East Greenland Ice Sheet retreat history during the last deglaciation

Abstract. The lack of geological constraints on past ice-sheet change in marine-based sectors of the Greenland Ice Sheet (GrIS) following the Last Glacial Maximum limits our ability to assess (1) the drivers of ice-sheet change, and (2) the performance of ice-sheet models that are benchmarked against the paleo-record of GrIS change. Here, we provide new in situ ¹⁰Be surface exposure chronologies of ice-sheet margin retreat from the outer Scoresby Sund and Storstrømmen Glacier regions in eastern and northeastern Greenland, respectively. Ice retreated from Rathbone Island, east of Scoresby Sund, by ~14.1 ka, recording some of the earliest documentations of terrestrial deglaciation in Greenland. The mouth of Scoresby Sund deglaciated by ~13.2 ka, and retreated at an average rate of ~43 m/yr between 13.2 ka and 9.7 ka. Storstrømmen Glacier retreated from the outer coast to within ~3 km of the modern ice margin between ~12.7 ka and 8.6 ka at an average rate of ~28 m/yr. Retreat then slowed or reached a stillstand as ice retreated ~3 km between ~8.6 ka to the modern ice margin at ~8.0 ka. These retreat rates are consistent with late glacial and Holocene estimates for marine-terminating outlet glaciers across East Greenland, and comparable to modern retreat rates observed at the largest ice streams in northeastern, and northwestern Greenland.