Mixed layer

Last updated August 13, 2024

Depth of Mixed Layer versus the month of the year, along with relationship to temperature MixedLayerMonth.png — Depth of Mixed Layer versus the month of the year, along with relationship to temperature

The oceanic or limnological mixed layer is a layer in which active turbulence has homogenized some range of depths. The surface mixed layer is a layer where this turbulence is generated by winds, surface heat fluxes, or processes such as evaporation or sea ice formation which result in an increase in salinity. The atmospheric mixed layer is a zone having nearly constant potential temperature and specific humidity with height. The depth of the atmospheric mixed layer is known as the mixing height. Turbulence typically plays a role in the formation of fluid mixed layers.

Oceanic mixed layer

Importance of the mixed layer

The mixed layer plays an important role in the physical climate. Because the specific heat of ocean water is much larger than that of air, the top 2.5 m of the ocean holds as much heat as the entire atmosphere above it. Thus the heat required to change a mixed layer of 2.5 m by 1 °C would be sufficient to raise the temperature of the atmosphere by 1 °C. The depth of the mixed layer is thus very important for determining the temperature range in oceanic and coastal regions. In addition, the heat stored within the oceanic mixed layer provides a source for heat that drives global variability such as El Niño.

The mixed layer is also important as its depth determines the average level of light seen by marine organisms. In very deep mixed layers, the tiny marine organisms known as phytoplankton are unable to get enough light to maintain their metabolism. The deepening of the mixed layer in the wintertime in the North Atlantic is therefore associated with a strong decrease in surface chlorophyll a. However, this deep mixing also replenishes near-surface nutrient stocks. Thus when the mixed layer becomes shallow in the spring, and light levels increase, there is often a concomitant increase of phytoplankton biomass, known as the "spring bloom".

Oceanic mixed layer formation

There are three primary sources of energy for driving turbulent mixing within the open-ocean mixed layer. The first is the ocean waves, which act in two ways. The first is the generation of turbulence near the ocean surface, which acts to stir light water downwards.^[1] Although this process injects a great deal of energy into the upper few meters, most of it dissipates relatively rapidly.^[2] If ocean currents vary with depth, waves can interact with them to drive the process known as Langmuir circulation, large eddies that stir down to depths of tens of meters.^[3]^[4] The second is wind-driven currents, which create layers in which there are velocity shears. When these shears reach sufficient magnitude, they can eat into stratified fluid. This process is often described and modelled as an example of Kelvin-Helmholtz instability, though other processes may play a role as well. Finally, if cooling, addition of brine from freezing sea ice, or evaporation at the surface causes the surface density to increase, convection will occur. The deepest mixed layers (exceeding 2000 m in regions such as the Labrador Sea) are formed through this final process, which is a form of Rayleigh–Taylor instability. Early models of the mixed layer such as those of Mellor and Durbin included the final two processes. In coastal zones, large velocities due to tides may also play an important role in establishing the mixed layer.

The mixed layer is characterized by being nearly uniform in properties such as temperature and salinity throughout the layer. Velocities, however, may exhibit significant shears within the mixed layer. The bottom of the mixed layer is characterized by a gradient, where the water properties change. Oceanographers use various definitions of the number to use as the mixed layer depth at any given time, based on making measurements of physical properties of the water. Often, an abrupt temperature change called a thermocline occurs to mark the bottom of the mixed layer; sometimes there may be an abrupt salinity change called a halocline that occurs as well. The combined influence of temperature and salinity changes results in an abrupt density change, or pycnocline. Additionally, sharp gradients in nutrients (nutricline) and oxygen (oxycline) and a maximum in chlorophyll concentration are often co-located with the base of the seasonal mixed layer.

Oceanic mixed layer depth determination

The depth of the mixed layer is often determined by hydrography—making measurements of water properties. Two criteria often used to determine the mixed layer depth are temperature and sigma-t (density) change from a reference value (usually the surface measurement). The temperature criterion used in Levitus^[5] (1982) defines the mixed layer as the depth at which the temperature change from the surface temperature is 0.5 °C. However, work done by Kara et. al. (2000) suggest that the temperature difference is closer to .8 °C.^[6] The sigma-t (density) criterion used in Levitus^[5] uses the depth at which a change from the surface sigma-t of 0.125 has occurred. Neither criterion implies that active mixing is occurring to the mixed layer depth at all times. Rather, the mixed layer depth estimated from hydrography is a measure of the depth to which mixing occurs over the course of a few weeks.

An example of barrier layer thickness for an Argo profile taken January 31, 2002 in the tropical Indian Ocean. The red line is the density profile, black line is temperature, and the blue line is salinity. One mixed layer depth, D_T-02, is defined as the depth at which the surface temperature cools by 0.2°C (black dashed line). The density defined mixed layer, D_sigma, is 40 m (red dashed line) and is defined as the surface density plus the density difference brought about by the temperature increment of 0.2°C. Above D_sigma the water is both isothermal and isohaline. The difference between D_T-02 minus D_sigma is the barrier layer thickness (blue arrows on the figure) .

Barrier layer thickness

The barrier layer thickness (BLT) is a layer of water separating the well-mixed surface layer from the thermocline.^[7] A more precise definition would be the difference between mixed layer depth (MLD) calculated from temperature minus the mixed layer depth calculated using density. The first reference to this difference as the barrier layer was in a paper describing observations in the western Pacific as part of the Western Equatorial Pacific Ocean Circulation Study.^[8] In regions where the barrier layer is present, stratification is stable because of strong buoyancy forcing associated with a fresh (i.e. more buoyant) water mass sitting on top of the water column.

In the past, a typical criterion for MLD was the depth at which the surface temperature cools by some change in temperature from surface values. For example, Levitus^[5] used 0.5 °C. In the example to the right, 0.2 °C is used to define the MLD (i.e. D_T-02 in the Figure). Prior to the abundant subsurface salinity available from Argo, this was the main methodology for calculating the oceanic MLD. More recently, a density criterion has been used to define the MLD. The density-derived MLD is defined as the depth where the density increases from the surface value due to a prescribed temperature decrease of some value (e.g. 0.2 °C) from the surface value while maintaining constant surface salinity value. (i.e. D_T-02 - D_sigma).

BLT regimes

Large values of the BLT are typically found in the equatorial regions and can be as high as 50 m. Above the barrier layer, the well mixed layer may be due to local precipitation exceeding evaporation (e.g. in the western Pacific), monsoon related river runoff (e.g. in the northern Indian Ocean), or advection of salty water subducted in the subtropics (found in all subtropical ocean gyres). Barrier layer formation in the subtropics is associated with seasonal change in the mixed layer depth, a sharper gradient in sea surface salinity (SSS) than normal, and subduction across this SSS front.^[9] In particular, the barrier layer is formed in winter season in the equatorward flank of subtropical salinity maxima. During early winter, the atmosphere cools the surface and strong wind and negative buoyancy forcing mixes temperature to a deep layer. At this same time, fresh surface salinity is advected from the rainy regions in the tropics. The deep temperature layer along with strong stratification in the salinity gives the conditions for barrier layer formation.^[10]

For the western Pacific, the mechanism for barrier layer formation is different. Along the equator, the eastern edge of the warm pool (typically 28 °C isotherm - see SST plot in the western Pacific) is a demarcation region between warm fresh water to the west and cold, salty, upwelled water in the central Pacific. A barrier layer is formed in the isothermal layer when salty water is subducted (i.e. a denser water mass moves below another) from the east into the warm pool due to local convergence or warm fresh water overrides denser water to the east. Here, weak winds, heavy precipitation, eastward advection of low salinity water, westward subduction of salty water and downwelling equatorial Kelvin or Rossby waves are factors that contribute to deep BLT formation.^[11]

Importance of BLT

Prior to El Nino, the warm pool stores heat and is confined to the far western Pacific. During the El Nino, the warm pool migrates eastward along with the concomitant precipitation and current anomalies. The fetch of the westerlies is increased during this time, reinforcing the event. Using data from the ship of opportunity and Tropical Atmosphere – Ocean (TAO) moorings in the western Pacific, the east and west migration of the warm pool was tracked over 1992-2000 using sea surface salinity (SSS), sea surface temperature (SST), currents, and subsurface data from Conductivity, temperature, depth taken on various research cruises.^[12] This work showed that during westward flow, the BLT in the western Pacific along the equator (138^oE-145^oE, 2^oN-2^oS) was between 18 m – 35 m corresponding with warm SST and serving as an efficient storage mechanism for heat. Barrier layer formation is driven by westward (i.e. converging and subducting) currents along the equator near the eastern edge of the salinity front that defines the warm pool. These westward currents are driven by downwelling Rossby waves and represent either a westward advection of BLT or a preferential deepening of the deeper thermocline versus the shallower halocline due to Rossby wave dynamics (i.e. these waves favor vertical stretching of the upper water column). During El Nino, westerly winds drive the warm pool eastward allowing fresh water to ride on top of the local colder/saltier/denser water to the east. Using coupled, atmospheric/ocean models and tuning the mixing to eliminate BLT for one year prior to El Nino, it was shown that the heat buildup associated with barrier layer is a requirement for big El Nino.^[13] It has been shown that there is a tight relationship between SSS and SST in the western Pacific and the barrier layer is instrumental in maintaining heat and momentum in the warm pool within the salinity stratified layer.^[14] Later work, including Argo drifters, confirm the relationship between eastward migration of the warm pool during El Nino and barrier layer heat storage in the western Pacific.^[15] The main impact of barrier layer is to maintain a shallow mixed layer allowing an enhanced air-sea coupled response. In addition, BLT is the key factor in establishing the mean state that is perturbed during El Nino/La Niña ^[16]

Limnological mixed layer formation

Formation of a mixed layer in a lake is similar to that in the ocean, but mixing is more likely to occur in lakes solely due to the molecular properties of water. Water changes density as it changes temperature. In lakes, temperature structure is complicated by the fact that fresh water is heaviest at 3.98 °C (degrees Celsius). Thus in lakes where the surface gets very cold, the mixed layer briefly extends all the way to the bottom in the spring, as surface warms as well as in the fall, as the surface cools. This overturning is often important for maintaining the oxygenation of very deep lakes.

The study of limnology encompasses all inland water bodies, including bodies of water with salt in them. In saline lakes and seas (such as the Caspian Sea), mixed layer formation generally behaves similarly to the ocean.

Atmospheric mixed layer formation

The atmospheric mixed layer results from convective air motions, typically seen towards the middle of the day when air at the surface is warmed and rises. It is thus mixed by Rayleigh–Taylor instability. The standard procedure for determining the mixed layer depth is to examine the profile of potential temperature, the temperature which the air would have if it were brought to the pressure found at the surface without gaining or losing heat. As such an increase of pressure involves compressing the air, the potential temperature is higher than the in-situ temperature, with the difference increasing as one goes higher in the atmosphere. The atmospheric mixed layer is defined as a layer of (approximately) constant potential temperature, or a layer in which the temperature falls at a rate of approximately 10 °C/km, provided it is free of clouds. Such a layer may have gradients in the humidity, though. As is the case with the ocean mixed layer, velocities will not be constant throughout the atmospheric mixed layer.

Related Research Articles

<span class="mw-page-title-main">North Atlantic Deep Water</span> Deep water mass formed in the North Atlantic Ocean

North Atlantic Deep Water (NADW) is a deep water mass formed in the North Atlantic Ocean. Thermohaline circulation of the world's oceans involves the flow of warm surface waters from the southern hemisphere into the North Atlantic. Water flowing northward becomes modified through evaporation and mixing with other water masses, leading to increased salinity. When this water reaches the North Atlantic, it cools and sinks through convection, due to its decreased temperature and increased salinity resulting in increased density. NADW is the outflow of this thick deep layer, which can be detected by its high salinity, high oxygen content, nutrient minima, high ¹⁴C/¹²C, and chlorofluorocarbons (CFCs).

Downwelling is the downward movement of a fluid parcel and its properties within a larger fluid. It is closely related to upwelling, the upward movement of fluid.

El Niño–Southern Oscillation (ENSO) is a global climate phenomenon that emerges from variations in winds and sea surface temperatures over the tropical Pacific Ocean. Those variations have an irregular pattern but do have some semblance of cycles. The occurrence of ENSO is not predictable. It affects the climate of much of the tropics and subtropics, and has links (teleconnections) to higher-latitude regions of the world. The warming phase of the sea surface temperature is known as "El Niño" and the cooling phase as "La Niña". The Southern Oscillation is the accompanying atmospheric oscillation, which is coupled with the sea temperature change.

Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters.

Thermohaline circulation (THC) is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, factors which together determine the density of sea water. Wind-driven surface currents travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes. This dense water then flows into the ocean basins. While the bulk of it upwells in the Southern Ocean, the oldest waters upwell in the North Pacific. Extensive mixing therefore takes place between the ocean basins, reducing differences between them and making the Earth's oceans a global system. The water in these circuits transport both energy and mass around the globe. As such, the state of the circulation has a large impact on the climate of the Earth.

<span class="mw-page-title-main">Thermocline</span> Distinct layer of temperature change in a body of water

A thermocline is a distinct layer based on temperature within a large body of fluid with a high gradient of distinct temperature differences associated with depth. In the ocean, the thermocline divides the upper mixed layer from the calm deep water below.

The surface layer is the layer of a turbulent fluid most affected by interaction with a solid surface or the surface separating a gas and a liquid where the characteristics of the turbulence depend on distance from the interface. Surface layers are characterized by large normal gradients of tangential velocity and large concentration gradients of any substances transported to or from the interface.

Sea surface temperature is the temperature of ocean water close to the surface. The exact meaning of surface varies in the literature and in practice. It is usually between 1 millimetre (0.04 in) and 20 metres (70 ft) below the sea surface. Sea surface temperatures greatly modify air masses in the Earth's atmosphere within a short distance of the shore. Local areas of heavy snow can form in bands downwind of warm water bodies within an otherwise cold air mass. Warm sea surface temperatures can develop and strengthen cyclones over the ocean. Tropical cyclones can also cause a cool wake. This is due to turbulent mixing of the upper 30 metres (100 ft) of the ocean. Sea surface temperature changes during the day. This is like the air above it, but to a lesser degree. There is less variation in sea surface temperature on breezy days than on calm days. The thermohaline circulation has a major impact on average sea surface temperature throughout most of the world's oceans.

The Pacific decadal oscillation (PDO) is a robust, recurring pattern of ocean-atmosphere climate variability centered over the mid-latitude Pacific basin. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20°N. Over the past century, the amplitude of this climate pattern has varied irregularly at interannual-to-interdecadal time scales. There is evidence of reversals in the prevailing polarity of the oscillation occurring around 1925, 1947, and 1977; the last two reversals corresponded with dramatic shifts in salmon production regimes in the North Pacific Ocean. This climate pattern also affects coastal sea and continental surface air temperatures from Alaska to California.

A pycnocline is the cline or layer where the density gradient is greatest within a body of water. An ocean current is generated by the forces such as breaking waves, temperature and salinity differences, wind, Coriolis effect, and tides caused by the gravitational pull of celestial bodies. In addition, the physical properties in a pycnocline driven by density gradients also affect the flows and vertical profiles in the ocean. These changes can be connected to the transport of heat, salt, and nutrients through the ocean, and the pycnocline diffusion controls upwelling.

The North Brazil Current (NBC) is a warm water ocean current that is part of the southwestern North Atlantic Gyre. It begins when the westward moving Atlantic South Equatorial Current splits in half and flows northwestward, following the coastline of north Brazil. It ends at the border of Brazil and Guiana, where it is renamed the Guiana Current. It is predominantly a salt water current, but it does help transport fresh water from the Amazon River northward.

Ocean stratification is the natural separation of an ocean's water into horizontal layers by density, which is generally stable because warm water floats on top of cold water, and heating is mostly from the sun, which reinforces that arrangement. Stratification is reduced by wind-forced mechanical mixing, but reinforced by convection. Stratification occurs in all ocean basins and also in other water bodies. Stratified layers are a barrier to the mixing of water, which impacts the exchange of heat, carbon, oxygen and other nutrients. The surface mixed layer is the uppermost layer in the ocean and is well mixed by mechanical (wind) and thermal (convection) effects. Climate change is causing the upper ocean stratification to increase.

Ocean heat content (OHC) or ocean heat uptake (OHU) is the energy absorbed and stored by oceans. To calculate the ocean heat content, it is necessary to measure ocean temperature at many different locations and depths. Integrating the areal density of a change in enthalpic energy over an ocean basin or entire ocean gives the total ocean heat uptake. Between 1971 and 2018, the rise in ocean heat content accounted for over 90% of Earth's excess energy from global heating. The main driver of this increase was caused by humans via their rising greenhouse gas emissions. By 2020, about one third of the added energy had propagated to depths below 700 meters.

The West Spitsbergen Current (WSC) is a warm, salty current that runs poleward just west of Spitsbergen,, in the Arctic Ocean. The WSC branches off the Norwegian Atlantic Current in the Norwegian Sea. The WSC is of importance because it drives warm and salty Atlantic Water into the interior Arctic. The warm and salty WSC flows north through the eastern side of Fram Strait, while the East Greenland Current (EGC) flows south through the western side of Fram Strait. The EGC is characterized by being very cold and low in salinity, but above all else it is a major exporter of Arctic sea ice. Thus, the EGC combined with the warm WSC makes the Fram Strait the northernmost ocean area having ice-free conditions throughout the year in all of the global ocean.

Tropical instability waves, often abbreviated TIW, are a phenomenon in which the interface between areas of warm and cold sea surface temperatures near the equator form a regular pattern of westward-propagating waves. These waves are often present in the Atlantic Ocean, extending westward from the African coast, but are more easily recognizable in the Pacific, extending westward from South America. They have an average period of about 30 days and wavelength of about 1100 kilometers, and are largest in amplitude between June and November. They are also largest during La Niña conditions, and may disappear when strong El Niño conditions are present.

Sea ice is a complex composite composed primarily of pure ice in various states of crystallization, but including air bubbles and pockets of brine. Understanding its growth processes is important for climate modellers and remote sensing specialists, since the composition and microstructural properties of the ice affect how it reflects or absorbs sunlight.

The Barrier layer in the ocean is a layer of water separating the well-mixed surface layer from the thermocline.

Cyclonic Niño is a climatological phenomenon that has been observed in climate models where tropical cyclone activity is increased. Increased tropical cyclone activity mixes ocean waters, introducing cooling in the upper layer of the ocean that quickly dissipates and warming in deeper layers that lasts considerably more, resulting in a net warming of the ocean.

Stratification in water is the formation in a body of water of relatively distinct and stable layers by density. It occurs in all water bodies where there is stable density variation with depth. Stratification is a barrier to the vertical mixing of water, which affects the exchange of heat, carbon, oxygen and nutrients. Wind-driven upwelling and downwelling of open water can induce mixing of different layers through the stratification, and force the rise of denser cold, nutrient-rich, or saline water and the sinking of lighter warm or fresher water, respectively. Layers are based on water density: denser water remains below less dense water in stable stratification in the absence of forced mixing.

Atlantification is the increasing influence of Atlantic water in the Arctic. Warmer and saltier Atlantic water is extending its reach northward into the Arctic Ocean. The Arctic Ocean is becoming warmer and saltier and sea-ice is disappearing as a result. The process can be seen on the figure on the far right, where the sea surface temperature change in the past 50 years is shown, which is up to 5 degrees in some places. This change in the Arctic climate is most prominent in the Barents Sea, a shallow shelf sea north of Scandinavia, where sea-ice is disappearing faster than in any other Arctic region, impacting the local and global ecosystem.

References

Mellor, G. L.; Durbin, P. A. (1975). "The structure and dynamics of the ocean surface mixed layer". Journal of Physical Oceanography. 5 (4): 718–728. Bibcode:1975JPO.....5..718M. doi: 10.1175/1520-0485(1975)005<0718:TSADOT>2.0.CO;2 .

↑ Kato, H.; Phillips, O.M. (1969). "On the penetration of a turbulent layer into a stratified fluid". J. Fluid Mech. 37 (4): 643–655. Bibcode:1969JFM....37..643K. doi:10.1017/S0022112069000784. S2CID 122260276.
↑ Agrawal, Y.C.; Terray, E.A.; Donelan, M.A.; Hwang, P.A.; Williams, A.J.; Drennan, W.M.; Kahma, K.K.; Kitaiigorodski, S.A. (1992). "Enhanced dissipation of kinetic energy beneath surface waves". Nature. 359 (6392): 219–220. Bibcode:1992Natur.359..219A. doi:10.1038/359219a0. S2CID 4308649.
↑ Craik, A.D.D.; Leibovich, S. (1976), "A Rational model for Langmuir circulations", Journal of Fluid Mechanics, 73 (3): 401–426, Bibcode:1976JFM....73..401C, doi:10.1017/S0022112076001420, S2CID 18089261
↑ Gnanadesikan, A.; Weller, R.A. (1995), "Structure and variability of the Ekman spiral in the presence of surface gravity waves", Journal of Physical Oceanography, 25 (12): 3148–3171, Bibcode:1995JPO....25.3148G, doi: 10.1175/1520-0485(1995)025<3148:saiote>2.0.co;2
1 2 3 Levitus, Sydney (December 1982). Climatological Atlas of the World Ocean (PDF). NOAA Professional Paper 13. Rockville, Md, USA: U.S. Department of Commerce, National Oceanic and Atmospheric Administration. p. 173. Archived from the original (PDF) on October 12, 2011. Retrieved 29 January 2020.
↑ Kara, A. Birol; Rochford, Peter A.; Hurlburt, Harley E. (2000). "An optimal definition for ocean mixed layer depth". Journal of Geophysical Research: Oceans. 105 (C7): 16803–16821. Bibcode:2000JGR...10516803K. doi: 10.1029/2000JC900072 .
↑ Sprintall, J., and M. Tomczak, Evidence of the barrier layer in the surface-layer of the tropics, Journal of Geophysical Research: Oceans, 97 (C5), 7305-7316, 1992.
↑ Lukas, R.; Lindstrom, E. (1991). "The Mixed Layer of the Western Equatorial Pacific-Ocean". Journal of Geophysical Research: Oceans. 96 (S01): 3343–3357. Bibcode:1991JGR....96.3343L. doi:10.1029/90jc01951.
↑ Sato, K., T. Suga, and K. Hanawa, Barrier layers in the subtropical gyres of the world's oceans, Geophysical Research Letters, 33 (8), 2006.
↑ Mignot, J., C.d.B. Montegut, A. Lazar, and S. Cravatte, Control of salinity on the mixed layer depth in the world ocean: 2. Tropical areas, Journal of Geophysical Research: Oceans, 112 (C10), 2007.
↑ Bosc, C.; Delcroix, T.; Maes, C. (2009). "Barrier layer variability in the western Pacific warm pool from 2000 to 2007" (PDF). Journal of Geophysical Research: Oceans. 114 (C6): C06023. Bibcode:2009JGRC..114.6023B. doi:10.1029/2008jc005187.
↑ Delcroix, T.; McPhaden, M. (2002). "Interannual sea surface salinity and temperature changes in the western Pacific warm pool during 1992-2000". Journal of Geophysical Research: Oceans. 107 (C12): SRF 3-1-SRF 3-17. Bibcode:2002JGRC..107.8002D. doi:10.1029/2001jc000862.
↑ Maes, C.; Picaut, J.; Belamari, S. (2005). "Importance of the salinity barrier layer for the buildup of El Niño". Journal of Climate. 18 (1): 104–118. Bibcode:2005JCli...18..104M. doi: 10.1175/jcli-3214.1 .
↑ Maes, C.; Ando, K.; Delcroix, T.; Kessler, W.S.; McPhaden, M.J.; Roemmich, D. (2006). "Observed correlation of surface salinity, temperature and barrier layer at the eastern edge of the western Pacific warm pool". Geophysical Research Letters. 33 (6): L06601. Bibcode:2006GeoRL..33.6601M. doi: 10.1029/2005gl024772 .
↑ Mignot, J.; Montegut, C.d.B.; Lazar, A.; Cravatte, S. (2007). "Control of salinity on the mixed layer depth in the world ocean: 2. Tropical areas". Journal of Geophysical Research: Oceans. 112 (C10): C10010. Bibcode:2007JGRC..11210010M. doi: 10.1029/2006jc003954 .
↑ Maes, C.; Belamari, S. (2011). "On the Impact of Salinity Barrier Layer on the Pacific Ocean Mean State and ENSO". Scientific Online Letters on the Atmosphere. 7: 97–100. Bibcode:2011SOLA....7...97M. doi: 10.2151/sola.2011-025 .

External links

Lake effect snow for a link to a NASA image from the SeaWiFS satellite showing clouds in the atmospheric mixed layer.
See the Ifremer/Los Mixed Layer Depth Climatology website at Redirection for having access to up to date ocean Mixed Layer Depth Climatology, data, maps and links.