A recent international study warns of harsher weather ahead as the waters off the eastern Philippines and northeastern Australia have been found to be rising at one centimeter per year—one of the highest rates recorded in the world.
And there's no denying it this time: it's directly attributed to anthropogenic climate change. Researchers have estimated and removed the effect of the Pacific Decadal Oscillation (PDO) on sea level trends, eliminating the possibility that the rise is from natural causes alone.
Eliminating the PDO as a suspect
However, unlike the ENSO, the PDO fluctuates on a much longer time scale. The PDO fluctuates every 20-30 years, compared to the 6-18 months of ENSO. Because of this variability, there has been uncertainty as to what extent the PDO influences sea level rise in the Pacific.
The present study, published in the journal Nature Climate Change
, used sea level reconstruction to observe sea level trends from 1950-2010. Sea level reconstruction involves combining the data from tide gauges and satellite altimetry data from the National Aeronautics and Space Administration's (NASA) Topex-Poseidon and Jason satellite missions.
The effect of the PDO from 1993-2010 was estimated through empirical orthogonal function (EOF) analysis and then removed from the Archiving, Validation, and Interpretation of Satellite Oceanographic (AVISO) merged multi-altimeter sea surface height data.
PHL to experience stronger typhoons
By itself, the AVISO data already shows that sea levels off the eastern side of the Philippines are rising four times faster than the global average. When the PDO is removed as a factor, sea levels are still found to be rising at a rate of approximately one centimeter per year. This means that the eastern Philippines will bear the brunt of climate change impacts, including stronger typhoons.
"The conventional wisdom has been that if the Pacific Decadal Oscillation was removed from the equation, this sea level rise in parts of the Pacific would disappear," said Benjamin Hamlington, lead author of the study. "But we found that sea level rise off the coasts of the Philippines and northeastern Australia appear to be anthropogenic and would continue even without this oscillation."
Previous studies have shown that the warming tropical Indian Ocean works together with the warm western tropical Pacific and the cool central-eastern tropical Pacific to strengthen the easterly trade winds. The trade winds then push the surface waters westwards and increase sea levels in the western tropical Pacific.
"When water starts piling up there and typhoon-like storms are traveling over higher sea levels, it can be a bad situation," said Hamlington.
Americas also affected
"When the current PDO switches from its warm phase to its cool phase, sea levels on the western coast of North America likely will rise," added co-author Robert Leben. "I think the PDO has been suppressing sea level there for the past 20 or 30 years."
The study was done by researchers from Old Dominion University, the University of Colorado at Boulder, and Seoul National University. — TJD, GMA News
Macy Añonuevo earned her MS Marine Science degree from the University of the Philippines. She is a published science and travel writer and was a finalist in the 2013 World Responsible Tourism Awards under the Best Photography for Responsible Tourism category. Her writings and photographs may be found at www.theislandergirl.com.