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 and Gregory Flato

3. COLLABORATOR(S):

 

4. REPORT AGAINST PROJECT GOALS AND DELIVERABLES (for period ending 31 March 2000):

A description of, and the results from, a number of sensitivity analyses conducted using the sea ice model, to be included in the CCCma coupled model, has been submitted for publication (Bitz et al. 2000) and we are awaiting reviews. In the mean time, Linda Waterman (a new PhD student) and Mike Eby (a Research Associate), both funded off CICS Arctic grants, are undertaking further sensitivity analyses using this model.

After a delay in receiving funding, a post-doctoral fellow (Oleg Saenko) has been hired and he has recently commenced work on the project. He has so far familiarized himself with the sea-ice model and has begun a series of test calculations aimed at improving the representation of ocean convection under ice. In particular, an improved parameterization of sub-grid scale convection due to sea ice formation is being developed. Resolving a distribution of sea ice thickness within a given model grid cell enables us to account for the brine released under each ice category and to apply convective mixing to both ocean salinity and temperature under a density-unstable ice category. The latter is allowed to occur even if the ocean is vertically stable over the whole model grid cell. It is hoped that the new parameterization of brine rejection/sinking will improve the simulation of the ocean thermocline structure, and in particular deep water formation. A better simulation of Antarctic Bottom Water (AABW) due to sea ice formation should result in a better simulation of Antarctic Intermediate Water (AAIW). These water masses, jointly with North Atlantic Deep Water (NADW), are known to define deep ocean structure, thus influencing long-term variability of climate. Dr. Saenko is using the UVic coupled model as the tool for testing the new parameterization.

As he works on the parameterization development, Dr. Saenko is also familiarizing himself with the CCCma global coupled model, into which the sea-ice model will be incorporated. In collaboration with the principal investigators, a detailed work plan has been outlined for the coming year. This involves a methodical approach of first inserting and testing the dynamic portion of the ice model (that part which computes ice motion). This will be followed by inserting and testing the thermodynamic portion (that part which computes vertical ice growth and melt); and ultimately inserting and testing that portion that involves the evolution of the thickness distribution function (the sub-grid-scale variation of ice thickness).

In the mean time, Greg Flato at the CCCma has been developing and testing sea-ice diagnostic programs to display ice motion fields, compute ice mass transports, and calculate various statistics related to ice motion and variability. These will be used throughout the project to analyze the results of the developing sea-ice component of the CCCma coupled model.

 

Reference:

Bitz, C.M., M.M. Holland, A.J. Weaver, and M. Eby, 2000: Simulating the ice-thickness distribution in a coupled climate model. J. Geophys .Res., submitted.

 

5. ANY COMMENTS OR CONCERNS ON STATE OF PROGRESS:

None

6. CCAF FUNDS RECEIVED

TO MARCH 31, 2000: $35,000

7. CCAF FUNDS SPENT

TO MARCH 31, 2000: $35,000

8. SOURCES AND AMOUNTS OF non-CCAF FUNDS USED TO DATE (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).

9. PREPARED BY:

Andrew Weaver

10. DATE:

March 31, 2000




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