Oceans Flashcards
How much of earths surface is covered by ocean
71%
How much of earths water does oceans holds
97%
What controls the climate and weather on earths surface?
The interactions between the oceans and atmosphere
What are oceans responsible for?
Oceans are responsible for keeping conditions on the earth steady
Name all 5 major oceans
- Pacific
- Atlantic
- Arctic
- India
- Southern ocean
How can the effect of oceans on climate be measured
The effect of oceans on regional climates can be measured by comparing annual air temp at different latitudes
What are the most important bathymetric features of the sea floor?
- Continental shelf - thinning continental crust
- Slope and rise - transition between crust types
- Abyssal plains
- Oceanic ridges
- Oceanic trenches
How old is the ocean?
- Relatively young due to subduction of oceanic crust
- Oldest areas are ones furthest away from ridges
What is the geology of the ocean crust?
- Formed at sea floor spreading ridges from magma
- 10% of the mantle rock melts producing magic magma
- 50% silica (forms pillow basalts, breccia and flows
- Beneath is gabbros - formed through the cooling of magma under the crust
Describe oceanic sediment
- Thickness increases away from oceanic ridges
- Various sediment sources depending on the proximity to continent, water depth, currents, bio activity and climate
- Terrigenous - material eroded from land
- Pelagic - living organism shells - carbonate and silica
- Volcanic ash
Where is oceanic sediment distributed?
- Terrigenous - close to continents - from deltas
- Red clay - located near shore environments
- Silica - southern polar regions and equator in pacific
- Carbonate - cannot be lower than 4000 as it will dissolve
Why do humans retrieve deep sea sediment cores?
- Gives us information about the climate in the past
- Retrieved using drilling, majority of oceans have been drilled
Why is sea salty?
The dissolved ions have been concentrated in sea water as a result of chemical weathering and the degassing of the mantle volcanic activity
Why does salinity vary in the ocean?
surface waters evaporate, rain and stream water is added and ice forms and thaws
What are the different depths of the ocean divided into?
Divided into areas based on temp and density
- all zones based on horizontal distance from continental plate
How far does the sun penetrate into the ocean
only penetrates 200m of ocean water
What is the photic zone?
- The top 200m of the ocean
- Important for marine wildlife
What is the aphasic zone?
- Not enough light for photosynthesis
- Makes up majority of ocean water
What are the 4 primary factors that control ocean circulation?
- Water salinity
- Water temp
- Surface winds
- Coriolis effect
What is ocean circulation a major component of?
The climate system through the distribution of thermal energy
What is surface ocean circulation primarily influenced by?
- Winds - controlled by atmospheric circulation
- Earths rotation
What is thermohaline circulation (THC)
The movement of sea water in a pattern of flow dependent on variations in temperature, which give rise to changes in salt content and hence in density
What is deep sea circulation primarily influenced by?
- Density (temp and salinity)
- Position of land masses
What is the oceanic circulation system?
- Global conveyer
- Driven by changes in water temp and density
- surface flow of North Atlantic dominated by Gulf Stream
- Warm salty water driven northwards by prevailing winds
- Water cools and density increases and sinks near South Greenland
- This feeds the North Atlantic Deep Water (NADW)
- Current flows southwards to compensate for North flowing Gulf Stream
- Tother them comprise the Atlantic Meridional Overtiming Circulation (AMOC)
Outline AMOC
- Water evaporates near tropics
- E-W trade winds precipitate it init pacific
- Salinity increases in Atlantic and decreases in pacific
- Causes warm, salty Gulf Stream
Outline NADW
- Surface water cools (denser)
- Forms sea ice - becomes saltier (denser)
- Sinks
What are the stages of Broeckers (1990) Salt Oscillator Hypothesis?
- Injection of fresh water into N Atlantic reduces surface water density
- sinking no longer takes place
- AMOC slows down/shuts down
- reduces northward heat transfer via Gulf Stream
- Northern hemisphere ice sheets grow
- salt content gradually increases (evaporation) as salty water is not removed from from the Atlantic
- As salt accumulates, it gradually increases density until AMOC is able to start again
- Positive feedback mechanisms
What happens during times of NADW formation?
- Ice melting dilutes salinity of North Atlantic
- Eventually slowing or stopping NADW formation
What happens when NADW does not form?
- Less salt removed and little heat transported north
- Ice sheets stop melting
- North Atlantic gets salty and NADW starts to form again
