System Earth 5b

Quiz + Cryosphere II

Misha Velthuis

m.velthuis@uva.nl

Fri 4 Oct 2024

Last time

Snow

Glaciers

Sea ice

Permafrost (not yet!)

Permafrost

Basic structure

On average: heated from below (geothermal ≈ 0.03 W/m²), cooled from above (heat is lost to the atmosphere).

At a certain depth, the temperature does not change throughout the year anymore (it takes too long for temperature differences to travel to this depth). (Which does not mean that the temperature at this depth is unrelated to atmospheric temperatures. It is just not changing throughout the seasons).

Base of permafrost is where temperature reaches 0°C.

Zone of seasonally variant temperature divided in part that always remains below 0°C, and the "active zone", which temporarily exists above 0°C.

How does the organic material get into the permafrost?

Soils expand with sediment and organic material input → what used to be part of the active layer, gets 'enclosed' under the Permafrost table (soil expansion: see e.g. this article that I co-authored).
Also: cryoturbation.

Thermokarst in the Netherlands

Permafrost degradation

Greenhouse gases in permafrost

Link to FAQ AR6 WGI

"The Arctic is the biggest climate-sensitive carbon pool on Earth, storing twice as much carbon in its frozen soils, or permafrost, than is currently stored in the atmosphere."

"The projections from these permafrost carbon models show a wide range in the estimated strength of a carbon–climate vicious circle, from both carbon dioxide and methane, equivalent to 14–175 billion tonnes of carbon dioxide released per 1°C of global warming. By comparison, in 2019, human activities have released about 40 billion tonnes of carbon dioxide into the atmosphere." (Using higher estimate of 175 GT: 1.5°C warming causes greenhouse gases equivalent to (175*1.5)/40=6.56 years (using 2019 emissions).

"…the models do not identify any one amount of warming at which permafrost thaw becomes a ‘tipping point’ or threshold in the climate system that would lead to a runaway global warming. However, models do project that emissions would continuously increase with warming, and that this trend could last for hundreds of years."

Zombie viruses

Link to article.

"In 1733, an Inuit boy and girl who had been sent to Denmark for the king’s coronation 2 years earlier sailed back home to Greenland. Both were in a “sickly state of health” during the trip, according to an account written a few decades later by a missionary, and the girl died on the way. Shortly after reaching his native land that September, the boy also died, of “a cutaneous disorder.” He had brought smallpox with him, and the disease raced around the island, killing Inuits and Europeans alike. Another missionary wrote of “houses tenanted only by the corpses of their former occupants, and dead bodies lying unburied on the snow.” The outbreak lasted until at least June of the next year, killing maybe half of Greenland’s already sparse population."

This is scary because:

"Smallpox was an infectious disease caused by variola virus (often called smallpox virus), which belongs to the genus Orthopoxvirus.[7][11] The last naturally occurring case was diagnosed in October 1977, and the World Health Organization (WHO) certified the global eradication of the disease in 1980,[10] making smallpox the only human disease to have been eradicated to date." wiki

There are also worries that permafrost pathogens could infect livestock—and then spill over into humans. The Norse brought sheep when they settled the island around 1000 C.E., but both the animals and the Norse were gone by 1450. “With climate change, Greenland expects to start having sheep farming again,” Aarestrup says. “As a vet, this is something that you immediately start getting concerned about because this potentially is bringing a completely immune-naïve population of animals into an area.”