Mixing in the equatorial surface layer and thermocline
Abstract
Twelve days of microstructure measurements at the equator (140°W) in November 1984 showed a surprisingly strong effect of both the daily cycle of solar heating and wind on mixing in the upper ocean. Because of limited variations in atmospheric forcing and currents during the experiment, processes in the daily mixing cycle were similar from day to day. Only the intensity of mixing varied. The lower boundary of the diurnal surface layer separated two distinct mixing regimes, the diurnal surface layer and the thermocline. Within the diurnal surface layer (which extended to 10‐ to 35‐m depth), turbulent kinetic energy dissipation rates ε varied relatively little. Although variations in surface layer depth coincided with the daily change in direction of air‐sea surface buoyancy production of turbulent kinetic energy (or simply, the surface buoyancy flux), ε was significantly greater relative to the buoyancy flux than was expected for a simple convective layer. In the thermocline below the diurnal surface layer, ε was highly intermittent; the day‐night cycle was stronger, and variability was enhanced by turbulent “bursts” of 2–3 hours duration, which may be related to internal wave breaking events. The turbulent heat flux crossing 20‐m depth was almost equal to the surface heat flux less the irradiance penetrating below 20 m. Seventy percent of the surface heat flux was transported vertically to the water below 30 m by turbulent mixing. Only a negligible amount penetrated to the co…
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Moum et al. (1989) found the mean value of ε/(τ•Sh/ρ0) to be about 0.2 from 12 days of profiling in 1984 at 0° 140°W.
“Moum et al. (1989) found the mean value of ϵ/(τ •Sh/ρ 0 ) to be about 0.2 from 12 days of profiling in 1984 at 0 • 140 • W.”
From Deep Cycle Turbulence in Atlantic and Pacific Cold Tongues (2022) · cites this paper as Moum et al., 1989
Shipboard profiling measurements in the equatorial Pacific reveal both defining DC properties, albeit over only the cruise periods and only when profiling was rapid enough to resolve the diurnal cycle.
“Shipboard profiling measurements 76 in the equatorial Pacific (Gregg et al., 1985;Moum & Caldwell, 1985;Moum et al., 1989) 77 reveal both of the defining DC properties, albeit over only the cruise periods (typically 78 a few weeks) and only when profiling was rapid enough to resolve the diurnal cycle.”
From Deep Cycle Turbulence in Atlantic and Pacific Cold Tongues (2022) · cites this paper as Moum et al., 1989
In Figure 3a, these scalings neatly collapse the vertical profiles of ε from the three sites to within a factor of 2 at each scaled depth and close to the value of 0.2 found for the limited data set examined by Moum et al. (1989).
“In Figure 3a, these scalings neatly collapse the vertical profiles of ϵ from the three sites to within a factor of 2 at each scaled depth and close to the value of 0.2 found for the limited data set examined by Moum et al. (1989).”
From Deep Cycle Turbulence in Atlantic and Pacific Cold Tongues (2022) · cites this paper as Moum et al., 1989
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Sea surface cooling at the Equator by subsurface mixing in tropical instability waves
Moum, J. N., Lien, R.-C., Perlin, A., Nash, J. D., Gregg, M. C., & Wiles, P. J. (2009) · Nature Geoscience · doi:10.1038/ngeo657 · Cited by 137 · see citing works
Self-citationDeep Cycle Turbulence in Atlantic and Pacific Cold Tongues
Moum, J. N., Hughes, K. G., Shroyer, E. L., Smyth, W. D., Cherian, D., Warner, S. J., Bourlès, B., Brandt, P., & Dengler, M. (2022) · Geophysical Research Letters · doi:10.1029/2021gl097345 · Cited by 34 · see citing works
“The existence and behavior of DC turbulence at the equator and 140°W has been well-established through a series of short shipboard profiling investigations there (Gregg et al., 1985; Lien et al., 1995; Moum & Caldwell, 1985; Moum et al., 1989; Smyth et al., 2013).”
BackgroundInfluentialSelf-citation
- Authors
- Moum, J. N., Caldwell, D. R., & Paulson, C. A.
- ORCID
- Moum, James N.
- Venue
- Journal of Geophysical Research: Oceans
- Publisher
- American Geophysical Union (AGU)
- Published
- 1989-02-05
- Volume
- 94
- Issue
- C2
- Pages
- 2005-2022
- ISSN
- 0148-0227 (ISSN-L)
- OpenAlex
- W2105914586
- Cited by
- 146
- References
- 0
- Citations by year
- 2026: 1 · 2025: 1 · 2024: 2 · 2023: 3 · 2022: 5 · 2021: 6 · 2020: 2 · 2019: 8 · 2018: 3 · 2017: 7 · 2016: 3 · 2015: 3 · 2014: 7 · 2013: 3 · 2012: 6
- FWCI
- 7.27
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Journal of Geophysical Research Atmospheres (publishedVersion)
- Topics
- Physical Sciences › Earth and Planetary Sciences › Oceanography › Oceanographic and Atmospheric Processes
- Physical Sciences › Earth and Planetary Sciences › Oceanography › Ocean Waves and Remote Sensing
- Physical Sciences › Engineering › Computational Mechanics › Fluid Dynamics and Turbulent Flows
- Keywords
- ocean mixing, thermocline, turbulent kinetic energy dissipation, diurnal cycle, solar heating, wind forcing, surface buoyancy flux, turbulent heat flux, internal wave breaking, Equatorial Undercurrent, Richardson number, upper ocean turbulence, equatorial Pacific
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