Here is the follow-up I promised to my post on the July track map for polar bears being followed by satellite in the Beaufort Sea by the US Geological Survey (USGS) – Ten out of ten polar bears being tracked this summer in the Beaufort Sea are on the ice. See that post for methods and other background on this topic, and some track maps from 2012.
The track map for August was posted on the USGS website on September 4th and is copied here below (Figure 1). The ice moved a bit further offshore during August but not nearly as far as it did in 2012. The ten bears from July were down to eight – their collars might have stopped working or fallen off (most likely), they might have left the area entirely (also possible) or they might have died (the researchers don’t say which).
Figure 1. “Movements of 8 satellite-tagged polar bears for the month of August, 2013. Polar bears were tagged in 2013 on the spring-time sea ice of the southern Beaufort Sea. All 8 of these bears have satellite collar transmitters [i.e., all are females]. Polar bear satellite telemetry data are shown with Ice Analysis charts from 26 August, 2013. Ice Analysis charts are made available by the National Ice Center. The land cover is made available by Natural Earth. Click on the above image to enlarge.” [Note that the dots with the polar bear icons are the end points (end August), while the other end of the string is their position in early August. The yellow dot is behind the purple dot, on shore; two of the bears present in July (see Fig. 2 below) are no longer being tracked – their collars might have stopped working or fallen off (most likely), they might have left the area entirely (also possible) or they might have died. The researchers don’t say.]
So, of the eight polar bears still being followed by USGS researchers in August, three were on shore and five were on the ice. Only time will tell if the three females on shore are pregnant and preparing maternity dens for the winter, but this seems the likely reason they are not on the ice with the others.
I’ll post the track map for September when it is available in early October at the USGS website.
The map for July 2013 is below, for comparison: Continue reading
Posted in Life History, Sea ice habitat
Tagged Alaska Science Center, Beaufort Sea, Chukchi Sea, females with radio collars, Regehr, Rode, satellite radio collars, summer ice minimum, summer sea ice, swimming polar bears, tracking polar bears by satellite, US Fish, us geological survey, USGS
Tracking Beaufort Sea polar bears over the summer — what can it tell us about how important the position of summer sea ice relative to the shoreline in this region is to these bears? Do Beaufort Sea bears get stranded on shore like the polar bears in Davis Strait and Hudson Bay?
Polar bear biologist Eric Regehr (with the US Fish & Wildlife Service, or FWS) has a team working with US Geological Survey researchers (USGS) in the southern Beaufort tracking where adult female polar bears go throughout the year. This is part of on-going research in the Beaufort and Chukchi Sea (see previous post here; see also Fish & Wildlife 2009; Polar Bear News 2010 and 2013; Rode and Regehr 2010, pdfs below; and just out, the “accepted” version of the Rode et al. paper discussed here, and announced in my last post here).
The researchers have been posting a summary map at the end of each month on the USGS website showing the tracks of the females they fitted with radio collars the previous spring — for 2013, and back to 2010. They can’t put collars on male bears because their necks are larger around than their heads, so a collar would just slip off.
I’ve posted the July 2013 track map below, which shows all ten bears out on the ice, and the previous month (June 2013) to compare it to (the August map should be out shortly). I’ve included a few maps from 2012 to allow you to compare this year’s results to the situation last summer.
The August tracks should be available after the Labour Day weekend – check back next week to see where the bears have been this month. I’ll post the map here or you can go to the USGS website directly. [UPDATE Sept 4, 2013: The August map is up, posted here.]
Posted in Life History, Sea ice habitat
Tagged Alaska Science Center, Beaufort Sea, Chukchi Sea, Davis Strait, females with radio collars, Hudson Bay, Regehr, Rode, satellite radio collars, summer ice minimum, summer sea ice, swimming polar bears, tracking polar bears by satellite, US Fish & Wildlife, USGS
The most recent issue of Arctic Sea Ice News provided by the National Snow and Ice Data Center (NSIDC) – the official US keeper of sea ice data – (July 17, 2013) included an interesting graph of sea ice extent in the Chukchi and Beaufort Seas at July 12.
They present the data for 2007 to 2013, compared to the new 30 year average1, and note that the Beaufort Sea had “the most extensive ice cover seen there in the last seven summers.” It is also clear from their graph that the 2013 extent was virtually identical to the average in both regions (Fig. 1).
Figure 1. Graph of sea ice extent at July 12 each year from 2007 to 2013 from the National Snow and Ice Data Center, NSIDC. “Climatology” (last set of bars) is the 30 year average (1981-2010) extent at this date.1 It is clear from the graph that the 2013 extent was virtually identical to the 30-year average. Map from Wikipedia.
What puzzled me was why they featured only the last 7 years when satellite data go back to at least 1979. Is there something in that data they don’t want us to see?
There is no similar data in graph form available that I could find but there is the wonderful comparative sea ice mapping tool provided by Cryosphere Today, operated by the University of Illinois.
So, in the absence of numerical data to compare to the Fig. 1 graph, I chose visual data to ask the question: what could there be about the long-term record of Chukchi/Beaufort sea ice data that the NSIDC might not want us to know?
The ice coverage at mid-summer (July 12) provides a snapshot of what sea ice conditions are like for polar bears before the summer melt season gets into full swing, so this historical perspective is quite revealing. [See previous posts here, here, and here for more on Chukchi/Beaufort polar bears.]
This is a short follow-up to my last post on Davis Strait polar bears.
Today I’ll highlight a paper published last year (Rode et al. 2012) that had three of the same co-authors as the Peacock et al. (2012) paper I discussed on Monday – Lily Peacock, Mitch Taylor, and Ian Stirling contributed to both papers. Rode et al. (2012) deals with the issue of body condition (relative degree of fatness) in polar bears vs. changing levels of sea ice over time, and if you’ll pardon the pun, adds even more weight to the conclusion that declines in summer sea ice do not necessarily spell the disaster for polar bears we have been told is inevitable.
A polar bear in the summer of 2012 near Thule, NW Greenland (part of the Baffin Bay subpopulation). Note the decidedly chubby back end on this bear, who looks well prepared for winter. Photo by Robin Davies.
[details at my Quote Archive, Featured Quote #6]
Posted in Population, Sea ice habitat
Tagged arctic sea ice, baffin bay, body condition, Davis Strait, Hudson Bay, Peacock, polar bear numbers, polar bear population density, relative fatness, robin davies, Rode, sea ice concentration, sea ice conditions, Stirling, summer sea ice, Taylor
I’ve said it before but it’s worth saying again now that the sea ice in the Arctic is approaching its seasonal maximum extent and thickness: polar bears are limited by winter sea ice extent (Fig.1), not by the minimum extent of ice in the summer. Otherwise, their distribution would resemble the summer sea ice minimum (Fig. 2), not the winter maximum.
Despite the hue and cry about “declining sea ice,” polar bears are still as well distributed throughout their available winter habitat as they were in 1979, when detailed sea ice records began – see the map below. See further details on polar bear distribution here.
Figure 1. Polar bear distribution map (adapted from the one provided by the PBSG) compared to sea ice concentration at Feb 28 (at or near the seasonal maximum extent) 1979 and 2013. I can’t see a difference – can you see a difference? The only place there is consistently sea ice in winter but not polar bears is the Sea of Okhotsk, but there is no evidence that polar bears have ever lived there despite the presence of seals. Click to enlarge