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Effects of Wind Straining on Estuarine Stratification: A Combined Observational and Modeling Study

Citation: Xie, X., & Li, M. (2018). Effects of wind straining on estuarine stratification: A combined observational and modeling study. Journal of Geophysical Research: Oceans, 123, 2363-2380.

A combined observational and numerical modeling study was conducted to clarify the effects of wind straining on estuarine stratification. Long-term mooring observations in the middle of Chesapeake Bay showed an asymmetric stratification response to along-channel winds. The stratification decreased under up-estuary winds. Under down-estuary winds, however, the stratification increased at moderate wind speeds but decreased at high wind speeds. In concert with numerical modeling, the mooring and ship-based survey data were analyzed to test the wind-straining mechanisms. In the middle and upper parts of the estuary, the straining of the density field by the vertical shear of the along-channel current dominates the stratification response, enhancing stratification under the down-estuary winds but reducing it under the up-estuary winds. A regime diagram was constructed to place the wind-induced stratification change in terms of the dimensionless Wedderburn number W: it is a linearly function of W for W > 0 (up-estuary winds) but a parabolic function of W for W < 0 (down-estuary winds). In the lower part of the estuary, however, the stratification response to the wind direction was opposite to that in the middle and upper Bay. The wind-driven lateral circulation was much stronger there, and the cross-channel straining of the density field by the vertical shear in the lateral currents drove the stratification response in the lower Bay. Therefore, both the along-channel and cross-channel straining regulate the estuarine stratification, and the net stratification change over a wind event is determined by the relative strength of along-channel and cross-channel straining.

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The NOAA Ocean Acidification Program (OAP) works to prepare society to adapt to the consequences of ocean acidification and conserve marine ecosystems as acidification occurs. Learn more about the human connections and adaptation strategies from these efforts.

Adaptation approaches fostered by the OAP include:


Using models and research to understand the sensitivity of organisms and ecosystems to ocean acidification to make predictions about the future, allowing communities and industries to prepare


Using these models and predictions as tools to facilitate management strategies that will protect marine resources and communities from future changes


Developing innovative tools to help monitor ocean acidification and mitigate changing ocean chemistry locally


On the Road

Drive fuel-efficient vehicles or choose public transportation. Choose your bike or walk! Don't sit idle for more than 30 seconds. Keep your tires properly inflated.

With your Food Choices

Eat local- this helps cut down on production and transport! Reduce your meat and dairy. Compost to avoid food waste ending up in the landfill

With your Food Choices

Make energy-efficient choices for your appliances and lighting. Heat and cool efficiently! Change your air filters and program your thermostat, seal and insulate your home, and support clean energy sources

By Reducing Coastal Acidification

Reduce your use of fertilizers, Improve sewage treatment and run off, and Protect and restore coastal habitats

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You've taken the first step to learn more about ocean acidification - why not spread this knowledge to your community?

Every community has their unique culture, economy and ecology and what’s at stake from ocean acidification may be different depending on where you live.  As a community member, you can take a larger role in educating the public about ocean acidification. Creating awareness is the first step to taking action.  As communities gain traction, neighboring regions that share marine resources can build larger coalitions to address ocean acidification.  Here are some ideas to get started:

  1. Work with informal educators, such as aquarium outreach programs and local non-profits, to teach the public about ocean acidification. Visit our Education & Outreach page to find the newest tools!
  2. Participate in habitat restoration efforts to restore habitats that help mitigate the effects of coastal acidification
  3. Facilitate conversations with local businesses that might be affected by ocean acidification, building a plan for the future.
  4. Partner with local community efforts to mitigate the driver behind ocean acidification  – excess CO2 – such as community supported agriculture, bike & car shares and other public transportation options.
  5. Contact your regional Coastal Acidification Network (CAN) to learn how OA is affecting your region and more ideas about how you can get involved in your community
       More for Taking Community Action