Heat transport during the Last Glacial Maximum in PMIP2 models

1. Heat transport during the Last Glacial Maximum in PMIP2 models January 2012 With Shih-Yu Lee

2. PMIP2 Models • CNRM T63 L45 • IAP FGOALS T42 L26 • HadCM3 2.5%3.8 L19 • IPSL 2.5X3.75 L19 • Micro3.2 (medres) T42 L20 • CCSM T42 – lower resolution than the CMIP3 (I’m missing E and P fields) • MPI ECHAM 5 (lower resolution– I don’t have a PI run at the same resolution – Don’t use here)

3. Planetary albedo change and partition

4. Planetary albedo partitioning? Reflected by Atmosphere Solar Incident Reflected by Surface Atmosphere Earth’s Surface

5. Surface albedo and planetary

6. Calculating MHT (annual average) • Total MHT is (ASR-OLR) integrated over the polar cap to the latitude where the flux is calculated (the global mean of ASR-OLR is removed so that there is no heat transport through the poles) • The ocean heat transport (OHT) is the surface heat flux integrated over the polar cap (global average removed) • Atmospheric heat transport (AHT) is the residual: AHT = MHT –OHT • Atmos. Moist heat transport is L(P-E) integrated over the polar cap (with a global average adjustment) • Atmos. Dry heat transport is the residual: Atmos. Dry=AHT –Atmos. Moist • We’d like to do the stationary, mean overturning and, transient decomposition as well

7. The LGM-PI difference in total (Ocean + Atmos) meridional heat transport is smaller than the inter-model spread

8. Ensemble average MHT change Solid line is the ensemble average. Shading is 1 sigma. The change in heat transports are not significantly different from 0 (the cross-equatorial change is)

9. Understanding MHT change 5.8 PW ASR* OLR* 8.2 PW 2.4 PW - Heat Transport =

10. ΔMHT = ΔASR* - ΔOLR* ΔMHT = ΔASR* - ΔOLR* NH SH +0.1 PW = +0.8 PW - 0.7PW -0.05 PW = -0.04 PW - 0.01 PW means ΔASR* = ΔMHT + ΔOLR* (regress against ΔASR* spread) NH SH • = 0.44 + 0.56 • 1 = 0.45 + 0.55 Dominant balance is between ASR* and OLR* ! slopes

11. The surface and atmospheric reflection contributions to ASR* What determines ΔASR*?Reminder: partitioning in modern climate.

12. ASR* change (surface and atmos. Components) ΔASR* = ΔASR*SURF + ΔASR*CLOUD + incident NH SH +0.8 PW = +1.12 PW - 0.37PW + 0.05PW -0.04 PW = +0.15 PW - 0.18 PW - 0.01 PW means ΔASR* = ΔASR*SURF + ΔASR*CLOUD + incident NH SH • = 0.22 + 0.77 + 0.01 • 1 = 0.66 + 0.38 -0.04 slopes Ensemble mean ΔASR* is due to surface albedo change. Spread in the NH is due to cloud response differences.

13. Ensemble average MHT change Solid line is the ensemble average. Shading is 1 sigma. The change in heat transports are not significantly different from 0 (the cross-equatorial change is)

14. MHT change and ocean/atmos contributions ΔMHT = ΔAHT + ΔOHT NH SH +0.1 PW = +0.24 PW - 0.14PW -0.04 PW = 0.0 PW - 0.04 PW means ΔMHT = ΔAHT + ΔOHT (regress vs. MHT) NH SH • = 0.20 + 0.80 • 1 = 0.75 + 0.25 slopes Ocean atmos. Compensation R^2 is 0.40 in the NH and 0.70 in SH

15. Ensemble average AHT change Solid line is the ensemble average. Shading is 1 sigma. The trade off between moist and dry AHT is robust across models (moisture transport goes down in the LGM). At the equator the changes are consistent with Northward cross equatorial heat transport by the Hadley cell (with the moisture transport opposing the net heat transport)

16. AHT change and moist/dry contributions AHT #s are different cause CCSM is excluded here ΔAHT = Δdry + Δmoist NH SH +0.1 PW = +0.27 PW - 0.17PW -0.1 PW = 0.14 PW - 0.24 PW means ΔMHT = Δdry + Δmoist (regress vs. AHT) NH SH • = 1.16 - 0.16 • 1 = 0.60 + 0.40 slopes

17. Cross equatorial heat transport • Cross equatorial MHT (atmos + ocean) is half the hemispheric difference in ASR (SH – NH) – the hemispheric difference in OLR (SH-NH) • MHTEQ= (ASRSH - ASRNH )/2 - (OLRSH - OLRNH )/2 • MHTEQ = <ASR> - <OLR> <ASR> <ASR> <OLR> <OLR> MHTEQ SH NH

18. ΔMHTeq , Δ<ASR> and, Δ<OLR> Robust increase in cross equatorial total heat transport due to <ASR> change

19. MHTEQ, AHTEQ and OHTEQ

20. ITCZ change

21. ITCZ intensity change and AHTEQ

22. Change in Annual mean surface temp Colors are the ensemble mean change Contours are the inter-model spread with contour interval 2k

23. Precipitation change Contours are precipitation in the PI climatology

24. Seasonal precipitation changes

25. Seasonal Cycle of Surface Temp. Contours are inter-model spread with contour interval 2K

26. Seasonal Heating

27. Seasonal Heating Climatology

28. LGM change in seasonal heating Less water vapor and more topography (thinner atmosphere) leads to less Shortwave atmospheric absorption

29. Change in seasonal surface fluxes More sea ice insulates the system from the heat capacity of the ocean leading To larger seasonal energy fluxes to the atmosphere Land ice has high albedo -> less seasonal energy input to the atmosphere

30. Seasonal surface flux changeand ice change

31. Zonal average change in seasonal heating

32. Change in seasonal amplitude of temperature

33. EXTRAS

34. MHT and partition change in each model

35. Same data- grouped by circulation classes The only robust changes across the models is the decreased moist transport and increased dry transport

36. Does the change in ocean heat transport predict the change in AHT?

40. Climatological seasonal amplitude of temperature