{
  "key": "mld_sigma_theta_0125",
  "slug": "mld_sigma_theta_0125",
  "label": "Mixed-layer depth, sigma-theta increase of 0.125 kg/m3 from 10 m (Levitus 1982)",
  "short_label": "Mixed-layer depth (Δσθ 0.125)",
  "description": "Mixed-layer depth, sigma-theta increase of 0.125 kg/m3 from 10 m (Levitus 1982)",
  "units": "m",
  "units_nerc_p06": "http://vocab.nerc.ac.uk/collection/P06/current/ULAA/",
  "nerc_p01": null,
  "category": {
    "key": null,
    "name": "Physical Oceanography",
    "icon": "cat-physical",
    "realm": "env",
    "order": 1
  },
  "is_unified": false,
  "derivation": "calcofi4db::ctd_mld(criterion = 'sigma_theta', threshold = 0.125, ref_depth = 10) on the 1 m bins; an alternative criterion published beside the headline mld_sigma_theta_002 (questions Q01)",
  "climatology": true,
  "bounds": {
    "valid_min": 0,
    "valid_max": 6500,
    "declared_by": [
      "mld_sigma_theta_0125"
    ]
  },
  "totals": {
    "n_values": 9177,
    "n_samples": 9177,
    "n_roots": 9177,
    "n_datasets": 1,
    "year_min": 1993,
    "year_max": 2026,
    "depth_min_m": null,
    "depth_max_m": null,
    "qual_ok_n": 9177,
    "n_flagged": 0
  },
  "series": [
    {
      "measurement_type": "mld_sigma_theta_0125",
      "dataset_key": "calcofi_ctd-derived",
      "source_column": "sigma_theta_ave",
      "qual_column": null,
      "description": "Mixed-layer depth, sigma-theta increase of 0.125 kg/m3 from 10 m (Levitus 1982)",
      "units": "m",
      "nerc_p01": null,
      "is_canonical": true,
      "n_values": 9177,
      "n_samples": 9177,
      "n_roots": 9177,
      "n_cells": 113,
      "n_cruises": 138,
      "year_min": 1993,
      "year_max": 2026,
      "depth_min_m": null,
      "depth_max_m": null,
      "years": {
        "1993": 130,
        "1994": 262,
        "1995": 260,
        "1996": 313,
        "1997": 281,
        "1998": 408,
        "1999": 260,
        "2000": 257,
        "2001": 251,
        "2002": 257,
        "2003": 312,
        "2004": 325,
        "2005": 276,
        "2006": 306,
        "2007": 280,
        "2008": 278,
        "2009": 303,
        "2010": 289,
        "2011": 309,
        "2012": 267,
        "2013": 313,
        "2014": 238,
        "2015": 297,
        "2016": 327,
        "2017": 316,
        "2018": 286,
        "2019": 226,
        "2020": 225,
        "2021": 251,
        "2022": 210,
        "2023": 307,
        "2024": 261,
        "2025": 224,
        "2026": 72
      },
      "months": [
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        583,
        375,
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        113,
        122,
        1540,
        667,
        117,
        949,
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        25
      ],
      "depth_bands": {
        "0-10": 0,
        "10-50": 0,
        "50-100": 0,
        "100-200": 0,
        "200-500": 0,
        "500-1000": 0,
        "1000-2000": 0,
        "2000+": 0
      },
      "qual": {
        "none": 9177
      },
      "qual_ok_n": 9177,
      "n_flagged": 0,
      "observed": {
        "min": 10.1541117001603,
        "p05": 11.8675010838204,
        "p50": 32.7126436781605,
        "p95": 79.5004864815655,
        "max": 136.438388625592
      },
      "out_of_bounds": {
        "n": 0,
        "min": null,
        "max": null
      },
      "flags": [
        "no_flag_at_grain",
        "no_p01"
      ],
      "grain": "sample"
    }
  ],
  "related": [],
  "flags": [
    "no_label"
  ],
  "face": {
    "kind": "scale",
    "face_of": null,
    "stands_in_note": null,
    "source": "no NERC P01 on this key; shows its own familiar-scale figure only (D3)"
  },
  "method": [
    {
      "dataset_key": "calcofi_ctd-derived",
      "measurement_type": "mld_sigma_theta_0125",
      "platform": "ctd",
      "instrument": "Computed from the CTD profile (1 m bins)",
      "nerc_l22": null,
      "principle": "The mixed-layer depth: the shallowest depth where potential density exceeds its value at the 10 m reference by 0.125 kg/m3 (Levitus 1982) on the 1 m bins; absent where the cast never crosses or does not reach 10 m.",
      "steps": [
        "take sigma-theta at 10 m",
        "find the first depth 0.125 kg/m3 denser"
      ],
      "wavelength_nm": null,
      "precision": null,
      "bibkeys": [
        "levitus1982"
      ],
      "calcofi_org_url": null,
      "text_fragment": null,
      "source": "the record's own derivation (measurement_type.csv)",
      "source_url": null
    }
  ],
  "why": [
    {
      "rank": 1,
      "kind": "authored",
      "text": "The mixed layer is the wind-stirred skin of the ocean above the density step that keeps deeper water from rising into it; how deep it is decides how much light the plankton in it get and whether deep nutrients can reach them, and off California warmer, more layered years have gone with fewer zooplankton.",
      "bibkeys": [
        "roemmich1995"
      ],
      "source_url": null,
      "eov": null,
      "goos_doc": null
    },
    {
      "rank": 2,
      "kind": "authored",
      "text": "There is no single mixed-layer depth: each criterion draws the line at a different density or temperature step from a 10 m reference, so the depths published here differ by design; compare a depth only with one made by the same criterion.",
      "bibkeys": [],
      "source_url": null,
      "eov": null,
      "goos_doc": null
    },
    {
      "rank": 3,
      "kind": "wikipedia",
      "text": "Mixed layer",
      "bibkeys": [],
      "source_url": "https://en.wikipedia.org/wiki/Mixed_layer",
      "eov": null,
      "goos_doc": null
    },
    {
      "rank": 4,
      "kind": "wikipedia",
      "text": "Pycnocline",
      "bibkeys": [],
      "source_url": "https://en.wikipedia.org/wiki/Pycnocline",
      "eov": null,
      "goos_doc": null
    }
  ],
  "grain": "sample"
}