WedUP: Weddell Gyre Upwelling and dynamical Processes

• Applicant: Dr. Krissy Reeve
• Subject Area: Oceanography
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 424330345

The Weddell Gyre supplies heat towards the Antarctic ice shelves and regulates the density of water masses that feed the deepest limb of the global overturning circulation. It is therefore a fundamental component in the global climate system. However, little is understood about how the Weddell Gyre might respond to long-term changes in atmospheric forcing. The upwelling component plays an important role in the climate system, by modifying source water masses through heat loss and freshwater input by sea-ice melt. However, while increasing nutrient and salinity trends are indicative of increased upwelling, a reduction in the uptake of anthropogenic carbon may be indicative of reduced upwelling over the same time period. In addition to upwelling, the role of turbulent eddy diffusion of heat is poorly established yet potentially important, since it may be a driving mechanism of removing heat from the southern limb of the gyre towards the central gyre interior where upwelling is likely to take place, and also towards the coastal ice shelves surrounding Antarctica, where the flux of heat can lead to basal ice melt and subsequently sea level rise. My previous work has shown, that Maud Rise appears to perturb the heat budget, yet so far the critical processes have been poorly resolved in observational analysis. The importance of Maud Rise towards the heat budget is paramount, in light of the recent return of the Weddell Polynya in 2017 after four decades of absence, directly over Maud Rise. The aim of WedUP is to determine the long-term, large-scale changes to the Weddell Gyre circulation and upwelling, and the role this may play in the ocean heat budget. Improved estimates of eddy-diffusivities which vary spatially and seasonally will provide an assessment on the contribution of eddy-processes in redistributing heat towards the gyre interior and towards the ice shelves. Lastly, a case study will be implemented, pulling together all previous information, to establish the role of the oceans in the development of the 2017 Weddell Polynya.WedUP will take advantage of the extensive collection of Argo float data that has provided full coverage of the Weddell Gyre since 2002, which includes under the sea-ice during the winter period. The Argo float data will be combined with seal-borne, vessel-based and mooring-based measurements to look at the spatial and temporal variation of salinity and stratification in the upper Weddell Gyre. Trends in nutrient concentration, sub-surface salinity, and radionuclide activity will provide a means of inferring changes in the rate of upwelling within the gyre interior.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1158: Infrastructure area - Antarctic Research with Comparative Investigations in Arctic Sea Ice Areas
• International Connection: Norway
• Cooperation Partners: Olaf Boebel, Ph.D.; Walter Geibert, Ph.D.; Tore Hattermann, Ph.D.; Mario Hoppema, Ph.D.; Professor Torsten Kanzow, Ph.D.