LGM Seasonal Energetics

1. LGM Seasonal Energetics October, 2009

2. Annual mean insolation Reflects Obliquity Change Only (Modern = 23.45 LGM = 22.95)

3. TOA seasonal incoming Insolation Primarily reflects obliquity (precession change from 102 in modern to 114 in LGM), biggest high latitude effect in summer

4. Insolation Changes Solid = Land average, Dotted = Ocean Average

5. Absorbed Solar Radiation High Latitude summer changes dominate

6. ASR by components • Delta_ASR = delta_Incoming + delta_surface_net + delta_atmosphere_net • we have delta_surface_sw– presumably this associated with a surface albedo change • We also have delta incomin • Therefore delta_atmosphere = delta_SW_net_TOA – delta_incoming –delta_surface_sw_net • Can’t say if this is due to a change in atmospheric albedo or atmospheric absorption of SW

7. ASR by components Solid = incoming / Dashed = surface / dotted = atmosphere Surface albedo chnages in the mid-latitude summer dominate

8. Surface Changes- Land Ocean Solid = Land Domain / Dotted = Ocean Domain

9. Atmospheric ASR changes/ Land-Sea Solid = Land /Dotted = Ocean Note; this is atmos contribution to total ASR, not ASR in the atmos Necessarily (could be atmos albedo change)

10. SURFACE HEAT BUDGET annual mean LGM surface LW goes up despite lower temperature- must Be because atmos has more vapor

11. SURFACE HEAT FLUX – OCEAN Domain Bottom Plot Takes Into Account Change in Land Frac In LGM Positive = to the atmosphere- LGM has smaller seasonal heat flux In both hemisphere’s because of more extensive sea-ice- NA is weird

12. SURFACE HEAT FLUX – LAND Domain Positive = to the atmosphere Bottom is an order of magnitude smaller than ocean

13. FS Change LGM gets more heat from ocean in NH winter NOT sure abour SH Land changes

14. Where does the LGM atmosphere get additional winter heat from? MODERN JFM FS (colors in W/m^2) and sea Ice concentration LGM

15. JFM FS change (LGM-MOD) SEA ICE is from LGM

16. JFM FS change- define regionsof interest Composite around regions of large FS change Where does the energy come from

17. Composite FS seasonal cyclesNorth Atlantic Regions Each region changes its annual mean FS- consequence of uncoupled Run? Are there really large ocean heat transport changes

18. North Atlantic Feb. FS and TS Solid = Modern, Dashed = LGM Sea ice edge has large FS gradient, leads to large temp. grad Temp. grad reverses north of Ice edge

19. Global Mean Energetics Solid = PI (CAM)/ Dashed = LGM / Dotted = Observations Should we be worried about model-observation difference?

20. 3 Box Surface Temp. Elevation change in LGM is a potential issue Larger LGM high latitude seasonal cycle

21. 3 Box Atmos Temp. Elevation change in LGM is a potential issue Slightly Larger LGM high latitude seasonal cycle

22. 3-BOX_Energies SOLID = MODERN / DASHED = LGM LGM polar region has less seasonality in ASR (albedo is higher) but Equally large changes in FS

23. 3 BOX energy changes (LGM-MOD) SH has smaller ASR amplitude but even smaller MHT variability, so the OLR and MHT amplitude up NH Summer changes dominate

24. (ASR-FS) is the energy fluxed to the atmosphere. Seasonal cycle ASR goes down in the LGM(enhanced albedo) but so does FS, so the energy fluxed to the atmosphere is unchanged. The partitioning of that energy between OLR and MHT is interesting.

25. 6 box energies- PI (cam) and obs Solid = observations / dashed = modeled

26. 6-box temperatures- TS

27. 6-box temperatures- TV

28. 6-box energies- **SAME LAND MASK** (modern grid boxes with >95% LFRAC) LGM = dashed/ MOD =Solid Less energy into LGM Ocean = more energy into LGM atmos over ocean = larger temp variability over ocean -> less zonal heat transport to the land -> larger seasonal cycle over land

29. 6-box energies- LGM-MOD

30. Land Domain Seasonal Amplitudes ZHT To land Is out Of phase With ASR Less LGM ASR cycle- but less energy is exported zonally because ocean temps. Have a larger seasonal cycle. The energy accumulated over land doesn’t change much Total energy accumulated = MHT, OLR, and CTEN (quadrature) variability

31. Ocean Domain Seasonal Amplitudes Note- ASR and ZHT are in phase over ocean

32. Change in non-open ocean

33. Diffusive heat transportStart with zonal mean vertically averaged temp I interpolate Below the Topography To make A vertically Integrated Temp record That isn’t biased By topography (I think) MOD = RED / LGM =BLUE– solid=raw / dashed = trunc. Legendre exp. Not many zonal mean differences beyond the global mean

34. Heat transport divergence MOD = RED / LGM =BLUE– solid=raw / dashed = trunc. Legendre exp. Not many zonal mean differences

35. Legendre Fourier expand temp and MHT_div

36. LGM –MOD legendre four. Coef.s Stronger annual mean temp. grad. In LGM. Seasonal changes are more Complex; Annual mean heat flux changes also up in LGM

37. Back out D Not all wavenumbers fall on a line of constant D- BUT the #2 in the LGM and MOD do- D/a^2 = .98

38. Reconstruct HT, from T and D T is Truncated At wave# 6 D is held constant, from the mod Wave#2 fit- SH placement is off

39. Reconstruct HT from T and D

40. MAX HT reconstruct