Several quantities computed by Lagrangian methods are being used to qualify local properties of ocean flow at different locations: rotation, stretching, convergence or divergence, shear, presence of flow barriers, etc., providing useful tools to characterize transport. Going beyond local characterization, ocean connectivity properties have also been addressed with Lagrangian methods, for example by using Lagrangian flow networks.  The presence of ‘bottlenecks’ or congestion areas (i.e. regions that should be crossed by water traveling between many distant origins and destinations) is conveniently identified by network-based measures such as the betweenness centrality. Here we combine the connectivity ideas with local transport properties to define a ‘Lagrangian betweenness’ [1], able to identify and to quantify the presence of bottlenecks in regions of the flow. We illustrate the use and meaning of the Lagrangian betweenness by identifying bottlenecks in ocean surface flows in the Adriatic Sea and in the Kerguelen region in the Southern Ocean. Also, by analyzing plankton abundance data from the Kuroshio region in the Pacific Ocean, we find significant spatial correlations between measures of biological diversity and betweenness, suggesting that ocean bottlenecks act as ecological hot spots.  [1] E. Ser-Giacomi, A. Baudena, V. Rossi, M. Follows, S. Clayton, R. Vasile, C. Lopez, E. Hernandez-Garcia (2021), Lagrangian betweenness as a measure of bottlenecks in dynamical systems with oceanographic examples, Nature Communications 12, 4935.

Primary Presenter: Emilio Hernandez-Garcia, IFISC (CSIC-UIB) (emilio@ifisc.uib-csic.es)

Authors:

Enrico Ser-Giacomi, Department of Earth, Atmospheric and Planetary Sciences, MIT, Cambridge, USA, and IFISC (CSIC-UIB), Instituto de Fisica Interdisciplinar y Sistemas Complejos, Palma de Mallorca, Spain  (enrico.sergiacomi@gmail.com)

Alberto Baudena, Sorbonne Universite, Institut de la Mer de Villefranche-sur-Mer, France  (alberto.baudena@gmail.com)

Vincent Rossi, Mediterranean Institute of Oceanography (UM110, UMR 7294), Marseille, France  (vincent.rossi@mio.osupytheas.fr)

Mick Follows, Department of Earth, Atmospheric and Planetary Sciences, MIT, Cambridge, USA  (mick@ocean.mit.edu)

Sophie Clayton, Old Dominion University, Norfolk, VA, USA  (sclayton@odu.edu)

Ruggero Vasile, UP Transfer GmbH, and GFZ German Research Centre for Geosciences, Potsdam, Germany  (ruleva1983@gmail.com)

Cristobal Lopez, IFISC (CSIC-UIB), Instituto de Fisica Interdisciplinar y Sistemas Complejos, Palma de Mallorca, Spain  (clopez@ifisc.uib-csic.es)

Emilio Hernandez-Garcia, IFISC (CSIC-UIB), Instituto de Fisica Interdisciplinar y Sistemas Complejos, Palma de Mallorca, Spain  (emilio@ifisc.uib-csic.es)