Southern California environment news and trends

UC Irvine researchers see the sea, and more of it, in satellite images

A team of scientists - led by researchers at UC Irvine - has made new estimations of sea level rise from freshwater flowing into the world's oceans.

Jay Famiglietti, UC Irvine Earth system science professor and principal investigator on the study, says rivers and melting polar ice fed 18 percent more water into the world's oceans by 2006. That's an average annual rise of 1.5 percent.

"In general, more water is good," Famiglietti said in a UC Irvine-penned release. "But here's the problem: Not everybody is getting more rainfall, and those who are may not need it. What we're seeing is exactly what the Intergovernmental Panel on Climate Change predicted - that precipitation is increasing in the tropics and the Arctic Circle with heavier, more punishing storms. Meanwhile, hundreds of millions of people live in semiarid regions, and those are drying up."

That intensifying water cycle - more rain in the tropics, with other regions drying up - has been a source of study for researchers around the world. Earlier this year, Australian researchers released work where they analyzed salinity and other historic records to find that sea water in areas of heavy rain has freshened, while sea water in hotter and drier areas - where evaporation occurs - has gotten saltier.

In this study led by the UC Irvine team, scientists used satellite records of sea level rise, and precipitation and evaporation, to estimate freshwater flows. They worked over a relatively short period of time - 13 years of data is hardly a long-term trend. But they and others are working to extend their observation period. So they caution that their observation period "though long for an observation-based global discharge, is relatively short considering the high degree of interannual variability apparent." In other words, as they say - they'd like more data to get evidence of an amplifying water cycle. Right now, what they have suggests it.

Still, one reason the findings are significant is that so far, nobody's organized a global network to actually watch for changes in sea level. In the journal Proceesings of the National Academies of Science (PNAS), lead author Tajdarul Syed of the Indian School of Mines, formerly of UCI, writes that "strong socioeconomic disincentives for sharing data, a worldwide decline in the number of operational gauging stations, and incomplete measurement of total volume of freshwater discharged along continental margins, combine to severely limit the capacity of gauging networks to characterize the behavior of global freshwater discharge in near real-time."

With apologies to Pablo Neruda - who wrote, "When I see the sea once more/will the sea have seen or not seen me?" - the answer seems to be probably not, but if it has, it wasn't in the same form last time.

Other authors are Don Chambers of the University of South Florida, Joshua Willis of the Jet Propulsion Laboratory in Pasadena, and Kyle Hilburn of Remote Sensing Systems in Santa Rosa, Calif. NASA funded the study.

Read more about it on UC Irvine's website here.

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