The Role of Freshwater Forcing on Surface Predictability in the Gulf of Mexico

Abstract

AbstractThe potential predictability of fields at the ocean surface in the northern Gulf of Mexico (GoM) is investigated through five ensembles of regional ocean simulations between 2014 and 2016. The ensembles explore two horizontal resolutions and different representations of the riverine inflow, and focus on the interactions between the Loop Current system (LCS) and the riverine system. The potential predictability of the surface fields is high when simulated by an ocean‐only model forced by appropriate atmospheric forcing and boundary conditions, and the ensembles simulate similar LCS behavior up to 5 months. The ensemble spread provides a mean to quantify the potential predictability. The ensembles confirm that LCS‐riverine interactions are modulated by the LC mesoscale variability. The relationship is two‐ways, with the LCS being influenced by—And not only influencing—The freshwater plume. Whenever the freshwater flux is strong, the northward extension of the LCS is constrained by the intensified salinity fronts. This influence is slightly stronger if the riverine inflow is simulated in an active fashion with a meridional velocity component proportional to the flux. Sea surface temperature (SST) and salinity (SSS) predictability have opposite seasonality in their signal, with the SST (SSS) being more predictable in summer (winter). Partially resolving submesoscale instabilities and improving the realism of the riverine fluxes’ representation causes the spread to increase, especially in SST. When increasing resolution, the spread increases also for surface vorticity due to feedbacks between the mesoscale and submesoscale circulations. The intraseasonal and interannual signal in vorticity is however similar among ensembles.