A Discontinuous ODE Model of the Glacial Cycles with Diffusive Heat Transport

• Published in: Mathematics
• Main Authors: James Walsh, Esther Widiasih
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2020
• Subjects: differential equation; invariant manifold; limit cycle; differential inclusion; Mathematics; QA1-939; Ice Sheet
• Online Access: https://doi.org/10.3390/math8030316; https://doaj.org/article/0d9d3f598580493f93f255c8b74847c4

We present a new discontinuous ordinary differential equation (ODE) model of the glacial cycles. Model trajectories flip from a glacial to an interglacial state, and vice versa, via a switching mechanism motivated by ice sheet mass balance principles. Filippov’s theory of differential inclusions is used to analyze the system, which can be viewed as a nonsmooth geometric singular perturbation problem. We prove the existence of a unique limit cycle, corresponding to the Earth’s glacial cycles. The diffusive heat transport component of the model is ideally suited for investigating the competing temperature gradient and transport efficiency feedbacks, each associated with ice-albedo feedback. It is the interplay of these feedbacks that determines the maximal extent of the ice sheet. In the nonautonomous setting, model glacial cycles persist when subjected to external forcing brought on by changes in Earth’s orbital parameters over geologic time. The system also exhibits various bifurcation scenarios as key parameters vary.