Sea Level Rise in the Tropical Pacific Ocean isn't Natural: Human Activity to Blame

First Posted: Jul 22, 2014 07:57 AM EDT

Rising sea levels are a huge issue for coastal communities in the face of climate change. Now, a new study reveals that levels will likely continue to rise in the tropical Pacific Ocean off the coasts of the Philippines and northeastern Australia.

In order to get a better understanding when it comes to sea level rise, the researchers combined past sea level data gathered from both satellite altimeters and traditional tide gauges. More specifically, they wanted to see how a naturally occurring climate phenomenon, known as the Pacific Decadal Oscillation (PDO), might influence sea rise patterns in the Pacific.

So what is the PDO? It's a temperature pattern in the Pacific Ocean that's similar to El Nino. Yet instead of lasting just a few months or a year, the PDO lasts roughly 20 to 30 years and contributes significantly to decadal trends.

The researchers reconstructed sea level patterns going back to 1950. Then, they stripped away the effects of the PDO to better understand its influence on current trends.

"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, one of the researchers, in a news release. "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."

In fact, the researchers estimate that sea level rise near the Philippines and northeast Australia is about one centimeter per year due to anthropogenic warming. This rise can also increase the intensity of severe level, including typhoon-like storms. That's not all, either; it's possible that the PDO may have actually helped suppress sea levels.

"When the current PDO switches from its warm phase to its cool phase sea levels on the western coast of North America will likely rise," said Robert Leben, one of the researchers. "I think the PDO has been suppressing sea level there for the past 20 or 30 years."

The findings reveal that sea levels are likely to continue to rise and that anthropogenic warming may be causing more issues than thought. While the PDO does play a role, it seems that people are more to blame.

The findings are published in the journal Nature Climate Change.

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