El Nino events in the Pacific will be more severe due to climate change

El Nino events in the Pacific will be more severe due to climate change

By the end of this century, El Nino and La Nina events will double in frequency and produce greater and greater levels of destruction, mostly in the southwestern Pacific.

The sea level of the Pacific Ocean is rising. An international collaboration of scientists have just released a study in Science Advances that may explain why.

Researchers at the University of Hawai’i at Manoa’s International Pacific Research Center worked with scientists at the Commonwealth Scientific and Industrial Research Organization in Australia to try and determine the cause behind the extreme variation in sea levels.

Using computer models and analysis of tides, the team was able to project the Pacific wind response to the behavioral change of El Nino. With state-of-the-art technology, scientists created the possible future effects of El Nino. The climate model they fashioned included calculations on the rising greenhouse gas concentrations.

“From our previous work, we know that toward the end of a very strong El Niño event, the tide-gauge measurements around Guam quickly return to normal reflecting the east-west seesaw, but those near Samoa continue to drop as a result of the lagging north-south seesaw,” said Matthew Widlansky, a researcher at the University of Hawai’i at Mānoa. “During these strong events, the summer rainband over Samoa, called the South Pacific Convergence Zone, shifts toward the equator and alters the trade winds and ocean currents which in turn change the sea level.”

The team concluded that climate change has boosted El Nino’s strength by increasing sea level extremes. By the end of this century, El Nino and La Nina events will double in frequency and produce greater and greater levels of destruction, mostly in the southwestern Pacific.

“Our results are consistent with previous findings that showed the atmospheric effects of both El Niño and La Niña are likely to become stronger and more common in a future warmer climate,” said Wenju Cai, a researcher at CSIRO.

Usually, trade wind blow from east to west across the Pacific ocean, moving warm water towards Asia and Australia while causing cold water to rise along the American coast.

El Nino is a weather phenomenon that naturally occurs every two to seven years. During a time when El Nino is in effect, trade winds grow weak and warm water stays in the east. This causes high water levels near American shores and low water levels along Asian shores.

Over the course of six months to a year, water levels in the Southern Hemisphere can drop by as much as one foot.

“We noted a trend in greater variability and were surprised at first to find not only more frequent and prolonged drops in sea level, but also more frequent high sea level events. This will further increase the risk of coastal inundations,” said study co-author Axel Timmerman.

This can wreck havoc on marine life in the South Pacific. Ecosystems become exposed to the air and huge chunks of coral reef have been known to die off. This is what causes the rotten smelling tide known as taimasa.

“The possibility of more frequent flooding in some areas and sea level drops in others would have severe consequences for the vulnerable coastlines of Pacific islands,” said Widlansky.

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