HR: 1340h
AN: C33B-0346    [Abstracts]
TI: Seasonal Variation of Antarctic Sea-Ice Freeboard Heights and Thicknesses from ICESat
AU: * Yi, D
EM: donghui@icesat2.gsfc.nasa.gov
AF: Raytheon ITSS, NASA, Goddard Space Flight Center, Code 971, Greenbelt, MD 20771 United States
AU: Zwally, H J
EM: zwally@icesat2.gsfc.nasa.gov
AF: NASA, Goddard Space Flight Center, Code 971, Greenbelt, MD 20771 United States
AB: The distribution of sea ice affects Earth's radiative balance and atmosphere and ocean circulation. The study of sea-ice thickness distribution and volume variation is an important part of understanding the Earth's climate system. ICESat measures the mean surface elevation of flat surfaces to better than 3 cm over its 70 m laser footprints spaced at 170 m. This provides an important tool to study sea ice. Previous knowledge of Antarctic sea-ice freeboard and thickness is based on very limited information from surface and ship-based measurements. The ICESat orbit has an inclination of 94ø and its ground tracks cover all sea ice surrounding Antarctica. Using open water and thin ice as reference sea level, a novel technique has been developed to measure sea-ice freeboard using ICESat measured elevation data. With estimates of snow, brine, and sea-ice density, combined with snow depth data from AMSR-E, sea-ice thickness can be derived from the freeboard. Sea-ice freeboard and thickness were calculated along ICESat ground tracks first and then gridded to 50 x 50 km grid maps. Three periods of Antarctic sea-ice freeboard and thickness data have been studied. Sea-ice freeboard and thickness distributions show clear seasonal variation. During the Antarctic winter (Oct-Nov, 2003), sea ice grows to its seasonal maximum. Thicker sea ice surrounds the Antarctic continent; thinner sea ice is distributed near Princess Ragnhild Coast and the Amundsen and Bellingshausen Seas; the mean thickness of winter sea ice is 2.9 m. During the Antarctic summer (Feb-Mar, 2004), thinner sea ice melts away. Sea ice is mainly distributed in the Weddell Sea near the Antarctic Peninsula and Ross Sea, with a mean thickness of 2.4 m. During the Antarctic fall (May-Jun, 2004), large areas of new, thinner sea ice forms. Thinner sea ice covers large areas of the Weddell and Ross Seas, and the overall mean thickness is 1.9 m. Overall, ICESat measurements provide unprecedented accuracy and spatial and temporal coverage of sea-ice freeboard and thickness and can be used to monitor sea-ice volume, which is an indicator of climate change.
DE: 4207 Arctic and Antarctic oceanography
DE: 4215 Climate and interannual variability (3309)
DE: 1827 Glaciology (1863)
DE: 1863 Snow and ice (1827)
DE: 1640 Remote sensing
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting