Tuesday, June 24, 2014

Strange days in the Indonesian straits

Among the very strange and spooky impacts of climate change: changes in the behavior of massive oceanic current patterns.

(Image: The Indonesian Straits, which provide a conduit between the Pacific and Indian Oceans. They are described as the only place on the planet where oceans interact the way they do here, and the only place in the tropics where oceans are able to interact. Source: University of Hawai`i.)

New research suggests that climate change will alter the flow between the Pacific and Indian Oceans through the Indonesian straits. That’s on top of changes in the flow that are driven  by the alternating El Nino-La Nina climate cycles.

What this will mean longer-term is not yet entirely clear, but there are suggestions that the changing flow could change the climate in both oceans. A better understanding of the changes could result in better forecasts of climate activity, according to a new paper.

The flow of ocean water through the Indonesian strait appears to have become both shallower and stronger, according to a study published June 22 in the journal Nature Geoscience. The paper is entitled “The Indonesian seas and their role in the coupled ocean-climate system.”

UH Mānoa physical oceanographer James Potemra is a co-author. The lead author is Janet Sprintall of Scripps Institution of Oceanography at UC San Diego, and other co-authors are Arnold Gordon of Lamont-Doherty Earth Observatory at Columbia Unversity, Ariane Koch-Larrouy of LEGOS in France, Tong Lee of the Jet Propulsion Laboratory in Pasadena, Calif., Kandaga Pujiana of Oregon State University and Insitut Teknologi Bandung in Indonesia, and Susan Wijffels of the Commonwealth Scientific and Research Organization in Australia.

Eric Lindstrom, co-chair of NASA’s  Global Ocean Observing System Steering Committee, which funded part of the study, talked about its importance:

“This is a seminal paper on a key oceanographic feature that may have great utility in climate research in this century. The connection of the Pacific and Indian oceans through the Indonesian Seas is modulated by a complex circulation, climate variations, and sensitive ocean-atmosphere feedbacks.  It’s a great place for us to sustain ocean observations to monitor potential changes in the ocean’s general circulation under a changing climate.”

Lead author Sprintall said: “Now that we have a better understanding of how the Indonesian Throughflow responds to El Niño and La Niña variability, we can begin to understand how this current behaves in response to changes in the trade wind system that are brought on through anthropogenic climate change.  Changes in the amount of warm water that is carried by the throughflow will have a subsequent impact on the sea surface temperature and so shift the patterns of rainfall in the whole Asian region.”

Here’s some complex language from the paper on what’s going on with the currents: “A synthesis of observational data and model simulations indicates that the temperature, salinity and velocity depth profiles of the Indonesian throughflow are determined by intense vertical mixing within the Indonesian seas. This mixing results in the net upwelling of thermocline water in the Indonesian seas, which in turn lowers sea surface temperatures in this region by about 0.5 °C, with implications for precipitation and air–sea heat flux.”

A University of Hawaii press release discusses the paper. 

More information on this kind of stuff at the website of the International PacificResearch Center at University of Hawai`i at Mānoa. 
© Jan TenBruggencate 2014

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