LATE WEICHSELIAN ICEBERG, SURFACE-MELT AND SEDIMENT PRODUCTION FROM THE EURASIAN ICE SHEET: RESULTS FROM NUMERICAL ICE-SHEET MODELLING

Abstract

Results from a numerical ice-sheet model were matched with geological evidence detailing the extent and timing of the Late Weichselian ice sheet in the Eurasian Arctic, through simple adjustments in the model’s environmental inputs. The numerical model predicts the spatial and temporal variation in (1) subglacial sediment transport and deposition, (2) rates of iceberg calving and (3) rates of supraglacial melting over the past 30 000 yr. The ice sheet is characterised by a series of ice streams occupying bathymetric troughs in the Barents Sea and west of Norway, which act as sources for glacial sediment build-up and iceberg production. Our model indicates that significant volumes of sediment are deposited over the Bear Island fan (3000 km3 in 12 000 yr), Franz Victoria Trough fan (500 km3 in 8000 yr) and a series of smaller fans west of Norway (which combine to yield 4000 km3 in 12 000 yr). The Norwegian Channel ice stream operated for only 4000 yr, during which time 400 km3 of sediments were deposited on the adjacent fan. The ice sheet experienced two major periods of iceberg production where the rate of calving increased by ∼50% at about 15 000 and 12 500 yr ago. However, the time-dependent response of iceberg calving to sea-level rise for individual ice streams is shown to be more complicated than the generalised ice-sheet response. The marine portions of the ice sheet decayed after 15 000 yr ago, resulting in several embayments at the mouths of bathymetric troughs. A second pulse of enhanced iceberg calving at 12 500 yr ago caused further decay of the marine ice sheet and the ice margin retreated back to the shorelines of island archipelagos in the northern Barents Sea. Ice loss through surface melting was restricted mostly to the southern margin of the ice sheet.