Atmospheric warming during rapid sea ice loss over the Barents-Kara seas in winter

The atmospheric temperature change associated with rapid sea ice loss events over the Barents-Kara Seas (BKS) is explored. Rapid sea ice loss events are defined as periods with a tendency for sea ice concentration averaged over BKS to be below the fifth percentile of the probability density function distribution during the winters of 1979-2020 for at least three consecutive days. Composite analysis shows that there is a significantly positive bottom-amplified temperature anomaly ahead of the rapid sea ice loss, which is closely associated with a wave train composed of a Ural blocking and an upstream positive phase of the North Atlantic Oscillation. This structure is favorable for the transport of warm and moist air into the BKS, and therefore, the tropospheric temperature, including the surface air temperature, increases through horizontal warm-temperature advection, specifically through warm advection of the climatological temperature by the anomalous wind. The cooling over the BKS due to the adiabatic effect and vertical mixing opposes the horizontal warm-temperature advection above and below about 900 hPa, respectively. However, an increase in skin temperature prominently results from enhanced downward long-wave radiation, which is also the main contributor to the rapid sea ice loss.