The Arctic’s rapidly shrinking sea ice cover: a research synthesis

TLDR

The rapid decline of September sea ice minima over the past decade signals an accelerating Arctic response to external forcing, hastening the transition to a seasonally open ocean. This acceleration arises from extensive September open water producing thin first‑year ice that melts more readily, amplifying summer albedo feedback, increasing retreat under anomalous heat, and with overall Arctic warming reducing the likelihood of cold‑year recovery.

Abstract

The sequence of extreme September sea ice extent minima over the past decade suggests acceleration in the response of the Arctic sea ice cover to external forcing, hastening the ongoing transition towards a seasonally open Arctic Ocean. This reflects several mutually supporting processes. Because of the extensive open water in recent Septembers, ice cover in the following spring is increasingly dominated by thin, first-year ice (ice formed during the previous autumn and winter) that is vulnerable to melting out in summer. Thinner ice in spring in turn fosters a stronger summer ice-albedo feedback through earlier formation of open water areas. A thin ice cover is also more vulnerable to strong summer retreat under anomalous atmospheric forcing. Finally, general warming of the Arctic has reduced the likelihood of cold years that could bring about temporary recovery of the ice cover. Events leading to the September ice extent minima of recent years exemplify these processes.