HR: 0800h
AN: OS41A-0452    [Abstracts]
TI: Annual cycle of dense water cascading in the north-eastern Barents Sea
AU: * Ivanov, V V
EM: vivanov@iarc.uaf.edu
AF: IARC University of Alaska, 930 Koyukuk Drive, Fairbanks, AK 99775 United States
AU: Shapiro, G I
EM: gshapiro@plymouth.ac.uk
AF: SEOES University of Plymouth, Drake Circus, Plumouth, PL4 8AA United Kingdom
AB: Dense water cascading, which moves cold and/or salty water down the continental slope, is an efficient way of communication between the coastal and the deep ocean. In the Arctic with respect to its extensive shelf waters, annual freeze-thaw cycle and associated salination and freshening the contribution by cascading in ventilation of the deep water masses was always considered to be remarkably high. Despite this fact comprehensive physical descriptions of the Arctic cascades are extremely rare, due to intermittent nature of the process and complexity of launching winter surveys in the darkness of the Polar Night. The present analysis is based on the recently publicized oceanographic archives, containing oceanographic measurements in 1970-1980s, when the Barents Sea was repeatedly sampled by Russian research vessels in the framework of extended field studies of the Arctic Ocean. Piecing together oceanographic observations in various seasons allowed reconstructing the annual cycle of dense water cascading in this area in connection with causative physical processes. Shelf water attains required for cascading potential by the end of December due to topographic control mechanism, which provides faster cooling in the shallow waters. Early winter cascades originate over the shelf of Novaya Zemlya Archipelago (40-60 m depth). They are driven by temperature, although salination caused by ice formation in the coastal zone, its offshore drift and melting in the warm deep water are critical. Throughout the winter vertically homogeneous source water grows saltier and spreads over deeper areas, including isolated banks, thus providing cold and salty cascades. Active ice formation in the north-eastern Barents Sea terminates in the end of April. By this time, newly formed bottom water fills adjacent bottom depressions. However, significant portion of winter-origin water is still accumulated over shoals. The fate of this water mainly depends on the depth of the productive area. If it is deeper than the lower bound of the seasonal pycnocline, cascading is observed throughout summer and fall in the shape of dense plumes gradually sliding down slope. Model estimations give 7 months as a typical time of complete removal of dense water from the Novaya Zemlya Bank (150 m depth) in the course of cascading. This result is confirmed by the late fall survey demonstrating the remnants of a cascading plume near the seabed separated by the warm water from the developing convective cell near the sea surface.
DE: 4207 Arctic and Antarctic oceanography
DE: 4219 Continental shelf processes
DE: 4283 Water masses
DE: 4504 Air/sea interactions (0312)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting