Surface Layer Structure and Turbulent Kinetic Energy Dissipation Across the East Australian Current

Andrew FRIEDRICHS, Remo COSSU, David SPENCER, Alexander LeBaron Forrest Forrest, Charles LEMCKERT, Larissa PEREZ

Research output: Contribution to conference (non-published works)Abstract

Abstract

The East Australian Current (EAC) is a highly energetic and intricate mixing system in the western Pacific. Between variable wind forcing, and separate surface- and under-currents, a complex turbulent surface layer develops. A Turbulence Ocean Microstructure Acquisition Profiler (TurboMAP) was used to collect vertical profiles of shear and Conductivity-Temperature-Depth (CTD) at six stations transecting the EAC. Using the universal Nasmyth spectrum, the shear microstructure profiles provided estimates of turbulent kinetic energy (TKE). Temperature and salinity profiles typically revealed a three-layer structure: a well-mixed layer in the upper 30 m, an underlying, clearly defined subsurface layer, and an extensive thermocline region spanning a depth of 100 m or more. Shear data and TKE dissipation estimates were compared alongside the CTD profiles to clearly illustrate the three-layer structure. TKE dissipation trended to a local minimum in the upper mixed layer on the order of 10-9 W/kg, as wave action attenuated. The magnitude of dissipation then proceeded to fluctuate between 10-9 and 10-8 W/kg with subsequent stratification. Additionally, local peaks in shear and TKE dissipation were associated with the sharp transitions between layers and instabilities along the thermocline. Such observations of turbulence across the EAC provide a rare and unique insight into the dynamic nature of the upper ocean. The turbulent structure of these sublayers suggests the potential for rapid mixing and transport of nutrients between the mid- and upper waters along the EAC.
Original languageEnglish
Pages1
Number of pages1
Publication statusPublished - 2017
EventAnnual Meeting of the Asia-Oceania-Geosciences-Society (AOGS) - Singapore, Singapore
Duration: 6 Aug 201711 Aug 2017
Conference number: 14
http://www.asiaoceania.org/aogs2017/

Conference

ConferenceAnnual Meeting of the Asia-Oceania-Geosciences-Society (AOGS)
Abbreviated titleAOGS
CountrySingapore
CitySingapore
Period6/08/1711/08/17
Internet address

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energy dissipation
kinetic energy
surface layer
thermocline
mixed layer
microstructure
conductivity
turbulence
temperature
wind forcing
wave action
profiler
upper ocean
vertical profile
dissipation
stratification
energetics
salinity
nutrient
ocean

Cite this

FRIEDRICHS, A., COSSU, R., SPENCER, D., Forrest, A. L. F., LEMCKERT, C., & PEREZ, L. (2017). Surface Layer Structure and Turbulent Kinetic Energy Dissipation Across the East Australian Current. 1. Abstract from Annual Meeting of the Asia-Oceania-Geosciences-Society (AOGS), Singapore, Singapore.
FRIEDRICHS, Andrew ; COSSU, Remo ; SPENCER, David ; Forrest, Alexander LeBaron Forrest ; LEMCKERT, Charles ; PEREZ, Larissa. / Surface Layer Structure and Turbulent Kinetic Energy Dissipation Across the East Australian Current. Abstract from Annual Meeting of the Asia-Oceania-Geosciences-Society (AOGS), Singapore, Singapore.1 p.
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title = "Surface Layer Structure and Turbulent Kinetic Energy Dissipation Across the East Australian Current",
abstract = "The East Australian Current (EAC) is a highly energetic and intricate mixing system in the western Pacific. Between variable wind forcing, and separate surface- and under-currents, a complex turbulent surface layer develops. A Turbulence Ocean Microstructure Acquisition Profiler (TurboMAP) was used to collect vertical profiles of shear and Conductivity-Temperature-Depth (CTD) at six stations transecting the EAC. Using the universal Nasmyth spectrum, the shear microstructure profiles provided estimates of turbulent kinetic energy (TKE). Temperature and salinity profiles typically revealed a three-layer structure: a well-mixed layer in the upper 30 m, an underlying, clearly defined subsurface layer, and an extensive thermocline region spanning a depth of 100 m or more. Shear data and TKE dissipation estimates were compared alongside the CTD profiles to clearly illustrate the three-layer structure. TKE dissipation trended to a local minimum in the upper mixed layer on the order of 10-9 W/kg, as wave action attenuated. The magnitude of dissipation then proceeded to fluctuate between 10-9 and 10-8 W/kg with subsequent stratification. Additionally, local peaks in shear and TKE dissipation were associated with the sharp transitions between layers and instabilities along the thermocline. Such observations of turbulence across the EAC provide a rare and unique insight into the dynamic nature of the upper ocean. The turbulent structure of these sublayers suggests the potential for rapid mixing and transport of nutrients between the mid- and upper waters along the EAC.",
keywords = "turbulence, East Australian Current, microstructure, ocean dynamics",
author = "Andrew FRIEDRICHS and Remo COSSU and David SPENCER and Forrest, {Alexander LeBaron Forrest} and Charles LEMCKERT and Larissa PEREZ",
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language = "English",
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FRIEDRICHS, A, COSSU, R, SPENCER, D, Forrest, ALF, LEMCKERT, C & PEREZ, L 2017, 'Surface Layer Structure and Turbulent Kinetic Energy Dissipation Across the East Australian Current' Annual Meeting of the Asia-Oceania-Geosciences-Society (AOGS), Singapore, Singapore, 6/08/17 - 11/08/17, pp. 1.

Surface Layer Structure and Turbulent Kinetic Energy Dissipation Across the East Australian Current. / FRIEDRICHS, Andrew; COSSU, Remo; SPENCER, David; Forrest, Alexander LeBaron Forrest; LEMCKERT, Charles; PEREZ, Larissa.

2017. 1 Abstract from Annual Meeting of the Asia-Oceania-Geosciences-Society (AOGS), Singapore, Singapore.

Research output: Contribution to conference (non-published works)Abstract

TY - CONF

T1 - Surface Layer Structure and Turbulent Kinetic Energy Dissipation Across the East Australian Current

AU - FRIEDRICHS, Andrew

AU - COSSU, Remo

AU - SPENCER, David

AU - Forrest, Alexander LeBaron Forrest

AU - LEMCKERT, Charles

AU - PEREZ, Larissa

PY - 2017

Y1 - 2017

N2 - The East Australian Current (EAC) is a highly energetic and intricate mixing system in the western Pacific. Between variable wind forcing, and separate surface- and under-currents, a complex turbulent surface layer develops. A Turbulence Ocean Microstructure Acquisition Profiler (TurboMAP) was used to collect vertical profiles of shear and Conductivity-Temperature-Depth (CTD) at six stations transecting the EAC. Using the universal Nasmyth spectrum, the shear microstructure profiles provided estimates of turbulent kinetic energy (TKE). Temperature and salinity profiles typically revealed a three-layer structure: a well-mixed layer in the upper 30 m, an underlying, clearly defined subsurface layer, and an extensive thermocline region spanning a depth of 100 m or more. Shear data and TKE dissipation estimates were compared alongside the CTD profiles to clearly illustrate the three-layer structure. TKE dissipation trended to a local minimum in the upper mixed layer on the order of 10-9 W/kg, as wave action attenuated. The magnitude of dissipation then proceeded to fluctuate between 10-9 and 10-8 W/kg with subsequent stratification. Additionally, local peaks in shear and TKE dissipation were associated with the sharp transitions between layers and instabilities along the thermocline. Such observations of turbulence across the EAC provide a rare and unique insight into the dynamic nature of the upper ocean. The turbulent structure of these sublayers suggests the potential for rapid mixing and transport of nutrients between the mid- and upper waters along the EAC.

AB - The East Australian Current (EAC) is a highly energetic and intricate mixing system in the western Pacific. Between variable wind forcing, and separate surface- and under-currents, a complex turbulent surface layer develops. A Turbulence Ocean Microstructure Acquisition Profiler (TurboMAP) was used to collect vertical profiles of shear and Conductivity-Temperature-Depth (CTD) at six stations transecting the EAC. Using the universal Nasmyth spectrum, the shear microstructure profiles provided estimates of turbulent kinetic energy (TKE). Temperature and salinity profiles typically revealed a three-layer structure: a well-mixed layer in the upper 30 m, an underlying, clearly defined subsurface layer, and an extensive thermocline region spanning a depth of 100 m or more. Shear data and TKE dissipation estimates were compared alongside the CTD profiles to clearly illustrate the three-layer structure. TKE dissipation trended to a local minimum in the upper mixed layer on the order of 10-9 W/kg, as wave action attenuated. The magnitude of dissipation then proceeded to fluctuate between 10-9 and 10-8 W/kg with subsequent stratification. Additionally, local peaks in shear and TKE dissipation were associated with the sharp transitions between layers and instabilities along the thermocline. Such observations of turbulence across the EAC provide a rare and unique insight into the dynamic nature of the upper ocean. The turbulent structure of these sublayers suggests the potential for rapid mixing and transport of nutrients between the mid- and upper waters along the EAC.

KW - turbulence

KW - East Australian Current

KW - microstructure

KW - ocean dynamics

M3 - Abstract

SP - 1

ER -

FRIEDRICHS A, COSSU R, SPENCER D, Forrest ALF, LEMCKERT C, PEREZ L. Surface Layer Structure and Turbulent Kinetic Energy Dissipation Across the East Australian Current. 2017. Abstract from Annual Meeting of the Asia-Oceania-Geosciences-Society (AOGS), Singapore, Singapore.