Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Tropical rainfall patterns varied through time

05.02.2013
Research provides deeper understanding of drought cycles in Central America

Historic lake sediment dug up by University of Pittsburgh researchers reveals that oceanic influences on rainfall in Central America have varied over the last 2,000 years, highlighting the fluctuating influence the Atlantic and Pacific Oceans have on precipitation.

The Pitt study, published in the February print edition of the peer-reviewed journal Geology, shows that factors currently producing drier climates in Central America actually resulted in wetter conditions a few hundred years ago, providing a deeper understanding of drought cycles in that region of the Western Hemisphere.

The researchers analyzed lake sediment that had accumulated for 1,400 years in Lago El Gancho in Nicaragua to reconstruct climate patterns in the Central American country during the Medieval Climate Anomaly—a warm period roughly spanning the years 950 to 1250—and a 500-year, global cold spell known as the Little Ice Age that began around 1350.

Because of the extreme disparity in climatic conditions they represent, these two time periods contain clues for scientists looking to better understand climate change, said lead study author Nathan Stansell, who conducted the research as a graduate student in Pitt's Sedimentology and Sediment Geochemistry Labs led by Mark Abbott, Pitt associate professor of geology. Stansell earned his master's and PhD degrees in geology and planetary science from Pitt's Kenneth P. Dietrich School of Arts and Sciences in 2005 and 2009, respectively.

"We have a decent understanding of how those systems affect today's Central American climate, but we wanted to know if those systems operated in similar ways in the past," said Stansell, now a research fellow at The Ohio State University. "We found that the long-term trends we inferred from the data are not entirely consistent with our modern-day observations."

Sandwiched between the Atlantic and Pacific oceans, Lago El Gancho, which is near the city of Granada, became the research team's choice for examining the variability and influence of the North Atlantic Oscillation—a phenomenon that is the dominant mode of climate variability in the North Atlantic region. The researchers also examined the El Niño/La Niña Southern Oscillation pattern—a quasi-periodic climate pattern occurring every three to seven years or so in the Pacific Ocean.

Using layered mud found in the sediment cores collected in 2004, the team reconstructed past climatic conditions using the radiocarbon ages of charcoal to date the layers. They examined the calcium-carbonate shells of the ostracod crustaceans, small organisms living in lakes, to measure the oxygen isotope ratios commonly studied to identify wet and dry climate cycles.

The sediments revealed a dramatic change in climatic conditions brought on by the North Atlantic Oscillation. In our modern age, when the North Atlantic is in its "positive" phase, atmospheric pressure anomalies prevent colder Arctic air from plunging south into the lower latitudes of North America, leading to drier conditions in Nicaragua, while negative phases lead to wetter climates.

However, the Pitt team found that during the positive-phase Medieval Climate Anomaly, wetter conditions prevailed alongside the North Atlantic and La Niña patterns. Then, 150 years later, the Little Ice Age chilled the region off, holding a negative North Atlantic phase, and an abrupt shift toward persistently drier conditions occurred. The impact of the El Niño/La Niña Southern Oscillation pattern did not change between the two periods.

How or why did this happen? "There are any number of possible scenarios," Stansell says. "Most likely, the Northern Hemisphere temperatures affected the atmospheric pressure across the North Atlantic while in a positive phase. When the Oscillation became negative, it would have pushed precipitation to the south, leaving it drier in Nicaragua.

"The main idea here is that the ability of the Atlantic Ocean to exert its influence on precipitation patterns in Central America varied in the past," Stansell adds.

Climatic Future

Scientists are currently working towards a better understanding of how precipitation patterns will change under a range of different scenarios.

Modern-day observations show drier conditions during positive whirls. However, Stansell's geologic record of the Medieval Climate Anomaly and Little Ice Age shows the opposite. Therefore, he said, the use of a geologic record to determine current conditions needs to be considered carefully.

"What this tells us is that more studies like ours need to be done in order to better predict how the tropical hydrologic cycle will operate in the future," said Stansell. "Our specific work in the tropics is to better develop that longer-term perspective of how the North Atlantic pressure anomalies play a key role in this region's water-resource availability."

Stansell stresses the importance of combining geologic evidence with modeling scenarios to reconstruct patterns of the past to more accurately discern a climatic future.

"If we can't accurately reconstruct past conditions in our modeling scenarios, then we can't rely on those models to predict future changes," Stansell said.

In addition to Stansell and Abbott, the research team for this study included Pitt alumni Michael Rubinov (A&S '06), Manuel Roman-Lacayo (A&S '06), and Byron A. Steinman (A&S '11G).

The paper, "Lacustrine stable isotope record of precipitation changes in Nicaragua during the Little Ice Age and Medieval Climate Anomaly," was published online by Geology on Nov. 13 in addition to being published in the journal's February 2013 print edition. The work was supported by grants from the Geological Society of America and the University of Pittsburgh Center for Latin American Studies.

B. Rose Huber | EurekAlert!
Further information:
http://www.pitt.edu

More articles from Earth Sciences:

nachricht GPM sees deadly tornadic storms moving through US Southeast
01.12.2016 | NASA/Goddard Space Flight Center

nachricht Cyclic change within magma reservoirs significantly affects the explosivity of volcanic eruptions
30.11.2016 | Johannes Gutenberg-Universität Mainz

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>