Posted onJune 8, 2021|Comments Off on Polar bear habitat in Canada at the first week of June sees widening of critical polynyas
Winds primarily cause the apparent sea ice ‘breakup’ in late spring through the widening of persistent polynyas and shore leads. This year the development of critical open water areas in Canada (which are important feeding areas for polar bears) is on track with previous years in most areas, although there is a lot of year-to-year variability.
Posted onMay 30, 2018|Comments Off on Does thick first year ice on Hudson Bay mean a late date ashore for WH polar bears in 2018?
Following up on my previous post, it appears sea ice conditions on Hudson Bay this year might be headed for a late breakup due to the dominance of thick first year ice. That would mean a relatively longer on-ice season for polar bears in Western and Southern Hudson Bay.
As of the 1st week in May 2018, most of Hudson Bay, Foxe Basin and Hudson Strait were covered with thick 1st year ice (dark green, >1.2 m thick):
Compare that to the 1st week of May 2016, which had much less thick first year ice than 2018 and more medium first year ice (70-120cm, bright green):
To update the situation, at the end of May this year (week of 28 May), thick first year ice covered even more of the bay with a large patch of open water in the NW corner:
Thick first year ice does not melt as quickly as medium or thin first year ice (lime green) under most conditions, so the amount of thick first year ice present in May strongly affects the rate of breakup of the ice over the summer (temperature and wind also contribute). Here are some charts of ice melt sequences from the past (2016 and a couple others) that give a hint at what might be in store for Hudson Bay polar bears this year.
Posted onMay 21, 2015|Comments Off on Arctic polynyas and sea ice extent in Canada at 20 May 2015
The map of sea ice extent in Canada at 20 May 2015 is an almost-perfect example of the placement of recurring patches of open water polynyas that were present in the Canadian Arctic at this time of year in 1975-1979. Notes from field work on shore leads in Hudson Bay ice at May, 1948 offer further insight into the current pattern of sea ice cover on the bay.
May is traditionally the time when recurring polynyas in the Canadian Arctic become more prominent and persistent shore leads (cracks in the ice near shore, also called “flaw leads”) become wider. Polar bears hunt around these polynyas because ringed and bearded seals congregate around them in the spring (Stirling et al. 1981; Stirling 1997). These polynyas are often not truly “open water” but covered by thin ice that’s easy for seals to break through.
This suggests that while sea ice cover over Hudson Bay and the Beaufort Sea is now a bit below average for this time of year (as the maps for this week show), it does not necessarily portend an earlier breakup or longer open-water period later in the year.
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