The Pacific Ocean

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The Pacific Ocean
Talley, 2001
2
Major Pacific Current Systems
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Equatorial Surface Currents

• Trade winds in both northern and southern
  hemispheres separated by a region of light winds,
  the Doldrums
• They are basically associated with the ITCZ
• The position of the continents shifts the
  doldrums into the northern hemisphere (instead of
  directly on the Equator)

Segar, 2007
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Sea level pressure and surface wind
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Equatorial Surface Currents

• The observed wind pattern sets up the Ekman
  transports in the Equatorial region
• Note the change in Ekman transport at the Equator
• This sets up patterns of raised and lowered sea
  surface height

Segar, 2007
6
Equatorial Surface Currents

• The normal sea surface slope up into the
  sub-tropical regions is present
• Additionally, there is a region of high sea
  surface near the the doldrums, produced by the
  northward Ekman transport in the region just
  north of the Equator
• These slopes set up the Equatorial current system

Segar, 2007
7
Equatorial Surface Currents

• Flow from 5N is directed south by the pressure
  gradient and then turned to the right by the
  Coriolis Effect, producing the westward South
  Equatorial Current (SEC)
• Similar process south of the Equator (with a
  deflection to the left) also help strengthen the
  SEC
• Farther north, the North Equatorial Current (NEC)
  and the Equatorial Counter Current (ECC) are
  generated

Segar, 2007
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Equatorial Surface Currents

• The strong currents to the west lead to water
  piling up along the western boundary
• To balance this, the Equatorial Undercurrent
  (EUC) is generated
• This is a strong and fast current that flows
  directly along the Equator

Segar, 2007
9
Equatorial Surface Currents

• EUC found at 50-300 m depth
• Flows purely east-west as no Coriolis deflection
  at the Equator
• Additionally, if it moves north or south of the
  Equator, the Coriolis deflections help direct it
  back to the Equator
• Flows thousands of kms from west-to-east across
  the tropical Pacific
• Note Similar behavior (somewhat) in other basins

Segar, 2007
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Pacific layering salinity
Pacific salinity section with inset map showing
150w
Lower salinity - Antarctic and N. Pacific
intermediate waters
Higher salinity - Atlantic/Ant- arctic waters
32S
24N
Talley, 2001
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Oxygen at 1000 meters
Yellow low oxygen concentration
High oxygen sources are in the Okhotsk Sea and in
the southeast Pacific (sources of North Pacific
and Antarctic Intermediate Waters)
Blue high oxygen concentration
Talley, 2001
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Abyssal circulation (4000 dbar)
Two anticyclonic gyres
Samoan Passage constriction of deep northward flow
Deep western boundary current
Talley, 2001
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Abyssal radiocarbon
Penetration of higher values in the west, lowest
values in the northeast