Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

North Atlantic warming tied to natural variability; but global warming may be at play elsewhere

07.01.2008
A Duke University-led analysis of available records shows that while the North Atlantic Ocean’s surface waters warmed in the 50 years between 1950 and 2000, the change was not uniform. In fact, the subpolar regions cooled at the same time that subtropical and tropical waters warmed.

This striking pattern can be explained largely by the influence of a natural and cyclical wind circulation pattern called the North Atlantic Oscillation (NAO), wrote authors of a study published Thursday, Jan. 3, in Science Express, the online edition of the journal Science.

Winds that power the NAO are driven by atmospheric pressure differences between areas around Iceland and the Azores. “The winds have a tremendous impact on the underlying ocean,” said Susan Lozier, a professor of physical oceanography at Duke’s Nicholas School of the Environment and Earth Sciences who is the study’s first author.

Other studies cited in the Science Express report suggest human-caused global warming may be affecting recent ocean heating trends. But Lozier and her coauthors found their data can’t support that view for the North Atlantic. “It is premature to conclusively attribute these regional patterns of heat gain to greenhouse warming,” they wrote.

“The take-home message is that the NAO produces strong natural variability,” said Lozier in an interview. “The simplistic view of global warming is that everything forward in time will warm uniformly. But this very strong natural variability is superimposed on human-caused warming. So researchers will need to unravel that natural variability to get at the part humans are responsible for.”

In research supported by the National Science Foundation in the United States and the Natural Environment Research Council in the United Kingdom, her international team analyzed 50 years of North Atlantic temperature records collected at the National Oceanic Data Center in Washington, D.C.

To piece together the mechanisms involved in the observed changes, their analysis employed an ocean circulation model that predicts how winds, evaporation, precipitation and the exchange of heat with the atmosphere influences the North Atlantic’s heat content over time. They also compared those computer predictions to real observations “to test the model’s skill,” the authors wrote.

Her group’s analysis showed that water in the sub-polar ocean –- roughly between 45 degrees North latitude and the Arctic Circle –- became cooler as the water directly exchanged heat with the air above it.

By contrast, NOA-driven winds served to “pile up” sun-warmed waters in parts of the subtropical and tropical North Atlantic south of 45 degrees, Lozier said. That retained and distributed heat at the surface while pushing underlying cooler water further down.

The group’s computer model predicted warmer sea surfaces in the tropics and subtropics and colder readings within the sub-polar zone whenever the NAO is in an elevated state of activity. Such a high NAO has been the case during the years 1980 to 2000, the scientists reported.

“We suggest that the large-scale, decadal changes...associated with the NAO are primarily responsible for the ocean heat content changes in the North Atlantic over the past 50 years,” the authors concluded.

However, the researchers also noted that this study should not be viewed in isolation. Given reported heat content gains in other oceans basins, and rising air temperatures, the authors surmised that other parts of the world's ocean systems may have taken up the excess heat produced by global warming.

“But in the North Atlantic, any anthropogenic (human-caused) warming would presently be masked by such strong natural variability,” they wrote.

Monte Basgall | EurekAlert!
Further information:
http://www.duke.edu

More articles from Ecology, The Environment and Conservation:

nachricht Study suggests LEGO bricks could survive in ocean for up to 1,300 years
17.03.2020 | University of Plymouth

nachricht Wearing clothes could release more microfibers to the environment than washing them
12.03.2020 | University of Plymouth

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Junior scientists at the University of Rostock invent a funnel for light

Together with their colleagues from the University of Würzburg, physicists from the group of Professor Alexander Szameit at the University of Rostock have devised a “funnel” for photons. Their discovery was recently published in the renowned journal Science and holds great promise for novel ultra-sensitive detectors as well as innovative applications in telecommunications and information processing.

The quantum-optical properties of light and its interaction with matter has fascinated the Rostock professor Alexander Szameit since College.

Im Focus: Stem Cells and Nerves Interact in Tissue Regeneration and Cancer Progression

Researchers at the University of Zurich show that different stem cell populations are innervated in distinct ways. Innervation may therefore be crucial for proper tissue regeneration. They also demonstrate that cancer stem cells likewise establish contacts with nerves. Targeting tumour innervation could thus lead to new cancer therapies.

Stem cells can generate a variety of specific tissues and are increasingly used for clinical applications such as the replacement of bone or cartilage....

Im Focus: Artificial solid fog material creates pleasant laser light

An international research team led by Kiel University develops an extremely porous material made of "white graphene" for new laser light applications

With a porosity of 99.99 %, it consists practically only of air, making it one of the lightest materials in the world: Aerobornitride is the name of the...

Im Focus: Cross-technology communication in the Internet of Things significantly simplified

Researchers at Graz University of Technology have developed a framework by which wireless devices with different radio technologies will be able to communicate directly with each other.

Whether networked vehicles that warn of traffic jams in real time, household appliances that can be operated remotely, "wearables" that monitor physical...

Im Focus: Peppered with gold

Research team presents novel transmitter for terahertz waves

Terahertz waves are becoming ever more important in science and technology. They enable us to unravel the properties of future materials, test the quality of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“4th Hybrid Materials and Structures 2020” takes place over the internet

26.03.2020 | Event News

Most significant international Learning Analytics conference will take place – fully online

23.03.2020 | Event News

MOC2020: Fraunhofer IOF organises international micro-optics conference in Jena

03.03.2020 | Event News

 
Latest News

3D printer sensors could make breath tests for diabetes possible

27.03.2020 | Power and Electrical Engineering

TU Bergakademie Freiberg researches virus inhibitors from the sea

27.03.2020 | Life Sciences

The Venus flytrap effect: new study shows progress in immune proteins research

27.03.2020 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>