Measurements of Hurricane Induced High-Frequency Currents
NAVAL RESEARCH LAB STENNIS DETACHMENT STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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Hurricanes are powerful, energetic storms that can be fueled by warm ocean waters, while simultaneously driving transport and mixing under their path. Wind-driven mixing is an important mechanism for generating internal waves, and hurricanes are capable of generating particularly high levels of mixing. The internal waves, in turn, allow diapycnal mixing in the ocean, accelerating heat transfer from the near surface to deeper waters. This plays a role in global thermohaline circulation, which affects heat transfer and density properties throughout the oceans. However, while the importance of internal waves is well established, direct measurements of hurricane-generated internal waves over the shelf and slope regions are scarce. As a result, the mechanisms for the generation of these waves by storms are poorly understood. In this paper, we examine the high frequency response and generation of internal waves by Hurricane Ivan as it travelled over the continental shelf edge and slope in the Gulf of Mexico. Velocity data were collected as part of the Naval Research Laboratorys Shelf Energetics and Exchange Dynamics SEED experiment. Moorings consisted of Trawl Resistant Bottom Mounts TRBMs in the form of a dome-shaped pod known as a Barny due to its barnacle-like shape. The Barnies housed ADCPs and wavetide gauges, and during the hurricane were subject to extreme current conditions. In particular, over the shelf where water depths are 60 - 90 meters and surface waves reached significant wave heights of at least 20 meters, bottom currents generated by these waves were over 2 meters sexp -1. Despite these extreme conditions, which set the nearby National Data Buoy Center buoy 42040 adrift, the Barnies proved themselves to be robust and continued to measure water velocity and pressure both during and after the hurricanes presence in the region.
- Physical and Dynamic Oceanography