Tag Archives: spring ice

Polar bear habitat update: Masie charts show more ice in 2017 than 2006

It’s just an observation but NSIDC Masie ice charts show 14.7 mkm2 of sea ice for 2017 at 19 February (Day 50) but only 14.3 mkm2 for 2006 (see them copied below).

In contrast, the NSIDC interactive graph shows almost the opposite: 14.3 mkm2 for 2017 and 14.4 mkm2 for 2006 (but with both below 2 standard deviations of average).

sea-ice-at-19-feb-2017_vs-2006_nsidc-interactive

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Challenging polar bear fearmongering about Arctic sea ice extent for March 2015

Here are some facts to counter the misinformation and fearmongering being spread via twitter by a polar bear biologist who is getting carried away with his conservation activism.

Arctic Sea ice extent March greater than PB habitat_April 12 2015

Following up on my last post, I note that Arctic regions with sea ice but not polar bears were about 0.32 mkm2 below last year’s March average extent – which means the total ice decline from 2014 (0.4 mkm2) represents only a slight decline in polar bear habitat, most of which is in the Barents Sea (and due primarily to the state of the AMO, not global warming).

Sea ice extent for the Sea of Okhotsk and Baltic Sea combined (both areas without polar bears)1 were about 0.6 mkm2 below average this year for March. Average extent for March (according to NSIDC) is 15.5 mkm2, which means this year’s extent (14.4 mkm2) was 1.1 mkm2 below average, of which less than half (0.5 mkm2) was “lost” polar bear habitat.

IUCN Polar Bear Specialist Group biologist Andrew Derocher has been saying this is a “huge loss for polar bears” (see below): rational analysis of the facts show it is not. Continue reading

What polar bear habitat could look like in another 5-6 weeks

According to the National Snow and Ice Data Center (NSIDC, Sept. 20 report), the annual sea ice minimum extent was reached on Sept. 13, 2013.

At 5.10 million square kilometers, this year’s low was a whopping 1.69 million square kilometers above the minimum extent for 2012 (which was the lowest since 1979) and well within two standard deviations of the 1979-2010 average. (Two standard deviations: “Measurements that fall far outside of the two standard deviation range or consistently fall outside that range suggest that something unusual is occurring that can’t be explained by normal processes”).

The minimum extent for 2013 is virtually indistinguishable from the minimum for 2009, which was 5.13 million square kilometers. The ice was distributed a bit differently in 2009 – more in the east and less in the west — than it was this year (see Fig. 1 below).

Figure 1. Using the JAXA “Sea ice monitor” feature, I plotted the date the 2013 minimum was reached (September 13, 5.10 million square kilometers, white) with an overlay (purple) for the same date back in 2009 (September 13, 2009, 5.13 million square kilometers), when that year’s minimum was reached (according to the NSIDC report). Areas of overlap are pink.

Figure 1. I used JAXA to plot the date the 2013 minimum was reached (September 13, 5.10 million square kilometers, white) with an overlay (purple) for the same date back in 2009 (September 13, 2009, 5.13 million square kilometers), when that year’s minimum was reached. Areas of overlap are pink.

You’ll know from previous discussions here that the annual minimum reached in late summer has little impact on polar bear health and survival (see excellent summary of the evidence for that here). What matters most to polar bears is the presence of ample ice in spring and early summer (March-June), which is their critical feeding period.

But after the fast that many polar bears endure over the height of the summer, they are eager to get back onto the ice and resume hunting. When in the fall does that become possible?

I wondered what the similarity in extent for 2013 and 2009 might tell us about polar bear habitat development over the next month or so.

In other words, what might polar bears this year expect in the way of sea ice development by say, the end of October? When might they be able to start hunting?

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Biologists spreading misinformation: hybridization with grizzlies not due to polar bears moving inland

A paper published last week in the journal Science, written by a team of biologists and atmospheric scientists, expounds on a possible dire future for a range of Arctic animals. It’s called, “Ecological consequences of sea-ice decline” and surprisingly, polar bears are discussed only briefly.

However, with the inclusion of one short sentence, the paper manages to perpetuate misinformation on grizzly/polar bear hybridization that first appeared in a commentary essay three years ago in Nature  (Kelly et al. 2010)1. The Post et al. 2013 missive contains this astonishing statement (repeated by a Canadian Press news report):

Hybridization between polar bears and grizzly bears may be the result of increasing inland presence of polar bears as a result of a prolonged ice-free season.

Lead author of the paper, Professor of Biology Eric Post, is quoted extensively in the press release issued by his employer (Penn State University, pdf here). In it, Post re-states the above sentence in simpler terms, removing any doubt of its intended interpretation:

“… polar and grizzly bears already have been observed to have hybridized because polar bears now are spending more time on land, where they have contact with grizzlies.

Both statements are patently false. All recent hybridization events documented (2006-2013) occurred because a few male grizzlies traveled over the sea ice into polar bear territory and found themselves a polar bear female to impregnate (see news items here and here, Fig. 1 below). These events did not occur on land during the ice-free season (which is late summer/early fall), but on the sea ice in spring (March-May).

Grizzlies have been documented wandering over the sea ice of the western Arctic since at least 1885 (Doupe et al. 2007; Fig. 2, below) and the presence in this region of hybrid grizzly/polar bear offspring is not an indicator of declining summer sea ice, whether due to global warming or natural causes, or some combination thereof.

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