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1. Introduction The oceanic mixed layer provides a connection between atmosphere and ocean and thus plays a central role in climate variability. For example, recent studies suggest that changes in the maximum depth of the mixed layer from one winter to the next may explain the reemergence of sea surface temperature (SST) anomalies and thus persistence of wintertime SST patterns ( Alexander et al. 2001 ; Timlin et al. 2002 ; Deser et al. 2003 ). Here we exploit the availability of a newly
1. Introduction The oceanic mixed layer provides a connection between atmosphere and ocean and thus plays a central role in climate variability. For example, recent studies suggest that changes in the maximum depth of the mixed layer from one winter to the next may explain the reemergence of sea surface temperature (SST) anomalies and thus persistence of wintertime SST patterns ( Alexander et al. 2001 ; Timlin et al. 2002 ; Deser et al. 2003 ). Here we exploit the availability of a newly
overlying lighter fluid) that in turn incites the development of rapid vertical convective plumes that communicate the surface forcing signal through depth. Vertical mixing during open-ocean convection leads to the homogenization of surface layer properties, creating a deep mixed layer ( Marshall and Schott 1999 ). The mixed layer (also referred to here as a mixed patch) plays a role in modulating the properties of dense overflows in the Southern Ocean and therefore the downwelling branch of the global
overlying lighter fluid) that in turn incites the development of rapid vertical convective plumes that communicate the surface forcing signal through depth. Vertical mixing during open-ocean convection leads to the homogenization of surface layer properties, creating a deep mixed layer ( Marshall and Schott 1999 ). The mixed layer (also referred to here as a mixed patch) plays a role in modulating the properties of dense overflows in the Southern Ocean and therefore the downwelling branch of the global
An Integrated Method for Determining the Oceanic Bottom Mixed Layer Thickness Based on WOCE Potential Temperature Profiles1. Introduction In oceans, the bottom mixed layer (BML) is the region adjacent to the ocean floor, where active mixing promoted by bottom shear and internal wave breaking leads to a vertically quasi-homogeneous profile in terms of the temperature, salinity, density, and other properties. Many interrelated physical, geochemical, and biological processes actively take place inside the BML, and these processes communicate with the ocean interior and underlying sediments ( Bowden 1978 ; Grant and
1. Introduction In oceans, the bottom mixed layer (BML) is the region adjacent to the ocean floor, where active mixing promoted by bottom shear and internal wave breaking leads to a vertically quasi-homogeneous profile in terms of the temperature, salinity, density, and other properties. Many interrelated physical, geochemical, and biological processes actively take place inside the BML, and these processes communicate with the ocean interior and underlying sediments ( Bowden 1978 ; Grant and
1. Introduction Upper oceans are characterized by the existence of a vertically quasi-uniform layer of temperature ( T , isothermal layer) and density ( ρ , mixed layer). Underneath each layer, there exists another layer with a strong vertical gradient, such as the thermocline (in temperature) and pycnocline (in density). The intense vertical turbulent mixing near the surface causes the vertically quasi-uniform layer. The mixed layer is a key component in studies of climate and the link between
1. Introduction Upper oceans are characterized by the existence of a vertically quasi-uniform layer of temperature ( T , isothermal layer) and density ( ρ , mixed layer). Underneath each layer, there exists another layer with a strong vertical gradient, such as the thermocline (in temperature) and pycnocline (in density). The intense vertical turbulent mixing near the surface causes the vertically quasi-uniform layer. The mixed layer is a key component in studies of climate and the link between
1. Introduction Strong turbulence usually exists near the surface in the ocean mixed layer as a result of wave breaking (WB; e.g., Agrawal et al. 1992 ; Drennan et al. 1996 ), leading to the response to a surface stabilizing buoyancy flux that is fundamentally different from the atmospheric boundary layer. A diurnal thermocline (or “thermocline” hereafter) is formed at a certain depth during the day in the ocean mixed layer while a temperature gradient remains small near the surface. A strong
1. Introduction Strong turbulence usually exists near the surface in the ocean mixed layer as a result of wave breaking (WB; e.g., Agrawal et al. 1992 ; Drennan et al. 1996 ), leading to the response to a surface stabilizing buoyancy flux that is fundamentally different from the atmospheric boundary layer. A diurnal thermocline (or “thermocline” hereafter) is formed at a certain depth during the day in the ocean mixed layer while a temperature gradient remains small near the surface. A strong
Improvement of the Ocean Mixed Layer Model via Large-Eddy Simulation and Inverse Estimation1. Introduction The ocean mixed layer model (OMLM), or the parameterization of vertical mixing in the upper ocean, is a key element in ocean general circulation models (OGCMs) or climate models, as this model determines the downward transport of heat, salt, and momentum in the ocean and thus controls air–sea interactions. A large number of OMLMs has been suggested to reproduce the upper ocean more realistically in OGCMs, but many OMLM features still require further improvement (e
1. Introduction The ocean mixed layer model (OMLM), or the parameterization of vertical mixing in the upper ocean, is a key element in ocean general circulation models (OGCMs) or climate models, as this model determines the downward transport of heat, salt, and momentum in the ocean and thus controls air–sea interactions. A large number of OMLMs has been suggested to reproduce the upper ocean more realistically in OGCMs, but many OMLM features still require further improvement (e
An Objective Method for Determining Ocean Mixed Layer Depth with Applications to WOCE Data1. Introduction The upper-ocean mixed layer (ML) is generally characterized by a vertically homogeneous profile of temperature, salinity, and density. This layer results from vertical mixing near the surface is promoted by various processes—wind stirring, waves, and turbulence—generated by vertical shear or nighttime convective mixing. Hence, the ML is important in establishing the mean state and variability of the World Ocean because it acts as a buffer between the atmosphere and the interior
1. Introduction The upper-ocean mixed layer (ML) is generally characterized by a vertically homogeneous profile of temperature, salinity, and density. This layer results from vertical mixing near the surface is promoted by various processes—wind stirring, waves, and turbulence—generated by vertical shear or nighttime convective mixing. Hence, the ML is important in establishing the mean state and variability of the World Ocean because it acts as a buffer between the atmosphere and the interior
1. Introduction Typhoons are extremely high wind events, which inject substantial momentum into the ocean mixed layer for a short duration along their passages. Strong typhoon winds generate turbulent entrainment and upwelling that cause subsurface cold water to entrain and uplift into surface layer, resulting in cooling of surface water and deepening of upper mixed layer. The range of sea surface temperature (SST) drop was from 1° to 6°C ( Price 1981 ), and more intensive cooling of 9°C was
1. Introduction Typhoons are extremely high wind events, which inject substantial momentum into the ocean mixed layer for a short duration along their passages. Strong typhoon winds generate turbulent entrainment and upwelling that cause subsurface cold water to entrain and uplift into surface layer, resulting in cooling of surface water and deepening of upper mixed layer. The range of sea surface temperature (SST) drop was from 1° to 6°C ( Price 1981 ), and more intensive cooling of 9°C was
representation of an MJO event, the fundamental physics behind the improved simulation is not well understood ( Jiang et al. 2020 ). Numerous studies suggest that the inability of climate models to simulate a realistic MJO may in part be due to deficiencies in modeling the dynamics of oceanic mixed layer (e.g., DeMott et al. 2015 ; Ling et al. 2017 ; Anber et al. 2017 ; Maloney and Sobel 2004 ). In particular, climate models have difficulty in simulating a realistic mixed layer depth (MLD). Overly deep
representation of an MJO event, the fundamental physics behind the improved simulation is not well understood ( Jiang et al. 2020 ). Numerous studies suggest that the inability of climate models to simulate a realistic MJO may in part be due to deficiencies in modeling the dynamics of oceanic mixed layer (e.g., DeMott et al. 2015 ; Ling et al. 2017 ; Anber et al. 2017 ; Maloney and Sobel 2004 ). In particular, climate models have difficulty in simulating a realistic mixed layer depth (MLD). Overly deep
1. Introduction The Madden–Julian oscillation (MJO) is a system of large-scale coupled patterns of atmospheric convection and winds that originate in the western tropical Indian Ocean, propagate eastward along the equator, and eventually die out in the eastern Pacific Ocean ( Madden and Julian 1972 ). Atmospheric MJO forcing exerts a profound influence on the mixed layer of the tropical Indian and Pacific Oceans through anomalous fluxes of heat, precipitation, and momentum (e.g., Hendon and
1. Introduction The Madden–Julian oscillation (MJO) is a system of large-scale coupled patterns of atmospheric convection and winds that originate in the western tropical Indian Ocean, propagate eastward along the equator, and eventually die out in the eastern Pacific Ocean ( Madden and Julian 1972 ). Atmospheric MJO forcing exerts a profound influence on the mixed layer of the tropical Indian and Pacific Oceans through anomalous fluxes of heat, precipitation, and momentum (e.g., Hendon and
