Category: News

A surprising new picture of ocean circulation could have major consequences for climate science

By Chris Mooney

Some experts say the Atlantic Ocean circulation is already slowing down — but we’re just beginning to learn how it really works.

It may be the biggest wild card in the climate system. Scientists have long feared that the so-called “overturning” circulation in the Atlantic Ocean could slow down or even halt due to climate change — a change that would have enormous planetary consequences.

But at the same time, researchers have a limited understanding of how the circulation actually works, since taking measurements of its vast and remote currents is exceedingly difficult. And now, a major new research endeavor aimed at doing just that has suggested a dramatic revision of our understanding of the circulation itself.

A new 21-month series of observations in the frigid waters off Greenland has led to the discovery that most of the overturning — in which water not only sinks but returns southward again in the ocean depths — occurs to the east, rather than to the west, of the enormous ice island. If that’s correct, then climate models that suggest the circulation will slow as the climate warms may have to be revised to take this into account.

The magnitude of the scientific surprise, on a scale of 1 to 10, is pretty large, said Susan Lozier, an oceanographer at Duke University who was lead author of the research published Thursday in Science.

Read full article: https://www.washingtonpost.com/climate-environment/2019/01/31/surprising-new-picture-ocean-circulation-could-have-major-consequences-climate-science/

Ocean mixing that drives climate found in surprise location

By SETH BORENSTEIN

WASHINGTON (AP) — One of the key drivers of the world’s climate is an area in the North Atlantic Ocean where warmer and colder water mix and swirl. When scientists went for their first close look at this critical underwater dynamo, they found they were looking in the wrong place.

By hundreds of miles.

The consequences are not quite yet understood, but eventually it could change forecasts of one of the worst-case global warming scenarios — still considered unlikely this century — in which the mixing stops and climate chaos ensues.

It’s called the Atlantic Meridional Overturning Circulation , and scientists describe it as a giant ocean conveyor belt that moves water from Greenland south to beyond the tip of Africa and into the Indian Ocean.

Read full article: https://apnews.com/article/climate-science-oceans-indian-ocean-north-america-595bfe2060ef46d49d2417082e3cbd18

Climate change might not slow ocean circulation as much as thought

Observations over 21 months cast doubt on ideas of what drives Atlantic Ocean ‘conveyor belt’

By Carolyn Gramling

New findings from an international ocean observing network are calling into question the long-standing idea that global warming might slow down a big chunk of the ocean’s “conveyor belt.” The first 21 months of data from sensors moored across much of the North Atlantic are giving new insight into what controls the strength of the Atlantic Meridional Overturning Circulation, a system of currents that redistributes heat around much of the Western Hemisphere.

Researchers had thought the strength of that circulation, known by the acronym AMOC, was largely influenced by the sinking of cold freshwater in the Labrador Sea, between Greenland and Canada. And climate simulations suggest that the sea’s deepwater formation might slow as the world continues to warm — which also could slow down the entire Atlantic current system and possibly make temperatures on land in the northeastern United States and the United Kingdom plunge. That concept inspired the (otherwise unrealistic) 2004 climate apocalypse film The Day After Tomorrow.

Read full article: https://www.sciencenews.org/article/climate-change-might-not-slow-ocean-circulation-much-thought

How Climate Change Could Jam The World’s Ocean Circulation

BY NICOLA JONES

Scientists are closely monitoring a key current in the North Atlantic to see if rising sea temperatures and increased freshwater from melting ice are altering the “ocean conveyor belt” — a vast oceanic stream that plays a major role in the global climate system.

Susan Lozier is having a busy year. From May to September, her oceanographic team is making five research cruises across the North Atlantic, hauling up dozens of moored instruments that track currents far beneath the surface. The data they retrieve will be the first complete set documenting how North Atlantic waters are shifting — and should help solve the mystery of whether there is a long-term slowdown in ocean circulation. “We have a lot of people very interested in the data,” says Lozier, a physical oceanographer at Duke University.

A similar string of moorings across the middle of the Atlantic, delving as deep as 3.7 miles from the Canary Islands to the Bahamas, has already detected a disturbing drop in this ocean’s massive circulation pattern. Since those moorings were installed in 2004, they have seen the Atlantic current wobble and weaken by as much as 30 percent, turning down the dial on a dramatic heat pump that transports warmth toward northern Europe. Turn that dial down too much and Europe will go into a deep chill.

Read full article: https://e360.yale.edu/features/will_climate_change_jam_the_global_ocean_conveyor_belt

Atlantic Current Strength Declines

By Quirin Schiermeier

More data are needed to determine whether the slowing is a result of human-induced climate change

The marked slowdown in the past decade of the warm Atlantic Ocean currents that bring mild weather to northwestern Europe may be caused by natural variation and not anthropogenic climate change, as has been previously suggested.

The Atlantic Meridional Overturning Circulation (AMOC) is part of the great ocean ‘conveyor belt’ that ceaselessly circulates sea water, heat and nutrients around the globe. In particular, it transports large amounts of warm water from the tropics to the poles, warming the British Isles and maritime northern Europe along the way (see ‘Current affair’). But since 2004, ocean sensors have detected a significant decline in the strength of the currents and a cooling of the subtropical Atlantic as a result. From mid-2009 to mid-2010, for example, the circulation slowed to two-thirds of its usual strength — and some oceanographers suggested that the drop caused the harsh weather in the United Kingdom and western Europe that winter (see Nature 497, 167–168; 2013).

Read full article: https://www.scientificamerican.com/article/atlantic-current-strength-declines/