Tracking polar bears in the Beaufort Sea – all bears on the ice in June

The recent open water in the Southern Beaufort didn’t seem to change what polar bears were doing – bears tracked by USGS show them on the ice, likely trying to hunt. More ice edge means more hunting habitat at this time of year.

Beaufort tracking USGS bear-movements-June 2016 lg closeup

However, few hunts are likely successful at this time of year – because only older seals are on the ice and the broken ice makes escape so much easier for the seals (see previous post here). Fat bears on shore this summer (like the ones seen at Kaktovik in September) will tell us that they got enough to eat earlier in the season. Note that bears in good condition that appear at the whaling bone piles in September are there by choice (not stranding) and they got fat by feeding in the spring (March-May), not by picking at leftover whale scraps. Calories from terrestrial sources (for most bears) just reduce the amount of weight they lose over the summer.

More maps below.

The 13 polar bears with tags or collars tracked during April 2016 in the Beaufort Sea were down to 5 females with collars in June (see May map here).

Beaufort tracking USGS bear-movements-June 2016 sm

Original caption: “Movements of 5 satellite-tagged polar bears for the month of June, 2016. Polar bears were tagged in 2015 and 2016 on the spring-time sea ice of the southern Beaufort Sea. All 5 of these bears have satellite collar transmitters. Polar bear satellite telemetry data are shown with MODIS imagery from 1 July, 2016.” See original map here.

Sea ice conditions in perspective

Note the Canadian Ice Service chart below, that shows how much multi-year ice there still was in the Southern Beaufort at the end of June (brown is multi-year ice):

Western Arctic ice stage of development weekly at 4 July 2016

And despite the large patch of open water, the ice that remained was generally high concentrated pack ice, as the chart for 4 July 2016 show (red is 80-100%):

Western Arctic ice concentration weekly at 4 July 2016

The ice coverage for the week of 2 July this year is well below what it has been for past years (except for 1998) but as far as I know, there is nothing in the literature to suggest that 1998 was a catastrophic year for Southern Beaufort polar bears.

Beaufort Sea_same week 2 July 1968-2016

You’ll notice in the graph above that 2007 through 2012 had only a little more ice than 2016 for the first week of July – but all had more ice than was present in 1998.

As the graph below for the Eastern Beaufort at 4 June shows, 1998 had much reduced sea ice as early as May but by early July (above), the amount of open water increased, leaving more than this year (2016). But early expansion of open water in 1998 apparently did not hamper polar bear health or survival (or we would have heard about it from researchers working in the area).

Beaufort Sea_Mackenzie_same week 4 June 1968-2016

Note that the decline in polar bear numbers that took place in the Southern Beaufort was due to well-documented thick sea ice conditions in the springs of 2004-2006, which had similar effects on polar bears as an event that occurred in 1974-1976 (see previous posts here and here for the references).

Ice loss has now slowed in the region, as NSIDC Masie ice maps (below) show. As of 7 July, there was more ice in the Southern Beaufort this year than there was in 2012:

2016 (827 thousand km2):

masie_all_r01_v01_2016189_4km

2012 (803 thousand km2):

masie_all_r01_v01_2012189_4km

Ice conditions as of yesterday (10 July 2016):

Sea ice extent Canada 2016 July 10_CIS

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