Parameter: depth_mixed_layer

Short Description: mixed layer depth
Short Name: depth_mixed_layer
Official Name: depth_mixed_layer
Units: various
No Data Value: nd
External Identifier: odo:matches: http://vocab.nerc.ac.uk/collection/P01/current/MXLMD01Z/

Description

The mixed-layer depth (MLD)

Note: The calculation used for MLD should be included in the metadata as the methodology for calculating this can vary.  For example, one definition is the maximum depth at which the sea-water density is less than the density at 5m + 0.1 kg m-3.

The mixed-layer is the layer between the ocean surface and a depth usually ranging between 25 and 200m, where the density is about the same as at the surface. The mixed-layer owes its existence to the mixing initiated by waves and turbulence caused by the wind stress on the sea surface. An effect of mixing is to make both properties of water, temperature and salinity, and therefore density, more uniform. The penetration of mixing to a certain depth (the mixed-layer depth) mostly depends on the stability of the sea water and on the incoming energy from the wind. The more stable is the surface water, the less mixing occurs, and the shallower is the mixed-layer. Sea water stability in the near-surface is determined by the atmospheric fluxes through the ocean surface (wind stress, heat and fresh water exchange). A typical unstable configuration is when water is denser (“heavier”) at the surface than below. The mixing that ensues, for example with some impulse from waves or turbulence, renders the density more uniform and deepens the mixed-layer. In certain conditions occurring only in a few areas of the high-latitude seas (e.g. Labrador Sea in North Atlantic, Weddell Sea in the Antarctic waters), instability is so strong that denser surface water literally sinks and mixes over large depths reaching more than 1000m.

In many situations, the mixed-layer can be identified with the layer of mixed temperature, when the salinity does not vary much with increasing depth in general. However, this becomes untrue as soon as for instance fresh water is exchanged between the ocean and the air above (evaporation or rain), which may create large salinity contrast.

The mixed-layer is the oceanic surface zone that responds the most quickly and directly to atmospheric fluxes, and it is through the mixed-layer that such influence is transmitted to the whole ocean in the long term. Conversely, the mixed-layer is the part of the ocean through which the ocean influences directly the atmosphere. Many important processes occur within the mixed-layer, whether physical (e.g. direct wind-forcing of the ocean circulation), chemical (e.g. dissolution of incoming CO2 from the atmosphere), or biological (e.g. phytoplankton production).

Source: http://www.esr.org/outreach/glossary/mixed_layer.html

DatasetPI-Supplied DescriptionPI-Supplied Name
All 7Be data pertaining to upwelling velocity calculations from R/V Yellowfin cruises to the San Pedro Ocean Time-series (SPOT) in 2013 and 2014Mixed layer depth; Oxygen mixed layer depths were determined as the depth at which the oxygen concentration was 0.5% different from the surface concentration. MLD
Processed CTD data with thermodynamic calculations from R/V Atlantic Explorer cruise AE2207 to the Bermuda Atlantic Time Series (BATS) station in April 2022Mixed layer depth using a change in sigma-theta from 10dbar of 0.125 mld
ARISA relative abundances (bacterial community structure), San Pedro Channel, 5 depths, 2014 (Bacterial, Archaeal, and Protistan Biodiversity project, Marine Viral Dynamics project)Mixed layer depth depth_mixlayr
BIOS-SCOPE survey biogeochemical data as collected on Atlantic Explorer cruises (AE1614, AE1712, AE1819, AE1916) from 2016 through 2019 Depth of "active mixing" defined by buoyancy frequency after Mojica & Gaube (see Acquisition description) MLD_bvfrq
BIOS-SCOPE survey biogeochemical data as collected on Atlantic Explorer cruises (AE1614, AE1712, AE1819, AE1916) from 2016 through 2019 Mixed layer depth defined by surface density plus 0.125 kilograms per cubed meter (see Acquisition description) MLD_dens125
BIOS-SCOPE survey biogeochemical data as collected on Atlantic Explorer cruises (AE1614, AE1712, AE1819, AE1916) from 2016 through 2019 MLD from Thermal Expansion Coeff, and dT=0.2 deg C (see Acqusition description) MLD_densT2
Compilation of MULVFS size-fractionated POC, PIC, and bSi data from 17 cruises conducted between 1973 and 2005Mixed Layer Depth, as reported in original reference, or where Δσθ >0.05 kg/m3 MLD
Underway/continuous measurements of O2, O2/Ar and optically-based POC in the North Pacific from 2017-09-05 to 2017-09-27Mixed Layer Depth MLD
Temperature, salinity, fluorescence, and dissolved O2/Ar ratios measured continuously underway onboard basin-wide transects of the North Pacific from Hong Kong to Long Beach, CAClimatological mixed layer depth from monthly World Ocean Atlas 2013 (with 1 degree gridded data), used in calculations MLD_WOA13
Surface and mixed-layer averaged diel cycles of O2 and optically-based POC from repeated CTD casts in the North Pacific from 2017-09-05 to 2017-09-25Mixed layer depth MLD
Mixed layer depths from R/V Tangaroa cruise 61TG_3052 in the Southern Ocean in 1999 (SOIREE project)Mixed Layer Depth Mixed_layer_depth
Discrete O2 Argon (Ar) from NOAA Ship Ronald H. Brown cruise RB-08-02 in the Southwest Atlantic sector of the Southern Ocean near South Georgia Island in 2008 (SO_GasEx project)mixed layer depth for determining kw mixed_layer_depth_used_for_gas_exchange_weighting
Diurnal Gross Oxygen Production (GOP) from NOAA Ship Ronald H. Brown cruise RB-08-02 in the Southwest Atlantic sector of the Southern Ocean near South Georgia Island in 2008 (SO_GasEx project)mixed layer depth from nearest CTD cast mixed_layer_depth
Krill swarms detected with active acoustic EK80 onboard small boat surveys in Palmer Deep Canyon, Antarctica during January-March 2020Mixed layer depth as measured by ACROBAT (associated dataset) mld
Mixed-layer averaged O2 and optically-based POC from Profiling Floats in the North Pacific from R/V Kilo Moana from June to September 2017Mixed Layer Depth MLD
All measurements used in the gross oxygen production estimates; from samples collected on R/V Yellowfin cruises to the San Pedro Ocean Time-series (SPOT) station in 2013 and 2014Mixed layer depth; Oxygen mixed layer depths were determined as the depth at which the oxygen concentration was 0.5% different from the surface concentration. MLD
An ocean productivity database using consistent, globally-acquired data from in situ primary productivity based on 14C assimilation, and including ancillary data, 1985-2008mixed layer depth MLD_meters
Concentration of inorganic nutrients, primary productivity measurements and phytoplankton cell concentration in seawater samples from the Malaspina 2010 Circumnavigation Expedition (VitaMaps project)Mixed Layer Depth MLD
Estimates of mixed layer depths (MLD) mean mixed-layer values of temperature, salinity, and other measurements from R/V Roger Revelle cruise RR2201 in the Eastern Indian Ocean (Argo Basin) from January to March 2022mixed layer depth MLD
Virioplankton abundance using FISH probe at BATS site in the western Sargasso Sea from 2000-2011 (Ocean Microbial Observatory project)mixed layer depth in meters; MLD was determined as the depth where potential density (sigma-t) of the water was equal to sea surface sigma-t plus the equivalent in sigma-t to a 0.2 1C decrease in temperature (Sprintall and Tomczak 1992). depth_mixed
Virioplankton abundance from multiple cruises at the Bermuda AtlanticTime Series Station (BATS), Western Sargasso Sea from 2000-2011 (Ocean Microbial Observatory project)mixed layer depth in meters; MLD was determined as the depth where potential density (sigma-t) of the water was equal to sea surface sigma-t plus the equivalent in sigma-t to a 0.2 1C decrease in temperature (Sprintall and Tomczak 1992). depth_mixed
All measurements used in the net oxygen production estimates from R/V Yellowfin cruises to the San Pedro Ocean Time-series (SPOT) in 2013 and 2014Mixed layer depth; Oxygen mixed layer depths were determined as the depth at which the oxygen concentration was 0.5% different from the surface concentration. MLD
Standing stocks and rates for organic sulfur compounds during summer in the subarctic Northeast PacificMixed layer depth represents the depth of the well-mixed surface layer. The criteria for definining the depth of the mixed layer was a change of more than 0.05 mg/m3 in the density profile from the near-surface average. Mixed_Layer_Depth
Hydrological, biogeochemcial and N2-fixer qPCR-derived abundance data for May 2017 (SP1714) and October (SP1724) SCCS cruises. mixed layer depth mix_layer_depth
Nitrate and Oxygen isotope measurements from CLIVAR line P16S in 2005 from R/V Roger Revelle ZHNG02RR in the A meridional transect from 16 to 71 degrees South along 150 degrees West from January to February 2005 (CAREER project)depth range where active mixing has homogenized the water mixed_layer_depth
Planktic foraminifer tissue and shell d15N from net tows on R/V S.A. Agulhas II cruises VOY016 and VOY019 in the Southern Ocean south of Africa during 2015-2016Calculated mixed layer depth at each profile station, defined as the closest depth to the surface at which potential density is greater by greater than or equal to 0.03 kg/m3 than the value at a reference depth of 11 m (the shallowest depth common to every CTD station), based on the criterion of de Boyer Montégut et al. (2004). MLD_calc
Nitrate+nitrite and nitrate-only d15N from R/V S.A. Agulhas II cruises VOY016 and VOY019 in the Southern Ocean south of Africa during 2015-2016Calculated mixed layer depth at each profile station, defined as the closest depth to the surface at which potential density is greater by greater than or equal to 0.03 kg/m3 than the value at a reference depth of 11 m (the shallowest depth common to every CTD station), based on the criterion of de Boyer Montégut et al. (2004). MLD_calc
Environmental measurements from ARISA samples, San Pedro Channel, 5 depths , 2014 (Bacterial, Archaeal, and Protistan Biodiversity project, Marine Viral Dynamics project)Mixed layer depth depth_mixlayr
Tropical Pacific nitrate N and O isotopes in the tropical Pacific from 2003-2007 (CAREER project, Diatom-bound_N_Isotopes project)mixed layer depth mixed_layer_depth
Underway O2 Argon (Ar) from NOAA Ship Ronald H. Brown cruise RB-08-02 in the Southwest Atlantic sector of the Southern Ocean near South Georgia Island in 2008 (SO_GasEx project)mixed layer depth for determining kw mixed_layer_depth_used_for_gas_exchange_weighting
Wintertime nitrate delta 15N and delta 18O from hydrocasts from R/V S. A. Agulhas II cruise VOY03 in the Southern Ocean south of Africa in 2012 (Diatom-bound_N_Isotopes project)Mixed layer calculated from sigma-t using ref depth = 32 m. Mixed layer depth at each station is defined as the closest depth to the surface at which sigma theta is greater by >= 0.03 kg m-3 than the value at a reference depth of 32 m (the shallowest depth common to every CTD station) (based on the criterion of de Boyer Montégut et al. (2004)). depth_mixed_layer
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