Atmospheric responses to Arctic sea ice loss in a high-top atmospheric
general circulation model
Abstract
Rapid Arctic warming and sea ice decline in recent decades might have
profound impacts on midlatitude weather and climate. This study uses a
high-top atmospheric general circulation model - Whole Atmosphere
Community Climate Model version 6 (WACCM6) - to investigate the
atmospheric responses to the Arctic sea ice reduction, including impacts
on mid-latitude blocking and cyclones. The high-top configuration (top
layer at about 100 km or 0.001 hPa) together with the finer vertical
resolution (70 layers) in WACCM6 allow more realistic representation of
stratosphere-troposphere interactions. The sea ice impact during
1979-2015 is obtained by comparing ensemble simulations forced by daily
observational sea ice concentration (SIC) and sea surface temperature
(SST) to simulations where the time-varying SIC is replaced by a daily
SIC climatology. A series of SIC-SST adjustments are performed to
minimize unrealistic SIC and SST forcings used in the simulations. Each
ensemble consists of 30 members with slightly different atmospheric
initial conditions in order to separate forced atmospheric responses
from internal model spread.