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Projects > A - C > ANSLOPE

Preferred term

ANSLOPE  

Definition

  • AnSlope seeks an answer to the question: What is the role of the Antarctic Slope Front and continental slope morphology in the exchanges of mass, heat, and freshwater between the shelf and oceanic regimes, in particular those leading to outflows of dense water into intermediate and deep layers of the adjacent deep basins and world ocean circulation? The importance to the global ocean circulation and climate of cold water masses originating in the Antarctic is now understood, but the processes by which these water masses enter the deep ocean circulation are not. We have developed a program called AnSlope to address this problem. Our primary goal is to identify the principal physical processes that govern the transfer of shelf-modified dense water into intermediate and deep layers of the adjacent deep ocean. At the same time, we seek to understand the compensatory poleward flow of waters from the oceanic regime. We identify the upper continental slope as the critical gateway for the exchange of shelf and deep ocean waters. Here the topography, velocity and density fields associated with the nearly ubiquitous Antarctic Slope Front (ASF) must strongly influence the advective and turbulent transfer of water properties between the shelf and oceanic regimes. AnSlope has four specific objectives: [A] Determine the ASF mean structure and the principal scales of variability (spatial from ~1 km to ~100 km, and temporal from tidal to seasonal), and estimate the role of the Front on cross-slope exchanges and mixing of adjacent water masses; [B] Determine the influence of slope topography (canyons, proximity to a continental boundary, isobath divergence/convergence) on frontal location and outflow of dense Shelf Water; [C] Establish the role of frontal instabilities, benthic boundary layer transports, tides and other oscillatory processes on cross-slope advection and fluxes; and [D] Assess the effect of diapycnal mixing (shear-driven and double-diffusive), lateral mixing identified through intrusions, and nonlinearities in the equation of state (thermobaricity and cabbeling) on the rate of descent and fate of outflowing, near-freezing Shelf Water. AnSlope addresses these objectives with an integrated observational and modeling program structured as follows. A collaborative core program begins in 2002, containing the components considered central to meeting AnSlope objectives, primarily through acquisition of a set of measurements focused over the outer continental shelf and upper slope of the northwestern Ross Sea. This will allow us to assess the regional AABW production rate, and to identify the cross-front exchange processes that must be taken into account when assessing provision of dense water to the deep basins elsewhere around Antarctica. The core elements are: moorings; CTD/LADCP and CTD-based microstructure; tracers; and basic tidal modeling. "Enhancement" proposals, to be submitted separately, request support for the modeling studies that are necessary to fully exploit the measurements and develop the techniques for parameterizing cross-front exchanges in regional and global models. Three cruises are proposed, beginning in Austral summer 2003, over a period of 12 to 14 months. Moorings would be in place throughout this period. The Italian CLIMA program in the Ross Sea provides a valuable international enhancement for the AnSlope observational component. The German BRIOS-2 coupled ice-ocean GCM program is complementary to the US process-oriented modeling studies, and provides a test-bed for AnSlope-generated parameterizations of cross-front exchange. Additional information can be found at "http://www.ldeo.columbia.edu/res/div/ocp/projects/anslope.shtml" (en)

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https://gcmd.earthdata.nasa.gov/kms/concept/2e61366f-04e7-44c2-8d0f-ad44783eccdc

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