PIs: David J. Schwab and Dmitry Beletsky

The main objective of this proposal is to identify and quantify the physical processes generating nearshore- offshore transport of biogeochemically important materials in the Great Lakes during episodic events by applying a coupled ice-circulation model to Lake Michigan. The specific objectives include:

• To determine the role of ice in timing and magnitude of the plume events
• To determine whether the plume occurrence represents a response to the aggregate effects of a season of individual storm events, an episodic response to a single large storm event or a complex interaction between the low-frequency (seasonal) preconditioning of the lake and a single storm event that occurs at a critical time.
• To determine the importance of mesoscale atmospheric dynamics on the development of the plume.
• To determine the role of local bathymetry in the separation/meandering of the plume.
• To determine the influence of thermal effects on the dynamics of the plume.
• To refine the ice and circulation models using the results of an extensive observation program.
• To link the ice-circulation model and the Lake Michigan wind wave prediction model with a sediment resuspension/transport model in order to quantify the cross-isobath transport of resuspended material in the lake.
• To link the ice-circulation model with a nutrient and lower food web model in order to investigate the impact of nearshore-offshore transport during episodic events on biological processes in the lake.
• To incorporate the results of these investigations into a computer-based Information and Forecasting System.

1. Ice Modeling - develop Great Lakes Ice Model
2. Circulation Modeling - apply Great Lakes version of Princeton Ocean Model to Lake Michigan for EEGLE study years
3. Wave Modeling - apply GLERL/Donelan Wave Model to Lake Michigan for EEGLE study years
4. Integration with Sediment Transport Modeling and Lower Food Web Modeling Projects

1. The spectacular eddy-like plume that occurred during the 1998 EEGLE pilot year was used as a case study for coupled hydrodynamic/wave/sediment transport and coupled hydrodynamic/biological models. The case studies confirmed the episodic nature of lake circulation and sediment transport in the lake as well as identifying light limitation from suspended material in the plume region as a critical factor in primary production.
2. The combination of high waves and the two-gyre circulation pattern in southern Lake Michigan during storms with northerly winds appears to be responsible for the asymmetric distribution of bottom sediments in the lake.
3. During the unusually warm EEGLE pilot year and field years the role of ice in plume formation was a negligible factor so the work on developing a Great Lakes ice model was postponed.