Spatially Coherent Intraseasonal Velocity Fluctuations on the Western Antarctic Peninsula Shelf. Issue 5 (12th May 2020)

• Record Type: Journal Article
• Authors: McKee, Darren C.; Martinson, Douglas G.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 5(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-05-12
• Subjects: Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2019JC015770
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: We analyze several year‐long moored current meter records collected on the midshelf and shelf break of the western Antarctic Peninsula in order to describe the major features of the intraseasonal circulation. An empirical orthogonal function (EOF) analysis of all current meter records in any given year reveals that over 49% of the circulation variance follows a spatially coherent, nearly depth‐invariant anticyclonic cell in the downstream vicinity of Marguerite Trough, qualitatively consistent with flow‐topography interaction with the canyon. An analysis of kinetic energy spectra supports the interpretation that the shelf break current is diverted shoreward at the location of the canyon and generates substantial counterclockwise energy at periods shorter than ~10 days as the flow is compressed by a downstream bank. The circulation is well correlated with the long‐shore wind stress both local and remote. Composite velocity profiles under upwelling and downwelling winds show that the change in the barotropic current under different wind states is comparable to or larger than the shear of the mean profile in all years. The barotropic velocity fluctuations are generally not coherent with subpycnocline heat content. Plain Language Summary: Owing to scarcity of time series of observations on the western Antarctic Peninsula shelf, it has been difficult to diagnose how the currents below the ocean surface vary on time scales of days to weeks. Here we collect an array of ocean velocity measurements from several point locations across and along the shelf at various depths and study the properties of the currents at each site and how the currents at the different sites covary with each other. We find that over half of the circulation variance is nearly depth independent and is spatially coherent over a scale of several hundred kilometers. The circulation's spatial variability is related to the ocean bathymetry, and its temporal variability is related to the winds, both local and far away. Key Points: We provide the first analysis of intraseasonal circulation variability on the western Antarctic Peninsula shelf based on ocean data The major pattern of circulation variance is nearly barotropic, is wind driven, and is strongly influenced by Marguerite Trough