Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Global sea level rise dampened by Australia floods

20.08.2013
When enough raindrops fall over land instead of the ocean, they begin to add up.

New research shows that in 2010 and 2011, enough water collected in Australia to temporarily halt a long-term trend of global sea level rise. When three atmospheric patterns came together over the Indian and Pacific oceans in 2010-11, they drove so much precipitation over Australia that the world’s ocean levels dropped measurably. Unlike other continents, the soils and topography of Australia prevent almost all of its precipitation from running off into the ocean.

Now that the atmospheric patterns have snapped back and more rain is falling over tropical oceans, the seas are rising again. In fact, with Australia in a major drought, they are rising faster than before.

“It’s a beautiful illustration of how complicated our climate system is,” says John Fasullo, the lead author of the study. “The smallest continent in the world can affect sea level worldwide. Its influence is so strong that it can temporarily overcome the background trend of rising sea levels that we see with climate change.”

The study led by the National Center for Atmospheric Research (NCAR), with co-authors from NASA’s Jet Propulsion Laboratory and the University of Colorado at Boulder, will be published next month in Geophysical Research Letters.

-----Consistent rising, interrupted-----

As the climate warms, the world’s oceans rose in recent decades by just more than 3 millimeters (0.1 inches) annually. This is partly because the heat causes water to expand, and partly because runoff from retreating glaciers and ice sheets is making its way into the oceans.

But for an 18-month period beginning in 2010, the oceans mysteriously dropped by about 7 millimeters (about 0.3 inches), more than offsetting the annual rise.

Fasullo and his co-authors published research last year demonstrating that the reason had to do with the increased rainfall over tropical continents. They also showed that the drop coincided with the atmospheric oscillation known as La Niña, which cooled tropical surface waters in the eastern Pacific and suppressed rainfall there while enhancing it over portions of the tropical Pacific, Africa, South America, and Australia.

But an analysis of the historical record showed that past La Niña events only rarely accompanied such a pronounced drop in sea level.

Using a combination of satellite instruments and other tools, the new study finds that the picture in 2010–11 was uniquely complex. A rare combination of two other semi-cyclic climate modes came together to drive such large amounts of rain over Australia that the continent, on average, received almost 300 millimeters (1 foot) of rain more than normal.

The initial effects of La Niña were to cool surface waters in the eastern Pacific Ocean and push moisture to the west. A climate pattern known as the Southern Annular Mode then coaxed the moisture into Australia’s interior, causing widespread flooding across the continent. Later in the event, high levels of moisture from the Indian Ocean driven by the Indian Ocean Dipole collided with La Niña-borne moisture in the Pacific and pushed even more moisture into the continent’s interior. Together, these influences spurred one of the wettest periods in Australia’s recorded history.

Australia’s vast interior, called the Outback, is ringed by coastal mountains and often quite dry. Because of the low-lying nature of the continent’s eastern interior and the lack of river runoff in its western dry environment, most of the heavy rainfall of 2010–11 remained inland rather than flowing into the oceans. While some of it evaporated in the desert sun, much of it sank into the dry, granular soil of the Western Plateau or filled the Lake Eyre basin in the east.

“No other continent has this combination of atmospheric set-up and topography,” Fasullo says. “Only in Australia could the atmosphere carry such heavy tropical rains to such a large area, only to have those rains fail to make their way to the ocean.”

-----Measuring the difference-----

To conduct the research, the scientists turned to three cutting-edge observing instrument systems:
NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites, which make detailed measurements of Earth’s gravity field. The satellites enable scientists to monitor changes in the mass of continents.
The Argo global array of 3,000 free-drifting floats that measure the temperature and salinity of the upper 6,000 feet of the world’s oceans.

Satellite-based altimeters that are continuously calibrated against a network of tide gauges. Scientists subtract seasonal and other variations to closely estimate global sea level changes.

Using these instruments, the researchers found that the mass in Australia and, to a lesser extent, South America began to increase in 2010 as the continents experienced heavy and persistent rain. At the same time, sea levels began to measurably drop.

Since 2011, when the atmospheric patterns shifted out of their unusual combination, sea levels have been rising at a faster pace of about 10 millimeters (0.4 inches) per year.

Scientists are uncertain how often the three atmospheric events come together to cause such heavy rains over Australia. Fasullo believes there may have been a similar event in 1973-74, which was another time of record flooding in that continent. But modern observing instruments did not exist then, making it impossible to determine what took place in the atmosphere and whether it affected sea level rise.

“Luckily we’ve got great observations now,” Fasullo says. “We need to maintain these observing platforms to understand what is a complicated climate system.”

The study was funded by the National Science Foundation, which is NCAR’s sponsor, and by NASA.

The work was published today in Geophysical Research Letters, a journal of the American Geophysical Union.

Notes for Journalists: Journalists can download a PDF copy of this accepted article by clicking on this link:

http://onlinelibrary.wiley.com/doi/10.1002/grl.50834/abstract

Neither the paper nor this press release is under embargo.

Title:
“Australia's unique influence on global sea level in 2010–2011”
Authors:
John T. Fasullo: National Center for Atmospheric Research, Boulder, CO;
Carmen Boening and Felix W. Landerer: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA;

R. Steven Nerem: Colorado Center for Astrodynamics Research, University of Colorado at Boulder, Boulder, CO.

Contact information for the authors:
John Fasullo, Telephone: +1 (303) 497-1712, Email: fasullo@ucar.edu
Contacts:
AGU Contact:
Mary Catherine Adams
+1 (202) 777-7530
mcadams@agu.org

National Center for Atmospheric Research (NCAR) Contacts:
Bob Henson, NCAR/UCAR Media Relations
+1 (303) 497-8605
bhenson@ucar.edu

David Hosansky, NCAR/UCAR Media Relations
+1 (303) 497-8611
hosansky@ucar.edu

Mary Catherine Adams | American Geophysical Union
Further information:
http://www.agu.org
http://www.agu.org/news/press/pr_archives/2013/2013-41.shtml

More articles from Earth Sciences:

nachricht NASA examines newly formed Tropical Depression 3W in 3-D
26.04.2017 | NASA/Goddard Space Flight Center

nachricht Early organic carbon got deep burial in mantle
25.04.2017 | Rice University

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Scientist invents way to trigger artificial photosynthesis to clean air

26.04.2017 | Materials Sciences

Ammonium nitrogen input increases the synthesis of anticarcinogenic compounds in broccoli

26.04.2017 | Agricultural and Forestry Science

SwRI-led team discovers lull in Mars' giant impact history

26.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>