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.”

View full details

The Future Of Hurricanes

From WUNC – North Carolina Public Radio

“Floodwaters from Hurricane Harvey still filled the streets in Texas when Hurricane Irma blew ashore in Florida. As the latest storm moves toward North Carolina, Duke scientists explore whether these rare weather events are growing more frequent or more extreme. They also analyze how communities and governments can become more resilient.

Host Frank Stasio talks with oceanographer Susan Lozier, professor of earth and ocean sciences in Duke University’s Nicholas School of the Environment, about whether climate change is to blame and what other weather events could occur as a result of changing ocean conditions.”

Listen to Interview 

How scientists reacted to the US leaving the Paris climate agreement

What the United States’ departure from the historic pact means for efforts to fight global warming.

Nature rounds up reaction from researchers around the world to US President Donald Trump’s decision to pull the United States out of the Paris climate agreement.

Susan Lozier, oceanographer at Duke University in Durham, North Carolina:

Trump’s decision is as short-sighted as it is disheartening. The oceans already hold about 35% of the carbon dioxide that has been released to the atmosphere since the Industrial Revolution. Nothing good for the ocean and the life it contains comes from this storage. Whether you simply admire marine life or count on it for your livelihood, this decision shouldn’t sit well. An already fragile ocean is further imperilled.

View full article

Susan Lozier and Drew Shindell Named AGU Fellows

DURHAM, N.C. – Two faculty members at Duke University’s Nicholas School of the Environment have been named Fellows of the American Geophysical Union (AGU).

Susan Lozier, professor of physical oceanography, and Drew Shindell, professor of climate sciences, are among 62 scientists selected as AGU Fellows this year.

Election as an AGU Fellow is an honor reserved for individuals who have made exceptional scientific contributions and attained eminence in the fields of Earth and space sciences. AGU bylaws restrict the annual honor to no more than 0.1 percent of the organization’s total membership.

Lozier is a physical oceanographer with interests in large-scale ocean circulation and its links to global climate change.

She currently is leading a $32 milllion international initiative, the U.S.-led Overturning in the Subpolar North Atlantic Program (OSNAP), to deploy a new observing system in the subpolar region of the North Atlantic to more accurately measure the ocean’s overturning circulation, a key component of the global climate system. Her studies have appeared in Science, Nature and other top peer-reviewed journals. A member of the Duke faculty since 1992, she was named a Fellow of the American Meteorological Society in 2008.

Shindell, formerly a climatologist at the NASA Goddard Institute for Space Studies, joined the Nicholas School faculty earlier this year. He is widely hailed for his work using climate models to investigate connections between climate change and chemical changes in the atmosphere, including the depletion of Earth’s ozone layer. His studies have appeared in Nature, Science and numerous other leading journals.

Lozier, Shindell and the other new Fellows will be recognized during a ceremony on December 17 at the AGU Fall Meeting in San Francisco.

Ana Barros, professor of civil and environmental engineering at Duke’s Pratt School of Engineering, was also named a 2014 AGU Fellow.

http://nicholas.duke.edu/news/susan-lozier-and-drew-shindell-named-agu-fellows

 

Changes in Ocean Circulation Focus of $16 Million Project

DURHAM, N.C. — Oceanographers from Duke University, Woods Hole Oceanographic Institution and the University of Miami have received $16 million in grants from the National Science Foundation for the deployment of a new observing system in the subpolar region of the North Atlantic. The observing system will measure the ocean’s overturning circulation, a key component of the global climate system.

The five-year initiative is part of the $32 million, U.S.-led Overturning in the Subpolar North Atlantic Program (OSNAP). International collaborators include scientists from Canada, the United Kingdom, Germany, France and the Netherlands.

The goal of the program is to simultaneously measure the surface ocean currents that carry heat northward toward the Arctic Ocean and the deep ocean currents that carry cooler waters southward toward the equator. Together, these currents form the overturning circulation that plays a role in redistributing heat from the equator to the poles. Recent modeling studies have shown that changes in this circulation would have a critical impact on temperatures and precipitation in North America, Europe and Africa.

“In addition to measuring the variability of the ocean overturning, OSNAP is strongly focused on understanding what factors create those changes,” said Susan Lozier, the international project lead and a physical oceanographer at Duke’s Nicholas School of the Environment.

“For decades, oceanographers have understood the overturning circulation to be highly susceptible to changes in the temperature and salinity of surface waters in the subpolar North Atlantic. With increasing ocean temperatures, and increased ice melt that impacts the salinity of the surface waters, it is timely to establish just how climate changes might affect the strength of the overturning circulation,” Lozier explained.

Likewise, the OSNAP array affords the opportunity to study how overturning changes impact the environment. OSNAP measurements will facilitate the study of how changes in the northward flow of warm water affects the reduction of Arctic sea ice and the shrinking of the Greenland Ice Sheet.

Duke, Woods Hole and Miami oceanographers, along with their international partners, will deploy moored instruments and sub-surface floats across the subpolar North Atlantic during the summer of 2014. The measurement period will last until 2018.

The array of instruments will stretch along two lines, from Labrador to southern Greenland and from Greenland east to Scotland. The instruments will provide the scientists with continuous measurements of surface-to-bottom water temperature, salinity and velocities in areas of the subpolar ocean that historically have been under-sampled. Trajectories of the subsurface floats will provide the first look at deep-water pathways in the North Atlantic.

The OSNAP measurement system complements a joint U.K. and U.S. program that has been measuring the overturning circulation in the subtropical North Atlantic since 2004. Differences and similarities in these measures will provide oceanographers insight into the working of the ocean’s overturning.

Overturning measures are also critical for an understanding of the ocean’s continued ability to act as one of Earth’s most important carbon sinks.

Surface waters absorb heat-trapping carbon dioxide from Earth’s atmosphere. When cold, dense south-flowing waters from subpolar regions sink, they carry the surface water — and much of the CO2 it contains — into the ocean’s depths, where it is no longer available to heat Earth’s climate.

“Because the storage of carbon at depth is linked to the overturning circulation, our OSNAP measures take on added importance,” Lozier said. “A critical question for climate scientists today is: How much carbon will continue to be stored in the ocean?”

The OSNAP program was designed at an international workshop Lozier led at Duke in April 2010.

Principal U.S. investigators of the new program are Amy Bower, Fiamma Straneo and Robert Pickart, scientists in physical oceanography at Woods Hole Oceanographic; William Johns, professor of meteorology and physical oceanography at the University of Miami; and Lozier.

OSNAP will be one of the first projects to make use of the new, NSF-funded Ocean Observatories Initiative’s (OOI) array of moored sensors that will be installed in the Irminger Sea, off the southern tip of Greenland, in 2014. The Irminger Sea is one of four planned global observing sites of the OOI program, a networked infrastructure of sensor systems measuring physical, chemical, geological and biological variables in high-latitude and coastal ocean locations as well as at the seafloor.

The OSNAP project is funded by two NSF grants, OCE-1259102 and OCE-1259103.

For more information about OSNAP and related projects, go to www.o-snap.org