In:
Journal of Physical Oceanography, American Meteorological Society, Vol. 53, No. 2 ( 2023-02), p. 551-571
Abstract:
This study focuses on the statistical features of dissipation flux coefficient Γ in the upper South China Sea (SCS). Based on the microscale measurements collected at 158 stations in the upper SCS and derived dissipation rates of turbulent kinetic energy and temperature variance ε and χ T , via a modified method, we estimate Γ and analyze its spatiotemporal variation in an energetic and a quiescent region. We show that Γ is highly variable, which scatters over three orders of magnitude from 10 −2 to 10 1 in both regions. Ιn the energetic region, Γ is slightly greater than in the quiescent region; their median values are 0.23 and 0.17, respectively. Vertically, Γ presents a clear increasing tendency with depth in both regions, though the increasing rate is greater in the energetic region than in the quiescent region. In the upper SCS, Γ positively depends on the buoyancy Reynolds number Re b and negatively depends on the ratio of the Ozmidov scale to the Thorpe scale R OT and is scaled as , which holds for both regions. The vertical decreasing of R OT is observed, which yields parameterization of R OT = 10 −0.002 z ; this parameterization improves the performance of the Thorpe-scale method by reducing at least 50% of the bias between the observed and parameterized ε . These results shed new light on the spatiotemporal variability and modulating mechanism of Γ in the upper ocean. Significance Statement The great global ocean conveyor is maintained by vertical mixing. Turbulent kinetic energy released by local internal wave breaking goes into two parts: one part is used to furnish this vertical mixing, and the rest is dissipated into irreversible heat. The ratio of these two parts is termed as the dissipation flux coefficient and is usually treated as a constant. Our measurements suggest that this coefficient is highly spatiotemporally variable. Specific relationships are obtained when scaling this coefficient with other parameters, and mechanisms modulating this coefficient are also explored. This study sheds light on how much turbulent kinetic energy contributes to elevating the potential energy and its associated influences not only in marginal seas but also in open oceans.
Type of Medium:
Online Resource
ISSN:
0022-3670
,
1520-0485
DOI:
10.1175/JPO-D-22-0127.1
Language:
Unknown
Publisher:
American Meteorological Society
Publication Date:
2023
detail.hit.zdb_id:
2042184-9
detail.hit.zdb_id:
184162-2
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