Earth Science News  





. Monsoon intensity driven by Earth's orbit: study

by Staff Writers
Paris (AFP) Feb 27, 2008
The monsoon rains that drench tropical and subtropical Asia from June through September vary in duration and intensity in keeping with tiny wobbles in Earth's orbit as it circles the Sun, according to a study released Wednesday.

These cycles wax and wane every 23,000 years, said the study, based on the breakthrough use of stalagmites from a cave in central-eastern China to measure changes in climate patterns over the last quarter million years.

"The implications are that the present Asian summer monsoon is relatively weak in comparison to a few thousand years ago and that is will stay at this level for centuries more," lead researcher Hai Cheng of Nanjing Normal University in China's Jiangsu Province told AFP.

The findings, however, do not take into account the relatively recent impact of greenhouse gas-driven global warming, which climate scientists predict could significant alter monsoon patterns.

Three irregularities in the movement of Earth -- its orbit, the angle at which it is tilted, and the axis of rotation -- all combine to create a periodic variation in the amount of incoming solar radiation, explained Cheng.

It is this so-called precessional cycle that is largely responsible for longterm changes in monsoon duration and strength, the researchers found.

Monsoons occur with the seasonal reversals of wind directions caused by temperature differences between the land and sea.

While found elsewhere in the world, they are most pronounced in Asia in part due to the impact of the massive Tibetan Plateau.

Economies in tropical and sub-tropical Asia, especially around the Indian subcontinent, depend on monsoon rainfall to grow crops on land that is largely unirrigated.

But heavy monsoons can also bring massive flooding, causing severe economic damage and loss of life.

As significant as the findings, arguably, are the methods used to collect them.

Cheng and his colleagues measured the oxygen isotope ratios locked in the stalagmites built up from the floor of the Sanbao Cave to determine changes in climate over millennia, said the study, published in the British journal Nature.

Compared with other commonly used proxies of paleoclimatology such as tree-rings and ice cores, speleothems -- as these mineral deposits are called -- provide a record over a much longer timescale.

This technique "will likely replace the Greenland ice records as the chronological benchmark for correlating and calibrating climate variability," said Cheng.

It also allows for a new level of precision, achieved by measuring the growth of the isotope thorium-230 from the slow radioactive decay of uranium, found in trace amounts in the deposits.

"What emerges is a record of monsoon variation unprecedented in its detail and chronology stretching back 224,000 years," said Jonathan Overpeck and Julia Cole, both geologists at the University of Arizona, in a commentary, also in Nature.

The word "monsoon" is thought to have originated from the Arabic word "mausim," which means season.

Community
Email This Article
Comment On This Article

Related Links
Climate Science News - Modeling, Mitigation Adaptation




Tempur-Pedic Mattress Comparison

Newsletters :: SpaceDaily Express :: SpaceWar Express :: TerraDaily Express :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News
Voyage To Southern Ocean Aims To Study Air-Sea Fluxes Of Greenhouse Gases
New York NY (SPX) Feb 27, 2008
Scientists will embark this week from Punta Arenas, Chile, on the tip of South America, to spend 42 days amid the high winds and waves of the Southern Ocean. Here they hope to make groundbreaking measurements to explain how huge fluxes of climate-affecting gases move between atmosphere and sea, and vice-versa.

.
Get Our Free Newsletters Via Email
  



  • Indonesian city braces for disaster with little more than hope
  • Death toll from China snow storms hits 129: report
  • Kenya, UN warn crisis risks incubating new AIDS infections
  • Philippine floods and landslides toll rises to 26: officials

  • Monsoon intensity driven by Earth's orbit: study
  • Why Juniper Trees Can Live On Less Water
  • Wind variations may spur climate change
  • Voyage To Southern Ocean Aims To Study Air-Sea Fluxes Of Greenhouse Gases

  • Falcon Investigates Pollution From The Dakar Metropolis Into Desert Dust Layers
  • NASA Extends Mission For Ball Aerospace-Built ICESat
  • CIRA Scientist Among Authors Of Book Celebrating 50 Years Of Earth Observations From Space
  • Indonesia To Develop New EO Satellite

  • Exxon Valdez: oil company tells top court captain was to blame
  • Sofitel Hotels Become First Wind Powered Hotel Chain In The US
  • Analysis: Cuban oil production down
  • ADA-ES Plans To Provide Activated Carbon To The Power Industry

  • WHO plays down bird flu threat in China after three human deaths
  • Death of woman confirmed bird flu related: China health ministry
  • Yellow fever outbreak reported in Paraguay
  • Woman dies in southern China, tested positive for bird flu

  • Invasion Of The Cane Toads
  • MBL Creates Portal for Online Macroscope To Explore Life's Mysteries
  • Life May Have Begun In The Hot Or The Cold
  • Two Oxygenation Events In Ancient Oceans Sparked Spread Of Complex Life

  • Creation Of A New Material Capable Of Eliminating Pollutants Generated By The Hydrocarbon Industry
  • US DoE And Foundation Capital Partner To Commercialize Groundbreaking New Clean Energy Technologies
  • US DoE Funds Four Projects Developing Cost-Effective Enzymes For Advanced Biofuels
  • China's listed firms forced to submit environmental data: report

  • Delving Into The Deepest Recesses Of Human Brain
  • Military Matters: Shooting up schools
  • From Delicious To Death: Understanding Taste
  • Large Portion Of Brain Switches Off And Lets Creativity Flow In Jazz Improvisations

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2007 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. 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 SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement