Summer melt regulates winter glacier flow speeds throughout Alaska

TitleSummer melt regulates winter glacier flow speeds throughout Alaska
Publication TypeJournal Article
Year of Publication2013
AuthorsBurgess, EW, Larsen, CF, Forster, RR
JournalGeophysical Research Letters
KeywordsAlaska, Ice Dynamics, Mountain Glaciers, Offset Tracking, Sub-Glacial Hydrology, Winter

Predicting how climate change will affect glacier and ice sheet flow speeds remains a large hurdle towards accurate sea level rise forecasting. Increases in surface melt rates are known to accelerate glacier flow in summer, whereas in winter, flow speeds are believed to be relatively invariant. Here we show that wintertime flow speeds on nearly all major glaciers throughout Alaska are not only variable but are inversely related to melt from preceding summers. For each additional meter of summertime melt, we observe an 11% decrease in wintertime velocity on glaciers of all sizes, geometries, climates and bed types. This dynamic occurs because inter-annual differences in summertime melt affect how much water is retained in the sub-glacial system during winter. The ubiquity of the dynamic indicates it occurs globally on glaciers and ice sheets not frozen to their beds and thus constitutes a new mechanism affecting sea level rise projections.