Atmospheric Inversion Strength over Polar Oceans in Winter Regulated by Sea Ice 1 2

1 2 Low-level temperature inversions are a common feature of the wintertime troposphere in 3 the Arctic and Antarctic. Inversion strength plays an important role in regulating 4 atmospheric processes including air pollution, ozone destruction, cloud formation, and 5 negative longwave feedback mechanisms that shape polar climate response to 6 anthropogenic forcing. The Atmospheric Infrared Sounder (AIRS) instrument provides 7 reliable measures of spatial patterns in mean wintertime inversion strength when 8 compared with available radiosonde observations and reanalysis products. Here, we 9 examine the influence of sea ice concentration on inversion strength in the Arctic and 10 Antarctic. Correlation of inversion strength with mean annual sea ice concentration, 11 likely a surrogate for the effective thermal conductivity of the wintertime ice pack, yields 12 strong, linear relationships in the Arctic (r=0.88) and Antarctic (r=0.86). We find a 13 substantially greater influence of sea ice concentration on surface air temperature than 14 temperature at 850 hPa, lending credence to the idea that sea ice controls inversion 15 strength through modulation of surface heat fluxes. As such, declines in sea ice in either 16 hemisphere may imply weaker mean inversions in the future. Comparison of mean 17 inversion strength in AIRS and global climate models (GCMs) suggests that most GCMs 18 poorly characterize mean inversion strength at high latitudes.