LGM Seasonal Energetics October, 2009 Slide 2 Annual mean
insolation Reflects Obliquity Change Only (Modern = 23.45 LGM =
22.95) Slide 3 TOA seasonal incoming Insolation Primarily reflects
obliquity (precession change from 102 in modern to 114 in LGM),
biggest high latitude effect in summer Slide 4 Insolation Changes
Solid = Land average, Dotted = Ocean Average Slide 5 Absorbed Solar
Radiation High Latitude summer changes dominate Slide 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 Cant say if this is due to a change in
atmospheric albedo or atmospheric absorption of SW Slide 7 ASR by
components Solid = incoming / Dashed = surface / dotted =
atmosphere Surface albedo chnages in the mid-latitude summer
dominate Slide 8 Surface Changes- Land Ocean Solid = Land Domain /
Dotted = Ocean Domain Slide 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) Slide 10 SURFACE HEAT BUDGET annual mean LGM surface LW
goes up despite lower temperature- must Be because atmos has more
vapor Slide 11 SURFACE HEAT FLUX OCEAN Domain Positive = to the
atmosphere- LGM has smaller seasonal heat flux In both hemispheres
because of more extensive sea-ice- NA is weird Bottom Plot Takes
Into Account Change in Land Frac In LGM Slide 12 SURFACE HEAT FLUX
LAND Domain Positive = to the atmosphere Bottom is an order of
magnitude smaller than ocean Slide 13 FS Change LGM gets more heat
from ocean in NH winter NOT sure abour SH Land changes Slide 14
Where does the LGM atmosphere get additional winter heat from? JFM
FS (colors in W/m^2) and sea Ice concentration MODERN LGM Slide 15
JFM FS change (LGM-MOD) SEA ICE is from LGM Slide 16 JFM FS change-
define regions of interest Composite around regions of large FS
change Where does the energy come from Slide 17 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 Slide 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 Slide 19 Global Mean Energetics Solid = PI (CAM)/ Dashed =
LGM / Dotted = Observations Should we be worried about
model-observation difference? Slide 20 3 Box Surface Temp.
Elevation change in LGM is a potential issue Larger LGM high
latitude seasonal cycle Slide 21 3 Box Atmos Temp. Elevation change
in LGM is a potential issue Slightly Larger LGM high latitude
seasonal cycle Slide 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 Slide 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 Slide 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.
Slide 25 6 box energies- PI (cam) and obs Solid = observations /
dashed = modeled Slide 26 6-box temperatures- TS Slide 27 6-box
temperatures- TV Slide 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 Slide
29 6-box energies- LGM-MOD Slide 30 Land Domain Seasonal Amplitudes
Less LGM ASR cycle- but less energy is exported zonally because
ocean temps. Have a larger seasonal cycle. The energy accumulated
over land doesnt change much Total energy accumulated = MHT, OLR,
and CTEN (quadrature) variability ZHT To land Is out Of phase With
ASR Slide 31 Ocean Domain Seasonal Amplitudes Note- ASR and ZHT are
in phase over ocean Slide 32 Change in non-open ocean Slide 33
Diffusive heat transport Start with zonal mean vertically averaged
temp MOD = RED / LGM =BLUE solid=raw / dashed = trunc. Legendre
exp. Not many zonal mean differences beyond the global mean I
interpolate Below the Topography To make A vertically Integrated
Temp record That isnt biased By topography (I think) Slide 34 Heat
transport divergence MOD = RED / LGM =BLUE solid=raw / dashed =
trunc. Legendre exp. Not many zonal mean differences Slide 35
Legendre Fourier expand temp and MHT_div Slide 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 Slide 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 Slide 38
Reconstruct HT, from T and D D is held constant, from the mod
Wave#2 fit- SH placement is off T is Truncated At wave# 6 Slide 39
Reconstruct HT from T and D Slide 40 MAX HT reconstruct
