1. COASTAL OCEAN

2. • We will start with chapter 11 first, then chapter 10

3. Coastal ocean Shallow ocean area over continental shelf
Complex shorelines

4. Currents are more or less parallel to the shoreline
– 1. tides and winds have strong influence
– 2. affected by river discharge
– 3. estuarine circulation prevails (will see this later)
– 4. Davidson coastal: geostrophic currents (arises
from a balance between the down-slope component
of the gravitational force and the Coriolis effect
that deflects it) that parallel the coast (Fig 11.4 p 317)

5. Davidson coastal geostrophic circulation

6. Currents are more or less parallel to the shoreline cont.
– 5. seasonal change - summer wind diminish or
little river discharge, and weaken coastal currents -
winter storms - coastal currents are re-established

7. Example • surface waters can be blown toward shore and held there by winds, depressing the pycnocline (where water density changes markedly with depth - changes in either temperature, salinity or both, can cause the marked change in density). A sloping sea surface results, creating geostrophic currents that parallel the coast. Because of this parallel flow transfer of freshwater across the coastal ocean is slow - residence time of freshwater is long, 1/2 year to 2+ years

8. Words from previous chapters
1. pycnocline
2. geostrophic current
3. residence time
4. up welling
5. boundary currents
6. fetch
7. lagoon

9. Boundary currents Western boundary current - strongest in oceans
– 1. deep, narrow, swift
– 2. intensified by Earth's rotation
– 3. often meander and spin off rings that move
separately
Eastern boundary currents
– 1. broad, shallow, slow-moving
– 2. often associated with up welling areas

10. Up welling Up welling induced by winds or river
discharge cause nutrient-rich waters to
move into surface zone
Coastal up welling occurs along the
California-Oregon coast (good fishing) and
western coasts of South America (good fishing)
These waters usually come from about 200
meters depth (cold plus nutrients)

11. Temperature and salinity
Marked changes in temp and salinity along
coast and offshore due to winds (Fig 11.2, & 11.3
p 316)
Strong seasonal changes
– winter, cold winds bring on rain and lower
salinity
– summer, dry winds from the continent cause
evaporation - while blowing across coastal
waters increase salinity through evaporation

12. Temperature and salinity
Evaporation occurs from all oceans
Lowest salinity occurs near large rivers (Amazon
discharges fresh water about 1 mile out)
Extreme temperatures occur in surface
coastal waters - surface temp > 40o C
3 points:
– 1. no mixing - warm water on top of cooler
water

13. Temperature and salinity cont.
– 2. limited fetch (distance over which the wind
blows in a constant direction) in small ocean areas
limits wave action - inhibit vertical mixing
– 3. lower surface-water temperatures are
controlled by freezing sea water at -2oo C
large surface area - shallow bays and lagoons - low
salinity (river discharge)

14. Estuaries, fjords, and lagoons Fig 11.5 p 318

15. Estuary- a semi-inclosed body of water where
fresh water from the land mixes with saltwater -
found on stable (sinking Atlantic-type) margin a
– Formed by flooding of indentations along the coast
– Drowned river a valleys
– Coastal plain estuaries are typically broad, and
gradually deepen seaward

16. Coastal plain estuary

17. Drowned river a valleys

18. Estuaries, fjords, and lagoons cont.
Fjords - flooded glacially eroded high latitude coastlines b
– Glaciers removed the soil cover and carved
deep valleys and when these valleys were
flooded they formed fjords
– U shaped

19. Fjord

20. Estuaries, fjords, and lagoons cont.
Lagoon - wide shallow estuarine system
Bar-built estuaries separate shallow lagoons
coastal ocean c (barrier islands)
Review Fig p 65
Are seen commonly along the U.S. Gulf Coast and
much of the Atlantic coast up to Long Island

21. Lagoon

22. Estuaries, fjords, and lagoons cont
Where mountain building is active, and the
coast is rising, estuaries or bays d (tectonic
estuaries) are cut off from the ocean by young
mountain ranges. On such a coast, there are
few estuaries or lagoons. The Pacific coast of
North America is an example. (Rising Pacific
type margin)

23. Tectonic estuary

24. Estuarine circulation
Estuarine circulation - long term
Average flow seaward in the surface
layers and a net landward flow along
the bottom
Fig a, b, c, d p 319

25. Estuarine circulation cont.
Two-layered flow with sea-ward-moving
low-salinity surface water over landward moving
flow of higher-salinity water
Mixing between layers depends upon the
magnitude of river flow and tidally induced
mixing
Nutrients supplied from land and by estuarine circulation cause high productivity

26. Salt-wedge estuary Salt-wedge estuary Fig. 11.7 d p 319
friction between fresh and salt water - pycnocline
observed only where river flow is large and tidal range low – Columbia river during floods Fig p 320 (book)

27. Columbia river

28. Estuaries Vertically mixed estuary - (well mixed)
salinity at any point is uniform from the
surface to the bottom - river water mixes
evenly Fig a p 319
– shallow - low volume - little or no transport of
sea water inward

29. Estuarys cont. Slightly stratified estuary - (partially mixed)
two basic water layers - fresher on top,
increased salinity at bottom, with mixing in
the middle Fig b p 319
– deeper - salinity increasing from head to mouth

30. Estuaries cont. Highly stratified estuary - (Fjord type)
Fig p 319
deep water has uniform salinity
upper water increases in salinity from head
to mouth
relatively strong halocline

31. MARGINAL SEAS
partially isolated from coastal ocean – have varying degrees of exchange with the open oceans - salinity and temperature is different than those of typical sea water

32. Marginal seas of the Atlantic
1. Mediterranean Sea Fig a p 323 T 106
– a. number of small seas connected by narrow necks
– b. remains of the Tethys Sea that separated former continents of Laurasia and Gondwanaland
– c. opposite to the pattern characteristic of estuaries (where surface freshwater flow goes into the open ocean and saline subsurface flow enters the estuary) Fig b p 341

33. Marginal seas of the Atlantic cont.
2. Caribbean Sea T 107
– a. connects to Atlantic by way of the Anegada
Passage (very deep 2300 m)
– b. four major basins - Venezuela, Colombia,
Cayman, Yucatan depths > 4000m
– c. cold nutrient rich upwellings

34. Marginal seas of the Atlantic cont
3. Gulf of Mexico T 107
– a. connected to the Atlantic by way of the
Straits of Florida (1000m)
– b. Florida current - part of the Gulf stream
– c. Loop Current

35. Marginal seas of the Atlantic cont
3. Gulf of Mexico T 107
– Vertical Salinity in Caribbean and Gulf of Mexico T 108
a. saltier warmer water does not sink

36. Marginal seas of the Pacific
1. Gulf of California
2. Bearing Sea triangle shaped
– a. volcanic island arc of the Aleutians with a broad continental shelf T 109
– b. three domains
• 1. coastal 50 m deep and km from shore
• 2. middle 100 m deep km from shore
• 3. outer 170 m deep 500 km from shore T 110

37. 2. Bearing Sea triangle shaped cont.
– c. biological productivity T 111
– d. nutrient supply from upwelling T 112
– e. large phytoplankton biomass T 113

38. Marginal seas of the Mediterranean Area
1. Black Sea - estuarine like circulation T 106
– a. water flows in via several large rivers - Danube which drains
Central Europe (flowing generally eastwards for a distance of
some 2850 km (1771 miles), passing through several Central and Eastern European capitals, before emptying into the Black Sea via the Danube Delta in Romania.)
– b. high salinity (38.52) flows in from the Mediterranean Sea along
the bottom of the Bosporus (a narrow channel with a shallow sill)

39. Danube River Delta

40. Mediterranean Area
1. Black Sea - estuarine like circulation T 106 cont.
– c. low -salinity water (17.2) flows out in the surface
layers
– d. isolated bottom waters devoid of dissolved oxygen - only bacteria that use sulfite survive - SO2 + HOH -> usable O2 + H2S
– e. high hydrogen sulfide concentration

41. Mediterranean Area 2. Mediterranean Sea - convective currents
– a. strong evaporation -> high salinity (39) Fig.
11.12 b p 323
– b. Atlantic <=> Strait of Gibraltar : Black Sea -> Bosporus : Red sea -> Suez Canal
– c. no water from the Nile because of the dam – all other rivers are small

42. Mediterranean Area
2. Mediterranean Sea - convective currents cont.
– d. salty water from the Mediterranean causes the North Atlantic to have the highest salinity of any of the major ocean basins (salty Mediterranean water enters the Atlantic as subsurface water, while surface water from the Atlantic enters the Mediterranean)

43. Mediterranean Area 3. Red Sea - antiesturine circulation
– a. high salinity surface water (>40)
– b. narrow basin connecting to the Indian Ocean through a narrow opening at its southern end
– c. no large rivers empty into it
– d. circulation is controlled by winds which shift seasonally (monsoon)

44. Mediterranean Area 3. Red Sea - antiesturine circulation
– e. bottom of the Red Sea has hydrothermal
circulation in the newly formed ocean crust
– f. hot (60) and salty (257) these highly saline
brines are extremely dense and do not mix with
overlying waters
– g. still forming, plates separating

45. Coastal processes 10.1 p 286
Shoreline - where land, air, and sea meet - most dynamic
part of the ocean
– 1. shaped by tides, winds, waves, changing sea level, and humans
– 2. storm surges - relatively sudden large changes in sea level resulting from strong winds blowing across a shallow and partially enclosed body of water
cause flooding with wide changes to shoreline
occur only every few decades or even centuries

46. Coastal processes cont.
– Shoreline cont. – 3. glacier retreats and advances resulted in sea level changes - if the glaciers in Antarctica and Greenland melted the sea surface would be as high as 50 meters above its present level

47. Coastal processes cont.
Coastlines
– Some are formed mainly by terrestrial processes – increased water level
1. drowned river valleys
2. fjords
– Volcanoes
1. island of Hawaii
2. crater that has lost the seaward portion of its rim
3. See next slide

49. Coastal processes cont.
Coastlines cont.
– Bluffs are eroded and deposited near shore
– Barrier islands and spits - sand is moved along
coasts by long shore currents Fig p 288
– Waves in the surf zone produce a long-shore
current that transports sediment - arrows
indicate on-shore and long-shore water
movement Fig 10.3 p 288
– wave rays perpendicular to wave crest p 247

50. Coastal processes cont
Beaches - sediment deposit in motion Fig p 304
– 1. sand beaches, barrier islands, and bays boarder the U.S.
Atlantic Coast from New York to Key West, Florida
– 2. barrier islands and lagoons on Gulf Coast Fig p 293 in book and migration of barrier islands Fig p 295
– 3. sediment supplied by rivers or by erosion of bluffs Fig.
10.4 p 289
– 4. moved by wave action or tidal currents Fig p 288

51. Coastal processes cont.
– 5. dynamic relationship between beach and offshore deposits
beaches are accumulations of locally abundant materials
not immediately removed by waves, currents, or winds
– 6. kinds of beaches - sand, bolder, lava, gravel
– 7. Some anatomy of the beach Fig p 286
a. berm - highest part of the beach
b. dunes - formed by beach sands blown by prevailing winds and colonized by salt tolerant plants (Spartina)
c. deposits – Fig p 292

52. Coastal sand dunes and Spartina sp.

53. Coastal processes cont.
Seasonal beach changes Fig 10.2 a,b p 287 in book S&A 138 Table 10.1
– summer beach
– winter beach

54. Barriers on the beach
– Fig p 305
– Fig p 306

55. Fig p 307 Sea Wall

56. Delta
– deposit of river borne sediments discharged into the ocean (read this in the book p 296)
– 1. supply exceeds transport of sediment away from river mouth
– 2. usually areas of low tidal range and little wave action

57. Delta cont. • 3. Making of a delta – a. river/estuary
– b. excess sediment
– c. marsh and estuarine deposits of sediment
– d. marshy coastal plain
– e. distributaries - small stream flowing away from a main stream (characteristic of deltas)

59. Drainage basin of the Mississippi River and its major tributaries
Drainage basin of the Mississippi River and its major tributaries. The basins for the Headwaters (in Minnesota) and the Upper Mississippi River reaches are combined on the map.

60. Salt marshes
low-lying areas, protected from wave action Fig p 325 book
– 1. usually submerged at highest tides
– 2. generally covered by salt-tolerant grasses and other plants
– 3. last stages in sediment filling of coastal
indentations

61. Salt marshes cont.
– 6. cut through with channels for water flow (tidal) – 7. nurseries for over half the species of commercially important fish in the southeastern United States – 8. filter pollutants

62. Salt marsh

63. Mangrove swamps tropical areas where mangroves dominate marshes
– 1. restricted to latitudes below 30 
– 2. once established, they normally out grow and replace marsh grasses, first mangrove trees are red -> Black -> White
– 3. pneumatophores - roots above water, allows O2 to
enter the plant systems
– 4. the loss of the mangrove trees allowed the tsunami of
2004 to penetrate further in land than it would have if the mangroves were allowed to remain

64. Mangrove

66. Location of mangroves 30oN - 30oS