Meeting Hurricane Beryl, which evolved from a tropical depression to a Category 5 hurricane in just 42 hours, was one of the most intense experiences of our nearly year-long sailing trip. We decided to moor under the protection of Petit Piton (743m) – one of the famous volcanic peaks of Saint Lucia, which we had the good fortune of climbing earlier.
The mooring buoy was installed at a depth of 50 meters, which was crucial for our successful survival of the tropical storm. The destructive impact came not only from the wind but also from the high waves generated by the passing hurricane Beryl. These waves, coming from the opposite direction of the wind, created a particularly damaging effect on the coast. Our sailboat’s position at a depth of 50 meters allowed us to perform CTD casts directly from the mooring. It was fascinating to observe the changes in ocean biogeochemical parameters before and after the hurricane’s passage.
Fortunately, the eye of the hurricane passed just south of us, but our location was still significantly affected by the tropical storm, with winds reaching up to 45 knots and swells of 3-4 meters. We completed the CTD casts, processed the data, and it is now ready to be presented and analyzed.
CTD cast before Hurricane Beryl passed Winward islandsDuring the tropical stormDebrize in the Caribbean Sea after tropical storm passedCTD cast under a rainbow after the Hurrican Beryl passed Winward IslandsA stable temperature stratification, with a gradient of 1 degree from the surface to the bottom (29.3 to 28.3 deg C) before the passage of the hurricane, was completely mixed over the entire depth of 50 meters, resulting in an average temperature of 28.8 deg C.A stable salinity stratification with a gradient of 1.2 from the surface to the bottom (34.7 to 35.9 ) before the passage of the hurricane turned out to be not very mixed throughout the entire depth of 50 m with a change in salinity from 34.7 to 35.2. One of the factors that did not allow salinity to be uniform as temperature was a significant rain influx of fresh water, which was included in the overall salinity balance and created a constant salinity gradient.A stable dissolved oxygen stratification, with a gradient of 10 uMol/L from the surface to the bottom (188 to 178uMol/L) before the passage of the hurricane, was well mixed over the entire depth of 50 meters, resulting in an average dissolved oxygen concentration 182 uMol/L.A stable Chlorophyll-a stratification, with a gradient of 1.5 ug/L from the surface to the bottom (1 to 2.5ug/L) before the passage of the hurricane, was well mixed over the entire depth of 50 meters, resulting in an average Chlorophyll-a concentration 1.2 ug/L.A very low and uniform backscatter attenuation coefficient value 0.0002 1/m from the surface to the bottom, which indicates very good transparency of water before the passage of the hurricane, was significantly deteriorating, resulting in an increasing attenuation coefficient about 10 times, to 0.0045 to 0.002 1/m for entire depth of 50 meters. A very low and uniform FDOM concentration value 1.05 ppb from the surface to the bottom, which indicates a lack of presence of organic matter and nutrients in water before the passage of the hurricane, increased to 1.5 to 1.2 ppb for the entire depth of 50 meters. This is the result of significant runoff of terrestrial waters after the heavy rain and significant wave and storm surge interaction in the shoreline, which brought more nutrients to the water.
