Icebergs around Antarctica: size distributions, mass fluxes, and local calving rates by using remote sensing and drift modeling

Project description:

Mass flux discharge of the Antarctic ice sheet occurs mainly by iceberg calving and basal melting. A mass discharge of about 2016 Gt per year is caused by calving of icebergs from the floating ice shelves and glaciers.

Within the project, the calculation of mass discharge from Antarctica will be improved, by observing icebergs at various sizes. Therefore, the spatial distribution of icebergs around Antarctica combined with a size classification will be carried out. This will be done by utilizing medium-resolution SAR image mosaics (generated for different years), which cover the whole Antarctic coastline and the adjacent Southern Ocean, and by using an automated iceberg detection algorithm (Fig. 1). The SAR mosaics will also be used to investigate the ice shelf edges with regard to crevasses and recent calving events.



Figure 1. Detection results. (a) shows the input SAR image (image credits: ESA), (b) the results of applying thresholds (white = iceberg, grey = mixture of iceberg and sea ice, black = sea ice) and (c) shows the result of the morphological filtering after thresholding.

Additionally, regional studies of crevasse evolution and the estimation of local calving rates will be done with high-resolution SAR images.

To estimate the mass flux caused by icebergs, information about the initial iceberg masses are needed. An iceberg drift model, buoy data and results from literature (Fig. 2) will be used to track the icebergs back to their origin



Figure 2. Drift tracks of giant icebergs observed by the NIC. Image source: http://www.scp.byu.edu/data/iceberg/database1.html (last visit: 16.06.2011)

Then digital elevation models will be used to determine the thickness of the ice shelf edges and glaciers. A comparison of total iceberg masses, total iceberg areas and iceberg size distributions between different years enables the estimation of inter-annual iceberg mass flux and trend analyses of total iceberg area change or a shift in size distribution.

Scientists

Christine Wesche, Alfred Wegener Institute Bremerhaven

Research areas

Antarctica

Publications

Wesche C, Dierking M, 2011. Iceberg detection in SAR images in two test regions of the Weddell Sea, Antarctica, Journal of Glaciology, in Review.

Wesche C, 2009. Evaluation and application of GPS and altimetry data over central Dronning Maud Land, Antarctica: annual elevation change, a digital elevation model, and surface flow velocity. PhD thesis, University of Bremen

Wesche C, Riedel S, Steinhage D, 2009. Precise surface topography of the grounded ice tongues at Ekströmisen, Antarctica, based on several geophysical data sets, ISPRS Journal of Photogrammetry and Remote Sensing 64, 381-386., doi:10.1016/j.isprsjprs.2009.01.005

Wesche C, Eisen O, Oerter H, Schulte D, Steinhage D, 2007. Surface topography and ice flow in the vicinity of the EDML deep-drilling site, Antarctica., Journal of Glaciology, 53(182), 442 - 448.

Wesche C, Dierking W, 2010. Separation of icebergs and sea ice in SAR images, Proceedings of ESA Living Planet Symposium, 28 June - 2 July 2010, Bergen, Norway / European Space Agency, H. Lacoste-Francis, (ed.), 1 CD-ROM. Noordwijk : ESA Communication Production Office (SP / European Space Agency ; 686)(ESA-SP ; 686).

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Research funding organisation

German Research Foundation

Project number: WE 4772/1
Funding period: 2011 - 2014