Hydrologic Responses to a Shrinking Arctic Sea Ice Cover
The focus of this project will be to test the hypothesis that the loss of Arctic sea ice and northern high latitude snow cover will invoke changes in the seasonality, spatial distribution and magnitudes of precipitation (P) and net precipitation (P-E) over the Arctic, which along with attendant rises in temperature, have ramifications for the freshwater budget of the Arctic Ocean and the mass balance of the Greenland ice sheet.
Regarding the relevant processes underlying these changes, we expect that: (a) sea ice loss will lead to an increase in available water vapor over the Arctic Ocean and peripheral seas, most pronounced in autumn and winter, when delayed ice formation and thinner ice will promote large vertical fluxes of heat and moisture into the atmosphere; (b) loss of sea ice and terrestrial snow cover will invoke changes in Arctic circulation patterns and hence patterns of water vapor convergence, driven in autumn and winter by enhanced vertical heat fluxes and during the warm season by altered differential heating over the Arctic Ocean and surrounding land; (c) in lying "downwind" of the Arctic Ocean as well as adjacent to the (presently) partially ice-covered East Greenland Sea and Baffin Bay, the Greenland ice sheet will feel these changes both through impacts on accumulation and surface melt.
The primary analysis tool will be Polar WRF, a recently developed regional climate model optimized for polar applications. Control simulations will be conducted for several Arctic domains, focusing on the past few years which are characterized by extremely low September sea ice extent, with lateral forcing supplied from the NCEP/NCAR reanalysis, and sea ice conditions prescribed from satellite-based observations. Generated fields of key hydrologic variables (precipitable water, precipitation, vapor flux convergence, net precipitation, temperature) and atmospheric circulation will be contrasted with those from a series of experiments with altered sea ice and snow cover. These will include simulations with climatological maximum winter ice extent and concentration through the annual cycle, prescribed reductions in ice extent and concentration larger than those observed, 100% and 0% terrestrial snow cover maintained over the annual cycle but with observed sea ice conditions, and observed sea ice conditions but with increased sea surface temperature over open water areas in summer.