Permafrost in a warming world

Permafrost thaw is directly governed by the thermal characteristics of the frozen ground. This Review outlines the status of and mechanisms influencing the thermal state of permafrost, revealing widespread increases in permafrost temperatures and active-layer thicknesses.

Lakes and drained lake basins are the most prominent periglacial landforms in northern high-latitude lowland regions, and their dynamics impact permafrost, ecosystem and biogeochemical processes. This Review discusses the influence and consequences of climate change on lake systems.

Arctic coasts are increasingly affected by erosion and flooding, owing to decreasing sea ice, thawing permafrost and rising sea levels. This Review examines the changes in Arctic coastal morphodynamics and discusses the broader impacts on Arctic systems.

Siberian Arctic permafrost contains vast stores of carbon, the fate of which is dependent on the climate. Here the authors use models of future scenarios to show that under the direst climate changes up to 2/3 of the stored organic carbon could thaw.

A reconstruction of permafrost dynamics using speleothems from a Siberian cave indicates that Siberian permafrost is robust to warming when Arctic sea ice is present, but vulnerable when it is absent.

Climate change strongly impacts regions in high latitudes and altitudes that store high amounts of carbon in yet frozen ground. Here the authors show that the consequence of these changes is global warming of permafrost at depths greater than 10 m in the Northern Hemisphere, in mountains, and in Antarctica.

Large stores of carbon could be released to the atmosphere from Arctic warming, driving permafrost thaw. This Review examines the processes that impact Arctic permafrost carbon emissions, how they might change in the future and ways to monitor and predict these changes.

Permafrost-affected soils are an unappreciated but potentially substantial source of nitrous oxide, a powerful greenhouse gas. This Review outlines the global importance of nitrous oxide dynamics in permafrost-affected soils, examines what drives nitrous oxide fluxes and discusses the impact of climate change on these greenhouse gas emissions.

Thawing permafrost in the Arctic may release microorganisms, chemicals and nuclear waste that have been stored in frozen ground and by cold temperatures. This Review discusses the current state of potential hazards and their risks under warming to identify prospective threats to the Arctic.

The sudden collapse of thawing soils in the Arctic might double the warming from greenhouse gases released from tundra, warn Merritt R. Turetsky and colleagues.

Soil radiocarbon dating reveals that combusted ‘legacy carbon’—soil carbon that escaped burning during previous fires—could shift the carbon balance of boreal ecosystems, resulting in a positive climate feedback.

Future changes in non-growing season conditions, particularly irradiance and temperature, will enhance carbon emissions from a northern peatland, according to projections with a data-driven machine learning model.

Analyses of inventory models under two climate change projection scenarios suggest that carbon emissions from abrupt thaw of permafrost through ground collapse, erosion and landslides could contribute significantly to the overall permafrost carbon balance.

High-elevation rivers in permafrost of the East Qinghai–Tibet Plateau are hotspots of methane emissions, according to measurements of methane fluxes in the region.

Permafrost locks away the largest reservoir of mercury on the planet, but climate warming threatens to thaw these systems. Here the authors use models to show that unconstrained fossil fuel burning will dramatically increase the amount of mercury released into future ecosystems.

Iron minerals trap carbon in permafrost, preventing microbial degradation and release to the atmosphere as CO₂, but the stability of this carbon as permafrost thaws is unclear. Here the authors use nanoscale analyses to show that thaw conditions stimulate Fe-reducing bacteria that trigger carbon release.

Biological productivity and carbon dynamics in Arctic ecosystems started to change prior to human-induced warming of the region, according to an investigation of coupled carbon–nitrogen cycle dynamics using stable isotope analyses of lake sediments.

Winter warming in the Arctic will increase the CO₂ flux from soils. A pan-Arctic analysis shows a current loss of 1,662 TgC per year over the winter, exceeding estimated carbon uptake in the growing season; projections suggest a 17% increase under RCP 4.5 and a 41% increase under RCP 8.5 by 2100.

In this study, the authors show that water flowing through thawed soils below the tundra surface (supra-permafrost groundwater) can be a major source of dissolved organic matter (DOM) to Arctic coastal waters during the summer. This DOM contains leachates from old soil carbon stocks, including potential contributions from thawing permafrost.

Greening and vegetation community shifts have been observed across Arctic environments. This Review examines these changes and their impact on underlying permafrost.

Microbial life can thrive in extreme environments such as terrestrial hot springs and deep sea hydrothermal vents, glaciers and permafrost, hypersaline habitats, acid mine drainage and the subsurface. In this Review, Shu and Huang explore the diversity, functions and evolution of bacteria and archaea inhabiting Earth’s major extreme environments.

In this Review, Jansson and Hofmockel explore the impacts of climate change on soil microorganisms in different climate-sensitive soil ecosystems and the potential ways that soil microorganisms can be harnessed to help mitigate the negative consequences of climate change.

Siberian mammoth genomes from the Early and Middle Pleistocene subepochs reveal adaptive changes and a key hybridization event, highlighting the value of deep-time palaeogenomics for studies of speciation and long-term evolutionary trends.

‘The timing and ecological dynamics of extinction in the late Pleistocene are not well understood. Here, the authors use sediment ancient DNA from permafrost cores to reconstruct the paleoecology of the central Yukon, finding a substantial turnover in ecosystem composition between 13,500-10,000 years BP and persistence of some species past their supposed extinctions.’

Using plant community trait composition data and microclimate and soil chemistry data from four distinct tundra regions, the authors demonstrate strong, consistent trait–environment relationships across Arctic and Antarctic regions.

Models overestimate Arctic methane emissions compared to observations. Incorporating microbial dynamics into biogeochemistry models helps reconcile this discrepancy; high-affinity methanotrophs are an important part of the Arctic methane budget and double previous estimates of methane sinks.

Plant roots in thawing permafrost soils act to enhance microbial decomposition and the loss of soil organic carbon, according to an analysis of observational data and a rhizosphere priming model.

Satellites provide clear evidence of greening trends in the Arctic, but high-resolution pan-Arctic quantification of these trends is lacking. Here the authors analyse high-resolution Landsat data to show widespread greening in the Arctic, and find that greening trends are linked to summer warming overall but not always locally.

Permafrost thaw and degradation threaten circumpolar infrastructure. This Review documents observed and projected infrastructure impacts, as well as the mitigation strategies available to minimize them.

Permafrost is thawing with rising temperatures. More work and collaboration are needed to understand the impacts of this thaw, and how to mitigate them.

Underground smouldering fires resurfaced early in 2020, contributing to the unprecedented wildfires that tore through the Arctic this spring and summer. An international effort is needed to manage a changing fire regime in the vulnerable Arctic.

Changes in lightning activity are uncertain under climate change. The authors project that summer lightning in the Arctic is likely to more than double by the end of the century, with implications for lightning-strike tundra wildfires and associated carbon release from permafrost.

Nonlinear transitions in permafrost carbon feedback and surface albedo feedback have largely been excluded from climate policy studies. Here the authors modelled the dynamics of the two nonlinear feedbacks and the associated uncertainty, and found an important contribution to warming which leads to additional economic losses from climate change.

Permafrost thaw due to rising temperatures will impact soil hydrology in the Arctic. Abrupt changes in soil moisture and land–atmosphere processes may alter the bearing capacity of soil and increase susceptibility to wildfires, with consequences for adapting engineering systems in the region.