{
  "key": "nitracline_depth",
  "slug": "nitracline_depth",
  "label": "Nitracline depth: where nitrate reaches 1 umol/L, interpolated between the bracketing samples",
  "short_label": "Nitracline depth (1 µmol/L)",
  "description": "Nitracline depth: where nitrate reaches 1 umol/L, interpolated between the bracketing samples",
  "units": "m",
  "units_nerc_p06": "http://vocab.nerc.ac.uk/collection/P06/current/ULAA/",
  "nerc_p01": null,
  "category": {
    "key": null,
    "name": "Nutrients & Chemistry",
    "icon": "cat-nutrients",
    "realm": "env",
    "order": 2
  },
  "is_unified": false,
  "derivation": "calcofi4db::profile_threshold_depth(threshold = 1, direction = 'above'): the shallowest sample at or above 1 umol/L, the depth interpolated linearly from the sample above it; a profile already at 1 umol/L in its first sample counts only when that sample is within 20 m of the surface; absent where nitrate never reaches 1 umol/L. The provider's rule (Rasmus Swalethorp 2026-09-24 and his D_NClineDepth.m, questions Q10). calcofi_ctd-derived: on the 1 m bins of the bottle-fitted sensor estimate est_nitrate_sta_corr, final and preliminary_with_bottle casts. calcofi_bottle-derived: on the bottle database's nitrate at the bottle depths of each cast",
  "climatology": true,
  "bounds": {
    "valid_min": 0,
    "valid_max": 6500,
    "declared_by": [
      "nitracline_depth"
    ]
  },
  "totals": {
    "n_values": 4060,
    "n_samples": 4060,
    "n_roots": 4060,
    "n_datasets": 1,
    "year_min": 2004,
    "year_max": 2026,
    "depth_min_m": null,
    "depth_max_m": null,
    "qual_ok_n": 4060,
    "n_flagged": 0
  },
  "series": [
    {
      "measurement_type": "nitracline_depth",
      "dataset_key": "calcofi_ctd-derived",
      "source_column": "est_nitrate_sta_corr",
      "qual_column": null,
      "description": "Nitracline depth: where nitrate reaches 1 umol/L, interpolated between the bracketing samples",
      "units": "m",
      "nerc_p01": null,
      "is_canonical": true,
      "n_values": 4060,
      "n_samples": 4060,
      "n_roots": 4060,
      "n_cells": 105,
      "n_cruises": 67,
      "year_min": 2004,
      "year_max": 2026,
      "depth_min_m": null,
      "depth_max_m": null,
      "years": {
        "2004": 63,
        "2005": 237,
        "2006": 190,
        "2007": 247,
        "2008": 175,
        "2009": 288,
        "2010": 229,
        "2011": 275,
        "2012": 254,
        "2013": 272,
        "2014": 226,
        "2015": 257,
        "2016": 265,
        "2017": 256,
        "2018": 253,
        "2019": 208,
        "2020": 142,
        "2021": 63,
        "2025": 105,
        "2026": 55
      },
      "months": [
        754,
        207,
        210,
        827,
        45,
        86,
        652,
        214,
        0,
        313,
        752,
        0
      ],
      "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": 4060
      },
      "qual_ok_n": 4060,
      "n_flagged": 0,
      "observed": {
        "min": 1,
        "p05": 1,
        "p50": 7,
        "p95": 96.5437566137566,
        "max": 152.51572327044
      },
      "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": "Nitrate is used up in the sunlit surface layer; the nitracline is where it reappears, and a shallow nitracline means nutrients within reach of light and so of phytoplankton, which is why it tracks upwelling and El Niño off California.",
      "bibkeys": [],
      "source_url": null,
      "eov": "Nutrients",
      "goos_doc": "https://goosocean.org/document/17509"
    },
    {
      "rank": 2,
      "kind": "authored",
      "text": "The depth at which nitrate reaches 1 µmol/L, interpolated between the two samples that bracket it; the CTD version uses the bottle-fitted sensor estimate, the bottle version the bottle database itself (Rasmus Swalethorp, SIO, 2026-09-24).",
      "bibkeys": [],
      "source_url": null,
      "eov": "Nutrients",
      "goos_doc": "https://goosocean.org/document/17509"
    },
    {
      "rank": 3,
      "kind": "wikipedia",
      "text": "Nutricline",
      "bibkeys": [],
      "source_url": "https://en.wikipedia.org/wiki/Nutricline",
      "eov": "Nutrients",
      "goos_doc": "https://goosocean.org/document/17509"
    }
  ],
  "grain": "sample"
}