4.11 Sensitivity of Arctic circulation to changes in sea ice cover in the WRF model

Tuesday, 3 May 2011: 4:30 PM
Rooftop Ballroom (15th Floor) (Omni Parker House )
David F. Porter, CIRES/Univ. of Colorado, Boulder, CO; and J. J. Cassano and M. C. Serreze

The Arctic landscape has been experiencing dramatic changes in the past several decades. Arguably, the most striking changes are in the sea ice cover. While the causes of these changes are somewhat well known, the impacts of the sea ice loss are still being actively researched. Here, we chose to use the WRF version 3.2.1 model to explore the sensitivity of the large-scale circulation to prescribed changes in Arctic sea ice. Observed sea ice fraction and SST from 1996 and 2007, representing high and low sea ice years, respectively, are used as the WRF lower boundary conditions. Two sets of WRF simulations are run with these sea ice / SST states and lateral boundary conditions supplied by ERA-Interim from 1994 through 2008. The resulting 15-member ensemble for each lower boundary condition samples a large range of the true climatic variability. Results of the simulations show that there are both local and remote responses to the sea ice reduction. The local barotropic response is dominated by a vertically deep heating of the troposphere due to large sensible and latent heat flux increases in the area of sea ice loss. Remote changes, brought about by changes in the large-scale circulation, persist for months after the largest sea ice anomaly. These changes in the Arctic circulation drive changes in precipitation, temperature, and snow pack, both in the Arctic and at lower latitudes.
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