Geophysical Research Letters, 10 March 2022
Much of Arctic sea ice research focuses on summer sea ice loss; but this study found that the Arctic has now lost one-third of its winter sea ice volume in the past 20 years as well, including a large amount of its thick, multi-year ice. This decline in sea ice is largely driven by the replacement of multi-year ice with thinner “seasonal” ice, which melts completely each summer rather than accumulating over several years. Multi-year ice tends to be thicker and therefore more resistant to melting. Since 2019, however, rising global temperatures have thinned Arctic multi-year ice by 0.5 meters – losing 16% of its remaining total volume in only three years. The complete loss of multi-year sea ice will result in ice-free summers in the Arctic, when the older ice thick enough to survive the melt season is gone. This study brings together decades of satellite data to estimate past ice thickness and the depth of snow on top, and these findings suggest that previous estimates may have been overestimating sea ice thickness by as much as 20%. This underscores the importance of reducing emissions to curb rising temperatures, and protect the global climate system from the cascading consequences of losing summer sea ice cover.