Maximum late Holocene extent of the western Greenland Ice Sheet during the late 20th century

Abstract

The pattern of Greenland Ice Sheet margin change during the 20th century is variable. Large-scale retreat of marine-outlet glaciers contrasts with the often-negligible retreat observed along land-terminating margins of the ice sheet. We reconstruct a chronology of ice-margin change for two land-terminating ice margins in western Greenland using radiocarbon and 10Be exposure dating. Our results indicate that two land-terminating lobes attained their maximum late Holocene position in the late 20th century. This contrasts with the nearby marine-terminating Jakobshavn Isbræ, which achieved a maximum late Holocene position during the Little Ice Age, and has since retreated ca 40 km. In addition, we survey ice-margin change across western Greenland, utilizing satellite imagery. We find that many land-terminating sectors of the ice sheet, in addition to our study area, may have attained their maximum late Holocene extent during the 20th century. This suggests a lagged ice-margin response to prior cooling, such as the Little Ice Age, which would imply significant retreat of land-terminating sections of the Greenland Ice Sheet in response to 20th and 21st century warming may be yet to come.