THE DEGLACIAL AND RELATIVE SEA-LEVEL HISTORY OF DISKO BUGT AND THE JAKOBSHAVNS ISBRAE ICE STREAM, WEST GREENLAND

New relative sea-level (RSL) data from Disko Bugt, a large marine embayment in west Greenland, are used to examine the deglacial history of the Jakobshavns Isbrae ice stream. RSL data show rapid deglaciation from the outer part of the bay after 10.3 ka cal. yr BP. Following initial rapid retreat, ice stream recession slowed as it approached the eastern shores of the bay. Sea bed elevations increase here and the ice stream terminus lingered for several thousand years before retreating into the narrow bedrock-confined Jakobshavns Isfjord.

The focus of this paper is the timing of ice stream retreat into the Jakobshavns Isfjord. A prominent moraine at the mouth of the Jakobshavns Isfjord c. 200-300 m asl marks the initial location of the ice stream terminus. RSL data from a staircase of isolation basins c. 5 km inland of this moraine are used to determine the timing of deglaciation, the elevation of the local marine limit (c. 40 m asl), as well as the rate and form of RSL change since deglaciation. Lakes from above the local marine limit, up to an elevation of 275 m asl, provide further information on the relative dynamics of the ice stream and the ice sheet in this region.

RSL data from an isolation basin with a submerged sill c. –4m asl record convincing evidence for a significant late Holocene RSL rise since c. 3 ka cal. yr BP. This is compared with other records of late Holocene RSL change from within the bay to examine whether it reflects forebulge collapse following the retreat of the Greenland and Laurentide Ice Sheets, or renewed crustal loading caused by a significant readvance of the Greenland Ice Sheet in the late Holocene, from c. 4-5ka cal. yr BP onwards.

Long, A.J. & Roberts, D.H. Late Weichselian deglacial history of Disko Bugt, West Greenland, and the dynamics of the Jakobshavns Isbrae ice stream. Boreas. In press. Long, A.J. & Roberts, D.H. 2002. A revised chronology for the ‘Fjord Stade’ moraine in Disko Bugt, West Greenland. Journal of Quaternary Science, 17, 561-579. Long, A.J., Roberts, D.H. & Wright, M. 1999. Isolation basin stratigraphy and Holocene relative sea-level change on Arveprinsen Ejland, Disko Bugt, West Greenland. Journal of Quaternary Science, 14, 323-345.