Fast response of cold ice-rich permafrost in northeast Siberia to a warming climate

Abstract

The ice-and organic-rich permafrost of the northeast Siberian Arctic lowlands (NESAL) has been projected to remain stable beyond 2100, even under pessimistic climate warming scenarios. However, the numerical models used for these projections lack processes which induce widespread landscape change termed thermokarst, precluding realistic simulation of permafrost thaw in such ice-rich terrain. Here, we consider thermokarst-inducing processes in a numerical model and show that substantial permafrost degradation, involving widespread landscape collapse, is projected for the NESAL under strong warming (RCP8.5), while thawing is moderated by stabilizing feedbacks under moderate warming (RCP4.5). We estimate that by 2100 thaw-affected carbon could be up to threefold (twelve-fold) under RCP4.5 (RCP8.5), of what is projected if thermokarst-inducing processes are ignored. Our study provides progress towards robust assessments of the global permafrost carbon-climate feedback by Earth system models, and underlines the importance of mitigating climate change to limit its impacts on permafrost ecosystems.

Evaluating permafrost physics in the Coupled Model Intercomparison Project 6 (CMIP6) models and their sensitivity to climate change

“…In particular, excess ground ice which exists as ice lenses or wedges in permafrost soils is a key process that is not included in the current generation of CMIP models. Thawing of ice-rich permafrost ground will lead to landscape changes including subsidence, thaw slumps and active layer detachments and large-scale modification of the hydrological cycle (Liljedahl et al, 2016;Nitzbon et al, 2020). These ice-rich thermokarst landscapes are susceptible to abrupt changes and cover about 20 % of the northern permafrost region (Olefeldt et al, 2016).…”

Consequences of permafrost degradation for Arctic infrastructure – bridging the model gap between regional and engineering scales

“…This limits the ability to understand the magnitude of impacts under permafrost thaw. Thus, current model assessments are most likely far too conservative in their estimates of permafrost thaw impacts, which is underlined by observational evidence of strong permafrost degradation even under present day climate conditions not being captured by models (Farquharson et al, 2019;Nitzbon et al, 2020).…”

“…Comparable to the challenge of modelling microtopographic landscape features such as for polygonal tundra dynamics (Nitzbon et al, 2019;Nitzbon et al, 2020), a key limitation of modelling infrastructure in current LSMs is in their coarse https://doi.org/10.5194/tc-2020-192 Preprint. Discussion started: 16 September 2020 c Author(s) 2020.…”

“…For this purpose a case-specific tiling concept is needed to segregate infrastructure and tundra into individual structural units adapted to the scales of the modelling task. Examples of using a PTM (CryoGrid) in a tiling setting for describing diverse permafrost landscape dynamics can be found in Nitzbon et al (2019Nitzbon et al ( , 2020, where the authors capture micro-topography features to model dynamics of polygonal tundra degradation, and in (Langer et al, 2016), where accelerated thaw through talik formation induced by thermokarst lakes is simulated.…”

“…including subsurface water exchange (Nitzbon et al, 2019;Nitzbon et al, 2020). Further, the model has been evaluated under different climate conditions and for different permafrost landscape types such as peat plateaus and palsas .…”