oceans

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  • Oceans
    • distinctive features
      • continental shelf-av. width 70km. shallow gradient 2m/km
      • continental slope-av. width 16km steep gradient 70m/km
      • continental rise- gently sloping zone
      • abyssal plain-vast, relatively flat areas make up half the earths surface
      • seamounts-chains of mountains and isolated peaks some rising 3000m from abyssal plain
      • guyots- flat topped peaks that were once above the surface but erosion reduced them below sea level
      • mid ocean ridge- long chains of mountains crossing the abyssal plain, rift valley along the centre of the ridge
    • Horizontal and vertical variations in ocean water
      • salinity in sea 35ppt-higher towards the tropics and lower towards the poles. salinity decreases with fresh water inputs from rivers, precipitation into ocean and when ice melts.
        • Halocline- sharp change in salinity form surface to 750m
      • temperature-oceans act as reservoirs for heat energy. below surface is the thermocline- sharp change in temp with depth from below the surface to 1000m
      • warm and cold ocean surface currents-warm water flows north and south from low latitudes to the middle and high latitudes- transfer vast quantities of heat energy- key to influencing climates
        • gyres are generated by winds e.g Atlantic and Pacific are north and south gyres
      • circulation in the North Atlantic-from gulf of Mexico a warm surface current (gulf stream) moves north. it flows north of Arctic circle, its temp and density fall so the current sinks. a deep cold water flows back towards the low latitudes.
    • changes in factors influencing biodiversity
      • light and temp- as depth increases, temp and light decreases. photosynthesis takes place in the photic zone-50m. some animals use bio luminescence to capture or evade prey. light levels are highest at equator and decrease with distance away from equator
      • nutrient levels-rivers transport nutrients from land to oceans.            marine organisms use nutrients of they sink as 'marine snow'. remain deep- snow forms basis of deep water ecosystems. sometimes water movements bring nutrients to the surface .
        • some bacteria fix the energy from hydrothermal vents and communities develop around the- not dependent on suns energy
      • ocean biodiversity- oceans are home to 80% of all life on earth. food chains develop from organisms such as phytoplankton which converts suns energy into chemical energy. large parts of the deep ocean are unproductive. Coastal shelves have high NPP and so do large seaweeds such as kelp
      • Antarctic deep-water ecosystem- salt is expelled from sea ice into surrounding water--> more saline= more dense-->very cold saline water at surface sinks-->less salty, less dense water rises carrying nutrients--> phytoplankton use this to grow--> krill eat phytoplantom--> whales eats krill
      • salt marsh inter tidal ecosystem- coastal wetlands are common in mid to high latitudes. rivers supply sediment to saltmarshes which helps them develop. high NPP and they are important to migratory birds
    • biological resources, sustainable/unsustainable
      • value of resources-biological resources are part of natural capital of oceans
      • whales case study
        • IWC-created a moratorium that 88 states have agreed- caused by whale numbers decreasing. set whaling catch limits
        • used for: food, commercial whaling, ribs used for construction materials, blubber used for lamps.
        • Stakeholders
          • IWC- want to conserve whales- global body 88 members
          • Aboriginal- don't seek profit, subsistence-rely on them for meat, don't affect whale numbers- don't catch many
          • Japan- commercial whaling- not part of IWC. within their culture they eat whale, very profitable. Often lie about scientific research and continue to commercial whale catch. 333 whale quota
          • Norway- only respected the IWC ban till 1993- resumed hunting Minke whales, sets own quota of 1000 whales. hunt for breading females and could put strain on Minke population
          • Iceland- similar to Japan, conducted 'scientific research' in 2010 killed 148 endangered Fin whales and 60 Minke whales
        • Blue whales have seen and 8% increase in southern hemisphere, grey whales critically endangered- less than 30,000 left, Antarctic Minke whales are endangered but protected
    • ocean energy and mineral resources
      • non renewable oil and gas: Gulf of Mexico- offshore drilling for 70 years. 40.000 km of pipelines
        • positives: employment opportunities-240,000 jobs related,wealth creation, rigs act as artificial reef, increasing local marine species-coral, fish, sharks
        • negatives: over dependence of local communities on this one industry, visual impact, oil spills, ecosystem disturbance-lots of noise
      • renewable:75-80% of energy is from fossil fuels
        • tidal energy- energy comes from the rise and fall of the tide - power depends on physical geography , tide spins rotas which turn a generator and provides electricity
          • Swansea bay- £300 million, 2000 jobs,sea wall 9.5km long, lagoon 12km2, power 155,000 homes
            • advantages: renewable, does not emit climate gases, predictable unlike solar, jobs, educational for all levels, farm for oysters and kelp- local produce,sports can take place- better quality of life
            • negatives: environmental effects are not determined, close to land so could spoil the view, sediment movements in Swansea bay,water quality due to limited flows
        • wave energy- wave creates hydraulic pressures, which drive electricity generators- large equipment to be robust, looses
      • sea floor mining- ferrous and non ferrous metals mineral deposits.
        • REEs are important to technology e.g mobile phones- humans rely on them, geo political issue. China dominates production- concerns for USA, Japan and Europe
        • ROVs survey an sample sea deposits in Pacific Ocean- geopolitical concerns influence whether permission in EEZs
        • concentration of minerals around mid ocean ridges and hydrothermal vent- don't know the damage it could cause some ecosystems. Tailings can smother coral
    • Governing the oceans poses issues for management
      • UNCLOS defines  marine rights and responsibilities
        • Territorial waters- country has complete control over all activities
        • Contiguous zone (3) country has sovereignty and legeal rights e.g rules about waste disposal
        • EEZ (12 or 24) country has rights to control sea beds and water resources but sharing allowed in some situations, all countries have rights to fly or sail over area, unresolved issues about fishing in Europe
        • High seas (200 nautical miles) outside the sovereignty and legal rights of a single country, certain international agreements apply
      • most countries have signed convention but issues persist in some locations over who owns what e.g fish+ minerals. also issues that weren't covered by the agreement like ocean acidification.
      • Marine reserves-3% of the worlds oceans are marine reserves
        • Chagos marine reserve- surrounded by the cleanest sea water in the world, 2x the size of Britain, worlds largest coral, reefs have rebound climate change, 800 species of fish, 50 types of shark
          • Benefits: offer training to local communities so they can add to marine research, scientific research, vast coral reefs due to little human involvement, can investigate effects of climate change without human interference, contributes to the globally agreed target that 10% of oceans will be protected by 2020
    • Human activities that pollute the ocean
      • fossil fuel burning at sea- shipping relies on burning fossil fuels. 90,000-100,000 cargo ships. Burn cheap low quality fuel- high in sulphide 5,000 tonnes of sulphur a year.
        • ships at ports threaten human health air pollution in 2-3x higher in places with ports. fuel efficiency is being increased, improved ship design
      • Domestic and industrial pollutants- rivers discharge chemicals into sea or fall via rain. however coastal waters around ACs have improved however large amounts of pollutants are released into rivers and sea in LIDCs
        • Algal bloods- sign water has deteriorated. algal flourishes in nitrates, phosphates from fertilisers or detergents.
      • Nuclear waste- 20th century, thought nuclear waste was suitable for nuclear waste. there are also nuclear submarines in which their shields will disintegrate and release radioactive material
    • Deep water horizon case study-2010- 210 million gallons
      • Environmental impacts- 16,000 coastlines affected- leaked for 87 days, 8,000 animals( birds turtles mammals) died just 6 months after spill, 3,000 pelicans, food chains disrupted as birds could not get fish- fish and sea animals dies, dolphins and whales died due to oil exposure
      • social impacts- 11 people died, 8,000-12,000 temporally unemployed,$22.7 billion lost in tourism e.g hotel cancellations
      • economic impacts-fish died-not as many to sell, people helped clean up- tourists lost, fishing shrimp was banned due to intake of oil.

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