Nepheloid layers in the deep Gulf of Mexico

Abstract

The first measurements of bottom nepheloid layers in the central and southern deep waters of the Gulf of Mexico west of the Yucatan peninsula were made during the three summers of 2015–2017. Particulate matter concentrations (PM) were estimated from optical profiles of beam attenuation due to particles (cp). Near-bottom maps and vertical sections of cp and PM converted from cp show evidence of sediment resuspension, possibly linked with topographic Rossby waves, loop current eddies, or eddy-topography interactions. Additional cp profiles were made along cross-slope transects around the entire Gulf of Mexico, including across the Yucatan Channel and Straits of Florida in 2017. Near-bottom PM concentrations were barely elevated in the deep Yucatan Channel and Straits of Florida at that time, except in about the surface 200 m along the northern and western boundaries. Comparison was made between areas with benthic nepheloid layers and Eddy Kinetic Energy (EKE) patterns in the deep Gulf of Mexico. Regions of high EKE or strong bottom currents in the central and eastern Gulf were found over a large region of deeply eroded furrows in the seafloor previously imaged using 3-D seismic profiling and submersible observations. Few PM measurements were obtained in the high EKE areas during these expeditions, however, historical and recent sampling show very strong nepheloid layers at stations within and westward of the region of the actively eroding furrows.