Will the low sea ice threaten harp seals and polar bears on Canada’s east coast this yr? – Watts up with that?

By On Mar 13, 2021

Reposted by Polar Bear Science

Posted on March 11, 2021 |

In early February of this year, sea ice was much lower than usual on the Labrador coast and virtually non-existent in the Gulf of St. Lawrence, two important whelping habitats for North Atlantic harp seals. The picture would have been very bleak for seal pups and the polar bears of Davis Strait, whose food depends on them, had the ice not expanded and thickened by early March – but it did. Past experience suggests that harp seals, which normally wither in the Gulf of St. Lawrence, where the ice is still well below average this year, go on ice before Southern Labrador (“the front line”) to to get their pups.

SEA ICE FROM LABRADOR / GULF OF ST. LAW

There’s no way to sugar-coat this: there wasn’t much ice off the east coast in early February that turned out to be as bad or worse than last year, 2011, with low ice levels. Below is the weekly departure from the Canadian Ice Service normal ice map for the week of February 1, which shows much of the area normally ice-covered (red) at that time of year that was still open water:

However, there was ice further north that has now moved from Davis Strait along the Labrador coast (see below):

On March 10th there is still much less ice than usual, but on the frontline (southern Labrador coast) it seems sufficient that seals have their pups.

However, the puppy grounds won’t spread across the north coast of Newfoundland as usual – there’s just no ice for it:

WHEN DO HARP SEALS NEED ICE?

The timing of the puppy season for seals in the North Atlantic is White Sea (late February); Gulf of St. Lawrence, also known as “Golf” (early March, mean March 5); Labrador / Newfoundland, also known as “Front” (mid to late March, mean March 12); East Greenland around Jan Mayen Island, also known as “West Ice” (late March to early April). The Jan Mayen / West Ice region is the northernmost place where Harp seals puppies, breeds and moults.

The sea ice in the Gulf in the week of March 8, 2021 is not thick enough for harp seals. You need ice in the first year (green on the map), which is sorely missing in golf this year:

No difference was found between harp seals in the Gulf and those at the front, so they are treated together as one population for management purposes (Sergeant (1991; Stenson 2014). Harp seals are currently more common than they have been for decades and the graph shows the changes in harp seal numbers in the northeast of the Atlantic between 1952 and 2019 (DFO 2020):

What kind of ice do harp seals need?

According to Sergeant (1991: 116):

“… It is possible to categorize the type of ice used by seals to pup (Fig. 127). This is mid winter ice in late February with an ice cover of 6 to 8/10, meaning it must be strong enough but have enough open lines for the seals to penetrate. “ [my bold]

Sergeant (1976: 98, 38) pointed out that ice in the Gulf forms in situ and is usually only about 40-50 cm thick, while the ice at the front in the first year is thick ice originating in the far north. This makes ice formation in the Gulf of St. Lawrence much more susceptible to local conditions (warm or cold) and therefore the highly variable sea ice conditions are not new (Johnston et al. 2005), as confirmed by reports from sealers in the early 20th century from 1924-1941 (Ryan 2014).

Sergeant (1991: 31) made this point:

“The greatest year-to-year changes are seen in the Gulf of St. Lawrence on the southern edge of the range, where the ice can be thick or almost non-existent at one time of the year.” [my bold]

WHAT DO SEALS DO WHEN THERE IS A LITTLE ICE?

What do seals do when ice conditions in the Gulf of St. Lawrence are poor, as has often happened in the past? Sergeant (1991: 56) said this:

“In 1981, when there was almost no ice in the Gulf, at least several hundred young and ten adult deaths were observed on the beaches on the north coast of Prince Edward Island….

Sergeant (1982) found that ice conditions significantly affected casting patterns in the Gulf of St. Lawrence in 1953, 1969 and 1981, or about a year in ten. At least in 1969, ice conditions on the front line and in the Strait of Belle Isle were also low, and would have allowed adult women who had not been thrown in the Gulf to look north for ice. Some may have.

…

[in 1969] There was no ice in the Gulf except in Northumberland Strait and the shore ice on Prince Edward I’s north coast. It was generally agreed that no more than 40,000 animals wept here. 100,000.

Probably the rest of them looked for ice and found none in the northern Gulf, passed the Strait of Belle Isle and whirled along with the front herd on the Labrador coast at Hamilton Inlet.

In 1981, although the ice in the Gulf was minimal in size and thickness, harp seals swirled off the west coast of the Magdalen Is. And drifted to the north coast of Prince Edward I. Here, storms destroyed the small amount of ice and young seals died from starvation and Loss of body reserves (Dr. JR Geraci, in suffered.).

…

In unusually strong ice conditions, harp seals will not be able to move from the front to the gulf in front of the pup because the Belle Isle Strait will be blocked by ice. The pup is found only further south along the east coast of Newfoundland. “ [my bold]

However, polar bears have seldom invaded the Gulf during the last difficult ice years: They eat seal pups on the ice on the frontline off Newfoundland and Labrador.

HOW DID THE LAST IRON LOOK LIKE?

The worst year for low ice on the east coast in recent decades was 2011 (Stenson et al. 2015), see below, for the week of January 31:

Comparing the above with this year for the week of February 1st (below) shows the remarkable similarity:

REFERENCES

Department of Fisheries and Oceans Canada (DFO) 2012. Current status of the Northwest Atlantic Seals (Pagophilus groenlandicus). Scientific advisory report 2011/070.

Department of Fisheries and Oceans Canada DFO. 2014. Status of Northwest Atlantic Seals, Pagophilus groenlandicus. DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2014/011.

DFO. 2020. 2019 Status of the Northwest Atlantic Seals, Pagophilus groenlandicus. DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2020/020. http://www.isdm-gdsi.gc.ca/csas-sccs/applications/Publications/result-eng.asp?params=0&series=7&year=2020 PDF here.

Johnston, DW, Friedlaender, AS, Torres, LG, Lavigne, DM 2005. Variation in sea ice cover on the east coast of Canada from 1969 to 2002: Climate variability and effects on harp and hooded seals. Climate Research 29: 209- 222.

Kovacs, KM 2015. Pagophilus groenlandicus. The IUCN 2015 Red List of Threatened Species: e.T41671A45231087. http://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T41671A45231087.de

Ryan, S. 2014. Appendix 3: Chafes “Notes of Journeys” 1924-1941, In: The Last of the Ice Hunters: An Oral History of the Newfoundland Seal Hunting, pg. 445-457. Flanker Press, St. John’s. [Contains critical notes about ice conditions between 1924 and 1941 and where harp seals were found in those years]

Sergeant, DE 1976. History and current status of the populations of harp and hooded seals. Biological conservation 10:95-118.

Sergeant, DE 1991. Harp seals, humans and ice. Canadian Special Fisheries and Aquatic Sciences 114. Fisheries and Oceans Canada, Ottawa.

Stenson, UK 2014. The status of harp and hooded seals in the North Atlantic. Report presented at the Scientific Council meeting in June 2014. Northwest Atlantic Fisheries Organization SCR Doc. 14/026, serial number N6321.

Stenson, GB, Buren, AD and Koen-Alonso, M. 2015. The effects of climate change and abundance on the reproduction of an ice-dependent species, the northwest Atlantic seal Pagophilus groenlandicus. ICES Journal of Marine Science 73 (2): 250-262. http://icesjms.oxfordjournals.org/content/73/2/250

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