Subsurface Fine‐Scale Patterns in an Anticyclonic Eddy Off Cap‐Vert Peninsula Observed From Glider Measurements

Abstract

Glider measurements acquired along four transects between Cap-Vert Peninsula and the Cape Verde archipelago in the eastern tropical North Atlantic during March-April 2014 were used to investigate fine-scale stirring in an anticyclonic eddy. The anticyclone was formed near 12°N off the continental shelf and propagated northwest toward the Cape Verde islands. At depth, between 100 and -400 m, the isolated anticyclone core contained relatively oxygenated, low-salinity South Atlantic Central Water, while the surrounding water masses were saltier and poorly oxygenated. The dynamical and thermohaline subsurface environment favored the generation of fine-scale horizontal and vertical temperature and salinity structures in and around the core of the anticyclone. These features exhibited horizontal scales of O(10-30 km) relatively small with respect to the eddy radius of O(150 km). The vertical scales of O(5-100 m) were associated to density-compensated gradient. Spectra of salinity and oxygen along isopycnals revealed a slope of around k À2 in the 10-to 100-km horizontal scale range. Further analyses suggest that the fine-scale structures are likely related to tracer stirring processes. Such mesoscale anticyclonic eddies and the embedded fine-scale tracers in and around them could play a major role in the transport of South Atlantic Central Water masses and ventilation of the North Atlantic Oxygen Minimum Zone.Ubiquitous surface and subsurface cyclonic and anticyclonic eddies of various origin and nature act as a major transport agent between the coastal waters and the open ocean (e.g., Chelton et al.

Global Perspectives on Observing Ocean Boundary Current Systems

“…Ship-based hydrographic and biogeochemical sampling has taken place twice per year since 2006 at the latitude of the Canary Archipelago as part of the RAPROCAN program (Figure 9), which aims to monitor the Canary Current and maintain the ESTOC mooring. Gliders have periodically surveyed between the African coast and the Cape Verde Islands (Figure 9; Karstensen et al, 2017;Kolodziejczyk et al, 2018).…”

The Dynamical Structure of a Warm Core Ring as Inferred from Glider Observations and Along-Track Altimetry

“…During the past two decades, gliders (autonomous underwater vehicles) have become widespread, reliable, flexible, and cost-effective measurement platforms [1][2][3][4]. They were shown to be appropriate for measuring most oceanic features and processes on a variety of time and space scales, including high-frequency internal waves [5], intense surface boundary currents [6], mesoscale and submesoscale eddies [7][8][9][10], fine-scale thermohaline stirring [11], or turbulent mixing [12].…”

Anatomy of a Cyclonic Eddy in the Kuroshio Extension Based on High-Resolution Observations

“…Glider measurements in the eastern tropical North Atlantic were used to investigate an anticyclonic eddy's finescale features, which are likely to be related to stirring by the mesoscale eddy. References [17,18] conducted an intensive field observation experiment in the northern South China Sea that indicated a strong interaction between the anticyclonic eddy and the slope topography of Dongsha Island. Ship observations can obtain the target ocean water thermohaline and current data and thereby are always used in the investigations of targeted eddies [19,20] combined a week-long cruise observations with in situ current and satellite observations to examine the 3D structure and physical properties of a cold eddy in the southwestern South China Sea.…”