Transcript Coastal Waters and Marginal Seas

Coastal Waters and Marginal
Seas
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
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
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
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
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
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
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
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
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
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
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
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
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
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
Marginal seas
 Marginal seas of the Atlantic
 Mediterranean
 Caribbean sea
 Gulf of Mexico
 Marginal seas of the Pacific
 Gulf of California
 Bering Sea
Marginal Seas
 Marginal seas of the Atlantic
 Red sea
 Arabian sea
 Bay of Bengal