Eddy Surface Characteristics and Vertical Structure in the Gulf of Mexico from Satellite Observations and Model Simulations

Abstract

The Gulf of Mexico exhibits strong circulation due to the Loop Current System, along with high mesoscale eddy activity. In order to investigate eddy characteristics, we apply an automatic eddy‐tracking algorithm to absolute dynamic topography maps and analyze the spatial distribution and evolution of eddy attributes including amplitude, radius, and eddy kinetic energy. The Loop Current region in the eastern Gulf of Mexico is an area of robust eddy generation for both cyclonic and anticyclonic eddies. Anticyclonic eddies were generally characterized by smaller amplitudes and larger radii when compared to their cyclonic counterparts. We also examine eddy surface properties including temperature and salinity anomalies as well as chlorophyll‐a concentration and observe how these properties vary between the eastern and western Gulf of Mexico. Persistent features such as the Loop Current System and coastal low‐salinity, highly biologically productive waters dominate eddy properties in the eastern side of the basin. We also apply the eddy‐tracking algorithm to a regional Hybrid Coordinate Ocean Model validated using Argo floats. We find that this model accurately reflects surface characteristics in the mesoscale eddy field as well as the mean vertical eddy structure and use it to extend our analysis of eddy properties with depth. We find that subsurface characteristics of density, salinity, temperature, and velocities vary greatly between eddies in the eastern and western Gulf of Mexico. Through composite analysis of both surface and subsurface eddy properties, we gain a more complete picture of the mechanisms behind the observable characteristics of these eddies.

Volume and Heat Transports by North Brazil Current Rings

“…For each eddy detected, the following properties are defined: (i) amplitude, which is the difference between the maximum (minimum) sea surface high (SSH) value and the averaged SSH over the edge pixels that define the outer perimeter of the eddy; (ii) radius of maximum velocity; and (iii) rotational velocity, which is the average of geostrophic speed over the radius of maximum velocity. This same methodology has been successful applied by other authors, such as Arur et al (2014) in their study of eddies in the Indian Ocean, Jufaili and Piontkovski (2020) for eddies in the western Arabian Sea, and Brokaw et al (2020) for eddies generated by the Loop Current in the eastern Gulf of Mexico. A newer version of mesoscale eddy trajectory atlas product META3.1 DT was made available recently and uses a different algorithm based on pyeddy-tracker to detect eddies.…”

Dispersal modeling of octopoda paralarvae in the Gulf of Mexico

“…The NCODA system assimilates available satellite altimeter data, satellite sea surface temperature, in situ sea surface temperature, and available in situ vertical temperature and salinity profiles from XBTs, Argo floats, and moored buoys, among others. The HYCOM GoM simulations have shown good consistency with observations and accurately reflect eddy characteristics in the GoM (Brokaw et al, 2020; Rosburg & Donohue, 2011; Rosburg et al, 2016). The domain of the model extends from 19 to 32°N and 98 to 76°W in such a way that also includes the Yucatan and Florida currents.…”

Eddy‐Induced Near‐Surface Chlorophyll Anomalies in the Subtropical Gyres: Biomass or Physiology?

“…Although the model captured the dominant feature of the θ ′ in the subtropical gyres, the pattern exhibits high spatial and temporal variability due to the discrete MLD data, which were estimated from over 3,300,000 in‐situ temperature and salinity profile observations delivered by the World Ocean Database (WOD) (Figure and Text ) (de Boyer Montégut et al., 2004). High resolution reanalysis data from the HYbrid Coordinate Ocean Model (HYCOM) have been documented to resolve eddy signals (Ajayi et al., 2020; Brokaw et al., 2020; He et al., 2017). We applied MLD data from the HYCOM and reran the model for a refined result.…”

“…10.1029/2020GL091975 5 of 10 (WOD) (Figure S1 and Text S3) (de Boyer Montégut et al, 2004). High resolution reanalysis data from the HYbrid Coordinate Ocean Model (HYCOM) have been documented to resolve eddy signals (Ajayi et al, 2020;Brokaw et al, 2020;He et al, 2017). We applied MLD data from the HYCOM and reran the model for a refined result.…”