Automated ocean front feature mapping using Sentinel-1 with examples from the Gulf Stream

ABSTRACT

This study assessed the ability of Sentinel-1 radial velocity (RVL) products to mark the position of ocean current front features, using the Gulf Stream (GS) as a case study. RVL-derived front features were compared to fronts derived from Multi-scale Ultra-high Resolution Sea Surface Temperature Analysis (MURSST) data. A ridge filter was used to find fronts in both the Sea Surface Temperature (SST) and RVL data, and the similarity between each pair of fronts was measured using the discrete Hausdorff Distance (HD) and Mean Hausdorff Distance (MHD). Front features were correctly identified in concurrent SST and RVL data pairs in 65% of cases. The automatic front extraction sometimes failed by misclassifying an eddy or similar ocean feature as the ocean current in either the RVL or SST image, and sometimes failed to extract the entire length of the front visible within the image. SST and RVL fronts were classified manually to determine the success rate of the automatic front extraction, and to exclude front extraction errors from further analysis. The results demonstrated that RVL products were effective at determining the location of ocean fronts where the angle between the front’s normal vector and the sensor’s azimuthal heading is less than ~ 40°. A mean HD of 25.5 km and a mean MHD of 10.8 km was calculated for all front pairs in the study area.

KEYWORDS:

• fronts (ocean)
• sea surface temperature
• edge detection
• classification

Acknowledgements

The authors would like to thank Céline Danilo and Gábor Bella for providing their RVL preprocessing code. Without their contributions this project would not have been possible. We would also like to acknowledge NOAA’s Environmental Research Division’s Data Access Program (ERDAAP) for providing the MURSST product, as well as the ESA Copernicus Open Access Hub for providing the Sentinel-1 Ocean products.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available in the GHRSST Level 4 MUR Global Foundation Sea Surface Temperature Analysis (v4.1) at https://doi.org/10.5067/GHGMR-4FJ04, reference number 10.5067/GHGMR-4FJ04. These data were derived from the following resources available in the public domain: https://coastwatch.pfeg.noaa.gov/erddap/griddap/jplMURSST41.html, https://podaac.jpl.nasa.gov/dataset/MUR-JPL-L4-GLOB-v4.1