Forum für Wissenschaft, Industrie und Wirtschaft

Hauptsponsoren:     3M 
Datenbankrecherche:

 

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 Researchers discover dust plays prominent role in nutrients of mountain forest ecoystems
29.03.2017 | University of Wyoming

nachricht More than 100 years of flooding and erosion in 1 event
28.03.2017 | Geological Society of America

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Quantenkommunikation: Wie man das Rauschen überlistet

Wie kann man Quanteninformation zuverlässig übertragen, wenn man in der Verbindungsleitung mit störendem Rauschen zu kämpfen hat? Uni Innsbruck und TU Wien präsentieren neue Lösungen.

Wir kommunizieren heute mit Hilfe von Funksignalen, wir schicken elektrische Impulse durch lange Leitungen – doch das könnte sich bald ändern. Derzeit wird...

Im Focus: Entwicklung miniaturisierter Lichtmikroskope - „ChipScope“ will ins Innere lebender Zellen blicken

Das Institut für Halbleitertechnik und das Institut für Physikalische und Theoretische Chemie, beide Mitglieder des Laboratory for Emerging Nanometrology (LENA), der Technischen Universität Braunschweig, sind Partner des kürzlich gestarteten EU-Forschungsprojektes ChipScope. Ziel ist es, ein neues, extrem kleines Lichtmikroskop zu entwickeln. Damit soll das Innere lebender Zellen in Echtzeit beobachtet werden können. Sieben Institute in fünf europäischen Ländern beteiligen sich über die nächsten vier Jahre an diesem technologisch anspruchsvollen Projekt.

Die zukünftigen Einsatzmöglichkeiten des neu zu entwickelnden und nur wenige Millimeter großen Mikroskops sind äußerst vielfältig. Die Projektpartner haben...

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Das anwachsende Ende der Ordnung

Physiker aus Konstanz weisen sogenannte Mermin-Wagner-Fluktuationen experimentell nach

Ein Kristall besteht aus perfekt angeordneten Teilchen, aus einer lückenlos symmetrischen Atomstruktur – dies besagt die klassische Definition aus der Physik....

Im Focus: Wegweisende Erkenntnisse für die Biomedizin: NAD⁺ hilft bei Reparatur geschädigter Erbinformationen

Eine internationale Forschergruppe mit dem Bayreuther Biochemiker Prof. Dr. Clemens Steegborn präsentiert in 'Science' neue, für die Biomedizin wegweisende Forschungsergebnisse zur Rolle des Moleküls NAD⁺ bei der Korrektur von Schäden am Erbgut.

Die Zellen von Menschen und Tieren können Schäden an der DNA, dem Träger der Erbinformation, bis zu einem gewissen Umfang selbst reparieren. Diese Fähigkeit...

Alle Focus-News des Innovations-reports >>>

Anzeige

Anzeige

IHR
JOB & KARRIERE
SERVICE
im innovations-report
in Kooperation mit academics
Veranstaltungen

Industriearbeitskreis »Prozesskontrolle in der Lasermaterialbearbeitung ICPC« lädt nach Aachen ein

28.03.2017 | Veranstaltungen

Neue Methoden für zuverlässige Mikroelektronik: Internationale Experten treffen sich in Halle

28.03.2017 | Veranstaltungen

Wie Menschen wachsen

27.03.2017 | Veranstaltungen

 
VideoLinks
B2B-VideoLinks
Weitere VideoLinks >>>
Aktuelle Beiträge

Entzündung weckt Schläfer

29.03.2017 | Biowissenschaften Chemie

Mittelstand 4.0-Kompetenz­zentrum Stuttgart gestartet

29.03.2017 | Wirtschaft Finanzen

Energieträger: Biogene Reststoffe effizienter nutzen

29.03.2017 | Ökologie Umwelt- Naturschutz