Transcript OCEAN STRATIFICATION - CCE LTER | California Current …
OCEAN STRATIFICATION
SURFACE AND DEPTH SALINITY VARIATIONS
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Surface variations
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Varies with latitude
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Lowest at high latitudes
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Highest at tropics of Cancer and Capricorn
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Dips near the Equator
Surface Variations
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Why vary at the surface?
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High Latitudes: low salinity
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Lots of precipitation
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Melting of ice
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Runoff
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Limited evaporation
Surface Variations
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Why vary at the surface?
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Tropics of Capricorn and Cancer: High salinity
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Warm air descends here
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Evaporation rates are high
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Little precipitation
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Little runoff
Surface Variation
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Why vary at the surface?
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Equator:
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Warm temperatures
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High evaporation rates
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Increased precipitation
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Increased runoff
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Kind of offset one another
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Depth Salinity Variation Low latitude regions
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High salinity at surface
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Dips to intermediate level with depth High latitude regions
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Low salinity at surface
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Goes to intermediate level with depth
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Approaches value of low latitude version at depth Salinity varies little with ocean depth
The Halocline
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Rapid change in salinity with depth
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Between 300m – 1000m Low latitude:
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Curve is a decrease in salinity High latitude:
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Curve is an increase in salinity
SEAWATER DENSITY
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Pure water = 1.000g/cm 3 at 4°C Seawater:
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Dissolved substances increase density
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1.022 – 1.030g/cm 3
The ocean is layered
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Ocean Stratification
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Lower density floats on top
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Higher density at bottom
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Density is affected by… Temperature:
– Density increases as temperature decreases – Greatest influence
Salinity:
– Density increases as salinity increases – Has more effect at poles
Pressure:
– Density increases as pressure increases – Least effect
Density curves – low-latitude
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Density remains fairly constant till 300m
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Good surface mixing from currents, waves and tides Below 300m:
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Density increases rapidly with depth to 1000m Below 1000m:
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Density remains constant
Density curve – High latitudes
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Very little variation with depth High density at surface – low water temp
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High density below the surface –low water temp
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Straight line
Pycnocline and Thermocline
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Pycnocline:
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Layer of rapidly changing density with depth Thermocline:
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Layer of rapidly changing temperature with depth Typically occurs between 300-1000m
Thermoclines in High Latitudes
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Cold year round surface water Thermocline and pycnocline rarely develop
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Only during the short summer
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Long days of sunlight
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Stays isothermal and isopycnal
Why is it important?
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Pycnocline=barrier to mixing
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Results from combined effects of halo and thermoclines
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Results in a layered ocean