{
  "id": "2026-10-08-arctic",
  "region": "arctic",
  "status": "published",
  "draftedAt": "2026-10-08",
  "publishedAt": "2026-10-08",
  "dataThrough": "2026-10-06",
  "headline": "Arctic sea ice is below its seasonal average.",
  "value": "19.3",
  "unit": "%",
  "valueLabel": "Below the same-day average",
  "baselineLabel": "1981\u20132010 reference period",
  "copy": "Sea ice covered 5.959 million km\u00b2 on 6 Oct 2026. The reading is still within the historical comparison range used here. Extent describes the area covered by sea ice. This daily comparison helps track the seasonal ice cover; it does not establish changes in thickness, wildlife impacts or a long-term trend.",
  "mapHref": "#extent-title",
  "mapLabel": "Explore the sea-ice record",
  "methodsHref": "/data.html#polar-records",
  "source": "NOAA/NSIDC Sea Ice Index, Version 4",
  "sourceUrl": "https://nsidc.org/data/g02135/versions/4",
  "evidence": {
    "extentMillionKm2": 5.959,
    "date": "2026-10-06",
    "sameDayMean": 7.38825,
    "sampleStandardDeviation": 1.0531765574257297,
    "referenceYears": 28,
    "rangeLower": 5.281896885148541,
    "rangeUpper": 9.49460311485146,
    "rangePosition": "within",
    "differencePercent": -19.34490576252834,
    "dailySource": "https://noaadata.apps.nsidc.org/NOAA/G02135/north/daily/data/N_seaice_extent_daily_v4.0.csv",
    "citedMap": "/briefings/evidence/2026-10-08-arctic-extent.png",
    "retrievedAt": "2026-10-07T16:01:57.835584+00:00"
  },
  "selectionReason": "First editorial example: latest saved hemisphere-wide extent and its existing same-calendar-day comparison.",
  "method": {
    "baseline": "1981\u20132010",
    "method": "Calendar-day mean \u00b1 two sample standard deviations; missing records excluded",
    "limitations": [
      "One daily reading does not establish a long-term trend or a record minimum.",
      "Mean \u00b1 two sample standard deviations describes the reference period; it is not a probability or confidence interval.",
      "Extent is a satellite-derived estimate at the 15% concentration threshold, separate from the OSI SAF map product.",
      "Recent daily values may be revised."
    ]
  },
  "sourceSha256": {
    "polar-data.json": "465697773926b1997e70071e97ebd042235fa118d3271d48572f5ba27b6a3381",
    "sea-ice-comparison.json": "4c5f42d866b874db8d10d94163ddaa88fe582fa967b2582b677ce839db9b0326"
  },
  "editorialAssessment": {
    "analyse": "Arctic sea-ice extent was 5.959 million km\u00b2 on 6 October 2026, 19.3% below the same-calendar-day 1981\u20132010 reference mean.",
    "evaluate": "The central estimate remains inside the descriptive reference range, mean plus/minus two sample standard deviations. This uses 28 valid reference years. The range is not a confidence interval; no source uncertainty interval is available in this saved daily record, and recent values may be revised.",
    "explain": "This tracks seasonal sea-ice coverage. It does not measure thickness or land-ice loss; wildlife effects and a long-term trend cannot be established from this daily comparison."
  },
  "reviewedAt": "2026-10-08",
  "archivedInputs": "/briefings/evidence/2026-10-08-arctic-inputs.json",
  "archivedInputsSha256": "fd63f48029d84119c940f673710c037955589056f834e6bc88b1cff81911d374"
}