Sea level rise 'unavoidable,' NASA says; West Coast waters likely to start rising rapidly
Global sea levels have risen an average of 3 inches over nearly a quarter century, but not along the West Coast. NASA scientists say long-term climatic patterns have lowered sea levels along California, Oregon and Washington in recent decades, but they also warn that the region is likely to see a dramatic reversal in that trend in the next twenty years.
"Long-term natural cycles there are hiding the impact of global warming," says Josh Willis, an oceanographer at NASA's Jet Propulsion Laboratory in Pasadena. "This is a temporary thing."
Willis attributed the trend in the eastern Pacific Ocean to lower-than-normal sea surface temperatures associated with the Pacific Decadal Oscillation. The PDO is a climate pattern being tracked by NASA and the National Oceanographic and Atmospheric Administration’s Climate Prediction Center. When patches of the ocean cool, they contract; the smaller mass means lower seas.
Now NOAA says we’re entering a warming phase for the PDO. And NASA researchers say it's likely that warming seas near the West Coast will expand and rise.
"In the long run we expect sea levels to catch up to the global mean and even exceed it," Willis says. "People need to be prepared for sea level rise. It's not a question of how much, but when."
Scientists attribute about a third of global sea level rise to oceans expanding as they warm. Another third of the rise comes from melting glaciers on mountains, and the final third is blamed on the loss of ice on the massive Greenland and Antarctic ice sheets.
NASA's researchers emphasized that sea level is rising, rapidly and unavoidably, for all three reasons. "It's already happening right now," says UC Irvine and JPL glaciologist Eric Rignot. "This isn't some futuristic scenario."
The findings are based on data from three satellite missions conducted since 1992.
The video below shows as a visualization of that data.
In recent years, NASA has launched specific programs aimed at understanding how ocean temperatures and currents speed melting of the Greenland and Antarctic ice sheets from underneath.
The Oceans Melting Greenland, or OMG project, is producing the first high-resolution maps of the continental shelf surrounding Greenland, including the seafloor and canyons below the surface.
"And before you ask, yes, I did pick that name while I was deleting old texts from my cell phone," Willis says.
While Greenland currently contributes more heavily to sea level rise than Antarctica, Rignot emphasized that NASA and other scientists were watching ice sheets on Antarctica, particularly east Antarctica, closely.