Soil layers of permafrost that scientists expected to remain frozen for at least 70 more years have already begun thawing.

In the Canadian Arctic, layers of permafrost that scientists expected to remain frozen for at least 70 years have already begun thawing.
The once-frozen surface is now sinking and dotted with melt ponds and from above looks a bit like Swiss cheese, satellite images reveal.
“We were astounded that this system responded so quickly to the higher air temperatures,” said Louise Farquharson,
a co-author of the study and postdoctoral fellow at the Permafrost Laboratory at the University of Alaska Fairbanks.

At sites in the Canadian Arctic we have observed that warmer than average summer air temperatures have caused the active layer to deepen, near‐surface ground ice to melt,
and the overlying ground surface to subside, in some cases leading to the formation of small thaw ponds.

The study examined data collected between 1990 and 2016, and found an increase of up to 4 °C in the permafrost,
and this trend is now expected to continue as Arctic mean annual air temperatures increase at a rate twice that of lower latitudes.

We observed permafrost degradation and thermokarst development in the form of top‐down melt of ice‐wedge ice across all three study sites.

Active layer deepening and the subsequent thermokarst development took place during summers with higher thawing indexes.
Air temperature measurements for thawing index (TI); is the cumulative number of thawing degree‐days above 0°C per year.

Most notably during 2007, 2011, and 2012, when the thaw front intersected massive ice remarkably early in the season.

For all sites, the maximum observed thaw depths observed since 2003 met or exceeded the projected thaw depths for 2090 under the RCP 4.5 scenario,
indicating that the depth of thaw is already routinely exceeding the thaw expected for this temperature projection.

Also in 2019, at other study sites of the Canadian Arctic, permafrost is melting so fast that it’s gulping up the equipment left there to study it. “The ground thaws and swallows it,” said Merritt Turetsky,
a University of Guelph biologist whose new research warns the rapid melt could dramatically increase the amount of greenhouse gases released from ancient plants and animals frozen within the tundra.

“We’ve put cameras in the ground, we’ve put temperature equipment in the ground, and it gets flooded. It often happens so fast we can’t get out there and rescue it.
Permafrost in Arctic is melting so fast it’s swallowing science equipment

Not only are projections off, thaw melt rates much more than expected, yest another 2019 study concluded that carbon from thawing permafrost is already released at higher rates than previously thought.

This study was novel because we used new methods to directly track the soil carbon losses, and they were much higher than we previously thought, co-author Schuur said.
Our results suggests that not only is carbon being lost through greenhouse gases directly to the atmosphere but also dissolved in waters that flow through the soil and likely carried carbon into streams, leaves and rivers.

Thawing permafrost affects plant and soils in tundra ecosystems, and ultimately the storage of carbon in permafrost soils. The surface of tundra subsides as ice in permafrost melts and drains.
This can mask the loss of soil carbon through time that occurs as a result of soil microbial activity converting soil organic matter into greenhouse gases carbon dioxide and methane.

Accounting for ground subsidence as a result of thaw revealed that substantial quantities of soil carbon were loss both directly to the atmosphere as carbon dioxide, but also dissolve in water that drained from this site.
Soil carbon loss from permafrost ecosystems that ends up in the atmosphere at greenhouse gases can ultimately accelerate climate change.

A decade of remotely sensed observations highlight complex processes linked to coastal permafrost bluff erosion in the Arctic (2018)





Leave your comment

Your email address will not be published. Required fields are marked *