Quantifying connectivity in the coastal ocean with application to the Southern California Bight

Abstract

The quantification of coastal connectivity is important for a wide range of real‐world applications ranging from assessment of pollutant risk to nearshore fisheries management. For these purposes, coastal connectivity can be defined as the probability that water parcels from one location have advected to another site over a given time interval. Here we demonstrate how to quantify connectivity using Lagrangian probability‐density functions (PDFs) based on numerical solutions of the coastal circulation of the Southern California Bight (SCB). Ensemble mean dispersal patterns from a single release site show strong dependencies on particle‐release location, season, and year, reflecting annual and interannual circulation patterns in the SCB. Mean connectivity patterns are heterogeneous for the advection time of 30 days or less, due to local circulation patterns, and they become more homogeneous for longer advection times. However, connectivity patterns for a single realization are highly variable because of intrinsic eddy‐driven transport and synoptic wind‐forcing variability. In the long term, mainland sites are good sources while both Northern and Southern Channel Islands are poor sources, although they receive substantial fluxes of water parcels from the mainland. The predicted connectivity gives useful information to ecological and other applications for the SCB (e.g., designing marine protected areas and predicting the impact of a pollution event) and demonstrates how high‐resolution numerical solutions of coastal ocean circulations can be used to quantify nearshore connectivity.