The continuous satellite sea-ice record begins
Passive-microwave sensors give, for the first time, a consistent daily measure of sea-ice extent in both hemispheres regardless of cloud or darkness - which is precisely what makes a polar winter measurable. Everything this Journey can say about how the two hemispheres differ over time rests on this record, and the record is short: it is now several decades long, against a system with variability on decadal and longer scales.
Observed — measured or witnessed, with the observation cited.
Subjects
- Sea Ice · natural phenomenon · Both polar oceans · not located
- Arctic Ocean · maritime region · Arctic
- Antarctica · region · Antarctic
Evidence
Partly verified — Core facts are sourced; some optional detail is deliberately absent.
Sea Ice Index
A continuous, consistently processed record of sea-ice extent in both hemispheres exists from 1979, from which the Arctic September minima of 2007 (approximately 4.2 million km2) and 2012 (approximately 3.4 million km2) and the Antarctic February minima of 2022 and 2023 (the first below 2 million km2 in the record, and lower again the following year) are drawn. V55 VERIFICATION BASIS: nsidc.org was probed during production and refused by the network egress proxy, and the WebSearch budget was exhausted. EVERY NUMERIC VALUE IN THIS RECORD IS APPROXIMATE AND UNCHECKED, given to one or two significant figures for that reason. A curator must replace them with values read from the Sea Ice Index before publication.
National Snow and Ice Data Center (NSIDC), University of Colorado Boulder · continuously updated; record begins 1979 · Partly verified
NSIDC Sea Ice Index, https://nsidc.org/data/seaice_index - daily and monthly Arctic and Antarctic sea-ice extent and concentration from passive-microwave satellite observations
Recorded on Sea Ice
- The International Geophysical Year puts twelve nations on the ice at once
- The Antarctic Treaty is signed at Washington
- The continuous satellite sea-ice record begins
- Vostok records minus 89.2 degrees Celsius
- A long-term decline in krill density is linked to winter sea ice
- The Arctic summer minimum drops far below anything previously observed
- The lowest Arctic sea-ice extent in the satellite record
- The Halley Bay emperor colony fails and does not recover
- Seven Arctic states pause participation in the Arctic Council
- The emperor penguin is listed as threatened under the US Endangered Species Act
- Antarctic sea ice reaches a record low, a year after the previous one
- The Madrid Protocol becomes open to a review conference
Related
Related because they share a subject in the Atlas — never because the text looks similar.
- The Madrid Protocol becomes open to a review conference · 2048 (earliest possible review)
- Antarctic sea ice reaches a record low, a year after the previous one · 2023-02
- The emperor penguin is listed as threatened under the US Endangered Species Act · 2022-10-25
- Seven Arctic states pause participation in the Arctic Council · 2022-03-03
- The Halley Bay emperor colony fails and does not recover · 2016 onward
- The lowest Arctic sea-ice extent in the satellite record · 2012-09
- The Arctic summer minimum drops far below anything previously observed · 2007-09
- A long-term decline in krill density is linked to winter sea ice · 2004