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The Arctic is warming faster than the rest of the planet and, in doing so, it should become wetter. 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 shows that in ancient times, western Greenland had become wetter, a trend often related to increased precipitation. 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 area warmed up rapidly 8,000 years ago" says lead researcher Elizabeth Thomas, Ph.D., assistant professor of geology at the university. at the College of Arts and Sciences, Buffalo. "As such, both processes could be used again today, contributing to any future increases in Arctic moisture and, ultimately, precipitation." "
"We do not have long or detailed records of rainfall in the Arctic, so we do not fully understand how precipitation could increase in response to warming," she says. This is an important area of study, she adds, because "precipitation in the Arctic has complex interactions with the climate. They also have an impact on plant communities and the speed with which 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.
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. These sediments contain organic matter, such as old leaf waxes and compounds produced by bacteria, that reveal information about the region's climate history.
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.
These chemical indicators allowed Thomas's team to study the old patterns of moisture and precipitation in West Greenland, as the region warmed about 8,000 years ago. 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 study the ancient climate in a way that was not possible before," says Thomas. "We can use these tools to study the fluctuations of humidity in an area thousands of years ago or to determine whether storms have a local or distant origin. This is important because understanding what has happened in ancient times can help us understand what could happen with climate change today. "
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
The Arctic is warming faster than the rest of the planet and, in doing so, it should become wetter. 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 shows that in ancient times, western Greenland had become wetter, a trend often related to increased precipitation. The study further shows that two different climate processes may have contributed to this high humidity. The processes are:
"We used geological evidence to determine that these two processes probably contributed to an increase in humidity in West Greenland when the area warmed up rapidly 8,000 years ago" says lead researcher Elizabeth Thomas, Ph.D., assistant professor of geology at the university. at the College of Arts and Sciences, Buffalo. "As such, both processes could be used again today, contributing to any future increases in Arctic moisture and, ultimately, precipitation." "
"We do not have long or detailed records of rainfall in the Arctic, so we do not fully understand how precipitation could increase in response to warming," she says. This is an important area of study, she adds, because "precipitation in the Arctic has complex interactions with the climate. They also have an impact on plant communities and the speed with which 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.
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. These sediments contain organic matter, such as old leaf waxes and compounds produced by bacteria, that reveal information about the region's climate history.
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.
These chemical indicators allowed Thomas's team to study the old patterns of moisture and precipitation in West Greenland, as the region warmed about 8,000 years ago. 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 study the ancient climate in a way that was not possible before," says Thomas. "We can use these tools to study the fluctuations of humidity in an area thousands of years ago or to determine whether storms have a local or distant origin. This is important because understanding what has happened in ancient times can help us understand what could happen with climate change today. "
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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