The finding is the first to document that the abrupt changes in Ice Age climate known from Greenland also occurred in the southwestern U.S., said co-author Julia E. Cole of the University of Arizona in Tucson.
"It's a new picture of the climate in the Southwest during the last Ice Age," said Cole, a UA professor of geosciences. "When it was cold in Greenland, it was wet here, and when it was warm in Greenland, it was dry here."
The researchers tapped into the natural climate archives recorded in a stalagmite from a limestone cave in southern Arizona. Stalagmites grow up from cave floors.
The stalagmite yielded an almost continuous, century-by-century climate record spanning 55,000 to 11,000 years ago. During that time ice sheets covered much of North America, and the Southwest was cooler and wetter than it is now.
Cole and her colleagues found the Southwest flip-flopped between wet and dry periods during the period studied.
Each climate regime lasted from a few hundred years to more than one thousand years, she said. In many cases, the transition from wet to dry or vice versa took less than 200 years.
"These changes are part of a global pattern of abrupt changes that were first documented in Greenland ice cores," she said. "No one had documented those changes in the Southwest before."Scientists suggest that changes in the northern Atlantic Ocean's circulation drove the changes in Greenland's Ice Age climate, Cole said. "Those changes resulted in atmospheric changes that pushed around the Southwest's climate."
"Also, changes in the storm track are the kinds of changes we expect to see in a warming world," she said. "When you warm the North Atlantic, you move the storm track north."
The team's paper, "Moisture Variability in the Southwestern U.S. Linked to Abrupt Glacial Climate Change," is scheduled for publication in the February issue of Nature Geoscience. Cole's UA co-authors are Jennifer D. M. Wagner, J. Warren Beck, P. Jonathan Patchett and Heidi R. Barnett. Co-author Gideon M. Henderson is from the University of Oxford, U.K.
Cole became interested in studying cave formations as natural climate archives about 10 years ago. At the suggestion of some local cave specialists, she and her students began working in the Cave of the Bells, an active limestone cave in the Santa Rita Mountains.
In such a cave, mineral-rich water percolates through the soil into the cave below and onto its floor. As the water loses carbon dioxide, the mineral known as calcium carbonate is left behind. As the calcium carbonate accumulates in the same spot on the cave floor over thousands of years, it forms a stalagmite.
The researchers chose the particular stalagmite for study because it was deep enough in the cave that the humidity was always high, an important condition for preservation of climate records, Cole said. Following established cave conservation protocols, the researchers removed the formation, which was less than 18 inches tall.
For laboratory analyses, first author Wagner took a core about one inch in diameter from the center of the stalagmite. The scientists then returned the formation to the cave, glued it back into its previous location with special epoxy and capped it with a limestone plug.
To read the climate record preserved in the stalagmite, Wagner sliced the core lengthwise several times for several different analyses.
On one slice, she shaved more than 1,200 hair-thin, 100-micron samples and measured what types of oxygen molecule each one contained.
A rare form of oxygen, oxygen-18, is more common in the calcium carbonate deposited during dry years. By seeing how much oxygen-18 was present in each layer, the scientists could reconstruct the region's pattern of wet and dry climate.
To assign dates to each wet and dry period, Wagner used another slice of the core for an analysis called uranium-thorium dating.
The radioactive element uranium is present in minute amounts in the water dripping onto a stalagmite. The uranium then becomes part of the formation. Uranium decays into the element thorium at a steady and known rate, so its decay rate can be used to construct a timeline of a stalagmite's growth.
By matching the stalagmite's growth timeline with the sequence of wet and dry periods revealed by the oxygen analyses, the researchers could tell in century-by-century detail when the Southwest was wet and when it was dry.
"This work shows the promise of caves to providing climate records for the Southwest. It's a new kind of climate record for this region," Cole said.
She and her colleagues are now expanding their efforts by sampling other cave formations in the region.
The National Science Foundation, the Geological Society of America and the University of Arizona's Faculty Small Grant program funded the research.Researcher contact:
Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union
UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences