Observations and Analyses of Upper Ocean Responses to Tropical Storms and Hurricanes in the Vicinity of Bermuda

The interaction between the atmosphere and ocean is of fundamental importance for understanding the dynamics and thermodynamics of the atmosphere and the ocean. Understanding of the upper ocean response to intense wind forcing has been limited by the paucity of direct observations. A circular region within a radius of 400 km of Bermuda has been struck by 188 tropical storms or hurricanes from 1851 through 2005 and by 20 since 1995. Here we describe new direct and remote sensing observations and analyses of recent events near the Bermuda Test Mooring including Hurricane Fabian (2003), Tropical Storm Harvey (2005) and Hurricane Nate (2005). Comparisons with Hurricane Felix of 1995 are also presented. Key features of the ocean response include rapid deepening of the mixed layer, rightward bias in SST cooling in relation to the hurricane or storm track, production of high velocity near-inertial currents, generation of near-inertial internal waves, and in some cases ocean color wakes produced by hurricaneforced upwelling and entrainment. The most impressive upper ocean response of the recent events was produced by Hurricane Fabian where SST cooling exceeded 4 °C, vertical mixing occurred to a depth of greater than 130 m and upper ocean currents reached 100 cm s. Fabian triggered an ocean color event visible in SeaWiFS satellite images. The data sets and analyses presented here provide key information valuable for the development of advanced models designed to improve understanding and prediction of upper ocean responses and atmospheric feedbacks for hurricanes along with biological and biogeochemical effects.