Climate Modelling Group
School of Earth and Ocean Sciences


1. PROJECT TITLE: "Improved Representation of Sea Ice in the CCCma Global Coupled Climate Model"

Project # (for CCAF use)

S99-14-08

2. PRINCIPAL INVESTIGATOR(S):

Andrew J. Weaver, Gregory M. Flato

3. COLLABORATOR(S):

 

4. REPORT AGAINST PROJECT GOALS AND DELIVERABLES (for period ending September 30, 2000):

The primary objective of this work is to provide a new, ‘state-of-the-art’ sea ice component for use in the CCCma global climate model. This will include the Hunke and Dukowicz (1997) ice dynamics model and the Bitz and Lipscombe (1999) multi-category thermodynamic model. In order to allow efficient testing of the new sea-ice and related ocean parameterizations, this ice model has been coupled to a global ocean model (a version of the GFDL MOM code).

A series of global ice-ocean model experiments were conducted to investigate the sensitivity of ocean temperature and salinity distributions and circulation patterns to the parameterization of under-ice mixing — specifically the disposition of brine rejected during ice formation.

In a second set of experiments, the global ice-ocean model was forced in one case by ‘observed’ atmospheric data (NCEP reanalysis) and in another case by the observed forcing plus the changes projected by the CCCma global coupled model at the middle of the 21st century. These experiments provide an estimate of the sensitivity of the new sea-ice component to the forcing changes expected under greenhouse-gas-induced climate warming.

Results from these two sets of ice-ocean model experiments have been analyzed and a manuscript is in preparation.

Introduction of the new sea-ice component into the CCCma global coupled model has proceeded in a systematic manner. The latest version of the CCCma global model, CGCM2 (Flato and Boer, 2000), uses a rather idealized sea-ice dynamics scheme (the ‘cavitating fluid’ model of Flato and Hibler, 1992). This has been replaced by the Hunke and Dukowicz ‘elastic-viscous-plastic’ model, and multi-year test runs of the global model were conducted. In these test runs, the thermodynamic component remained unchanged. Work is currently underway to replace the thermodynamic component, although, because of the complexity of coupling between ice and atmospheric surface energy exchanges, this is a substantial technical challenge.

In preparation for replacing the thermodynamic component, stand-alone single-column versions of both the original (‘0-layer’) and new Bitz/Lipscombe thermodynamic models have been constructed. These will allow rapid and efficient parameter studies aimed at optimizing the parameter values to be used in the global model implementation. These single-column model versions are also being used in the WCRP ACSYS/CLIC thermodynamic ice model intercomparison project (http://www.cccma.bc.ec.gc.ca/acsys/simip2). This will allow us to benefit directly from the coordinated evaluation of sea-ice thermodynamic models being conducted by this international project.

References:

Bitz, C.M. and W.H. Lipscomb, An energy-conserving thermodynamic model of sea ice. J. Geophys. Res., 104, 15,669-15,677, 1999.

Flato, G.M. and G.J. Boer, Warming asymmetry in climate change simulations. Geophys. Res. Lett., submitted, 2000.

Flato, G.M. and W.D. Hibler III, Modeling pack ice as a cavitating fluid. J. Phys. Oceanogr., 22, 626-651, 1992.

Hunke, E.C. and J.K. Dukowicz, An elastic-viscous-plastic model for sea ice dynamics. J. Phys. Oceanogr., 27, 1849-1867, 1997.

 

5. ANY COMMENTS OR CONCERNS ON STATE OF PROGRESS:

None

6. CCAF FUNDS RECEIVED, APRIL 1

TO SEPT. 30, 2000: $35,000

7. CCAF FUNDS SPENT, APRIL 1

TO SEPT. 30, 2000: $35,000

8. DO YOU FORESEE FINISHING UNDER BUDGET (CCAF FUNDS)? No

IF SO, BY APPROXIMATELY HOW MUCH? $0.00

9. SOURCES AND AMOUNTS OF non-CCAF FUNDS RECEIVED, APRIL 1

TO SEPTEMBER 30, 2000 (CASH AND IN-KIND):

Support for Mike Eby and Linda Waterman and Wanda Lewis has come from

the CICS Arctic node of the CRN (200,000$ in the past year). The infrastructure

and personnel support for the Climate Modelling Lab, for projects related to

this CCAF initiative comes from NSERC ($160,000 in the past year).

10. PREPARED BY: Andrew Weaver

11. DATE: Sept. 19, 2000




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