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A researcher at UB's Biological and Stable Isotope Biogeochemistry Laboratory, led by Assistant Professor of Geology Elizabeth Thomas, adds solvents to glass columns holding organic matter from lake sediments. This process allows scientists to separate leaf waxes and bacterial lipids for further analysis. Although the samples presented here have not been used in the new study, the methods described reflect the procedures of the research team. Credit: Douglas Levere / University of Buffalo
The Arctic is warming faster than the rest of the planet and in doing so, it should become more humid. But why? What mechanisms could lead these changes?
A new study looks at history to find answers, examining what happened in the region during a period of global warming some 8,000 years ago. Research has highlighted that in this ancient era, the west of Greenland had become wetter, a trend often related to increased rainfall. The study further shows that two different climate processes may have contributed to this high humidity. The processes are:
- As the Arctic heats up, the sea ice melts, exposing regional waters to the sun, to the air and to increased evaporation.
- As the planet heats up, the humidity increases further in areas closer to the equator. This creates an imbalance in the overall humidity and, ultimately, moist air from low latitudes is sucked into the drier Arctic.
"We used geological evidence to determine that these two processes probably contributed to an increase in humidity in West Greenland when the region warmed up rapidly 8,000 years ago" says researcher Elizabeth Thomas, Ph.D., assistant professor of geology at the university. at the College of Arts and Sciences, Buffalo. "As such, the two processes could be used again today, contributing to any future increases in Arctic moisture and, ultimately, precipitation." "
"We do not have detailed written documentation on precipitation in the Arctic, so we do not understand how precipitation could increase in response to warming," she said. This is an important area of study, she adds, because "precipitation in the Arctic has complex interactions with the climate, and it has an impact on plant communities and the environment. how quickly glaciers can shrink. "
The study was published this month in Letters of geophysical research by a team of scientists from UB, the University of Massachusetts and Northern Arizona University. The research was funded by the National Science Foundation.
A sample of organic matter extracted from lacustrine sediments at the bottom of a flask. The new study was based on data from similar samples extracted from the bottom of Lake Sikuiui, in West Greenland. Credit: Douglas Levere / University of Buffalo
Indices in the mud of the lake bottom
To learn more about the climate history of West Greenland, scientists have analyzed the lake bottom mud dating back thousands of years. This sediment contains organic materials, such as old leaf waxes and compounds produced by bacteria, that reveal information about the region's climate past.
As Thomas explains, with regard to leaf waxes, weather conditions influence the chemical content of these waxes so that scientists can determine. Specifically, leaf waxes contain small amounts of a rare form of hydrogen called deuterium, and the concentration of deuterium may increase or decrease depending on factors such as humidity and precipitation patterns. (An example: in Arctic leaf waxes, deuterium concentrations fluctuate with local precipitation or clouds traveling long distances from low latitudes to the region).
Chemicals called glycerol tetraethers and branched dialkylglycerol (GDGT), produced by bacteria, also hold clues about past climate. The composition of these compounds varies depending on the ambient temperature at the time they were produced. As a result, scientists can use branched GDGTs to reconstruct trends in prehistoric temperature, Thomas explains.
Elizabeth Thomas, assistant professor of geology at UB, holds a sediment core – a cylindrical sample of lake bed mud. These samples contain organic matter that can be analyzed to learn more about the past climate of a region. The new study was based on data from a sediment core extracted from the bottom of Lake Sikuiui, in West Greenland. Credit: Douglas Levere / University of Buffalo
These chemical indicators allowed Thomas' team to study the old trends in moisture and rainfall in West Greenland, while the area was warming around 8000 years old. The new research was based on leaf waxes and branched GDGTs found in a sample of sediment that the team had extracted from the bottom of Lake Sikuiui, in western Greenland.
"These chemical indicators are relatively new tools and they allow us to do research on the ancient climate in a way that was not possible before," Thomas said. "We can use these tools to study the fluctuations of humidity in a region thousands of years ago or to determine whether storms in a region have a local or distant origin. that has happened in ancient times can help us understand what could happen today as the climate changes. "
Explore further:
A history of snowfall on Greenland, hidden in old leaf waxes
More information:
E. K. Thomas et al, A wetter Arctic coinciding with the warming of the hemisphere 8,000 years ago, Letters of geophysical research (2018). DOI: 10.1029 / 2018GL079517
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