Affiliation:
1. Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78713-8924, USA
2. Oceanography Division, U.S. Naval Research Laboratory, Stennis Space Center, MS 39529, USA
Abstract
The ocean’s mixed layer depth (MLD) plays an important role in understanding climate dynamics, especially during extreme weather occurrences like hurricanes. This study investigates the effects of Hurricane Katrina (2005) on the MLD in the Gulf of Mexico, using the Delft3D modeling system. By integrating hydrodynamics and wave dynamics modules, we simulate the ocean’s response to extreme weather, focusing on temperature, salinity and MLD variations. Our analysis reveals significant cooling and mixing induced by Katrina, resulting in spatial and temporal fluctuations in temperature (~±4 °C) and salinity (~±1.5 ppt). The MLD is estimated using a simple threshold method, revealing a substantial deepening to ~120 m on 29–30 August during Hurricane Katrina in the middle of the northern Gulf of Mexico, compared to an average MLD of ~20–40 m during pre-storm conditions. It took about 18 days to recover to ~84% of the pre-storm level after Katrina. Compared to the stand-alone FLOW model, the coupled FLOW+WAVE model yields a deeper MLD of ~5%. The MLD recovery and wave effect on the MLD provide insights from various scientific, environmental and operational perspectives, offering a valuable basis for ocean management, planning and applications, particularly during extreme weather events.