Sea ice tracker

Tip: click any legend entry to hide or show that series. The anomaly chart starts with Global only; click Arctic or Antarctic to add them.

Interpretation

Further reading: Zack Labe's climate graphics, with detailed, regularly updated figures on Arctic sea ice (extent, thickness and volume), Arctic temperatures and more.

Extent = total area where sea-ice concentration is at least 15%. Each value is a 5-day trailing mean of daily extent; the newest days are near-real-time and may be revised. Reference period 1981–2010, as used by NSIDC. Data: Sea Ice Index, Version 4 (NSIDC / NOAA), nsidc.org/data/g02135.

Volume = thickness × ice concentration × area, summed over the polar ocean. Model: Mercator Ocean's GLORYS12 global ocean reanalysis (monthly, 1993 to about two months ago), which combines an ocean and sea-ice model with observations, much as ERA5 does for the atmosphere. Satellite: ice thickness from ESA's CryoSat-2 radar altimeter merged with SMOS (thin ice), sampled weekly. Radar cannot see through summer melt ponds, so the satellite record covers only the cold season (Arctic October–April, Antarctic roughly April–October). The shaded band adds up the uncertainty of every grid cell, a cautious upper bound. Antarctic thickness is harder to measure: heavy snow pushes the ice down and floods it. Data: Copernicus Marine Service, data.marine.copernicus.eu.