10 Fallacies About Arctic Sea Ice & Polar Bear Survival

Dr. Susan Crockford’s Polar Bear Science – Re-Blogged From WUWT

Summer sea ice loss is finally ramping up: first year is disappearing, as it has done every year since ice came to the Arctic millions of years ago. But critical misconceptions, fallacies, and disinformation abound regarding Arctic sea ice and polar bear survival. Ahead of Arctic Sea Ice Day (15 July), here are 10 fallacies that teachers and parents especially need to know about.

polar_bear_summer_2-final-2

The cartoon above was done by Josh: you can drop off the price of a beer (or more) for his efforts here.

As always, please contact me if you would like to examine any of the references included in this post. These references are what make my efforts different from the activist organization Polar Bears International. PBI virtually never provide references within the content it provides, including material it presents as ‘educational’. Links to previous posts of mine that provide expanded explanations, images, and additional references are provided.

Sea ice background: extent over the last year

Summer sea ice minimum 2018 (from NSIDC):

masie_all_zoom_4km 2018 Sept 23

Winter sea ice maximum 2019:

masie_all_zoom_4km 2019 March 17

Sea ice at 7 July 2019: early summer extent

masie_all_zoom_4km 2019 July 7

Despite the fact that 2019 had the 2nd lowest extent for the month of June since 1979, by early July, there was still ice adjacent to all major polar bear denning areas across the Arctic. In many regions, pregnant females that give birth on land in December come ashore in summer and stay until their newborn cubs are old enough to return with them to the ice the following 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 comparison. In fact, Arctic sea ice is like a big wetland pond that dries up a bit every summer, where the amount of habitat available to sustain aquatic plants, amphibians and insects is reduced but does not disappear completely. Wetland species are adapted to this habitat: they are able to survive the reduced water availability in the dry season because it happens every year. Similarly, sea ice will always reform in the winter and stay until spring. During the two million or so years that ice has formed in the Arctic, there has always been ice in the winter and spring (even in warmer Interglacials than this one). Moreover, I am not aware of a single modern climate model that predicts winter ice will fail to develop over the next 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.

PolarBearCV1_USGS_2009

2. Polar bears need summer sea ice to survive.  False: polar bears that have fed adequately on young seals in the early spring can live off their fat for five months or more until the fall, whether they spend the summer on land or the Arctic pack ice. Polar bears seldom catch seals in the summer because only predator-savvy adult seals are available and holes in the pack ice allow the seals many opportunities to escape (see the BBC video below). Polar bears and Arctic seals truly require sea ice from late fall through early spring only. 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.

3. Ice algae is the basis for all Arctic life. Only partially true: plankton also thrives in open water during the Arctic summer, which ultimately provides food for the fish species that ringed and bearded seals depend upon to fatten up before the long Arctic winter. Recent research has shown that less ice in summer has improved ringed and bearded seal health and survival over conditions that existed in the 1980s (when there was a shorter ice-free season and fewer fish to eat): as a consequence, abundant seal populations have been a boon for the polar bears that depend on them for food in early spring. For example, despite living with the most profound decline of summer sea ice in the Arctic polar bears in the Barents Sea around Svalbard are thriving, as are Chukchi Sea polar bears – both contrary to predictions made in 2007 that resulted in polar bears being declared ‘threatened’ with extinction under 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.

4. Open water in early spring as well as summer ice melt since 1979 are unnatural and detrimental to polar bear survival. False: melting ice is a normal part of the seasonal changes in the Arctic. In the winter and spring, a number of areas of open water appear because wind and currents rearrange the pack ice – this is not melt, but rather normal polynya formation and expansion. Polynyas and widening shore leads provide a beneficial mix of ice resting platform and nutrient-laden open water that attracts Arctic seals and provides excellent hunting opportunities for polar bears. The map below shows Canadian polynyas and shore leads known in the 1970s : similar patches of open water routinely develop in spring off eastern Greenland and along 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.

Smith and Rigby 1981_Canada polynyas_sm

Recurring polynyas and shore leads in Canada known in the 1970s. From Smith and Rigby 1981

5. Climate models do a good job of predicting future polar bear habitat. False: My recent book, The Polar Bear Catastrophe That Never Happened, explains that the almost 50% decline in summer sea ice that was not expected until 2050 actually arrived in 2007, where it has been ever since (yet polar bears are thriving). That is an extraordinarily bad track record of sea ice prediction. Also, contrary to predictions made by climate modelers, first year ice has already replaced much of the multi-year ice in the southern and eastern portion of the Canadian Arctic Archipelago, to the benefit of polar bears. See also 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.

Arctic_September_Sea_Ice_Extent_NSIDC_Stroeve_Wikimedia_to Sept 2007

Simplified predictions vs. observations up to 2007 provided by Stroeve et al. 2007 (courtesy Wikimedia). Sea ice hit an even lower extent in 2012 and all years since then have been below predicted levels.

6. Sea ice is getting thinner and that’s a problem for polar bears.  False: First year ice (less than about 2 metres thick) is the best habit for polar bears because it is also the best habitat for Arctic seals. Very thick multi-year ice that has been replaced by first year ice that melts completely every summer creates more good habitat for seals and bears in the spring, when they need it the most. This has happened especially in the southern and eastern portions of the Canadian Arctic Archipelago (see ice chart below from Sept 2016). Because of such changes in ice thickness, the population of polar bears in Kane Basin (off NW Greenland) has more than doubled since the late 1990s. See Atwood et al. 2016; Durner et al. 2009; Lang et al. 2017; Stirling et al. 1993; SWG 2016.

Sea ice extent 2016 Sept 10_NSIDC_minimum declared

7. Polar bears in Western and Southern Hudson Bay are most at risk of extinction due to global warming. False: Ice decline in Hudson Bay has been among the lowest across the Arctic. Sea ice decline in Hudson Bay (see graphs below) has been less than one day per year since 1979 compared to more than 4 days per year in the Barents Sea. Hudson Bay ice decline also uniquely happened as a sudden step-change in 1998: there has not been a slow and steady decline. Since 1998, the ice-free season in Western Hudson Bay has been about 3 weeks longer overall than it was in the 1980s but has not become any longer over the last 20 years despite declines in total Arctic sea ice extent or increased carbon dioxide emissions. See Castro de la Guardia et al. 2017; Regehr et al. 2016.

Regehr et al 2016 SH WH BS together

Loss of summer sea ice per year, 1979-2014. From Regehr et al. 2016.

8. Breakup of sea ice in Western Hudson Bay now occurs three weeks earlier than it did in the 1980s. False: Breakup now occurs about 2 weeks earlier in summer than it did in the 1980s. The total length of the ice-free season is now about 3 weeks longer (with lots of year-to-year variation). See Castro de la Guardia et al. 2017; Cherry et al. 2013; Lunn et al. 2016; and vidoe below, showing the first bear spotted off the ice at Cape Churchill, Western Hudson Bay, on 5 July 2019 – fat and healthy after eating well during the spring:

9. Winter sea ice has been declining since 1979, putting polar bear survival at risk. Only partially true: while sea ice in winter (i.e. March) has been declining gradually since 1979 (see graph below from NOAA), there is no evidence to suggest this has negatively impacted polar bear health or survival, as the decline has been quite minimal. The sea ice chart at the beginning of this post shows that in 2019 there was plenty of ice remaining in March to meet the needs of polar bears and their primary prey (ringed and bearded seals), despite it being the 7th lowest since 1979.

arc18_seaice_perovich_fig2

10. Experts say that with 19 different polar bear subpopulations across the Arctic, there are “19 sea ice scenarios playing out“ (see also here), implying this is what they predicted all along. False: In order to predict the future survival of polar bears, biologists at the US Geological Survey in 2007 grouped polar bear subpopulations with similar sea ice types (which they called ‘polar bear ecoregions,’ see map below). Their predictions of polar bear survival were based on assumptions of how the ice in these four sea ice regions would change over time (with areas in purple and green being similarly extremely vulnerable to effects of climate change). However, it turns out that there is much more variation than they expected: contrary to predictions, the Barents Sea has had a far greater decline in summer ice extent than any other region, and both Western and Southern Hudson Bay have had relatively little (see #7). See Amstrup et al. 2007; Crockford 2017, 2019; Durner et al. 2009; Atwood et al. 2016; Regehr et al. 2016.

USGS_pbear_ecoregions_sm

CONTINUE READING –>

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