Reposted from Dr. Susan Crockford’s Polar Bear Science
Posted on July 12, 2019 |
Summer time sea ice loss is lastly ramping up: first 12 months is disappearing, because it has carried out yearly since ice got here to the Arctic thousands and thousands of years in the past. However crucial misconceptions, fallacies, and disinformation abound concerning Arctic sea ice and polar bear survival. Forward of Arctic Sea Ice Day (15 July), listed below are 10 fallacies that lecturers and fogeys particularly have to find out about.
The cartoon above was carried out by Josh: you may drop off the worth of a beer (or extra) for his efforts right here.
As all the time, please contact me if you want to look at any of the references included on this publish. These references are what make my efforts completely different from the activist group Polar Bears Worldwide. PBI just about by no means present references throughout the content material it supplies, together with materials it presents as ‘instructional’. Hyperlinks to earlier posts of mine that present expanded explanations, photographs, and extra references are offered.
Sea ice background: extent over the past 12 months
Summer time sea ice minimal 2018 (from NSIDC):
Winter sea ice most 2019:
Sea ice at 7 July 2019: early summer season extent
Even if 2019 had the 2nd lowest extent for the month of June since 1979, by early July, there was nonetheless ice adjoining to all main polar bear denning areas throughout the Arctic. In lots of areas, pregnant females that give beginning on land in December come ashore in summer season and keep till their new child cubs are sufficiently old to return with them to the ice the next spring. See Andersen et al. 2012; Ferguson et al. 2000; Garner et al. 1994; Jonkel et al. 1978; Harington 1968; Kochnev 2018; Kolenosky and Prevett 1983; Larsen 1985; Olson et al. 2017; Richardson et al. 2005; Stirling and Andriashek 1992.
Ten fallacies and disinformation about sea ice
1. ‘Sea ice is to the Arctic as soil is to a forest‘. False: this all-or-nothing analogy is an specious comparability. In actual fact, Arctic sea ice is sort of a huge wetland pond that dries up a bit each summer season, the place the quantity of habitat obtainable to maintain aquatic vegetation, amphibians and bugs is diminished however doesn’t disappear utterly. Wetland species are tailored to this habitat: they can survive the diminished water availability within the dry season as a result of it occurs yearly. Equally, sea ice will all the time reform within the winter and keep till spring. Throughout the two million or so years that ice has shaped within the Arctic, there has all the time been ice within the winter and spring (even in hotter Interglacials than this one). Furthermore, I’m not conscious of a single fashionable local weather mannequin that predicts winter ice will fail to develop over the subsequent 80 years or so. See Amstrup et al. 2007; Durner et al. 2009; Gibbard et al. 2007; Polak et al. 2010; Stroeve et al. 2007.
2. Polar bears want summer season sea ice to outlive. False: polar bears which have fed adequately on younger seals within the early spring can stay off their fats for 5 months or extra till the autumn, whether or not they spend the summer season on land or the Arctic pack ice. Polar bears seldom catch seals in the summertime as a result of solely predator-savvy grownup seals can be found and holes within the pack ice enable the seals many alternatives to flee (see the BBC video under). Polar bears and Arctic seals actually require sea ice from late fall by means of early spring solely. See Crockford 2017, 2019; Hammill and Smith 1991:132; Obbard et al. 2016; Pilfold et al. 2016; Stirling 1974; Stirling and Øritsland 1995; Whiteman et al. 2015.
Three. Ice algae is the premise for all Arctic life. Solely partially true: plankton additionally thrives in open water in the course of the Arctic summer season, which in the end supplies meals for the fish species that ringed and bearded seals rely on to fatten up earlier than the lengthy Arctic winter. Latest analysis has proven that much less ice in summer season has improved ringed and bearded seal well being and survival over situations that existed within the 1980s (when there was a shorter ice-free season and fewer fish to eat): as a consequence, ample seal populations have been a boon for the polar bears that rely on them for meals in early spring. For instance, regardless of dwelling with probably the most profound decline of summer season sea ice within the Arctic polar bears within the Barents Sea round Svalbard are thriving, as are Chukchi Sea polar bears – each opposite to predictions made in 2007 that resulted in polar bears being declared ‘threatened’ with extinction beneath the Endangered Species Act. See Aars 2018; Aars et al. 2017; Amstrup et al. 2007; Arrigo and van Dijken 2015; Crawford and Quadenbush 2013; Crawford et al. 2015; Crockford 2017, 2019; Frey et al. 2018; Kovacs et al. 2016; Lowry 2016; Regehr et al. 2018; Rode and Regehr 2010; Rode et al. 2013, 2014, 2015, 2018.
four. Open water in early spring in addition to summer season ice soften since 1979 are unnatural and detrimental to polar bear survival. False: melting ice is a traditional a part of the seasonal modifications within the Arctic. Within the winter and spring, numerous areas of open water seem as a result of wind and currents rearrange the pack ice – this isn’t soften, however quite regular polynya formation and growth. Polynyas and widening shore leads present a helpful mixture of ice resting platform and nutrient-laden open water that pulls Arctic seals and supplies wonderful searching alternatives for polar bears. The map under reveals Canadian polynyas and shore leads identified within the 1970s : comparable patches of open water routinely develop in spring off japanese Greenland and alongside the Russian coast of the Arctic Ocean. See Dunbar 1981; Grenfell and Maykut 1977; Hare and Montgomery 1949; Smith and Rigby 1981; Stirling and Cleator 1981; Stirling et al. 1981, 1993.
Recurring polynyas and shore leads in Canada identified within the 1970s. From Smith and Rigby 1981
5. Local weather fashions do a great job of predicting future polar bear habitat. False: My current e-book, The Polar Bear Disaster That By no means Occurred, explains that the virtually 50% decline in summer season sea ice that was not anticipated till 2050 really arrived in 2007, the place it has been ever since (but polar bears are thriving). That’s an awfully unhealthy observe file of sea ice prediction. Additionally, opposite to predictions made by local weather modelers, first 12 months ice has already changed a lot of the multi-year ice within the southern and japanese portion of the Canadian Arctic Archipelago, to the advantage of polar bears. See additionally ACIA 2005; Crockford 2017, 2019; Durner et al. 2009; Hamilton et al. 2014; Heide-Jorgensen et al. 2012; Perovich et al. 2018; Stern and Laidre 2016; Stroeve et al. 2007; SWG 2016; Wang and Overland 2012.
Simplified predictions vs. observations as much as 2007 offered by Stroeve et al. 2007 (courtesy Wikimedia). Sea ice hit a fair decrease extent in 2012 and all years since then have been under predicted ranges.
6. Sea ice is getting thinner and that’s an issue for polar bears. False: First 12 months ice (lower than about 2 metres thick) is the very best behavior for polar bears as a result of it is usually the very best habitat for Arctic seals. Very thick multi-year ice that has been changed by first 12 months ice that melts utterly each summer season creates extra good habitat for seals and bears within the spring, once they want it probably the most. This has occurred particularly within the southern and japanese parts of the Canadian Arctic Archipelago (see ice chart under from Sept 2016). Due to such modifications in ice thickness, the inhabitants of polar bears in Kane Basin (off NW Greenland) has greater than doubled for the reason that late 1990s. See Atwood et al. 2016; Durner et al. 2009; Lang et al. 2017; Stirling et al. 1993; SWG 2016.
7. Polar bears in Western and Southern Hudson Bay are most vulnerable to extinction as a consequence of international warming. False: Ice decline in Hudson Bay has been among the many lowest throughout the Arctic. Sea ice decline in Hudson Bay (see graphs under) has been lower than at some point per 12 months since 1979 in comparison with greater than four days per 12 months within the Barents Sea. Hudson Bay ice decline additionally uniquely occurred as a sudden step-change in 1998: there has not been a sluggish and regular decline. Since 1998, the ice-free season in Western Hudson Bay has been about Three weeks longer total than it was within the 1980s however has not change into any longer over the past 20 years regardless of declines in complete Arctic sea ice extent or elevated carbon dioxide emissions. See Castro de la Guardia et al. 2017; Regehr et al. 2016.
Lack of summer season sea ice per 12 months, 1979-2014. From Regehr et al. 2016.
eight. Breakup of sea ice in Western Hudson Bay now happens three weeks sooner than it did within the 1980s. False: Breakup now happens about 2 weeks earlier in summer season than it did within the 1980s. The overall size of the ice-free season is now about Three weeks longer (with plenty of year-to-year variation). See Castro de la Guardia et al. 2017; Cherry et al. 2013; Lunn et al. 2016; and vidoe under, displaying the primary bear noticed off the ice at Cape Churchill, Western Hudson Bay, on 5 July 2019 – fats and wholesome after consuming nicely in the course of the spring:
9. Winter sea ice has been declining since 1979, placing polar bear survival in danger. Solely partially true: whereas sea ice in winter (i.e. March) has been declining progressively since 1979 (see graph under from NOAA), there isn’t a proof to counsel this has negatively impacted polar bear well being or survival, because the decline has been fairly minimal. The ocean ice chart originally of this publish reveals that in 2019 there was loads of ice remaining in March to satisfy the wants of polar bears and their main prey (ringed and bearded seals), regardless of it being the seventh lowest since 1979.
10. Consultants say that with 19 completely different polar bear subpopulations throughout the Arctic, there are “19 sea ice situations enjoying out“ (see additionally right here), implying that is what they predicted all alongside. False: With a view to predict the long run survival of polar bears, biologists on the US Geological Survey in 2007 grouped polar bear subpopulations with comparable sea ice varieties (which they known as ‘polar bear ecoregions,’ see map under). Their predictions of polar bear survival had been based mostly on assumptions of how the ice in these 4 sea ice areas would change over time (with areas in purple and inexperienced being equally extraordinarily susceptible to results of local weather change). Nevertheless, it seems that there’s far more variation than they anticipated: opposite to predictions, the Barents Sea has had a far larger decline in summer season ice extent than some other area, and each Western and Southern Hudson Bay have had comparatively little (see #7). See Amstrup et al. 2007; Crockford 2017, 2019; Durner et al. 2009; Atwood et al. 2016; Regehr et al. 2016.
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