“For the past 18 years, the U.S./French Jason-1, Jason-2 and Topex/Poseidon spacecraft have been monitoring the gradual rise of the world’s ocean in response to global warming,” NASA’s Jet Propulsion Laboratory said in a 2011 release.
“While the rise of the global ocean has been remarkably steady for most of this time, every once in a while, sea level rise hits a speed bump,” it continued. In 2011, “ it’s been more like a pothole” as global sea level fell by about a quarter of an inch, or half a centimeter between the summers of 2010 and 2011.”
“So what’s up with the down seas, and what does it mean?”
In the accompanying video by Peter Sinclair, independent videographer, NASA/JPL climate scientist Josh Willis points to the cycle of El Niño and La Niña in the Pacific.
Willis said that while 2010 had begun with a sizable El Niño, by year’s end it was replaced by one of the strongest La Niñas in recent memory. According to JPL, in Pasadena, Ca., that sudden shift in the Pacific changed rainfall patterns across the globe, bringing “massive floods to places like Australia and the Amazon basin, and drought to the southern United States.”
JPL pointed to data from the “Grace” spacecraft indicating that extra rain piled onto the continents in the early parts of 2011.
“By detecting where water is on the continents, Grace shows us how water moves around the planet,” Steve Nerem, a sea level scientist at the University of Colorado in Boulder, said in the JPL press statement.
The extra water flooding Brazil and Australia actually came from the ocean, JPL said.
“Each year, huge amounts of water are evaporated from the ocean. While most of it falls right back into the ocean as rain, some of it falls over land.
“The continents got an extra dose of rain, so much so that global sea levels actually fell over most of the last year,” Carmen Boening, a JPL oceanographer and climate scientist, said.
Willis put the kibosh on those thinking a long-term decline in global sea level is in the works. Sea level drops such as this one cannot last, and over the long-run, the trend remains solidly up, he said.
JPL’s quick take: “Water flows downhill, and the extra rain will eventually find its way back to the sea. When it does, global sea level will rise again.”
“We’re heating up the planet, and in the end that means more sea level rise,” Willis added. “But El Niño and La Niña always take us on a rainfall rollercoaster, and in years like this they give us sea-level whiplash.”