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Kevin Trenberth NCAR

Annual cycle of equivalent ocean heat content and ocean heat transport inferred from atmospheric heat budgets. Kevin Trenberth NCAR. F s = H s +LE-R s Q 1 = R T + F s + L(P-E) Q 2 = L(P-E)  .F A = Q 1 -Q 2 = R T + F s = (R T – R s ) + LP +H s.  .F A. H s. LE. R s.

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Kevin Trenberth NCAR

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  1. Annual cycle of equivalent ocean heat content and ocean heat transport inferred from atmospheric heat budgets Kevin Trenberth NCAR

  2. Fs = Hs+LE-Rs • Q1 = RT + Fs + L(P-E) • Q2 = L(P-E) • .FA = Q1-Q2 = RT+ Fs • = (RT – Rs) + LP +Hs .FA Hs LE Rs LP Fs .FO RT

  3. Data • ERBE TOA February 1985-April 1989 • CERES TOA March 2000- December 2004 • WOA01: Ocean heat content: ~1960-2000 • NCEP/NCAR reanalyses 1979-2001 • ERA-40 reanalyses 1979-2001 • Reanalyses sub-sampled for ERBE period. RT OT .FA .FO years x 85-89 ERBE NRA x 79-01+85-89 x 79-01+00-04 WOA01 x 85-89 CERES ERA-40 x 79-01+85-89 x 79-01+00-04

  4. Global ERBE Annual cycle Albedo (green) Radiation Shortwave (red) Longwave (blue) Net (black)

  5. OCEANSAlbedo (green) Radiation Shortwave (red) Longwave (blue) Net (black)

  6. Departures from annual mean: Equivalent ocean heat content (Includes annual cycle in ocean heat transports)

  7. Annual cycle of equivalent ocean heat content Surface flux and inferred ocean heat content

  8. WOA results spotty, often wrong sign in SH Levitus and Antonov 1997

  9. Annual cycle of ocean heat content Inferred divergence of ocean heat transport

  10. Joint EOFs of the ocean heat content and surface fluxes: 1) The ocean heat content annual cycle is larger than for the surface fluxes, due to Ekman transports (winds) that switch sign about 25° lat. 2) The large annual cycle in ocean heat content in the tropics is entirely dynamically induced by winds: reds and blues should balance.

  11. 1 PW=2.8 W m-2

  12. RT based on ERBE 85-89 and CERES 01-04 Atmospheric energy and transports based on NCEP and ERA-40: For ERBE period For 1979-2001 FS and .FO based on 6 possible combinations 1 PW=2.8 W m-2

  13. Surface flux and top 295 m heat content model Atlantic ocean. Boning and Hermann 1994 The annual cycle of heat content is > surface flux: northward transport of heat in summer across 25N.

  14. Seasonal (January - July) overturning circulation for the world ocean; the "Ekman only" part of the Parallel Ocean Climate Model and Ekman approximation. Jayne and Marotzke, 2001

  15. Ocean heat transport at 24°N , Zhang et al 2002 JGR Global Atl Pac 3-mo running averages Northward heat transport Global annual cycle range 1.6 PW? Pacific Min in winter, max in summer, due mainly to Ekman transport (seasonal wind change): enhances annual cycle in heat content in northern oceans.

  16. Conclusions We have not yet been able to balance the heat budget adequately for the mean annual cycle. Implied ocean transports are too big and global integrals do not satisfy physical constraints. TOA radiation and atmospheric divergence of heat do not seem to provide enough scope for obtaining closure. This leaves uncertainties in Ocean Heat Content as the main potential candidate. Some of this may come from not integrating deep enough, especially in tropics? Bring on ARGO!!!

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