MAR 110: Lecture 10 Outline – Oceanic Conveyor Belt
MAR 110 LECTURE #10
The Oceanic Conveyor Belt
“Oceanic Thermohaline Circulation”
Ocean Climate Temperature Zones
The pattern of approximately parallel oceanic surface
isotherms (lines of constant temperature) reflects the
equator to pole solar heating contrasts. (?)
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MAR 110: Lecture 10 Outline – Oceanic Conveyor Belt
Surface Ocean Heat Transport
The latitudinal deviations in the isotherms reflect the effects
of ocean surface currents, which consist of clockwise gyres
with particularly intense currents along the western
boundaries in northern hemisphere ocean basins
(counterclockwise in the southern hemisphere ocean
basins). The arrows show the effect on the surface
temperature field by both the Gulf Stream and the Brazil
Currents, which transport warm water from the equatorial
region towards the poles. (??)
Wind-Driven Surface Ocean Currents
The juxtaposition of the zonal winds – trades, westerlies and easteries –
produces gyre circulations with intensified western boundary currents in the
major ocean basins – the North & South Atlantic, North Pacific , and Indian
Ocean basins. (LEiO)
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MAR 110: Lecture 10 Outline – Oceanic Conveyor Belt
The World’s Oceans –
A Bartholomew projection of the geography of the oceans . Nearly
three-fourths (72%) of the Earth’s surface is covered by
oceans
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MAR 110: Lecture 10 Outline – Oceanic Conveyor Belt
The Oceanic Conveyor Belt Moves Heat Poleward
The oceanic conveyor belt consists of (1) sinking in the North Atlantic polar
region - as the ocean gives up its heat to the atmosphere- (2) deep
southward transport of the colder water to the Southern Ocean around
Antarctica, (3) distribution to the Indian and Pacific Ocean basins (4)
upwelling primarily along the equator, and (5) surface flow returning to the
North Atlantic via a series of intensified western boundary currents caused by
the surface winds (CCaMA)
The Oceanic Conveyor Belt - ON
The oceanic conveyor belt consists of (1) sinking in the North Atlantic polar
region - as the ocean gives up its heat to the atmosphere- (2) deep southward
transport of the colder water to the Southern Ocean around Antarctica, (3)
distribution to the Indian and Pacific Ocean basins (4) upwelling primarily along
the equator, and (5) surface flow returning to the North Atlantic via a series of
intensified western boundary currents caused by the surface winds. (CCaMA)
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MAR 110: Lecture 10 Outline – Oceanic Conveyor Belt
The Oceanic Conveyor Belt - OFF
In this configuration the oceanic conveyor belt the sinking component
disappears because fresh water and ice inhibit sinking in the polar North
Atlantic. Only the wind-driven warm surface flow remains. (CCaMA)
Ocean Surface Temperature Distribution - NH Winter (??)
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MAR 110: Lecture 10 Outline – Oceanic Conveyor Belt
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Salinity
Salinity is the term used to reflect the ‘saltiness’ of the water. Salts (and other constituents of
ocean water) are derived from erosion of continental land masses slowly being carried into the
ocean with river water. Eventually these salts became concentrated in the ocean and are now in
a steady state (loss of salts to sedimentation and other processes equals the input of salt from
river discharges). Many factors may affect the local salinity value in the ocean, including
evaporation, precipitation, river input, and mixing between two water masses. Salinity is
measured in units of parts per thousand (ppt).
MAR 110: Lecture 10 Outline – Oceanic Conveyor Belt
Ocean Density Sensitivity to Temperature (T) & Salinity (S)
The density of the ocean varies with respect to both temperature (negative relationship) and
salinity (positive relationship).
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MAR 110: Lecture 10 Outline – Oceanic Conveyor Belt
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Ocean Surface Salinity Distribution
Graph of evaporation and surface salinity as a function of latitude (top). Map of surface
salinity distribution over the globe (bottom). Note that regions with increased
evaporation also have higher levels of salinity. (??, ??)
Ocean Temperature & Salinity & Density Profiles
The changes of temperature, salinity, and density with increasing depth. The –clines are regions
where the particular property in question (temperature, salinity, or density) changes rapidly with
depth. (ItO)
MAR 110: Lecture 10 Outline – Oceanic Conveyor Belt
An Atlantic Ocean Density section (??)
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MAR 110: Lecture 10 Outline – Oceanic Conveyor Belt
Global Ocean Thermohaline Circulation
A rough schematic cross section of circulation between the poles. Cold
water at the poles becomes dense as it cools and sinks to a depth
dependant on the density with the coldest and densest water sinking
the deepest. As the water warms it becomes less dense and rises.
(??)
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MAR 110: Lecture 10 Outline – Oceanic Conveyor Belt
A Two Layered Atlantic Ocean
Cold water at the poles becomes dense as it cools and sinks to a depth
dependant on the density with the coldest and densest water sinking the
deepest. A surface layer of warm, less dense water exists nearer the equator,
separated from the deeper and colder water by the pycnocline, an area where
the density changes rapidly with depth. (ItO)
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MAR 110: Lecture 10 Outline – Oceanic Conveyor Belt
Atlantic Ocean-Deep Western Boundary Current (DWBC)
The DWBC is a current that originates in the Norwegian Sea as very cold and
dense water that travels along the deep sea bed towards the south. (??)
Gulf Stream & the Deep Western Boundary Current off of Cape Hatteras (BG)
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MAR 110: Lecture 10 Outline – Oceanic Conveyor Belt
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The Oceanic Conveyor Belt Moves Heat Poleward
The oceanic conveyor belt consists of (1) sinking in the North Atlantic polar region - as the
ocean gives up its heat to the atmosphere- (2) deep southward transport of the colder water to
the Southern Ocean around Antarctica, (3) distribution to the Indian and Pacific Ocean basins
(4) upwelling primarily along the equator, and (5) surface flow returning to the North Atlantic via
a series of intensified western boundary currents caused by the surface winds. (CCaMA)