Scientists Puzzled by Slowing of Atlantic Conveyor Belt, Warn of Abrupt Climate Change
Scientists are increasingly warning of the potential that a shutdown, or even significant slowdown, of the Atlantic conveyor belt could lead to abrupt climate change, a shift in Earth’s climate that can occur within as short a timeframe as a decade but persist for decades or centuries.
By Mike Gaworecki / news.mongabay.com
May 30, 2016

Scientists in the Labrador Sea recently made the first retrieval of data from one of 53 lines moored to the sea floor and studded with instruments that have been monitoring the ocean’s circulatory system since 2014.

Held taut by submerged buoys, these moorings are arrayed from Labrador to Greenland and Scotland. In total, five research cruises are planned for this spring and summer to fetch the data the moorings are busy collecting.

The instrument array, known as the Overturning in the Subpolar North Atlantic Program (OSNAP), measures salinity, temperature, and current velocity of the surrounding water, data that is vital to understanding a set of powerful currents with far-reaching effects on the global climate. These currents are known as the Atlantic Meridional Overturning Circulation (AMOC) — or, more popularly, “the Atlantic conveyor belt” — and they have “mysteriously” slowed down over the past decade, according to Eric Hand, author of a Science article published this month.

Scientists are increasingly warning of the potential that a shutdown, or even significant slowdown, of the Atlantic conveyor belt could lead to abrupt climate change, a shift in Earth’s climate that can occur within as short a timeframe as a decade but persist for decades or centuries.

North Atlantic waters, such as the Greenland, Irminger, and Labrador Seas, are especially salty when compared with water in other parts of the world’s oceans. When AMOC currents, like the Gulf Stream, bring warmer waters from the south to the North Atlantic, the water cools down, releases its heat to the atmosphere, becomes colder, and sinks, since saltier water is denser than fresher water and cold water is denser than warm water.

In a process called “thermohaline circulation” (“thermos” is the Greek word for heat, while “halos” is the word for salt), this cold, salty water then slowly flows back down into the South Atlantic and eventually makes its way throughout the world’s oceans. At the same time, warm, salty tropical surface waters are drawn northward, where they replace the sinking cold water.

1024px-Thermohaline_Circulation_2
This map shows the pattern of thermohaline circulation also known as “meridional overturning circulation”. This collection of currents is responsible for the large-scale exchange of water masses in the ocean, including providing oxygen to the deep ocean. The entire circulation pattern takes ~2000 years. Image via Wikimedia Commons.

In other words, the dynamic at play in the North Atlantic seas are an important driver of the ocean’s circulation system, which is why the region was selected for the OSNAP instrument array. Two other arrays that have been deployed in different waters have already produced some strange results that scientists are eager to learn more about.

“Models suggest that climate change should weaken the AMOC as warmer Arctic temperatures, combined with buoyant freshwater from Greenland’s melting ice cap, impede the formation of deep currents,” Hand wrote in the Science article. “But so far, limited ocean measurements show the AMOC to be far more capricious than the models have been able to capture.”

An array deployed in 2004 between Florida and the Canary Islands, for instance, showed “unexpectedly wild swings” in the strength of the AMOC currents from month to month, Hand reported. From 2009 to 2010, the average strength of the AMOC dropped by about 30 percent, causing warmer waters to remain in the tropics rather than being carried northward.

“The consequences included an unusually harsh European winter, a strong Atlantic Basin hurricane season, and — because a strong AMOC keeps water away from land — an extreme sea level rise of nearly 13 centimeters along the North American coast north of New York City,” Hand said.

Over its first decade of operation, the Florida-to-Canary Islands subtropical array recorded a 25 percent decline in the AMOC’s average strength, which is an order of magnitude more than models suggested could occur due to the effects of climate change.

Meric Srokosz, an oceanographer at the UK’s University of Southampton and the science coordinator for the U.K.-funded portion of the array, told Hand that scientists suspect some natural variation is to blame in the dropoff of the AMOC’s strength, including the 60- to 70-year cycle of varying sea temperatures called the Atlantic Multidecadal Oscillation. Initial analysis of the latest, unpublished data from the array shows the AMOC’s average strength has leveled out, but is still well below where it started in 2004.

“It will take another decade of measurements to separate the climate change effect from natural variability,” Hand wrote.

Threat of abrupt climate change

Models have suggested that there is a threshold below which the AMOC could suddenly shut down altogether — “the doomsday scenario of a frozen Europe exploited in the 2004 disaster movie The Day After Tomorrow,” as Hand put it. “Many climate models suggest that the AMOC should be stable over the long term in a warming world, but plenty of evidence from the recent geological past confirms that the conveyor belt can slow down significantly.”

As far back as 2003, Robert Gagosian, who was then the President and Director of the Woods Hole Oceanographic Institution (WHOI) in Woods Hole, Massachusetts (he’s now President Emeritus), warned that we ignore the threat of abrupt climate change induced by a slowing or shutdown of the AMOC at our own peril.

“[T]he debate on global change has largely failed to factor in the inherently chaotic, sensitively balanced, and threshold-laden nature of Earth’s climate system and the increased likelihood of abrupt climate change,” he wrote in a post on the WHOI website.

Speculation about the future impacts of climate change focus on forecasts by the UN’s Intergovernmental Panel on Climate Change, which projects gradual global warming of 1.4 to 5.8-degree Celsius over the next century, Gagosian wrote at the time. That doesn’t appear to have significantly changed, as the Paris Climate Agreement signed in December of last year commits signatory countries to limiting warming to 2 degrees Celsius, with an aspirational goal of limiting it to 1.5 degrees Celsius — and there’s little to no mention of how the world will fend off the possibility of abrupt climate change.

But we’d be wise to include in our forecasts the potential for relatively sudden, possibly localized climate change induced by thermohaline shutdown, Gagosian argued. “Such a change could cool down selective areas of the globe by 3° to 5° Celsius, while simultaneously causing drought in many parts of the world.”

These abrupt changes could occur even while other regions of the globe continue to warm more gradually, Gagosian said, making it “critical to consider the economic and political ramifications of this geographically selective climate change. Specifically, the region most affected by a shutdown — the countries bordering the North Atlantic — is also one of the world’s most developed.”

CITATION

3.5 ·
1
Trending Today
How Norway Avoided Becoming a Fascist State
George Lakey · 21,022 views today · Instead of falling to the Nazi party, Norway broke through to a social democracy. Their history shows us polarization is nothing to despair over.
Stunning Small Homes Form Part of a Communal Compound for Best Friends
Lighter Side · 13,923 views today · If you’re lucky enough to have longtime friends even as an adult, then you know probably already know how much it means to be able to spend time together. Maybe you even have a...
Where the Term "Redneck" Came From
15 min · 10,804 views today · If you don't know this story, you'll never look at the word the same again.  This is just a window into the sometimes shocking, subversive and untold history of the United...
Without Saying a Word This 6 Minute Clip From Samsara Will Make You Speechless
6 min · 6,965 views today · Can you put this video into words? It's a clip from the phenomenal documentary Samsara, directed by Ron Fricke, who also made Baraka.  If you're interested in watching...
Redneck Revolt Presents: A Message to the Patriot Movement
6 min · 5,668 views today · Over the past few weeks, Redneck Revolt has been communicating with a former member of a III% Patriot Militia based out of Ohio. Peter made contact with our organization after...
Voices of Standing Rock
49 min · 5,617 views today · Short stories told by water protectors at Standing Rock, North Dakota. Part 1 - Introduction: Since mid-August 2016, thousands have set up camp near the Standing Rock Sioux...
The Fire Within
Words by Sophie Scholl - Illustrations by Gavin Aung Than · 5,383 views today · Sophie Scholl (1921-1943) was a German activist who is famous for speaking out against the Nazi regime. Scholl was a member of a protest group called The White Rose, which...
The London Anarchist Group Squatting Mansions to Fight Homelessness
6 min · 3,832 views today · London squatting activists ANAL (Autonomous Nation of Anarchist Libertarians) are squatting empty multi-million pound buildings and opening them up to the homeless.
The Most Astounding Fact about the Universe
3 min · 3,472 views today · This is Neil Degrasse Tyson's response when asked to describe the most astounding fact about the universe. Background music is the cinematic orchestra - To build a home.
10 Words Every Girl Should Learn
Soraya Chemaly · 2,790 views today · "Stop interrupting me."  "I just said that." "No explanation needed." In fifth grade, I won the school courtesy prize. In other words, I won an award for being polite. My...
Your Lifestyle Has Already Been Designed (The Real Reason For The Forty-Hour Workweek)
David Cain · 2,590 views today · Well I’m in the working world again. I’ve found myself a well-paying gig in the engineering industry, and life finally feels like it’s returning to normal after my nine months...
The Lessons of Standing Rock
Michael Emero · 2,544 views today · In mid-November of 2016, I was a Water Protector at Standing Rock. At first my goal was to play investigative journalist; documenting then writing about every detail for my...
The Foiled Bomb Plot in Kansas That Didn't Make Trump's Terror List
5 min · 2,283 views today · When a plot by a pro-white militia to bomb a Somali mosque in Kansas was foiled by the FBI last October, the aborted conspiracy received little national coverage - nor did it...
Charles Eisenstein: The Two Great Stories That Give Meaning to Our Lives
6 min · 1,604 views today · What matters in life? Who are we? Every culture has answers to these questions. And the way we answer them has profound effects on the health of people and planet. This is a...
How a Lack of Touch Is Destroying Men
Mark Green · 1,399 views today · Why Men Need More Platonic Touch in their Lives
What Happens When You Rebel Against the Herd
Sofo Archon · 1,240 views today · Are You Truly Living Your Life? You live, but are you living the way you want to live, or the way others want you to live? You choose, but are your choices based on...
John Lennon's "Imagine," Made Into a Comic Strip
John Lennon. Art by Pablo Stanley · 1,002 views today · This is easily the best comic strip ever made.  Pabl
A Hauntingly Beautiful Short Film About Life and Death
5 min · 908 views today · The Life of Death is a touching handdrawn animation about the day Death fell in love with Life.
To Change Everything, Start Everywhere
8 min · 650 views today · To Change Everything, Start Everywhere! The case for complete self-determination—a guide for the furious, the curious, and the pure of heart. To Change Everything: An...
Everything We Think We Know About Addiction Is Wrong
6 min · 572 views today · What causes addiction? Easy, right? Drugs cause addiction. But maybe it is not that simple. This video is adapted from Johann Hari's New York Times best-selling book 'Chasing...
Load More
What's Next
Like us on Facebook?
Scientists Puzzled by Slowing of Atlantic Conveyor Belt, Warn of Abrupt Climate Change