"Antarctic sea ice thickness from space: validating estimates from the laser and radar satellite altimeters with ship-based measurements" is a three year project funded by NASA Cryosphere Program (#NNX08AQ87G) from 06/03/2008 – 06/02/2011.

Project Summary

The Antarctic sea ice zone remains one of the least known regions of the Earth's surface. Both passive and active microwave remote sensing have provided useful information about sea ice extent in both polar regions and its trend of changes over 30 years. Results indicate consistently a large decrease in Arctic sea ice extent (3%/decade), while in the Antarctic, changes are small. Submarine-based ice thickness measurements have shown greater decreases than extent in Arctic ice thicknesses, up to 40% (10%/decade), over the past 30 years. Without submarines traversing the Antarctic sea ice zone however, there are no estimates of ice thickness change, or even circumpolar mean sea ice thickness for the Antarctic region. Using radar and laser satellite altimeters, it is postulated that the measurement of snow and ice surface elevations over sea ice can be used to derive the sea ice thickness using an isostatic relationship between the above and below sea level portions of the ice cover.

For Antarctic sea ice, however, work on computing ice thicknesses from satellite algorithms, either laser or radar, are still in a developmental and unvalidated state. Data from ground-based surveys of ice thickness and surface elevation (combined snow depth and ice elevation) have indicated a more complex relationship between elevation and thickness than predicted by simple isostasy for computing ice thickness, as currently attempted using satellite laser altimetry. Similarly, the presence of significant areas of flooded ice with sea water at the ice surface-snow interface in the Antarctic differs from the Arctic surface case, suggesting radar algorithms based on positive ice elevation may need adjustment for the Antarctic flooded condition with negative ice elevation. We propose to develop and test new models or algorithms, to convert surface elevations into sea ice thickness, based on data on both elevation and thickness currently available. We propose to use data gathered from ships over the past twenty years on surface elevation, ice elevation and ice thickness, from several regions of the Antarctic sea ice zone to develop relationships that will test existing algorithms, evaluate alternative algorithms and provide error estimates on sea ice thickness derived from satellite altimetry. We will also use results obtained as ground truth data for satellite altimeters during two ship studies, also headed by the investigators here, currently scheduled for International Polar Year (IPY) in 2007 in two different regions of the Antarctic sea ice zone. Determining the baseline thickness of Antarctic sea ice has been identified as the primary objective by Antarctic Sea Ice in IPY, an international project endorsed for IPY.

Personnel

News and Reports

• LRSG/UTSA awarded a NASA supplement for Education to develop "Polar and Planetary Sciences Modules for K-12 Teachers" (30K for 2010-2011), (PI Ackley, CoPIs Xie and Fies)
• LRSG/UTSA researches/publications highlighted in the June 2009 issue of NOTUS, the AGCS Newsletter
• Our NASA project co-funding the ISSI workshop "Monitoring Arctic and Antarctic sea ice form various satellite products" held on 15-19 March, 2010 at the ISSI, Bern, Switzerland. Workshop team leaders Burcu and Hongjie.
• Project First Year Annual Report (2008-2009) to NASA
• Project Second Year Annual Report (2009-2010) to NASA
• Antarctic Sea Ice Workshop, Lucca, Italy (March 22-24, 2009) Final Report

Publications

Worby, A., A. Steer, J. Lieser, N. Galin, D. Yi, I. Allison, P. Heil, R.A. Massom, and J. Zwally, 2010. Regional-scale sea ice and snow thickness distributions from in situ and satellite measurements over East Antarctica during SIPEX. Deep Sea Research II, 58:9-10, 1125-1136. doi:10.1016/j.dsr2.2010.12.001

Ozsoy-Cicek, B., Kern, S., Ackley, S.F., Xie, H., Tekeli, A.E., 2011. Intercomparisons of Antarctic sea ice properties from ship observations, active and passive microwave satellite observations in the Bellingshausen Sea. Deep Sea Research II, 58:9-10, 1092-1111. doi:10.1016/j.dsr2.2010.10.031

Xie, H., S.F. Ackley, D. Yi, H.J. Zwally, P. Wagner, B. Weissling, M. Lewis, K. Ye 2010, Sea ice thickness distribution of the Bellingshausen Sea from surface measurements and ICESat altimetry, Deep Sea Research II, 58:9-10, 1039-1051. doi:10.1016/j.dsr2.2010.10.038

Lewis, M. J., Tison, J. L., Weissling, B., Delille, B., Ackley, S. F., Brabant, F., Xie, H., 2011. Sea ice and snow cover characteristics during the winter-spring transition in the Bellingshausen Sea: an overview of SIMBA 2007, Deep Sea Research II, 58:9-10, 1019-1038. doi:10.1016/j.dsr2.2010.10.027

Xiaodong Huang, Hongjie Xie, Tiangang Liang, Donghui Yi (2011) Estimating vertical error of SRTM and map-based DEMs using ICESat altimetry data in the eastern Tibetan Plateau, International Journal of Remote Sensing, 32:18, 5177-5196. doi:10.1080/01431161.2010.495092

Weissling, B. and S.F. Ackley, Antarctic sea ice altimetry: scale and resolution effects on derived ice thickness distribution, IGS. (presented at IGS Tromso Norway, June 2010)

Gao, Y., H. Xie, N. Lu, T. Yao, and T. Liang, 2010. Toward advanced daily cloud-free snow cover and snow water equivalent products from Terra-Aqua MODIS & Aqua AMSR-E measurements. Journal of Hydrology. doi:10.1016/j.jhydrol.2010.01.022

Gao, Y., H. Xie, T. Yao, and C. Xue, 2010. Integrated assessment on multi-temporal and multi-sensor combination for reducing cloud obscuration of MODIS snow cover products at the Pacific Northwestern USA. Remote Sensing of Environment. doi:10.1016/j.rse.2010.02.017

Fan, C., H. Xie, D. Schulze-Makuch, S.F. Ackley, 2010. A formation mechanism for hematite-rich spherules on Mars. Planetary and Space Science 58(3):401-410. doi:10.1016/j.pss.2009.11.001

Weissling, B., S.F. Ackley, P. Wagner, and H. Xie, 2009. EISCAM - Digital image acquisition and processing for sea ice parameters from ships. Cold Regions Science and Technology, 57(1): 49-60. doi:10.1016/j.coldregions.2009.01.001

Ozsoy-Cicek, B., H. Xie, S.F. Ackley, and K. Ye, 2009. Antarctic summer sea ice concentration and extent: comparison of ODEN 2006 ship observations, satellite passive microwave and NIC sea ice charts. The Cryosphere, Vol.3 (1):1-9. doi:10.5194/tc-3-1-2009

Wang, X. and H. Xie, 2009. New methods for studying the spatiotemporal variation of snow cover based on combination products of MOIDS Terra and Aqua. Journal of Hydrology, Vol 371:192-200. doi:10.1016/j.jhydrol.2009.03.028

Ackley, S.F., M.J. Lewis, C.H. Fritsen, and H. Xie, 2008. Internal melting in Antarctic sea ice: development of "Gap Layers." Geophysical Research Letters, 35, L11503. doi:10.1029/2008GL033644