Posted onMay 6, 2022|Comments Off on Ancient polar bear remains explained by sea ice and polynyas: my peer-reviewed paper
My open-access, peer-reviewed paper on the ecology of ancient polar bears in relation to sea ice has just been published in Open Quaternary. It’s called ‘Polar Bear Fossil and Archaeological Records from the Pleistocene and Holocene in Relation to Sea Ice Extent and Open Water Polynyas’.
A unique compilation of more than 104 polar bear skeletal records from the Holocene and late Pleistocene shows that most ancient remainsare associated with existing or ancient open water polynyas or the expansion of sea ice during past cold periods. This big-picture analysis indicates that as they do today, polar bears were most commonly found near polynyas throughout their known historical past because of their need for ice-edge habitats.
Read my longer summary below and download the paper here. This is a much-updated and expanded analysis based on an informal study I did in 2012.
Posted onApril 21, 2018|Comments Off on Less Svalbard polar bear habitat during the early Holocene than now
Svalbard in the western Barents Sea has recently had less sea ice extent than it had in the 1980s, especially in the west and north, but this is not unprecedented.
New evidence from clams and mussels with temperature-sensitive habitat requirements confirm that warmer temperatures and less sea ice than today existed during the early Holocene period about 10.2–9.2 thousand years ago and between 8.2 and 6.0 thousand years ago (based on radio carbon dates) around Svalbard. Barents Sea polar bears almost certainly survived those previous low-ice periods, as they are doing today, by staying close to the Franz Josef Land Archipelago in the eastern half of the region where sea ice is more persistent.
As this sea ice chart for 18 April 2018 shows, ice this month has been virtually absent from the west and north coasts of the Svalbard Archipelago, while Franz Josef Land to the east is surrounded by highly concentrated pack and land-fast ice.
From a new paper by Jan Mangerud and John Svendsen (2018) [my bold]:
Svalbard, located between 74° and 81°N, is the warmest place on Earth at this latitude (Drange et al., 2013). This is because of the North Atlantic Current and large-scale atmospheric circulation which transport warm water and air masses from lower latitudes northwards across the Atlantic and along the coast of Norway to Svalbard (Figure 1). Yet, during the Holocene Thermal Maximum, the climate of Svalbard was considerably warmer than at present.
The transition from Younger Dryas cold to Holocene Thermal Maximum warm conditions took place very rapidly, according to records from nearby Greenland (Taylor et al. 1997), warming in “steps” of about five years each over a period of about 40 years. This was at least as fast, if not faster than, recent Arctic warming between the 1980s and 2015. And since polar bears of the Barents Sea and adjacent Arctic areas appear to have survived this change to Holocence Thermal Maximum conditions, it challenges the notion that recent warming has been (or will be) too fast to allow polar bears to survive without huge changes in their present distribution (Amstrup et al. 2007). Continue reading
Comments Off on Less Svalbard polar bear habitat during the early Holocene than now
Posted onJanuary 24, 2018|Comments Off on Early Holocene polar bear skeleton from Norway vs. other ancient remains
A press release issued yesterday (23 January 2018) by the University of Stavanger tells the story of decades of work on the most complete ancient polar bear skeleton in the world, found in 1976 in southern Norway, that culminated in an articulated museum display. This specimen was described in my research paper, Annotated Map of Ancient Polar Bear Remains of the World (Crockford 2012), which shows how many very early Holocene remains have been found outside current polar bear range.
Posted onApril 3, 2014|Comments Off on Amstrup grasps at straws to defend his polar-bears-are-doomed computer model
Polar bear activist Steven Amstrup made an astonishing statement in an interview earlier this week — he insisted that the current rate of warming in the Arctic is greater than anything polar bears have lived through before. He also said that optimistic comments on the future of polar bears made by geneticist Matt Cronin a few weeks ago were “incautious” and “misleading.”
Previously, I described how a new paper by Cronin and colleagues confirmed that genetic evidence indicates polar bears have been around long enough to have survived several past Interglacial periods that were warmer than today (and therefore, would have had virtually no summer ice). Cronin, not unreasonably, had some critical things to say about computer modeled predictions that polar bears could not survive in an Arctic without summer sea ice.
On Monday, the Anchorage Daily News gave Amstrup a forum to rebuke Cronin for his comments. A similar story was also carried by the Washington Post. [In the same ADN article, geneticist Charlotte Lindqvist, offered an outdated argument against future polar bear survival that I’ll deal with later]
Today, I’ll address Amstrup’s ridiculous assertion that the current rate of warming, attributed by him primarily to human activities rather than natural variation, is something polar bears have never experienced in their evolutionary history (a period of more than 400,000 years!).