Oceans Warmer and Smaller in New Studies

Washington, May 22, 2010 — -- Two new studies out this week give the best scientific estimates of the average depth of the world's oceans, the total amount of water they contain, and the extent to which this water warmed over the last two decades – the latter being an important measure of climate change.

In the first study, reported in the journal Oceanography, a team from Woods Hole Oceanographic Institution in Massachusetts analyzed global satellite data and made the best-ever estimate of the amount of water in the world's oceans. They put the figure at more than 1.3 billion cubic kilometers. Though that's slightly less water than scientists had previously estimated, it's still enough to fill more than 1.5 million Olympic-size swimming pools for each person in the United States.

The second study, reported in this week's issue of the journal Nature, addresses how all this water can help scientists track global warming and predict its effects.

Led by John Lyman at the National Oceanic and Atmospheric Administration, this study involved a team of researchers from the United States, Germany, and Japan. They analyzed several different sets of ocean temperature measurements collected around the world from 1993 through 2008.

These measurements were made by different groups over this 16-year period using different assumptions. Some discrepancies between them arose because of the way the data was processed. Some swaths of ocean were not sampled as widely or as often as others. Changes in instrumentation have confused the issue further.

However, Lyman and colleagues standardized all the measurements and in doing so they found the same general trend for all the data.

"Although you see differences, they are all fairly consistent," said Lyman.

They also averaged the results from these groups, which gave them the best estimate to date of the extent to which the top layers of the ocean have warmed over the last two decades. Lyman said that information is important because it is a good measure of global warming.