糖心视频

During very strong El Ni帽o events, sea level drops abruptly in the tropical western Pacific and tides remain below normal for up to a year in the South Pacific, especially around Samoa. The Samoans call the wet stench of coral die-offs arising from the low sea levels "taimasa" (pronounced [kai' ma'sa]). Studying the climate effects of this particular variation of El Ni帽o and how it may change in the future is a team of scientists at the International Pacific Research Center, University of Hawai'i at M膩noa and at the University of New South Wales, Australia.

Two El Ni帽o Taimasa events have occurred in recent history: 1982/83 and 1997/98. El Ni帽o Taimasa differs from other strong El Ni帽o events, such as those in 1986/87 and 2009/10, according to Matthew Widlansky, postdoctoral fellow at the International Pacific Research Center, who spearheaded the study.

"We noticed from tide gauge measurements that toward the end of these very strong El Ni帽o events, when sea levels around Guam quickly returned to normal, that tide gauges near Samoa actually continued to drop," recalls Widlansky.

During such strong El Ni帽o, moreover, the summer rain band over Samoa, called the South Pacific Convergence Zone, collapses toward the equator. These shifts in rainfall cause droughts south of Samoa and sometimes trigger more tropical cyclones to the east near Tahiti.

Using statistical procedures to tease apart the causes of the sea-level seesaw between the North and South Pacific, the scientists found that it is associated with the well-known southward shift of weak trade winds during the termination of El Ni帽o, which in turn is associated with the development of the summer rain band.

Looking into the future with the help of computer climate models, the scientists are now studying how El Ni帽o Taimasa will change with further warming of the planet. Their analyses show, moreover, that sea-level drops could be predictable seasons ahead, which may help island communities prepare for the next El Ni帽o Taimasa.