Mixed and mixing layer depths in the ocean surface boundary layer under conditions of diurnal stratification

G. Sutherland; G. Reverdin; L. Marié; B. Ward

doi:10.1002/2014GL061939

Mixed and mixing layer depths in the ocean surface boundary layer under conditions of diurnal stratification

G. Sutherland
, G. Reverdin
, L. Marié
, B. Ward

Physics

Research output: Contribution to a Journal (Peer & Non Peer) › Article › peer-review

51 Citations (Scopus)

Abstract

A comparison between mixed (MLD) and mixing (XLD) layer depths is presented from the SubTRopical Atlantic Surface Salinity Experiment (STRASSE) cruise in the subtropical Atlantic. This study consists of 400 microstructure profiles during fairly calm and moderate conditions (2 < U₁₀ < 10 m s^-1) and strong solar heating O(1000 W m^-2). The XLD is determined from a decrease in the turbulent dissipation rate to an assumed background level. Two different thresholds for the background dissipation level are tested, 10^-8 and 10^-9 m² s^-3, and these are compared with the MLD as calculated using a density threshold. The larger background threshold agrees with the MLD during restratification but only extends to half the MLD during nighttime convection, while the lesser threshold agrees well during convection but is deeper by a factor of 2 during restratification. Observations suggest the use of a larger density threshold to determine the MLD in a buoyancy driven regime.

Original language	English
Pages (from-to)	8469-8476
Number of pages	8
Journal	Geophysical Research Letters
Volume	41
Issue number	23
DOIs	https://doi.org/10.1002/2014GL061939
Publication status	Published - 16 Dec 2014

Keywords

buoyancy
mixed and mixing layer depths
ocean surface boundary layer

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10.1002/2014GL061939

Cite this

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title = "Mixed and mixing layer depths in the ocean surface boundary layer under conditions of diurnal stratification",

abstract = "A comparison between mixed (MLD) and mixing (XLD) layer depths is presented from the SubTRopical Atlantic Surface Salinity Experiment (STRASSE) cruise in the subtropical Atlantic. This study consists of 400 microstructure profiles during fairly calm and moderate conditions (2 < U10 < 10 m s-1) and strong solar heating O(1000 W m-2). The XLD is determined from a decrease in the turbulent dissipation rate to an assumed background level. Two different thresholds for the background dissipation level are tested, 10-8 and 10-9 m2 s-3, and these are compared with the MLD as calculated using a density threshold. The larger background threshold agrees with the MLD during restratification but only extends to half the MLD during nighttime convection, while the lesser threshold agrees well during convection but is deeper by a factor of 2 during restratification. Observations suggest the use of a larger density threshold to determine the MLD in a buoyancy driven regime.",

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author = "G. Sutherland and G. Reverdin and L. Mari{\'e} and B. Ward",

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doi = "10.1002/2014GL061939",

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TY - JOUR

T1 - Mixed and mixing layer depths in the ocean surface boundary layer under conditions of diurnal stratification

AU - Sutherland, G.

AU - Reverdin, G.

AU - Marié, L.

AU - Ward, B.

PY - 2014/12/16

Y1 - 2014/12/16

N2 - A comparison between mixed (MLD) and mixing (XLD) layer depths is presented from the SubTRopical Atlantic Surface Salinity Experiment (STRASSE) cruise in the subtropical Atlantic. This study consists of 400 microstructure profiles during fairly calm and moderate conditions (2 < U10 < 10 m s-1) and strong solar heating O(1000 W m-2). The XLD is determined from a decrease in the turbulent dissipation rate to an assumed background level. Two different thresholds for the background dissipation level are tested, 10-8 and 10-9 m2 s-3, and these are compared with the MLD as calculated using a density threshold. The larger background threshold agrees with the MLD during restratification but only extends to half the MLD during nighttime convection, while the lesser threshold agrees well during convection but is deeper by a factor of 2 during restratification. Observations suggest the use of a larger density threshold to determine the MLD in a buoyancy driven regime.

AB - A comparison between mixed (MLD) and mixing (XLD) layer depths is presented from the SubTRopical Atlantic Surface Salinity Experiment (STRASSE) cruise in the subtropical Atlantic. This study consists of 400 microstructure profiles during fairly calm and moderate conditions (2 < U10 < 10 m s-1) and strong solar heating O(1000 W m-2). The XLD is determined from a decrease in the turbulent dissipation rate to an assumed background level. Two different thresholds for the background dissipation level are tested, 10-8 and 10-9 m2 s-3, and these are compared with the MLD as calculated using a density threshold. The larger background threshold agrees with the MLD during restratification but only extends to half the MLD during nighttime convection, while the lesser threshold agrees well during convection but is deeper by a factor of 2 during restratification. Observations suggest the use of a larger density threshold to determine the MLD in a buoyancy driven regime.

KW - buoyancy

KW - mixed and mixing layer depths

KW - ocean surface boundary layer

UR - https://www.scopus.com/pages/publications/84921549798

U2 - 10.1002/2014GL061939

DO - 10.1002/2014GL061939

M3 - Article

SN - 0094-8276

VL - 41

SP - 8469

EP - 8476

JO - Geophysical Research Letters

JF - Geophysical Research Letters

IS - 23

ER -

Mixed and mixing layer depths in the ocean surface boundary layer under conditions of diurnal stratification

Abstract

Keywords

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