Jonassen Island
Jonassen Island is a known penguin breeding site in the Northeast Antarctic Peninsula, at 63°33'S 56°41'W. Gentoo penguins have been recorded here.
Species recorded here
The sea around this site, 1979–2024
Averaged over the 38 ocean cells within 100 km, this site carries sea ice for a median of 260 days a year, peaking at a median 88.3% concentration. The fitted change is -18.2 days per decade, but it does not hold when the record is refitted from 1988 onward, so it is not quotable — the satellite before that date reads low at the coast, and every site here is coastal.
134 other known breeding sites lie within 200 km of this one, and the cells this measurement averages over reach 100 km — so this record and theirs are not independent readings of the sea. Thinned so that no two overlap, the 728 measurable sites in this archive become 56 places.
In the 2023 ice year — the last one this archive holds — the sea ice here lasted 176 days, which is this site's 3rd shortest season of 41 and below its own median of 260. It was below the median at 657 of the 728 sites measured here and at 44 of the 56 independent places, which is the most widespread short season in the record: the whole archive is drawn in one frame.
Two limits. This is the sea around the site and never the fast ice on it — at 25 km that is invisible. And the archive ends 2024-12-31, so it is a climate record rather than a current reading.
Why there is no count on this page
Penguins are too small to resolve from orbit. What is visible is the guano stain a colony leaves on the ice, which is why counting from satellite is a colour problem rather than a counting problem — and it is not solved. Our own detector correlates at r = −0.16 against ground counts across eight colonies, which is no relationship at all. Until that is fixed, this site publishes locations and says nothing about numbers. A number we cannot defend would be worse than none.