Submitted as: model description paper 08 Jan 2021

Submitted as: model description paper | 08 Jan 2021

Review status: this preprint is currently under review for the journal GMD.

A Permafrost Implementation in the Simple Carbon-Climate Model Hector

Dawn L. Woodard1, Alexey N. Shiklomanov2, Ben Kravitz3,4, Corinne Hartin1, and Ben Bond-Lamberty1 Dawn L. Woodard et al.
  • 1Joint Global Change Research Institute, College Park, MD, 20740, USA
  • 2NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA
  • 3Department of Earth and Atmospheric Sciences, Indiana University, Bloomington, IN, 47405, USA
  • 4Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA

Abstract. Permafrost, soil that remains below 0 °C for two or more years, currently stores more than a fourth of global soil carbon. A warming climate makes this carbon increasingly vulnerable to decomposition and release into the atmosphere in the form of greenhouse gases. The resulting climate feedback can be estimated using Earth system models (ESMs), but the high complexity and computational cost of these models make it challenging to use them for estimating uncertainty, exploring novel scenarios, and coupling with other models. We have added a representation of permafrost to the simple, open-source global carbon-climate model Hector, calibrated to be consistent with both historical data and twenty-first century ESM projections of permafrost thaw. We include permafrost as a separate land carbon pool that becomes available for decomposition into both methane and carbon dioxide once thawed; the thaw rate is controlled by region-specific air temperature increases from a pre-industrial baseline. We found that by 2100 thawed permafrost carbon emissions increased Hector's atmospheric carbon dioxide concentration by 10–15 % and the atmospheric methane concentration by 10–20 %, depending on the future scenario. This resulted in around 0.5 °C of additional warming over the next century. The fraction of thawed permafrost carbon available for decomposition was the most significant parameter controlling the end-of-century temperature change and atmospheric carbon dioxide concentration in the model and became increasingly significant over even longer timescales. The addition of permafrost in Hector provides a basis for the exploration of a suite of science questions, as Hector can be cheaply run over a wide range of parameter values to explore uncertainty and easily coupled with integrated assessment models to explore the economic consequences of warming from this feedback.

Dawn L. Woodard et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2020-377', Anonymous Referee #1, 15 Feb 2021
  • RC2: 'Comment on gmd-2020-377', Anonymous Referee #2, 23 Feb 2021
  • CEC1: 'Comment on gmd-2020-377', Juan Antonio Añel, 03 Mar 2021
  • AC1: 'Comment on gmd-2020-377', Dawn Woodard, 02 Apr 2021

Dawn L. Woodard et al.

Dawn L. Woodard et al.


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Short summary
We have added a representation of the permafrost carbon feedback to the simple, open-source global carbon-climate model Hector and calibrated the results to be consistent with historical data and Earth system model (ESM) projections. Our results closely match previous work, estimating around 110 Pg C emitted from permafrost this century. This capability will be useful to explore uncertainties in this feedback and for coupling with integrated assessment models for policy and economic analysis.