Title: Assessing changes in the terrestrial environment: a soil climate monitoring network

Presenter: Megan Balks

University of Waikato

Authors: Megan R. Balks¹, Holly E. Goddard², Cathy Seybold³

1 - University of Waikato, Hamilton, New Zealand, m.balks@waikato.ac.nz

2 - Reservoir Chemistry, MB Century, Wairakei, Taupo, New Zealand, HGoddard@mbcentury.com

3 - National Soil Conservation Service, USDA, Lincoln, Nebraska, USA, cathy.seybold@lin.usda.gov

Abstract

A network of nine sites monitors soil climate in the McMurdo Sound - Dry Valleys region with limited additional data available from Cape Hallet (72°S) and Darwin Glacier (79.5°S). Measurements include soil and upper permafrost temperatures and the usual suite of above-ground climate measurements, with up to 13 years of hourly data now available (http://www.wcc.nrcs.usda.gov/scan/Antarctica/antarctica.html). Thus we can accurately determine the depth of the active layer (or depth to permafrost) which is a sensitive indicator of environmental change and an integrator of many climate variables. Characterisation of the soil climate is important for understanding the environmental limitations for soil ecosystems and is contributing to underpinning the development of the Environmental Domains programme.

In the 1999-2012 period there has been marked between-season variability in summer temperatures and active layer depths. Only one station (Marble Point) had any warming trend over the measurement period. Mean annual air temperatures ranged from -15.3°C at Cape Hallett to -22.4 °C at Victoria Valley. Mean cumulative days per summer with air temperature >0°C ranged from 33 at Wright Valley to zero at Mt Fleming. Soils have longer periods of thaw over summer with mean cumulative days with temperature > 0°C at ~20 cm depth ranging from 66 days at Granite Harbour to 2 days at Victoria Valley and zero at Mt Fleming. Mean annual wind speeds ranged from 45kmhr^-1 at Darwin Glacier to 7kmhr^-1 at Granite Harbour with little between-year variability. There is variability between stations in predominant wind direction and seasonal wind patterns.

Title: Past, present, future: quantifying present-day Antarctic ice mass changes relies on new ice history constraints

Presenter and Author: Matt King

University of Tasmania, Hobart, Tasmania, Australia
Newcastle University, Newcastle upon Tyne, United Kingdom
Matt.King@utas.edu.au

Abstract

Evolution of the Antarctic Ice Sheet’s extent since the Last Glacial Maximum (LGM) is surprisingly poorly constrained by data. Onshore, LGM ice extent data exist at less than ~20 sites, with that number reducing at more recent times. Offshore, while bathymetric data exist for much of the coastal margin it consists mainly of single profiles and, as such, does not provide the spatial detail required to constrain paleo ice flow, thickness and retreat history. Consequently, the transition of the ice sheet from LGM to present-day is poorly understood, and the degree to which the present ice sheet continues to adjust to past changes is also poorly known.

Interest in post-LGM Antarctic ice history has been renewed recently due to the GRACE satellite mission, which measures changes in Earth’s gravity field. GRACE cannot decouple changes in ice mass from changes within the solid Earth which have in turn been induced by post-LGM ice mass changes. Recent forward ice sheet modelling has resulted in significant downward revisions of predicted total LGM ice volume, but these models cannot be verified in most places at most time-steps. Thus, glacial isostatic adjustment (GIA) is highly uncertain, making GRACE measurements of present-day ice mass change also uncertain. This talk will highlight differences in recent GIA models and ice sheet reconstructions and highlight the areas where a ten-fold or greater increase in observation density is required in order to satisfactorily assess the accuracy of GIA models and provide constraints on a new generation of ice sheet reconstructions.