Clear‐sky thermodynamic and radiative anomalies over a sea ice sensitive region of the Arctic

Monthly clear‐sky anomalies of atmospheric temperature and water vapor over the East Siberian and Laptev Sea regions of the Arctic for 2003–2010 are examined here. This region experiences significant interannual variations in sea ice concentration and is also where ice loss was most apparent in the record year 2007. Clear‐sky thermodynamic profiles come from the Atmospheric Infrared Sounder (AIRS) sensor onboard the Aqua satellite. Associated longwave (LW) and shortwave (SW) radiation‐flux anomalies are estimated through radiative transfer modeling. Anomalies of temperature (±10 K) and water vapor (±1 g kg −1 ) often positively covary, resulting in distinct signatures in the clear‐sky downwelling LW (LWD) anomalies, occasionally larger than ±10 W m −2 around the 2003–2010 climatology. Estimates of mean greenhouse anomalies indicate a shift from negative to positive anomalies midway through the 8‐year record. Sensitivity tests suggest that temperature anomalies are the strongest contributor to both LWD and greenhouse anomalies, relative to water‐vapor anomalies; monthly averaging of column precipitable water yields relatively small anomalies (order 1 mm) that produce a linear response in greenhouse anomalies. Finally the clear‐sky contribution to 2007 monthly ice thickness is estimated. Anomalous clear‐sky radiation retards the total 2007 ice thickness by 0.3 m (15–30% of ice‐thickness climatology), and anomalous LW radiation is most important for preconditioning the ice during the months prior to, and after, the summer melt season. A highly sensitive interaction between cloud fraction, surface albedo and LWD anomalies is found, and we develop a metric for determining clear‐sky anomalous ice melt potential.