{
  "key": "pycnocline_depth",
  "slug": "pycnocline_depth",
  "label": "Pycnocline depth: where the buoyancy frequency squared N2 (TEOS-10, 10 m running mean) is greatest between 10 and 200 m",
  "short_label": "Pycnocline depth (max N²)",
  "description": "Pycnocline depth: where the buoyancy frequency squared N2 (TEOS-10, 10 m running mean) is greatest between 10 and 200 m",
  "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_pycnocline(p_min = 10, p_max = 200) on buoyancy_n2: the depth of the largest smoothed N2 in the window (ties to the shallowest), for a cast that starts within 15 m of the surface and reaches 50 m with at least 5 bins in the window (the conditions of the CTD team's F_PycnoclineDepth.m, after Fiedler et al. 2013); the 10 m running mean replaces that script's 10 m centred difference and the draft R script's smoothing spline (questions Q11)",
  "climatology": true,
  "bounds": {
    "valid_min": 10,
    "valid_max": 200,
    "declared_by": [
      "pycnocline_depth"
    ]
  },
  "totals": {
    "n_values": 8525,
    "n_samples": 8525,
    "n_roots": 8525,
    "n_datasets": 1,
    "year_min": 1993,
    "year_max": 2026,
    "depth_min_m": null,
    "depth_max_m": null,
    "qual_ok_n": 8525,
    "n_flagged": 0
  },
  "series": [
    {
      "measurement_type": "pycnocline_depth",
      "dataset_key": "calcofi_ctd-derived",
      "source_column": "temperature_ave; salinity_ave_corr; pressure",
      "qual_column": null,
      "description": "Pycnocline depth: where the buoyancy frequency squared N2 (TEOS-10, 10 m running mean) is greatest between 10 and 200 m",
      "units": "m",
      "nerc_p01": null,
      "is_canonical": true,
      "n_values": 8525,
      "n_samples": 8525,
      "n_roots": 8525,
      "n_cells": 103,
      "n_cruises": 139,
      "year_min": 1993,
      "year_max": 2026,
      "depth_min_m": null,
      "depth_max_m": null,
      "years": {
        "1993": 124,
        "1994": 251,
        "1995": 249,
        "1996": 304,
        "1997": 270,
        "1998": 394,
        "1999": 250,
        "2000": 247,
        "2001": 241,
        "2002": 249,
        "2003": 299,
        "2004": 304,
        "2005": 251,
        "2006": 277,
        "2007": 257,
        "2008": 261,
        "2009": 275,
        "2010": 272,
        "2011": 276,
        "2012": 242,
        "2013": 287,
        "2014": 214,
        "2015": 268,
        "2016": 301,
        "2017": 282,
        "2018": 261,
        "2019": 205,
        "2020": 208,
        "2021": 226,
        "2022": 192,
        "2023": 277,
        "2024": 233,
        "2025": 207,
        "2026": 71
      },
      "months": [
        1550,
        565,
        336,
        1808,
        105,
        108,
        1378,
        616,
        113,
        882,
        1041,
        23
      ],
      "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": 8525
      },
      "qual_ok_n": 8525,
      "n_flagged": 0,
      "observed": {
        "min": 10,
        "p05": 13,
        "p50": 48,
        "p95": 120,
        "max": 200
      },
      "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)"
  },
  "why": [
    {
      "rank": 1,
      "kind": "authored",
      "text": "The pycnocline is the density step that separates the surface layer from the water below; its depth sets how far mixing reaches and where nutrients stop, and it rises toward the coast where upwelling lifts deep water.",
      "bibkeys": [],
      "source_url": null,
      "eov": "Subsurface temperature",
      "goos_doc": "https://goosocean.org/document/17501"
    },
    {
      "rank": 2,
      "kind": "authored",
      "text": "The depth of the greatest static stability, the maximum of the buoyancy frequency squared N² (TEOS-10, a 10 m running mean) between 10 and 200 m, after the CTD team's bottle-era script (Fiedler et al. 2013) modernised with TEOS-10 (Rasmus Swalethorp, SIO, 2026-09-24).",
      "bibkeys": [],
      "source_url": null,
      "eov": "Subsurface temperature",
      "goos_doc": "https://goosocean.org/document/17501"
    },
    {
      "rank": 3,
      "kind": "wikipedia",
      "text": "Pycnocline",
      "bibkeys": [],
      "source_url": "https://en.wikipedia.org/wiki/Pycnocline",
      "eov": "Subsurface temperature",
      "goos_doc": "https://goosocean.org/document/17501"
    }
  ],
  "grain": "sample"
}