Major Study Rewrites the Driving Source of Atlantic Ocean Circulation – Discover Magazine

By Roni Dengler

Massive volumes of water circulate throughout the Atlantic Ocean and serve as the central drivers of Earth’s climate. Now researchers have discovered that the heart of this circulation is not where they suspected.

“The general understanding has been [that it’s] in the Labrador Sea, which sits between the Canadian coast and the west side of Greenland,” said Susan Lozier, a physical oceanographer at Duke University in Durham, North Carolina, who led the new research. “What we found instead was that … the bulk [of it] is taking place from the east side of Greenland all the way over to the Scottish shelf.”

The discovery will help improve global climate models.

Read full article: http://blogs.discovermagazine.com/d-brief/2019/02/01/amoc-ocean-current-driving-cause/#.XFm3Iy2ZNp_

Ocean mixing that drives climate found in surprise location – AP

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.

Warm, salty water near the surface moves north and mixes with cold, fresher water near Greenland. As that water cools and sinks it drives a slow circulation of the oceans that is critical to global climate, affecting the location of droughts and frequency of hurricanes. It also stores heat-trapping carbon dioxide deep in the ocean. The faster it moves, the more warm water gets sent into the depths to cool.

The area where warm water turns over in the North Atlantic is considered to be the engine of the conveyor belt. Scientists thought it was in the Labrador Sea west of Greenland.

But then a new international science team measured temperature, saltiness and the speed of ocean currents throughout the North Atlantic to try to better understand the conveyor belt. The preliminary results after hundreds of measurements in 21 months found that engine was several hundreds of miles east of where they figured, said study lead author Susan Lozier, an ocean sciences professor at Duke University. The study, published in Thursday’s journal Science, puts it east of Greenland, closer to Scotland.

Read full article: https://www.apnews.com/595bfe2060ef46d49d2417082e3cbd18

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

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.

“For me personally, maybe a 7,” she said. “But I think for the community, it might have been more like a 9.”

Read full articlehttps://www.washingtonpost.com/climate-environment/2019/01/31/surprising-new-picture-ocean-circulation-could-have-major-consequences-climate-science/?utm_term=.a6d7bc06d6e6

Waters west of Europe drive ocean overturning, key for regulating climate

by Tim Lucas

DURHAM, N.C. — A new international study finds that the Atlantic meridional overturning circulation (MOC), a deep-ocean process that plays a key role in regulating Earth’s climate, is primarily driven by cooling waters west of Europe.

In a departure from the prevailing scientific view, the study shows that most of the overturning and variability is occurring not in the Labrador Sea off Canada, as past modeling studies have suggested, but in regions between Greenland and Scotland. There,  warm, salty, shallow waters carried northward from the tropics by currents and wind, sink and convert into colder, fresher, deep waters moving southward through the Irminger and Iceland basins.

Overturning variability in this eastern section of the ocean was seven times greater than in the Labrador Sea, and it accounted for 88 percent of the total variance documented across the entire North Atlantic over the 21-month study period.

These findings, unexpected as they may be, can help scientists better predict what changes might occur to the MOC and what the climate impacts of those changes will be, said Susan Lozier, the Ronie-Rochele Garcia-Johnson Professor of Earth and Ocean Sciences at Duke University’s Nicholas School of the Environment.

“To aid predictions of climate in the years and decades ahead, we need to know where this deep overturning is currently taking place and what is causing it to vary,” said Lozier, who led the international observational study that produced the new data.

“Overturning carries vast amounts of anthropogenic carbon deep into the ocean, helping to slow global warming,” said co-author Penny Holliday of the National Oceanography Center in Southampton, U.K. “The largest reservoir of this anthropogenic carbon is in the North Atlantic.”

“Overturning also transports tropical heat northward,” Holliday said, “meaning any changes to it could have an impact on glaciers and Arctic sea ice. Understanding what is happening, and what may happen in the years to come, is vital.”

Scientists from 16 research institutions from seven countries collaborated on the new study. They published their peer-reviewed findings Feb. 1 in Science.

“I cannot say enough about the importance of this international collaboration to the success of this project,” Lozier said. “Measuring the circulation in the subpolar North Atlantic is incredibly challenging so we definitely needed an ‘all hands on deck’ approach.”

This paper is the first from the $32 million, five-year initial phase of the OSNAP (Overturning in the Subpolar North Atlantic Program) research project, in which scientists have deployed moored instruments and sub-surface floats across the North Atlantic to measure the ocean’s overturning circulation and shed light on the factors that cause it to vary. Lozier is lead investigator of the project, which began in 2014.

“As scientists, it is exciting to learn that there are more pieces to the overturning puzzle than we first thought,” said co-author Johannes Karstensen of the GEOMAR Helmholtz Centre for Ocean Research Kiel, in Germany.

“Though the overturning in the Labrador Sea is smaller than we expected, we have learned that this basin plays a large role in transporting freshwater from the Arctic,”  Karstensen said. “Continued measurements in that basin will be increasingly important,” as the Arctic changes unexpectedly.

https://nicholas.duke.edu/about/news/waters-west-europe-drive-ocean-overturning-key-regulating-climate

Susan Lozier to serve as President-elect of the American Geophysical Union

by Tim Lucas

“Susan Lozier, Ronie-Richele Garcia-Johnson Professor of Earth and Ocean Sciences at Duke University’s Nicholas School of the Environment, has been elected president-elect of the American Geophysical Union (AGU).

AGU is a professional society of atmospheric and ocean sciences, solid-Earth sciences, hydrologic sciences and space sciences, and has more than 62,000 members in 144 countries.  Its activities are focused on the organization and dissemination of scientific information in the interdisciplinary and international field of geophysics.

Lozier will begin her two-year term as president-elect on Jan. 1, 2019, and then serve a two-year term as AGU president beginning in 2021.”

https://nicholas.duke.edu/about/news/susan-lozier-serve-president-elect-american-geophysical-union

Nature and Science both highlight North Atlantic research lead by Lozier

by Tim Lucas, 919/613-8084, tdlucas@duke.edu

“Two of the world’s most influential science journals, Nature and Science, this week highlighted findings from an international research project led by Susan Lozier

You can read the Science article here.

You can read the Nature article here.

Lozier leads the Overturning in the Subpolar North Atlantic Program (O-SNAP), a seven-nation, $35 million initiative, launched in 2013, to shed light on changes occurring in the Atlantic meridional overturning circulation (AMOC), which plays a major role in shaping Earth’s climate.

Last week, she and her O-SNAP colleagues presented initial data from the project to scientists gathered at the American Geophysical Union’s Ocean Science meeting in Portland, Ore.

Their findings, though still preliminary, reveal strong variability in AMOC currents and suggest that ocean currents east of Greenland play unexpectedly large roles in the total AMOC flow. By contrast, most climate models have emphasized the role played by currents west of Greenland in the Labrador Sea.

These new insights add to scientists’ understanding of the complex inner workings of the AMOC and, with further research, could help improve the accuracy of climate models.

Lozier is Ronie-Richelle Garcia-Johnson Professor of Earth and Ocean Sciences at the Nicholas School.”

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