  Coherent oceanic mesoscale structures, especially the non-filamenting cores
of oceanic eddies, have gained a lot of attention in recent years. These
Lagrangian structures are considered to play a significant role in oceanic
transport processes which, in turn, impact marine life, weather and potentially
even the climate itself. Answering questions regarding these phenomena requires
robust tools for the detection and identification of these structures. In this
article, we use transfer operator ideas to develop a novel method for the
identification of weakly-mixing coherent volumes in oceanic velocity field data
sets. Unlike other methods, the approach focuses on maximizing consistency over
longer time periods. We employ a time-centralized transfer operator approach
with practical modifications to identify potential structures in predetermined
domains and couple adjacent time steps to decide how to conduct the final
partitioning. The analysis pipeline includes plausibility checks that give
further insights into the stability and coherence of the inferred structure.
The presented method is able to find changing masses of maximal coherence in
stationary and non-stationary toy models and yields good results when applied
to field data.
