Kill the days of newly exposed black moss

image: Cape Rasmussen, one of the study sites mentioned in the paper. Credit: Derek J. Ford.
vision Again

Credit: Derek J. Ford

Boulder, Colo., USA: In their new paper for the journal of the Geological Society of America GeologyDulcinea Groff and colleagues used radiocarbon dating (dates of death) of ice-covered black moss to reveal that the ice continued in three distinct phases on the northern Peninsula of Antarctic 1,500 years ago.

The terrestrial cryosphere and the biosphere of the Antarctic Peninsula are rapidly changing as “first responders” to polar warming. We know from other studies that the large glaciers on the Antarctic Peninsula respond quickly to warmer summer air temperatures, and scientists have modeled that the ice has expanded in the past due to warmer temperatures. cooling, not increased rainfall. However, we know very little about how this happens at the ocean level where ice, sea and marine life interact. Knowing when the ice rose in the past would improve our understanding of the diversity of coastal ecosystems—thriving with seals, penguins, and plants—and how they affect the Antarctic Peninsula. One of the limitations of reconstructing the history of the ice is that there are not many types of storage areas of the earth that we can use to constrain the past behavior of the ice. Dead plants that have regenerated, abandoned penguin colonies, and rocks can be labeled to better identify periods of snow or permafrost in the past.

Lichens are one of the few types of plants that live in Antarctica and can be overwhelmed and killed by the advancing ice. The time when the ice killed the lichen provides a record of the ice’s history. For example, when ice expands or advances, it can bury or cover the plant—starving it of light and warmth. The day the plant died is the time the ice reached the area. As the ice recedes, the lichens are exposed and dead and black. “What’s important about these kill dates compared to other records (such as the age of the ice retreat or the number of penguins left) is their accuracy,” Groff says. a clearer history of climate due to the exchange of carbon with the atmosphere and reduced errors in age estimation.

Groff and colleagues collected black moss around the northern Antarctic Peninsula by surveying the edges of ice and nunataks in several locations. Using the radioactivity of the lichen, they found that the ice has advanced three times in the last 1,500 years. This is evidence of layers of cooler and possibly wetter conditions than today. On the island of Anvers, they learned that the last time the ice was in its place in 2019 was 850 years ago as it grew over several centuries. Their estimates of ice advance are much slower than recent returns. “Interestingly, we found that the ice front with the fastest speed also retreated the fastest, suggesting that the areas that Coastal tidal waves occur on the Antarctic Peninsula.

This is a unique data collection because it is not easy to have past rates in the books because the ice records are often destroyed as the ice ages. This black moss can be reliably used to estimate the advance of the ice in the past. “There is other evidence to support our moss-killing dates for past cooler conditions, such as peat records showing low biological productivity, as well as evidence of sea-level change from the uplifted coasts due to ice change. It is also possible that the climatic conditions that caused the ice advance affected the humidity levels and could have had a negative effect on the penguins, as “We know they do today. Most of the newly abandoned penguin colonies are the same size as our black moss,” says Groff.


Killing days of newly exposed black algae disrupt the advance of past ice on the northern Antarctic Peninsula.
Dulcinea V. Groff, David W. Beilman, Zicheng Yu, Derek Ford;
Contact: Dulcinea V. Groff,, Department of Geology & Geophysics, University of Wyoming, Laramie, Wyoming 82073, USA; Department of Earth and Environmental Sciences, Lehigh University, Bethlehem, Pennsylvania 18015, USA

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