Western Hudson Bay freeze-up sooner than common for 1980s for the third yr in a row

Reposted from Polar Bear Science

Posted on November 11, 2019 |

That is the third yr in a row that freeze-up of Western Hudson Bay (WH) ice has come sooner than the common of 16 November documented within the 1980s. Experiences by of us on the bottom close to Churchill affirm polar bears are beginning to transfer onto the ocean ice that’s growing alongside the shore after virtually 5 months on land. After 5 good sea ice seasons in a row for WH polar bears, this repeat of an early freeze-up means a sixth good ice season is now doable for 2019-2020.

Sadly for the vacationers, nonetheless, it means the polar bear viewing season in Churchill can be ending early this yr, identical to it did final yr and the yr earlier than.

Polar bear household on the ice off Churchill Manitoba (taken from a helicopter), courtesy Discover.org

When moms with cubs are out on the ice (see photograph above), it’s fairly sure the mass motion from land to sea ice is properly underway as a result of these household models are often the final to depart.

Present ice circumstances

Climate in Churchill was very chilly right now, -36C with the wind chill. The slight moderation in temperature within the forecast for the remainder of this week remains to be very conducive to ice formation:

The Canadian Ice Service charts for 10 November 2018 beneath (the general image and the main points for ice growth in northern Hudson Bay) present the ice circumstances final yr on the time that bears left for the ice:

Beneath is what the ice appears like this yr (11 November 2019): whereas the band of ice isn’t fairly as thick as final yr right now, latest chilly climate has led to strong ice formation alongside the west coast of Hudson Bay and into James Bay (residence to Southern Hudson Bay bears). This ice is assured to widen and thicken over the following few days, placing this yr solely a day or two behind final yr and 2017.

Simply to spherical out the comparability, beneath is the detailed ice growth chart for 11 November 2017:

Freeze-up dates since 1979

Like Andrew Derocher’s pupil Laura Castro de la Guardia, I’m utilizing a definition of “freeze-up” that describes the behaviour of polar bears to newly shaped ice, not the date when fall ice protection on the bay reaches 50% (e.g. Lunn et al. 2016).

In accordance with a recalculation of WH knowledge that goes as much as 2015 and again to 1979 (Castro de la Guardia 2017, see graph beneath), within the 1980s bears left for the ice at freeze-up (10% sea ice protection) about 16 November ± 5 days whereas lately (2004-2008) they left about 24 November ± eight days, a distinction of eight days. In different phrases, the relative change within the dates that WH bears left the shore between the 1980s and up to date years is simply about 1 week (with a number of variation).

Determine Three from Castro de la Guardia (2017) displaying freeze-up and breakup dates and ice-free days 1979-2015 for Western Hudson Bay, displaying that the earliest freeze-up dates since 1979 (high panel) got here on 6 November, Day 310 (in 1991 and 1993).

Due to this fact, freeze-up dates of 10-12 November or so (Day 314-316) for 2017, 2018, and 2019 are among the earliest freeze-up dates recorded since 1979 (the earliest being 6 November, Day 310, in 1991 and 1993), even sooner than the common for the 1980s.

Nearly all Western Hudson Bay bears go away the shore inside about 2 days of sea ice focus reaching 10% (Castro de la Guardia 2017; Cherry et al. 2013), though Southern Hudson Bay bears go away when it reaches about 5%: in different phrases, the bears go as quickly as they probably can.

As I mentioned in 2016 relating to newly-published research (Obbard et al. 2015, 2016) on the standing of Southern Hudson Bay (SH) bears:

“…SH polar bears left the ice (or returned to it) when the common ice cowl close to the coast was about 5%. This discovering is but extra proof that the meteorological definition of “breakup” (date of 50% ice cowl) utilized by many researchers (see dialogue right here) isn’t applicable for describing the seasonal actions of polar bears on and off shore.”

Right here is the week 19 report from the 2018 Churchill Polar Bear Alert Program (November Four-11 — virtually 5 months ashore), confirming that bears had been transferring onto the quickly forming ice by the primary week of November final yr:

For 2019, the city of Churchill is behind of their posting of downside bear stories (the final one listed is 28 October) however I’ll insert the related standing sheets for the season’s finish right here as quickly as they’re obtainable.

My 2017 Southern Hudson Bay submit (with its checklist of references) is value one other search for its dialogue of the next factors: the definition of freeze-up; the connection of official freeze-up and breakup dates to the dates that bears depart; the general well being and survival of Western and Southern Hudson Bay polar bears.

A remaining notice: if PBI spokesperson Amstrup had been proper about his predictions of Arctic sea ice and polar bear survival again in 2007 when he was the pinnacle of the US Geological Survey’s polar bear analysis staff, there can be no polar bears in any respect in Hudson Bay proper now (Crockford 2017, 2019), not a thriving inhabitants of fats, wholesome bears transferring offshore as early as bears did within the 1980s.

References

Castro de la Guardia, L., Myers, P.G., Derocher, A.E., Lunn, N.J., Terwisscha van Scheltinga, A.D. 2017. Sea ice cycle in western Hudson Bay, Canada, from a polar bear perspective. Marine Ecology Progress Sequence 564: 225–233. http://www.int-res.com/abstracts/meps/v564/p225-233/

Cherry, S.G., Derocher, A.E., Thiemann, G.W., Lunn, N.J. 2013. Migration phenology and seasonal constancy of an Arctic marine predator in relation to sea ice dynamics. Journal of Animal Ecology 82: 912-921. http://onlinelibrary.wiley.com/doi/10.1111/1365-2656.12050/summary

Crockford, S.J. 2017. Testing the speculation that routine sea ice protection of Three-5 mkm2 ends in a higher than 30% decline in inhabitants dimension of polar bears (Ursus maritimus). PeerJ Preprints 2 March 2017. Doi: 10.7287/peerj.preprints.2737v3 Open entry. https://peerj.com/preprints/2737/

Crockford, S.J. 2019. The Polar Bear Disaster That By no means Occurred. International Warming Coverage Basis, London. Out there from Amazon in paperback and e-book codecs.

Lunn, N.J., Servanty, S., Regehr, E.V., Converse, S.J., Richardson, E. and Stirling, I. 2016. Demography of an apex predator on the fringe of its vary – impacts of fixing sea ice on polar bears in Hudson Bay. Ecological Functions 26(5): 1302-1320. DOI: 10.1890/15-1256

Obbard, M.E., Stapleton, S., Middel, Okay.R., Thibault, I., Brodeur, V. and Jutras, C. 2015. Estimating the abundance of the Southern Hudson Bay polar bear subpopulation with aerial surveys. Polar Biology 38:1713-1725.

Obbard, M.E., Cattet, M.R.I., Howe, E.J., Middel, Okay.R., Newton, E.J., Kolenosky, G.B., Abraham, Okay.F. and Greenwood, C.J. 2016. Developments in physique situation in polar bears (Ursus maritimus) from the Southern Hudson Bay subpopulation in relation to modifications in sea ice. Arctic Science 2: 15-32. DOI: 10.1139/AS-2015-0027

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