A University of Arkansas researcher and her colleagues studied core sediments from a shallow boreal lake and found that storm activity has increased substantially over the past 150 years.
The rise in storm frequency appears to be linked to solar activity, but also may be linked to higher global temperatures resulting from increased amounts of greenhouse gases.
Sonja Hausmann and Falko Fye, professors of geosciences at the University of Arkansas; Isabelle Larocque-Tobler of the University of Bern, Switzerland; Pierre Richard of the University of Montréal, Canada; Reinhard Pienitz of Laval University, Québec City, Canada; and Guillaume St-Onge of the University of Québec at Rimouski, Canada, report their findings in The Holocene.
“We don’t really know if it is solar activity or if it is greenhouse gases because what we found correlates with both,” Hausmann said.
In the last 150 years, human activity has considerably increased the concentration of greenhouse gases in the atmosphere. Greenhouse gases trap heat in the lower atmosphere of Earth, raising the Earth’s temperature. Scientists have predicted that rising temperatures could lead to more frequent storms, and Hausmann’s evidence supports this.However, Hausmann also compared the diatom-storm evidence to solar activity, which includes sunspots. Solar activity peaks and dips on 11-year and longer cycles. The diatom activity appears to fluctuate with the solar cycles, with stormy periods coinciding with high solar activity.
The researchers took core samples at Lac du Sommet, a shallow mountain lake in the Laurentian Mountains of eastern Canada. They were able to extend their climate reconstruction back 9,500 years.
Hausmann studies diatoms, unicellular algae with shells of silica, which remain in the sediments. Diatoms make excellent bioindicators, Hausmann said, because the diatom community composition changes with environmental changes in acidity, climate, nutrient availability and lake circulation.
By examining relationships between modern diatom communities and their environment, Hausmann and her colleagues can reconstruct various historic environmental changes quantitatively. In this case, they examined the residual effect of storms on the diatom communities in lake sediments. High winds cause the water column to circulate and mix the diatoms and nutrients in the water.
In the absence of wind, diatoms settle at the lake bottom where they have less light. The researchers compared the diatom community structures to wind records from a nearby weather station established in 1965 and found that they matched well. They then examined the diatom community structures for the past 9,500 years.The diatom evidence shows that storms have increased substantially over the last 150 years, Hausmann said.
She and her colleagues compared these findings to other tiny proxies: non-biting midges and pollen. Midge larvae live in the lake sediment and act as good indicators of temperature changes in a given environment. At Lac du Sommet, the midge evidence shows that temperature, while variable, has not recently increased in the same manner. Pollen evidence tells a similar story.
“The diatoms do not show a temperature effect. They show wind,” Hausmann said. “We are looking at climate change, not just temperature differences.”
Hausmann will return to Lac du Sommet during decreased periods of solar activity to see if diatom activity shows a similar decrease.CONTACTS:
Melissa Lutz Blouin | Newswise Science News
Less radiation in inner Van Allen belt than previously believed
21.03.2017 | DOE/Los Alamos National Laboratory
Mars volcano, Earth's dinosaurs went extinct about the same time
21.03.2017 | NASA/Goddard Space Flight Center
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
22.03.2017 | Materials Sciences
22.03.2017 | Physics and Astronomy
22.03.2017 | Materials Sciences