Observations of turbulent kinetic energy dissipation at the Labrador Sea surface layer

Abstract

We present an analysis of turbulent kinetic energy dissipation rates in the upper ocean using in situ measurements collected by a coherent Doppler sonar in the Labrador Sea during summer 2004. The sonar recorded horizontal velocity fluctuations of the upper 2 m with an uncommonly small spatial resolution of 0.8 cm, allowing direct calculations of wavenumber spectra and the application of Kolmogorov theory to obtain turbulent kinetic energy dissipation rates for the first time in this area. The project presented a unique opportunity for the study of air–sea exchange during a phytoplankton bloom, being the first time a specialized air–sea interaction spar buoy was deployed during such particular event. An additional uniqueness of this experiment resulted from being the first turbulent kinetic energy dissipation rate observations obtained at higher latitudes, coincidentally in a well-known region of dense water formation, with a fundamental role in both global circulation and forecasting studies of global climate change. Focusing on the relationship between turbulent kinetic energy dissipation rates and wave phase in the upper 2 m, we estimated O[Formula: see text] turbulent kinetic energy dissipation rates, consistent with previous estimates obtained through similar devices and methods. A T-test between dissipation rates calculated at the crest and at the trough of waves showed no dependency of turbulent kinetic energy dissipation rates on the wave phase at 2 m depth, coinciding with many of the earlier findings available. a comparison with previous research showing conflicting results with our values is also discussed here linking them to the relative roles of experimental design variations, diverse dynamical frames, and particular environmental conditions.