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

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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This page was last modified on 24 September 2013.