The influence of surface gravity waves on the injection of turbulence in the upper ocean
Observations were made in the near-surface layer, at about 8 m depth in 132 m deep water off the coast of Ålesund in Norway, for a duration of 2.5 months in late 2011. The measurement period covers the passage of two low pressure systems with substantial wind and wave forcing. The time series of the...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-06-01
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| Series: | Nonlinear Processes in Geophysics |
| Online Access: | http://www.nonlin-processes-geophys.net/21/713/2014/npg-21-713-2014.pdf |
| Summary: | Observations were made in the
near-surface layer, at about 8 m depth in 132 m deep water off the coast of
Ålesund in Norway, for a duration of 2.5 months in late 2011. The
measurement period covers the passage of two low pressure systems with
substantial wind and wave forcing. The time series of the dissipation rate of
turbulent kinetic energy, ε, and the estimates of surface gravity
waves are analysed. Dissipation rates varied by 5 orders of magnitude and
reached 10<sup>-5</sup>–10<sup>-4</sup> W kg<sup>−1</sup> in conditions when wind speed
exceeded 15 m s<sup>−1</sup> and the significant wave height was of the order of
10 m. The data set suggests substantial injection of turbulence from
breaking surface gravity waves and Langmuir turbulence. To support and
interpret the observations, numerical calculations are conducted using a
second-order turbulence closure scheme based on the Mellor–Yamada level 2.5
scheme, modified to incorporate the near-surface processes such as Langmuir
circulation and wave breaking. The results from a run forced by observed wind
and wave fields compare favourably with the observations. Comparisons with
other near-surface data sets available from the literature lend confidence on
our dissipation measurements and the wave-forced simulations. |
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| ISSN: | 1023-5809 1607-7946 |