Cooperative Institute for Research in Environmental Sciences

Local and large-scale atmospheric responses to reduced Arctic sea ice and ocean warming in the WRF model

Porter, D.F., J.J. Cassano, and M.C. Serreze

2012, Journal of Geophysical Research, 117, D11115, doi:10.1029/2011JD016969.

One of the most striking changes in the Arctic is the decline in sea ice extent. While the causes of this decline have been widely researched, there is growing recognition that sea ice loss will have substantial environmental impacts both within and beyond the Arctic. Here, the WRF model (version 3.2.0) is used to explore the sensitivity of the large-scale atmospheric circulation to prescribed changes in Arctic sea ice. Observed sea ice fractions and sea surface temperatures (SSTs) from 1996 and 2007, representing years of high and low sea ice extent, respectively, are used as WRF lower boundary conditions. ERA-Interim reanalysis data from 1994 to 2008 are used as lateral forcing data for each high and low sea ice state. This yields two 15-member ensembles that sample a large range of true climatic variability.

Results of the simulations show both local and remote responses to the sea ice reduction. The local response is largest in October and November, dominated by increased turbulent heat fluxes resulting in a vertically deep heating and moistening of the Arctic atmosphere. Significant warming and moistening persists through November. This warmer and moister atmosphere is associated with an increase in cloud cover, affecting the surface and atmospheric energy budget. There is an enhancement of the hydrologic cycle, with increased evaporation in areas of sea ice loss paired with increased precipitation. Summertime changes in the hydrologic cycle reflect circulation responses to mid-latitude SSTs, highlighting the general sensitivity of the Arctic climate.