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The Oceanic Conveyor Belt: Climate Change Tipping Points Being Reached in the Arctic, Western Boundary Ocean Currents

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Accelerated changes in the Arctic are moving ocean currents poleward and threaten the oceanic conveyor belt

Two new research papers by authoritative climate research teams were announced this week — one on climate change tipping points being reached in the Arctic and a second on warming of long-distance, poleward-moving ocean currents. The results of the studies show that warming of both the Arctic and western boundary currents is happening faster than has been anticipated, prompting the researchers to publicly urge that efforts to adapt to abrupt climate change be intensified globally.

Climate Change Tipping Points in the Arctic

In “Abrupt climate change in the Arctic,” University of Western Australia (UWA) Ocean Institute researchers lead by director and Winthrop Professor Carlos Duarte found that the Arctic is warming at a rate three times faster than the global average, which has caused Arctic summer sea ice to melt and recede at a pace faster than researchers have forecast.

Arctic summer sea ice may be limited to the the waters off northern Greenland and Ellesmere Island in as short a period as the next decade, and is likely to disappear entirely by the middle of the century, according to a WA News report. The warming’s occurring so fast that it’s not only threatening Arctic ecosystems and traditional ways of life, the Arctic may change from being a net carbon sink to a net source of greenhouse gas emissions.

The fast warming Arctic is opening up new sea lanes and a bonanza of resource exploration and exploitation, as well as political controversy over resource rights. However, faster than anticipated warming and melting will also have “abrupt knock-on effects” across major world cities in northern mid-latitudes, a list that includes Beijing, Berlin, London, Moscow, New York and Tokyo. Tentatively linked is the occurrence of much colder winters in Europe.

Warming of Western Ocean Boundary Currents

Also published in Nature Climate Change, “Enhanced warming over the global subtropical western boundary currents,” is a global study of fast-moving, long-distance ocean currents, such as the Gulfstream, that distribute heat and moisture from warming tropical ocean waters globally.

Moving along the western boundaries of the world’s ocean basins, changes in water temperature of these currents also have significant, large-scale effects on climate globally. Releasing heat and moisture on their way from the equator to the poles, they affect atmospheric jet streams and mid-latitude storms and patterns, as well as ocean absorption of carbon dioxide.

Reconstructing and re-examining data sets using new methods, the research team found that “the post-1900 surface ocean warming rate over the path of these currents is two to three times faster than the global mean surface ocean warming rate. The accelerated warming is associated with a synchronous poleward shift and/or intensification of global subtropical boundary currents in conjunction with a systematic change in winds over both hemispheres.”

The faster than expected warming of these long-distance, poleward moving ocean currents “may reduce the ability of the oceans to absorb anthropogenic carbon dioxide over these regions,” according to the report’s authors. “Uncertainties in detection and attribution of these warming trends remain,” they note, “pointing to a need for a long-term monitoring network of the global western boundary currents and their extensions.”

The Oceanic Conveyor Belt and Climate Change

Though not stated by the authors, the increasing incidence of unusual extreme storms, such as 2011’s Hurricane Irene, which carried as far north as the US’ mid-Atlantic and New England regions, and Typhoon Washi, which struck the southern Philippine island of Mindanao, may be evidence of the faster than expected melting of Arctic ice and faster than expected warming of western ocean boundary currents.

Moreover, the changes in both Arctic sea ice and western boundary currents are both aspects of what’s now known as the “oceanic conveyor belt” – scientific knowledge that’s come to us thanks to groundbreaking hypothesizing, testing and research performed by Wallace Broecker.

The abruptness and scale of the climate changes that increasingly appear to be headed our way warrant much greater attention by world leaders and policy makers. While exaggerated for dramatic effect, they bring to mind the popular disaster film, “The Day after Tomorrow,” the science of which is based on a shutting down of the oceanic conveyor belt Broecker first theorized, and the occurrence of world-changing super-storms that bring on a new Ice Age in a matter of months.

As UWA’s Prof. Duarte was quoted as saying, “We need to stop debating the existence of tipping points in the Arctic and start managing the reality of dangerous climate change.”

Image credit: NASA Ocean Motion

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