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NOClim Module A Theory and modelling of the meridional oceanic heat transport Joe LaCasce (met.no) Arne Melsom (met.no) Ole Anders Nøst (NPI) Tore Furevik.

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Presentation on theme: "NOClim Module A Theory and modelling of the meridional oceanic heat transport Joe LaCasce (met.no) Arne Melsom (met.no) Ole Anders Nøst (NPI) Tore Furevik."— Presentation transcript:

1 NOClim Module A Theory and modelling of the meridional oceanic heat transport Joe LaCasce (met.no) Arne Melsom (met.no) Ole Anders Nøst (NPI) Tore Furevik (GfI-UiB) Peter M. Haugan (GfI-UiB) Helge Drange (NERSC/BCCR)

2 Major Objective – Module A To examine the forcing, structure and sensitivity of the Atlantic Meridional Overturning Circulation in response to buoyancy forcing, internal mixing and wind driving, in idealized and realistic basin configurations Task A.1Establish an idealized model to study the AMOC met.no Task A.2Quantify role of applied model resolution met.no Task A.3Examine role of topography NP Task A.4 Assess role of horizontal and vertical mixing parameterisations NERSC

3 ProClim WP 4 – Integration and synthesis 1)Synthesize and quantify the observed and modelled interannual variability of dense water production modes in the entire region of interest 2)Synthesize Meridional Overturning in the North Atlantic – Nordic Seas Helge Drange (NERSC) MICOM and Bergen Climate Model J Even Ø Nilsen, Post Doc (NERSC) Model and data integration on large scale W. Paul Budgell (IMR) ROMS, high resolution coupled atmosphere-ice-ocean model Harald Loeng (IMR) Observational data base, linkages and interpretation Randi Ingvaldsen/Øystein Skagseth Post Doc (IMR) Model and data integration on regional scale

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8 North Atlantic circulation Figure from Fratantoni, (2000) Shallow water on the right Shallow water on the left

9 Anticyclonic flow Ro>>E Ro~E

10 Conclusions The non-linear effects are only important for anti- cyclonic flow (Shallow water on the left). Non-linear effects are import when Ro>E, which is mostly the case in ocean boundary currents. Topographic steering in ocean boundary currents needs shallow water on the right (northern hemisphere) to be effective. This has a strong effect on the path of the Gulf Stream and the North Atlantic circulation. Nøst, O. A., J. Nilsson and J. Nycander: On the asymmetry between cyclonic and anticyclonic flow in a basin with sloping boundaries, JPO, to be subm

11 Stratification-dependent mixing in a coupled GCM controlling sensitivity of mixing to stratification 0.1 Sv freshwater hosing K d prop to N - 

12 Stratification-dependent mixing in a coupled GCM controlling sensitivity of mixing to stratification 0.1 Sv freshwater hosingidealized CO 2 forcing K d prop to N - 

13 Mechanism Feedback between stratification and diffusion: change in diffusivity

14 Mechanism Feedback between stratification and diffusion: change in diffusivity freshwater creates stratification stratification weakens mixing freshwater anomaly gets stronger depends on  no deep convection

15 Marzeion, B., and H. Drange (2006): Diapycnal Mixing in a Conceptual Model of the Atlantic Meridional Overturning Circulation, Deep Sea Research Part II, 53, Marzeion, B., J. Mignot, A. Levermann (2006): The Role of Stratification-dependent Mixing for the Stability of the Atlantic Overturning in a Global Climate Model, Journal of Physical Oceanography, in revision Marzeion, B., J. Mignot, A. Levermann (2006): Stratification-dependent Mixing May Decrease Stability of Atlantic Overturning under Global Warming, Geophys. Res. Lett., to be submitted Dissertation sometime 2006 Publications & PhD status


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