VULNERABILITY OF FRESH-WATER RESOURCES TO CLIMATE-CHANGE IN THE TROPICAL PACIFIC REGION

El Nino events and associated droughts adversely affect freshwater res ources on islands in the tropical Pacific region. Particularly vulnera ble are low-lying atolls because rainwater collection is the main fres hwater source on such islands. During El Nino-ralated droughts, water can be drawn only from the limited freshwater lenses beneath the islan ds. If drought conditions such as these intensify, the depletion of fr eshwater resources could affect the habitability of atolls. Avenge cli mate change in the Pacific region from increased anthropogenic carbon dioxide in a global coupled climate model resembles present-day El Nin o conditions as well as the decadal time scale sea surface temperature and precipitation anomalies observed during the 1980s and early 1990s . These anomalies are a consequence of greater warming of sea surface temperatures in the eastern equatorial Pacific than over the western P acific warm pool with increased carbon dioxide in the climate model. A ttendant increases in precipitation in the central equatorial Pacific are also accompanied by precipitation decreases in the northern and so uthern tropical Pacific (roughly 5 degrees N to 15 degrees N and 5 deg rees S to 15 degrees S), as well as in the Australasian and eastern In dian Ocean regions. Associated effects in the midlatitude North Pacifi c also resemble El Nino conditions and the decadal time-scale signals from the 1980s. Future possible increases of drought conditions in cer tain tropical Pacific regions, as indicated by the climate model resul ts, could limit the sustainability of atoll populations in those regio ns, causing migration and increased urbanization, with all the attenda nt problems, on larger high islands with more stable water supplies.