Meeting Abstracts

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Fates and transformation of Denmark Strait Overflow Water revealed by Lagrangian particles in a high resolution ocean model

Inga Koszalka, Thomas W. N. Haine, Marcello G. Magaldi
Johns Hopkins University, Earth and Planetary Sciences, Baltimore, United States
(Abstract received 03/13/2012 for session A)
ABSTRACT

The Denmark Strait Overflow Water (DSOW) accounts for one third of the North Atlantic Deep Water and is a key component of the global thermohaline circulation. The understanding of the pathways of DSOW downstream of Denmark Strait and its evolution in the water-mass property space during the transfer through the Irminger Basin is still incomplete, however, due to spatio-temporal variability of the flow and the sparsity of observations.

This study employs synthetic Lagrangian particles deployed at Denmark Strait in a high resolution ocean model to study the transit of dense waters through the Iriminger Basin. The Lagrangian framework is ideal for addressing the fate and transformation of DSOW because the water masses are defined on water particle trajectories. The floats are integrated using velocity fields every 15mins from a 2km resolution simulation with 210 vertical levels for a total period of two months in summer 2003.

The floats deployed in dense boluses at the Denmark Strait Sill (66.1N) make a fast transit through the Irminger basin, reaching the Angmagssalik mooring line (63.5N) within 2 weeks on average. The floats deployed in the dense waters in the Kangerdlugssuaq Trough, and adjacent shelf on the western side of the Denmark Strait, follow an alternative southward route on the continental shelf. These floats constitute over 40% of the floats that reach Angmagssalik within two months. These results challenge the traditional idea that DSOW originates solely from the Denmark Strait sill. We calculate the water mass property transformation rates following the floats and classify the deep water masses in T-S-density space using hierarchical clustering methods. We thereby map spatial distributions of eddy diffusivity and eddy fluxes to quantify the effect of eddies in the mixing and transformation processes affecting DSOW.