Progress Toward Modeling 3-Dimensional Lake Dynamics Driven by a Global General Circulation Model

The spatial and temporal scales that can be investigated for global and regional aspects of the climate system are beginning to converge. Reducing the number of hand-offs of data among different models in a causal chain leading from anthropogenic greenhouse gases to an end-point impact (lake water levels, fish growth, etc.) reduces the opportunity for conceptual inconsistencies among models in that chain. In contrast to the more conventional plan of using dynamically downscaled climate model output to drive regional phenomena associated with climate change, we are investigating the use of a 3-dimensional model of the Laurentian Great Lakes, both driven directly by output from a general circulation model (GCM) of climate with a global domain, and data statistically downscaled from that GCM. The Great Lakes version of the Finite Volume Community Ocean Model with ice module (FVCOM-CICE) has been tuned for use on the Great Lakes, and currently has an operational version for short-term prediction. The Geophysical Fluid Dynamics Laboratory Climate Model version 4 (GFDL CM4.0) has been developed at that NOAA lab for multi-decadal projection of climate in the air-land-ocean system. Direct driving of FVCOM by output from GFDL CM4.0 will enable greater consistency of modeling than adding downscaling layers, and hence better conceptual fidelity among the pieces of the modeling system. A variety of technical issues have been overcome, and preliminary results of these simulations will be presented.