Storyboard: What is permafrost?

What is permafrost?

• Permafrost is ground that stays frozen for at least two consecutive years, covering nearly a quarter of the Northern Hemisphere.
• As Arctic temperatures rise rapidly, this frozen ground begins to thaw，causing the land to subside, damaging roads and buildings, and releasing ancient carbon stores in the form of greenhouse gases.
• The thaw of permafrost is both a local hazard and a global climate concern.

Modeling the permafrost thaw

The objective: To quantify land surface subsidence and the potential risks of permafrost thawing in the Arctic region

Illustrations of the process understanding (left) and how it is simulated in the CTSM-EXICE model (right).

The Arctic is changing – fast

CNRM-driven runs are warmer than NORESM-driven ones, so they are coloured in warmer colours. The 2 m temperature increase is visible everywhere in the Arctic, and warming is more pronounced in the autumn and winter seasons.

Soil temperature at 1 m depth

Smaller increase rate than T2.

Rainfall

A more pronounced increase in rainfall is also related to the CNRM-driven runs, and patterns are very similar to T2. Spring, summer and autumn are expected to have the strongest rainfall increase.

Rainfall

Interannual variability in snowfall patterns is high. Snowfall decline is faster in CNRM-driven runs. There are regional differences in snowfall patterns, and a strong decline is associated with coastal Norway, among others. Spring and summer are the seasons of the most pronounced snowfall decline throughout the period.

Permafrost extent in 2015 (in blue)

Permafrost extent in 2099 (in blue)

A change in the regional permafrost extent is very similar across configurations.

The entire Arctic

• CNRM-driven simulations show a stronger decrease in permafrost extent
• Our work accounts for two permafrost area extent definitions

Steinert et al. (2023) include a global permafrost change (also areas outside of the Arctic).

Change in permafrost area (2015 – 2099)

Using one definition or the other yields very similar results.

Future: areas of greatest ground subsidence

• The regions of projected largest ground subsidence lie between 60° and 70° N
• 5 regions of the same spatial extent across the respective latitude belt are selected as they are projected to experience more than 1 m of ground subsidence until 2100

Future subsidence changes

The period of the stronger subsidence depends on the region. A seemingly faster subsidence is from 2050-2060 onwards.

• The most pronounced change in subsidence (25 cm from present-day on average across the models) is in Canada (Region 5)
• The uncertainty in subsidence magnitude is the largest in Region 4 (Alaska-Bering Sea)

Future subsidence changes

In most regions, permafrost outputs from GCMs are more similar to each other than those from RCMs.

• CNRM-HCLIM-CTSM shows the fastest rate of permafrost thaw across the regions
• The largest decrease in permafrost area extent is expected in Region 2 (around the Lena river) in Russia