Dynamics of Basin-Scale Arctic Ocean Circulation

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The dynamics of large-scale ocean circulation in the Arctic must be very different from that in any lower-latitude ocean basin since the two processes that constitute the leading order dynamics of a basin-scale circulation, i.e., (1) the Sverdrup flow driven by Ekman pumping/sucking and (2) a western boundary layer current that closes the gyre circulation and dissipates the vorticity flux from wind stress, cannot apply to the Arctic Ocean. This is due to the fact that (= df/dy where f is the Coriolis parameter) is nearly zero and to the lack of a western boundary in the Arctic Ocean. Despite the rapid development of modeling capability, a basic understanding of the dynamics that govern the basin scale ocean circulation and its variability in the Arctic has yet to be developed. Funds are provided to address this issue using process-oriented models. The project objectives are to understand (1) which processes balance the surface forcing in the ocean interior; (2) how and where the vorticity flux from the curl of surface stress is dissipated so that a quasi-steady circulation can be maintained; (3) how the Arctic Ocean responds to changes in the forcing field in an environment where planetary Rossby waves are stagnant due to approaching zero; (4) the role of boundary currents in establishing the basin-scale circulation; and (5) the effects of bottom topography. Both wind-driven and thermohaline circulation will be studied. The PI plans to use the simplest possible, yet adequate, models to address each of these issues. The results, however, will be tested in Ocean General Circulation Models (OGCMs) through collaboration with a major Arctic Ocean modeling consortium. The PI and Dr. A. Proshutinsky (also at WHOI), who leads the Arctic Ocean Model intercomparison Project (AOMIP), which focuses on the development of 3-D OGCMs, have agreed to work closely for testing the results from this process-oriented study in various OGCMs that AOMIP is currently running. The results of a successful project will help guide development, interpretation, and verification of predictive models of Arctic Ocean circulation. Such models are necessary for the prediction of climate change and pollutant transport pathways, amongst other applications.