Coastal Waters and Marginal Seas

1. Coastal Waters and Marginal Seas

2. Salinity Runoff from rivers does not mix well with coastal waters, so a well developed halocline forms Though when shallow enough it will mix making it isohaline

3. Temperature Sea ice forms in high latitudes, while a strong thermocline prevents water to mix in low latitudes Mixing allows water to bring oxygen from the surface to deeper water Offshore winds can carry heat in the summer, or take away heat during the winter

4. Coastal geostrophic currents Geostrophic currents can form as wind blowing parallel to shore piles water up Gravity then pulls it back towards the ocean Then as it runs back the coriolis effect takes over and pulls it to the right or left Even runoff is affected by the coriolis effect

5. Estuaries • Estuary is a partially enclosed body of water in which freshwater runoff dilutes salty ocean water • Most common type is at the mouth of a river • Also most economically important due to being seaports • Experience great variations in temperature and salinity • Classified by both origin and water mixing

6. Origin of estuaries • Coastal plain- formed when sea level rises and flood river valleys • Fjord- formed when valleys carved by glaciers are flooded • U shaped • Moraine- submerged glacial deposit of debris at the mouth of the estuary marks the farthest extent of the glacier

7. Origin of estuaries Bar built estuary- formed from the opening between a lagoon of a sand bar and the ocean Tectonic estuary- formed when faulting or folding of rocks creates a lower area where a river flows

8. Water mixing in estuaries • Vertically mixed estuary- the waters are mixed so salinity just increases as one moves toward the ocean • Slightly stratified estuary- Somewhat deeper, like vertically mixed but two water masses can be identified • Water masses separated by a zone of mixing • The flow of low salinity surface water towards the ocean and subsurface high salinity water towards the river is estuarine circulation pattern

9. Water mixing in estuaries • Highly stratified estuary- strong separation between the two water masses • deep estuary • well developed estuarine circulation • strong halocline • Salt wedge estuary-salt water intrude beneath the river • Typical of high output rivers

10. Estuaries and human activities • Colombia river valley • Between Washington and Oregon • Many dams have altered the flow of the river • Salt wedge • Chesapeake Bay estuary • Formed by drowning of Susquehanna river • Slightly stratified • Water can become anoxic due to waters not mixing well

11. Coastal wetlands • Wetlands are in which the water table is close to the surface, so they are saturated most of the time • Very productive and economically beneficial when left alone • Most important types are salt marshes and mangrove swamps • Both periodically covered by ocean water • Both have oxygen poor mud

12. Coastal wetlands • Can filter water very well, .4 acres can filter 2,760,000 liters of water • They are being destroyed • 87 mil hectares to 43 mil hectares • Office of Wetland protection created to stop this

13. Lagoons • Lagoons lie between sand bars and land • Brackish • Salinity is high at the mouth but low at the head of the river feeding it • Can be hyper saline in arid regions

14. Marginal seas • Marginal seas are margins of the ocean semi enclosed isolated bodies of water • Mediterranean sea • Number of seas connected by small necks • Remains of Tethys sea • Contains an underwater ridge called a sill between sicily and Tunisia

15. Mediterranean circulation • Atlantic water flows on the surface to replace water evaporated in the arid eastern end • Water flows into the Atlantic at 200-600 meters of depth • The water cools to 13*C and 373% salinity as it passes though the Gibraltar • It then goes down to 1000 meters and equalizes wih surrounding water • Mediterranean circulation is where surface water from the ocean replaces evaporated water in the mediterranean

16. Marginal seas • Marginal seas of the Atlantic • Mediterranean • Caribbean sea • Gulf of Mexico • Marginal seas of the Pacific • Gulf of California • Bering Sea

17. Marginal Seas • Marginal seas of the Atlantic • Red sea • Arabian sea • Bay of Bengal