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Antarctic Circumpolar Current

Antarctic Circumpolar Current. Philip Sontag. Thermohaline Circulation; “Mix-Master”. Antarctic Fronts. Convergence Divergence Patterns. Antarctic Circumpolar Curren t. Geostrophic Driven by prevailing westerly winds B alance of surface and bottom stresses

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Antarctic Circumpolar Current

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  1. Antarctic Circumpolar Current Philip Sontag

  2. Thermohaline Circulation; “Mix-Master”

  3. Antarctic Fronts

  4. Convergence Divergence Patterns

  5. Antarctic Circumpolar Current • Geostrophic • Driven by prevailing westerly winds • Balance of surface and bottom stresses • Potential Vorticity and Bottom Topography

  6. Antarctic Polar Ice, Bottom Water Formation (600S) • Penetrative barrier – Albedo – Positive Feedback • Polynas • Origin, Shallow Weddel and Ross Seas • Stability of stratified ocean • Transport to western basin • Decrease CO2 uptake • Driven by Halocline • Melting, formation of ice • Sources: 1) Surface waters -> Continental Shelf 2) Remnants of Circumpolar deep waters

  7. Eddies • 20 km diameter –> jets • Primary mechanism for generating interface displacement • Divergence in Ekman transport • Sheered along flanks of jets

  8. Eddies and Jets, Ocean Storms • Focusing of eddies into narrow jet • ACC -> 2 to 3 narrow jets, sharp fronts • Meridional gradients of potential vorticity (PV) • Strong along Eastward • Weaker along Westward • Eastward and westward flow arise from local PV mixing • “PV staircase” • Merge and split, yet persistent • “Barrier” or “Blender”

  9. Drake Passage

  10. Implications for Primary Production

  11. Melting of Antarctic Shelves

  12. References • Hellmer, H. H., F. Kauker, et al. (2012). Twenty-first-century warming of a large Antarctic ice-shelf cavity by a redirected coastal current. 485: 225-228. • Knauss, J. A., Ed. (1997). Introduction to Physical Oceanography. Long Grove, IL, Waveland Press, Inc. • NASA/MODIS Rapid Response/Jeff Schmaltz. Caption Credit: Rebecca Lindsey, NASA Earth Observatory. http://www.nasa.gov/multimedia/imagegallery/image_feature_1509.html • Orsi, A. H., G. C. Johnson, et al. (1999). Circulation, mixing, and production of Antarctic Bottom Water. 43: 55-109. • Rintoul, S. R. and J. L. Bullister (1999). A late winter hydrographic section from Tasmania to Antarctica. 46: 1417-1454. • Stewart, R. H. (2008). Introduction To Physical Oceanography, Department of Oceanography Texas A & M University. • Thompson, A. F. (2008). The atmospheric ocean: eddies and jets in the Antarctic Circumpolar Current. 366: 4529-4541. • U.S. Geological Survey First published in the Encyclopedia of Earth March 30, 2010; Last revised Date June 11, 2012; Retrieved December 6, 2012 http://www.eoearth.org/article/Antarctic_Convergence?topic=49523

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