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Julien Emile-Geay with Mark Cane, Richard Seager, Amy Clement, Naomi Naik and Alexander van Geen Warren revisited : atmospheric freshwater fluxes and “Why.

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Presentation on theme: "Julien Emile-Geay with Mark Cane, Richard Seager, Amy Clement, Naomi Naik and Alexander van Geen Warren revisited : atmospheric freshwater fluxes and “Why."— Presentation transcript:

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

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 S s V BS,S s S WB V WB,S WB SuVu,SuSuVu,Su S WB V N,S WB SsVS,SsSsVS,Ss F=P-E V’S’ Eddy salt fluxes Interior flow : V N –V S ≈ Sverdrup transport Salt transport M S = S WB V N – S s V S Runoff Western Boundary flow S WB ~ 34 psu S u = 34.6 V’S’ H=200m A box model for the nNP (based on Warren 1983) ?

5 Conservations equations : Freshwater budget : Interior flow = V N - V S V WB is computed as a residual Salt budget (southward V WB ) : Eddy salt fluxes Outflow V 0 Interior salt flux M S = S WB V N - S s V S Subtropical inflowUpwelling

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

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

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 the land-sea configuration can explain THC asymmetries

11 Mass balance at the Southern Boundary

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

13 S s V BS,S s S WB V WB,S WB SuVu,SuSuVu,Su S WB V N,S WB SsVS,SsSsVS,Ss F=P-E A box model for the nNP (based on Warren 1983) V’S’ Eddy salt fluxes Interior flow : V N –V S ≈ Sverdrup transport Salt transport M S = S WB V N – S s V S Runoff Western Boundary flow S WB ~ 34 psu S u = 34.6 V’S’ D =200m


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