14.12.2020: Online Ocean Circulation and Climate Dynamics Colloquium

online 11 am
Webex meeting room: https://geomar.webex.com/geomar/j.php?MTID=m04716ae21ab3b21cf5f146332774032f
Meeting number (access code): 174 650 5874
Meeting password: WTzvkbxr678

Southern Ocean sea ice has been changing, Antarctic glaciers melting, and high-latitude precipitation potentially intensifying over recent decades. All these changes substantially altered the Southern Ocean surface freshwater input, which directly affected the surface ocean salinity. Since salinity is the main driver of the upper ocean stratification in cold polar surface waters, these salinity changes could have affected the vertical exchange of carbon and heat between the deep ocean and the surface. In this talk, I will present observational evidence and model experiments showing that the water column in the open ocean south of the Subantarctic Front is dominated by sea-ice processes and that effects from glacial melt are mostly confined to the coastal ocean. Supporting evidence arises from a new circumpolar dataset of the seawater isotopic composition. Overall, these results highlight the important role of sea ice in driving the water-mass structure in the high-latitude Southern Ocean and its recent changes. These processes are particularly important due to their strong impact on the subsurface heat content that could have influenced the melting of Antarctic ice shelves and the vertical exchange of carbon with the deep ocean.

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