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

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 Be-10 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 Isbrae, 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. (C) 2012 Elsevier Ltd. All rights reserved.