Faculty Candidate Seminar - Alison Gray

01/28/2016 - 2:30pm


DATE:  January 28, Thursday, 2:30 p.m.  

LOCATION: Nierenberg Hall 101
SPEAKER:  Alison Gray, Ph.D.
Princeton University 

 Observing the large-scale circulation with autonomous profiling floats: The wind-driven circulation and the Southern Ocean overturning circulation 

 The large-scale circulation of the ocean plays a central role in the global transport of heat, freshwater, carbon, oxygen, nutrients, and other constituents, thereby shaping both global climate and patterns of marine biological production. Observations of large-scale circulation, however, have traditionally been limited in both space and time because of the resource-intensive nature of shipboard measurements and the sheer magnitude of the world’s oceans. The development over the past decades of the Argo array of autonomous profiling floats has now revolutionized our ability to directly observe the large-scale circulation. Here I present analyses of two components of the large-scale circulation, both of which are founded on global absolute geostrophic velocity estimates computed from hydrographic and velocity data provided by the Argo floats. In the first, these estimates are combined with satellite observations of wind stress to assess the extent to which observed geostrophic transports are accurately predicted by Sverdrup balance, a simple but ubiquitous theory of the relationship between wind-forcing and ocean circulation. In the second, a direct circumpolar estimate of the meridional overturning circulation in the Southern Ocean is produced using the gridded velocity fields together with eddy thickness fluxes also estimated from the Argo data. The spatial variability of the overturning and the relative contributions of the mean and eddy components of the flow are both analyzed. Eddies are found to generate significant cross-stream transport of Upper Circumpolar Deep Water that is primarily localized to regions just downstream of major topographic features, consistent with predictions based on analytic and numerical models. In addition, this analysis suggests that the eddy component is associated with the restratification of deep winter mixed layers and the export of mode and intermediate waters. Overall, this work demonstrates that measurements from the Argo array of profiling floats can be used to quantitatively estimate the large-scale circulation of the global ocean with unparalleled spatial and temporal resolution.

Faculty Host:   Dan Rudnick (drudnick@ucsd.edu)
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Nierenberg Hall 101