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TitleEvaluating permafrost physics in the Coupled Model Intercomparison Project 6 (CMIP6) models and their sensitivity to climate change
AuthorBurke, E J; Zhang, YORCID logo; Krinner, G
SourceThe Cryosphere vol. 14, issue 9, 2020 p. 3155-3174, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20200508
PublisherCopernicus GmbH
Mediapaper; on-line; digital
File formatpdf; html
Subjectssurficial geology/geomorphology; soils science; environmental geology; Nature and Environment; Science and Technology; permafrost; climate effects; climate, arctic; temperature; modelling; models; soil profiles; terrain sensitivity; Coupled Model Intercomparison Project 6 (CMIP6); Climate change; permafrost thaw
Illustrationsschematic cross-sections; tables; plots; bar graphs; sketch maps; models
ProgramCanada Centre for Remote Sensing Optical methods and applications
Released2020 09 16
AbstractPermafrost is a ubiquitous phenomenon in the Arctic. Its future evolution is likely to control changes in northern high-latitude hydrology and biogeochemistry. Here we evaluate the permafrost dynamics in the global models participating in the Coupled Model Intercomparison Project (present generation - CMIP6; previous generation - CMIP5) along with the sensitivity of permafrost to climate change. Whilst the northern high-latitude air temperatures are relatively well simulated by the climate models, they do introduce a bias into any subsequent model estimate of permafrost. Therefore evaluation metrics are defined in relation to the air temperature. This paper shows that the climate, snow and permafrost physics of the CMIP6 multi-model ensemble is very similar to that of the CMIP5 multi-model ensemble. The main differences are that a small number of models have demonstrably better snow insulation in CMIP6 than in CMIP5 and a small number have a deeper soil profile. These changes lead to a small overall improvement in the representation of the permafrost extent. There is little improvement in the simulation of maximum summer thaw depth between CMIP5 and CMIP6. We suggest that more models should include a better-resolved and deeper soil profile as a first step towards addressing this. We use the annual mean thawed volume of the top 2m of the soil defined from the model soil profiles for the permafrost region to quantify changes in permafrost dynamics. The CMIP6 models project that the annual mean frozen volume in the top 2m of the soil could decrease by 10 %-40%C1 of global mean surface air temperature increase.

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