About
Daily Arctic and Antarctic sea ice extent from NSIDC — for internal review and sharing.
What this version includes
Every panel on the dashboard is finished. Nothing on the main page is a placeholder.
- Sea ice area for Arctic and Antarctic with date and plain comparison to the usual amount for that time of year.
- Days lower than ever on that date — side-by-side Arctic vs Antarctic counts, with a plain definition on the panel.
- Arctic decadal trend and winter maximum (Jan–Apr peak), computed from the same NSIDC download.
- Seasonal chart (monthly means) with Arctic / Antarctic tabs.
- Milestones — winter-max rank and all-time daily minimums per pole.
Not in this version (and why)
- Daily line chart (Charctic-style) — Would plot every day of the current year vs all prior years; v1 uses monthly means for clarity. Data is already in our database.
- NSIDC browse maps / GeoTIFF — Separate image products; not in our CSV pipeline.
- Sea ice thickness (volume) — Copernicus CMEMS needs free registration and NetCDF processing.
- News RSS — Listed in the original plan but not on the dashboard; avoids mixing headlines with extent numbers.
- Regional seas (Beaufort, Ross, etc.) — NSIDC has regional files; deferred for readability.
How we get the data
We download NSIDC Sea Ice Index v4 daily extent and climatology CSV files from NOAA’s public host each day. This is not a map tile or streaming API. Extent is usually about one day behind real time.
“Updated” on the dashboard means we last ran that download and rebuilt the JSON files — not that a satellite measured ice at that exact moment.
Open any ⓘ on the dashboard for what each number means and where it comes from.
How to read the numbers
- Extent (M km²) — area where at least 15% of the ocean surface is covered by sea ice (NSIDC definition). Not the same as ice volume or thickness.
- “Less / more than usual” — compares the latest day to what NSIDC expects for that calendar date (their 1981–2010 reference). Not the same as last year, and not the same as “lowest ever on this date.”
- Days lower than ever on that date — counts days when ice beat every prior year on that calendar date (since 1979). Separate from “less than usual.”
- Winter max (Arctic) — highest extent between 1 January and 30 April; after April this is the final peak for that melt season.
- Seasonal chart — monthly averages; the dashed line uses NSIDC’s daily climatology averaged by month. The footnote about “lowest full-year average” refers to the calendar year with the smallest mean extent, which can differ from the lowest single-day minimum.
- Arctic vs Antarctic — show separate stories; do not average the poles into one “global sea ice” number.