Study rethinks the ocean's role in Pacific climate

According to the study's lead author, UM Rosenstiel School Professor Amy Clement, the tropical atmospheric pressure system know as the Southern Oscillation (a periodic fluctuation of atmospheric pressure commonly observed as the El Niño Southern Oscillation, which brings unusually warm water across the Pacific Ocean basin) plays a bigger, more fundamental role in the climate system than just being El Niño's atmospheric counterpart.

Scientists have long believed that the Southern Oscillation exists due to its connection to the ocean. "This study changes the textbook version of one of the most fundamental aspects of atmospheric circulation," said Clement, whose study was published in the August 2011 issue of American Meteorological Society's Journal of Climate.

In two sets of experiments, Clement, recent UM alumnus Pedro DiNezio, and co-author Clara Deser from the National Center for Atmospheric Research modeled two climate scenarios – one with a static, current-free ocean and another with a fully dynamic ocean. The team showed that atmospheric pressure, surface temperature, and precipitation were the same in both ocean scenarios, which reveals that the Southern Oscillations global signature is still present even when the ocean and atmosphere are disconnected.

In a news item in the Sept. 29 issue of the journal Nature, Research Institute for Global Change scientists Jing-Jia Luo said, "…Clement et al. argue impressively that it is not necessary to couple ocean dynamics to the atmosphere in models to reproduce tropi¬cal climate modes and their associated global connections."

British physicist Sir Gilbert Walker discovered the Southern Oscillation in the early 20th century when trying to understand and predict India's monsoons, which caused torrential rains and widespread famine in the region. He proved that this large-scale sea-level pressure in the tropics connected India's weather with other weather patterns across the world.

"This new development can help link climate patterns between distant region, such as rainfall patterns in Australia and drought in the Southwestern U.S.," said Clement.

Journal reference: Journal of Climate

Provided by University of Miami Rosenstiel School of Marine & Atmospheric Science