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Posters day 2-3

Signatures of distorted geomagnetic field lines in Antarctic magnetometer data
Sean Ables

Authors

Ables S
The University of Newcastle

Sciffer M
The University of Newcastle

Waters C
The University of Newcastle

Inness E
Institution not provided

Fraser B
The University of Newcastle

Abstract

Ultra-low frequency (ULF) wave signatures in the magnetometer data from Davis, Antarctica (74.49° S, 100.03° E CGM) often exhibit spectral characteristics which can be interpreted as field line resonances (FLR) of the outermost closed field lines in the dayside magnetosphere. Diurnal variations in the frequency at which maximum power occurs in the Pc5 (1-10 MHz) band, often show an arch-shaped variation with local magnetic time. The general topology of the dayside high latitude magnetosphere results in longer field lines and therefore lower resonance frequencies on the dawn and dusk flanks, and the shortest field lines and higher resonant frequency for field lines near magnetic noon, passing through the sub-solar point. Similar FLR variations are seen in magnetometer data from the Mawson, Casey and Scott Base, Antarctica. We present an eigenfunction solution for shear Alfvén waves which also accounts for the curvature and torsion of the magnetic field that threads high latitude stations. This provides an explanation for our observations of a saddle in the Pc5 arch - a decrease in frequency centred on local magnetic noon - which is seen in Davis magnetometer data and to a lesser extent in Mawson, Casey and Scott Base data. Our modelling indicates that this saddle is due to increased field torsion on the dawn and dusk flanks producing increased pre- and post noon frequencies while the noon frequencies are depressed by field curvature.

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East Antarctic ice sheet thinning and retreat of the Ross Sea ice sheet
Jacob Anderson

Authors

Anderson, J.T.H.1, Wilson, G.S.1, 2, Lilly, K.1, Fink, D.3

  1. Department of Geology, University of Otago
  2. Department of Marine Science, University of Otago
  3. Institute for Environmental Research, Australian Nuclear Science and Technology Organisation

Abstract

Retreat of the East Antarctic Ice Sheet (EAIS) since the Last Glacial Maximum (LGM) has been associated with sea-level rise and ocean warming on the ice sheet margins, but this has been difficult to quantify. Understanding the timing of retreat is however, critical for identifying whether the EAIS made any significant contribution to eustatic sea-level rise since the LGM. This poster presents field evidence for EAIS thinning and Ross Sea Ice Sheet (RSIS) retreat. Using Escalade and Tate Peaks as mountain dipsticks, glacial deposits indicate the EAIS has thinned by more than 500 metres in the Skelton Névé during the late Cenozoic. The distribution of McMurdo Volcanic Group erratics on Brown Peninsula and Mount Discovery shows an expanded Koettlitz Glacier lobe enveloped much of Brown Peninsula and flowed northward and northeastward. Cenozoic fossiliferous rocks distributed on the northeastern flanks of Mount Discovery and on the northern coast of Minna Bluff, indicate that the Minna Bluff lobe of the RSIS flowed north and northwest to coalesce with the expanded Koettlitz Glacier lobe between Brown Peninsula and Black Island. 10Be and 26Al exposure ages from bedrock surfaces and erratics of Beacon Supergroup sandstones in the Skelton Névé will demonstrate whether meltwater contributions came from the EAIS, the Northern Hemisphere or both. Preliminary 10Be exposure ages from Eocene fossiliferous erratics from Southern McMurdo Sound imply the RSIS has responded to sea-level rise during the Holocene. Additional ages from granite and Eocene fossiliferous erratics will constrain the timing of retreat for the RSIS.

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Home-range overlap and site fidelity in the winter foraging movements of Antarctic fur seals
Benjamin Arthur

Authors

BT Arthur
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia

MA Hindell
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia

MN Bester
Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa

ME Goebel
NOAA South West Fisheries Science Centre, La Jolla, USA

ID Jonsen
Ocean Tracking Network, Department of Biology, Dalhousie University, Halifax, Canada

WC Oosthuizen
Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa

MD Sumner
Australian Antarctic Division, Channel Highway, Kingston, TAS 7050, Australia

PN Trathan
British Antarctic Survey, Cambridge, United Kingdom

M-A Lea
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia

Abstract

The Antarctic fur seal (Arctocephalus gazella) is a numerous and key Southern Ocean predator yet little is understood regarding foraging site fidelity in this species. During the non-breeding austral winter, female Antarctic fur seals undertake long-distance migrations, which were studied at three circum-polar breeding colonies (Marion Island, South Georgia and the Antarctic Peninsula) in 2008-2011. During the latter part of the lactation period in March/April of each year, animals were equipped with miniaturised geolocation tags (GLS) to track at-sea movements. Since 2008, winter tracks of ~8 months duration have been collected for 139 adult females. State-space modeling was employed to identify regions of area-restricted search behaviour, indicating areas of large-scale foraging activity. Kernel-based home range analyses were undertaken to identify home range size and overlap to quantify site fidelity. This was done at three scales: within trip, between successive trips across a year, and between years for animals tracked over multiple winters (n=6); a rare data set in marine biotelemetry studies. The long-term variability (10 plus years) of key environmental parameters including sea-surface temperature, sea-surface height, chlorophyll- a concentration, as well as bathymetric features, were assessed and compared between areas of high and low home-range overlap. There was a higher degree of home-range overlap between years (64 ± 16%) than within years (49 ± 15%), whilst overlap within trips was relatively low (24 ± 3%). Initial results suggest a range of winter foraging areas in female Antarctic fur seals and strong site fidelity both within and between years. Such strong foraging site fidelity has a number of ecological, evolutionary and conservation implications for competition, net long-term energy gain, niche specialization and the ability of individuals to respond to environmental change.

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Aeolian dust in Terra Nova Bay Polynya, Antarctica
Cliff Atkins

Authors

Cliff Atkins
School of Geography, Environment & Earth Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140

Gavin Dunbar
Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington 6140

Nick Golledge
Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington 6140 & GNS Science, PO Box 30 368, Lower Hutt 5040

Abstract

Aeolian dust is an important but poorly-constrained source of iron (Fe)-bearing sediment into the Ross Sea. Iron is an essential nutrient critical for triggering vast phytoplankton blooms each summer. These blooms are major productivity events, which influence an important biogeochemical cycle that draws-down atmospheric CO2, alters the oceanic food web and contributes biogenic sediment to the seafloor. Understanding these fundamental modern processes is essential for interpreting records of past environmental change in the region and predicting how they might change in a warming Antarctic and Southern Ocean. Terra Nova Bay (TNB) is an ideal location to examine the Fe-driven biogeochemical cycle because the interactions between dust, phytoplankton growth and nutrient supply from ocean upwelling thought to occur in the Ross Sea are found here. Strong katabatic airflow crosses the Transantarctic Mountains and Nansen Ice Shelf adjacent to the well-studied TNB polynya where intense phytoplankton blooms occur. We deployed custom built dust traps on the ice shelf and collected snow and firn samples to measure the flux of dust into the polynya. Initial results show that dust distribution and composition is strongly related to areas of exposed rock and the complex katabatic airflow. Aeolian sediment is concentrated into a ‘dusty corridor’ several km wide on the northern part of the ice shelf in the vicinity of ‘Hells Gate’, suggesting a concentrated point source for most of the Fe-bearing dust entering the polynya. Future work will focus on providing a greater spatial coverage of dust traps and numerical modelling to better quantify the flux. This will contribute to an improved understanding on the impact of dust on primary productivity and biogeochemical cycling in the region.

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Combining bio-logging and fatty acid signature analysis indicates spatio-temporal variation in the diet of the southern elephant seal, Mirounga leonina
Janaya Banks

Authors

Banks J
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania

Lea M
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania

McMahon C
Research Institute for the Environment and Livelihoods, Charles Darwin University

Hindell M
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania

Abstract

Quantifying the foraging ecology of apex predators is crucial for understanding and managing marine ecosystems. This is particularly important in the Southern Ocean ecosystem, as its vastness and heterogeneously distributed biological resources make year-round studies logistically impractical. Moreover, due to the wide-ranging nature of many southern hemisphere marine predators, detailed investigations into their diet need to be quantified spatio-temporally. We coupled tracking data with fatty acid signature analysis to investigate the foraging ecology of the southern elephant seal (Mirounga leonina). Seal foraging areas varied in space and time, but were concentrated in three broad geographic regions (i) off the East Antarctic Continental Shelf (S-ACC), (ii) at the edge of the pack ice north of the Ross Sea (SE-RS) and (iii) north of the Sub-Antarctic Front (SE-SAF). There were significant differences in the fatty acids (FA) in the blubber from the seals that used these different regions. Those in the SE-SAF were high in short chained mono-unsaturated fatty acids, compared to those from the S-ACC and SE-RS habitats, which contained more poly-unsaturated fatty acids. Comparisons with FAs of known prey species from the region indicated that blubber collected from seals using the shelf and pack-ice habitats were likely to have higher proportions of fish in the diet and, conversely, those from pelagic habitats were likely to have higher proportions of squid. Diet also varied annually, within the shelf and pack-ice habitats changing from a diet relatively high in fish, to a diet relatively high in squid. Coupling tracking data with FASA is a powerful technique to investigate the spatio-temporal variations in the diet of a wide-ranging marine predator, the southern elephant seal.

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Platelet ice attachment to instrument strings beneath the Amery Ice Shelf
Mike Craven

Authors

M. Craven
Australian Antarctic Division, Channel Highway, Kingston, Tasmania, 7050, Australia
and Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

R. C. Warner
Australian Antarctic Division, Channel Highway, Kingston, Tasmania, 7050, Australia
and Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

B. K. Galton-Fenzi
Australian Antarctic Division, Channel Highway, Kingston, Tasmania, 7050, Australia
and Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

L. Herraiz-Borreguerro
Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

S. W. Vogel
Australian Antarctic Division, Channel Highway, Kingston, Tasmania, 7050, Australia
and Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

I. Allison
Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

Abstract

Instruments suspended beneath the Amery Ice Shelf through hot water drilled boreholes record sporadic decreases in pressure of 10-20 decibars at sites where active growth of a marine ice layer occurs at the base of the shelf. These events are attributed to the buoyancy gained from accretion of platelet ice crystals to the moorings. Some events are transient, which we interpret as temporary achievement of buoyancy by the moorings before returning to pre-event pressures, probably due to mechanical dislodgement of loosely attached crystals. Driven by these pressure level changes temperatures recorded at the shallowest instruments (within 20 m of the shelf base) track in situ freezing point temperatures during these events. These results provide indirect evidence for the presence of frazil in the sub-ice shelf mixed layer and the active accretion of marine ice at the base of the Amery Ice Shelf. They also provide insight into the annual cycle of sub-ice ocean circulation confirming previous modelling results. The attachment of platelet ice to and vertical displacement of moorings has important ramifications for future project design and instrument deployment, as well as implications for the interpretation of oceanographic data from the sub-ice shelf environment.

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Live fast and die young; the cost of early breeding in southern elephant seals
Marine Desprez

Authors

Desprez M
Department of Environment and Geography, Macquarie University

Hindell M. A.
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania

Gimenez, O
Institution not provided

McMahon C
Research Institute for the Environment and Livelihoods, Charles Darwin University

Abstract

When to begin breeding is an important life-history decision that implies trade-offs, also known as the cost of reproduction, between present reproduction and future survival and reproduction. The cost of reproduction is important in shaping the life-history strategies of many species and can potentially strongly influence the fitness and the population viability. The youngest first-time breeders are expected to have lower subsequent survival and/or fecundity than individuals that delay their first reproduction to an older age. Consequently younger first-time breeders are likely to have lower lifetime reproductive success and/or to produce low-quality offspring. To quantify the effects of early breeding, we estimated the age-specific survival and the subsequent breeding probabilities of first-time breeders in a population of permanently marked southern elephant seals (Mirounga leonina) at Macquarie Island. We also investigated the relation between the maternal age at first reproduction and both the lifetime reproductive success and the offspring survival using multi-event capture-recapture models that account for both imperfect detection and uncertainty in the breeding status. Our results clearly supported the presence of a cost of early reproduction as the youngest first time breeders have a lower survival and breed less frequently than the females that delayed their first reproduction attempt.

Keywords: cost of reproduction, age at first reproduction, Mirounga leonina, multi-event capture-recapture model.

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Characterization of insoluble nanoparticles in ice cores from Law Dome, East Antarctica
Aja Ellis

Authors

Aja Ellis
Curtin University, Perth, GPO Box U1987, Perth WA 6845, Australia

Ross Edwards
Curtin University, Perth, GPO Box U1987, Perth WA 6845, Australia

Arie Van Riessen
Curtin University, Perth, GPO Box U1987, Perth WA 6845, Australia

Andrew Smith
Australian Nuclear Science and Technology Organisation (ANSTO), Sydney, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia

Mark Curran
Australian Antarctic Division (AAD), Kingston, Channel Highway, Kingston TAS 7050, Australia
Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC), Hobart, Private Bag 80, Hobart TAS 7001, Australia

Ian Goodwin
Macquarie University, Sydney, Balaclava Road, North Ryde, NSW 2109, Australia

Wang Feiteng
Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, 320 Donggang West Road, Lanzhou, 730000, China

Abstract

Insoluble nanoparticles, in the form of aerosols, have significant affects on climate and biogeochemical cycles. Records of these aerosols are essential for understanding paleoclimate forcing and future climate change. While a large body of research exists with respect to mineral dust particles (micron scale) derived from ice cores and sediment cores, very little is known with regards to the history of insoluble nanoparticles. These particles and their precursors are emitted to the atmosphere from a variety of primary and secondary sources including biomass burning, biogenic, anthropogenic, volcanic, and terrestrial mineral emissions. Ice core records are the only reliable way to study the past history of these particles. Here, we will present new data with regards to the physical and chemical properties of these particles as found in the Law Dome ice core, DSS0506 from East Antarctica.

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Light stimulated growth of proteorhodopsin bearing sea-ice psychrophile Psychroflexus torquis is salinity-dependent
Shi Feng

Authors

Shi Feng1, Shane M Powell1, Richard Wilson2 and John P Bowman1

  1. Food Safety Centre, School of Agriculture Science, Tasmanian Institute of Agriculture, University of Tasmania, Hobart, Tasmania, Australia
  2. Central Science Laboratory, University of Tasmania, Hobart, Tasmania, Australia

Abstract

Proteorhodopsins (PRs) are commonly found in marine prokaryotes and allow microbes to use light as an energy source. In recent studies it was reported that PR stimulates growth and survival under nutrient-limited conditions. In this study we tested the effect of nutrient and salinity stress on the extremely psychrophilic sea-ice bacterial species Psychroflexus torquis, which possesses PR. We demonstrated for the first time that light stimulated growth occurs under conditions of salinity stress rather than nutrient limitation and that elevated salinity is related to increased growth yields, PR levels and associated proton pumping activity. PR abundance in P. torquis also is post-transcriptionally regulated by both light and salinity and thus could represent an adaptation to its sea-ice habitat. Our findings extend the existing paradigm that light provides an energy source for marine prokaryotes under stress conditions other than nutrient limitation.

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Characterizing horizontal thermal and salinity structure in the wake of a floating glacier
Alexander L. Forrest

Authors

A.L. Forrest1, A. Hamilton2, C.L. Stevens3 and B.E. Laval2

  1. Australian Maritime College, University of Tasmania, Launceston, TAS, Australia
  2. Department of Civil Engineering, University of British Columbia, Vancouver, BC Canada
  3. Marine Physics, National Institute of Water and Atmospheric Research, Greta Point, Wellington, New Zealand

Abstract

Water column variability in the lee of the floating Erebus Glacier Tongue (EGT) was quantified using instrumented moorings, profilers and an Autonomous Underwater Vehicle (AUV). At the time of the work in 2011, the glacier extended 12 km into Southern McMurdo Sound, Antarctica. Vertical variability within the background tidal flows of ~0.3 m s-1 was quantified using a combination of CTD and time series of flow characteristics from acoustic Doppler current profilers (ADCPs). These instruments were deployed at 3 locations along the main AUV transect. Horizontal variability in temperature and conductivity was measured over ~500m transects using a Conductivity-Temperature-Depth profiler mounted on the AUV, enabling wavenumber energy spectra to be estimated at 10, 25 and 50 m depths through a range of tidal conditions. Analyses show highly energetic mixing in the near-surface layer (i.e., at the two shallow most depths run by the AUV) in the wake of the EGT. The spectral magnitude at high wavenumber increased with regional flow speed. In some cases a clear isotropic turbulence regime was apparent (k -5/3). The turbulence characteristics identified in the AUV transects were comparable with the moored data at similar depths run by the AUV during both spring and neap tides. These results suggest that floating ice tongues contribute to enhanced energy dissipation in the near-surface layer. Furthermore, there are a number of features in common with the calving face of ice-shelves so that the results here promote a greater understanding of ice-ocean interactions in general.

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Improved Antarctic surface mass balance remote sensing using ASCAT
Alexander D. Fraser

Authors

Alexander D. Fraser
Antarctic Climate & Ecosystems Cooperative Research Centre,
University of Tasmania, Private Bag 80, Hobart, Tasmania, 7001, Australia

Simon Wotherspoon
Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania 7001, Australia

Hiroyuki Enomoto
National Institute of Polar Research, 10-3 Midori-cho, Tachikawa-shi, Tokyo, 190-8518, Japan

Neal W. Young
Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia;
Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania, 7001, Australia

Abstract

Large scale distribution of Antarctic Surface Mass Balance (SMB) is currently poorly understood. High quality in situ measurements of SMB are sparse, particularly in the interior of the continent. Remote sensing can be used to guide interpolation between in situ measurements. Previously, passive microwave polarisation ratio, which is sensitive to the density of horizons of different dielectric properties in the upper snowpack (a proxy for SMB), has been used to guide interpolation of SMB points in Antarctica. We present evidence that maps of alternative parameters may be more suitable maps upon which to base interpolated fields. These maps come from the EUMETSAT Advanced Scatterometer (ASCAT) C-band scatterometer, which was launched in 2007. In particular, we use the "A" (isotropic component of backscatter, sensitive to grain size within the C-band penetration depth of ~ 20 m) and "B" (linear component of backscatter dependence on incidence angle, sensitive to grain size profile). Importantly, these maps are sensitive to recently-mapped extensive areas of surface wind glaze which are areas of near-zero net accumulation, and thus are less prone to overestimation of SMB compared with earlier large-scale SMB maps. A further focus of this work is a comparison of several statistical interpolation methods, including a careful consideration of the statistical treatment of negative SMB values. A primary output of this work is a new SMB map of the Antarctic continent based on these improved fields.

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Mercury cycling over the Southern Ocean during Polar Spring: Results from SIPEX II
Caitlin M. Gionfriddo

Authors

Caitlin M. Gionfriddo
School of Earth Sciences, University of Melbourne, Parkville, Australia

Michael Tate
Wisconsin Water Science Center, U.S. Geological Survey, Middleton, WI

David Krabbenhoft
Wisconsin Water Science Center, U.S. Geological Survey, Middleton, WI

Andrew Klekociuk
Australian Antarctic Division, Kingston, Australia

Klaus M. Meiners
Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Sandy Bay, Australia
Australian Antarctic Division, Kingston, Australia

Andrew Bowie
The Institute for Marine and Antarctic Studies, University of Tasmania, Sandy Bay, Australia
Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Sandy Bay, Australia

Delphine Lannuzel
The Institute for Marine and Antarctic Studies, University of Tasmania, Sandy Bay, Australia
Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Sandy Bay, Australia

Robyn Schofield
School of Earth Sciences, University of Melbourne, Parkville, Australia

John W. Moreau
School of Earth Sciences, University of Melbourne, Parkville, Australia

Abstract

Polar sea-ice plays a critical role in defining marine food webs. Despite of this, very little is known about the contribution of methylmercury (MeHg) from the sea-ice environment to resident aquatic organisms in the Southern Ocean. Sea-ice provides a unique ecological niche that may host microorganisms capable of methylating mercury (Hg). During the Sea Ice Physics Ecosystem eXperiment (SIPEX) II, snow, sea-ice, brine, and seawater samples were collected for total Hg (THg) and MeHg analysis to understand the speciation and distribution of Hg at the sea-ice/water interface. Real-time atmospheric elemental Hg concentrations were measured over the duration of the voyage, to identify Hg depletion events, which regularly occur in polar spring and result in Hg deposition in the snowpack. THg concentrations in snow, ice, and brine samples ranged from 0.20-179.1 ng/L, with a median value of 4.03 ng/L. MeHg concentrations ranged from 0.020-0.17 ng/L, median: 0.023 ng/L. The highest concentrations of MeHg and THg were found in ice core samples, but only ~0.7% was methylated. Seawater samples collected from depths of 15-1000 m had the lowest THg concentrations (0.22-2.48 ng/L, median: 0.47 ng/L), but higher methylation proportionally (11% MeHg). Thus, MeHg concentrations in the seawater profile were similar to ice core samples (median: 0.035 ng/L). In the snowpack, the highest concentrations of THg were found in the upper 2 cm, and decreased with depth, indicating Hg deposition, but loss over time. Our results provide useful constraints on fluxes and bioavailability for mercury across the atmosphere-sea-ice-seawater continuum for the under-sampled Antarctic region.

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Oceanic heat flux, on-shelf flow and basal melting of the Totten Glacier, East Antarctica
David E. Gwyther

Authors

David E. Gwyther
Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania 7001, Australia
Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001

Ben Galton-Fenzi
Australian Antarctic Division, Hobart, Tasmania, Australia
Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001

John Hunter
Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001
Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania 7001, Australia

Jason Roberts
Australian Antarctic Division, Hobart, Tasmania, Australia
Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001

Abstract

The Totten glacier and ice stream drains a large proportion of the Antarctic Ice Sheet, much of it grounded below sea level and susceptible to rapid mass loss. Increased basal melting reduces the buttressing effect of the ice shelf, leading to accelerated glacial flow and thinning. The state of the grounded ice sheet is therefore susceptible to changes in ocean heat flux and circulation. The Totten glacier has recently been observed to be thinning (at 1.9 m/yr). It is believed that the change exhibited by the Totten glacier is from changes in oceanic forcing - but the details, extent and magnitude of the interaction is unknown. Here we present a model, based on the Regional Ocean Modelling System, that has been developed to simulate the interaction between the Totten ice shelf and the ocean, with the aim of pinpointing causal factors of basal melting. Publicly available bathymetry and ice thickness datasets provide the geometry while the model is forced by currents, tides, buoyancy fluxes and wind on the surface and lateral boundaries. Analysis of model output shows basal melt rates in agreement with glaciological estimates. Ocean currents simulated by the model supply significant heat across the continental shelf break and into the topographic basin in front of the ice shelf. Therefore this study links basal melt of the Totten ice shelf to ocean heat transport. This is the first such modelling study of this region, and will provide valuable information for directing future observational missions.

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Energetic variability in toothed whales and relationships with a changing marine environment
Vicki Hamilton

Authors

Vicki Hamilton1, Karen Evans1,2 and Mark Hindell1

  1. Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania 7001, Australia
  2. CSIRO Marine and Atmospheric Research, GPO Box 1538, Hobart, Tasmania 7001, Australia

Abstract

Information on the biology of many marine mammal species in the Southern Hemisphere is sparse. The importance of addressing and identifying environmental change issues, such as the impacts of a changing climate on the distribution of species and prey resources, and the capacity for adaptation by marine mammals is recognised. To this end, there is a need for long-term cetacean environmental datasets for use in modelling studies for identifying interactions between management advice and the effects of variability in the marine environment. Here we describe a project that aims to provide insights into aspects of the responses of marine mammal species to climate mediated variation in the marine environment, and how these responses might vary into the future under changing climatic conditions. Using marine mammal teeth as multi-decadal archives of ecological information, relationships between variability in the marine environment and tooth growth, as an indicator of energy available for growth, and isotopic composition, as a reconstruction of past diet in marine mammals will be examined. Initially focusing on three pelagic cetacean species: the sperm whale (Physeter macrocephalus), the long-finned pilot whale (Globicephala melas) and the short-finned pilot whale (Globicephala macrorhynchus), this project will incorporate investigations of both taxonomic and geographic variability regionally across Australia and more broadly across the Southern Hemisphere. Statistical models developed will be used to investigate how future projections of oceanic conditions may influence energetic intake in each species and the potential for adaptation of these species under changing environmental conditions.

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Using animal telemetry data to identify areas of ecological significance in the Southern Ocean
Robert Harcourt

Authors

R Harcourt
Graduate School of Environment, Macquarie University

C Guinet
Centre National de la Recherche Scientifique

S Bestley
Australian Antarctic Division

J Charrassin
Muséum National d'Histoire Naturelle

SD Goldsworthy
Marine Environment and Ecology, SAARDI Aquatic Sciences

M Lea
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia

CR McMahon
Research Institute for the Environment and Livelihoods, Charles Darwin University

MA Hindell
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia

Abstract

Far from homogeneous, the Southern Ocean is a complex mix of frontal regions, eddies, currents, and a dynamic sea-ice zone, all of which can act to concentrate nutrients and productivity in some areas and dissipate them in others. Establishing the physical and biological determinants of ecologically important areas is a core question in marine ecology, but our ability to do this is hampered by a lack of data collected at the appropriate spatial and temporal scales. However, animal tracking data can provide valuable insights. Predators focus their foraging efforts in regions that enable them to meet their energetic needs in the context of current and future requirements. Individual animal-borne CTD-SRDLs afford us the capacity to record physical attributes of areas of ecological importance to animals and interpret the effects structure and variability at-sea have on individual life history traits such as growth, reproduction and survival. The Integrated Marine Observing System (IMOS) and the French polar program is supporting tracking of several species in the Southern Ocean using CTD tags, which has so far provided more than 65,000 CTD profiles in the Southern Indian Ocean from 7 consecutive years (2007-2013) between Iles Kergeulen and Prydz Bay enabling a comprehensive spatial and temporal description of the ocean habitats used by the animals. Coupled with the movement and diving behaviour of the seals, these data identify modified shelf water and upper circumpolar deep water as important habitats. This information can be used to predict how seal foraging locations change with respect to changing Southern Ocean conditions.

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Fine scale 3 dimensional dive behaviour of Antarctic fur seals along the Kerguelen Plateau
Nicole Hellessey

Authors

Nicole Hellessey
Institute for Marine and Antarctic Studies (IMAS), Cnr Grosvenor and Alexander Streets, Hobart

Dr Mary-Anne Lea
Institute for Marine and Antarctic Studies (IMAS), Cnr Grosvenor and Alexander Streets, Hobart

Abstract

Antarctic fur seals (Arctocephalus gazella) are one of the more well studied circumpolar marine predators. In the Kerguelen Plateau region in particular, much is known regarding their diet preferences for myctophids and squid, variability in foraging regions and diving behaviour and even route tactics associated with the Polar Front. Little, however, is currently known concerning the three dimensional habitat use of female Antarctic fur seals in relation to oceanographic features such as thermoclines. Knowledge of how predators (and their prey) respond at fine-scales to variability in the water column is important for understanding temporal shifts in predator-prey dynamics. This study assesses the validity of using water column temperature data measured by Mk7 time depth recorders deployed on female Antarctic fur seals in 1999 and 2000 at Cap Noir, Iles Kerguelen. A total of 66 foraging trips were recorded over the two austral summers. Preliminary results suggest that females may dive within distinct temperature bands that vary between years.

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Glacial history of Mackay Glacier, Transantarctic Mountains Chronology of thinning to the present day
Richard S. Jones

Authors

Richard Selwyn Jones
Victoria University of Wellington, Kelburn, Wellington, New Zealand

Andrew Mackintosh
Victoria University of Wellington, Kelburn, Wellington, New Zealand

Kevin Norton
Victoria University of Wellington, Kelburn, Wellington, New Zealand

Nicholas Golledge
GNS Science, Avalon, Lower Hutt, New Zealand
Victoria University of Wellington, Kelburn, Wellington, New Zealand

Abstract

Configuration of the Antarctic ice sheets is inherently linked to changes in climate and the encircling Southern Ocean. Quantifying the changes that occurred in the ice sheet since the Last Glacial Maximum (LGM) is therefore vital for understanding the overall ice sheet sensitivity and long-term drivers of ice sheet changes. Mackay Glacier drains the East Antarctic Ice Sheet through the Transantarctic Mountains into the Ross Sea, and is therefore well placed to record the sensitivity of outlet glaciers to regional atmospheric warming, sea level rise or increased ocean temperatures.

We present recent fieldwork at Mackay Glacier which aims to firstly better constrain the thickness of the Antarctic Ice Sheet in this region of the Transantarctic Mountains at the LGM, and secondly to understand the way in which it subsequently thinned and retreated to its present configuration. Geomorphological mapping aided sample collection for terrestrial cosmogenic nuclide dating. Samples were collected in a series of elevation transects at several locations down the longitudinal profile of the glacier to record deglacial thinning. The resultant chronology will include mostly 10Be dates but will also require multiple isotope analysis. It will subsequently constrain a glaciological flowline model that will investigate the dynamics of outlet glaciers during deglaciation.

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The Antarctic Blue Whale Project
Natalie Kelly

Authors

Kelly N
CSIRO Mathematics, Informatics and Statistics and Wealth from Oceans Flagship, Australian Marine Mammal Centre

Double M
Australian Marine Mammal Centre, Australian Antarctic Division

Wadley V
Australian Marine Mammal Centre, Australian Antarctic Division

Miller B
Australian Marine Mammal Centre, Australian Antarctic Division

Peel D
CSIRO Mathematics, Informatics and Statistics and Wealth from Oceans Flagship, Australian Marine Mammal Centre

Andrews-Goff V
Australian Marine Mammal Centre, Australian Antarctic Division

Bell E
Australian Marine Mammal Centre, Australian Antarctic Division

Abstract

During the twentieth century some 330,000 Antarctic blue whales were taken by commercial whaling; the species was close to extinction when hunting was banned in the 1960s. Subsequent abundance estimates derived from line transect surveys over the past thirty years suggest that while the population is probably increasing, it still remains less than 5% of pre-exploitation abundance. Following cessation of circumpolar-level sighting surveys in 2004 there was no strategy to obtain further abundance estimates for Antarctic blue whales to judge their recovery, but a renewed effort will be conducted as part of the multi-national, circumpolar Southern Ocean Research Partnership (SORP). With low encounter rates, line transect methods are not likely to yield estimates of abundance with reasonable precision given the expected availability of dedicated research vessels. We therefore propose a mark-recapture approach, using both photo-ID and genetics, for estimating a new circumpolar abundance of Antarctic blue whales. These data may also prove valuable in studying population structure and individual movements within the Southern Ocean and beyond. We anticipate substantial improvements on historical encounter rates by targeting higher-density regions and by using passive-acoustics. Such improvement was confirmed during a voyage west of the Ross Sea in Jan-Mar 2013, which successfully found nearly 50 blue whales. The potential to place satellite-tags on blue whales was also demonstrated during this voyage. Under the Antarctic Blue Whale Project we plan build a legacy of data, and develop powerful and robust methods, to aid understanding of the recovery of the species over the coming decades.

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SIPEX II: Wave propagation in an Antarctic marginal ice zone
Alison L. Kohout

Authors

Dr Alison L Kohout
NIWA, Christchurch, NZ

Dr Mike Williams
NIWA, Wellington, NZ

Dr Jan Lieser
ACE CRC, Hobart, Australia

Dr Takenobu Toyota
Hokkaido University, Hokkaido, Japan

Abstract

Antarctic sea-ice is highly influenced by the dynamic nature of the Southern Ocean. Ocean waves can propagate from tens to hundreds of kilometres into sea-ice, leaving behind a wake of broken ice sheets. As global climate change intensifies, storm intensity will increase in the Southern Ocean. Increased storm intensity will bring stronger winds and bigger waves, which have the potential to travel deeper into the ice pack and increase the likelihood that ice floes break apart. To enhance our understanding of this system, our aim during the Sea Ice, Physics and Ecosystems eXperiment (SIPEXII) was to build on the scarce Antarctic waves-in-ice dataset by collecting a set of wave observations in the marginal ice zone. Five wave sensors were deployed on Antarctic sea-ice. They were spread along a 200 km north – south transect line on 121 E. Every three hours, the sensors simultaneously woke and recorded their location and a burst of wave acceleration data. The results from the voyage will be presented.

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Role of Antarctic sea ice as a natural ocean fertilizer during the spring 2012-13 sea ice research voyage SIPEX-2
Delphine Lannuzel

Authors

Lannuzel D
Institute for Marine and Antarctic Studies

van der Merwe P
Antarctic Climate and Ecosystems CRC

Chever F
Antarctic Climate and Ecosystems CRC

Janssens J
Institute for Marine and Antarctic Studies

Cavagna A
Vrije Universiteit Brussel

Roukaerts A
Vrije Universiteit Brussel

Abstract

One of the most important advances in oceanography was the discovery that iron can limit the productivity of High Nutrient Low Chlorophyll areas like the Southern Ocean where iron input to the sunlit layer of the ocean is low. In order to elucidate the ocean carbon cycle in the past, present and future climate scenarios, iron biogeochemistry became a focal point in our understanding of the processes that regulate the delivery and retention of this key micro-nutrient in surface waters. It has been demonstrated that Antarctic sea ice acts as an annual fertilizer of iron in the Southern Ocean at a time ideal for algal growth, therefore producing large blooms observable every austral spring from SeaWIFS pictures. Our study quantified the spatial and temporal distribution of iron in sea ice cores, surface snow, brine and underlying seawater collected during an interdisciplinary Australian Antarctic fieldwork in East Antarctic pack ice in 2012 (SIPEX-2). Additional processing in the home laboratory was achieved on ice cores to obtain for the first time the size fractionation of iron in the soluble (< 0.02 µm), dissolved (< 0.2 µm) and particulate (> 0.2 µm) fractions. Complementary samples were collected for the determination of sea ice salinity and temperature, sea ice texture, macro-nutrients, dissolved and particulate organic carbon, chlorophyll a as well as other key trace elements in first-year (seasonal) sea ice. Preliminary results are presented and discussed in this session.

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You snooze, you lose: adaptive sleep loss in polygynous pectoral sandpipers
John A. Lesku

Authors

John A. Lesku
La Trobe University, Melbourne, Australia

Niels C. Rattenborg
Max Planck Institute for Ornithology, Seewiesen, Germany

Mihai Valcu
Max Planck Institute for Ornithology, Seewiesen, Germany

Alexei L. Vyssotski
University of Zurich / ETH Zurich, Zurich, Switzerland

Sylvia Kuhn
Max Planck Institute for Ornithology, Seewiesen, Germany

Franz Kuemmeth
e-obs Digital Telemetry, Munich, Germany

Wolfgang Heidrich
e-obs Digital Telemetry, Munich, Germany

Bart Kempenaers
Max Planck Institute for Ornithology, Seewiesen, Germany

Abstract

Sleep performs restorative processes that sustain waking brain function. However, we recently provided the first direct evidence that sleep loss can be adaptive. Pectoral sandpipers (Calidris melanotos) migrate annually to above the Arctic Circle to breed in the summer under continuous daylight. Males are polygynous and engage in intense male-male competition for access to fertile females during a 3-week period. In a multi-year study, we measured (i) activity levels in males, (ii) electroencephalogram (EEG) activity in free-roaming males on the tundra to determine whether inactive males were sleeping or simply sitting quietly awake, (iii) the number of male-female interactions, and (iv) the parentage of virtually all chicks on the study site. Overall, activity levels varied considerably across males, and some males were active >95% of the time for a period lasting up to 19 d. Birds rapidly transitioned from active wakefulness to sleep, such that activity is a good proxy for wakefulness in these animals. Not only did some males sleep very little, but the sleep obtained was heavily fragmented into hundreds of short micronaps. Most importantly, males that slept the least interacted with more females and sired the most offspring. Thus, males that slept less performed better on the most important measure of performance from an evolutionary perspective. These results provide the first evidence that reduced performance is not an evolutionarily inescapable outcome of sleep loss.

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Aerial imaging of sea ice with LiDAR and photos
Jan L. Lieser

Authors

Jan L Lieser
Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Private Bag 80, 7001, Hobart, Tasmania, Australia

Abstract

An integrated airborne imaging system with scanning LiDAR (Light Detecting And Ranging) and high resolution, digital aerial photography is used by the Australian Antarctic Program for various purposes, in East Antarctica. One of the main objectives is the measurement of surface elevation of sea ice (ice freeboard) and glacial ice to estimate its thickness. To understand the effects and feedbacks of a changing climate in polar regions information on the rate of change of ice thickness is vital. Large-scale coverage of the East Antarctic ice sheet, ice shelves, and the sea ice zone is currently very sparse, with latterly relying on satellite altimetry measurements that are unvalidated and uncalibrated.

We describe the combined instrument system and present in-situ results acquired over sea ice in the vicinity of 122° East, 65° South. Validation of the airborne surface elevation data is done by drill-hole measurements of sea ice freeboard and shows agreement to within the centimetre-level. This allows confidence to use the system for large-scale aerial surveys (up to 200 km range) to calibrate and validate space-borne sea ice thickness products, for example from CryoSat-2.

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An airborne snow-thickness RADAR for marine glaciology application
Jan L. Lieser

Authors

Jan L Lieser
Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Private Bag 80, 7001, Hobart, Tasmania, Australia

Peter W Jansen
Integrated Marine Observing System, University of Tasmania, Hobart, Private Bag 110, 7001, Hobart, Tasmania, Australia

Abstract

Snow on sea ice has a profound influence on the albedo of the ice covered ocean and the heat flux between ocean and atmosphere in the sea ice zone. Knowledge of the thickness of the snow cover on sea ice is also essential to compute sea ice thickness from altimeter data. Precise measurements of both, snow and sea ice thickness will allow for an assessment of the performance of numerical models of the physical polar environment. To estimate the thickness of the snow cover on sea ice over sufficiently large areas (tens of kilometres) space-borne instrumentation is required, for example the radar altimeter of CryoSat-2, or the Advanced Microwave Scanning Radiometer AMSR-2. In-situ measurements of snow properties are essential to enable adequate calibration and validation of these satellite data products.

We present an airborne snow thickness RADAR deployed by the Australian Antarctic program in the East Antarctic sea ice zone. This instrument is used to bridge the gap between highly detailed/small scale (space and time) measurements of snow properties, including surface elevation (freeboard), and broad scale/resolution space-borne estimates. These will be used to improve the ice and snow thickness products from satellite laser and radar altimetry, which provide the necessary global coverage for monitoring large-scale change.

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Impact of external factors on changing dynamics of Mertz Glacier Tongue prior to 2010 calving
Robert A. Massom

Authors

Robert A. Massom
Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7053, Australia
and Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

A. Barry Giles
Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

Roland C Warner
Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7053, Australia
and Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

Benoit Legrésy
LEGOS (CNRS-CNES-UPS-IRD), Av. E. Belin, 31400 Toulouse, France

Helen A. Fricker
Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093-0225, USA

Glenn Hyland
Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7053, Australia
and Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

Lydie Lescarmontier
LEGOS (CNRS-CNES-UPS-IRD), Av. E. Belin, 31400 Toulouse, France.
Now at: Research School of Earth Sciences, Australian National University, Building 142 Mills Road, Acton, ACT 0200, Australia

Neal Young
Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

Abstract

Iceberg calving accounts for about half the mass lost from Antarctica, yet our current understanding of the process is inadequate. The Mertz Glacier tongue (MGT) in East Antarctica experienced a large calving event in 2010, producing iceberg C28. Satellite observations over the preceding decade provide an opportunity to analyse the behaviour of the MGT prior to the calving. Major and occasionally abrupt changes in flow dynamics occurred in response to several “external” factors. These factors include apparent contact of the northwestern tip of the MGT with the seabed beginning in 2002, which caused the MGT flow direction to rotate rapidly by approximately 46° eastwards. This was immediately followed by a rapid opening of the western part of a major transverse rift ~70 km to the south; which became the C28 calving front. A more localized external factor was an abrupt collision of vast iceberg C08 (calved from the Ninnis Glacier tongue in 1980-82) with the northeastern flank of the MGT. This temporarily knocked the northern portion of the MGT a few hundred metres to the west before it “rebounded” to approximately its original flow direction. Finally, a small iceberg, grounding near the northwestern tip of the MGT, “chiselled” off numerous small icebergs as the tongue advanced, removing 36.4 km2 of ice over five-years. We propose that detailed understanding of case-specific external factors may be critical to understanding how glacier tongues calve, and this might considerably complicate modeling efforts to predict the ice sheet contribution to sea level change.

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Cone Penetration Testing (CPT) in polar snow
Adrian McCallum

Authors

Adrian McCallum
University of the Sunshine Coast, Queensland, Australia

Abstract

Penetrative testing is the best means of assessing snow strength in situ. However, existing snow penetrative equipment is unable to penetrate to substantial depth, at a constant rate, in hard polar firn. Therefore, existing Cone Penetration Testing (CPT) equipment, typically used in soils, was modified to allow efficient testing in snow. CPT equipment was mounted on the back of a tractor, and was hydraulically powered, enabling rapid testing to depths of 10 m, in polar firn as hard as 10 MPa, recording data including cone tip resistance and sleeve friction. Analysis of results suggests that three main determinants of snow’s physical behaviour, its strength, density, and microstructure, can potentially all be obtained via this one test: the CPT.

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Dietary analysis of Weddell seals (Leptonychotes weddellii) as concluded from scat collection in McMurdo Sound, Antarctica
Jessie McEldowney

Authors

Jessie McEldowney
University of Tasmania, University of Canterbury

Abstract

Weddell seals (Leptonychotes weddellii) in McMurdo Sound have a long history of dietary analyses, with understanding their feeding ecology essential to determining ecological role, trophic links, and prey consumption in the Ross Sea. Twenty-one faecal samples collected in summer 2009 revealed a diet primarily dominated by fish – the tentatively identified nototheniid Pleuragramma antarcticum in particular – with over 83% of samples exhibiting some evidence of piscines. Despite this, often a large percentage of samples will not contain identifiable otoliths, and as such no direct confirmation for the believed major prey item Antarctic toothfish (Dissostichus mawsonii) consumption was exhibited, especially with the tendency for Weddell seals to avoid eating the head, skin, and vertebral column. The excessive presence of plankton (in 100% of samples) has led to supporting the proposal of secondary ingestion, and similar theories have been applied to the occurrence of rocks and stones (in over 16% of samples). With all this uncertainty, the future of dietary analysis in Weddell seals is moving away from taxonomic identification of faecal hard parts, and more towards molecular methods such as DNA and stable isotope analysis, as combined methods tend to have a greater success rate than singular identification techniques.

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Holocene climate history for coastal East Antarctica: The isotopic record from the Law Dome deep ice core
Andrew Moy

Authors

Moy, A.D.1,2, van Ommen, T.D.1,2, Morgan, V.1,2, Plummer, C.2,3, and Curran, M.A.J.1,2

  1. Australian Antarctic Division, Kingston, Australia
  2. Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Australia
  3. Institute for Marine and Antarctic Science, University of Tasmania, Hobart, Australia

Abstract

Contiguous high-resolution oxygen isotope (d18O) measurements have been made along the entire length of the Dome Summit South (DSS) ice core from Law Dome (LD), Antarctica. This high-resolution d18O record provides a climate history for coastal East Antarctica spanning the last 90ky. We present here the Holocene part of the record – 10ky BP to the present. LD d18O during the Holocene is marked by a pronounced ‘warm’ peak at ca. 9.7ky followed by cooling. The subsequent cooling ends at ca. 7.5ky and is followed by a period of minimal isotope trend between ca. 7.5ky and ca. 3.6ky. The late Holocene shows a slow cooling trend from ca. 3.6ky to 1ky at which time there is a cooling event of some 0.5 permil. The recent 1ky is the isotopically ‘coolest’ period in the Holocene. The accumulated cooling since ca. 8ky is ca. 1 permil, amounting to ca. 2-3 degrees Celsius based on T/d18O calibrations derived by comparing interannual variations with meteorological records. This calibration value is substantially different to the value of ca 0.7 permil per deg C obtained from spatially distributed values for mean annual d18O and mean annual temperature. The cooling in the late Holocene part of the LD record differs significantly from records obtained from inland sites and other coastal sites. It is possible that a part or all of the isotope ratio change is a result of change in the elevation of the Dome but there is no convincing evidence of this.

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The velocity of the primary tributary glaciers of the Amery Ice Shelf, 2004-2012
Mark L. Pittard

Authors

Mark L. Pittard
Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania 7001
Antarctic Climate & Ecosystems Cooperative Research Centre, Private Bag 80, Hobart Tasmania 7001

Jason L. Roberts
Department of Sustainability, Environment, Water, Population and Communities, Australian Antarctic Division, Hobart, Tasmania, Australia
Antarctic Climate & Ecosystems Cooperative Research Centre, Private Bag 80, Hobart Tasmania 7001

Ben K. Galton-Fenzi
Department of Sustainability, Environment, Water, Population and Communities, Australian Antarctic Division, Hobart, Tasmania, Australia
Antarctic Climate & Ecosystems Cooperative Research Centre, Private Bag 80, Hobart Tasmania 7001

Christopher S. Watson
School of Geography and Environmental Studies, University of Tasmania, Private Bag 76, Hobart, Tasmania 7001

Roland C. Warner
Department of Sustainability, Environment, Water, Population and Communities, Australian Antarctic Division, Hobart, Tasmania, Australia
Antarctic Climate & Ecosystems Cooperative Research Centre, Private Bag 80, Hobart Tasmania 7001

Abstract

Observations have shown that tributary glaciers can accelerate rapidly following changes in their bordering ice shelves. Monitoring these changes in the rate of ice flow into the ice shelf is vital to understand how, where and when changes are occurring in Antarctica and hence subsequently their possible impact on sea level rise. The Amery Ice Shelf (AIS) is the largest embayed ice shelf within the East Antarctic Ice Sheet. The observations of velocity change on the AIS are between 1968-1999, with a focus on the floating ice with very limited observations on the tributary glaciers. This study uses the surface feature tracking software IMCORR to measure the displacement of features on the ice surface between a sequence of visible spectrum Landsat 7 images spanning 2004 to 2012, focussing on the region bordering the Amery Ice Shelf's grounding line, and its tributary glaciers the Fisher, Mellor and Lambert Glaciers. No significant changes in velocity are observed over this period which supports the Mass-Balance and Altimetry observations that support the hypothesis of no change and relative stability in this region. Using the calculated spatially incomplete velocity fields for each year set between 2004 and 2012, a composite map of velocities is developed. The computed velocity field estimates lower velocities than comparable datasets in the literature, especially evident in the Lambert Glacier, but is consistent with the limited in situ velocity measurements derived from GPS in the region.

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The Holocene sea-salt trace ion chemistry record from Law Dome, East Antarctica
Christopher T. Plummer

Authors

Christopher T. Plummer1,2, Mark A.J. Curran2,3, Tas D. van Ommen2,3, Tessa .R. Vance2, Andrew D. Moy2,3, Vin I. Morgan2, Paul A. Mayewski4

  1. Institute for Marine and Antarctic Science, University of Tasmania, Hobart, Tasmania, Australia
  2. Antarctic Climate and Ecosystems Cooperative Research Centre, Hobart, Tasmania, Australia
  3. Australian Antarctic Division, Kingston, Tasmania, Australia
  4. Climate Change Institute, University of Maine, Orono, USA

Abstract

Trace ion chemistry records from ice cores provide a valuable archive of past climate, with snow preserving atmospheric conditions during deposition. Trace ion analysis has been performed on ice from the Law Dome, Dome Summit South (DSS) ice core site in East Antarctica, covering the 12ky BP Holocene epoch. The data have a resolution from sub-annual over the last 2300 years, to 30 years at 12ky BP, and provide a well-resolved Holocene chemistry record. The sea-salt species of Cl- and Na+ are useful indicators of variation in atmospheric circulation patterns, with links recognized previously between sea-salt concentrations and regional wind strength, Southern Annular Mode (SAM) and El Niño–Southern Oscillation (ENSO). Here we present initial findings from analysis of DSS Cl- and Na+ records and examine their variability through the Holocene. Comparisons with other Holocene sea-salt records from the East Antarctic sector (TALOS dome and EDC ice cores) are used to explore regional-scale variability.

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Volcanic signals in ice core records from Law Dome, East Antarctica
Samuel Poynter

Authors

Poynter S
Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia

Curran M
Australian Antarctic Division, Kingston, and Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia

Plummer C
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia

Moy A
Australian Antarctic Division, Kingston, and Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia

van Ommen T
Australian Antarctic Division, Kingston, and Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia

Roberts J
Australian Antarctic Division, Kingston, and Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia

McConnell J
Division of Hydrologic Sciences, Desert Research Institute, Nevada, USA

Etheridge D
CSIRO Marine and Atmospheric Research, Aspendale, Victoria, Australia

Abstract

Volcanic forcing is a major influence on our climate, and ice cores provide the best record of the timing and strength of volcanic eruptions. Our understanding of volcanic sulfate deposition is very important and is generally attributed to the physical characteristics of the site, climatic circulation patterns and depositional mechanisms. However, localised variation in volcanic sulfate deposition is not widely understood, arguably due to the small number of ice core records originating from clustered sites.

The Dome Summit South (DSS) ice core from Law Dome holds one of the most accurately dated volcanic records from Antarctica. This location is characterised by a high snow accumulation rate, with a decrease in accumulation observed in a westerly direction across Law Dome. A second, independently-layer counted record (W10k) has been recently generated from a site 10 km west of DSS, and covers a period of 270 years up to 2009 CE.

Presented here is a comparison of volcanic sulfate records from four sites, namely DE08, DSS, W10k and W19k (in order of accumulation) lying in an approximate 40 km East-West transect across Law Dome. Nine major low-latitude volcanic events are preserved in these records, of which the largest are the 1815 CE Tambora eruption and the 1809 CE eruption at an unidentified location.

While the absolute concentration of volcanic sulfate is in agreement between the sites for the 8 smallest events, the concentration during the Tambora event displays an inverse relationship with respect to the accumulation rate. It is envisaged that by using this data to generate an uncertainty estimation of volcanic sulfate deposition, this study will improve the accuracy and further strengthen volcanic forcing in climate models.

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HEM bird measurements of ice thickness and freeboard over the McMurdo Sound and implications for ice density
Wolfgang Rack

Authors

W. Rack1, C. Haas2 and P. Langhorne3

  1. Gateway Antarctica, University of Canterbury, Christchurch, NZ
  2. Department for Earth and Space Science, York University, Toronto, CAN
  3. Department of Physics, University of Otago, Dunedin, NZ

Abstract

We present airborne measurements to investigate the thickness, freeboard, and density of sea ice and ice shelf in McMurdo Sound in the western Ross Sea. In November 2009 and 2011 we used a helicopter-borne laser and electromagnetic induction sounder (HEM bird) to measure thickness and freeboard profiles across the ice shelf and the sea ice. In both years, airborne data were validated with field measurements for ice thickness, snow depth and density, and thickness of the sub-ice platelet layer. The quality of the helicopter measurements was analysed at cross-over points, yielding an accuracy of about 10% for both thickness and freeboard over sea ice and ice shelf. It was found that the EM sounder systematically overestimates the ice thickness in the presence of a sub-ice platelet layer, which is observed in areas of outflow of super-cooled ice shelf water. This offers the opportunity to use the HEM bird for mapping the sub-ice platelet layer by airborne remote sensing. Using freeboard and thickness, the bulk density was calculated assuming hydrostatic equilibrium. Significant density steps were detected between first-year and multiyear sea ice, with higher values for the younger sea ice. On the ice shelf, bulk ice densities were sometimes higher than that of pure ice, which can be partly explained by the accretion of marine ice and glacial sediments. The thickness and density distribution reflects a picture of areas of basal freezing and supercooled Ice Shelf Water emerging from below the central ice shelf cavity into the McMurdo Sound.

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Inferring ice-flow directions from single ice-sheet surface images using the Radon transform
Jason L. Roberts

Authors

Jason L Roberts
Australian Antarctic Division, Channel Highway, Kingston, Tasmania, 7050, Australia
and Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

Roland C Warner
Australian Antarctic Division, Channel Highway, Kingston, Tasmania, 7050, Australia
and Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

Adam Treverrow
Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

Abstract

We present a new method for extracting the direction of surface flow for ice sheets, based on the detection of flow-induced features that are visible in satellite imagery. The orientation of linear features is determined using a Radon transform and only requires a single image. The technique is demonstrated by applying it to the RADARSAT mosaic of Antarctica, over the Lambert Glacier–Amery Ice Shelf region of East Antarctica. Comparisons with both existing flow-direction fields and traced streamlines over the same area provide an evaluation of the method. We also illustrate its application to Landsat 7 imagery.

Knowledge of the direction of ice flow in glaciers and ice sheets is useful in a variety of applications. These include defining drainage regions and delineating flowbands in mass-balance and modelling studies, reconstructing complete surface velocities from satellite interferometric synthetic aperture radar (InSAR) measurements and making along-flow interpolations.

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Atmospheric chemistry measurements of bromine explosion/mercury deposition during the Polar Spring SIPEX II, 2012 Campaign
Robyn Schofield

Authors

Robyn Schofield1, Ruhi Humphries2, Caitlin Gionfriddo1, Karin Kreher3*, Paul Johnston3, Neil Harris4, Andrew Robinson4, Michael Tate5, David Krabbenhoft5, John W. Moreau1, Suzie Molloy6, Ian Galbally6, Melita Keywood6, Stephen Wilson2, Simon Alexander7, Andrew Klekociuk7, Andrew Bowie8,9, Delphine Lannuzel8,9 and Klaus Meiners8

  1. School of Earth Sciences, University of Melbourne, VIC 3010, Australia
  2. Centre for Atmospheric Chemistry, University of Wollongong, NSW 2522, Australia
  3. National Institute of Water and Atmospheric Research, Lauder, New Zealand
  4. Centre for Atmospheric Science, Department of Chemistry, Cambridge CB2 1EW, England
  5. US Geological Survey, Middleton, WI53562, United States
  6. Centre for Australian Weather and Climate Research, CSIRO Marine and Atmospheric Research, VIC 3195, Australia
  7. Australian Antarctic Division, TAS 7050, Australia
  8. Antarctic Climate and Ecosystems, Cooperative Research Centre, Hobart, TAS 7001, Australia
  9. Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS 7001, Australia

*Now at Bodeker Scientific, Alexandra, New Zealand

Abstract

Bromine explosion events that occur over first year sea ice in the polar spring cause mercury deposition and dramatically alter the oxidative capacity of the polar boundary layer. Atmospheric chemical measurements made during the Sea Ice Physics and Ecosystems eXperiment (SIPEX II) in the polar spring of 2012 are presented here. Vertical BrO, NO2, HCHO profile concentrations were made with a UV-Vis Multi-AXis Differential Optical Absorption Spectrometer (MAX-DOAS). Halocarbon (i.e. CH2CH2, CHBr3) observations were made using a GC-ECD µ-Dirac and gaseous elemental mercury (GEM) observations made using a Tekran instrument along with in-situ ozone and aerosol new particle observations. In addition, snow-sea-ice and ocean samples were made at several ‘ice stations’ between 62- 65°S and 115-121°E to analyze for total mercury and methylmercury. Several mercury and ozone depletion events were observed. This suite of observations provides the most complete suite of observations to date to improve our understanding of the implications of BrO explosion events in the Antarctic under changing future sea-ice conditions.

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Melting and ocean circulation at the front of the Ross Ice Shelf
Craig L. Stewart

Authors

Craig L. Stewart
Scott Polar Research Institute, University of Cambridge, Cambridge, England

Michael J.M. Williams
NIWA, Private Bag 14901, Kilbirnie, Wellington New Zealand

Abstract

Ice shelves form the floating fringe of the Antarctic Ice Sheet and provide an opportunity for the underlying ocean to act on the ice shelf. Despite the importance of these processes very few observations of oceanographic conditions have been made beneath ice shelves due to the extreme difficulty of accessing the cavities.

In November 2010 the first long term oceanographic mooring was deployed through a hot-water borehole into the cavity beneath the Ross Ice Shelf. The mooring is located in the north-west sector of the ice shelf approximately 7km from the ice front. It is located over the deepest point of the cavity entrance (at 900m) and has an ice thickness of ~260m. The mooring was deployed with temperature/salinity loggers and acoustic current meters at 4 depths between the ice base and the seabed. An upward looking acoustic sounder configured to measure basal melting is mounted 15m below the ice base.

Here we present an analysis of the first two years of mooring data with an emphasis on describing the seasonal cycle and the processes which cause higher frequency variability. The mooring shows a clear influence of Antarctic Surface Water during each of the three summers. This penetrates to the mooring site only during summer and is associated with increased melt rates which peak during January. Melt rates at the mooring range from ~1-3m/a with an annual average of ~1.55m/a – approximately an order of magnitude greater than the estimated average for the entire ice shelf but in line with other estimates of near-frontal melting.

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Exploring algae zooplankton relationships in the East Antarctic sea ice zone using Stable Isotope Mixing Models
Kerrie Swadling

Authors

Kerrie Swadling
Institute for Marine and Antarctic Studies, Hobart, University of Tasmania, PB 129, Hobart TAS 7001, Australia

Hugh Jones
Institute for Marine and Antarctic Studies, Hobart, University of Tasmania, PB 49, Hobart TAS 7001, Australia

Abstract

Sea ice provides habitat for high standing stocks of bacteria, algae, protists and invertebrates. The most commonly encountered invertebrates are crustaceans, mainly copepods, which inhabit the brine channel system of the ice-crystal matrix or live at the under-ice surface. Amphipods and krill also live in crevices beneath the sea ice where they forage and find refuge from predators. The trophic status of these ice-associated grazers remains largely unknown, including the relative importance of phytoplankton, ice algae and small metazoans to their diets. A Bayesian isotopic mixing model, SIAR (Stable Isotope Analysis in R), was used to assess the contributions of sea ice algae and phytoplankton to the diets of invertebrates inhabiting the East Antarctic pack ice. Phytoplankton can be distinguished from sea ice algae by their different isotopic profiles. Stable isotope ratios of carbon (13C/12C = del13C) show little enrichment (0.8-1‰) and usually reflect dietary composition, while stable nitrogen isotope ratios (15N/14N = del15N) exhibit a constant rate of incremental enrichment between trophic levels, typically 3 – 4‰, thereby supplying a direct measure of trophic hierarchy. Sea ice algae were generally enriched in carbon over phytoplankton, with the surface-most ice showing the largest difference. For the dominant crustacean grazers nitrogen isotopes suggested mainly herbivory for Calanus propinquus, Thysanoessa macrura and Metridia gerlachei, but omnivory for Euphausia crystallorophias, Euphausia superba and amphipods. The contribution that sea ice algae made to the diets of these species ranged from 0 to > 60% and, importantly, varied substantially in time and space.

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First at-sea telemetry of two threatened populations of pinniped from Campbell Island, New Zealand
Leigh Torres

Authors

L Torres
National Institute of Water and Atmospheric Research, Wellington, 6021, New Zealand

M-A Lea
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia

MA Hindell
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia

J Roberts
National Institute of Water and Atmospheric Research, Wellington, 6021, New Zealand

K Vinette Herrin
Taronga Zoo, Mosman, Sydney, NSW 2088, Australia

RH Mattlin
Marine Wildlife Research Ltd, Richmond, Nelson, 7050, New Zealand

Abstract

The southern elephant seal, Mirounga leonina, has exhibited considerable, inexplicable population declines in many parts of their range. Although they have been studied extensively at their main breeding sites, no at-sea habitat use information exists for animals breeding at Campbell Island where populations have declined by >90% since the 1940s. Juvenile and sub-adult males were fitted with CTD surface relayed data loggers in March of 2012 and 2013 to record their post-moult habitat use and three dimensional diving effort. These data are used to describe their habitat use patterns and describe their rates of interactions with fishing activities on the Campbell Plateau. These tracks reveal diverse distribution patterns across the Campbell Plateau, stretching from 50.5°S to the ice edge at 65°S, and one individual that spent 5 months within the same 20 km2 area. Likewise, the abundance of New Zealand sea lions (Phocarctos hookeri) has dramatically declined over the last decade particularly at the Auckland Island’s colonies where the cause is unclear but often attributed to fisheries by-catch, ecosystem change and increased competition for prey. However, the Campbell Island sea lion population appears stable or increasing, yet has been infrequently studied including no tracking data. In order to examine the foraging behaviour, habitat requirements, and fisheries overlap of the Campbell Island population, and compare these results to data from the Auckland Island population, 15 young female sea lions of 3-5 years' age were equipped with satellite-dive tags in 2012 and 2013. The females were tagged just prior to (n=5) and after (n=10) their annual moult and at least 30 days of movement and dive data were recorded for each animal. Dive and movement data for the young females were related to bathymetry to describe key foraging habitats and were assessed relative to the distribution of fishing vessels. Preliminary results indicate that some overlap with fishing vessel regions occurs at this time of year and that young females typically perform local (within 40km of the island) foraging trips with occasional longer trips (within 150 km of island) to shallow bathymetric features on the Campbell Plateau (50-150m water depth).

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Automated measurements of biogeochemical and ecological cycles: results from the Southern Ocean Time Series
Tom Trull

Authors

Tom Trull
Institute for Marine and Antarctic Studies, University of Tasmania

Abstract

The IMOS Southern Ocean Time Series is located in the central Sub-Antarctic Zone, ~500km southwest of Tasmania. It consists of 3 moorings that measure air-sea exchanges, surface mixed layer biogeochemical processes, and deep sea sinking particle fluxes. These measurements provide information on processes important to climate, carbon cycling, and ocean productivity. This talk will give an overview of the SOTS facility, including opportunities for involvement. SOTS results emphasize the importance of accounting for seasonal cycles in assessments of climate and carbon cycle processes, and the application of advances in automated in-sensor applications for remote marine. As an example of new sensor approaches first time series for the Southern Ocean of hourly measurements of dissolved oxygen and nitrogen (from total gas tension) concentrations. Nitrogen was consistently supersaturated (100.8% - 102.9%), while oxygen was highly subsaturated in early spring (as low as 93.5%) and reached supersaturation during only 17% of the time series in mid-summer. These low oxygen levels emphasize the importance of the Subantarctic Zone in ventilating the upper limb of the overturning circulation, and that this process is incomplete. Using the nitrogen as a proxy for physical processes affecting gas budgets, we separated physical and biological contributions to the oxygen time series, and estimated a seasonal record of net community production (NCP). Almost all NCP occurred in short bursts in spring, in the presence of deep mixed layers as indicated by moored temperature sensors and nearby Argo float profiles, before ceasing at the start of summer in mid-December.

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East Antarctic surface melting Biggest 21st century sea-level change threat?
Stefan W. Vogel

Authors

Stefan W. Vogel
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Alex D. Fraser
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Petra Heil
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Rob Massom
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Neal Young
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Mike Craven
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Abstract

Antarctica driest and coldest place on Earth. The East Antarctic Coast line in summer however provides a contrasting picture. Along the coast surface melting and an extensive network of melt water streams are the dominant features in summer. While Greenland melting is on the forefront of science and with extensive attention given to its inter-annual variability as well its impact on ice dynamics, Antarctic melting has received comparably little attention, with most of the attention coming from broad scale remote sensing applications. Direct measurements validating remote sensing applications are however scars as are estimates of surface accumulation/ablation and fate of melt water during winter. With surface melting being already widespread at the present Antarctic surface melting will only increase under 21st century warming scenarios, raising the question when the East Antarctic margin will catch up with the Antarctic Peninsula and/or Greenland.

This presentation provides a visual overview of melting along the East Antarctic Margin and discusses the potential impact of surface melting on ice dynamics, ice shelf stability and the Southern Ocean environment. In general surface melt water can have a destabilizing effect on ice shelves, while fresh water flux into the ocean impacts thermohaline circulation, sea ice production and the southern ocean ecosystem in general. Potential loss of East Antarctic ice shelves and its buttressing effect, as seen along the Antarctic Peninsula, could easily double the discharge of ice from major East Antarctic outlet glaciers, which would be enough ice to double the rate at which currently sea-level rises.

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Ice dolines in East Antarctica ice-ocean interactions from surface melt water drainage events
Stefan W. Vogel

Authors

Stefan W. Vogel
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Alex D. Fraser
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Petra Heil
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Ben Galton-Fenzi
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

David Alexander
School of Geography, Planning and Environmental Management, University of Queensland, Brisbane, QLD, 4072, Australia

Abstract

Surface melting and melt water streams are common features on outlet glaciers along the East Antarctic coast during summer. A big questions about surface melting in Antarctica is what happens to the melt water? With Antarctic winters being long and cold, most melt water refreezes in the snowpack with little to no impact on the overall mass balance of the ice sheet. One mechanism for surface melt water to reach the ocean and mass being lost from the ice sheet is drainage through ice shelves. Ice dolines are longitudinal surface depression, which are believed to be remains of melt water lakes which drained through the ice. Dolines are reported from various parts of Antarctica and pose a mechanism through which significant amounts of freshwater may reach the ocean beneath ice shelves with potential impact on the sea-ice environment, Antarctic bottom water formation and ocean circulation in general.

Here we revisit the topic of surface melt water drainage and report on the evolution of Amery Ice Shelf Dolines and a very recent doline drainage event on the Mawson Coast. Satellite observations indicate that dolines may be a standing feature, which reforms as the original feature moves with the flow of ice. In addition to the lake drainage events both features (Amery and Mawson coast) are at the receiving end of larger melt water catchment areas and bear the potential that significant amounts of surface melt water drains each year through hidden openings at the bottom of the partially snow covered dolines.

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Surface melting and melt features on the Amery Ice Shelf - implications for ice shelf, ice sheet stability
Stefan W. Vogel

Authors

Stefan W. Vogel
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Alex D. Fraser
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Petra Heil
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Abstract

A general notion about Antarctica is that it is dry and cold. Yet along its coast line significant melting is observed each summer. In various places melt water has been responsible for changes in the dynamic of glaciers, ice sheet and ice shelves. One spectacular event was the collapse of the Larsen B Ice Shelf. Here melt water ponding had a destabilising effect on the ice shelf. Melt water draining through an ice sheet can enhance lubrication of the glacier bed leading to flow acceleration and enhanced ice discharge. Freshwater input to the sub ice shelf environment may enhance thermohaline circulation with the potential of enhancing the draw of warmer water masses into the sub ice shelf cavity.

Here we present initial results investigating surface melting and surface melt-distribution on the Lambert Graben- Amery Ice Shelf. Clearly visible from space, each year a network of lakes and rivers forms on the surface of the Amery Ice Shelf south of Jetty Peninsula (~ 70.5 °S). Surface melt features are absent in the front half of the Amery Ice Shelf likely due to high snow accumulation.

Microwave imagery as well as snow temperature data indicate melting with melt water percolation into and refreezing inside the snow cover. Closer examination of satellite imagery shows an extensive surface hydrological network covering the back of the Amery Ice Shelf transporting melt water over large distances. During high melt years supra glacial lakes can reach tens of kilometres in length and >1 kilometre in width. The most southern surface lake is found adjacent to the Cumpston Massif on the Mellor Glacier (73.5 °S). This is a significant distance upstream from the ice shelf grounding zone and raises the possibility that surface melting under 21st climate warming scenarios could enhance lubrication of East Antarctic outlet glaciers.

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Quantifying the trophic linkages of Antarctic marine predators
Andrea Walters

Authors

A Walters
Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania, Australia
Antarctic and Climate Ecosystems Cooperative Research Centre, Private Bag 80, Hobart, Tasmania, Australia

MA. Lea
Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania, Australia

M Bester
Department of Zoology and Entomology, University of Pretoria, South Africa

M Goebel
NOAA South West Fisheries Science Centre, North Torrey Pines Court, La Jolla, USA

P Trathan
British Antarctic Survey, Madingley Rd, High Cross, Cambridge, UK

G Miller
Division of Pathology and Laboratory Medicine, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia

S Sokolov
CSIRO Marine and Atmospheric Research, Castray Esplanade, Hobart, Tasmania, Australia

J van den Hoff
Australian Antarctic Division, 203 Channel Highway, Kingston, Tasmania, Australia

C Oosthuizen
Department of Zoology and Entomology, University of Pretoria, South Africa

M Hindell
Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania, Australia

Abstract

We assessed the trophic relationships of Antarctic fur seals (Arctocephalus gazella), southern elephant seals (Mirounga leonina)and emperor penguins (Aptenodytes forsteri)by analysing variation in stable isotope values along the length of seal whiskers and in whole blood. Whisker isotopic data, mixing models and concurrent tracking information for fur seals (2008 and 2009) and elephant seals (1995, 1999 and 2005) showed how seals, which breed on opposite sides of the Polar Front (PF), exhibit contrasting winter movement behaviour to access predictable, high food source areas during winter. In the Western Antarctica Peninsula (WAP), fur seals (n=24) migrated north to oceanic waters. Isotopic mixing models estimated the relative proportion and diversity of fish and squid prey to the diets of seals increased from areas close to the WAP in autumn (39.1%) to waters north of the Subantarctic Front (SAF) in spring (84.2%) where no Antarctic krill occurs. In contrast, fur seals in the Indian Sector (Marion Is., n=19) and elephant seals in the Pacific Sector (Macquarie Is., n=23) travelled south towards Antarctica. Some fur seals travelled to the ice edge, with model estimates indicating consumption of crustaceans, such as Antarctic krill (20.9%), in addition to mesopelagic fish and squid (49.6%) in PF and SAF waters. Stable isotope ratios for blood reflected the use of high Antarctic waters by breeding and chick rearing penguins from the Auster colony, Mawson Coast, Antarctica in 2008 (n=156). The isotopic signature of females indicated increased importance of higher trophic level prey (fish and squid) from early to mid-winter, concurrent with a shift in δ15N from 11.2 to 11.8‰. In spring, adults and chicks were segregated by their δ15N signatures indicating adults consumed crustaceans, fish and squid (10.6‰), but fed higher trophic level prey (fish and squid) to their young (11.4‰).

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Pine Island Glacier velocities from Landsat7 images: FFT-based image correlation for images with data gaps
Roland C. Warner

Authors

Roland C Warner
Australian Antarctic Division, Channel Highway, Kingston, Tasmania, 7050, Australia
and Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

Jason L Roberts
Australian Antarctic Division, Channel Highway, Kingston, Tasmania, 7050, Australia
and Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia

Abstract

Remote sensing of ice motion by tracking displacement of surface features is a valuable tool in glaciology. Efficient image feature-tracking programs, such as IMCORR, based on Fast Fourier Transform methods can produce misleading correlations if there are data gaps in either or both of the reference and search images. This is particularly problematic if the data gaps are regular in character, such as for Landsat7 images collected after the failure of the Scan Line Corrector (SLC-off images). We demonstrate that this situation can be alleviated by filling the data gaps with suitably chosen random data. We modified IMCORR to achieve this automatically, but generic image processing software could be used to modify inputs for other correlation packages. We tested our method using images of Pine Island Ice Shelf, Antarctica, and documented the acceleration of the velocity field for the floating extension of the Pine Island Glacier over the decade 2001-2011. We also combined our velocities with recent NASA Operation IceBridge ice thickness data from CReSIS to estimate the basal melt rates for 2010.

Our estimates of total basal melting for the Pine Island Ice Shelf in 2010 are in reasonable agreement with recent oceanographic estimates based on 2009 observations. The indications of changes in basal melt rates are firmer, supporting the approximately 50% increases in basal melt rates seen in both glaciological and oceanographic estimates between 1996 and 2010.

Our simple technique provides the means to use the large archive of Landsat7 imagery to construct time series of ice surface velocities for the recent past.

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Distributed temperature logging on the Amery Ice Shelf challenges and scientific opportunities
Roland Warner

Authors

Roland Warner
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Stefan W. Vogel
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Mike Craven
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Alan Elcheikh
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Adam Christensen
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia

Adam Treverrow
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia

Shavawn Donoghue
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia
Now: Integrated Marine Observing Systems, University of Tasmania, Hobart, TAS, 7000, Australia

Kelly Brunt
University of California San Diego, now - NASA Goddard Space Flight Centre, Greenbelt, MD, 20771, USA

Jeremy Ridgen
formerly: Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia

Steve Cann
formerly: Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia

David Tulloh
formerly: Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia

Scott Tyler
University of Nevada, Reno, NV 89503, USA

Ian Allison
Antarctic Climate and Ecosystem CRC, University of Tasmania, Hobart, TAS, 7000, Australia, Australian Antarctic Division

Ben Galton Fenzi
Australian Antarctic Division, 203 Channel Highway, Kingston, TAS, 7050, Australia, Antarctic Climate and Ecosystem CRC

Abstract

Antarctic ice shelves are coupled to the climate of the Southern Ocean by the sub-ice ocean circulation, with interactions ranging from substantial basal melting to the accretion of thick layers of marine ice. They are vulnerable to increased melting from a warming ocean and from changes in ocean currents. Hidden beneath kilometre thick ice, sub-ice shelf processes are difficult to study. During the 2009/2010 field season the AMSIOR team installed two fibre optic cables through the Amery ice Shelf as part of a sub-ice ocean observation network. Optical fibre light scattering properties can be used for Distributed Temperature Sensing (DTS). DTS measurements provide continuous temperature profiles at a resolution of ~1 m. Here we discuss the opportunities DTS systems provide for sub-ice and englacial temperature monitoring as well as the challenges which come with installing and operating a DTS system in Antarctica, including system set-up and calibration challenges.

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Seasonality of soluble iron and black carbon in the Ross Sea and Southern Ocean
Holly Winton

Authors

Holly Winton
Curtin University, GPO Box U1987, Perth, WA

Ross Edwards
Curtin University, GPO Box U1987, Perth, WA

Andrew Bowie
University of Tasmania, Private Bag 80, Hobart, TAS

Abstract

Past changes in the atmospheric deposition of soluble iron (Fe) to high nutrient low chlorophyll (HNLC) and tropical waters may have stimulated primary production, drawing down atmospheric CO2 and thus initiating changes in global climate. An understanding of the sources (e.g. mineral dust, biomass emissions, fuel combustion, extra-terrestrial dust) and geochemistry of soluble Fe in atmospheric aerosols is critical for determining the impact of Fe deposition on ocean fertility in the past and the future. However, to date no Fe solubility data exists for biomass emissions from Australian fires and there are few estimates of soluble Fe aerosols entering the Southern Ocean. Here we present two seasonally resolved short records of soluble Fe concentrations. The first record is derived from aerosols transported from the Southern Ocean and collected at Cape Grim Baseline Air Pollution Station, northwest Tasmania. Soluble Fe was investigated by a sequential step-wise leaching protocol whereby the water soluble, liable particulate and total fractions of Fe are leached from the aerosols. The second record of soluble Fe is derived from a snow pit on Roosevelt Island, Ross Sea. Seasonal variability in soluble Fe concentrations is attributed to changes in the source e.g. dust and biomass emissions.

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Latest news

  • Conference prize winners
    27 Jun 2013

    The Strategic Science in Antarctica conference concluded yesterday and two days of workshops have commenced. Congratulations to those who were awarded prizes for their contributions to the conference.

  • Watch the welcome message from Australia's Environment Minister
    24 Jun 2013

    In a welcome message via video from Canberra, Australia’s Environment Minister, Tony Burke, reflected on the foresight of earlier decision-makers who agreed to set aside an entire continent for scientific research.

  • Last minute information for attendees
    20 Jun 2013

    There's not too long to wait until the start of the Strategic Science in Antarctica conference, and we hope you’re as excited as we are! Read on for more information about the final program, registration, Twitter, presenters, posters and social functions.

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Key dates

  • 11th June 2013
    Registrations close
  • 21st June 2013
    Registrations at the AAD open for staff
  • 24th June 2013
    Registrations at the venue open
  • 24th June 2013
    Conference commences
  • 26th June 2013
    Conference concludes

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This page was last modified on 6 September 2013.