Tuesday, October 5, 2010

More river water flows into oceans

Liz Kalaugher in Environmental Research Web: Climate change appears to be causing the water cycle to accelerate, boosting the amount of water flowing from rivers into the oceans. That's according to researchers in the US and India who have used satellite data to produce the first observation-based time-series of monthly global river discharge.

"Global river discharge is a fundamental Earth system flux that is important for fresh water availability, sediment and nutrient transport to the oceans, and for sea-level variations and sea-level rise," Jay Famiglietti of the University of California, Irvine, US, told environmentalresearchweb. "Surprisingly, there is no global, operational river-discharge monitoring network in existence – and in fact the number of stream gauges in the world is in steady decline."

Together with colleagues from the University of California, Irvine, Indian School of Mines, University of South Florida, California Institute of Technology and Remote Sensing Systems, US, Famiglietti found that river discharge increased from 1994 to 1999 and decreased slightly from 1999 to 2006. The team ascribed the increase to warmer sea temperatures due to El NiƱo.

On average, from 1994 to 2006 river discharge increased each year by 540 cubic km per year, or roughly 1.5%; the average global freshwater discharge was 36,055 cubic km per year. "While that [1.5%] may not sound like much, it summed to an 18% change over the 13-year period," said Famiglietti. "The 13-year period is too short to say that these trends are representative of the longer term. However, right now we can say that our study is an early warning that the water cycle may already be accelerating If these trends persist, say through the next decade, then they will be a smoking gun that water cycle acceleration is here."…

China’s Huang He (Yellow River) is the most sediment-filled river on Earth. Image from NASA

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