CAREER: Physical Modulation of Dissolved Oxygen in Chesapeake Bay

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Physical processes play a dominant role in controlling the inter-annual variability of summertime hypoxia in Chesapeake Bay. The classical model for the development of hypoxia in the Bay assumes a simple one-dimensional balance in which biological oxygen demand exceeds the vertical supply of dissolved oxygen through the pycnocline by turbulent mixing. The PI's recent work suggests a new model for the modulation of hypoxia in which dissolved oxygen is supplied to the sub-pycnocline waters not through direct vertical mixing, but rather through the interactions of lateral circulation and mixing near the boundaries. It is hypothesized that wind-driven lateral circulation is the dominant mechanism that supplies dissolved oxygen to regions susceptible to hypoxia, and that the effectiveness of this mechanism is sensitive to both wind direction as well as estuarine bathymetry. This is supported by both numerical simulations and historical data, but comprehensive field measurements are required to adequately test this hypothesis. The overall research objective of this project is to develop a comprehensive understanding of how physical forcing, including winds, tides and density stratification, modulates dissolved oxygen in Chesapeake Bay. This objective will be achieved through a comprehensive examination of the interactions between circulation, density stratification and estuarine bathymetry and how these interactions ultimately govern when and where the turbulent scalar (salinity, temperature, and oxygen) flux occurs. The public awareness and local importance of hypoxia in Chesapeake Bay make it an ideal socio-scientific issue for a comprehensive context-based education plan for students and the general public in the greater Hampton Roads area. The educational activities in this project will promote an interdisciplinary examination of hypoxia in Chesapeake Bay that highlights the interactions between biological and physical processes and stresses the role of science in shaping public policy.Intellectual Merit: Understanding how circulation interacts with density stratification to control when and where turbulent scalar flux occurs is a fundamental problem in coastal and estuarine oceanography. It significantly impacts a wide range of physical and biogeochemical processes and exerts a first order control on hypoxia. Hypoxia is one of the most pressing water quality issues facing coastal and estuarine waters, yet there are few if any detailed studies that resolve the turbulent mixing processes that modulate dissolved oxygen. The measurements collected here will represent the most comprehensive examination of turbulent mixing in Chesapeake Bay, including unprecedented measurements of the direct turbulent flux of oxygen.Broader Impacts: The scientific goals of this study are of fundamental importance to assessing efforts to restore water quality in Chesapeake Bay. The results from this research will help regulatory agencies and policymakers better design and assess restoration efforts in this economically and ecologically important estuary. The educational activities of this proposal are designed to promote scientific literacy about the issue of hypoxia by targeting both the general public and students across a wide range of educational levels. The development of the Summer Hypoxia/Anoxia Research Program (SHARP) will provide unique research opportunities for undergraduate students, specifically targeting underrepresented minorities through a partnership with Hampton University. The integration of hypoxia into the Chesapeake Interactive Modeling Program (CHIMP) will provide a powerful tool for educating the public about one of the most important water quality issues in Chesapeake Bay. This new tool will be made available to the extensive group of educators already using the original version of CHIMP, and it will be used to educate middle school students involved in the Mentoring Young Scientist Program and the general public through a display at the Virginia Aquarium.