Sea ice

Simulations of sea ice dynamics suggest that some of the most marked responses to climate change would be expected to occur in the high latitudes, and in particular in the Arctic. Sea ice modulates planetary heat transport by insulating the ocean from the cold polar atmosphere, and also by modulating the thermohaline circulation of the world ocean through the process of brine rejection. Moreover, the high albedo of snow-covered ice further insulates the polar oceans from solar radiation and introduces another positive feedback in the climate system. Simulations of future climate are therefore very sensitive to the ways in which the high latitudes are represented in models of the climate system. By supporting the development and analysis of extensive and novel observations of the polar regions acquired by current space-based systems such as DMSP, Radarsat, QuikSCAT and future missions such as EOS Aqua and ICESat, to be operational in the 2001 timeframe. NASA has an important role to play in helping to refine the way in which high latitude climate and the polar oceans and sea ice in particular are simulated.

These same observations and analysis methods can also be used to establish the nature and significance of current change in the high latitudes. Time series of sea-ice concentration data are critical for identifying interannual and decadal fluctuations that could point to the existence of significant changes in oceanic and atmospheric circulation at high latitude. Changes in the large-scale circulation of the ice pack may provide insight in the response of the high latitude environment to, and in turn influence on, changes in ocean and atmosphere circulation at lower latitudes. Other efforts are being directed towards obtaining additional information about the polar regions. In recent years much attention has been focused on describing teleconnections between elements of the climate system at high latitudes, which has been made possible through the advent of wide-coverage observations of a variety of geophysical parameters that now extend back, in many cases, for 2 or more decades.

Studies that can shed light on the extent to which climate at high latitudes is effectively and responsively linked to climate at lower latitudes through any oceanographic or sea ice response are important. Such studies will help to determine the amplitude and rapidity of the response of the climate system as a whole to any greenhouse gas - induced warming. Key elements of interaction include freshwater import (from rivers) and export, ice mass re-distribution, thermohaline circulation and atmospheric dynamics particularly in the marginal ice zone. The key is to be able to devise a strategy that enables the importance of these linkages to be evaluated and this is likely to require close coupling of modeling and observational analysis.