SEA-ICE PROCESSES IN THE LAPTEV SEA AND THEIR IMPORTANCE FOR SEDIMENTEXPORT

Based on remote-sensing data and an expedition during August-September 1993, the importance of the Laptev Sea as a source area for sediment- laden sea ice was studied. Ice-core analysis demonstrated the importan ce of dynamic ice-growth mechanisms as compared to the multi-year cove r of the Arctic Basin. Ice-rafted sediment (IRS) was mostly associated with congealed frazil ice, although evidence for other entrainment me chanisms (anchor ice, entrainment into freshwater ice) was also found. Concentrations of suspended particulate matter (SPM) in patches of di rty ice averaged at 156 g m(-3) (standard deviation sigma = 140 g m(-3 )), with a background concentration of 5 g m(-3). The potential for se diment entrainment over the broad, shallow Laptev Sea shelf during fal l freeze-up was studied through analysis of remote-sensing data and we ather-station records for the period 1979-1994. Freeze-up commences on 26 September (sigma = 7 d) and is completed after 19 days (sigma = 6 d). Meteorological conditions as well as ice extent prior to and durin g freeze-up vary considerably, the open-water area ranging between 107 x 10(3) and 447 x 10(3) km(2). Ice motion and transport of IRS were d erived from satellite imagery and drifting buoys for the period during and after the expedition (mean ice velocities of 0.04 and 0.05 m s(-1 ), respectively). With a best-estimate sediment load of 16 t km(-2) (r anging between 9 and 46 t km(-2)), sediment export from the eastern La ptev Sea amounts to 4 x 10(6) t yr(-1), with extremes of 2 x 10(6) and 11 x 10(6) t yr(-1). Implications for the sediment budget of the Lapt ev shelf, in particular with respect to riverine input of SPM, which m ay be of the same order of magnitude, are discussed. Copyright (C) 199 6 Elsevier Science Ltd.