Summary 26 September 2012

Core Theme 2:  Assessing sources of uncertainty in ocean analyses and forecasts

Lead: Steffen M Olsen (DMI), Co-lead: H. Drange (NERSC)Participants: UiB, GEOMAR, UPMC-LOCEAN, MET-O, NERSC, DMI, MPG

CT2 overview, Hamburg

THOR 2012

Collaborative work: Paper on the historical hosing experiments now online

- Swingedouw et al. 2012, Clim. Dyn.

New coordinated sensitivity simulations using RCP8.5 scenarios completed - Five model-member ensemble.

Analysis and interpretations initialized- CT2 hands-on workshop in Paris, May 2012.

Developments:New model based estimate of plausible future GIS mass loss available from MPI

Deliverables months 48D34 WP2.1 : Updated evaluation of ocean state estimates (CT3 obs)D35 WP2.2 & 2.3 : Recommendation of model developments to improve

future THC forecasts

D34 concludes also on D04 (ongoing throughout the project)

CT2: Assessing sources of uncertainty…

CT2 overview, Hamburg

THOR 2012

RCP8.5 hosing experiments

Setup and models

• RCP8.5 over the period 2006-2100

• 0.1 Sv distributed around Greenland for the period 2050-2090

• Four models: EC-Earth, MPI-ESM, HadCM3, IPSLCM5A-LR, BCM2

Hosing relative to 2050

Hosing-R

CP

8.5

CT2 overview, Hamburg

THOR 2012

AMOC response to hosing

CT2 overview, Hamburg

THOR 2012

Preliminary conclusions

• Smaller impact than under historical (and Stouffer et al. 2006) but not negligible: around 1 Sv at 26°N (1.5 Sv for the max) in 40 years. (equivalent to around 0.05 PW decrease at 26°N in HT)

• Deep convection already ceased south of the GSR (Labrador Sea) in all model by year 2050.

• In the strongly forced experiment (RCP8.5) the deep ocean apears decoupled and the ocean impact of hte hosing is confined to the upper ~ 800m

• Apparently reduced AMOC sensitivity to GrIS melting in a warming climate!

CT2 overview, Hamburg

THOR 2012

Greenland's response and interaction within a fully coupled ice sheet-earth system for the near-future

Christian Rodehacke, Miren Vizcaino, Uwe Mikolajewicz

• ESM: ECHAM6 T63/MPIOM GR15 (T63L47GR15L40)• Ice sheet model: mPISM (SIA+SSA)

Greenland: Resolution horizontal 10 km, vertical 40 m

• Ctrl: Control Run for pre-industrial state: pCO2=284ppm• abrupt: immediate increase to 4xpCO2 • 1pct: Gradual pCO2 increases by1% per year until 4xpCO2, then constant • 1pct_alone: same as 1pct but ice sheet melt water is from Ctrl

CT2 overview, Hamburg

THOR 2012

GrIS melting under global warming

Ctrl, abrupt, 1pct, 1pct_alone

Ice mass loss rate (mSv)

Thi

ckne

ss a

nom

alie

s (m

)gr

owsh

rink

Equilibrium lines Ctrl 1pct

Ice thickness1pct – Ctrl : 350yr

1pct

Ctrl

abrupt

0yr 200yr 350yr

CT2 overview, Hamburg

THOR 2012

GrIS melting under global warming

abrupt

1pct_alone

1pct

CtrlStronger radiative forcing results ultimately in a weaker AMOC

In the first 200yr the additional melt water hardly affects the AMOC

AMOC

CT2 overview, Hamburg

THOR 2012

CT2 activities will continue after Thor

- joint analysis and publication on the RCP8.5 exercise.

- intercation with CT3 on exploiting Thor observations in ocean state estimates and analysis.

Note the CT2 multi model data archive of historical and RCP8.5 hosing experiments.

THOR is a project financed by the European Commission through the 7th Framework Programme for Research, Theme 6 Environment, Grant agreement 212643 http://ec.europa.eu/index_en.htm