Subscribe free to our newsletters via your
. 24/7 Space News .




EARTH OBSERVATION
Stalled Weather Systems More Frequent in Decades of Warmer Atlantic
by Maria-Jose Vinas for Goddard Space Flight Center
Greenbelt MD (SPX) Nov 08, 2011


The researchers observed the frequency of blocked weather events in the North Atlantic -from the equator to Greenland- over the entire twentieth century and compared it to the evolution of ocean surface temperatures for the same area.

Slow-moving winter weather systems that can lead to massive snowfalls are more frequent during the decades when the North Atlantic Ocean is warmer than usual, a new NASA study finds.

The study demonstrates that the impacts of such systems, which are often fueled by an atmospheric phenomenon known as atmospheric blocking, go far beyond the atmosphere and can trigger changes in ocean circulation.

Blocking events occur when one of the jet streams -fast-flowing air currents traveling around the Earth in the upper part of the troposphere-pinches off large masses of air from the normal wind flow for an extended period.

These kinks in the jet stream typically last at least five days but can persist for weeks. They can cause weather patterns to stall over one area and fuel floods, droughts, and other extreme weather events.

In the North Atlantic, atmospheric blocking centers generally form over Greenland and Western Europe. A blocking event that took place over Greenland in the winter of 2009-10 ultimately led to intense blizzards in the East Coast of the United States, in an episode popularly known as Snowmageddon.

Now, a team of researchers lead by Sirpa Hakkinen, an oceanographer at NASA Goddard Space Flight Center in Greenbelt, Md., has reanalyzed atmospheric data from the 20th century and concluded that blocking events occurred up to 30 percent more often from the 1930s to the 1960s and during a period that started in the late 1990s and continues to the present.

At first, the researchers thought the increase in blocking events during these periods might be explained by a climatic phenomenon calledthe North Atlantic Oscillation (NAO). The NAO fluctuates between periods of high and low atmospheric pressure, without a predictable pattern, and strongly influences weather in Europe and the United States.

"The NAO is the usual suspect for all atmospheric changes in the northern hemisphere," Hakkinen said.

But since 1996, the NAO has been in an almost a neutral state, while blocking events have continued to be abnormally frequent, especially after 2000.

Hakkinen's team then looked at how a cyclical series of natural changes in sea surface temperatures, known as the Atlantic Multidecadal Ocean Variability (AMV), was behaving in the decades when there were more clusters of blocking events. The AMV switches phases every few decades.

The researchers observed the frequency of blocked weather events in the North Atlantic -from the equator to Greenland- over the entire twentieth century and compared it to the evolution of ocean surface temperatures for the same area.

They then removed the effect that global warming has on water temperatures, and found that decades with more frequent, recurring blocking events in the North Atlantic corresponded to those decades when the North Atlantic Ocean was warmer than usual, as it is now.

The team also found that these short-term weather blocking events impacts beyond the atmosphere and may ultimately alter ocean currents.

A series of connected changes begin because clusters of blocking events can divert the normal track of the storms crossing the Atlantic, which in turn can alter the twisting motion that the wind has on ocean waters, or wind curl. Depending on how wind curl works, it can speed up or slow down the large, circulating currents in the ocean known as gyres.

When a blocking event reverses the rotation of the wind curl, the winds push against the direction of the whirlpool-like North Atlantic subpolar gyre, slowing its rotation. A slower, weaker gyre allows subtropical waters that would normally be trapped in the whirlpool-like flow to escape and move northward.

"These warmer and more saline waters then invade the subpolar ocean and cause a series of impacts," said Peter Rhines, an oceanographer at the University of Washington, Seattle, and co-author of the new study.

"They erode the base of glaciers, contributing to the melting of the Greenland ice sheet. And the change in temperature and freshness of the waters can alter subpolar ecosystems, too."

A better understanding of the linkage between the Atlantic Multidecadal Ocean Variability and blocking events could lead to better weather forecasts and improved seasonal predictions.

"For example, knowing that there's going to be a potential for more blocking events causing more snowfall would not only help people prepare better for the winter; it would be useful with water resources management," said Hakkinen.

Denise Worthen, a researcher with Wyle Information Systems/NASA Goddard Space Flight Center contributed to this study, which NASA funded.

Link to science papee

.


Related Links
-
Earth Observation News - Suppiliers, Technology and Application






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





EARTH OBSERVATION
Landsat's TIRS Instrument Comes Out of First Round of Thermal Vacuum Testing
Greenbelt MD (SPX) Nov 02, 2011
The Thermal Infrared Sensor (TIRS) that will fly on the next Landsat satellite came out of its first round of thermal vacuum testing Tuesday, October 4 at NASA's Goddard Space Flight Center, Greenbelt, Md. The two-month test marked the first time engineers evaluated the fully-assembled instrument at its normal operating temperature, a frigid 43 Kelvin (-382 degrees F). The verdict is that ... read more


EARTH OBSERVATION
Lunar Probe to search for water on Moon

Subtly Shaded Map of Moon Reveals Titanium Treasure Troves

NASA's Moon Twins Going Their Own Way

Titanium treasure found on Moon

EARTH OBSERVATION
Moscow's Mars pioneers hail success, gripe at space rations

Russia aims for first conquest of Mars

Welcome back and thank you, Mars500

Return from virtual flight to Mars

EARTH OBSERVATION
NASA's Future Up In Space

NASA plans 2014 test-flight of deep-space capsule

Voyager 2 to Switch to Backup Thruster Set

Boeing to Build Commercial Spacecraft at Kennedy, Create 550 Jobs

EARTH OBSERVATION
What does the Tiangong 1 space station mean for China

China masters space command, control

China's great big leap skyward

China space prowess benefits world

EARTH OBSERVATION
Campaign Begins For Third Automated Transfer Vehicle Mission To ISS

New Supply Ship Arrives, Departure Preps and Science Under Way

Russian space freighter docks with orbital station

Progress Successfully Docks With ISS

EARTH OBSERVATION
Six Astrium satellites on the same flight

Arianespace's no. 2 Soyuz begins taking shape for launch from the Spaceport in French Guiana

Vega getting ready for exploitation

MSU satellite orbits the Earth after early morning launch

EARTH OBSERVATION
Three New Planets and a Mystery Object Discovered Outside Our Solar System

Dwarf planet sized up accurately as it blocks light of faint star

Herschel Finds Oceans of Water in Disk of Nearby Star

UH Astronomer Finds Planet in the Process of Forming

EARTH OBSERVATION
Tying atomic threads in knots may produce material benefits

GMV Awarded Contract For Paz Satellite Control Center

An Incredible Shrinking Material

Trillions served: Massive, complex projects for DOE JGI 2012 Community Sequencing Program




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement