Abstract

Bottom water formation in the Southern Ocean plays an important role in the lower cell of the Meridional Overturning Circulation and in marine biogeochemical cycling, by ventilating and cooling the ocean abyss and sequestering carbon and nutrients there. The lack of adequate observations has to date hindered the quantification of exchanges of mass and physical and biogeochemical tracers between the Weddell gyre and the global ocean. The Antarctic Deep Water Rate of Export (ANDREX) project seeks to determine these exchanges through analysis of the first systematic hydrographic and tracer survey along the gyre’s outer rim. These measurements (including temperature, salinity, nutrients, carbon system parameters, chlorofluorocarbons, sulphur hexafluoride, oxygen isotopes and noble gases) are combined with velocity observations in an inverse model to obtain a self-consistent estimate of the physical and biogeochemical transports across the edge of the Weddell gyre and of the rate at which the deep ocean is ventilated from the region. Of particular interest to the analysis are the quantification of bottom water formation and the density profile of ventilation in the gyre, as well as an assessment of the region’s role in biogeochemical cycling and anthropogenic carbon sequestration. In this presentation, we will discuss the initial results of the box inverse model, focusing on the physical circulation and bottom water formation rates in the Weddell gyre.