GC116-0006
Supercool Southern Ocean Waters from Sinking Plumes and Ice-Shelf Melting

Wednesday, 16 December 2020
Poster
Alexander Haumann1, Ruth Moorman2, Stephen Riser3, Annie P S Wong3, Lars Henrik Smedsrud4, Ted Maksym5, Earle Wilson6, Robert Drucker3, Lynne D Talley7, Kenneth S Johnson8, Robert M Key1 and Jorge L Sarmiento1, (1)Princeton University, Atmospheric and Oceanic Sciences Program, Princeton, NJ, United States, (2)Princeton University, Atmospheric and Oceanic Sciences Program, Princeton, United States, (3)University of Washington, School of Oceanography, Seattle, WA, United States, (4)Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway, (5)Woods Hole Oceanographic Inst, Woods Hole, MA, United States, (6)California Institute of Technology, Earth Science and Engineering, Pasadena, CA, United States, (7)University of California San Diego, La Jolla, CA, United States, (8)Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States
Abstract:
In cold polar waters, temperatures sometimes drop below the freezing point, which is referred to as supercooling. However, observational challenges in this region limit our understanding of the spatial and temporal extent of this phenomenon. We here provide observational evidence that supercooled waters are much more widespread in the seasonally ice-covered Southern Ocean than previously thought. In 5.7% (+4.6%) of all analyzed hydrographic profiles south of 55° S we find temperatures below the surface freezing point (potential supercooling) and in 2.5% (+3.4%) of all cases the temperature is below the local freezing point (in-situ supercooling). We attribute deep coastal ocean supercooling to melting ice shelves, and surface-induced supercooling that occurs in the entire seasonal sea-ice region to sea-ice formation. The latter mechanism provides evidence for deep-reaching convective plumes down to the permanent pycnocline—a potentially important mechanism for the vertical tracer transport and water-mass structure in the polar ocean.
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