Types of Estuaries and Mixing Patterns. Mrs. Stahl Marine Science Honors

Transcription

1 Types of Estuaries and Mixing Patterns Mrs. Stahl Marine Science Honors

2 Coastal Plain Form between glacial periods, when water from melting glaciers raises the sea level and floods coastal plains and low lying rivers. Ex- Gulf of Mexico, Eastern Atlantic, Chesapeake Bay, and Long Island Sound

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5 Tectonic Estuary Form when geological events, such as earthquakes, cause the land to sink below sea level, allowing seawater to cover it. Ex- San Francisco Bay

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7 Bar Built Estuary When geographical barriers, such as islands, form walls between FW and SW. Ex- Cape Hatteras, N.C., Texas and Florida Gulf Coasts, Indian River, Fl., and the Coast of Northern Europe.

8 Indian River Lagoon

9 Cape Hatteras, N.C.

10 Fjord Form when glaciers carve large valleys in coastal areas. After the glaciers retreated these valleys filled with water and formed a type of estuary. Ex- Alaska, Along the coast of Scandinavia

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13 Norway Fjord

14 Salinity and Mixing Patterns Foldable Terms to know portion of the foldable: Tidal over-mixing Positive estuary Negative estuary Brackish water Salt wedge Tidal flats Embayments Notes

15 Vocabulary Tidal over-mixing- The denser seawater at the surface tends to sink as the lighter FW beneath it rises, creating a mixing action from the surface to the bottom. Positive estuary- Surface water from the river flows out to sea and SW from the ocean moves into the estuary along the bottom. Negative estuary- Surface water flows toward the river and the water along the bottom moves out to sea. Brackish water- Mixture of FW and SW that is less saline than ocean water.

16 Salt wedge- The angled boundary between SW and FW in an estuary that occurs when the rapid flow of river water prevents the SW from mixing with the FW. Tidal flats- An area of estuary that is exposed at low tide and covered at high tide. Embayments- a recess in a coastline forming a bay.

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18 Positive estuary

19 Salt Wedge

20 Tidal Flats

21 Embayments

22 Notes to the right of vocab Average salinity is 35 ppt. Strongly influences marine organisms as they work to maintain appropriate levels of salt and water in their bodies. Six ions are responsible for 99% of the dissolved salts in the ocean Sodium Magnesium Calcium Potassium Chloride Sulfate Other 1% are called trace elements

23 Temperature- on the back Relatively shallow- the water temp changes rapidly with changes in air temp. Fluctuates seasonally and daily. Depending on location, some estuaries may freeze in the winter. Tidal currents warm or cool an estuary.

24 Surface water can be cooler in the winter and warmer in the summer than deeper water, as a result of the amount of solar energy reaching the surface. Produces a winter turnover in which cooler / denser surface water sinks and is replaced by warmer, deeper water. Vertical mixing of nutrients gets mixed up and swept back out to sea with the next tide. The mixing that occurs because of turnover circulates nutrients vertically between the water and bottom sediments (upwelling and downwelling).

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26 Salt Wedge Occur in the mouths of rivers that are flowing into SW. At the surface, FW flows rapidly out to sea, and at the bottom the denser SW flows upstream along the river bottom. Produces an angled boundary known as a salt wedge between the two. Example- Mississippi

27 Mississippi Salt Wedge

28 Well Mixed Estuary River flow is low and tidal currents play a major role in the circulation of the water. Result= seaward flow of water and uniform salinity at all depths. Ex- Delaware Bay

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30 Partially Mixed Estuary Have a strong surface flow of FW and a strong influx of seawater, which increases salinity. Tidal currents force the seawater upward where it mixes with the surface water, producing a seaward flow of surface water. Rapid exchange of surface water between the estuary and ocean. Examples- Puget Sound and Chesapeake Bay

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32 Fjord River water remains at the surface and mixes very little with the seawater beneath it.