The acc and Primary production in the southern ocean James Fiorendino

Antarctic Circumpolar Current (ACC) Driven by westerly winds Isotherms and Isohalines contribute to eastward flow 3 – 9 cms-1 300 m above bottom in Drake Passage Bottom topography results in curvature of current due to conservation of potential vorticity

Antarctic Fronts 3 major fronts: Subtropical, polar, Southern (Antarctic Divergence) Antarctic polar front (convergence) occurs at ~55° S and forms northern boundary of acc Polar easterlies drive westward current close to the continent Coriolis results in divergence Fronts Account for 75% of transport by ACC

Antarctic convergence and divergence North Atlantic deep water upwells at the Antarctic divergence Upwelled water is high in nutrients, influences biology Antarctic surface water sinks beneath warmer subantarctic water, becomes Antarctic intermediate water

Primary production in the southern ocean Southern ocean is a high- nutrient low-chlorophyll area Iron limits phytoplankton growth Primary production is highest at fronts, coastal/shelf regions, and areas of ice retreat

Primary production in the southern ocean Interaction of current with topography results in mixing at fronts Cross-frontal mixing may provide limiting nutrients Coastal regions and islands are a source of iron Melting stabilizes water layer and release nutrients collected from the air

Sources Knauss, J.A. 2005. Introduction to Physical Oceanography. Waveland Press, Inc. Long Grove, IL. Moore, J.K. and M.R. Abbott. 2000. Phytoplankton chlorophyll distributions and primary production in the Southern Ocean. Journal of Geophysical Research, 105: 28,709 – 28,722 Klinck, L. and Nowlin, W.D. Jr. 2001. Southern Ocean-Antarctic Circumpolar Current. In: Encyclopedia of Oceanography. Academic Press. Raymont, J.E.G. 1980. Plankton and Productivity in the Oceans 2nd Edition, Vol. 1. Pergamon Press. Elmsford, NY. Moore, J.K., Abbott, M.R., and J.G. Richman. 1999. Location and dynamics of the Antarctic Polar Front from satellite sea surface temperature data. Journal of Geophysical Research 104: 3059 – 3073.