Okjökull (, Ok glacier) was a glacier in western Iceland on top of the shield volcano Ok.
Ok is located north-east of ReykjavÃÂk. The glacier was declared dead in 2014 by glaciologist Oddur Sigurðsson due to its loss of thickness. Ice crystals in glaciers collapse under their own weight to form solid ice capable of movement due to central gravitational pressure only when the ice is around 40 to 50 metres thick. By 2017 its thickness no longer met this criterion. Its surface area had declined from size at the start of the twentieth century to about in 2015.
In 2018, anthropologists Cymene Howe and Dominic Boyer of Rice University filmed a documentary about its loss, Not Ok, and proposed a commemorative plaque. The plaque was installed on August 18, 2019, with an inscription written by Andri Snær Magnason, titled "A letter to the future", in Icelandic and English. The English version reads:
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At the end is the global atmospheric carbon dioxide reading for that month: 415 ppm. The ceremony was attended by KatrÃÂn Jakobsdóttir, the Prime Minister of Iceland; Guðmundur Ingi Guðbrandsson, the Environment Minister; and Mary Robinson, the former President of Ireland. The placement of the plaque is intended to raise awareness of the decline of Iceland's glaciers due to global warming. Prior to the ceremony, NASA Earth Observatory tweeted images of Okjökull in 1986 and 2019.