ACCESS Ocean and Sea Ice Model CORE II Simulations

ACCESS Ocean and Sea Ice ModelCORE II Simulations

Simon Marsland

CSIRO Marine and Atmospheric Research

WGOMD, Exeter, May 1, 2009

CSIRO. WGOMD, Exeter, May 1, 2009

ACCESSAustralian Community Climate and Earth System Simulator

• The ACCESS Model is being developed by the

Centre for Australian Weather and Climate Research,

a partnership between CSIRO and the Bureau of Meteorology

CouplerOASIS

Atmosphere(UM)

Sea Ice(Auscom – CICE)

OceanBiogeochemistry

(Matear)

AtmosphericChemistry

(UKCA)

Land SurfaceCABLE

(+ CASA-CNP)

Ocean(Auscom – MOM4)

DynamicVegetation (LPJ)


ACCESS Ocean Model: MOM4p1 + OASIS3.2.5 + CICE4

• 46 vertical levels• Nominal 1 degree global horizontal grid

• Tripolar grid in Arctic region• Equatorial meridional refinement: 1/3 degree from 10S to 10N• Mercator grid in Southern Ocean: 1 degree at 30S to 0.25 degree at 78S


ACCESS Implementation Plan

The Atlantic, May 2009

• 2006: choose some models

• 2007: develop some expertise

• 2009: buy a computer and couple the models

• 2010: commence IPCC/CMIP5 runs


How can a CORE II dataset be used by the “outsiders”?

• Nobody (beyond the ocean modellers) expects much from CORE I

• The opposite is true for CORE II. Everybody expects everything.

• Interannual forcing means people want to see the real world

• Modes of variability: ENSO, NAO, IOD, SAM, …• sea ice, watermasses, convection, overturning, …• Transports: Drake, ITF, …• Seasonal variability, Interannual variability, Decadal variability• etc• Even some climate change, e.g. sea level rise

• Highly likely people will use CORE II outputs as a guide when shopping for a model

• Shoppers will look for what they want to see in a model• And then use the CORE II model run of choice as a control for whatever experiment they have been losing sleep over

• And they will want extension of dataset through to 2008, and beyond in due course?

• e.g. Arctic sea ice, Antarctic sea ice, …


10: Initialisation - Repeat cycles or spinup?Need to account for both initial shock and model drift

• Do we want to spin up with climatology (CORE I) and then start CORE II?

• Do we want to run repeat cycles of CORE II, and how many?

COREv2 interannual

COREv1 normal year


Model validation (I): Global Ocean Water mass transports


12: How can we make output more accessible to community

• Central server versus individual repositories?

• If we intend to individually serve our IPCC outputs to community, then this might be a good practice exercise

• What do the AMIP community do?


Current Australian experiences with CORE II

• We have chosen CORE for our tuning runs

• Currently doing both CORE I and CORE II runs

• Laplacian versus Biharmonic• KPP vs Chen vs GOTM• Convective overturn vs enhanced diffusion• Etc …


ACCESS ocean/sea ice model simulation27 years 1979 - 2005

Sea surface temperatureequatorial Pacific (5°N–5°S; 170°W–120°W)

observed

AusCOM model

Upper ocean heat contentequatorial Pacific (5°N–5°S; 180°–110°W; top 300 m)


AusCOM1.0: Long-term mean

temperature along the equator

Levitus climatology:

Temperature along the equator

Equatorial thermocline - mean 1979-2006

Problems:

• Thermocline too diffusea common model problem

•Western Pacific WarmPool too hot


Pacific equatorial undercurrent (m/s)

A variety of problems:

• undercurrent too weak• undercurrent wrong structure

Possible solutions:

• improved Indonesian Throughflow?• need for higher resolution?• biharmonic versus Laplacian friction?

Pers. Comm. Jaci Brown (CSIRO)


5: INSTANT Mooring Program

• Susan Wijffels and Rebecca Cowley (CAWCR)• INSTANT. International Nusantara Stratification and Transport Program

• 2004-2006 continuous moorings in key straits

• Allows direct comparison with ACCESS model transports

LombokOmbai

Timor

Total ITF


INSTANT/ACCESS comparison - Lombok St

We are making incrementalimprovements to modelITF by tuning individualStrait transports against theobserved intra-seasonal variability

• momentum sink parameterisation is used to reduce flow where necessary

• changes to bathymetry toincrease flow wherenecessary


INSTANT/ACCESS comparison - Lombok St

We are making incrementalimprovements to modelITF by tuning individualStrait transports against theobserved intra-seasonal variability


• changes to bathymetry toincrease flow wherenecessary


INSTANT/ACCESS comparison - Timor St

• Model/data collaborationWe are making incrementalimprovements to modelITF by tuning individualStrait transports against theobserved intra-seasonal variability


• changes to bathymetry toincrease flow where necessary


Opening Timor St - massive earthworks required

• Model/data collaboration


INSTANT/ACCESS comparison - ITF (old)

INSTANT (obs)


INSTANT/ACCESS comparison - ITF (new)

INSTANT (obs)


INSTANT/ACCESS comparison - watermasses

Importance of resolvingcorrect watermassesin transports

Requires tuning ofindividual straits

Recent work indicatesenhanced mixing may help (e.g. tides)


INSTANT/ACCESS comparison - vertical structure

Resolving wind drivenStrait transportreversals

Work in progress


The INSTANT project was 2004-06: same years as the recent bug report

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4: Baseline metrics: Validating an Ocean Climate Model

• Start with the Griffies et. al CORE I baseline metrics

• Global Diagnostics• Meridional overturning circulation (Global and Atlantic)

• Strength and depth of North Atlantic Deep Water cell• Atlantic outflow at 30 S• Antarctic Bottom Water Cell• Southern Ocean Cell

• Poleward heat transport (Global and Atlantic)• Gulf Stream and Kuroshio currents• Drake Passage transport• Sea ice concentration and thickness (winter and summer)• North Atlantic and Southern Ocean convection• Tropical Pacific velocity structure


ACCESS Atlantic Meridional Overturning Circulation (Sv)

North Atlantic Deep Water (NADW)

Depth of interface

Antarctic BottomWater (AABW)

Equatorial cells


ACCESS Global Meridional Overturning Circulation (Sv)

AntarcticIntermediate Water (AAIW)

Southern Oceancell


ACCESS barotropic streamfunction (Sv)

KuroshioCurrent

Aghulus

GulfStream

DrakePassagetransport

Indonesian Throughflow


Drake Passage transport (Sv)

• Common Ocean Ice Reference Experiment forcing (CORE)• corrected version of NCEP forcing (Large and Yeager, 2008)• COREv1 climatology - too weak?• COREv2 interannual - too strong?

COREv2 interannual

COREv1 normal year


AusCOM high latitude deep convection sites

Northern Hemisphere Southern Hemisphere

• Mixed layer depth shows main sites of deep convection• Importance for water mass exchange• Importance for overturning circulation


February (winter) August (summer)

AusCOM Arctic sea ice thickness (m)

• Arctic sea ice too thin in summer• Too strong ocean vertical mixing?• Sea ice initial condition? Collapse of Arctic halocline.


February (summer) August (winter)

AusCOM Antarctic sea ice thickness (m)

• Too little summer sea ice• Poor representation of Western Weddell Sea• Nice representation of East Antarctic coastal polynyas


Southern Hemisphere Sea Ice ConcentrationYear 200; climatological forcing


Southern Hemisphere Sea Ice Thickness (m)Year 200; climatological forcing


Surface Temperature and Salinity

Initial Condition Year 100 Year 200

SALINITY

TEMPERATURE


Zonal Average Temperature and Salinity:Loss of Antarctic Intermediate Water

Initial Condition Year 100 Year 200

SALINITY

TEMPERATURE

AAIW

Documents

ACCESS Ocean and Sea Ice Model CORE II Simulations