Abstract

Fronts, meeting points with water masses having different properties, are common occurrences in the ocean and cover a wide range of both temporal and spatial scales. Coastal areas such as the Hauraki Gulf (Aotearoa New Zealand) are characterised strong frontal heterogeneity that is challenging to monitor. Here, we combine fine resolution satellite imaging with a front detection algorithm optimised for the region to investigate the spatio-temporal variability of ocean color fronts. We adapted the Belkin and O’Reilly Algorithm (BOA) to remove the noise typically associated with Ocean and Land Colour Instrument (OLCI) images. By compiling high resolution detection over the 2016-2022 period, we show the distribution of frontal features varied across seasons, wind direction, and ENSO phase. Locations of fronts oscillated seasonally from the inner to the outer gulf, going far from land between winter and spring, reversing between spring and autumn. Similarly, El Niño periods correspond to fronts closer to the coast, while La Niña periods correspond to locations further offshore. These patterns relate to the predominant wind direction in the region of interest: El Niño is dominated by westerlies while La Niña is linked with prevalent easterlies. This flexible approach supports the study of the spatio-temporal variability of fronts and provides a near-real time tool to monitor change in coastal regions.

Conference link: ASLO.

Presentation link: Access.