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oai:cora.ucc.ie:10468/150162023-09-21T02:03:26Zcom_10468_388com_10468_5com_10468_88com_10468_1col_10468_389col_10468_859col_10468_8983

Mulchrone, Kieran F. Wieczorek, Sebastian O'Sullivan, Eoin ATSR Ltd. 2023-09-20T14:52:20Z 2023-09-20T14:52:20Z 2023 2023 Surface wildfires are generally believed to be the cause of so-called Zombie fires observed in peatlands, that disappear from the surface, smoulder underground during the winter, and ''come back to life" in the spring. Here, we propose rate-induced tipping (R-tipping) to a subsurface hot metastable state in bioactive peat soils as a main cause of Zombie fires. Our hypothesis is based on a conceptual soil-carbon model subjected to realistic changes in weather and climate patterns, including global warming scenarios and summer heatwaves. Mathematically speaking, R-tipping to the hot metastable state is a nonautonomous instability, due to crossing an elusive quasithreshold, in a multiple-timescale dynamical system. The instability is {\em reversible}, in the sense that the system eventually returns to its base state. To explain this instability, we provide a framework that combines a special compactification technique with concepts from geometric singular perturbation theory. This framework allows us to reduce a reversible R-tipping problem due to crossing a quasithreshold to a heteroclinic orbit problem in a singular limit. Thus, we identify generic cases of such R-tipping via: (i) unfolding of a codimension-two heteroclinic folded saddle-node type-I singularity for global warming, and (ii) analysis of a codimension-one saddle-to-saddle hetroclinic orbit for summer heatwaves, which in turn reveal new types of excitability quasithresholds. Not peer reviewed Accepted Version application/pdf O'Sullivan, E. G. 2023. Rate-induced tipping to metastable Zombie fires. PhD Thesis, University College Cork. 137 https://hdl.handle.net/10468/15016 en University College Cork © 2023, Eoin O'Sullivan. https://creativecommons.org/licenses/by/4.0/ Applied mathematics Zombie fires Rate-induced tipping Canards Geometric singular perturbation theory Rate-induced tipping to metastable Zombie fires Doctoral thesis Doctoral PhD - Doctor of Philosophyinfo:eu-repo/semantics/openAccess