Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Satellites Record Weakening North Atlantic Current

19.04.2004


A North Atlantic Ocean circulation system weakened considerably in the late 1990s, compared to the 1970s and 1980s, according to a NASA study.


Dominant Pattern of Variability of the Sea-surface Height in the 1990s

This image shows the dominant pattern of variability of the sea-surface height in the 1990s. The slope of the sea-surface height is in balance with ocean currents, much in the way weather maps of pressure relate to winds. The large blue region in the northern Atlantic represents a slowing of the counter-clockwise,
cyclonically circulating subpolar gyre. For this image, the researchers used TOPEX/Poseidon data, which has been combined with ERS-1/2 data into the NASA Pathfinder data set. The Pathfinder data set also includes the Seasat and Geosat data which are referenced to TOPEX/Poseidon data. The next few years will reveal how sea surface height is going to evolve as the altimetric time series continues with JASON-1 observations. Credit: Sirpa Hakkinen, NASA GSFC


Terra MODIS Sea Surface Temperatures for North Atlantic Ocean

This image of North Atlantic Ocean sea surface temperatures represents an eight-day composite from Sept 6 - Sept 13, 2001 from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on Terra. The red and orange colors represent warmer water, while the blue shades represent cold water in the higher latitudes. The Gulf Stream is evident along the U.S. eastern seaboard. The color bar is in units of degrees Celsius. Credit: Ronald Vogel, SAIC for NASA GSFC



Sirpa Hakkinen, lead author and researcher at NASA’s Goddard Space Flight Center, Greenbelt, Md. and co-author Peter Rhines, an oceanographer at the University of Washington, Seattle, believe slowing of this ocean current is an indication of dramatic changes in the North Atlantic Ocean climate. The study’s results about the system that moves water in a counterclockwise pattern from Ireland to Labrador were published on the Internet by the journal Science on the Science Express Web site at:

http://www.sciencexpress.org or http://www.aaas.org


The current, known as the sub polar gyre, has weakened in the past in connection with certain phases of a large-scale atmospheric pressure system known as the North Atlantic Oscillation (NAO). But the NAO has switched phases twice in the 1990s, while the subpolar gyre current has continued to weaken. Whether the trend is part of a natural cycle or the result of other factors related to global warming is unknown.

"It is a signal of large climate variability in the high latitudes," Hakkinen said. "If this trend continues, it could indicate reorganization of the ocean climate system, perhaps with changes in the whole climate system, but we need another good five to 10 years to say something like that is happening." Rhines said, "The subpolar zone of the Earth is a key site for studying the climate. It’s like Grand Central Station there, as many of the major ocean water masses pass through from the Arctic and from warmer latitudes. They are modified in this basin. Computer models have shown the slowing and speeding up of the subpolar gyre can influence the entire ocean circulation system."

Satellite data makes it possible to view the gyre over the entire North Atlantic basin. Measurements from deep in the ocean, using buoys, ships and new autonomous "robot" Seagliders, are important for validating and extending the satellite data. Sea-surface height satellite data came from NASA’s Seasat (July, August 1978), U.S. Navy’s Geosat (1985 to 1988), and the European Space Agency’s European Remote Sensing Satellite1/2 and NASA’s TOPEX/Poseidon (1992 to present).

Hakkinen and Rhines were able to reference earlier data to TOPEX/Poseidon data, and translate the satellite sea-surface height data to velocities of the subpolar gyre. The subpolar gyre can take 20 years to complete its route. Warm water runs northward through the Gulf Stream, past Ireland, before it turns westward near Iceland and the tip of Greenland.

The current loses heat to the atmosphere as it moves north. Westerly winds pick up that lost heat, creating warmer, milder European winters. After frigid Labrador Sea winters, the water in the current becomes cold, salty and dense, plunges beneath the surface, and heads slowly southward back to the equator. The cycle is sensitive to the paths of winter storms and to the buoyant fresh water from glacial melting and precipitation, all of which are experiencing great change.

While previous studies have proposed winds resulting from the NAO have influenced the subpolar gyre’s currents, this study found heat exchanges from the ocean to the atmosphere may be playing a bigger role in the weakening current. Using Topex/Poseidon sea-surface height data, the researchers inferred Labrador Sea water in the core of the gyre warmed during the 1990s. This warming reduces the contrast with water from warmer southern latitudes, which is part of the driving force for ocean circulation.

The joint NASA-CNES (French Space Agency) Topex/Poseidon oceanography satellite provides high-precision data on the height of the world’s ocean surfaces, a key measure of ocean circulation and heat storage in the ocean.

NASA’s Earth Science Enterprise is dedicated to understanding the Earth as an integrated system and applying Earth System Science to improve prediction of climate, weather and natural hazards using the unique vantage point of space. NASA, the National Oceanic and Atmospheric Administration, and the National Science Foundation funded the study.

Krishna Ramanujan | GSFC
Further information:
http://www.gsfc.nasa.gov/topstory/2004/0415gyre.html

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: It’s All in the Mix: Jülich Researchers are Developing Fast-Charging Solid-State Batteries

There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.

The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Quantum bugs, meet your new swatter

20.08.2018 | Information Technology

A novel synthetic antibody enables conditional “protein knockdown” in vertebrates

20.08.2018 | Life Sciences

Metamolds: Molding a mold

20.08.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>