Tag Archives: Chukchi

Summer refuge for polar bears in Arctic Basin only 0.3 mkm2 below its possible maximum

At the seasonal minimum 2015, the Arctic Basin was still almost full of sea ice, down only 0.3 mkm2 below the maximum it could ever be.

Healy Aug 24 2015 Polar-Bear III Tim Kenna

Remember that spending the summer in the Arctic Basin for most polar bears is just like sitting on the western shore of Hudson Bay – they are all waiting for the refreeze. In either location, they might find something to eat, they might not.

Below are NSIDC MASIE sea ice maps for 10 April 2015 (as big as it gets, basin filled) vs. 17 September 2015: Continue reading

Designated critical habitat for Alaskan polar bears offers no protection from thick spring ice deaths

The Obama administration is apparently attempting to overturn a previous ruling that rejected proposed Alaskan “critical habitat” for polar bears in 2013 – as if “critical habitat” would protect the bears from the repeated episodes of thick spring ice that develop in this region every 10 years or so.

Polar_Bear_male on sea ice_Alaska Katovik Regehr photo_April 29, 2005_sm labeled

According to a Reuters report today (5 May 2015):

Seeking to reverse a ruling throwing out its designation of critical habitat for polar bears, the Obama administration has defended its decision to list large swathes of the Arctic as necessary for the conservation of the threatened species.

A coalition of oil industry groups and Alaska Natives, represented by Stoel Rives and Holland & Hart, successfully persuaded the U.S. District Court for Alaska to vacate the government’s polar bear habitat designation in 2013.” [my bold]

If they succeed, it would put most of the north coast of Alaska under special ESA rules, as the map below shows (click to enlarge).

Critical habitat Polar Bears US_NorthSlopeOrg map_labeled_PolarBearScience

As I commented previously, regarding the Obama administration’s recommendation to congress that they approve a proposed Arctic wildlife refuge area on Alaska’s North Slope, this move (if implemented) would not protect polar bears from the starvation deaths due to thick spring ice conditions that have occurred in this region for 2-3 years out of every 10 since 1960 at least.

The other issue is how much additional, biologically meaningful protection a critical habitat designation would provide for Southern Beaufort and Chukchi Sea polar bears – over and above that already provided by the Marine Mammal Protection Act.
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Chukchi-Beaufort sea ice atlas: check out polar bear habitat 1850-2013

It’s here – as promised and right on schedule — the sea ice atlas put together by University of Alaska Fairbanks (UAF) now has ice concentration maps for Alaska going back to 1850 — and for every year up to 2013. 

Several examples are included below: August 1850 vs August 1870, and April 1850 vs. April 1920 and April 2012.

For background, see my post announcing the site preview, which was then limited to 1953-2012 data, when it became available in late January.

Sea ice atlas_1850_Aug
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Graphing polar bear population estimates over time

I’ve already commented on the 2013 update of polar bear population status released by the IUCN Polar Bear Specialist Group (PBSG).

However, I thought it might be interesting to graph the changes in global population estimates over time (from 1981-2013) — not just the actual estimates from PBSG status tables (with their min/max error ranges) but those totals plus the so-called “inaccurate” estimates that the PBSG have dropped from their accounts in recent (2005-2013) assessments: Chukchi Sea, East Greenland, Queen Elizabeth Islands (now known as the “Arctic Basin”), and Laptev Sea.

In 2001, those “inaccurate” estimates contributed 5,000-5,400 bears to the global total, but now they’re gone — no bears from those regions contribute to the official totals listed on recent PBSG status tables.

Adding those dropped estimates back into the global totals makes it possible to generate a graph in which the global estimates are truly comparable over time.

To see how the dropped estimates influenced the perception of population change over time, I’ve also graphed the estimates given by the PBSG in their status tables. I’ve combined the two into one image (Fig. 1, click to enlarge) to make comparison easy.

UPDATE 5 December 2014: Links to more recent posts relevant to this issue added below. The most recent numbers, added 31 May 2015, are here.
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Polar bear habitat update for October 31, 2013

Here’s the ground-truth follow-up to my suggestion of what polar bear habitat would likely look like 6 weeks after the minimum extent was reached this year – which was looking then like it would mirror 2009.

You’ll find my discussion, posted on September 22, here. At that point (September 13), ice extent was 5.1 million square kilometers; now it is 9.1 million square kilometers (Fig.1).

Figure 1. Oct 30 2013 Maisie sea ice extent, 9.1 mkm2. This does not take thickness or concentration into account.

Figure 1. Oct 30 2013 Maisie sea ice extent, 9.1 mkm2. Click to enlarge.

Have a look at the maps below: Fig. 2 to see how ice extent at October 31st compares to ice extent at the end of October 2009, and Fig. 3 to see what ice concentrations looked like in the Canadian Arctic.

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Record sea ice loss in 2007 had no effect on polar bears, Chukchi study confirms

One aspect of the recently published study on Chukchi Sea polar bears (Rode et al.2014 [now in print] 2013; see here and here) has not been stressed enough: their finding that the differences in overall condition between bears in the Chukchi and Southern Beaufort Seas came down to disparities in spring feeding opportunities and therefore, the condition of spring sea ice.

The fact that spring — not summer — is the most critical period for polar bears is something I’ve pointed out before (see here and here, for example) but it’s worth repeating at this time of year, when all eyes are on the annual ice minimum. It is often treated as a given that the decline in extent of summer sea ice in the Arctic since 1979 has been detrimental to polar bears. However, this is an assumption that we can now say is not supported by scientific evidence (see summary of that evidence here).

The results published by Rode et al. (2014 2013) not only add further support to the conclusion that declines in summer sea ice have not harmed polar bears, but should put the matter to rest – unless new evidence to the contrary is produced.

Chukchi bears, the report tells us, had more food available in the spring than Southern Beaufort bears (see map below) and this was the primary reason that bears were doing very well in the Chukchi and not quite as well in the Southern Beaufort. And because the polar bears for this study were captured and measured in mid-March to early May, from 2008 to 2011, they reflect spring-time conditions for 2008-2011 as well as year-round conditions from 2007 through 2010.

This means that the annual low ice extent for 2007 (record-breaking at the time), in the fall before this study began, had no discernible negative effect on either Chukchi or Southern Beaufort polar bears – and neither did similarly low annual minimums in two of the three remaining years of the study (Fig 1).

Figure 1. Sea ice extent at August 27, 2007 – the lowest extent that year (downloaded September 15, 2013 from IARC-JAXA, Arctic Sea-ice Monitor). At the time, it was the lowest extent recorded since 1979 (2012 broke that record). This (2007) was the fall before the Rode & Regehr study on Chukchi/Southern Beaufort polar bears began (2008-2011). The ice was almost as low in September 2008 and 2010, while 2009 was more like 2013.

Figure 1. Sea ice extent at August 27, 2007 – the lowest extent that year (downloaded September 15, 2013 from IARC-JAXA, Arctic Sea-ice Monitor). At the time, it was the lowest extent recorded since 1979 (2012 broke that record). This (2007) was the fall before the Rode & Regehr study on Chukchi/Southern Beaufort polar bears began (2008-2011). The ice was almost as low in 2008 and 2010, while 2009 was more like 2013.

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Polar bears have not been harmed by sea ice declines in summer – the evidence

PB  logo colouredThe polar bear biologists and professional activists of the IUCN Polar Bear Specialist Group (PBSG) continue to insist that since 1979 increasingly smaller amounts of Arctic sea ice left at the end of summer (the September ice minimum) have already caused harm to polar bears. They contend that global warming due to CO2 from fossil fuels (“climate warming” in their lexicon) is the cause of this decline in summer ice.

In a recent (2012) paper published in the journal Global Change Biology (“Effects of climate warming on polar bears: a review of the evidence”), long-time Canadian PBSG  members Ian Stirling and Andrew Derocher (both of University of Alberta) summarized their position this way:

“Climate warming is causing unidirectional changes to annual patterns of sea ice distribution, structure, and freeze-up. We summarize evidence that documents how loss of sea ice, the primary habitat of polar bears (Ursus maritimus), negatively affects their long-term survival”

I’ve spent the last year examining their evidence of on-going harm, but in addition, I’ve looked at the evidence (much of it not mentioned in the Stirling and Derocher paper1) that polar bears have either not been harmed by less sea ice in summer or have thrived in spite of it.

This is a summary of my findings. I’ve provided links to my original essays on individual topics, which are fully referenced and illustrated. You are encouraged to consult them for complete details. This synopsis (pdf with links preserved, updated; pdf with links as footnotes, updated) complements and updates a previous summary, “Ten good reasons not to worry about polar bears” (pdf with links preserved; pdf with a foreword by Dr. Matt Ridley, with links as footnotes).

Update 8 September 2013: to include links to my post on the recently published Chukchi population report; updated pdfs have been added above.

Update 22 January 2014: added figure comparing March vs. September sea ice extent using the same scale, from NOAA’s “2014 Arctic Report Card,” discussed here.
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