Potential vorticity structure in the North Atlantic western boundary current from underwater glider observations
MetadataShow full item record
KeywordGeographic location/entity; North Atlantic Ocean; Circulation/ Dynamics; Boundary currents; Potential vorticity; Atm/Ocean Structure/ Phenomena; Boundary currents
Potential vorticity structure in two segments of the North Atlantic’s western boundary current is examined using concurrent, high-resolution measurements of hydrography and velocity from gliders. Spray gliders occupied 40 transects across the Loop Current in the Gulf of Mexico and 11 transects across the Gulf Stream downstream of Cape Hatteras. Cross-stream distributions of the Ertel potential vorticity and its components are calculated for each transect under the assumptions that all flow is in the direction of measured vertically averaged currents and that the flow is geostrophic. Mean cross-stream distributions of hydrographic properties, potential vorticity, and alongstream velocity are calculated for both the Loop Current and the detached Gulf Stream in both depth and density coordinates. Differences between these mean transects highlight the downstream changes in western boundary current structure. As the current increases its transport downstream, upper-layer potential vorticity is generally reduced because of the combined effects of increased anticyclonic relative vorticity, reduced stratification, and increased cross-stream density gradients. The only exception is within the 20-km-wide cyclonic flank of the Gulf Stream, where intense cyclonic relative vorticity results in more positive potential vorticity than in the Loop Current. Cross-stream gradients of mean potential vorticity satisfy necessary conditions for both barotropic and baroclinic instability within the western boundary current. Instances of very low or negative potential vorticity, which predispose the flow to various overturning instabilities, are observed in individual transects across both the Loop Current and the Gulf Stream.
Author Posting. © American Meteorological Society, 2016. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 46 (2016): 327–348, doi:10.1175/JPO-D-15-0112.1.
Suggested CitationArticle: Todd, Robert E., Owens, W. Brechner, Rudnick, Daniel L., "Potential vorticity structure in the North Atlantic western boundary current from underwater glider observations", Journal of Physical Oceanography 46 (2016): 327–348, DOI:10.1175/JPO-D-15-0112.1, https://hdl.handle.net/1912/7795
Showing items related by title, author, creator and subject.
Yang, Jiayan; Price, James F. (American Meteorological Society, 2007-09)This paper examines the role of potential vorticity (PV) balance in source- and sink-driven flows between two basins. As shown in previous studies, PV advection into a basin, say a positive PV advection, requires a negative ...
Hall, Melinda M. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1985-02)From October, 1982 to October, 1983 a current meter mooring reaching from the bottom into the thermocline was deployed for the first time in the Gulf Stream at 68°W. The temperatures, pressures, and velocities at the ...
Håvik, Lisbeth; Våge, Kjetil; Pickart, Robert S.; Harden, Benjamin E.; von Appen, Wilken-Jon; Jónsson, Steingrímur; Østerhus, Svein (American Meteorological Society, 2017-10-31)Data from a mooring array deployed north of Denmark Strait from September 2011 to August 2012 are used to investigate the structure and variability of the shelfbreak East Greenland Current (EGC). The shelfbreak EGC is a ...