Understanding the Mechanism of Arctic Amplification and Sea Ice Loss

Sea ice melting is accelerating in the Barents and Kara Seas. Several mechanisms are proposed to explain the accelerated loss of polar sea ice, which remains an open question. In the present study, the detailed physical mechanism of sea ice melting in winter is identified using the daily ERA interim reanalysis data. Downward longwave radiation is an essential element for sea ice melting, but can only be sustained by excessive upward heat flux from the sea surface exposed to air in the region of sea ice loss. This energy is used to increase air temperature in the lower troposphere, which in turn increases downward longwave radiation. This feedback process is clearly observed in the Barents and Kara Seas in the reanalysis data. A quantitative assessment reveals that this feedback process is amplifying at the rate of ~8.9% every year during 1979-2014. Based on this estimate, sea ice will completely disappear in the Barents and Kara Seas by around 2022. Availability of excessive heat flux is necessary for the maintenance of this melting feedback process; a similar sea ice melting mechanism is expected to take place over the sea-ice covered polar region when sea ice is not fully recovered in winter.