New proof that polar bears survived 1,600 years of ice-free summers within the early Holocene
New evidence signifies that Arctic areas with the thickest ice at present in all probability melted out yearly throughout the summer season for about 1,600 years throughout the early Holocene (ca. 11.3-9.7k years in the past), making the Arctic nearly ice-free. As I argue in my new book, which means that polar bears and different Arctic species are able to surviving prolonged durations with ice-free summers: in any other case, they might not be alive at present.
Money quote: Right here we present marine proxy proof for the disappearance of perennial sea-ice within the southern Lincoln Sea throughout the Early Holocene, which suggests a widespread transition to seasonal sea-ice within the Arctic Ocean. [Detlef et al. 2023: Abstract]
An illustration of the Last Ice Area within the Arctic, which is at present lined in perennial ice (2-4m thick) that doesn’t soften out each summer season (Moore et al. 2019) from the press launch for a paper by Newton and colleagues (2021):
The Lincoln Sea mentioned within the new paper is withing the LIA, between Greenland and Ellesmere Island, as proven beneath.
The brief animation beneath reveals sea ice thickness from 1979-2022 within the Arctic on the peak of summer season throughout the Final Ice Space was ca. 2.5-4.0m thick, which is thinner and fewer intensive than it was within the Eighties (when it was 4-5m thick or larger). In different phrases, perennial ice is just not gone but.
Determine S5 from the Detlef paper (beneath) reveals that diminished sea ice throughout the early Holocene was widespread, with proof for seasonal ice within the Barents, Beaufort and Laptev Seas in addition to NE Greenland and the Lincoln Sea between northern Greenland and Ellesmere Island.
Proof from a number of sources signifies that the Eemian produced situations even hotter than documented throughout the early Holocene and so they lasted longer, as defined within the glorious abstract by Leonid Polyak and colleagues (2010). Throughout the early portion of the Eemian a minimum of (ca. 130-120k years in the past), summer season temperatures had been about 5–8 levels Celsius hotter than at present and the Arctic was nearly ice-free. At about 120k years in the past, there’s proof from Finland and the Norwegian Sea off Norway {that a} cooling occasion lasting 500-1,000 years broke the lengthy stretch of heat (Helmens et al. 2015).
Not solely did polar bear survive these two prolonged durations when ice-free summers prevailed, however the Eemian heat summers got here solely about 10,000 years after the bears arose as a singular species. This makes polar bear survival by the Eemian much more spectacular than most scientists acknowledge. The polar bears’ ability to store excess energy as fat within the spring and metabolize it later when wanted should have been fine-tuned by pure choice throughout this challlenging time (Crockford 2023).
The truth that polar bears survived each prolonged durations of ice-free summers signifies that their computer-generated prediction of extinction in a barely hotter world are groundless.
References
Crockford, S.J. 2023. Polar Bear Evolution: A Mannequin for How New Species Come up. Amazon Digital Providers, Victoria. https://www.amazon.com/dp/1778038328
Detlef, H., O’Regan, M., Stranne, C. et al. 2023. Seasonal sea-ice within the Arctic’s final ice space throughout the Early Holocene. Communications Earth & Setting 4:86. https://doi.org/10.1038/s43247-023-00720-w
Helmens, Ok.F., Salonen, J.S., Plikk, A. et al. 2015. Main cooling intersecting peak interglacial heat in northern Europe. Quaternary Science Evaluations 122:293-299. http://dx.doi.org/10.1016/j.quascirev.2015.05.018
Moore, G.W.Ok., Schweigher, A., Zhang, J. et al. 2019. Spatiotemporal variability of sea ice within the Arctic’s Final Ice Space. Geophysical Analysis Letters 46(20):11237-11243. https://doi.org/10.1029/2019GL083722
Newton, R., Pfirman, S., Tremblay, L.B. et al. 2021. Defining the “Ice Shed” of the Arctic Ocean’s Final Ice Space and its future evolution. Earth’s Future 9(9):e2021EF001988. https://doi.org/10.1029/2021EF001988
Polyak, L., Alley, R.B., Andrews, J.T., et al. 2010. Historical past of sea ice within the Arctic. Quaternary Science Evaluations 29:1757–1778. https://doi.org/10.1016/j.quascirev.2010.02.010