New study finds Arctic sea ice has been thinning over the years – Much less because of that?
In fact Sea ice has become thinner over the years from 2018 to 2021 as recorded by a new study, finally good news for polar bears: less multi-year ice than first-year ice is better for all Arctic cetaceans. For example, polar bears and seals depend on seasonal ice that forms each winter (Atwood et al. 2016; Durner et al. 2009). Perennial ice is simply too thick for any purpose except as a summer shelter for polar bears (any land will do) and a foundation for winter nests, where which the thick ice of the first year will usually also do (Anderson et al. 2012; Rode et al. 2018).
According to Press Release for the new paper (Kacimi and Kwok 2022):
– Multi-year sea ice in the Arctic at the end of the season is about 1.5 feet thinner in 2021 than in 2019
– Sea ice in the Arctic Ocean has lost a third of its volume in the past 18 years
New Arctic snow depths suggest previous estimates of sea ice thickness may have been overestimated
Authors of the article also emphasized that there have been ‘negligible’ changes in the first-year tape over the same period, so it’s just the multi-year tape of change.
But don’t forget that old ice for many years can actually be very thick: 2-4 meterssometimes a little thicker, as well as the ice north of Greenland, maybe up to 20 meters thick.
Sea ice thickness and sea ice age are not the same, but sea ice ages provide a measure for thickness. A study published in 2007 found a significant change in the age of sea ice in the Central Arctic Basin since the mid-1980s. In 1987, 57% of the ice sheets were at least aged. is 5 years, and a quarter of that block is at least 9 years old. As of 2007, only 7% of the ice sheets were at least 5 years old, and almost none of them were at least 9 years old (Maslanik et al., 2007). Multi-year ice cover actually increased between March 2013 and March 2014, thanks to more ice surviving the summer melt than the record-setting summer. 2012. But overall, multi-year sea ice continues to decline in the Arctic (Perovich et al. 2014).
Areas in the central Canadian Arctic where multi-year ice has been largely replaced by first-year ice in recent years (such as Channel M’Clintock and Kane . Basin) has seen polar bear populations increase.
Presenter
Andersen, M., Derocher, AE, Wiig, Ø. and Aars, J. 2012. Polar bears (Ursus maritimus) Maternity den distribution in Svalbard, Norway. Biological Pole 35: 499-508.
Atwood, TC, Marcot, BG, Douglas, DC, et al. 2016. Projecting the relative influence of environmental and anthropogenic stressors on polar bears. Ecosphere 7 (6): e01370. Hole: 10.1002 / ecs2.1370
Durner, GM, Douglas, DC, Nielson, RM, Amstrup, SC, McDonald, TL, et al. 2009. Prediction of polar bear habitat distribution in the 21st century from global climate models. Ecological monograph 79: 25–58.
Kacimi, S. and Kwok, R. 2022. Arctic ice depth, thickness and volume from ICESat-2 and CryoSat-2: 2018–2021. Geophysical research letter 49 (5): e2021GL097448. https://doi.org/10.1029/2021GL097448
Rode, KD, Olsen, J., Eggett, D., et al. 2018. Den phenology and reproductive success of polar bears in one
climate change. Mammalogy Magazine 99 (1): 16-26. https://doi.org/10.1093/jmammal/gyx181
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