Tag Archives: sea ice maximum

Arctic sea ice extent total for March does not equal global polar bear habitat

Only half or less of the estimated 2.6% loss per decade of March sea ice extent since 1979 (Fig. 1, below) represents a decline in polar habitat. That’s because several regions with sea ice that are not home to polar bears, like the Sea of Okhotsk, are included in Arctic sea ice totals.

Figure 1. Average monthly Arctic sea ice extent for March 1979-2015, which includes ice in the Sea of Okhotsk and the Sea of Japan, a decline of 2.6% per decade. NSIDC, March summary 2015.

Figure 1. Average monthly Arctic sea ice extent for March 1979-2015 (which includes ice in the Sea of Okhotsk, the Sea of Japan, and the Baltic, where polar bears do not live), shows a decline of 2.6% per decade. NSIDC, March summary 2015.

Both the Sea of Okhotsk and northern Sea of Japan (Fig. 2) have sea ice in winter (which is included in total Arctic sea ice records) but they are not truly “Arctic” – neither is connected to the Arctic by continuous ice, even when the ice is at its maximum extent (nor is the Baltic Sea — in contrast to Hudson Bay and the east coast of North America, which are connected to the Arctic by continuous ice).

Sea of Okhotsk_1979 March marked_PolarBearScience

Figure 2. Location of the Sea of Okhotsk and Sea of Japan. Insert ice map for March 1979 from NSIDC shows it’s position relative to the Arctic proper.

That lack of connection to Arctic pack ice is probably the main reason that polar bears never colonized the Sea of Okhotsk, even though western Arctic seal species (ringed, bearded, spotted, and ribbon) and Arctic whales  (bowhead and beluga) live there. Polar bears don’t currently live in the Sea of Okhotsk and all evidence suggests they never have.

Sea ice maps show that about half of the total ice extent difference between March 1979 and March 2015 was due to a relatively large decline in sea ice cover for Sea of Okhotsk and northern Sea of Japan — regions without polar bears. Surely no reputable scientist or journalist would suggest that the “record low” maximum ice extent for 2015 has any relevance for polar bear health and survival? [or for Northwest Passage travel, for that matter] Sadly, they would.

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Polar bear habitat update – even more ice this week in the Barents Sea

Polar bear habitat is close to average for this date all over the Arctic this week. Barents Sea pack ice has increased substantially since last week and the ice in Eastern Canada is still well above average (and higher than 1979-early 1980s). Arctic ice has grown since a preemptive call for “the lowest maximum extent on record” was made by NSIDC last week — there is now at least as much ice for this date as there was in 2011 and almost as much as there was last year (2014).

Polar Bear Breaks Ice

Southern Davis Strait polar bears are out feeding on the glut of harp seals in the pack ice off Labrador and Newfoundland (discussed in detail here). One or more bears strayed a bit from the pack and ended up swimming around near the Hibernia oil platform (not far from the ice edge, although the CBC reports didn’t mention that “minor” fact), discussed in this recently updated post (with maps).

Harp seal female with nursing pup, DFO Canada.

Harp seal female with nursing pup, DFO Canada.

Ice maps and graphs below: it’s worth a look.
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Polar bear visiting Hibernia oil platform off Newfoundland was not far from sea ice

Perhaps the folks on the platform couldn’t see it, but sea ice wasn’t far off on Monday when a polar bear came to visit the Hibernia oil platform southeast of St. John’s, Newfoundland. See the map below (composite from Heritage Newfoundland and Canadian Ice Service):

Hibernia platform and sea ice at 23 March 2015_Polarbearscience
UPDATE 26 March 2015: Ian Stirling has added his expert comment on this incident, see below.

UPDATE 28 March 2015: Newfoundland’s Director of Wildlife has commented on this incident, see below.
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Polar bear habitat: Spring 2014 in Eastern Canada was much better than 1969

It was a good year for polar bear habitat in the southern portions of Eastern Canada this spring – surprisingly, much better than it was in 1968 through 1970. And since spring conditions are what really matter to polar bears, this is good news indeed.

Environment Canada’s Canadian Ice Service recently published a nice little summary that has some rather eye-opening graphs. These describe the conditions for polar bears in the southern Davis Strait subpopulation – the one whose population size increased so dramatically between 1974 and 2007 despite lower-than-average ice extent in some years, even while their body condition declined (see here and here).

Environment Canada - Ice maps regions at July 26 2014

[Fitting post for the second anniversary of this blog, I think – more below1]

Note that I’ve added a “Blog Archive” page that lists all of my posts, easier to browse now that there are more than 200 of them.
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NSIDC says the sea ice minimum in 1964 was not different from 1979, 1981, or 2001

I just came across the National Snow and Ice Data Center (NSIDC) “monthly highlights” article for April 2013 (Glimpses of sea ice past), which turned out to be a rather more interesting story than it appeared at first glance.

The article chronicles the details of how NSIDC technicians pieced together photos taken by the Nimbus 1 satellite between August 28 and September 23, 1964 – of both the Arctic and the Antarctic – to create an estimate of sea ice extent at September 1964 for both regions. For the Arctic, this was the yearly minimum; for the Antarctic, the yearly maximum.

NSIDC scientist Walt Meier was part of this effort and he and colleagues Gallaher and Campbell recently published their findings in the journal The Cryosphere (Meier et al. 2013). For the Arctic estimate, they had to add in data from Alaskan and Russian sea ice charts because the 1964 satellite data was not complete. This means the ice extent figure they came up with is not a true ‘satellite only’ figure but a composite one.

One of the things they did in their analysis was to place the 1964 value on a graph of the more recent 1979-2012 data, which really helps put it into perspective (see Fig. 1 below).

Figure 1. This is Fig. 7 from the Meier et al. 2013 paper, to which I’ve added labels. Meier et al. call this a “time series of Arctic September sea ice extent.” The estimate for 1964 is the red dot on the far left (with its error bars), which I’ve circled (I also added the red label for 1964 and the black line). Note the Y-axis on the left goes to 3.0 million km2, not zero. The solid blue line is the monthly average for September from passive microwave data (1979-2012), and the blue dashed lines are a “three-day average of the high and low range of daily extents during the month.” The 1964 estimate of 6.90 ± 0.3 million km2 is just about identical to 1979, 1981, and 2001 and well within the average for 1979-2000. However, it’s significantly lower than the previous estimate of 8.28 million km2 for 1964 made by the UK Hadley Centre in 2003 (Meier et al. 2013:704).

Figure 1. This is Fig. 7 from the Meier et al. 2013 paper, to which I’ve added labels. Meier et al. call this a “time series of Arctic September sea ice extent.” The estimate for 1964 is the red dot on the far left (with its error bars), which I’ve circled (I also added the red label for 1964 and the black line). Note the Y-axis on the left goes to 3.0 million km2, not zero. The solid blue line is the monthly average for September from passive microwave data (1979-2012), and the blue dashed lines are a “three-day average of the high and low range of daily extents during the month.” The 1964 estimate of 6.90 ± 0.3 million km2 is just about identical to 1979, 1981, and 2001 and well within the average for 1979-2000. However, Meier and colleagues note it is significantly lower than the previous estimate of 8.28 million km2 for 1964, made by the UK Hadley Centre in 2003.

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