LGM Seasonal Energetics October, 2009

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

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

Insolation Changes Solid = Land average, Dotted = Ocean Average

Absorbed Solar Radiation High Latitude summer changes dominate

ASR by components ASR = Incoming_SW – outgoing_SW Outgoing = what never makes it surface + reflected by surface + residual What never makes it to surface = downwelling_TOA – downwelling_Surf---- this could be absorbed or reflected but lets assume it’s reflected by atmos reflected by surface = upwelling_Surf Res = up_TOA - what never makes it surface – upwelling surface The residual includes the absorbed (and scattered) downwelling and the upwelling radiation that is absorbed, reflected in the atmos (res = approx. 20% incoming, fairly spatially uniform)

ASR by components- all signs are gain to atmosphere Solid = incoming / Dashed = surface / dotted = atmosphere Dashed dot are residual (small)

ASR by components- all signs are gain to atmosphere Solid = NET (all terms) / Dashed = surface albedo / dotted = atmosphere Large but not total compensation between the atmos and surface

What never makes it to surface (atmos) by components Total = downwelling_TOA – downwelling_Surf Clear = downwelling_TOA –down_SURF_clear Cloudy = down_SURF_clear – down_Surf

Atmosphere’s effect on ASR change Signs are defined such that positive mean atmos gains LGM - MOD

More clouds = more reflection July LGM – MOD Cloud liquid water (vert. Int. in kg) change July- LGM - MOD Change in radiation REFLECTED (+ = more LGM up) SW

More clouds = more reflection JAN LGM – MOD Cloud liquid water (vert. Int. in kg) change JAN- LGM - MOD Change in radiation REFLECTED (+ = more LGM up) SW Cloud changes could be multiplied by incoming solar to try And tease out the change in reflected--- if we care

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

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)

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

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

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

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

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

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

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

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

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

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

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

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

3 box temp- amplitudes Seasonal Temp. Amplitude

3-BOX_Energies SOLID = MODERN / DASHED = LGM / Dotted = 4 X co2 LGM polar region has less seasonality in ASR (albedo is higher) but Equally large changes in FS

3 BOX energy changes (LGM/quad-PI) LGM – PI Is SOLID Quad – PI Is dashed SH has smaller ASR amplitude but even smaller MHT variability, so the OLR and MHT amplitude up NH Summer changes dominate

3 box seasonal amplitudes (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.

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

6-box temperatures- TS

6-box temperatures- TV

6 box temp amplitudes

6-box energies- **SAME LAND MASK** (modern grid boxes with >95% LFRAC) Solid =PI Dashed = LGM Dotted = quad 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

6-box energies- LGM/quad-PI

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

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

Change in non-open ocean

Diffusive heat transport Start 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

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

Legendre Fourier expand temp and MHT_div

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

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

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

Reconstruct HT from T and D

MAX HT reconstruct

B_mht from 3 box models - TV B_MHT values are 3 +/- .4 (2 sigma) and 2 +/-.1 for NH and SH We used 3.4 in EBM; R^2 are .86 and .89 for NH and SH

B_mht from 3 box models -TS B_MHT values vary widely between models- however R^2 values are Slightly better and = .87 and .91 for NH and SH

B_olr from 3 box model Asterisk =NH Square = SH Solid = NH Linear Dashed = SH