Effect of Mesoscale Eddies on the Vertical Distribution of Dissolved Inorganic Nutrients in Open Waters of the Gulf of Mexico during a Warm and a Cold Season

Erika Lee1, Victor F Camacho-Ibar2, Jorge Velasquez1 and Augusto Valencia3, (1)Universidad Autónoma de Baja California, Facultad de Ciencias Marinas, Ensenada, BJ, Mexico, (2)Autonomous University of Baja California- UABC, Instituto de Investigaciones Oceanológicas, Ensenada, Mexico, (3)Autonomous University of Baja California, Instituto de Investigaciones Oceanologicas, Ensenada, BJ, Mexico
In Mexican waters of the deep basin (>1000 m) of the Gulf of Mexico (GoM) there is a scarce knowledge about the magnitude of the mesoscale eddies effect on vertical distribution of dissolved inorganic nutrients. In this study, mean hydrographic vertical profiles were obtained from stations influenced by cyclonic eddies (CEs) and anticyclonic eddies (from the Loop Current, LCEs) in the GoM, west of 88°W. The separation between CEs and LCEs was based on the relationship of the dynamic height and the depth of the 25.5 kg m-3 isopycnal (p<0.05), associated to the depth of the nutricline, from data of campaigns carried out in a cold season (XIXIMI-3; Feb-Mar 2013) and in a warm season (XIXIMI-5; Jun 2016). Of the total of stations in both campaigns, ~30% were influenced by LCEs and 60% by CEs. In both seasons the maximum difference between CEs and LCEs for conservative temperature was ~3.3°C at 120 m, ~0.39 g kg-1 for absolute salinity at 190 m, and ~7.45, ~0.37, ~2.4 µmol kg-1 for N+N, phosphate and silicic acid, respectively, at 150 m of depth. The seasonal variability of the conservative and non-conservative properties seems to be masked by mesoscale eddies in the GoM. The effect of this contrasting physical scenarios on the magnitude of remineralization of organic matter below the euphotic zone will be explored.