Upper-ocean Response to Hurricane Gonzalo (2014): Salinity Effects Revealed by Targeted and Sustained Underwater Glider Observation
Ricardo M. Domingues1,2, Gustavo Jorge Goni3, Francis Bringas2, Sang-Ki Lee1,2, Hyun-Sook Kim4, George R Halliwell Jr3, Ricardo M. Domingues1,5, Julio M Morell6 and Luis Pomales7, (1)University of Miami, Cooperative Institute for Marine and Atmospheric Studies, Miami, FL, United States, (2)Atlantic Oceanographic and Meteorological Laboratory, Miami, FL, United States, (3)NOAA Atlantic Oceanographic and Meteorological Laboratory, Miami, FL, United States, (4)IMSG at EMC/NCEP/NOAA, College Park, MD, United States, (5)National Centers For Environmental Prediction-Environmental Modeling Center, College Park, MD, United States, (6)University of Puerto Rico Mayaguez, Caribbean Coastal Ocean Observing System, Mayaguez, PR, United States, (7)University of Puerto Rico Mayagüez Campus, Marine Sciences, Mayagüez, PR, United States
Abstract:
In July 2014, two underwater gliders were deployed off Puerto Rico as part of a multi-institutional effort lead by NOAA/AOML funded by the Disaster Appropriations Relief Act of 2013 known as Sandy Supplemental. The goal of this work is to collect ocean observations to: (1) investigate the response of the ocean to tropical cyclone (TC) wind conditions; (2) improve understanding on the role that the ocean plays in the intensification of TCs; and (3) help improve TC seasonal and intensity forecasts. The two gliders were piloted along predetermined tracks in the Caribbean Sea and in the North Atlantic Ocean (Figure 1), where TCs very often travel and intensify. On October 12, 2014, TC Gonzalo developed in the tropical North Atlantic, reaching the status of Category 3 hurricane on October 14 as it travelled ~85 km northeast of the location of the glider (site B, Figure 1). The sampling strategy adopted during the passage of Hurricane Gonzalo consisted of carrying out observations: along a repeat section three times between sites A and B, one before and two after the passage of the hurricane; and at a fixed location at site B during the passage of the hurricane. Observations collected before, during, and after the passage of this hurricane were analyzed to improve our understanding of the upper-ocean response to hurricane winds.
The main finding in this study is that salinity played an important role on the upper-ocean response to Hurricane Gonzalo; where a near-surface barrier-layer has likely suppressed the hurricane-induced upper-ocean cooling, leading to smaller than expected temperature changes of –0.4ºC. Post-storm observations also revealed a partial recovery of the ocean to pre-storm conditions 11 days after the hurricane. Glider observations were further compared with outputs from a numerical coupled atmospheric-ocean model used for hurricane prediction to evaluate the model performance in simulating the upper-ocean response during Hurricane Gonzalo. The comparison revealed that model‑observations discrepancies were largely linked to salinity effects. Results presented in this study emphasize the value of underwater glider observations for improving our knowledge of how the ocean responds to tropical cyclone winds and for tropical cyclone intensification studies and forecasts.
