title: How well-connected is the surface of the global ocean?
abstract: The Ekman dynamics of the ocean surface circulation is known to contain attracting regions such as the great oceanic gyres and the associated garbage patches. Less well-known are the extents of the basins of attractions of these regions and how strongly attracting they are. Understanding the shape and extent of the basins of attraction sheds light on the question of the strength of connectivity of different regions of the ocean, which helps in understanding the flow of buoyant material like plastic litter. Using short flow time trajectory data from a global ocean model, we create a Markov chain model of the surface ocean dynamics. The surface ocean is not a conservative dynamical system as water in the ocean follows three-dimensional pathways, with upwelling and downwelling in certain regions. Using our Markov chain model, we easily compute net surface upwelling and downwelling, and verify that it matches observed patterns of upwelling and downwelling in the real ocean. We analyze the Markov chain to determine multiple attracting regions. Finally, using an eigenvector approach, we (i) identify the five major ocean garbage patches, (ii) partition the ocean into basins of attraction for each of the garbage patches, and (iii) partition the ocean into regions that demonstrate transient dynamics modulo the attracting garbage patches.
authors.affiliation: School of Mathematics and Statistics, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Gary
authors.initials: G
authors.lastname: Froyland
authors.affiliation: School of Mathematics and Statistics, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Robyn M
authors.initials: RM
authors.lastname: Stuart
authors.affiliation: Climate Change Research Centre and ARC Centre of Excellence for Climate System Science, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Erik
authors.initials: E
authors.lastname: van Sebille