Dynamics of North Atlantic western boundary currents
Citable URI
https://hdl.handle.net/1912/8657DOI
10.1575/1912/8657Keyword
Ocean currentsAbstract
The Gulf Stream and Deep Western Boundary Current (DWBC) shape the distribution of
heat and carbon in the North Atlantic, with consequences for global climate. This thesis
employs a combination of theory, observations and models to probe the dynamics of these
two western boundary currents.
First, to diagnose the dynamical balance of the Gulf Stream, a depth-averaged vorticity
budget framework is developed. This framework is applied to observations and a state
estimate in the subtropical North Atlantic. Budget terms indicate a primary balance of vorticity
between wind stress forcing and dissipation, and that the Gulf Stream has a significant
inertial component.
The next chapter weighs in on an ongoing debate over how the deep ocean is filled with
water from high latitude sources. Measurements of the DWBC at Line W, on the continental
slope southeast of New England, reveal water mass changes that are consistent with
changes in the Labrador Sea, one of the sources of deep water thousands of kilometers upstream.
Coherent patterns of change are also found along the path of the DWBC. These
changes are consistent with an advective-diffusive model, which is used to quantify transit
time distributions between the Labrador Sea and Line W. Advection and stirring are both
found to play leading order roles in the propagation of water mass anomalies in the DWBC.
The final study brings the two currents together in a quasi-geostrophic process model,
focusing on the interaction between the Gulf Stream’s northern recirculation gyre and the
continental slope along which the DWBC travels. We demonstrate that the continental
slope restricts the extent of the recirculation gyre and alters its forcing mechanisms. The
recirculation gyre can also merge with the DWBC at depth, and its adjustment is associated
with eddy fluxes that stir the DWBC with the interior. This thesis provides a quantitative
description of the structure of the overturning circulation in the western North Atlantic,
which is an important step towards understanding its role in the climate system.
Description
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy
at the
Massachusetts Institute of Technology
and the
Woods Hole Oceanographic Institution
February 2017
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Suggested Citation
Thesis: Le Bras, Isabela A., "Dynamics of North Atlantic western boundary currents", 2017-02, DOI:10.1575/1912/8657, https://hdl.handle.net/1912/8657Related items
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