Mesquite trees and woody shrubs are better adapted than grasslands to a Southwestern climate predicted to shift toward higher temperatures and greater variability in rainfall, UA ecologists have discovered.
As the desert Southwest becomes hotter and drier, semi-arid grasslands are slowly being replaced by a landscape dominated by mesquite trees, such as Prosopis velutina, and other woody shrubs, a team of University of Arizona researchers has found.
In a “leaf-to-landscape” approach, the team combined physiological experiments on individual plants and measurements across entire ecosystems to quantify how well grasslands, compared to mesquite trees and woody shrubs, cope with heat and water stress across seasonal precipitation periods. (more…)
How do we understand what’s happening today by looking back millions of years?
Scientists are looking at what climate conditions were like 3.3 to 3 million years ago, during a geologic period known as the Pliocene, and they are confident in the accuracy of their data.
The Pliocene is the most recent period of sustained global warmth similar to what is projected for the 21st century. Climate during this time period offers one of the closest analogs to estimate future climate conditions. (more…)
Researchers led by Matt Sullivan at the UA are among the first to dive into the world of viruses drifting through the world’s oceans.
Surrounded by the deep blue of the Pacific Ocean stretching from horizon to horizon, a lonely dot is glinting in the sun. It is the aluminum hull of a sailboat, a 118-foot schooner with white sails billowing from two masts.
On the deck, crewmembers and scientists are milling about. Commands are flying back and forth, and soon a strange contraption consisting of tubes clustered around an array of sensors dangling from a crane is lowered into the water, until it disappears in the clear blue depths. (more…)
Nearly one-third of CO2 emissions due to human activities enters the world’s oceans. By reacting with seawater, CO2 increases the water’s acidity, which may significantly reduce the calcification rate of such marine organisms as corals and mollusks, resulting in the potential loss of ecosystems. The extent to which human activities have raised the surface level of acidity, however, has been difficult to detect on regional scales because it varies naturally from one season and one year to the next, and between regions, and direct observations go back only 30 years.
By combining computer modeling with observations, an international team of scientists concluded that anthropogenic CO2 emissions, resulting from the influence of human beings, over the last 100 to 200 years have already raised ocean acidity far beyond the range of natural variations. The study is published in the January 22, 2012 online issue of Nature Climate Change. (more…)
*Disruption of wind shear enables stronger storms*
Pollution is making Arabian Sea cyclones more intense, according to a study in this week’s issue of the journal Nature.
Traditionally, prevailing wind shear patterns prohibit cyclones in the Arabian Sea from becoming major storms.
The Nature paper suggests that weakening winds have enabled the formation of stronger cyclones in recent years–including storms in 2007 and 2010 that were the first recorded storms to enter the Gulf of Oman. (more…)
*Evidence of water mass moving south 70 million years ago shows how warmth was distributed*
COLUMBIA, Mo. – New research from the University of Missouri indicates that Atlantic Ocean temperatures during the greenhouse climate of the Late Cretaceous Epoch were influenced by circulation in the deep ocean. These changes in circulation patterns 70 million years ago could help scientists understand the consequences of modern increases in greenhouse gases.
“We are examining ocean conditions from several past greenhouse climate intervals so that we can understand better the interactions among the atmosphere, the oceans, the biosphere, and climate,” said Kenneth MacLeod, professor of geological sciences in the College of Arts and Science. “The Late Cretaceous Epoch is a textbook example of a greenhouse climate on earth, and we have evidence that a northern water mass expanded southwards while the climate was cooling. At the same time, a warm, salty water mass that had been present throughout the greenhouse interval disappeared from the tropical Atlantic.” (more…)
Woods Hole Oceanographic Institution (WHOI) scientists have discovered that bacterial communication could have a significant impact on the planet’s climate.
In the ocean, bacteria coalesce on tiny particles of carbon-rich detritus sinking through the depths. WHOI marine biogeochemists Laura Hmelo, Benjamin Van Mooy, and Tracy Mincer found that these bacteria send out chemical signals to discern if other bacteria are in the neighborhood. If enough of their cohorts are nearby, then bacteria en masse commence secreting enzymes that break up the carbon-containing molecules within the particles into more digestible bits. It has been suggested that coordinated expression of enzymes is very advantageous for bacteria on sinking particles, and Hmelo and her colleagues have uncovered the first proof of this in the ocean. (more…)
