Biogeosciences, 15, 2649-2668, 2018
https://doi.org/10.5194/bg-15-2649-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
04 May 2018
The competing impacts of climate change and nutrient reductions on dissolved oxygen in Chesapeake Bay
Isaac D. Irby, Marjorie A. M. Friedrichs, Fei Da, and Kyle E. Hinson Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, VA 23062, USA
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.
Citation: Irby, I. D., Friedrichs, M. A. M., Da, F., and Hinson, K. E.: The competing impacts of climate change and nutrient reductions on dissolved oxygen in Chesapeake Bay, Biogeosciences, 15, 2649-2668, https://doi.org/10.5194/bg-15-2649-2018, 2018.
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Short summary
We use an estuarine-watershed modeling system of the Chesapeake Bay to examine the impact climate change may have on the ability of nutrient reduction regulations to increase dissolved oxygen. We find that climate change will move the onset of hypoxia ~7 days earlier, while also decreasing oxygen in the bay primarily due to increased temperature. While this effect is smaller than the increase in oxygen due to nutrient reduction, it is enough to limit the regulation's future effectiveness.
We use an estuarine-watershed modeling system of the Chesapeake Bay to examine the impact...
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