Abstract's details
Blending AIS data and altimetric measurements to estimate sea surface currents in the Gulf of Mexico
CoAuthors
Event: 2022 Ocean Surface Topography Science Team Meeting
Session: Science III: Mesoscale and sub-mesoscale oceanography
Presentation type: Type Oral
Contribution: PDF file
Abstract:
The maritime traffic around the Loop current of the Gulf of Mexico is large enough to help retrieving the oceanic surface current. Using Automatic Identification System (AIS) data streams for the period 2019-2020, a distance-weighted least-squares approach [Le Goff et al 2021] is used to estimate ocean surface currents at a depth corresponding to the mean draught of the commercial vessels (about 7m).
The calculated gridded data product has spatial resolution of 0.125⁰ × 0.125⁰ and daily temporal resolution. These estimations provide a valuable resource to investigate the ageostrophic processes that altimeter-based data are not sufficient to resolve. However, the limited coverage of the AIS Data (limited to the main maritime routes), prevents studies from reaching regional basins and thus limits potential applications of the collected data at larger scales where altimetry data is sufficient. As such, synergy between AIS-derived sea surface currents and altimetry data needs to be considered to increase the accuracy of sea surface currents in the Gulf of Mexico.
The merging is done through the Multiscale Inversion for Ocean Surface Topography (MIOST) [Ubelmann et al., 2020] variational tool to retrieve both geostrophic and ageostrophic current. This tool allows the decomposition of the signal into different components representing different time and space scales (i.e., mesoscale to large-scale) and different physical signals (i.e., geostrophic, internal waves, near-inertial oscillations, Ekman current…).
The resulting improved ocean surface current estimates will be compared to the intensity of surface currents estimated from the AOML drifters. Comparisons with high-resolution Sea Surface Temperature (SST) images from infrared instruments will be focused on the eddy separation events for the Gulf of Mexico loop current and on the associated eddy paths. Identification of warm rings with an eddy tracking algorithm (e.g., AMEDA [Le Vu et al 2018]) will allow the determination of the characteristics and life cycle of these eddies.
[Le Goff et al 2021] : Le Goff, C., Boussidi, B., Mironov, A., Guichoux, Y., Zhen, Y., Tandeo, P., et al. (2021). Monitoring the greater Agulhas Current with AIS data information. Journal of Geophysical Research: Oceans, 126, e2021JC017228. https://doi.org/10.1029/2021JC017228
[Ubelmann et al 2021]: Ubelmann, C., Dibarboure, G., Gaultier, L., Ponte, A., Ardhuin, F., Ballarotta, M., & Faugère, Y. (2021). Reconstructing ocean surface current combining altimetry and future spaceborne Doppler data. Journal of Geophysical Research: Oceans, 126, e2020JC016560. https://doi.org/10.1029/2020JC016560
[Le Vu et al 2018]: Le Vu, B., Stegner, A., & Arsouze, T. (2018). Angular Momentum Eddy Detection and tracking Algorithm (AMEDA) and its application to coastal eddy formation. Journal of Atmospheric and Oceanic Technology, 35(4), 739-762.
The calculated gridded data product has spatial resolution of 0.125⁰ × 0.125⁰ and daily temporal resolution. These estimations provide a valuable resource to investigate the ageostrophic processes that altimeter-based data are not sufficient to resolve. However, the limited coverage of the AIS Data (limited to the main maritime routes), prevents studies from reaching regional basins and thus limits potential applications of the collected data at larger scales where altimetry data is sufficient. As such, synergy between AIS-derived sea surface currents and altimetry data needs to be considered to increase the accuracy of sea surface currents in the Gulf of Mexico.
The merging is done through the Multiscale Inversion for Ocean Surface Topography (MIOST) [Ubelmann et al., 2020] variational tool to retrieve both geostrophic and ageostrophic current. This tool allows the decomposition of the signal into different components representing different time and space scales (i.e., mesoscale to large-scale) and different physical signals (i.e., geostrophic, internal waves, near-inertial oscillations, Ekman current…).
The resulting improved ocean surface current estimates will be compared to the intensity of surface currents estimated from the AOML drifters. Comparisons with high-resolution Sea Surface Temperature (SST) images from infrared instruments will be focused on the eddy separation events for the Gulf of Mexico loop current and on the associated eddy paths. Identification of warm rings with an eddy tracking algorithm (e.g., AMEDA [Le Vu et al 2018]) will allow the determination of the characteristics and life cycle of these eddies.
[Le Goff et al 2021] : Le Goff, C., Boussidi, B., Mironov, A., Guichoux, Y., Zhen, Y., Tandeo, P., et al. (2021). Monitoring the greater Agulhas Current with AIS data information. Journal of Geophysical Research: Oceans, 126, e2021JC017228. https://doi.org/10.1029/2021JC017228
[Ubelmann et al 2021]: Ubelmann, C., Dibarboure, G., Gaultier, L., Ponte, A., Ardhuin, F., Ballarotta, M., & Faugère, Y. (2021). Reconstructing ocean surface current combining altimetry and future spaceborne Doppler data. Journal of Geophysical Research: Oceans, 126, e2020JC016560. https://doi.org/10.1029/2020JC016560
[Le Vu et al 2018]: Le Vu, B., Stegner, A., & Arsouze, T. (2018). Angular Momentum Eddy Detection and tracking Algorithm (AMEDA) and its application to coastal eddy formation. Journal of Atmospheric and Oceanic Technology, 35(4), 739-762.