February 2, 2023
Dulcinea Groff, a postdoctoral fellow in the Department of Geology and Geophysics at the University of Washington, used the radiocarbon dates, or death dates, of previously ice-buried dead black moss to show that glaciers advanced in three distinct stages. was a member of the research team that revealed Northern Antarctic Peninsula over the past 1,500 years. This landscape scene from Cape Rasmussen shows where the glacial ice has retreated and the black moss has been exposed. Groff was the first author of a recent paper on the team’s work published in Geology. (Derek Ford photo)
Glacier retreat north of the Antarctic Peninsula has found and re-exposed black moss that marks the date of vegetation radiocarbon depletion. This is an important clue to understanding when glaciers have advanced in the past in the region.
University of Wyoming researchers found that such events occurred 1,300, 800, and 200 years earlier than 1950, corroborating evidence for glacier advance from other studies and the date of black moss extinction. led a study that found concordance.
“We used radiocarbon dates, or kill dates, of previously ice-buried dead black moss to reveal three distinct stages of glacier progression in the northern Antarctic Peninsula over the past 1,500 years.” says Dulcinea Groff, a postdoctoral fellow at UW. Department of Geology and Geophysics.
Groff says, “Date palms from re-exposed black moss curb past glacier advance in northern Antarctica” Appears on January 20 geologyis a journal that publishes relevant, timely, innovative and provocative articles for an international audience, representing research in all areas of earth science.
Researchers from Lehigh University in Changchun, Jilin, China, University of Hawaii at Manoa, Northeast Normal University, and the Chinese Academy of Sciences contributed to this paper.
Moss is one of the few plants that live in Antarctica and can be overwritten and killed by glacial advancement. The period when glaciers exterminated moss provides an archive of glacial history, says Grof.
For example, as a glacier expands or advances, it can bury or cover vegetation. This causes plants to lose light and warmth. The date the plant died is the same time the glacier advanced over the site.
“As the glacier retreats, these previously buried mosses are exposed, dying and turning black,” Groff explains. “What makes these records so valuable compared to other records is their accuracy, such as glacial instability and penguin fossils. It provides a clearer picture of climate history due to the reduction in estimation error.”
Glacial erratics are rocks deposited by glaciers that differ from natural rocks in certain areas.
The Antarctic Peninsula’s terrestrial cryosphere and biosphere are rapidly changing as “first responders” to polar warming, Groff said.
“We know from other studies that large glaciers on the Antarctic Peninsula are responding quickly to rising summer temperatures. We are modeling the expansion of glaciers,” says Groff. “However, we know very little about how this plays out at the surface, where ice, oceans and sensitive coastal organisms interact. It will enhance our understanding of biodiversity coastal ecosystems that thrive on , penguins and plants and their susceptibility on the Antarctic Peninsula.”
According to Grof, one of the limitations in reconstructing glacier history is that there are few types of terrestrial archives that can be used to constrain past glacier behavior. By dating re-exposed dead vegetation, abandoned penguin colonies and rocks, we can better understand the timing of past permanent snow and glacier advances.
According to the paper, during the summers of 2019 and 2020, a research field team including Groff collected black moss from Robert Island, Ambers Island, Charles Point and Cape Rasmussen. The group examined and cleaned 39 black moss samples.
“We collected black moss around the northern Antarctic Peninsula by probing the edges of glaciers and nunataks at several locations. Radiocarbon dating of the moss shows that the glacier has progressed three times in the last 1,500 years. “We had a lot of fun,” says Groff. “This is evidence of a phase of cooler and potentially wetter conditions than today.”
On Ambers Island, the group found that the glacier was last in its 2019 position about 850 years ago and has expanded over the centuries.
“Our estimates of glacier advance are much slower than recent retreat,” she says. “Interestingly, we also found that the fastest advancing glacier fronts retreated the fastest, suggesting that hotspots of rapid coastal glacier dynamics occur on the Antarctic Peninsula.”
Grof says that the datasets her group compiled are unique, and historical net advance rates are rarely in the literature because glacial advance tends to destroy the glacial record. increase. These black mosses can therefore be reliably used to extrapolate past glacier advances.
“There is other evidence to support moss die-off dates in past cold conditions, including peat records showing reduced biological productivity and evidence of sea level change from raised beaches as a result of ice mass changes. “There is,” she says. colonies are the same age as our youngest black moss.”
The National Science Foundation funded this research.