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

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)

Planetary albedo change and partition

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

Surface albedo and planetary

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

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

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)

Understanding MHT change 5.8 PW ASR* OLR* NH = 8.2 - 2.4 = 5.8 SH = 9.0 – 3.2 = 5.8 8.2 PW 2.4 PW - Heat Transport =

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 Δ ASR* spread) NH SH = 0.44 + 0.56 1 = 0.45 + 0.55 Dominant balance is between ASR* and OLR* ! slopes

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

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.

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)

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

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)

AHT change and moist/dry contributions ΔAHT = Δdry + Δmoist AHT #s are different cause CCSM is excluded here 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

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

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

MHTEQ, AHTEQ and OHTEQ

ITCZ change

ITCZ intensity change and AHTEQ

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

Precipitation change Contours are precipitation in the PI climatology

Seasonal precipitation changes

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

Seasonal Heating

Seasonal Heating Climatology

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

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

Seasonal surface flux change and ice change

Zonal average change in seasonal heating

Change in seasonal amplitude of temperature

EXTRAS

MHT and partition change in each model

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

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

Climatological seasonal amplitude of temperature