Linkage of the Physical Environments in the Northern Antarctic Peninsula Region to the Southern Annular Mode and the Implications for Marine Ecosystem Production

Zhaoru Zhang1, Eileen E Hofmann2, Michael S Dinniman2, Christian Reiss3, Walker O Smith Jr4 and Meng Zhou1, (1)Shanghai Jiao Tong University, School of Oceanography, Shanghai, China, (2)Old Dominion University, Center for Coastal Physical Oceanography, Norfolk, VA, United States, (3)NOAA Southwest Fisheries Science Center, Antarctic Ecosystem Research Division, La Jolla, CA, United States, (4)Virginia Inst Marine Sciences, Gloucester Point, VA, United States
The northern Antarctic Peninsula (NAP) is one of the biogeochemical hotspots in Antarctic marginal seas that supports high levels of primary production and a diverse food web. The productivity of the NAP is significantly modulated by the physical environment, especially vertical stratification, mesoscale circulation, and light availability. In this study, the long-term (almost 20 years) hydrographic and primary production data collected by the U.S. Antarctic Marine Living Resources (AMLR) program during the austral summer near Elephant Island and the South Shetland Islands were combined with satellite observations to assess interannual variability in environmental conditions and production of the NAP. Correlation analyses show that interannual variability of the region is related to the dominant mode of the Southern Hemisphere extratropical climate variability, the Southern Annular Mode (SAM). Post 2000, significant correlations (r>0.5 and p-value<0.1) are found between SAM and environmental properties that potentially affect NAP biological production, particularly mixed layer depth (MLD), the extent of the nutrient-rich Circumpolar Deep Water (CDW), and photosynthetically available radiation (PAR). The relationship of these properties to SAM has spatial variability. Near Elephant Island, interannual variations of the summertime MLD and PAR are significantly and positively correlated to the variation of the summer SAM index. Significant correlations also exist between chlorophyll concentration and summer SAM index, with the SAM-related change in PAR and vertical mixing being the most possible explanation for the association. Near the South Shetland Islands, the correlation between MLD and summer SAM index is weakened. High correlations are found between CDW extent and the spring SAM index as well as the annual SAM index. Significant correlations also exist between chlorophyll concentration and the spring and annual SAM indices. The statistical relationship between chlorophyll concentration and SAM is used with the predicted variation of SAM to make projections of future NAP biological production.