The North Pacific Acted as Earth Ocean Backup Generator

The North Pacific Ocean might very well have acted as a sort of backup generator for Earth’s climate towards the end of the last major ice age.

A new study to be published in the July 9 issue of the journal Science authored by an international team of scientists from Japan, Hawaii and Belgium looks at the possibility that a major reorganization took place in the current system of the North Pacific Ocean which resulted in far reaching implications for the planet’s climate.

“The reconstructed changes in the North Pacific current system may have buffered the global impacts of the collapsed circulation in the Atlantic and possibly prevented further cooling of the Northern Hemisphere,” says Axel Timmermann at the International Pacific Research Center, University of Hawaii at Manoa, and corresponding author of the paper.

Earth’s climate is regulated heavily by the ocean’s density driven circulation, which brings warm surface water to the polar regions and cold water away to southern regions at depth. This regulation is often referred to as the ocean conveyor belt.

It is now a well established fact, however, that there have been times in the past when the North Atlantic part of the conveyor belt circulation has been disrupted by a massive influx of fresh water from melting ice sheets. The last time this happened was towards the end of the last ice age, approximately 17,500 to 15,000 years ago.

According to the study the North Pacific branch of the conveyor belt suffered a massive change which could have helped minimize the impact of the North Atlantic collapse.

“Around 17,000 years ago, the North Pacific surface waters grew saltier, and the resulting higher density there caused massive sinking. Newly formed icy deep water spilled out of the subarctic North Pacific at depths of 2000-3000 meters merging into a southward flowing deep western boundary current. A warm, strong poleward current, moreover, formed at the surface. It released much heat into the atmosphere and supplied water for the Pacific deep overturning circulation,” explains Yusuke Okazaki of the Japan Agency for Marine-Earth Science and Technology and lead author on the paper.

The authors believe that this deep overturning circulation in the Pacific may have additionally stirred up old carbon-rich waters from much farther down then is normally introduced to the conveyor belt, possibly contributing to an increase in atmospheric CO2. “This could have catalyzed further warming and accelerated the glacial meltdown,” says Laurie Menviel, also at the International Pacific Research Center and a co-author on this study.

The team acquired their evidence from radiocarbon data taken from 30 sediment cores from various locations in the North Pacific. They also ran a computer model that simulated the interactions among the ocean basins, sea ice, the atmosphere, land vegetation, and the global marine-carbon cycle. This “earth system model” was run using conditions based on the time period 17,500 to 15,000 years ago. The computer model corroborated the data they had gathered from the sediment cores.

Source: University at Hawaii at Manoa

Image Source: IPRC/SOEST

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