Geography Revision – Test 16/04
Oceans and Their Coastal Margins
Key Terms
Advancing coasts – depositional coasts that arise from a fall in the sea level and grow due to sediment deposit.
Exclusive Economic Zone – an area extending up to 200 nautical miles off the shore of a country, where, said country has complete sovereign rights over all economic resources in that area, whether they are located on the sea, seabed or subsoil.
Littoral Drift – movement of sediment along a coast by wave action.
Oceanic Conveyor Belt – global thermohaline circulation, driven by the sinking of deep water and responsible for the flow of upper ocean water.
Retreating Coasts – formed by erosional processes and a sea level rise, results in coastlines moving inlands.
Humans X Coastal Margins
Mutual destructive effect
TOURISM and POLLUTION compromise the SUSTAINABILITY of the environment
Leads to CORAL BLEACHING, and death of BIODIVERSITY
Reduced through COASTAL and SUSTAINABLE MANAGEMENT
Aggravation of CLIMATE CHANGE and GLOBAL WARMING, leads to rise of the sea levels, disappearing with BEACHES, invading CONSTRUCTIONS along the RETREATING COASTS.
* Earth’s surface = 70% oceans and seas
Northern hemisphere: 50%
Southern hemisphere: 90%
Regulation of Climate Conditions by Oceans
Oceans regulate climate conditions through the cold and warm currents.
Warm currents move water to colder areas, away from Equator.
Cold currents move water to warmer areas.
Warm Gulf Stream moves warm water towards the British Isles, making the coasts warmer and contributing to the rainy weather, as there is more evaporation.
Great Ocean Conveyor Belt
* “Thermo” = temperature // “Haline” = salinity
* Cold saline deep current carries dense cold water towards the Pacific, Atlantic and Indian oceans, while the surface currents carry warmer water on top and colder at the bottom
* Cold winds disperse heats towards Europe (Gulf Stream), and the water evaporates. However, the water left behind is saltier and denser, and sinks, being carried towards the Pacific.
* Warm water to the Atlantic North from Pacific and Indian oceans.
Ocean Water: Salinity and Temperature
Salinity = how salty the water is.
Less salt: precipitation (dilutes), areas where rivers discharge (fresh water dilutes salty one), thawing of large icebergs.
More salt: evaporation (makes it more concentrated), freezing (increases salinity temporarily, water between ice crystals are salty).
- E.g.: Mediterranean Sea has high salinity as there is lots of evaporation, low contact with freshwater and almost none with ocean water; Artic and Antarctica oceans have low salinity levels as icebergs melt and fresh water mixes with ocean water, decreasing salinity.
- The Conveyor Belt affects salinity. The cold salty subsurface flows carry the salt until it starts to rise, making the surface water salty as well.
- Temperature = disrupted spatially due to global latitudes.
Western sides = colder water
Eastern sides = warmer water
Latitude 0: high temperatures & low salinity (high evap. and high rainfall)
Latitude 30: high temperatures & high salinity (high evap. and low precipitation, where deserts are located)
Latitude 60: low temperature and moderate high salinity
Deep ocean: denser and saltier water sinks, high salinity, low temperature
Surface: temperature rises, so there’s more evaporation and therefore, more salinity
El Niño and La Niña
Complex weather patterns resulting from variations of temperature in the Pacific Ocean.
Normal Conditions: southeast trade winds move from east (high pressure) to west (low pressure) across the Pacific Ocean. The air rises in low pressure systems and creates a lot of rainfall in the west side. The wind then falls at the area of high pressure in the east.
El Niño: The trade winds slow down, making the warm water in the west spread back towards the east. The trade winds weaken and break down, inversing direction according to the areas of low and high pressure, creating rainfall at the low pressure area (east). High rates of rain, storms and flooding are created from California to South America.
La Niña: La Niña is simply an intensification of the normal conditions. Trade winds blow more intensely, and even more cold water is pushed towards the west. Additionally, the cold upwelling increases along the coats of South America.
El Niño Effects: 1997 – 1998
China: drought affected 20 million hectares of arable land in the north. Grain harvest threatened by flooding.
Africa: damage to corn crops in sub-Saharan Africa.
Indonesia: world’s third largest coffee producer’s crop down 25%. Hurricanes.
U.S.A: during the first three months, there is less precipitation in the Southwest, and Florida. More precipitation across the pacific Northwest. The latter has unusually cold weather.
Ocean Currents and Climate
* They are controlled by the Earth’s rotation (direction of rotation) and land masses (diameter). The winds keep them in rotation, and it does not happen in the equator.
- Corioles Effect: equator moves faster, so on each tropic, the motion goes to the opposite of the other.
Ocean Morphology
Continental Shelf: flat seabed that stretches from land to continental slope.
Continental Slope: steeply slopping seabed from continental shelf to abyssal plane.
Abyssal Plane: Large, flat are of sea floor located on edge of continental slope.
Ocean Trenches: Arc-shaped depressions in ocean floor caused by subductive plates.
Sea Mountains: extinct volcanoes below ocean surface.
Volcanic Islands: Sea floor volcanos break surface of oceans.
Guyot: Flat topped volcanos that once emerged but later subsided.
Ocean Resources
CARBON CYCLE
The transport of carbon along the planet.
Expelled to the atmosphere in form of CO2 by forest fires, deforestation, the surface of the ocean and pollution.
Trees absorb some of it through photosynthesis, however, since the human emission of CO2 is much bigger, when the tree tissue dies and falls, high levels of carbon are absorbed into the soil.
Meanwhile, in the ocean, the carbon in the surface is absorbed by marine life.
Those, when dead, dissolve organic carbon into the deep ocean that can be transferred into sediments. Though most of it goes back to the surface ocean, when the cycle begins again.
OVERFISHING
Hunt for smaller fish affect the availability of types of fish consumed by people.
World’s fish stocks are declining, and some have become extinct.
Cod stocks in North Sea are less than 10% of the 1970 levels.
GRAND BANKS, NEWFOUNDLAND: due to overfishing in 1992, it was closed so that cod’s populations could recover. It is still closed.
Too many fishermen too few and immature fish
To protect fisheries and keep fish industries going = less people in fishing
Increasing capacity of boats waste of money
Threats to the World’s Oceans
PLASTIC
Pacific: 3.5 tons of plastic
GREAT PACIFIC GARBAGE PATCH
80% = lands, the rest from ships
70% of trash sinks, the rest builds up at bays
Concentration of chemicals rise
Virtually indestructible
DEAD ZONES & RED TIDES
Most of large fish in shallow coastal areas have been caught
Toxins becoming more frequent
Red tides forming dead zones
RADIOACTIVE WASTE
WASTE ON MARINE ENVIRONMENTS
Oceans being used as dust bins
80% of marine pollution comes from land-based stuff
10% of waste are heavy metals
Mercury affects tuna, seals polar bears, others.
CASE STUDY: Guanabara Bay
OIL POLUTION
Bunker oil = ships, dirtiest of oils, more CO2
Regularly contaminates coasts
Toxic effects on benthic communities on the floor of seas
CASE STUDY: Gulf of Mexico 2011
COMBATING THE THREATS
Stricter regulations; Limit agricultural pesticides; Better sewage systems; Sustainable systems.
Hard for people to break their habits
Industries and governments are not the only ones responsible
Buy more environmentally friendly products = industries can turn to
Processes of Coastal Erosions
Hydraulic Action: air becomes trapped in joints between rocks, and creates pressure as it compresses, eroding the cliff.
Abrasion: wearing away of cliff by materials hurled against it by waves.
Solution: acids contained in water corrode the base-rich rocks.
Attrition: waves smash rocks and pebbles against each other, making them smaller.
Sub-aerial Processes: weathering on coast line above sea level due to wind and frost.
Wave Pounding: waves hit the base of cliffs causing undercutting and formation of wave-cut notches.