Since 2007, we have been providing annual forecasts of the extent of the hypoxic volume in the main stem of the Chesapeake Bay. The model predicts mean July hypoxic volumes using January to May total nitrogen (TN) loads from the Susquehanna River, and is based on an adaptation of the Streeter-Phelps oxygen sag model, adapted from a similar model we built for the Gulf of Mexico. It simulates organic matter decay, oxygen flux through the pycnocline, and sub-pycnocline up-estuary advection in simple first-order processes. TN loading from the Susquehanna River is used as a surrogate for biological oxygen demand from decay of phytoplankton biomass, consistent with studies that have shown the middle reaches of Chesapeake Bay are nitrogen-limited and that phytoplankton biomass in the mid-Bay accounts for as much as 90% of the annual organic matter budget of the estuary. Using the Susquehanna River loads, and initial oxygen deficit estimated from oxygen measurements, the hypoxic volume forecasts, error bounds, and model coefficients were estimated using Bayesian inference for 22 years of data.
Applications of this work have been published in the following papers, and a special website dedicated to the annual forecasts can be found here.
- Zhou, Y., D. Scavia, A.M. Michalak 2014Nutrient loading and meteorological conditions explain interannual variability of hypoxia in the Chesapeake Bay. Oceanogr. 59:373-374
- Evans, M.A. and D. Scavia 2010.Forecasting hypoxia in the Chesapeake Bay and Gulf of Mexico: Model accuracy, precision, and sensitivity to ecosystem change. Res. Letters. doi:10.1088/1748-9326/6/1/015001
- Liu, Y. and D. Scavia. 2010.Analysis of the Chesapeake Bay Hypoxia Regime Shift: Insights from Two Simple Mechanistic Models. Estuaries and Coasts 33:629-639DOI 10.1007/s12237-009-9251-z
- Stow, C.A. and D. Scavia. 2009.Modeling Hypoxia in the Chesapeake Bay: Ensemble Estimation Using a Bayesian Hierarchical Model. Marine Systems 76:244-250.
- Scavia, D., E.A. Kelly, and J. D. Hagy III. 2006.A simple model for forecasting the effects of nitrogen loads on Chesapeake Bay hypoxia.Â Estuaries and Coasts 29(4) 674-684.