Effects of climate change and water management on West Florida Shelf's dynamics

Abstract

In the present study we evaluated, in a high-resolution simulation (1.5 km), the separate and combined effects of freshwater discharge management and climate warming by 1 °C on the Loop Current (LC) intrusions on the West Florida Shelf (WFS) and its dynamics in the subtropical western Atlantic. Based on a one-year simulation in which an LC and its eddy intruded on the WFS, either the increase of freshwater discharge or the climate warming led to a change in the stratification properties of the WFS significant enough to affect the type of LC intrusions. Increased freshwater discharge contributed to the intensification of shelf water mixing that favors surface intrusion of LC waters. On the contrary, 1 °C warming led to increased shelf waters stratification that favors bottom intrusions. Either type of intrusion leads to a different oceanographic regime on the shelf to which the ecosystem might respond differently. Our study suggests, however, that increased freshwater discharge could mitigate the effect of climate warming on the WFS by reducing shelf waters stratification. The WFS response to cold air outbreaks that are common in the fall and winter months was also analyzed. It showed that under a warmer climate, the increased stratification due to the freshwater discharge at the end of the boreal summer wet season is cancelled by the warmer climate and reduces the available potential energy on the shelf, limiting coastal upwelling, instabilities, and shelf convection.