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39 Cards in this Set
- Front
- Back
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What is the meridial ocean circulation? |
a global circulation system which connects the world's ocean. |
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What drives the thermohaline circulation? |
Wind, water density variations created by surface heat and freshwater fluxes |
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Why is the thermohaline circulation important? |
Carries heat from tropical Atlantic to higher latitudes, ventilates deep ocean, redistributes oxygen, pH, carbon |
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What is seawater density a function of? |
Seawater density is a function of temperature and salinity |
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What is an isopycnal? |
It is a contour of equal density |
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What is the average density of seawater? |
1025-1028kg/m3 |
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What is potential temperature? |
Potential temperature is the in situ temperature corrected for the effect of compression |
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What is a polynya? Why important? |
A polynya is an area of water in the sea surrounded by ice. Antarctic bottom water forms there |
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What part of the globe does the Coriolis effect have the biggest affect? |
At the poles |
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What is a geostrophic current? |
Variations in sea surface height generates horizontal pressure gradient forces. This makes water flow around a "hill" not down it |
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What is westward intensification? |
A phenomenon of the Coriolis effect. Westward intensification creates fast, deep, narrow western boundary currents (gulf stream) and shallow, slow, wide eastern boundary currents (Canary current) |
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What cuases vertical circulation of waters? |
convergences and divergences. Divergence of Norwegian current causes upwelling of nutrient rich deep water |
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What is an isohaline? |
Line joining point of equal salinity |
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What is the thermocline? |
the section of the temperature profile where temperature changes very rapidly |
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What is the mixed surface layer? |
The surface section where tempreature shows little variation with depth aprox 10-300m |
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How does seasonality of thermoclines (or lack of) affect nutrient cycling? |
The Tropical Atlantic has a permanent thermocline so nutrients at depth are not recycled into surface layer. Northern area has seasonal one which breaks down over winter allowing nutrients from deep water to be recycled to surface |
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How does climate change impact oceans? (3 things) |
1. Increased water stratification 2. Decreased vertical mixing/overturning of surface waters 3.Decreased primary production |
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Where does salt fingering occur? |
Where warm fresh waters overlie cold fresh waters. May mix h20 faster than local turbulence. |
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If warm salty water overlies cool, fresh water what will happen? |
T is stabilising but S is destabilising. T will diffuse faster and will become constant throughout. S will remain unstabilising and waters will overturn and mix = water column unstable |
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If cool fresh water overlies warm salty water what will happen? |
This may occur at high latitudes. T will diffuse fast and soon become constant. Salinity will remain at depth= water column will be stable |
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What will happen when warm fresh water overlies cool, salty water? |
Both T and S stabilising. Water column stable |
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How long does it take water to move from start of Meridional journey (N Atlantic) to upwell in Pacific? |
aprox 1000 years |
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What is main source of Al and Fe in seawater? |
aeolian dust |
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How do conservative elements behave? Examples? |
Their concentrations are constant with depth, and in different oceans. Na+, Cl- and non-major elements which usually have only weak biological reactions are not particle reactive and are relativly soluble |
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How to nutrient-type elements behave? |
the concentrations of these elements are controlled by biological cycling. Profiles are depleted in surface watrs and then increase again at depth. |
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How do scavenges elements behave? |
These elements show concentration decrease with depth. Scavenged elements are v partical reactive, have short residence times and show high variability between oceans. Al is quickly absorbed. Residence time= 200 years |
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What is the Intertropical convergence zone? |
the ITCZ is the area where the Northern and Southern trade winds meet. It is an oceanic divergence and causes upwelling |
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What is oxygen compensation depth? |
The depth at which light intensity declines and respiration and photosynthesis balances. Below this respiration dominates |
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Why does oxygen increase again at depth? |
Cold, oxygen rich deep waters formed at poles contribute |
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Is the oxygen concentration higher in Atlantic or Pacific? Why? |
More oxygen in Atlantic deep waters. Because Pacific deep waters are older so more particles have died and sunk, using up more oxygen |
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Where is climate-change induced oxygen decline most intense? |
Tropical Atlantic |
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What is causing oxygen minimum zone expansion? ( 4 things) |
1. Reduction in convective mixing from surface (increased stratification) 2. Reduction in deep water subduction ( due to decreased deep water density at formation sites) 3. Reduction in 02 solubility in warmer surface waters 4. Increased 02 consumption from organic decay at depth |
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What does the equilibrium constant define? |
The equilibrium constant defines the ratio of the concentrations of the products and reactants in a reaction at equilibrium |
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What would happen if we double atmospheric C02? |
we produce bicarbonate and protons, decreases carbonate |
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Total carbon higher in Pacific or Atlantic? |
Pacific. Waters older so more time for carbon from respiration to accumulate |
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Will solid calcium carbonate be better preserved in Atlantic or Pacific? |
Atlantic. Because pH is higher in Atlantic |
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What is the lysocline? |
depth at which CaCo3 dissolution begins. |
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Why is preservation of calcareous sediment become less likely in the Pacific? |
Because Co3 2- decreases from N Atlantic to N Pacific and as ocean depth increases due to increase in acidity |
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Which is more soluble: calcite or aragonite? |
Aragonite. Thats why modern corals are F***ed |
