Microfossils unravel climate history of tropical Africa, offer clues for future
Scientists from the Royal Netherlands Institute for Sea Research obtained for the first time a detailed temperature record for tropical central Africa over the past 25,000 years. They did this in cooperation with a German colleague from the University of Bremen. The scientists developed an entirely new method to reconstruct the history of land temperatures based on the molecular fossils of soil bacteria.
They applied the method to a marine sediment core taken in the outflow of the Congo River (picture, click to enlarge). This core contained eroded land material and microfossils from marine algae. The results show that the land environment of tropical Africa was cooled more than the adjacent Atlantic Ocean during the last ice-age. This large temperature difference between land and ocean surface resulted in drier conditions compared to the current situation, which favours the growth of a lush rainforest.
These findings provide further insight in natural variations in climate and the possible consequences of a warming earth on precipitation in central Africa. The results [*abstract] were published in this week's issue of Science.
One of the techniques currently used to estimate past sea surface temperatures, is based on organic molecules from algae growing in the surface layer of the Ocean. These organisms adapt the molecular composition of their cell membranes to ambient temperature to maintain constant physiological properties. When such molecules sink to the sea floor and are buried in sediments where oxygen does not penetrate, they can be preserved for thousands of years. The ratios between the different molecules from the algal cell membrane can be used to approximate the past temperature of the sea surface. These techniques are therefore called 'proxies'.
New method to measure soil temperatures
Reconstructing continental temperature history is more difficult than for the oceans, because soils on the continent do not form a continuous archive but are often eroded. The researchers developed an entirely new proxy for the annual mean air temperature on land, based on molecules from the cell membrane of soil inhabiting bacteria. They analysed eroded soil material in a sediment core in the outflow area of the river Congo in the South Atlantic Ocean at a depth of almost 1000m. Since the Congo River drains a large part of tropical central Africa, the land derived material gives an integrated signal for a very large area.
Cool tropical Africa
The new proxy was used in this sediment core to obtain both a continental and a sea surface temperature record. A comparison of both records shows that ocean surface and land temperatures behaved differently during the past 25,000 years:
biomass :: bioenergy :: biofuels :: energy :: sustainability :: climate change :: precipitation :: Congo :: Africa ::
During the last ice age, temperatures over tropical Africa were 21°C, about 4°C lower than today, whereas the tropical Atlantic Ocean was only about 2.5°C colder. By comparing this temperature difference with existing records of continental rainfall variability, lead author Johan Weijers and his colleagues concluded that the land-sea temperature difference has by far the largest influence on continental rainfall.
This can be explained by the strong relationship of air pressure to temperature. When the temperature of the sea surface is higher than that of the continent, stronger offshore winds reduce the flow of moist sea air onto the African continent. This occurred during the last ice age and, as a consequence, the land climate in tropical Africa was drier than it is in today's world, where it favours the growth of a lush rainforest. These results provide further insight into the natural variation of climate and the possible consequences of a warming earth on precipitation in central Africa.
This research project was funded by the division of Earth and Life Sciences of the Netherlands Organisation for Scientific Research (NWO-ALW).
Image: Overview of the drainage area of the river Congo in central Africa (area within the white outline) and the geographical postion of sediment core GeoB 6518, which was taken at a depth of 962m. A: Digitalelevation map (source: NASA Jet Propulsion Laboratory, California Inst. of Technol.); B: map with current annual mean air temperatures in Africa. Courtesy:
Royal Netherlands Institute for Sea Research.
More information:
Johan W. H. Weijers, Enno Schefuß, Stefan Schouten, Jaap S. Sinninghe Damsté, Coupled Thermal and Hydrological Evolution of Tropical Africa over the Last Deglaciation [*abstract], Science 23 March 2007: Vol. 315. no. 5819, pp. 1701 - 1704, DOI: 10.1126/science.1138131
Royal Netherlands Institute for Sea Research: Microfossils unravel Africa’s climate history - March 22, 2007.
Article continues
They applied the method to a marine sediment core taken in the outflow of the Congo River (picture, click to enlarge). This core contained eroded land material and microfossils from marine algae. The results show that the land environment of tropical Africa was cooled more than the adjacent Atlantic Ocean during the last ice-age. This large temperature difference between land and ocean surface resulted in drier conditions compared to the current situation, which favours the growth of a lush rainforest.
These findings provide further insight in natural variations in climate and the possible consequences of a warming earth on precipitation in central Africa. The results [*abstract] were published in this week's issue of Science.
One of the techniques currently used to estimate past sea surface temperatures, is based on organic molecules from algae growing in the surface layer of the Ocean. These organisms adapt the molecular composition of their cell membranes to ambient temperature to maintain constant physiological properties. When such molecules sink to the sea floor and are buried in sediments where oxygen does not penetrate, they can be preserved for thousands of years. The ratios between the different molecules from the algal cell membrane can be used to approximate the past temperature of the sea surface. These techniques are therefore called 'proxies'.
New method to measure soil temperatures
Reconstructing continental temperature history is more difficult than for the oceans, because soils on the continent do not form a continuous archive but are often eroded. The researchers developed an entirely new proxy for the annual mean air temperature on land, based on molecules from the cell membrane of soil inhabiting bacteria. They analysed eroded soil material in a sediment core in the outflow area of the river Congo in the South Atlantic Ocean at a depth of almost 1000m. Since the Congo River drains a large part of tropical central Africa, the land derived material gives an integrated signal for a very large area.
Cool tropical Africa
The new proxy was used in this sediment core to obtain both a continental and a sea surface temperature record. A comparison of both records shows that ocean surface and land temperatures behaved differently during the past 25,000 years:
biomass :: bioenergy :: biofuels :: energy :: sustainability :: climate change :: precipitation :: Congo :: Africa ::
During the last ice age, temperatures over tropical Africa were 21°C, about 4°C lower than today, whereas the tropical Atlantic Ocean was only about 2.5°C colder. By comparing this temperature difference with existing records of continental rainfall variability, lead author Johan Weijers and his colleagues concluded that the land-sea temperature difference has by far the largest influence on continental rainfall.
This can be explained by the strong relationship of air pressure to temperature. When the temperature of the sea surface is higher than that of the continent, stronger offshore winds reduce the flow of moist sea air onto the African continent. This occurred during the last ice age and, as a consequence, the land climate in tropical Africa was drier than it is in today's world, where it favours the growth of a lush rainforest. These results provide further insight into the natural variation of climate and the possible consequences of a warming earth on precipitation in central Africa.
This research project was funded by the division of Earth and Life Sciences of the Netherlands Organisation for Scientific Research (NWO-ALW).
Image: Overview of the drainage area of the river Congo in central Africa (area within the white outline) and the geographical postion of sediment core GeoB 6518, which was taken at a depth of 962m. A: Digitalelevation map (source: NASA Jet Propulsion Laboratory, California Inst. of Technol.); B: map with current annual mean air temperatures in Africa. Courtesy:
Royal Netherlands Institute for Sea Research.
More information:
Johan W. H. Weijers, Enno Schefuß, Stefan Schouten, Jaap S. Sinninghe Damsté, Coupled Thermal and Hydrological Evolution of Tropical Africa over the Last Deglaciation [*abstract], Science 23 March 2007: Vol. 315. no. 5819, pp. 1701 - 1704, DOI: 10.1126/science.1138131
Royal Netherlands Institute for Sea Research: Microfossils unravel Africa’s climate history - March 22, 2007.
Article continues
Monday, March 26, 2007
Scientists develop biodegradable fuel cell that runs on sugar and has higher energy density than lithium ion batteries
For consumers, the 'biobattery' could mean significantly longer time to talk and play music on their iPods, cell phones and laptops. For the world's farmers, this means the carbohydrate economy gets another boost. Our post-petroleum economy is becoming an ever sweeter one...
Like other biofuel cells, the sugar battery contains enzymes that convert fuel - in this case, sugar - into electricity, leaving behind water as a main byproduct. But unlike other fuel cells, all of the materials used to build the sugar battery are biodegradable. This gives it a huge advantage over the millions of common batteries used in electronics, which are becoming a big waste problem.
The new battery could eventually replace lithium ion batteries in many portable electronic applications, including computers, the scientists say. Their findings were described today at the 233rd national meeting of the American Chemical Society in Chicago.
"This study shows that renewable fuels can be directly employed in batteries at room temperature to lead to more energy-efficient battery technology than metal-based approaches," said study leader Shelley Minteer, Ph.D., an electrochemist at Saint Louis University (picture). "It demonstrates that by bridging biology and chemistry, we can build a better battery that's also cleaner for the environment."
Using sugar for fuel is not a new concept: sugar in the form of glucose supplies the energy needs of all living things. While nature has figured out how to harness this energy efficiently, scientists only recently have learned how to unleash the energy-dense power of sugar to produce electricity, Minteer said.
A few other researchers also have developed fuel cell batteries that run on sugar, but Minteer claims that her version is the longest-lasting and most powerful of its type to date. As proof of concept, she has used a small prototype of the battery (about the size of a postage stamp) to successfully run a handheld calculator. If the battery continues to show promise during further testing and refinement, it could be ready for commercialization in three to five years, she estimates:
biomass :: bioenergy :: biofuels :: energy :: sustainability :: sugar :: biofuel cell :: biodegradable :: batteries :: lithium ion :: carbohydrate economy :: bioeconomy ::
Consumers aren't the only ones who stand to benefit from this new technology. The military is interested in using the sugar battery to charge portable electronic equipment on the battlefield and in emergency situations where access to electricity is limited. These devices include remote sensors for detecting biological and chemical weapons. Devices could be instantly recharged by adding virtually any convenient sugar source, including plant sap, Minteer said.
So far, Minteer has run the batteries on glucose, flat sodas, sweetened drink mixes and tree sap, with promising results. She also tested carbonated beverages, but carbonation appears to weaken the fuel cell. The best fuel source tested so far is ordinary table sugar (sucrose) dissolved in water, she said.
One of the first applications Minteer envisions for the sugar fuel cell is using it as a portable cell phone recharger, similar to the quick rechargers already on the market that allow users to instantly charge their cell phones while 'on the go.' Ideally, these rechargers would contain special cartridges that are pre-filled with a sugar solution.
These cartridges then could be replaced when they're used up. Ultimately, she hopes that the sugar battery can be used as a stand-alone battery replacement in a wide range of portable electronic devices.
Future work includes modifying the battery's performance for varying environmental conditions, including high temperatures, and extending the life of the battery, Minteer said. Funding for this study was provided by the U.S. Department of Defense.
A chemistry professor at Saint Louis University, Minteer already has invented a biobattery than can run on alcohol and natural enzymes. She formed a start-up company with a former graduate student to develop commercial applications for the invention. The company has secured millions of dollars in venture capital and other investments.
The Saint Louis University scientist says her long-term goal is to create a rechargeable battery that not only lasts longer, but also is also friendly to the environment.
For her groundbreaking research, Minteer earned the 2005 Innovation Award from the Academy of Science of St. Louis. From freshmen to graduate assistants, Saint Louis University students at all levels work in her lab.
Article continues
posted by Biopact team at 6:12 PM 1 comments links to this post