Contribution of MPI to CLIMARES

Erich Roeckner, Dirk NotzMax Planck Institute for Meteorology, Hamburg

Suggestion: Apply procedure analogous to that of the FP6 ENSEMBLES project

‘Stream 1‘: Global climate simulations to be done for the IPCC AR5 (data available for impact studies by the end of year 2010)

‘Stream 2‘ Additional simulations with improved model - focus on sea ice (data available by the end of year 2011)

Model to be used for stream1

Atmosphere: ECHAM6 (T159L95) including the stratosphere (top at 80km height)

Ocean: MPI-OM (0.4°,L80)

Sea ice: dynamic/thermodynamic (zero-layer)

Aerosols: interactive or prescribed (not yet decided)

Carbon cycle: included

The IPCC AR5 Earth System Model

• ECHam6 (Roeckner et al., 2003), interactive runoff and glacier calving scheme.

• Land surface JSBACH (Raddatz et al., 2007), Dynamic Vegetation (Brovkin et al., 2009)

• New Radiation• Resolution: T63L47 and T159/L95

• OASIS 3.0 coupler• MPIOM (Marsland et al., 2003), C-Grid,

z-level, partial cells, BBL parameterization

• Hibler-type sea ice model incl. snow and fractional ice cover

• Conformal mapping grid: Tri-polar: Resolution: 1°L40, 0.4°L80

• Ocean biogeochemistry module HAMOCC5 (Wetzel et al., 2007)

Model experiments (stream 1 = AR5)

• Hindcasts (1960 to 2005) using observed GHG and aerosol concentrations (or emissions)

• Forecasts until 2035 (RCP4.5*) starting from different observed (assimilated) ocean initial states

• Projections until 2100 and beyond (”centennial”)

Number of realizations envisaged: ≥ 5

* Representative concentration pathways reaching4.5 W/m2 radiative forcing by year 2100

Model experiments (stream 2)

Repeat some of the stream 1 simulationswith an updated model, including new components

• Multi-layer sea-ice model (see contribution D. Notz)

• New parameterization of sea-ice albedo (Pedersen et al. JGR 2009)

New sea-ice model

An improved representation of first-year sea-ice formationAn improved representation of salt fluxes from iceMulti-layer, multi-category sea-ice thermodynamicsImproved albedo scheme (Pedersen et al., 2009)

At MPI, we are currently developing a new sea-ice model.

It will include:

Sea-ice albedo defined separately for

• snow on ice (depends on snow aging)

• bare ice (function of ice thickness)

• melt ponds (depth, fractional area for FYI, MYI)

and specified differently for

• direct, diffuse, visible, near-infrared radiation

Few results from an earlier model version ...

Annual cycle of Arctic sea-ice fractionsECHAM5/MPI-OM (T31L19)

Snow on ice

ponds

bare ice

00,10,20,30,40,50,60,70,80,9

1

f(myi) f(fyi)

minmaxmeanobs1obs2

Simulated (min, max, mean) and observed melt pond fractions (f) obs1 for whole Arctic (1998) ... SSM/I (IARC)obs2 for Beaufort and Chukchi Seas (Tschudi et al, 2004)

0

10

20

30

40

50

60

70

Jun-Aug Jun Jul Aug

obsnewold

Mean Arctic surface albedo(including sea-ice and leads)

Obs: Laine JGR 2004 (AVHRR 1982-1998)

%

Expected outcome in climate change experiments(hypothesis to be checked)

Enhanced sea-ice albedo feedback as a result ofextended melt ponds simulated (and observed) onfirst year ice (FYI) Climate warming

==> MYI decreases, FYI increases==> melt pond area increases==> summer albedo decreases==> enhanced absorption of sunlight==> further warming

Planned work within WP 110

Simulations with the new coupled model will be used within WP 110 to provide all partners with

● Distribution of ice thickness and ice concentration throughout the entire Arctic Ocean● Uncertainty ranges of future sea-ice evolution● Impact of changes in future anthropogenic GHG emissions on the expected sea-ice evolution● Future changes within the Arctic climate system (Air and water temperature, precipitation, wave patterns (-> coastal

erosion), changes in storm activity etc.)

● Manpower: 1 Post Doc for 2 years and 1 PhD for 3 years