Archives par mot-clé : Permafrost


by B. Van Vliet-Lanoé & A. Gudmundsson, Feb 2020, in ResearchGate

Permafrost developed from Termination Ia (Bölling interstadial, 14.5 cal ka BP) in Northern Iceland, in answer to deglaciation. Permafrost persisted or even re-extended during the Preboreal cooling events (at 11.2, 10.3 and 9.3 cal ka BP) synchronic with pulsated glacial advances. It disappeared below 1000 masl during the Thermal Optimum (8-5 cal ka BP). The present-day re-extent was controlled with the cooling related with the Little Ice Age and particularily the Maunder solar Minimum. Continuous permafrost is stable above 1000 masl, but is today melting between 900 and 800 masl. Discontinuous permafrost is vanishing today with the recent climate warming (from 1970), especially in palsa bogs, and on valley slopes with thermokarstic mass wasting.

Thawing Permafrost Could Leach Microbes, Chemicals Into Environment

by C. Rotter, Mar 10, 2022 in WUWT

Scientists are turning to a combination of data collected from the air, land, and space to get a more complete picture of how climate change is affecting the planet’s frozen regions.

Trapped within Earth’s permafrost – ground that remains frozen for a minimum of two years – are untold quantities of greenhouse gases, microbes, and chemicals, including the now-banned pesticide DDT. As the planet warms, permafrost is thawing at an increasing rate, and scientists face a host of uncertainties when trying to determine the potential effects of the thaw.

paper published earlier this year in the journal Nature Reviews Earth & Environment looked at the current state of permafrost research. Along with highlighting conclusions about permafrost thaw, the paper focuses on how researchers are seeking to address the questions surrounding it.

Infrastructure is already affected: Thawing permafrost has led to giant sinkholes, slumping telephone poles, damaged roads and runways, and toppled trees. More difficult to see is what has been trapped in permafrost’s mix of soil, ice, and dead organic matter. Research has looked at how chemicals like DDT and microbes – some of which have been frozen for thousands, if not millions, of years – could be released from thawing permafrost.

Then there is thawing permafrost’s effect on the planet’s carbon: Arctic permafrost alone holds an estimated 1,700 billion metric tons of carbon, including methane and carbon dioxide. That’s roughly 51 times the amount of carbon the world released as fossil fuel emissions in 2019. Plant matter frozen in permafrost doesn’t decay, but when permafrost thaws, microbes within the dead plant material start to break the matter down, releasing carbon into the atmosphere.

Ancient methane might not pose a major climate risk

by Nature, February 21, 2020

Bubbles in Antarctic ice suggest that warming will not result in massive release of long-buried methane.

Runaway global warming driven by the release of methane from the Arctic seems less likely than some scientists have feared.

Methane and its components can be locked up for millennia in permafrost — a frozen mixture of soil and ice — and in deposits of crystal-like structures called methane hydrates. Methane released by modern organic materials contains a form of carbon that methane from ancient sources does not, allowing scientists to distinguish between the two types.

Michael Dyonisius at the University of Rochester in New York and his colleagues analysed Antarctic ice cores to determine the origins of methane released during a warming period that ended the last ice age. The warming raised global temperature by roughly 4ºC — slightly more than the rise projected to occur by 2100 in most scenarios of human-induced climate change.

The team’s results suggest that methane emissions during that big thaw were dominated by emissions from wetlands, not by the release of ancient methane from melting permafrost and methane hydrates. The authors conclude that modern climate change is unlikely to trigger a massive release of ancient methane.