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Variability in the North Atlantic Deep Western Boundary Current: Upstream Causes and Downstream Effects as Observed at Line W

Beatriz Peña-Molino, Ph.D., 2010
Terry Joyce, Advisor

In this thesis we explored the variability in the DWBC, its connection to the forcing in the northern North Atlantic and interaction with the Gulf Stream.

Using satellite altimetry and Sea Surface Temperature we found that southward shifts of the main axis of the Gulf Stream were preceded by cold temperature anomalies and intensification of the southwestward flow in the Slope Water.

The analysis of 5.5 years of moored CTD and velocity data in the DWBC at 69W for the period 2002-2008, showed that the evolution of potential vorticity (PV) at the mooring site, characterized by a transition from deep to upper Labrador Sea Water (LSW), was similar to that observed in the Labrador Sea 6 to 9 years earlier, and imply spreading rates for the LSW that ranging from 1.5 to 2.5cm/s.

The evolution of the DWBC transport was explored from a 5-element moored array, also at 69W. Larger transports were associated with enhanced presence of recently ventilated upper-LSW and OW. The relative contribution of the different water masses to the circulation was investigated by inverting individual PV anomalies from the observations. We found that changes in the depth-integrated circulation were mostly driven by changes in the OW.