Tropical waters in the Northern Hemisphere have been heating at an enhanced rate since 1984, scientists at the National Oceanic and Atmospheric Administration said Friday. Bleaching can indicate that coral is stressed by such factors as high water temperatures, pollution, sedimentation, high light levels, reduced water levels or changes in salinity. A team of scientists, led by Alan E. Strong of NOAA's National Environmental Satellite, Data, and Information Service, analyzed sea surface temperature data from NOAA's polar-orbiting satellites for the period 1984 through 1996. The data show that temperatures have been inching slowly upward around the globe, Strong said.
Oceans show cooling in the centers of the major basins and warming around the margins.
Analyses of the Atlantic, Pacific, and Indian oceans, when taken as a whole, indicate that from 1984 to 1996, warming has been taking place over the Northern Hemisphere tropics, close to what has been referred to as the thermal equator, Strong said. Most of the reefs within these latitudes have been bleached over the past 10 years, he said. Strong and his colleagues compared the satellite-only sea surface temperature data to readings taken from the water. All data consistently show a warming in the equatorial Pacific, cooling in the central North Pacific, and cooling in the Southern Hemisphere. If this trend were to continue, implications for our coral reefs throughout these waters would be bleak.