Reply to the comment: Northern Hemisphere permafrost extent: Drylands, glaciers and sea floor

Obu, Jaroslav; Westermann, Sebastian; Bartsch, Annett; Berdnikov, Nikolai M.; Christiansen, Hanne H.; Dashtseren, Avirmed; Delaloye, Reynald; Elberling, Bo; Etzelmüller, Bernd; Kholodov, Alexander; Khomutov, Artem; Kääb, Andreas; Leibman, Marina; Lewkowicz, Antoni G.; Panda, Santosh K.; Romanovsky, V. E.; Way, Robert G.; Westergaard‐Nielsen, Andreas; Wu, Tonghua; Yamkhin, Jambaljav; Zou, Defu

doi:10.1016/j.earscirev.2019.103036

Cited by 7 publications

(20 citation statements)

References 3 publications

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“…The ALT rapidly decreases to 87.8 cm (25%-75% quantile: [62.7, 94.7] cm) in the region poleward of 50 • N latitude, corresponding to the main discontinuous to continuous permafrost regions in the NPR. The latitudinal patterns of mean ALT were similar among different percentages of permafrost extent and similar to a recent ML derived ALT map (Ran et al 2022) and the process-model based CCI ALT map (Obu et al 2021). However, there were some differences observed in the Qinghai-Tibet and Mongolian plateaus among the different datasets.…”

Section: Spatial and Temporal Patterns Of Altsupporting

confidence: 84%

Widespread deepening of the active layer in northern permafrost regions from 2003 to 2020

Liu,

Kimball,

Ballantyne

et al. 2023

Environ. Res. Lett.

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The changing thermal state of permafrost is an important indicator of climate change in northern high latitude ecosystems. The seasonally thawed soil active layer thickness (ALT) overlying permafrost may be deepening as a consequence of enhanced polar warming and widespread permafrost thaw in northern permafrost regions (NPRs). The associated increase in ALT may have cascading effects on ecological and hydrological processes that impact climate feedback. However, past NPR studies have only provided a limited understanding of the spatially continuous patterns and trends of ALT due to a lack of long-term high spatial resolution ALT data across the NPR. Using a suite of observational biophysical variables and machine learning (ML) techniques trained with available in situ ALT network measurements (n = 2966 site-years), we produced annual estimates of ALT at 1 km resolution over the NPR from 2003 to 2020. Our ML-derived ALT dataset showed high accuracy (R 2 = 0.97) and low bias when compared with in situ ALT observations. We found the ALT distribution to be most strongly affected by local soil properties, followed by topographic elevation and land surface temperatures. Pair-wise site-level evaluation between our data-driven ALT with Circumpolar Active Layer Monitoring data indicated that about 80% of sites had a deepening ALT trend from 2003 to 2020. Based on our long-term gridded ALT data, about 65% of the NPR showed a deepening ALT trend, while the entire NPR showed a mean deepening trend of 0.11 ± 0.35 cm yr−1 [25%–75% quantile: (−0.035, 0.204) cm yr−1]. The estimated ALT trends were also sensitive to fire disturbance. Our new gridded ALT product provides an observationally constrained, updated understanding of the progression of thawing and the thermal state of permafrost in the NPR, as well as the underlying environmental drivers of these trends.

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Section: Spatial and Temporal Patterns Of Altsupporting

confidence: 84%

Widespread deepening of the active layer in northern permafrost regions from 2003 to 2020

Liu,

Kimball,

Ballantyne

et al. 2023

Environ. Res. Lett.

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“… The BAWLD‐RECCAP2 region defined as the northern permafrost extent (data from Obu et al., 2021) restricted to the Boreal Arctic Wetlands and Lakes Data set area (BAWLD, Olefeldt et al., 2021). The Figure overlays the extents of the Boreal Forests and the Tundra on the BAWLD‐RECCAP2 region as well as the observation sites used for upscaling GHGs.…”

Section: Methodsmentioning

confidence: 99%

The Net GHG Balance and Budget of the Permafrost Region (2000–2020) From Ecosystem Flux Upscaling

Ramage,

Kuhn,

Virkkala

et al. 2024

Global Biogeochemical Cycles

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The northern permafrost region has been projected to shift from a net sink to a net source of carbon under global warming. However, estimates of the contemporary net greenhouse gas (GHG) balance and budgets of the permafrost region remain highly uncertain. Here, we construct the first comprehensive bottom‐up budgets of CO2, CH4, and N2O across the terrestrial permafrost region using databases of more than 1000 in situ flux measurements and a land cover‐based ecosystem flux upscaling approach for the period 2000–2020. Estimates indicate that the permafrost region emitted a mean annual flux of 12 (−606, 661) Tg CO2–C yr−1, 38 (22, 53) Tg CH4–C yr−1, and 0.67 (0.07, 1.3) Tg N2O–N yr−1 to the atmosphere throughout the period. Thus, the region was a net source of CH4 and N2O, while the CO2 balance was near neutral within its large uncertainties. Undisturbed terrestrial ecosystems had a CO2 sink of −340 (−836, 156) Tg CO2–C yr−1. Vertical emissions from fire disturbances and inland waters largely offset the sink in vegetated ecosystems. When including lateral fluxes for a complete GHG budget, the permafrost region was a net source of C and N, releasing 144 (−506, 826) Tg C yr−1 and 3 (2, 5) Tg N yr−1. Large uncertainty ranges in these estimates point to a need for further expansion of monitoring networks, continued data synthesis efforts, and better integration of field observations, remote sensing data, and ecosystem models to constrain the contemporary net GHG budgets of the permafrost region and track their future trajectory.

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“…In this sense, we want to highlight that conditions similar to those presented here for Greenland may be found across the entire Arctic region. To support this statement, we propose a rough estimate of degradation potential for mountain permafrost by overlaying the GlobPermafrost map of current ground temperatures (Obu et al, 2019) with the terrain roughness index (Amatulli et al, 2020) to quantify the ground temperature distribution in mountain terrain (defines as having a terrain roughness index larger than 450) (Figure 5). According to this analysis, Greenland hosts 30 000 km 2 of mountain terrain affected by continuous permafrost (defined by Obu et al, 2019, as having a temperature <-1.71 °C), accounting for only roughly 30% of the total continuous permafrost in the mountains of the Arctic.…”

Section: Evolution Of Rock Wall Permafrostmentioning

confidence: 99%

“…To support this statement, we propose a rough estimate of degradation potential for mountain permafrost by overlaying the GlobPermafrost map of current ground temperatures (Obu et al, 2019) with the terrain roughness index (Amatulli et al, 2020) to quantify the ground temperature distribution in mountain terrain (defines as having a terrain roughness index larger than 450) (Figure 5). According to this analysis, Greenland hosts 30 000 km 2 of mountain terrain affected by continuous permafrost (defined by Obu et al, 2019, as having a temperature <-1.71 °C), accounting for only roughly 30% of the total continuous permafrost in the mountains of the Arctic. The other regions sharing most of the mountain permafrost in the Arctic are the Verkhoyansk and Chersky Ranges in Siberia (27% c.ca), and the Arctic Cordillera in Canada (33% c.ca).…”

Section: Evolution Of Rock Wall Permafrostmentioning

confidence: 99%

“…Despite the significant impact of these events on local communities, the current understanding of rock wall permafrost in Greenland has some critical gaps. First, our knowledge of its distribution remains limited, as permafrost in this region is described only by large scale models (Obu et al, 2019;Gruber 2012), calibrated on temperature data from sedimentary permafrost and/or at a spatial resolution that is too low to describe the complexity of mountain terrain that dominates permafrost in this context (Marcer et al, 2024a(Marcer et al, , 2024b. Secondly, we currently have little knowledge of the regional patterns of future mountain permafrost evolution in Greenland, as most of the available studies focus on sedimentary permafrost (Westermann et al, 2015;Rasmussen et al, 2018;Daanen et al, 2011;Hjort et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

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Widespread rock wall permafrost degradation in Greenland by the end of the 21st century under CMIP6 projections

Marcer,

Citterio,

Ingeman-Nielsen

2024

Preprint

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Permafrost in rock walls is a critical component of cold mountain environments, as it plays a crucial role in slope stability. Under warming climate, the interstitial ice in fractures and porosities thaws, compromising slope stability and inducing failures. Although in Greenland this phenomenon is known to have recently generated catastrophic landslides that have severely impacted the local community, there is currently no knowledge of its broad distribution nor of its response to climate projections. Here we model current and future rock wall permafrost extents in Greenland, using field data and CMIP6 projections under different scenarios. In the current climatic conditions, rock wall permafrost is widespread in the region, and 76% of the rockwalls are likely hosting permafrost. By the end of the 21st century, two dominant climatic trends—arctic amplification and Atlantic Meridional Overturning Circulation (AMOC) weakening—emerge, shaping the future of rock wall permafrost in this region. While arctic amplification drives virtually certain degradation in northern sectors for all scenarios investigated, AMOC weakening poses varied impacts in southern sectors, including stationary conditions (possible) or cooling (very unlikely). Central West Greenland, a region known for landslide propensity, is very likely to experience substantial permafrost degradation. Overall, our findings suggest very likely degradation of rock wall permafrost across Greenland. We emphasize the need for comprehensive monitoring and proactive protection of people and infrastructure from rising rockfall and landslide hazard, both in Greenland and across Arctic.

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Reply to the comment: Northern Hemisphere permafrost extent: Drylands, glaciers and sea floor

Cited by 7 publications

References 3 publications

Widespread deepening of the active layer in northern permafrost regions from 2003 to 2020

Widespread deepening of the active layer in northern permafrost regions from 2003 to 2020

The Net GHG Balance and Budget of the Permafrost Region (2000–2020) From Ecosystem Flux Upscaling

Widespread rock wall permafrost degradation in Greenland by the end of the 21st century under CMIP6 projections

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