Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
. 24/7 Space News .




CLIMATE SCIENCE
Monsoon failure key to long droughts in Southwest
by Staff Writers
Tucson AZ (SPX) Mar 13, 2013


In the American Southwest, precipitation during the summer monsoon season provides a significant portion of the annual precipitation. Here lightning strikes over southern Arizona's Tucson Mountains during a 2010 monsoon thunderstorm. Credit: Copyright Daniel Griffin, University of Arizona.

Long-term droughts in the Southwestern North America often mean failure of both summer and winter rains, according to new tree-ring research from a University of Arizona-led team. The finding contradicts the commonly held belief that a dry winter rainy season is generally followed by a wet monsoon season, and vice versa.

The new research shows that for the severe, multi-decadal droughts that occurred from 1539 to 2008, generally both winter and summer rains were sparse year after year.

"One of the big questions in drought studies is what prompts droughts to go on and on," said lead author Daniel Griffin, a doctoral candidate in the UA School of Geography and Development. "This gives us some indication that the monsoon and its failure is involved in drought persistence in the Southwest."

The new 470-year-long history of summer precipitation in the Southwest covers most of Arizona, western New Mexico and parts of northern Mexico. "This is the first time researchers have used tree rings to take a closer look at the monsoon in a large and important area of the American Southwest," said Griffin, who also is an EPA STAR Research Fellow at the UA Laboratory of Tree-Ring Research.

"Monsoon droughts of the past were more severe and persistent than any of the last 100 years," he said. "These major monsoon droughts coincided with decadal winter droughts."

Those droughts had major environmental and social effects, Griffin said, pointing out that the late-16th-century megadrought caused landscape-scale vegetation changes, a 17th-century drought has been implicated in the Pueblo Revolt of 1680 and the 1882-1905 drought killed more than 50 percent of Arizona's cattle.

Co-author Connie A. Woodhouse, UA associate head and associate professor of geography and development, said, "The thing that's interesting about these droughts is that we've reconstructed the winter precipitation, but we've never known what the summers were like."

Because winter precipitation has the strongest influence on annual tree growth, previous large-scale, long-term tree-ring reconstructions of the region's precipitation history had focused only on the winter rainy season. "Now we see - wow - the summers were dry, too," she said. "That has a big impact."

The team's research report, "North American monsoon precipitation reconstructed from tree-ring latewood," is scheduled for publication March 11 in Geophysical Research Letters, a journal of the American Geophysical Union.

Additional UA co-authors are David M. Meko, Holly L. Faulstich, Carlos Carrillo, Ramzi Touchan, Christopher L. Castro and Steven W. Leavitt. Co-author David W. Stahle is from the University of Arkansas in Fayetteville.

The National Science Foundation, the National Oceanic and Atmospheric Administration and the U.S. Environmental Protection Agency supported the research.

"In the Southwest, the winter precipitation is really important for water supply. This is the water that replenishes reservoirs and soil moisture," Woodhouse said. "But the monsoon mediates the demand for water in the summer."

Until recently, most tree-ring researchers, known as dendrochronologists, have looked at the total width of trees' annual rings to reconstruct past climate. Few teased out the seasonal climate signal recorded in the narrow part of the growth ring laid down in late summer known as latewood.

To figure out the region's past history of monsoon precipitation, the scientists needed to measure latewood from tree-ring samples stored in the archives of the UA Laboratory of Tree-Ring Research and go into the field to take additional samples of tree rings.

The team looked at annual growth rings from two different species, Douglas-fir (Pseudotsuga menziesii) and ponderosa pine (Pinus ponderosa) throughout the weather forecast region called North American Monsoon Region 2, or NAM2.

In all, the researchers used samples from 50 to 100 trees at each of 53 different sites throughout southwestern North America. The team's climate analyses focused on NAM2, which covers most of Arizona, western New Mexico and northern parts of the Mexican states of Sonora and Chihuahua.

Griffin said, "It was a massive undertaking -- we employed about 15 undergraduates over a four-year period to measure almost 1 million tree rings."

The results surprised him because rain gauge records for the Southwest from 1950-2000 show dry seasons alternated with wet ones.

However, the team's new multi-century record going back to 1539 shows that the wet/dry pattern of the latter part of the 20th century is not the norm - either prior to the 20th century or now, he said.

One possible next step, Woodhouse said, is to expand the current project to other areas of the Southwest and into Mexico, where the monsoon has a bigger influence on annual precipitation.

Another would be using tree-ring reconstructions of the Southwest's fire histories to see how wildfires are related to summer precipitation.

Griffin said, "Before I moved to the Southwest, I didn't realize how critically important the summer rains are to the ecosystems here. The summer monsoon rains have allowed humans to survive in the Southwest for at least 4,000 years."

.


Related Links
The Monsoon Project
Climate Science News - Modeling, Mitigation Adaptation






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





CLIMATE SCIENCE
Governments falling short in drought fight: UN
Geneva (AFP) March 07, 2013
Governments worldwide are failing to do enough to tackle drought, which lacks the headline-making punch of a hurricane but can have an equally devastating human and economic impact, the UN weather agency warned Thursday. "A flood or hurricane is over within hours or days. A drought can last weeks, months, a season, a year. But droughts can cause as many deaths over time as any other natural ... read more


CLIMATE SCIENCE
Lunar impacts created seas of molten rock

China to use modified rocket for moon landing mission

Water On The Moon: It's Been There All Along

Building a lunar base with 3D printing

CLIMATE SCIENCE
Maryland explores adaptations strategies for survival on Mars

NASA rover finds conditions once suited to life on Mars

Curiosity Rover's Recovery Moving Forward

NASA Rover Finds Conditions Once Suited for Ancient Life on Mars

CLIMATE SCIENCE
Technology to detect Alzheimer's takes SXSW prize

Basketball legend Shaq talks tech at SXSW

UK and Kazakhstan agree collaboration in space

Wyle To Provide NASA Ongoing Support For Human Space Flight

CLIMATE SCIENCE
China's fourth space launch center to be in use in two years

China to launch new manned spacecraft

Woman expected again to join next China crew roster

China's space station will be energy-efficient

CLIMATE SCIENCE
'Goody Bag' Filled With Sample Processing Supplies Arrives on Station

ESA's Columbus Biolab Facility

SpaceX set for third mission to space station

Record Number of Students Control ISS Camera

CLIMATE SCIENCE
Grasshopper Successfully Completes 80M Hover Slam

Musk: 'I'd like to die on Mars'

Ariane 5 vehicle for next ATV resupply mission in Kourou

Vega launcher integration continues for its April mission

CLIMATE SCIENCE
Astronomers Conduct First Remote Reconnaissance of Another Solar System

The Birth of a Giant Planet?

Scientists spot birth of giant planet

NASA's Kepler Mission Discovers Tiny Planet System

CLIMATE SCIENCE
Aspirin may lower melanoma risk

NIST quantum refrigerator offers extreme cooling and convenience

Researchers Solve Riddle of What Has Been Holding Two Unlikely Materials Together

Star-shaped waves spotted in shaken fluid




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