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January 31 2012

18:35

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


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

June 28 2011

22:18

Shifting Ocean Currents Drive Accelerating Ice Melt of Antarctic Ice Shelf


Shifting currents are eating away at the Pine Island Ice ShelfShifting ocean currents appear to be accelerating ice melt of the Pine Island Glacier Ice Shelf in western Antarctica.

According to research published this week in the journal Nature Geoscience, scientists from the Lamont-Doherty Earth Observatory at Columbia University have recorded ocean currents driving at and underneath the ice shelf, carving out an expanding cavity from underneath the glacier, creating a growing impact 50 percent greater than when scientists began monitoring the region in the early 1990′s.

Researchers estimate that 2.5 miles of glacier now slide into the sea annually.

In a summary report, scientists say the rapid rate of deterioration of the Pine Island Glacier could significantly impact coastlines around the globe:

“Pine Island Glacier, among other ice streams in Antarctica, is being closely watched for its potential to redraw coastlines worldwide. Global sea levels are currently rising at about 3 millimeters (.12 inches) a year. By one estimate, the total collapse of Pine Island Glacier and its tributaries could raise sea level by 24 centimeters (9 inches).”

The accelerating trend of ice can’t be accounted for solely from the modest 0.2 degree Celsius increase in surrounding ocean temperature observed at Pine Island over the past fifteen years. Scientists point to evidence of stronger winds in the Southern ocean that are shifting currents, pushing warmer waters from the tropics toward the ice shelf. That warmer water pushes further underneath the glacier, leading to the observed rate of destabilization and the growing chasm underneath.

Authors of the report cite the phenomenon impacting western Antarctica as further indication of the “multiplier effect” climate change has on regional ecosystems. Eric Rignot, a senior scientist a the NASA Jet Propulsion Laboratory who participated in the study, explained in a statement coinciding with the publication of the research:

“The main reason the glaciers are thinning in this region, we think, is the presence of warm waters,” said Rignot. “Warm waters did not get there because the ocean warmed up, but because of subtle changes in ocean circulation. Ocean circulation is key. This study reinforces this concept.”

Additional sources and further reading:
Climatewire (subscription required)

 

Image credit: NASA, courtesy Flickr

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May 19 2011

17:22

Hauling Icebergs to Slake the Earth's Thirst

Wouldn't it be nice to haul a few icebergs to someplace short on water -- southern Spain, perhaps, or western Australia -- and melt them for drinking water?

June 03 2010

21:44
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