[Himanshu Bali (OP)]

Can anyone tell me about Western Pacific Warm Pool, how did it formed, and its relation to the Indonesian Throughflow?

[CliffordK]

If you look at the sea level anomaly, there consistently is a high or fast rising area just north of Australia.

http://photojournal.jpl.nasa.gov/catalog/PIA11002


It seems to be in part related to ENSO (El Niño/La Niña) ocean currents, but there seems to be a persistent element of it.  As if the sea level is increasing in both El Niño years and La Niña years.

There are a few low lying islands such as the Carteret Islands which lie in this area of increased sea level rise that are having significant problems with flooding.
http://en.wikipedia.org/wiki/Carteret_Islands

Anyway, much of the sea levels are rising due to thermal expansion, and thus the sea levels and temperatures are closely intertwined.

Ahh, found a chart showing sea levels over time with the western pacific and Indonesia barely visible along the leftmost side.



So, the chart was started during a multi-year El Niño event, which would bias the starting temperatures/sea level in the area being cold.  The strong El Niño or 97/98 brought a moderate drop in sea levels in the region.

The weaker El Niño currents in the middle of the first decade of this century did not.

Anyway, so to a large extent, this Western Pacific Warm Anomaly seems to be tossed around by ENSO (El Niño/La Niña), and perhaps other deep ocean cycles. 

Another ocean current I didn't discuss is the Pacific Decadal Oscillation (PDO) which is a multi-year oscillation of East to West sea temperatures, largely in the Northern Pacific.  We are currently in a phase that brings cool water to the west coast of the USA (eastern pacific), and warm water to the western pacific region.  There may be other related multi-year current oscillations in that region too.

[Himanshu Bali (OP)]

Thank You CliffordK for this valuable information.

[JimBob]

If you look at the sea level anomaly, there consistently is a high or fast rising area just north of Australia.

It seems to be in part related to ENSO (El Niño/La Niña) ocean currents, but there seems to be a persistent element of it.  As if the sea level is increasing in both El Niño years and La Niña years.

<SNIP>

Anyway, much of the sea levels are rising due to thermal expansion, and thus the sea levels and temperatures are closely intertwined.

..... thus the sea levels and temperatures are closely intertwined.

INDEED THEY ARE - There is only one physical cause, however.

The real - and only legitimate - physics behind the Western Pacific Warm Pool is the Coriolis effect. The water, warmed by the heat of it's travel along the equator, is going to be warmer in the western Pacific than in the eastern Pacific on average. This varies due to climate but it's origin and persistence is due only to Newtonian Physics.

A bowl of water sitting on a table in the northern hemisphere will be higher on its western side, just as an ocean does.

[granpa]

the wind at the equator is blowing toward the west so the warm equatorial water is blow to the west.

[JimBob]

"Perhaps the most commonly encountered rotating reference frame is the Earth. Because the Earth completes only one rotation per day, the Coriolis force is quite small, and its effects generally become noticeable only for motions occurring over large distances and long periods of time, such as large-scale movement of air in the atmosphere or water in the ocean. Such motions are constrained by the 2-dimensional surface of the earth, so only the horizontal component of the Coriolis force is generally important. This force causes moving objects on the surface of the Earth to appear to veer to the right in the northern hemisphere, and to the left in the southern. Rather than flowing directly from areas of high pressure to low pressure, as they would on a non-rotating planet, winds and currents tend to flow to the right of this direction north of the equator, and to the left of this direction south of it. This effect is responsible for the rotation of large cyclones (see Coriolis effects in meteorology)."

http://en.wikipedia.org/wiki/Coriolis_effect

[frethack]

INDEED THEY ARE - There is only one physical cause, however.

Be careful with absolutes.

The WHWP is indeed located in the Western Pacific because the trade winds (caused by coriolis) blow warm surface water westward, creating a shoaling of the thermocline and upwelling of cool water in the east. 

There are other major factors that are in play however.  The position, average temperature, sea level height, and sea level pressure of the WHWP oscillates on seasonal and interannual time scales because of shifts in the Walker circulation, position of the ITCZ, intensity and latitude of the Hadley Cell, etc.

[JimBob]

Are not the winds of the earth steered in their direction of initial movement by by the Coriolis Effect?

[Geezer]

Are not the winds of the earth steered in their direction of initial movement by by the Coriolis Effect?

I think they are. The predominant flow of weather systems goes from West to East as a result of the Earth's rotation.

[frethack]

Are not the winds of the earth steered in their direction of initial movement by by the Coriolis Effect?

Absolutely they are, which pushes the WHWP into the western pacific, but its northern extent is is greatly influenced by other factors as well.