The polar bear (Ursus maritimus) is the apex predator of the Arctic, and largely dependent on sea ice. The expected disappearance of the ice cover of the Arctic seas by the mid-21st century is predicted to cause a dramatic decrease in the global range and population size of the species.
Professor Heikki Seppä from the Department of Geosciences and Geography, University of Helsinki, has together with an international research group published new information on changes in the distribution of polar bears.
“The future of polar bears can be predicted by examining the past. We combined data from the fossil record with modelling of climate and sea ice conditions,” Seppä says.
Polar bears survived the warmest period of the Holocene
According to the study, polar bears have survived even warm periods, but the variation in the distribution of the species has depended on Arctic temperatures and sea ice.
“No polar bear fossils have been found from 8,000–6,000 years ago, the warmest period of the Holocene. They have however been found from 9,000–8,000 and 6,000–5,000 years ago, suggesting that the species likely survived during this period in cold refugia near the East Siberian Sea, northern Greenland and the Canadian archipelago,” Seppä says.
According to prior research, temperatures in the highest latitudes during the warmest period of the Holocene, roughly 9,000–5,000 years ago (Holocene Thermal Maximum, HTM), were 1.5–2.5°C higher and the surface area of Arctic sea ice was likely smaller than today (roughly the late 20th century).
“The newly published study will help in drawing conclusions on the survival strategy of key Arctic mammals during climatic conditions warmer than present,” Seppä says.
Polar bear's range dynamics and survival in the Holocene, Heikki Seppä, Marit-Solveig Seidenkrantz, Beth Caissie, Marc Macias Fauria, Quaternary Science Reviews, 1 October 2023, Elsevier https://www.sciencedirect.com/science/article/pii/S0277379123003256