Monitoring Arctic Sea Ice Thickness Change with ICESat, IceBridge and ICESat-2
Farrell, Sinead1; Kurtz, Nathan2; McAdoo, David1; Zwally, H Jay2; Yi, Donghui2
1University of Maryland, UNITED STATES; 2NASA Goddard Space Flight Center, UNITED STATES
Arctic sea ice has experienced rapid change in its composition over the last decade, transitioning from a predominantly thick, multi-year ice pack to a thinner, increasingly seasonal pack. Observations of sea ice extent and thickness reveal a continuing downward trend, with the September sea ice extent now declining at a rate of -13 % per decade, faster than models predict. These observed shifts in the sea ice mass-balance are a leading indicator of global climate variability.
Satellite altimetry observations of Arctic sea ice from the ICESat and CryoSat-2 missions indicate a significant decline in ice thickness, and volume, over the last ten years. The greatest losses have been observed in the oldest, multi-year ice areas. In this presentation we discuss the regional trends in ice thickness derived from ICESat laser altimetry, contrasting observations of the multi-year ice pack with seasonal ice zones. The ICESat mission ceased operation in 2009, and the final, reprocessed data set became available recently. We describe our current efforts to more accurately convert from freeboard to ice thickness, with a modified methodology that corrects for range errors, instrument biases, and includes an enhanced treatment of snow depth and ice density with respect to ice type. We extend our analysis to March 2012 using data from the NASA IceBridge airborne mission, which commenced operations in 2009.
With the planned launch by NASA of ICESat-2 in 2016 we may expect continuity of the sea ice thickness time series until at least the end of this decade. Data from this mission, together with ongoing observations from CryoSat-2, will allow us to understand whether recent observations are part of a sustained negative trend, or a reflection of the natural, interannual variability of a complex climate system. We briefly describe the current status of the ICESat-2 sea ice data products, and we demonstrate the utility of micro-pulse, photon-counting laser altimetry over sea ice, based on analysis of new data from the MABEL instrument, an airborne simulator for ICESat-2.