THE ROLE OF TROPICAL OCEANS IN CLIMATE FORCING: EVIDENCE FROM THE INDO-PACIFIC WARM POOL DURING THE QUATERNARY

Tropical oceanic water that surrounds Southeast Asia and northern Australia today is characterised by constantly high (>28°C) sea-surface temperatures, a low-salinity and shallow 'cap' called the barrier layer that prevents much exchange with the deeper water and the atmosphere. This region, abbreviated to the Warm Pool, sees the formation of high convective clouds that are critical to climate forcings on either sides of the Pacific and Indian Oceans. Today, the Warm Pool is the location of vast amounts of moisture and heat exchange between the atmosphere and the oceans, with ensuing contrasting monsoonal climates that affect the bordering land masses and its people and biota.

I will argue that any slight change in sea-surface temperature in the Warm Pool, and/or a change in the ocean to land ratio - the latter resulting from cyclic sea level changes so typical of the Quaternary - can substantial consequences for climate, very likely on a global scale.

A reduction in deep convective clouds over the Indo-Pacific Warm Pool would engender the following: (1) increase the radiative loss to the upper atmosphere, thus causing its cooling, but also force sea-surface surface heating associated with strong diurnal temperature contrasts on land; (2) change the precipitation/evaporation ratio over the Warm Pool region and associated landmasses, and also change the moisture of the upper atmosphere; (3) destabilise the upper layers of the oceans, and alter the freshwater flux to the global ocean (and consequently affect its upper layer density); (4) alter wind regimes, their strengths and patterns in the region. This would eventually cause significant changes in the upper layers of the Indian and Pacific Oceans at least; (5) alter the poleward transport of heat and moisture, thus affecting the characteristics and formation of oceanic deep water, and lapse rates in the tropics; and (6) the albedo ratio between land and ocean.