{"id":265498,"date":"2023-07-05T12:29:25","date_gmt":"2023-07-05T10:29:25","guid":{"rendered":"https:\/\/climatescience.press\/?p=265498"},"modified":"2023-07-05T12:29:29","modified_gmt":"2023-07-05T10:29:29","slug":"early-sea-ice-breakup-in-w-hudson-bay-caused-by-record-breaking-warmth-in-2023-but-not-2015","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=265498","title":{"rendered":"Early sea ice breakup in W Hudson Bay caused by \u201crecord breaking\u201d warmth in 2023 but not 2015?"},"content":{"rendered":"\n
\"\"<\/figure>\n\n\n\n

<\/p>\n\n\n\n

From polarbearscience<\/a><\/p>\n\n\n\n

According to\u00a0Polar Bears International<\/a>, the \u201c3rd-earliest\u201d breakup date for Western Hudson Bay was caused by a \u201crecord breaking\u201d heat wave in May. Western Hudson Bay sea ice hit the 30% coverage threshold used by PBI to define \u201cbreakup\u201d on 17 June this year, prompting speculation about potential future impacts on polar bear survival should breakup come even earlier.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

\u201cThis year\u2019s break-up date of June 17 is the 3rd earliest in the 45 years of satellite-based sea ice data from Western Hudson Bay, after 2015 and 2003<\/em>.\u201d [Flavio Lehner, PBI<\/a>]<\/p>\n\n\n\n

17 June 2023 is day 168 on the Julian calendar used to graph the data in the image included in the PBI essay (see copy below). However, the data point for 2003 is about three days earlier, on day 166 (14 June) and the point for 2015 is on day 152 (1 June).<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

If \u201crecord-breaking\u201d heat caused this year\u2019s early ice retreat, what caused the ice to retreat\u00a0more than two weeks earlier<\/em>\u00a0in 2015? May was warm that year along the west coast as well but obviously not \u201crecord-breaking\u201d warmth, because the records were broken\u00a0this year<\/em>. In fact, whatever warmth that occurred only affected ice melt in the western sector, while very thick ice over the rest of the bay resisted melt and allowed bears to stay out many weeks later than usual.<\/p>\n\n\n\n

<\/p>\n\n\n\n

Sea ice breakup in 2023<\/strong><\/p>\n\n\n\n

Closest in my archive to 17 June is 19 June (but 15 June isn\u2019t much different along the western portion so it probably didn\u2019t change much between the 17th and 19th). Note how much ice is missing in the eastern bay as well.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

<\/p>\n\n\n\n

Sea ice breakup in 2015<\/strong><\/p>\n\n\n\n

Compare the above to 1 June 2015 (below), when the\u00a0same 30% ice coverage<\/a>\u00a0threshold was apparently reached. Note this is 30% of the Western Hudson Bay region in particular, not Hudson Bay in general. In fact, the ice melt pattern in 2015 was quite unusual, with lots of open water in the western sector but\u00a0thick, solid ice<\/a>\u00a0everywhere else that resisted melt. Despite early melt in Western Hudson Bay,\u00a0at August 13, only 1992 had more ice<\/a>\u00a0remaining in the bay overall.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

At 20 July 2015,\u00a0more than half of collared Southern Hudson Bay bears<\/a>\u00a0were reported still far out on the ice. On the same date (see tweet below), polar bear specialist Andrew Derocher noted that only 2 out of 9 collared bears had come ashore (one way over in Hudson Strait), when the prediction based on 30% WH ice coverage should have seen them all onshore by 30 June (Cherry et al. 2013):<\/p>\n\n\n

\n
\"\"<\/figure>\n<\/div>\n\n\n

According to Cherry et al. (2013):<\/span>

\u201cThroughout the study, bears arrived ashore a mean of 28.3 day (S.E. = 1.8) after 30% ice cover.\u201d<\/em>Thus, according to Cherry\u2019s criteria, this year we should expect most bears to be onshore in WH by 15 July. However, as of 27 June, only 6 of Andrew Derocher\u2019s tagged bears were onshore and the rest (27 of them) were still out on low concentration sea ice (see map below). Several of them are way out in the middle of the bay. Time will tell whether they will all head to shore over the next two weeks or if some will linger a few weeks longer on bits of remnant ice, as\u00a0seems to be the usual pattern\u00a0<\/a>in recent years.<\/p><\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

All this suggests that the 30% ice coverage metric may not be an especially good predictor of polar bear behaviour. That\u2019s not just my opinion: one of Derocher\u2019s students undertook an analysis that came to a similar conclusion.<\/p>\n\n\n\n

Her more recent paper<\/a> (Castro de la Guardia et al. 2017) found that a threshold of 50% ice coverage<\/em> over WH was the best predictor of when polar bears come ashore in the summer:<\/p>\n\n\n\n

\u201cThe most suited definition of breakup was the 50% ice concentration. There was a high positive correlation (r2 > 0.9, p = 0.07) between migration onshore and breakup from 2006 to 2009, with polar bears migrating onshore approximately 20 d after breakup<\/strong>.<\/em>\u201d [Castro de la Guardia et al. 2017, pg. 230, my emphasis]<\/p>\n\n\n\n

If this more recent study, which uses more data and a 50% ice coverage threshold to define breakup, is the best predictor of when polar bears come ashore, why are PBI representatives using a 30% threshold? They don\u2019t say, or even mention that another method has ever been used to assess when polar bears come ashore. Nor do they mention that in general, since 2015 at least, some bears simply haven\u2019t been behaving as expected, and have been staying out on\u00a0highly degraded ice late into summer<\/a>. Odd, that.<\/p>\n\n\n\n

<\/p>\n\n\n\n

Problem Bears Onshore<\/strong><\/p>\n\n\n\n

The first real Churchill Polar Bear Alert Report came out (for week 2 of the summer season, 19-25 June), with only a few bears onshore close to town requiring encouragement to hang out further afield.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

<\/p>\n\n\n\n

References<\/strong><\/p>\n\n\n\n

Castro de la Guardia, L., Myers, P.G., Derocher, A.E., Lunn, N.J., Terwisscha van Scheltinga, A.D. 2017.<\/strong> Sea ice cycle in western Hudson Bay, Canada, from a polar bear perspective. Marine Ecology Progress Series<\/em> 564: 225\u2013233. http:\/\/www.int-res.com\/abstracts\/meps\/v564\/p225-233\/<\/a><\/p>\n\n\n\n

Cherry, S.G., Derocher, A.E., Thiemann, G.W., Lunn, N.J. 2013.<\/strong> Migration phenology and seasonal fidelity of an Arctic marine predator in relation to sea ice dynamics. Journal of Animal Ecology<\/em> 82<\/strong>:912-921. http:\/\/onlinelibrary.wiley.com\/doi\/10.1111\/1365-2656.12050\/abstract<\/a><\/p>\n\n\n\n

<\/p>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

According to\u00a0Polar Bears International, the \u201c3rd-earliest\u201d breakup date for Western Hudson Bay was caused by a \u201crecord breaking\u201d heat wave in May. Western Hudson Bay sea ice hit the 30% coverage threshold used by PBI to define \u201cbreakup\u201d on 17 June this year, prompting speculation about potential future impacts on polar bear survival should breakup come even earlier.<\/p>\n","protected":false},"author":121246920,"featured_media":265515,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_coblocks_attr":"","_coblocks_dimensions":"","_coblocks_responsive_height":"","_coblocks_accordion_ie_support":"","advanced_seo_description":"","jetpack_seo_html_title":"","jetpack_seo_noindex":false,"jetpack_seo_schema_type":"","_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_wpcom_ai_launchpad_first_post":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[1],"tags":[691820791,691818251,691820790,691820789],"class_list":["post-265498","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized","tag-bears-onshore","tag-polar-bears","tag-sea-ice-breakup","tag-western-hudson-bay","fallback-thumbnail"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/07\/0OIGP-3.jpeg?fit=1024%2C1024&ssl=1","jetpack_likes_enabled":true,"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/paxLW1-174e","jetpack-related-posts":[{"id":266535,"url":"https:\/\/climatescience.press\/?p=266535","url_meta":{"origin":265498,"position":0},"title":"Natural flexibility explains W Hudson Bay polar bear movements at breakup better than climate change","author":"uwe.roland.gross","date":"07\/10\/2023","format":false,"excerpt":"Hudson Bay in early July this year is a mosaic of more-than-average and less-than-average sea ice coverage but apparently, only the less-than-average ice areas constitute the \u201cearly breakup\u201d caused by climate change, and only \u201cdeniers\u201d would say otherwise.","rel":"","context":"In \"Climate change\"","block_context":{"text":"Climate change","link":"https:\/\/climatescience.press\/?tag=climate-change"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/07\/image-279.png?fit=1200%2C817&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/07\/image-279.png?fit=1200%2C817&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/07\/image-279.png?fit=1200%2C817&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/07\/image-279.png?fit=1200%2C817&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/07\/image-279.png?fit=1200%2C817&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":267566,"url":"https:\/\/climatescience.press\/?p=267566","url_meta":{"origin":265498,"position":1},"title":"Hudson Bay sea ice loss has not accelerated since 2014: in fact, summer ice cover has improved","author":"uwe.roland.gross","date":"07\/15\/2023","format":false,"excerpt":"This is only the third year since 2014 that the bay has had less than usual amounts of ice, which means most years since then have had normal or nearly normal ice coverage, similar to the 1980s. Hardly the\u00a0ever-worsening catastrophe\u00a0of sea ice loss story being spun in the media for\u2026","rel":"","context":"In \"Hudson Bay\"","block_context":{"text":"Hudson Bay","link":"https:\/\/climatescience.press\/?tag=hudson-bay"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/07\/0Polar-bears-10.webp?fit=1200%2C675&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/07\/0Polar-bears-10.webp?fit=1200%2C675&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/07\/0Polar-bears-10.webp?fit=1200%2C675&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/07\/0Polar-bears-10.webp?fit=1200%2C675&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/07\/0Polar-bears-10.webp?fit=1200%2C675&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":290645,"url":"https:\/\/climatescience.press\/?p=290645","url_meta":{"origin":265498,"position":2},"title":"Despite hand-wringing about Churchill polar bears this year, 2023 wasn\u2019t their worst summer","author":"uwe.roland.gross","date":"12\/10\/2023","format":false,"excerpt":"For months, the media has been bleating about the poor polar bears of Churchill suffering from lack of sea ice blamed on human-caused climate change during the so-called\u00a0\u2018hottest year\u2019 on record: in\u00a0April,\u00a0July,\u00a0August,\u00a0November, and\u00a0December.","rel":"","context":"In \"2023\"","block_context":{"text":"2023","link":"https:\/\/climatescience.press\/?tag=2023"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/12\/image-201.png?fit=1200%2C800&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/12\/image-201.png?fit=1200%2C800&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/12\/image-201.png?fit=1200%2C800&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/12\/image-201.png?fit=1200%2C800&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/12\/image-201.png?fit=1200%2C800&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":239391,"url":"https:\/\/climatescience.press\/?p=239391","url_meta":{"origin":265498,"position":3},"title":"Recent paper on W. Hudson Bay polar bears includes new official sea ice freeze-up data","author":"uwe.roland.gross","date":"01\/13\/2023","format":false,"excerpt":"Even though it\u2019s in graph form only, we finally have an update on sea ice freeze-up dates for Western Hudson Bay for 2016-2020 (but not breakup dates).","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/01\/image-568.png?fit=1009%2C1200&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/01\/image-568.png?fit=1009%2C1200&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/01\/image-568.png?fit=1009%2C1200&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/01\/image-568.png?fit=1009%2C1200&ssl=1&resize=700%2C400 2x"},"classes":[]},{"id":257313,"url":"https:\/\/climatescience.press\/?p=257313","url_meta":{"origin":265498,"position":4},"title":"Polar bears in W. Hudson Bay are in good shape, says researcher. So are numbers really falling?","author":"uwe.roland.gross","date":"05\/13\/2023","format":false,"excerpt":"We\u2019ve got ourselves another round of field data\u2013i.e., facts\u2013not fitting the\u00a0polar-bears-are-starving-to-death\u00a0narrative. According to polar bear specialist Andrew Derocher, Western Hudson Bay polar bears his team saw in April while installing collars and ear tags were in\u00a0good shape\u00a0this year, as he said they were\u00a0last year.","rel":"","context":"In \"plar bears\"","block_context":{"text":"plar bears","link":"https:\/\/climatescience.press\/?tag=plar-bears"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/05\/00Polar-bears-10.webp?fit=1200%2C675&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/05\/00Polar-bears-10.webp?fit=1200%2C675&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/05\/00Polar-bears-10.webp?fit=1200%2C675&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/05\/00Polar-bears-10.webp?fit=1200%2C675&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/05\/00Polar-bears-10.webp?fit=1200%2C675&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":336354,"url":"https:\/\/climatescience.press\/?p=336354","url_meta":{"origin":265498,"position":5},"title":"Last month of Arctic spring fails to bring sea ice to its knees, even in Southern Hudson Bay","author":"uwe.roland.gross","date":"07\/13\/2024","format":false,"excerpt":"Polar bear habitat for June \u2014 the last month of spring in the Arctic \u2014 is still within 2 standard deviations of the long-term average despite sea ice experts\u2019 predictions that catastrophic declines can be expected any year now.","rel":"","context":"In \"Arctic\"","block_context":{"text":"Arctic","link":"https:\/\/climatescience.press\/?tag=arctic"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/07\/0-plar-bears-47.jpeg?fit=1200%2C762&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/07\/0-plar-bears-47.jpeg?fit=1200%2C762&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/07\/0-plar-bears-47.jpeg?fit=1200%2C762&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/07\/0-plar-bears-47.jpeg?fit=1200%2C762&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/07\/0-plar-bears-47.jpeg?fit=1200%2C762&ssl=1&resize=1050%2C600 3x"},"classes":[]}],"_links":{"self":[{"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/posts\/265498","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/users\/121246920"}],"replies":[{"embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=265498"}],"version-history":[{"count":11,"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/posts\/265498\/revisions"}],"predecessor-version":[{"id":265517,"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/posts\/265498\/revisions\/265517"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/media\/265515"}],"wp:attachment":[{"href":"https:\/\/climatescience.press\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=265498"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=265498"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=265498"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}