Wen Long

Climate Forcing and Salinity Variability in Chesapeake Bay, USA

Salinity is a critical factor in understanding and predicting physical and biogeochemical processes in the coastal ocean where it varies considerably in time and space. In this paper, we introduce a Chesapeake Bay community implementation of the Regional Ocean Modeling System (ChesROMS) and use it to investigate the interannual variability of salinity in Chesapeake Bay. The ChesROMS implementation was evaluated by quantitatively comparing the model solutions with the observed variations in the Bay for a 15-year period (1991 to 2005). Temperature fields were most consistently well predicted, with a correlation of 0.99 and a root mean square error (RMSE) of 1.5°C for the period, with modeled salinity following closely with a correlation of 0.94 and RMSE of 2.5. Variability of salinity anomalies from climatology based on modeled salinity was examined using empirical orthogonal function analysis, which indicates the salinity distribution in the Bay is principally driven by river forcing. Wind forcing and tidal mixing were also important factors in determining the salinity stratification in the water column, especially during low flow conditions. The fairly strong correlation between river discharge anomaly in this region and the Pacific Decadal Oscillation suggests that the long-term salinity variability in the Bay is affected by large-scale climate patterns. The detailed analyses of the role and importance of different forcing, including river runoff, atmospheric fluxes, and open ocean boundary conditions, are discussed in the context of the observed and modeled interannual variability.

Modeling and forecasting the distribution of Vibrio vulnificus in Chesapeake Bay

To construct statistical models to predict the presence, abundance and potential virulence of Vibrio vulnificus in surface waters of Chesapeake Bay for implementation in ecological forecasting systems.

Sensitivity of Circulation in the Skagit River Estuary to Sea Level Rise and Future Flows

Abstract Future climate simulations based on the Intergovernmental Panel on Climate Change emissions scenario (A1B) have shown that the Skagit River flow will be affected, which may lead to modification of the estuarine hydrodynamics. There is considerable uncertainty, however, about the extent and magnitude of resulting change, given accompanying sea level rise and site-specific complexities with multiple interconnected basins. To help quantify the future hydrodynamic response, we developed a three-dimensional model of the Skagit River estuary using the Finite Volume Community Ocean Model (FVCOM). The model was set up with localized high-resolution grids in Skagit and Padilla Bay sub-basins within the intermediate-scale FVCOM based model of the Salish Sea (greater Puget Sound and Georgia Basin). Future changes to salinity and annual transport through the basin were examined. The results confirmed the existence of a residual estuarine flow that enters Skagit Bay from Saratoga Passage to the south and exits through Deception Pass. Freshwater from the Skagit River is transported out in the surface layers primarily through Deception Pass and Saratoga Passage, and only a small fraction (∼ 4%) is transported to Padilla Bay. The moderate future perturbations of A1B emissions, corresponding river flow, and sea level rise of 0.48 m examined here result only in small incremental changes to salinity structure and interbasin freshwater distribution and transport. An increase in salinity of ∼1 psu in the near-shore environment and a salinity intrusion of approximately 3 km further upstream is predicted in Skagit River, well downstream of drinking water intakes.

Estuarine Sediment Dissolved Organic Matter Dynamics in an Enhanced Sediment Flux Model

Sediment derived dissolved organic matter (DOM) can comprise a substantial portion of the organic carbon budget in coastal bottom waters, yet it is often neglected in coastal carbon cycle models. In most modern sediment-water column flux models, biologically mediated reactions that remineralize particulate organic matter (POM) into inorganic compounds are simplified. In reality, organic matter remineralization is a complex suite of reactions that include DOM intermediate compounds. To better represent the sequential breakdown of POM and remineralization of DOM, a DOM state variable was built into a widely used sediment flux model. In the model, DOM is created in the sediment by hydrolysis of POM, and all organic matter passes through the DOM pool before remineralization. The model was run for 11 years and tuned to reproduce observed sediment flux data collected in Chesapeake Bay and then used to assess the role of DOM in sediment organic matter dynamics. Sediment-water column fluxes of DOM are highly variable both on seasonal and inter-annual scales, with substantial variability among stations in both magnitude and flux direction. Across all stations, semi-labile and inert DOM is lost and labile DOM is taken up into the reactive first layer of the modeled sediment, with the net flux a balance of the two processes. The improved sediment flux model can be utilized to better understand the role of sediment biogeochemistry in the estuarine and coastal carbon cycle, and shed light on difficult to measure processes involving DOM intermediate compounds.