Geomorphological reconstruction of the Labrador Sector of the Laurentide Ice Sheet

The Labrador sector formed one of three major domes of the Laurentide Ice S heet during the last (Wisconsinan) glaciation. Reconstruction of its evolut ion is important because it modulated atmospheric and oceanic circulation o ver 1-100 ka time scales. This paper reports new geomorphological evidence of ice flow, which is used to reconstruct glimpses of the behaviour of the Labrador Sector during its evolution. mow evidence indicates a southern pos ition (51 degrees N) of the Labrador ice divide, presumed to be the usual l ocation when the ice sheet was close to its maximum extent. A previously in ferred dramatic surge of Labrador ice across Hudson Strait and onto Baffin Island (at 9.9-9.4 ka) is verified. Seemingly contradictory evidence regard ing deglaciation in northern Quebec has been analysed and a reconstruction developed that solves this problem. Deglacial retreat of the Labrador Ice S heet was highly asymmetric with rapid retreat of the southern margin, north wards migration of the centre of mass by 500 km, and slow retreat along the northern margin. As it shrank its thermal regime changed from cold-centred to entirely cold-based and it finally fragmented into many residual ice ca ps and glaciers. This dynamic and asymmetric behaviour may be due to destab ilisation of the Labrador Ice Sheet triggered by Heinrich-event ice streami ng through Hudson Strait. (C) 2000 Elsevier Science Ltd. All rights reserve d.