Satellite measurements of sea levels suggest the moon's tidal pull plays a once-unrecognized role in lifting cold water from the ocean depths and influencing Earth's climate.

Data from the U.S.-French TOPEX/POSEIDON satellite, which bounces radar off the oceans to measure sea levels precisely, also may solve the mystery of what happens to all the energy that the moon transfers to Earth by creating ocean tides.

Scientists once thought most of the energy was dissipated by friction as waves and tidal currents drag along shallow coastal sea floors. The new study indicates about three-fourths of the energy indeed is dispersed in that manner.

But the measurements also imply 25 percent to 30 percent of the energy in tides dissipates when deep-ocean tidal currents hit seamounts and mid-ocean ridges, creating turbulent "internal waves" that stir and lift cold bottom water so it mixes with warmer, shallower water. That effectively moves heat away from the sea surface, influencing climate in the overlying atmosphere.

Climate is strongly influenced by an oceanic "conveyor belt" in which cold, heavier water sinks near the poles, spreads toward the equator, then rises upward and mixes with warmer shallower water.

Winds were believed to provide 1 trillion watts half the power needed to drive such ocean circulation. Ray and geophysicist Gary Egbert of Oregon State University estimated the cold water is lifted by roughly another 1 trillion watts of tidal energy that dissipates in deep-ocean areas with rugged topography.

That rate of energy is enough to power 10 billion 100-watt light bulbs or to keep 77 billion people (13 times Earth's population) treading water so they won't drown, according to figures in The Sizesaurus, Stephen Strauss' book about measurement.

Egbert and Ray published their research June 15 in the journal Nature. They used six year's worth of data from TOPEX/POSEIDON. Plugging the information into computer simulations, they mapped the flow of tidal currents and energy, and where that energy dissipated.

The found about three-fourths of the tidal energy dissipated in shallow seas such as the European Shelf off Great Britain, the Yellow Sea near China, Canada's Hudson Bay, the Patagonian Shelf off Argentina's coast and the Australian Shelf.

But the other quarter of the tidal energy was dispersed in deep seas with rugged ocean-bottom terrain. Deep-water dissipation of tidal energy was notable along the Mid-Atlantic Ridge, Hawaii and related seamounts; island chains and seafloor trenches extending from Japan south to New Zealand; Tahiti and in the western Indian Ocean near Madagascar.

In 1998, MIT's Carl Wunsch and colleagues proposed tidal energy from the moon was lifting cold water from the ocean depths. Wunsch said the new findings do not prove the theory definitively. But he said they are consistent with the amount of energy needed to make cold ocean water well upward, and with the amount of energy imparted to the oceans by the moon.

Over geological time, sea levels rose and fell and Earth's continents and ocean basins changed in shape and size. That would have changed how much tidal energy dissipated in shallow and deep seas, and thus how heat was transported in the oceans. That, in turn, would have affected climate change over the eons.

"It appears that the tides, surprisingly, are an intricate part of the story of climate change," Wunsch wrote in a commentary accompanying the study.