The Power of an Interdisciplinary Approach

The voluminous amount of TOGA data, together with satellite measurements of sea levels and sea surface temperatures, would have been of no avail without concurrent advances in the use of computers to model El Niño's behavior. All of these efforts, coming from ocean scientists on the one hand and atmospheric scientists on the other, paved the way for the truly powerful "coupled" models that bring together all available information to track how atmosphere and ocean changes interact. With such models it becomes possible to anticipate longer-term climate fluctuations. In the mid-1980s a statistical coupled model--based on a statistical relationship over time among selected variables such as sea level pressure over Indonesia and sea surface temperatures in the eastern equatorial Pacific--predicted the El Niño that began in late 1986. At about the same time, other researchers used a relatively simple dynamic coupled model to predict the same event. (Dynamic models differ from statistical models by solving mathematical equations on a grid that incorporates data from specified latitudes, longitudes, and depths.) Right on schedule, El Niño made an appearance in late 1986 and lasted through the first half of 1988.

A significant insight into why coupled models work--and a much-needed breakthrough in the long-standing conundrum of which partner leads in the dance of ocean and atmosphere--came in 1988. As researchers were aware, the ocean and atmosphere are inextricably linked, but they are not a perfectly balanced pair. The atmosphere is quick and agile, responding within a matter of days or weeks to altered sea surface temperatures. The vast and cumbersome ocean, by contrast, takes months to reach a new equilibrium with changes in the winds. Thus, the state of the ocean at any given time reflects a kind of memory of earlier winds--in the form of waves below the ocean surface--rather than the action of the winds in play at the moment. This lag in the ocean's response, scientists suggested, imparts certain chaotic properties that affect the timing of shifts in the cycle.

Sea Surface Temperature Anamolies show global El Niño and La Niña conditions. Temperature gradient: red, orange, and yellow (warm); aqua, green and blue (cool). (NOAA/National Environmental Satellite, Data, and Information Service)

By the late 1990s, several groups around the world had devised more complex coupled general circulation models (CGCMs) to make use of the observational data from the TAO array. In early 1997 some of these models revealed telltale signs of Pacific warming on the horizon. In the spring of 1997, NOAA advisories warned the world to expect a major event. By November, at El Niño's warming peak, sea surface temperatures were up some 5 degrees Celsius over 4,500 miles of open ocean, the most dramatic ocean warming ever recorded.

The 1997 to 1998 El Niño produced societal impacts as devastating as in 1982 to 1983. Storms lashed California for months on end and damaged or destroyed more than 1,400 homes, sweeping many down soggy hillsides. Some 90 people were killed in the United States alone, including 39 in central Florida, which was ravaged by a series of seemingly random twisters, which some people blamed on El Niño's impact on the jet stream. Indonesia suffered forest and peat fires that blackened skies across southeast Asia. Off the coast of Peru, fish stocks plummeted, devastating local populations of seals, sea lions, Humboldt penguins, and seabirds such as gulls and terns. In Mexico rogue fires scorched a treasured cloud forest. In Panama drought and low water levels in lakes that feed the Panama Canal forced officials to restrict shipping through the canal for the first time in 15 years.

Disastrous as this El Niño was, it could have been much worse. The early warning allowed farmers in drought-prone northeastern Brazil to plant heat-resistant crops. Los Angeles County, California, residents banded together to clear flood channels, bolster levees, and distribute sandbags to areas subject to flooding. The number of flood insurance policies taken out by Californians surged from fewer than 265,000 to more than 333,000. Residents of the Galápagos Islands repaved roads, installed new drainage systems, and shored up basic services such as water and communications.

Thanks to the joint efforts of oceanographers and atmospheric scientists, we now have tools that may eventually make climate fluctuations as common to predict as tomorrow's weather for some locations around the globe. From an initial inquiry into the failure of the monsoon in India and basic research into the physical processes of the ocean and atmosphere has come the invaluable ability to guide human activity in preparation for significant shifts in the planet's climatological makeup.

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