*Permafrost is ground that remains frozen for at least two consecutive years.* It is found in cold climates, such as the Arctic and Antarctic, and is an important part of the global climate system. Permafrost stores large amounts of carbon, and when it melts, this carbon is released into the atmosphere, contributing to climate change.

*A new study published in the journal Nature Geoscience has found that permafrost has undergone significant shifts over the last 400,000 years.* The study used cave deposits in the Yukon Territory of Canada to reconstruct past permafrost conditions. The researchers found that permafrost was much more extensive during the last glacial period, which ended about 11,700 years ago, than it is today. Permafrost also retreated significantly during the early Holocene, a period of warm climate that lasted from about 11,700 to 4,000 years ago.

*The study's findings are surprising because they suggest that permafrost is more sensitive to climate change than previously thought.* The researchers say that the results of the study have implications for understanding the future of permafrost and its role in the global climate system.

*The study is also important because it provides a new way to study past permafrost conditions.* Cave deposits are a valuable archive of past environmental conditions, and they can be used to reconstruct climate history in a way that is not possible with other methods.

*The study's findings are a reminder that permafrost is an important part of the global climate system and that it is vulnerable to climate change.* Understanding how permafrost has responded to past climate change is essential for understanding how it will respond to future climate change.