Climate Modelling Group
School of Earth and Ocean Sciences



Improved Representation of Sea Ice in the CCCma
Global Coupled Climate Model

Proposal to the Climate Change Action Fund (CCAF)
(Climate model improvements)


 

INVESTIGATORS

        1. Andrew J. Weaver,
            University of Victoria
        2. Gregory M. Flato,
            Canadian Centre for Climate Modelling and Analysis, Environment Canada

INTRODUCTION:

    Current global climate models, including the CCCma versions CGCM1 and CGCM2, treat sea-ice dynamics and thermodynamics in a rather idealized manner. CGCM1 included only thermodynamic processes, assuming a motionless ice cover (Flato et al., 1999). CGCM2 includes a simplified representation of ice dynamics via the so-called 'cavitating fluid' rheology (Flato and Hibler, 1992). The enhanced climate warming sensitivity in the polar regions displayed by such models is, in part at least, a reflection of positive feedbacks involving sea ice. This motivates improvements in the treatment of sea-ice processes, both to enhance the credibility of climate change projections and to include additional feedbacks which may alter simulated climate and its sensitivity. In this proposal, we aim to take advantage of recent developments in sea-ice modelling to produce tangible improvements in sea-ice process representation in the Canadian Global Coupled Model.

OBJECTIVES:
    We seek funding to support a post-doctoral fellow or research associate for two years to: a) implement a recently developed multi-category, dynamic-thermodynamic sea-ice model in the CCCma Global Coupled Climate Model; b) develop a suite of diagnostic programs to analyse the results of this sea-ice component; c) conduct a series of experiments with the updated coupled model to evaluate the new sea-ice component and assess its impact on modelled climate and climate sensitivity.

METHODOLOGY:
    A new sea-ice model has been recently constructed in the climate modelling group at the University of Victoria, based on components developed elsewhere. This model employs a sophisticated sea-ice rheology (Hunke et al., 1997) to calculate the evolving ice velocity field, a multi-layer thermodynamic scheme (Bitz and Lipscombe, 1998), and a multi-category representation of the thickness distribution function (Schramm et al., 1997; Bitz, 1999). The latter involves a streamlined numerical approach which reduces the complexity of the code relative to earlier versions (e.g. Flato and Hibler, 1995), making it tractable in a global climate simulation. The velocity calculation is based on a widely accepted representation of internal ice stresses, but with a novel numerical solution technique developed at the Los Alamos National Lab. This model has recently been implemented in a simplified coupled model at the University of Victoria, and tested extensively in present-day and future climate scenarios (Holland et al. 1999a,b). This scheme is now also being implemented in the NCAR global coupled model. The new model, with its 'state-of-the-art' physical parameterisations, has the potential to improve the global model's simulation of ice motion and associated freshwater transport, as well as surface energy exchanges and ice growth and melt. All of these have important ramifications for the simulation of present-day climate and its sensitivity to greenhouse gas and other perturbations, particularly for areas of relevance to Canada. The proposal is to take this sea-ice model and develop it into a module for inclusion in the Canadian Centre for Climate Modelling and Analysis (CCCma) global coupled model (Flato et al., 1999). This involves revisions to the ice-model code to accommodate the CCCma data structure, model grid and NEC computer architecture, along with modifications to the coupled model to incorporate the new process parameterisations. The revisions will be done in such a way as to allow either the new scheme or the existing, simpler, scheme to be used via simple user-specified switches. The new scheme will be tested in the context of control and transient simulations with the coupled model to evaluate its performance and to assess the sensitivity of the simulated climate, and its change under greenhouse-gas forcing, to the improved representation of sea-ice. Analysis of these simulations will involve development of a suite of diagnostic programs to compute various derived quantities and statistics from the model output (especially those involving ice growth, melt and transport) and to compare these results to observations where available.

NEED FOR CCAF FUNDING:
    The proposed work is targeted directly at the 'Climate Model Improvements' call for proposals, and will provide tangible, short-term deliverables which directly contribute to the Canadian Global Climate Model and its evaluation. The proposed work is closely connected to a much broader Climate Research Network (CRN) project "The Arctic Ocean and its Role in Climate Change/Climate Variability", (the so-called 'Arctic Node') of which Weaver and Flato are co-investigators (along with others). The Arctic Node is targeted primarily at improved understanding the role of the Arctic in high-latitude climate variability and improving the representation of the Arctic ocean and its mixing and circulation processes, its ice cover, and their coupling, for potential use in the Canadian global climate model. However, the bulk of the research proposed in the Arctic Node project will be done using the simplified UVic climate model. CCAF funding will, by focussing specific, additional effort on sea-ice model improvements, allow quick transferral and implementation of improved ice modelling capabilities in the CCCma global model. It will also allow development of associated diagnostic and analysis programs and permit the extensive testing, evaluation and experimentation that would otherwise not be possible. As a result of the existing CRN project, the present proposal will lever substantial funds as outlined in the BUDGET section.

EXPERTISE:
    The collaborators in this proposal bring a wealth of relevant expertise. A. Weaver and his research group have expertise in ocean, sea-ice, and coupled climate modelling. G. Flato has been an active developer of sea-ice models for use in climate and operational applications, and is a co-developer of the CCCma global coupled climate model.

DELIVERABLES:
    At the end of the two year funding period we will have produced a new sea-ice module for the CCCma global coupled model which includes state-of-the-art process parameterisations recently assembled by the University of Victoria group. Additional benefits: This proposal will promote the development of expertise in an area of research of special interest to Canada, and in particular will entrain University researchers in the development of improved climate modelling capabilities in Canada.

BUDGET:
 

Description Year 1 Year 2
one (1) postdoctoral fellow or 
research assistant
$45 000 $45 000
Travel, publications and 
incidental expenses
$5 000 $5 000
Total $50 000 $50 000

LEVERAGE:
    The work proposed here will compliment (and gain leverage from) the recently funded Arctic Node of the Climate Research Network in which Flato and Weaver are co-investigators (along with others). The co-investigators in this project are: Andrew Weaver, Ed Carmack, Lawrence Mysak and Greg Flato. The Arctic Node will create a 'critical mass' of Arctic ocean and ice modelling and process studies here at UVic, IOS and CCCma, and draw on the ongoing activities at McGill. The CCAF proposal adds to this existing collaborative framework by promoting special attention on transferring ice model improvements arising from this collaboration to the CCCma global model. Specifically, the leveraging is as follows: o Salaries of the two principal investigators are covered from other sources, and so the portion of their time devoted to this project is available at no cost to the project. o Computing hardware and associated costs are covered from other sources. o Office space, furniture and other infrastructure is covered from other sources. o The project will benefit from interaction with ongoing Arctic ocean and ice modelling research funded (at an amount of ~$200k/year) through the CRN Arctic Node and Weaver's NSERC strategic grant (~$160k/year). The CCAF support of an additional researcher will create a 'critical mass' of scientists involved in this topic, and will allow model developments, sensitivity experiments, and diagnostic studies which would not be done otherwise. o Overall, CCAF support of the present proposal would enjoy leveraged funds and in-kind support far in excess of the amount requested.

PROJECT MANAGEMENT:
    The project will be coordinated by A Weaver, with funds deposited in a University of Victoria account. The Post-doc or research associate will be jointly supervised by G. Flato and A. Weaver, and will be based at the University of Victoria/CCCma.

REFERENCES:

Bitz, C.M., 1999: Simulating the ice-thickness distribution in a climate model. manuscript in prep.

Bitz, C.M., and W.H. Lipscomb, 1998: A new energy-conserving sea ice model for climate study, J. Geophys. Res., submitted.

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

Flato, G.M. and W.D. Hibler III, 1995: Ridging and strength in modelling the thickness distribution of Arctic sea ice. J. Geophys. Res., 100, 18,611- 18,626.

Flato, G.M., G.J. Boer, W.G. Lee, N.A. McFarlane, D. Ramsden, M.C. Reader, and A.J. Weaver. 1999: The Canadian Centre for Climate Modeling and Analysis Global Coupled Model and its Climate. Climate Dynamics, submitted.

Holland, M.M., A.J. Brasket, and A.J. Weaver, 1999a: The impact of rising atmospheric CO2 levels on low frequency North Atlantic climate variability. Nature, submitted.

Holland, M.M., C.M. Bitz, M. Eby, and A.J. Weaver, 1999b: The role of ice ocean interactions in the variability of the North Atlantic thermohaline circulation. Journal of Climate, submitted.

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

Schramm, J.L., M.M. Holland, J.A. Curry, and E.E. Ebert, 1997: Modeling the thermodynamics of a sea ice thickness distribution. J. Geophys. Res., 102, 23,079-23,091. 


Return to the Climate Modelling Group WWW page
This page is maintained by www@wikyonos.seos.uvic.ca.
Last updated: