permafrost feedbacks before and after 2100€¦ · permafrost feedbacks before and after 2100 c. d....
TRANSCRIPT
![Page 1: Permafrost feedbacks before and after 2100€¦ · Permafrost feedbacks before and after 2100 C. D. Koven, D. M. Lawrence June 20, 2017](https://reader034.vdocuments.mx/reader034/viewer/2022050113/5f4a742b727e04021019b5a1/html5/thumbnails/1.jpg)
Permafrost feedbacks before and after 2100
C. D. Koven, D. M. LawrenceJune 20, 2017
![Page 2: Permafrost feedbacks before and after 2100€¦ · Permafrost feedbacks before and after 2100 C. D. Koven, D. M. Lawrence June 20, 2017](https://reader034.vdocuments.mx/reader034/viewer/2022050113/5f4a742b727e04021019b5a1/html5/thumbnails/2.jpg)
IPCC‐AR5 (Ciais et al., 2013)
Most of the carbon in the terrestrial system is frozen in high latitude soils
![Page 3: Permafrost feedbacks before and after 2100€¦ · Permafrost feedbacks before and after 2100 C. D. Koven, D. M. Lawrence June 20, 2017](https://reader034.vdocuments.mx/reader034/viewer/2022050113/5f4a742b727e04021019b5a1/html5/thumbnails/3.jpg)
CLM4.5 includes a representation of permafrost effects on carbon storage, and thus allows exploration of
feedbacks from permafrost
Observations
Precipitation (mm/yr)
![Page 4: Permafrost feedbacks before and after 2100€¦ · Permafrost feedbacks before and after 2100 C. D. Koven, D. M. Lawrence June 20, 2017](https://reader034.vdocuments.mx/reader034/viewer/2022050113/5f4a742b727e04021019b5a1/html5/thumbnails/4.jpg)
Climate models project large losses of permafrost area with warming in the
21st century
Koven et al., (2013)
Slater and Lawrence, (2013)
![Page 5: Permafrost feedbacks before and after 2100€¦ · Permafrost feedbacks before and after 2100 C. D. Koven, D. M. Lawrence June 20, 2017](https://reader034.vdocuments.mx/reader034/viewer/2022050113/5f4a742b727e04021019b5a1/html5/thumbnails/5.jpg)
CLM4.5 shows large losses of carbon; sensitive to assumptions about the cycling of carbon at depth
• With decomposable deep soil organic matter, soil C losses dominate and lead to a large positive feedback from the permafrost region
• Inclusion of nitrogen cycle suggests that plants may not effectively use extra nitrogen released by decomposing deep soils to mitigate C losses
Koven et al., PNAS, 2015
![Page 6: Permafrost feedbacks before and after 2100€¦ · Permafrost feedbacks before and after 2100 C. D. Koven, D. M. Lawrence June 20, 2017](https://reader034.vdocuments.mx/reader034/viewer/2022050113/5f4a742b727e04021019b5a1/html5/thumbnails/6.jpg)
Feedback terms: carbon‐concentration(β) and carbon‐climate(γ) from permafrost region
Global CMIP5 values: Arora et al., 2013 Regional CLM4.5 values for permafrost
γPF=.04‐.11 W m‐2 K‐1.08‐.14 W m‐2 K‐1
Threshold,Negative curvature
![Page 7: Permafrost feedbacks before and after 2100€¦ · Permafrost feedbacks before and after 2100 C. D. Koven, D. M. Lawrence June 20, 2017](https://reader034.vdocuments.mx/reader034/viewer/2022050113/5f4a742b727e04021019b5a1/html5/thumbnails/7.jpg)
Long‐term carbon‐climate feedback in CLM4.5
Carbon‐climate feedback from permafrost region
Carbon‐climate feedback from entire terrestrial system
Difference between blue and red curves due to question of how to compute feedback — i.e. magnitude of synergistic effects between CO2 and climate change.
![Page 8: Permafrost feedbacks before and after 2100€¦ · Permafrost feedbacks before and after 2100 C. D. Koven, D. M. Lawrence June 20, 2017](https://reader034.vdocuments.mx/reader034/viewer/2022050113/5f4a742b727e04021019b5a1/html5/thumbnails/8.jpg)
Projected soil C emissions follow the retreating permafrost boundary and persist long after
permafrost has thawed
Koven et al., PNAS, 2015
![Page 9: Permafrost feedbacks before and after 2100€¦ · Permafrost feedbacks before and after 2100 C. D. Koven, D. M. Lawrence June 20, 2017](https://reader034.vdocuments.mx/reader034/viewer/2022050113/5f4a742b727e04021019b5a1/html5/thumbnails/9.jpg)
Carbon losses from permafrost may be large; similar magnitude to, but slower than, carbon responses of tropical forests
Koven et al., PNAS, 2015
![Page 10: Permafrost feedbacks before and after 2100€¦ · Permafrost feedbacks before and after 2100 C. D. Koven, D. M. Lawrence June 20, 2017](https://reader034.vdocuments.mx/reader034/viewer/2022050113/5f4a742b727e04021019b5a1/html5/thumbnails/10.jpg)
Summary
• Permafrost carbon‐climate feedbacks strong contributor to overall terrestrial feedback in CLM4.5
• Delayed feedback relative to tropical/temperate dynamics; threshold at around 4C global temperature change