Abstract
Abstract. The Chesapeake Bay region is projected to experience changes in temperature, sea level, and precipitation as a result of climate change. This research uses an estuarine-watershed hydrodynamic–biogeochemical modeling system along with projected mid-21st-century changes in temperature, freshwater flow, and sea level rise to explore the impact climate change may have on future Chesapeake Bay dissolved-oxygen (DO) concentrations and the potential success of nutrient reductions in attaining mandated estuarine water quality improvements. Results indicate that warming bay waters will decrease oxygen solubility year-round, while also increasing oxygen utilization via respiration and remineralization, primarily impacting bottom oxygen in the spring. Rising sea level will increase estuarine circulation, reducing residence time in bottom waters and increasing stratification. As a result, oxygen concentrations in bottom waters are projected to increase, while oxygen concentrations at mid-depths (3 < DO < 5 mg L−1) will typically decrease. Changes in precipitation are projected to deliver higher winter and spring freshwater flow and nutrient loads, fueling increased primary production. Together, these multiple climate impacts will lower DO throughout the Chesapeake Bay and negatively impact progress towards meeting water quality standards associated with the Chesapeake Bay Total Maximum Daily Load. However, this research also shows that the potential impacts of climate change will be significantly smaller than improvements in DO expected in response to the required nutrient reductions, especially at the anoxic and hypoxic levels. Overall, increased temperature exhibits the strongest control on the change in future DO concentrations, primarily due to decreased solubility, while sea level rise is expected to exert a small positive impact and increased winter river flow is anticipated to exert a small negative impact.
Highlights
Global climate change is projected to alter the world’s marine environments with coastal and estuarine systems bearing exacerbated impacts
This study examines the impact of climate change on oxygen concentrations in the Chesapeake Bay by utilizing a coupled hydrodynamic–biogeochemical model that has previously been compared to other Chesapeake Bay models (Irby et al, 2016)
The most striking result of this research is that the potential impact of climate change by the mid-21st century is much smaller than the impact of the 2010 Total Maximum Daily Load (TMDL) nutrient reductions, at anoxic and hypoxic levels
Summary
Global climate change is projected to alter the world’s marine environments with coastal and estuarine systems bearing exacerbated impacts. As the climate continues to change, it is important to evaluate the impact these changes will have on DO concentrations in critical coastal environments like the Chesapeake Bay. Climate change is generally predicted to have a net negative effect on DO in coastal waters through changes in temperature, sea level, and precipitation (Boesch et al, 2007; Meier et al, 2011; Altieri and Gedan, 2015). Climate change is generally predicted to have a net negative effect on DO in coastal waters through changes in temperature, sea level, and precipitation (Boesch et al, 2007; Meier et al, 2011; Altieri and Gedan, 2015) Higher temperatures impact both the timing and rates of biological functions, while potentially driving changes in oxygen production and consumption (Winder and Sommer, 2012).
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