School of Oceanography Seminar
Research Associate, UW Applied Physics Laboratory
“Local vs. distant controls of dissolved organic carbon in the Southern Ocean”
Wednesday October 11th
Ocean Sciences Building 425
Tea and cookies at 2:15 pm
The global ocean contains a massive reservoir (662±32 Pg C) of dissolved organic carbon (DOC), and its dynamics, particularly in the deepest zones, are not fully understood. DOC in the deep ocean is ubiquitously low in concentration (~35 to 48 umol kg-1) and aged (4000 to 6000 years), persisting for multiple meridional overturning circulations. Deep waters relatively enriched in DOC form in the North Atlantic, migrate to the Southern Ocean to mix with waters from the deep Pacific and Indian Oceans, in turn forming the voluminous deep and bottom waters of the Southern Ocean. Dense shelf water export at the continental shelf break of Antarctica provides an additional localized input of DOC into these deep Southern Ocean waters. Here we seek evidence for local versus distant processes in determining the DOC distributions in the deep Southern Ocean. We assess both the role of large-scale ocean mixing in the Antarctic Circumpolar Current, as well as localized production and export of DOC in the Ross Sea (a highly productive Antarctic Shelf system). In dense shelf waters of the Ross Sea, there is localized enrichment in DOC relative to the source waters off the shelf, primarily due to localized production and mixing into the deeper layers. However, this DOC is remineralized to TCO2 upon export to the deep ocean. We find instead that DOC concentrations and 14C ages in the deep Southern Ocean largely reflect the conservative mixing of the Atlantic, Pacific, and Indian deep waters entering the system from the north.