Hidden depths of global heat

TOM WILKIE

Science Editor

Many dark secrets lie within the Bermuda Triangle, according to modern myth, but its demonology has now taken an ultra-modern twist: could it be a cause of global warming?

Lurking in the upper few hundred metres of sediments at the bottom of those mysterious seas, scientists believe, lie strange ice-like substances known as "gas hydrates" - ice made up of methane and water. Later this year, they plan to despatch the international ocean drilling ship, Resolution, to probe the depths of the sediments for these hydrates.

The connection with the greenhouse effect is that methane is a powerful greenhouse gas, 20 times more effective than carbon dioxide, and that hydrates represent the largest reservoir of methane on earth. Their effect can be enormous: the release of one- thousandth of the global hydrate reservoir would be equivalent to the whole of humanity's output of carbon over the past century. The Bermuda Triangle is an area of the Atlantic Ocean where ships and aircraft are supposed to have vanished.

The voyage of the Resolution, partly sponsored by Britain's Natural Environment Research Council, is to measure more precisely the amount of gas trapped in hydrates, how they got there, and their effects on the sediments. But the gas hydrates have become the latest villains of the triangle: for they are capable of releasing huge volumes of methane, bursting as bubbles to the surface. The gas is asphyxiating and could cause crews to lose control of aircraft, and the outbursts could create enough turbulence to send a vessel to the bottom.

There are, however, two snags. The first is that no more aircraft and ships have "disappeared" in the area of the Bermuda Triangle than might be expected for a region with that pattern of weather and ocean currents. Secondly, gas hydrates have been found in marine sediments in all the world's oceans.