Forced Transients in Water Mass Transformation and the Meridional Overturning Circulation

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Idealized eddy resolving numerical ocean models will be combined with analytic theory to better understand how the low-frequency ocean thermohaline circulation responds to changes in atmospheric forcing. It is hypothesized that the generation and influences of anomalies in the thermohaline circulation are controlled by the propagation of information along and across geostrophic contours, and that eddy fluxes of heat and salt play a central role in the communication between regions of open and closed contours. The general approach is to use the theory to define the relevant non-dimensional numbers and provide a dynamical framework with which to guide and interpret the numerical model calculations. The numerical model will be used to test the basic predictions from the theory and to incorporate the high latitude convection regions into the large-scale ocean circulation. Quantities of interest include the properties of convective water masses, the meridional (poleward) heat transport, the meridional overturning circulation and ocean circulation anomalies.Intellectual MeritThe combination of analytic models and eddy resolving numerical models will provide a useful complement to more traditional large-scale climate models and very idealized box models that do not resolve essential physical processes. The theoretical underpinning of information propagation along and across geostrophic contours will provide both dynamical understanding of the dominant physical processes and an explicit theoretical estimate of the relevant time scales for the propagation of information and the transition between flow regimes.Broader ImpactsUnderstanding the low-frequency variability of the thermohaline circulation is a central problem in climate science that has direct influence over a wide range of disciplines, including: atmospheric science, biogeochemistry, ecosystems, and carbon uptake. The research results from this project will contribute to both undergraduate and graduate education programs at the Woods Hole Oceanographic Institution. Undergraduate students will be recruited to work on aspects of the analytic model through the Summer Student Fellowship Program, while the Principal Investigator will incorporate results from this program into graduate level classes and lectures at the Geophysical Fluid Dynamics Summer School. Results from this work will also be made broadly available through the peer reviewed literature, national and international meetings and the Principal Investigator's web page.