Researchers link ocean organisms with increased cloud cover and potential climate changeNovember 08, 2006The biology connection Atmospheric scientists have reported a new and potentially important mechanism by which chemical emissions from ocean phytoplankton may influence the formation of clouds that reflect sunlight away from our planet. Discovery of the new link between clouds and the biosphere grew out of efforts to explain increased cloud cover observed over an area of the Southern Ocean where a large bloom of phytoplankton was occurring. Based on satellite data, the researchers hypothesized that airborne particles produced by oxidation of the chemical isoprene - which is emitted by the phytoplankton - may have contributed to a doubling of cloud droplet concentrations seen over a large area of ocean off the eastern coast of South America. Using complex numerical models, they estimated that the resulting increase in cloudiness reduced the absorption of sunlight by an amount comparable to what has been measured in highly polluted areas of the globe. If confirmed by field studies, this connection between clouds and biological activity could add a critical new component to global climate models. Many environmental scientists believe that increased cloud cover may be partially countering the effects of global warming by reducing the amount of energy the planet absorbs from the sun. Researchers Athanasios Nenes of the Georgia Institute of Technology and Nicholas Meskhidze - formerly at Georgia Tech but now at North Carolina State University - reported their findings Nov. 2 in Science Express, the online advance publication of the journal Science. The research was sponsored by NASA, the National Science Foundation and a Blanchard-Milliken Young Faculty Fellowship. "Studies like this one may help reshape the way we think about how the biosphere interacts with clouds and climate," said Nenes, an assistant professor in Georgia Tech's School of Earth and Atmospheric Sciences. "One of the largest uncertainties right now in climate models is the ability to predict how clouds would respond to changing particle levels - whether they originate from humans with air pollution or from biological activity. We can now see very strongly the influence of marine biology on oceanic clouds." Researchers had previously theorized that dimethyl sulfide (DMS) - which is also emitted by phytoplankton - affects the formation of clouds by increasing the number of sulfate particles, which can absorb moisture and form cloud droplets. When oxidized, isoprene may enhance the effect of DMS by increasing the number and size of the particles while helping them to chemically attract more moisture. The impact of isoprene on atmospheric particulate matter was previously thought to be important only for terrestrial plants, Nenes said. The researchers stumbled upon the phytoplankton-cloud connection quite accidentally. "While looking at the satellite pictures, I noticed that cloud properties over large phytoplankton blooms were significantly different from those that occurred away from the blooms," recalled Meskhidze, now an assistant professor in NC State's College of Physical and Mathematical Sciences. The Southern Ocean normally has relatively few particles around which cloud droplets can form. The isoprene mechanism could therefore have a significant effect on the development of clouds there - and may account for most of variation in the area's cloud cover. "If a lot of particles form because of isoprene oxidation, you suddenly have a lot more droplets in clouds, which tends to make them brighter," Nenes explained. "In addition to becoming brighter, the clouds can also have less frequent precipitation, so you might have a build-up of clouds. Overall, this makes the atmosphere cloudier and reflects more sunlight back into space." In their paper, the researchers estimated that the isoprene emissions reduced energy absorption in the area by about 15 watts per square meter. "This is a huge signal," said Nenes. "You would normally expect to see a change of a couple of watts." The Southern Ocean is ideal for study because it is largely untouched by pollution and has relatively steady temperature and meteorological conditions during the seasons in which phytoplankton blooms appear. "This seems to be one of those rare regions in the globe where the biology really takes over," Nenes explained. "That allows us to see strongly the impact of biology on the clouds." As a next step, Nenes would like to examine other areas of the globe for similar activity. "There are a lot of areas that have intense biological activity, so with time we are going to explore more regions to see if this is a widespread phenomenon. Chances are that we will see this in other places," he added. Nenes and Meskhidze used data from satellite observations to estimate the amount of chlorophyll in the ocean, the emission of isoprene and its connection to cloud formation. Before this new mechanism can be incorporated into global climate models, however, it will have to be confirmed by field experiments. Atmospheric scientists believe that by blocking sunlight, increased cloudiness has up until now partially mitigated the effects of global warming. The role of oceanic biology on cloud formation could therefore be a major factor in controlling global climate, and the new mechanism identified by Nenes and Meskhidze may make it even more important. This effect needs to be better understood, Nenes noted, because anything that can change global clouds can dramatically alter the impact of greenhouse gases on our changing climate. "It shows that there is still a lot we need to explore to better understand the delicate balance in nature," said Meskhidze. "It will require the cooperative efforts of researchers from many different fields to identify the chemical components in these aerosols, to estimate the amounts of this and other potentially important gases emitted from the ocean, and to better characterize the effort of organics on cloud droplet formation." Georgia Institute of Technology Research News |
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| Related Phytoplankton Current Events and Phytoplankton News Articles Fish food fight: Fish don't eat trees after all, says new study What constitutes fish food is a matter of debate. A high-profile study a few years ago suggested that fish get almost 50 percent of their carbon from trees and leaves, evidence for a very close link between the terrestrial and aquatic ecosystems. Warmer means windier on world's biggest lake Rising water temperatures are kicking up more powerful winds on Lake Superior, with consequences for currents, biological cycles, pollution and more on the world's largest lake and its smaller brethren. Antarctica glacier retreat creates new carbon dioxide store Large blooms of tiny marine plants called phytoplankton are flourishing in areas of open water left exposed by the recent and rapid melting of ice shelves and glaciers around the Antarctic Peninsula. Newly Discovered Fat Molecule: An Undersea Killer with an Upside A chemical culprit responsible for the rapid, mysterious death of phytoplankton in the North Atlantic Ocean has been found by collaborating scientists at Rutgers University and the Woods Hole Oceanographic Institution (WHOI). This same chemical may hold unexpected promise in cancer research. New insight into predicting cholera epidemics in the Bengal Delta Cholera, an acute diarrheal disease caused by the bacterium Vibrio cholerae, has reemerged as a global killer. Outbreaks typically occur once a year in Africa and Latin America. But in Bangladesh the epidemics occur twice a year - in the spring and again in the fall. Iron controls patterns of nitrogen fixation in the Atlantic Scientists including researchers from the National Oceanography Centre, Southampton and the University of Essex have discovered that interactions between iron supply, transported through the atmosphere from deserts, and large-scale oceanic circulation control the availability of a crucial nutrient, nitrogen, in the Atlantic. Climate variability impacts the deep sea Deep-sea ecosystems occupying 60% of the Earth's surface could be vulnerable to the effects of global warming warn scientists writing in the Proceedings of the National Academy of Sciences. Eutrophication affects diversity of algae Eutrophication of the seas may have an impact on genetic variation in algae, research at the University of Gothenburg shows. Mystery Solved: Marine Microbe Is Source of Rare Nutrient A new study of microscopic marine microbes, called phytoplankton, by researchers at Woods Hole Oceanographic Institution (WHOI) and the University of South Carolina has solved a ten-year-old mystery about the source of an essential nutrient in the ocean. New genomic model defines microbes by diet -- provides tool for tracking environmental change In line with the U.S. Department of Energy (DOE) interest in characterizing the biotic factors involved in global carbon cycling, the DOE Joint Genome Institute (JGI) characterizes a diverse array of plants, microorganisms, and the communities in which they reside to inform options for reducing and stabilizing atmospheric greenhouse gases. More Phytoplankton Current Events and Phytoplankton News Articles |
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