Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Brown-led research team proposes new link to tropical African climate

15.09.2008
The Lake Tanganyika area, in southeast Africa, is home to nearly 130 million people living in four countries that bound the lake, the second deepest on Earth.

Scientists have known that the region experiences dramatic wet and dry spells, and that rainfall profoundly affects the area's people, who depend on it for agriculture, drinking water and hydroelectric power.

Scientists thought they knew what caused those rains: a season-following belt of clouds along the equator known as the Intertropical Convergence Zone (ITCZ). Specifically, they believed the ITCZ and rainfall and temperature patterns in the Lake Tanganyika area marched more or less in lockstep.

When the ITCZ moved north of the equator during the northern summer, the heat (and moisture) would follow, depriving southeast Africa of moisture and rainfall. When the ITCZ moved south of the equator during the northern winter, the moisture followed, and southeast Africa got rain.

Now a Brown-led research team has discovered the ITCZ may not be the key to southeast Africa's climate after all. Examining data from core sediments taken from Lake Tanganyika covering the last 60,000 years, the researchers report in this week's Science Express that the region's climate instead appears to be linked with ocean and atmospheric patterns in the Northern Hemisphere. The finding underscores the interconnectedness of the Earth's climate — how weather in one part of the planet can affect local conditions half a world away.

The discovery also could help scientists understand how tropical Africa will respond to global warming, said Jessica Tierney, a graduate student in Brown's Geological Sciences Department and the paper's lead author.

"It just implies the sensitivity of rainfall in eastern Africa is really high," Tierney said. "It doesn't really take much to tip it."

The researchers, including James Russell and Yongsong Huang of Brown's Department of Geological Sciences faculty and scientists at the University of Arizona and the Royal Netherlands Institute for Sea Research, identified several time periods in which rainfall and temperature in southeast Africa did not correspond with the ITCZ's location. One such period was the early Holocene, extending roughly from 11,000 years ago to 6,000 years ago, in which the ITCZ's location north of the equator would have meant that tropical Africa would have been relatively dry. Instead, the team's core samples showed the region had been wet.

Two other notable periods — about 34,000 years ago and about 58,000 years ago — showed similar discrepancies, the scientists reported.

In addition, the team found climatic changes that occurred during stadials (cold snaps that occur during glacial periods), such as during the Younger Dryas, suddenly swung rainfall patterns in southeast Africa. Some of those swings occurred in less than 300 years, the team reported.

"That's really fast," Tierney noted, adding it shows precipitation in the region is "jumpy" and could react abruptly to changes wrought by global warming.

While the scientists concluded the ITCZ is not the dominant player in shaping tropical African climate, they say more research is needed to determine what drives rainfall and temperature patterns there. They suspect that a combination of winter winds in northern Asia and sea surface temperatures in the Indian Ocean have something to do with it. Under this scenario, the winds emanating from Asia would pick up moisture from the Indian Ocean as they swept southward toward tropical Africa. The warmer the waters the winds passed over, the more moisture would be gathered, and thus, more rain would fall in southeast Africa. The theory would help explain the dry conditions in southeast Africa during the stadials, Tierney and Russell said, because Indian Ocean surface temperatures would be cooler, and less moisture would be picked up by the prevailing winds.

"What happens in southeast Africa appears to be really sensitive to the Indian Ocean's climate," Russell said.

The team examined past temperature in the region using a proxy called TEX86, developed by the Dutch contributing authors. To measure past precipitation, the researchers examined fatty acid compounds contained in plant leaf waxes stored in lakebed sediments — a relatively new proxy but considered by scientists to be a reliable gauge of charting past rainfall.

Richard Lewis | EurekAlert!
Further information:
http://www.brown.edu

More articles from Ecology, The Environment and Conservation:

nachricht Value from wastewater
16.08.2017 | Hochschule Landshut

nachricht Species Richness – a false friend? Scientists want to improve biodiversity assessments
01.08.2017 | Carl von Ossietzky-Universität Oldenburg

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>