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1. Introduction Estimates of mixed layer depth are routinely used to model wild fire behavior ( Clements et al. 2007 ) and trajectories of air pollutants and hazardous materials ( Dabberdt et al. 2004 ). In extreme cases, forecasts may lead local authorities to order evacuations, thus impacting lives, property, and the local economy. Mixed layer depth may be measured directly by rawinsondes; these data are weighted heavily when making short-range forecasts near balloon sites. The current
1. Introduction Estimates of mixed layer depth are routinely used to model wild fire behavior ( Clements et al. 2007 ) and trajectories of air pollutants and hazardous materials ( Dabberdt et al. 2004 ). In extreme cases, forecasts may lead local authorities to order evacuations, thus impacting lives, property, and the local economy. Mixed layer depth may be measured directly by rawinsondes; these data are weighted heavily when making short-range forecasts near balloon sites. The current
1. Introduction Boccaletti et al. (2007 , hereafter BFF ) and Fox-Kemper et al. (2008a , hereafter FFH ) study the restratification due to ageostrophic baroclinic instabilities that develop at fronts in the ocean surface mixed layer. BFF and FFH study the restratification once the instabilities have reached finite amplitude, by focusing on a mixed layer (ML) front in a reentrant channel. First, the front geostrophically adjusts ( Tandon and Garrett 1995 ) and then yields to ageostrophic
1. Introduction Boccaletti et al. (2007 , hereafter BFF ) and Fox-Kemper et al. (2008a , hereafter FFH ) study the restratification due to ageostrophic baroclinic instabilities that develop at fronts in the ocean surface mixed layer. BFF and FFH study the restratification once the instabilities have reached finite amplitude, by focusing on a mixed layer (ML) front in a reentrant channel. First, the front geostrophically adjusts ( Tandon and Garrett 1995 ) and then yields to ageostrophic
/ ρ O C p H : ρ O is a reference ocean density, C p is the specific heat of seawater, and H is the mixed layer depth). Moreover, patterns that form in this type of modeled SST-like tracer from the combined influence of stirring by mesoscale eddies and damping–dissipative effects are consistent with those found in SST from satellite observations ( Abraham and Bowen 2002 ). Comparison of the spatial patterns in model and observational data from the southwest Tasman Sea has indicated a
/ ρ O C p H : ρ O is a reference ocean density, C p is the specific heat of seawater, and H is the mixed layer depth). Moreover, patterns that form in this type of modeled SST-like tracer from the combined influence of stirring by mesoscale eddies and damping–dissipative effects are consistent with those found in SST from satellite observations ( Abraham and Bowen 2002 ). Comparison of the spatial patterns in model and observational data from the southwest Tasman Sea has indicated a
1. Introduction The surface mixed layer of the ocean is a weakly stratified layer often encountered below the air–sea interface, where turbulent mixing is strong in response to atmospheric forcing. The processes that set the stratification and ventilation of the mixed layer are an essential part of the coupled climate system, because this layer regulates the exchange of heat, freshwater, and all other climatically relevant tracers between the atmosphere and the ocean. Traditional models assume
1. Introduction The surface mixed layer of the ocean is a weakly stratified layer often encountered below the air–sea interface, where turbulent mixing is strong in response to atmospheric forcing. The processes that set the stratification and ventilation of the mixed layer are an essential part of the coupled climate system, because this layer regulates the exchange of heat, freshwater, and all other climatically relevant tracers between the atmosphere and the ocean. Traditional models assume
1. Introduction The action of the wind on the sea generates surface waves and turbulence within the upper ocean. Turbulent mixing leads to the development of a mixed layer (ML) with small vertical gradients in temperature and salinity above the stratified ocean beneath. This simple structure is the basis for mixed layer models of the ocean surface boundary layer (OSBL; Niller and Kraus 1977 ; Garwood 1977 ). In these models, the base of the mixed layer is assumed to be marked by a change in
1. Introduction The action of the wind on the sea generates surface waves and turbulence within the upper ocean. Turbulent mixing leads to the development of a mixed layer (ML) with small vertical gradients in temperature and salinity above the stratified ocean beneath. This simple structure is the basis for mixed layer models of the ocean surface boundary layer (OSBL; Niller and Kraus 1977 ; Garwood 1977 ). In these models, the base of the mixed layer is assumed to be marked by a change in
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
number of authors ( D’Asaro 1985 ; Alford 2001 , 2003b ; Watanabe and Hibiya 2002 ; Jiang et al. 2005 ; Rimac et al. 2013 ) have used the slab model of Pollard and Millard (1970 , hereafter PM70 ) to estimate the work done by the wind on mixed layer inertial motions, in analogy to previous estimates of the work done by the wind on the mean circulation ( Wunsch 1998 ). Global totals range from 0.3 to 1.3 TW, with the spread due to various methods and the temporal and lateral resolution of the
number of authors ( D’Asaro 1985 ; Alford 2001 , 2003b ; Watanabe and Hibiya 2002 ; Jiang et al. 2005 ; Rimac et al. 2013 ) have used the slab model of Pollard and Millard (1970 , hereafter PM70 ) to estimate the work done by the wind on mixed layer inertial motions, in analogy to previous estimates of the work done by the wind on the mean circulation ( Wunsch 1998 ). Global totals range from 0.3 to 1.3 TW, with the spread due to various methods and the temporal and lateral resolution of the
; Thomas et al. 2008 ; Capet et al. 2008 ). Large vertical velocities at the base of the mixed layer can lead to vertical transport of tracers and particles, such as nutrients, dissolved inorganic carbon, oxygen, and particulate organic carbon, between the surface and interior ocean. The vertical exchange can have significant climatological and biological effects ( Mahadevan and Archer 2000 ; Lévy et al. 2001 ; Thomas et al. 2008 ; Lévy et al. 2012a , b ; Mahadevan 2014 ; Omand et al. 2015
; Thomas et al. 2008 ; Capet et al. 2008 ). Large vertical velocities at the base of the mixed layer can lead to vertical transport of tracers and particles, such as nutrients, dissolved inorganic carbon, oxygen, and particulate organic carbon, between the surface and interior ocean. The vertical exchange can have significant climatological and biological effects ( Mahadevan and Archer 2000 ; Lévy et al. 2001 ; Thomas et al. 2008 ; Lévy et al. 2012a , b ; Mahadevan 2014 ; Omand et al. 2015
1. Introduction A typical oceanic stratification and shear allows two types of baroclinic instability ( Boccaletti et al. 2007 , hereafter BFF ): deep mesoscale instabilities spanning the entire depth and shallow submesoscale instabilities trapped in the weakly stratified surface mixed layer (ML). The troposphere and its surface boundary layer provide two analogous types of instability ( Blumen 1979 ; Nakamura 1988 ). The shallow ML instabilities are ageostrophic baroclinic instabilities
1. Introduction A typical oceanic stratification and shear allows two types of baroclinic instability ( Boccaletti et al. 2007 , hereafter BFF ): deep mesoscale instabilities spanning the entire depth and shallow submesoscale instabilities trapped in the weakly stratified surface mixed layer (ML). The troposphere and its surface boundary layer provide two analogous types of instability ( Blumen 1979 ; Nakamura 1988 ). The shallow ML instabilities are ageostrophic baroclinic instabilities
1. Introduction Langmuir circulation (LC), which appears in the form of an array of alternating horizontal roll vortices with axes aligned roughly with the wind, represents one of the most important characteristics of the ocean mixed layer (see, e.g., Leibovich 1983 ; Smith 2001 ; Thorpe 2004 ). The prevailing theory of LC is that of Craik and Leibovich (1976) , which describes the formation of LC in terms of instability brought on by the interaction of the Stokes drift with the wind
1. Introduction Langmuir circulation (LC), which appears in the form of an array of alternating horizontal roll vortices with axes aligned roughly with the wind, represents one of the most important characteristics of the ocean mixed layer (see, e.g., Leibovich 1983 ; Smith 2001 ; Thorpe 2004 ). The prevailing theory of LC is that of Craik and Leibovich (1976) , which describes the formation of LC in terms of instability brought on by the interaction of the Stokes drift with the wind
