On the Revealing Firsthand Probing of Ocean-Ice-Atmosphere Interactions off Sabrina Coast During NBP1402

Tuesday, 16 December 2014: 4:15 PM
Alejandro Hector Orsi1, Natalie Jane Zielinski1, William Joseph Durkin IV2, Paul Clark1, Christina L Wiederwohl1, Mark Andrew Rosenberg3, Bruce A Huber4, David Gwyther5, Jamin Stevens Greenbaum6, Caroline Lavoie7, Amelia Shevenell8, Amy Leventer9, Donald D Blankenship6, Sean P S Gulick6 and Eugene W Domack8, (1)Texas A & M University, College Station, TX, United States, (2)Cornell University, Ithaca, NY, United States, (3)Antarctic Cooperative Research Centre, CSIRO, Hobart, Australia, (4)Lamont-Doherty Earth Obs, Palisades, NY, United States, (5)University of Tasmania, Austin, TX, United States, (6)University of Texas, Institute for Geophysics, Austin, TX, United States, (7)University of Aveiro, Aveiro, Portugal, (8)University of South Florida St. Petersburg, St Petersburg, FL, United States, (9)Colgate University, Geology, Hamilton, NY, United States
Diverse interactions of winds, currents and ice around Antarctica dictate how, where and when the world’s densest waters form and massive floating ice shelves and glaciers melt, as well as control sea surface gas exchange and primary productivity. Compelled by recent rate estimates of East Antarctic Ice Sheet mass loss, we contrast the paths and mixing histories of oceanic waters reaching the continental ice edge off the Sabrina and Adelie coasts relying on the unique set of synoptic shipboard measurements from NBP1402 (swath bathymetry, ADCP, underway CTD).

Analysis of historical hydrography and sea ice concentration fields within the Mertz Polynya indicates the apparent effect of evolving ocean-ice-atmosphere interactions on the characteristics of local Shelf Water (SW) sources to current outflow of newly formed Antarctic Bottom Water (AABW). A polynya dominated water mass structure similar to that observed off the Adelie Coast before the removal of the Mertz Ice Tongue was expected to the west of the Dalton Ice Tongue (DIT). However, we found no evidence of dense SW off Sabrina Coast, which may lessen the region’s preconceived influence to global meridional overturning.

Present sea ice production within the eastern Dalton Polynya is overshadowed by freshwater input to relatively stable interior upper waters. The Antarctic Coastal Current (ACoC) picks up distinct meltwater contributions along the DIT western flank and in front of the Moscow University Ice Shelf (MUIS) and Totten Glacier (TG). Unlike over other highly influential margins to global sea level rise, there is no evidence of local cross-shelf inflow and mixing of warm Circumpolar Deep Water. Relatively cold thermocline waters from the continental slope enter the eastern trough off Sabrina Coast, and they are swiftly steered poleward by complex underlying topography. Meltwater export from beneath the MUIS and TG is observed at newly discovered trenches that effectively constrain sub-cavity inflow to low salinity near-freezing waters drawn from intermediate levels of the adjacent westward flowing ACoC.

Winds, currents and ice interactions observed off Sabrina Coast during NBP1402 are most likely widespread, in view of reported decadal freshening of upper waters over the Antarctic continental shelf and their localized AABW outflows.