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Julien Emile-Geay

Warren revisited : atmospheric freshwater fluxes and “Why is no deep water formed in the North Pacific ?”. Julien Emile-Geay. with Mark Cane, Richard Seager, Amy Clement, Naomi Naik and Alexander van Geen. THC. “A notable and well-known asymmetry in the deep ocean circulation

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Julien Emile-Geay

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  1. Warren revisited : atmospheric freshwater fluxes and “Why is no deep water formed in the North Pacific ?” Julien Emile-Geay with Mark Cane, Richard Seager, Amy Clement, Naomi Naik and Alexander van Geen

  2. THC “A notable and well-known asymmetry in the deep ocean circulation is that deep water forms in the North Atlantic, and not at all in the North Pacific” (adapted from Bruce Warren)

  3. What keeps deep water from sinking in the nNP ? Why is the nNP so fresh relative to its Atlantic counterpart?

  4. A box model for the nNP(based on Warren 1983) F=P-E VBS,Ss Runoff Vu,Su ? H=200m Western Boundary flow V’S’ VN,SWB VS,Ss VWB,SWB V’S’ Eddy salt fluxes Interior flow : VN –VS ≈ Sverdrup transport Salt transport MS= SWBVN – SsVS SWB ~ 34 psu Su = 34.6

  5. Conservations equations : • Freshwater budget : Interior flow = VN - VS VWB is computed as a residual • Salt budget (southward VWB) : Interior salt flux MS = SWBVN - SsVS Outflow V0 Upwelling Subtropical inflow Eddy salt fluxes

  6. Results and sensitivity analysis

  7. Seasonal freshwater budget • Solid line : • nNP • Dash-dotted : • nNA • Thin solid : • nNP-nNA Why is the nNP so rainy despite its low evaporation rate?

  8. Moisture is picked from the Warm Pool and converged into the nNP WINTER

  9. Most of the northward moisture transport is associated with the Asian Monsoon SUMMER

  10. Conclusions • Warren was essentially right : small throughflow rate and • large (P-E) make the nNP so fresh • But it’s P, not E : Large atmospheric moisture transports, especially the Asian Monsoon, seem to explain this • excess (in NCEP at least). • Why this is not happening in the North Atlantic : • different land/sea configuration (weaker Monsoon) • skinnier basin • Ultimately, the asymmetries of theland-sea configuration can explainTHC asymmetries

  11. Mass balance at the Southern Boundary

  12. Warren’s box model (1983) CONFUSING : Julien Emile-Geay: Julien Emile-Geay: Freshwater fluxes : + Eddy Transports .. • F=P-E • R

  13. A box model for the nNP(based on Warren 1983) F=P-E VBS,Ss Runoff VWB,SWB Vu,Su Western Boundary flow V’S’ VN,SWB D =200m VS,Ss V’S’ Eddy salt fluxes Interior flow : VN –VS ≈ Sverdrup transport Salt transport MS= SWBVN – SsVS SWB ~ 34 psu Su = 34.6

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