9317231 Martinson The proposed work is part of an integrated research program ("Anzflux") into the oceanographic structure of upper mixed layer of the eastern Weddell Sea. It is to be carried out from the RVIB Nathaniel B. Palmer in the austral winter of 1994. The work proposed here concerns the collecting of hydrographic and geochemical tracer data to determine the three-dimensional oceanic structure on various spatial scales and to provide data for the validation of oceanic models. The eastern Weddell Sea is a region where a warm regime, defined by the intrusion of warm circumpolar deep water with temperatures near +1 deg C, and a cold regime exist side by side. The cold regime occurs to the west, where deep water is overlain by a thick near- freezing mixed layer. In both regions however enough heat is seasonally carried to the sea ice to melt it completely. The objectives of this project are to allow the reconstruction of the overall configuration of the Weddell Gyre, the warm and cold regimes, and to determine the large-scale baroclinicity, upwelling, and ventilation of intermediate water masses. On a smaller scale this work will characterize the specific differences between the two drift stations and provide initial conditions for modeling the oceanic processes. The tracer measurements will complement the direct observations, and will constrain estimates of the net transfer of warm deep water into the surface layer. These measurements, in conjunction with the other concurrent experiments to quantify the energy brought to the underside of the ice, will form the basis of a regional study of the processes responsible for the relatively thick upper mixed layer and thin ice cover. It is believed that these conditions are only marginally stable, and are maintained by a relatively high upward heat flux, which, if interrupted, could lead to deep vertical convection, and a significant change in the oceanic climate. ***
