Windows on A Vast Frontier

By Eugene Linden/Miami

Laury Miller recalls with awe the moment he first saw the infrared image of the two cyclones. The picture, taken by a Japanese weather satellite, revealed two giant Pacific storms in temporary but exact alignment on opposite sides of the equator. That conjunction generated a massive burst of westerly winds across thousands of miles of the equatorial ocean, pushing a surge of warm water eastward. Miller, a Government oceanographer, abruptly realized he was looking at a mysterious natural engine that drives El Nino, the unruly fluctuation of weather that periodically afflicts places as widespread as South America, Asia, Alaska and Africa.

The satellite data, published in a scientific journal earlier this year, are only the latest evidence of how remote sensing -- the examination of distant or concealed objects by sound waves, electronic signals or other means -- has dramatically changed the study of the oceans. Scientists are now able to see things that they could only grope at before. This is made possible not only by a satellite's panoramic perspective but also by new sonar techniques that peer through waters that are miles deep. Oceanographers who once devoted years to analyzing information from infrequent research trips are deluged with data that are yielding the secrets of earth's last frontier.

Most recent breakthroughs in remote sensing came from satellites launched in the late 1970s. NASA's Seasat 1, Tiros N and Nimbus 7 satellites took indirect measurements of ocean conditions, such as surface wind speed and direction, by gathering data on radiation scattered by waves. At first, scientists had to correct their data for errors introduced by everything from sunspot activity to changes in the ozone levels of the upper atmosphere. "It wasn't just getting bigger computers, better instruments, better physics or better computer languages," says Robert Evans, a physicist at the University of Miami's Remote Sensing Laboratory. "We needed all of those."

Evans and his colleagues have been studying water color and temperature since 1980. Their aim is to develop the first global picture of oceanic photosynthesis, the process by which algae and microscopic plant life use light to convert water and carbon dioxide into nutrients. Ultimately, they would like to learn how the oceans will influence the global warming trend, known as the greenhouse effect, and how they will be influenced by it.

Today satellite pictures of chlorophyll a, the best indicator of photosynthesis, are as reliable as readings taken directly from the water. Evans and NASA will soon begin releasing the global images to eager colleagues. "If we are to ask society to make trillion-dollar decisions, such as switching from coal to natural gas in order to reverse the greenhouse effect, we have to validate the models on which those decisions are based," says Stephen Schneider of the National Center for Atmospheric Research in Boulder. "The primary productivity of the oceans is an essential component of any such model."

Remote-sensing instruments on ships and satellites have been used for years by underwater archaeologists, geologists and naval technicians to locate submerged objects. Similarly, scientists have used infrared satellite data, combined with on-site exploration, to examine the dynamics of huge underwater storms spun off by the Gulf Stream. These systems, called warm-or cold-core rings, remain intact for months. As much as 60 miles in diameter and 3,000 ft. deep, the slowly circulating columns store energy equivalent to the capacity of a major nuclear power plant and play an important role in ocean life.

In 1985 Donald Olson of Miami's sensing lab, with Richard Backus, a marine biologist at the Woods Hole Oceanographic Institution in Massachusetts, set about examining how one warm-core ring off the Atlantic Coast of the U.S. affected fish. They discovered that the population of small lantern fish on the outer boundary increased 100 times during a 50-day period as the circulation drove the fish to the edge of the ring. This has led other scientists to speculate that warm-core rings could be used as huge aquaculture systems, in which food fish are seeded early in the ring's life and harvested later.

When researchers want to peer beneath the surface of the oceans, they run into what one scientist called a "conspiracy of physics." Water tends to scatter light and sound waves, limiting scientists to either a fuzzy or restricted view of the ocean's depths. At Woods Hole, Physicist Ken Stewart overcame the problem this year with a computer program that integrates several sonar readings into a sharp composite image. For instance, readings from a towed sonar system that provides high-resolution detail about ocean-floor contours can be merged with data from a shipboard sonar system that views the same territory from above. The result is a vivid, three-dimensional view of the ocean bottom. "It's a real watershed," says Daniel Fornari of Columbia University's Lamont-Doherty Geological Observatory, near New York City. "Instead of analyzing data and getting a picture months after a cruise, if we see something interesting, we can go down and dredge on the spot."

Perhaps the biggest dividend of remote-sensing technology, though, is that it has changed the way ocean scientists pursue their work. Otis Brown, head of Miami's sensing lab, likens earlier oceanographers to "natural philosophers in the early 19th century, who had to build theories based on jottings in notebooks." Now scientists like Laury Miller have pictures that give shape to their abstractions. Says Mathematician Mark Cane of Lamont-Doherty: "The great scientists have a vision into which they fit the parts, while the rest feel their way along. Now all ocean scientists have the vision as well."