Gulf stream, recirculation, and other western boundary layer currents

download report

Transcript Gulf stream, recirculation, and other western boundary layer currents

Gulf stream, recirculation, and
other western boundary layer
currents
• 1. the Gulf Stream
• 2. the coriolis force ant the gyre
• 3.the western boundary current layer
The Gulf Stream
• powerful, warm, and
•
swift Atlantic ocean
current
originates in the Gulf
of Mexico, follows the
eastern coastlines of
the United States,
and exits through the
Strait of Florida.
The Gulf Stream
• Modifying influence of the climate of
•
•
the east cost of north America.
extension toward Europe,(North
Atlantic drift): Western Europe
warmer.
For example, in January, the
temperature difference between
coastal Norway and northern parts
of continental Canada is
approximately 30 °C on average,
even if they are the same latitude.
The Gulf Stream
• Finally, the Gulf Stream is one of the strongest
•
•
•
ocean currents known:
transporting 1.4 petawatts of power.
moves at a rate of 30 million cubic meters per
second.
The volume of the Gulf Stream dwarfs all rivers
that empty into the Atlantic combined, which
barely total 1 million cubic meters per second.
The Coriolis force and the Gyre
Historically
• Some early writers thought the mighty Mississippi
•
•
River empties in the Gulf of Mexico, and from
there become the Gulf Stream
Later, Benjamin Franklin understood that winds
were the supreme current-producing power in the
sea.
In the middle of the 19th century, Commander
M.F Maury understood, that the currents do
not invariably follow the winds, but run at
right angles, or even against the wind
The Coriolis Force
• Every moving object
•
•
responds to the "Coriolis
force."
In the northern
hemisphere the Coriolis
force always deflects
objects to the right.
In the southern
hemisphere the Coriolis
force deflect objects to
the left.
The Gyre
• Trade winds set up a large-scale
gyre motion of surface waters in
each ocean basin, centered roughly
on the tropics of Cancer and of
Capricorn.
• Because of the Coriolis force,
surface water is deflected toward
the interior of the gyres
• if the wind should cease, the water
will attempt to run downhill from
the center of the gyre, and be
deflected by the Coriolis force
• The gyre keeps turning, while
balancing the forces of gravity with
those of the Coriolis force
Western boundary current layer
• The Gulf Stream is just a portion of the circle of the North Atlantic Current
• Why is it so strong compared to its symmetric towards Europe costs?.
The asymmetry
• Coriolis: f=2*W*sin(theta)
• Define Beta:
• 3 attemps to explain: limit condition in PDEs
Sverdrup
Stommel
Munk
Sverdrup’s theory of the Oceanic
Circulation
Stommel theory of Western
boundary currents
• He adds a botom stress proportional to velocity
• Coriolis depending or not on latitude explains Gulf
Stream
Munk’s solution
• He adds lateral friction
Thanks, may I help you?