For the study, the researchers analysed past sea level data collected from both satellite altimeters (NASA’s Topex-Poseidon and Jason satellite series missions) and traditional tide gauges.
The team also performed sea level reconstructions, dating back to 1950, by fitting patterns of satellite altimeter data to tide gauge data. They then removed the effects of the PDO to understand its influence on current sea level increases in the Pacific.
“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 of Old Dominion University in Norfolk, Va., a former CU-Boulder postdoctoral researcher and lead study author, in a statement. “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.”
The researchers also used NASA climate models to measure sea level rise in the tropical Pacific. Hamlington said that sea level rise near the Philippines and Australia partly occurred as a result of anthropogenic or human-caused warming.
Currently, the areas of the ocean near the Philippines and northeast Australia are being raised by about 1 centimeter per year due to anthropogenic warming, increasing the intensity of severe weather.
“When water starts piling up there and typhoon-like storms are traveling over higher sea levels, it can be a bad situation,” said Hamlington.
The average current global sea level rise is roughly 3 millimeters per year. Some scientists are estimating that global seas may rise by a meter or more by the end of the century as a result of greenhouse warming.
“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,” said CU-Boulder Research Professor Robert Leben, a study co-author. “I think the PDO has been suppressing sea level there for the past 20 or 30 years.”
The finding is published in the journal Nature Climate Change.