Back in the Early Holocene, when CO2 levels were said to be ~255 ppm, Arctic Svalbard was warm enough to accommodate abundant numbers of thermophiles, or warmth-demanding species. Only “remnants” of these species and their habitat exist in today’s much-colder Arctic.
With the exception of a few centuries in recent millennia, today’s Svalbard (Arctic) is the most glaciated it has been in the last 10,000 years (see the blue trend line in the below chart from Brožová et al., 2023).
Image Source: Brožová et al., 2023
This region is today about 6°C colder than it was during the early Holocene (~10,000 to 8,000 years ago), a climatic period scientists characterize as an optimum, or “most favorable,” for a “rich species pool” of thermophiles.
The sea surface temperatures (SSTs) in the western Barents Sea were as warm as 13°C and “sea ice-free during most of the mid-Holocene” (Łącka et al., 2019). In contrast, today’s SST in this region are as cold as they were during the last glacial (2-4°C), when CO2 hovered near 200 ppm. Rapid double-digit SST fluctuations, varying from 3 to 13°C, have been ongoing throughout the Holocene.
Image Source: Łącka et al., 2019
The sea ice in the Barents Sea surrounding Svalbard is today nearly the most extensive (80% coverage) of the last 10,000 years. In contrast, when CO2 levels were below 260 ppm, this region of the Arctic was sea ice-free, or nearly so (Koseoglu, 2019).
Image Source: Koseoglu, 2019
William Barentsz discovered Arctic Svalbard as he sailed through an open-water Arctic Ocean using a wooden boat (with no ice breakers) in early June, 1596.
Image Source: Wikipedia
In September, 2019, the month of the year with least extensive sea ice, 16 scientists needed to be rescued by helicopters because the massive ship they were using to study climate change couldn’t cut through the ice-covered waters near Svalbard.
In the 1500s, the Western Arctic was sea ice free for about 4-5 months of the year. Today – and steadily since 1800 – the Western Arctic is sea ice free only about 2 weeks of the year (Porter et al., 2019).
Image Source: Porter et al., 2019
Finally, according to Rosel et al., 2018, Arctic sea ice was actually thicker in 2015 (1.56 m) and 2017 (1.65 m) than it was in 1955 (0.94 m) in a region north of Svalbard.