Evidence for fire in the Pliocene Arctic in response to amplified temperature

• Published in: Climate of the Past
• Main Authors: T. L. Fletcher, L. Warden, J. S. Sinninghe Damsté, K. J. Brown, N. Rybczynski, J. C. Gosse, A. P. Ballantyne
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2019
• Subjects: Environmental pollution; TD172-193.5; Environmental protection; TD169-171.8; Environmental sciences; GE1-350; Arctic; Ellesmere Island; Canada
• Online Access: https://doi.org/10.5194/cp-15-1063-2019; https://doaj.org/article/3c33fa5866214f5fad612fe9beb240b1

The mid-Pliocene is a valuable time interval for investigating equilibrium climate at current atmospheric CO 2 concentrations because atmospheric CO 2 concentrations are thought to have been comparable to the current day and yet the climate and distribution of ecosystems were quite different. One intriguing, but not fully understood, feature of the early to mid-Pliocene climate is the amplified Arctic temperature response and its impact on Arctic ecosystems. Only the most recent models appear to correctly estimate the degree of warming in the Pliocene Arctic and validation of the currently proposed feedbacks is limited by scarce terrestrial records of climate and environment. Here we reconstruct the summer temperature and fire regime from a subfossil fen-peat deposit on west–central Ellesmere Island, Canada, that has been chronologically constrained using cosmogenic nuclide burial dating to <math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">3.9</mn><mo>+</mo><mn mathvariant="normal">1.5</mn><mo>/</mo><mo>-</mo><mn mathvariant="normal">0.5</mn></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="76pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="f5acdab910ad7938adde8738ff1bd251"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cp-15-1063-2019-ie00001.svg" width="76pt" height="14pt" src="cp-15-1063-2019-ie00001.png"/></svg:svg> Ma. The estimate for average mean summer temperature is 15.4±0.8 ∘ C using specific bacterial membrane lipids, i.e., branched glycerol dialkyl glycerol tetraethers. This is above the proposed threshold that predicts a substantial increase in wildfire in the modern high latitudes. Macro-charcoal was present in all samples from this Pliocene section with notably higher charcoal concentration in the upper part of the sequence. This change in ...