Heat Content Anomaly and Decay of Warm‐Core Rings: the Case of the Gulf of Mexico

Abstract

In this study, we harness the 25‐year satellite‐altimeter record, in concert with a vast array of in situ measurements, to estimate the heat content anomaly of 32 warm‐core rings in the Gulf of Mexico (GoM). The decay rate of these mesoscale eddies is studied in detail, and it is shown that they release the majority of their heat as they drift in the central GoM (away from topographic obstacles). The surface heat fluxes from the eddies are shown to be small in comparison to the total rate of heat loss from the eddies, suggesting that heat is primarily released toward the surrounding water masses. Integrating the total heat evolution equation over the warm‐core rings yields an estimate of their effective lateral diffusivity coefficient. The long‐term impact of warm‐core rings on heat and salt balance in the GoM is also discussed.

Turbulent Mixing in a Loop Current Eddy From Glider‐Based Microstructure Observations

“…Horizontal fluxes associated with lateral intrusions were calculated using K h calculated Fh = ρCp Tz , with horizontal diffusivity = K T / (Ruddick et al, 2010) and for salt = K S / (Hebert et al, 1990); T x , and S x are the thermal and saline lateral bulk gradients, respectively. Horizontal diffusivities for heat and salt were estimated to be 2.8/0.15 m 2 /s, which is in agreement with other studies (Fine et al, 2018; Hebert et al, 1990; Meunier et al, 2020; Ruddick et al, 2010) and calculated averaged fluxes (within regions highlighted with magenta contours on Figures 6b and 6e) resulted in 2,800 W/m 2 and 2.36 * 10 −5 psu m/s of heat and salt transport. To quantify the total heat and salt transport we modeled the eddy as having a radius of 100 km and vertical extent of 200 m and assumed azimuthal symmetry.…”

Do Loop Current eddies stimulate productivity in the Gulf of Mexico?

“…However, in addition to depending on phytoplankton concentration, it is also affected by several other factors mainly produced by intracellular physiological mechanisms (Geider, 1987). In particular, photoacclimation processes have been proven to be determinant to explain [Chl] surf variability in oligotrophic areas (Mignot et al, 2014). In the GoM open waters, this issue was specifically addressed at a basin scale in Pasqueron de considering in situ particulate backscattering measurements and in Damien et al (2018) from modeling tools.…”

“…In addition, in situ measurements in oligotrophic regions have shown that the surface [Chl] variability, observed from ocean color satellite imagery, is not necessarily representative of the total phytoplankton (carbon) biomass variability in the water column (Siegel et al, 2013;Mignot et al, 2014). In particular, a surface [Chl] winter increase may result from physiological mechanisms (i.e., modification of the ratio of [Chl] to phytoplankton carbon biomass) or from a vertical redistribution of the phytoplankton (Mayot et al, 2017) rather than from changes in the biomass content.…”

Do Loop Current Eddies stimulate productivity in the Gulf of Mexico?

“…This homogenization mainly arises from vertical mixing and winter mixed layer convection (Sosa-Gutierez et al, 2020). Horizontal intrusions and filamentation may also contribute to this homogenization (Meunier et al, 2020). The composites also suggest that almost no ASTUW enters the GoM apart from the LCEs.…”

“…In the LCE core, this decay is considered as moderate since lateral diffusivity is expected to be relatively low (section V.1). This process may however be considerable in the LCE ring where the erosion rates are important (Meunier at al., 2020). Eddy-wind interactions are due to mesoscale modulation of the Ekman transport.…”