ABSTRACT
Arctic Amplification (AA) is one of the most striking climate trends taking place over recent decades, with the two-fold increases in the surface air temperature (especially in winter), as compared to the global average. Concurrently, the Arctic sea ice extent (SIE) has plummeted rapidly, especially in September when the SIE reaches its annual minimum. Besides AA and the rapid Arctic SIE decline, there is also substantial year-to-year variability and decadal variability of SIE superimposed on the long-term trend since the satellite-based observation began in late 1978. In this work, we examine this ongoing SIE loss across the four decades (1979–88, 1989–98, 1999–2008, and 2009–18), using statistical tools such as trends and correlation. Our analysis is based on SIE derived from the passive microwave satellite sea ice concentration and atmospheric variables derived from the reanalysis products. The Seas of Okhotsk and Japan, Bearing Sea and the Gulf of Saint Lawrence showed higher trends during December to May, while the Hudson Bay, Canadian Archipelago and Central Arctic showed higher trends during June to November. For 2009–18, the seas of Bearing, Greenland, Kara and Barents Seas, and Central Arctic Ocean exhibited sea ice loss, while the Hudson Bay, Canadian Archipelago, Baffin Bay and the Labrador Sea, and the Gulf of St. Lawrence showed increases in the SIE. A significant influence of ocean surface warming on the SIE was revealed for autumn, winter and spring. Atmospheric warming also contributed to the SIE changes across the decades. The SIE in the Greenland Sea and Gulf of Saint Lawrence experienced a lower impact of atmosphere/ocean warming. Overall, the SIE for the Northern hemisphere (NH) was significantly influenced by atmosphere/ocean surface warming for summer and autumn for 1999–2008 and 2009–2008. Changes in the wind speed and heat flux played a secondary role in the SIE decline. The physical mechanisms responsible for the Arctic sea ice decline include thermodynamic processes consisting of changes in air temperature, radiative and turbulent energy fluxes, and ocean heat storage, and dynamical processes such as changes in winds and ocean currents, which manifest through regional and remote forcing climate indices.
