Spectral early-warning signals for sudden changes in time-dependent flow patterns

• Published in: Fluids
• Main Authors: Ndour, M, Padberg-Gehle, K, Rasmussen, M
• Other Authors: Commission of the European Communities
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI 2021
• Subjects: Antarctic; The Antarctic; Antarc*
• Online Access: http://hdl.handle.net/10044/1/87261; https://doi.org/10.3390/fluids6020049

Lagrangian coherent sets are known to crucially determine transport and mixing processes in non-autonomous flows. Prominent examples include vortices and jets in geophysical fluid flows. Coherent sets can be identified computationally by a probabilistic transfer-operator-based approach within a set-oriented numerical framework. Here, we study sudden changes in flow patterns that correspond to bifurcations of coherent sets. Significant changes in the spectral properties of a numerical transfer operator are heuristically related to critical events in the phase space of a time-dependent system. The transfer operator approach is applied to different example systems of increasing complexity. In particular, we study the 2002 splitting event of the Antarctic polar vortex.