What was done
The authors of this eye-opening article in the official oracle of the Royal Swedish Academy of Sciences examined changes in the fraction of open-water found within various pack-ice microhabitats of Foxe Basin, Hudson Bay, Hudson Strait, Baffin Bay-Davis Strait, northern Baffin Bay and Lancaster Sound over a 23-year interval (1979-2001) using remotely-sensed microwave measurements of sea-ice extent, after which the trends they documented were "related to the relative importance of each wintering microhabitat for eight marine indicator species and potential impacts on winter success and survival were examined."

What was learned
Heide-Jorgensen and Laidre report that Foxe Basin, Hudson Bay and Hudson Strait showed small increasing trends in the fraction of open-water, with the upward trends at all microhabitats studied ranging from 0.2 to 0.7% per decade.  In Baffin Bay-Davis Straight and northern Baffin Bay, on the other hand, the open-water trend was downward, and at a mean rate for all open-water microhabitats studied of fully 1% per decade, while the trend in all Lancaster Sound open-water microhabitats was also downward, in this case at a mean rate of 0.6% per decade.

With respect to the context of these open-water declines, Heide-Jorgensen and Laidre report that "increasing trends in sea ice coverage in Baffin Bay and Davis Strait (resulting in declining open-water) were as high as 7.5% per decade between 1979-1999 (Parkinson et al., 1999; Deser et al., 2000; Parkinson, 2000a,b; Parkinson and Cavalieri, 2002) and comparable significant increases have been detected back to 1953 (Stern and Heide-Jorgensen, 2003)."  They additionally note that "similar trends in sea ice have also been detected locally along the West Greenland coast, with slightly lower increases of 2.8% per decade (Stern and Heide-Jorgensen, 2003)."

The two scientists note that "two types of vulnerability have been identified relative to increasing sea ice: i) the direct physical impact of sea ice as a barrier for air-breathing foraging animals; and ii) the cascading effects of changes in marine productivity."

The first of these problems most affects the cetaceans, including over 50,000 narwhal, 20,000 beluga and many bowhead whales.  In this regard, they note "there is sufficient evidence to detect a clear decline in the amount of open-water in several narwhal wintering microhabitats, including the Northern Wintering Ground, Southern Wintering Ground, Disko Bay, Store Hellefiske Bank, North Water and Cumberland Sound and adjacent offshore areas," several of which locations also serve as wintering grounds for beluga and bowhead whales.  In addition, they note that 33,000,000 breeding pairs of little auks feed in the offshore open-water of the North Water region in early May, and that ice-free areas there are declining and less water is available for the little auks at that time.  Similar problems confront many of the more than 100,000 breeding pairs of king eiders and large numbers of thick-billed murres that come from lands as far away as Svalbard and eastern Russia.

All in all, a crisis of huge proportions appears to be building, as the sea ice of these regions continues to increase.  What may be even more important than the long-term growth of this factor, however, is the increasing sea ice coverage in combination with environmental variability, "which leads to an increased frequency of periodic complete freeze-over."  According to the two scientists from the Greenland Institute of Natural Resources, who are experts in this field, this phenomenon "can result in catastrophic mortalities that can affect population trajectories."  In the case of Disko Bay, for example, they report that "less than 5% open-water was observed on 89% of the days in March between 1992-1995, and during this period, 15% of these days had complete freeze-over."  Already, in fact, there have been reports of common eiders, little auks and thick-billled murres succumbing in ice entrapments (Gilchrist and Robertson, 2000),while hundreds of narwhals have periodically died during episodes of rapid sea ice formation caused by sudden cold periods (Siegastad and Heide-Jorgensen, 1994; Heide-Jorgensen et al., 2002).

What it means
There's the devil to pay when Hellefiske freezes over ... and it's been happening there and elsewhere in the Arctic ever more frequently over the past few decades.

References
Deser, C.J., Walsh, E. and Timlin, M.S.  2000.  Arctic sea ice variability in the context of recent atmospheric circulation trends.  Journal of Climate 13: 617-633.

Gilchrist, H.G. and Robertson, G.J.  2000.  Observations of marine birds and mammals wintering at polynyas and ice edges in the Belcher Islands, Nunavut, Canada.  Arctic 53: 61-68.

Heide-Jorgensen, M.P., Richard, P., Ramsay, M. and Akeeagok, S.  2002.  In: Three recent Ice Entrapments of Arctic Cetaceans in West Greenland and the Eastern Canadian High Arctic.  Volume 4, NAMMCO Scientific Publications, pp. 143-148.

Parkinson, C.L.  2000a.  Variability of Arctic sea ice: the view from space, and 18-year record.  Arctic 53: 341-358.

Parkinson, C.L.  2000b.  Recent trend reversals in Arctic sea ice extents: possible connections to the North Atlantic Oscillation.  Polar Geography 24: 1-12.

Parkinson, C.L. and Cavalieri, D.J.  2002.  A 21-year record of Arctic sea-ice extents and their regional, seasonal and monthly variability and trends.  Annals of Glaciology 34: 441-446.

Parkinson, C.L., Cavalieri, D.J., Gloersen, P., Jay Zwally, H. and Comiso, J.C.  1999.  Arctic sea ice extents, areas, and trends, 1978-1996.  Journal of Geophysical Research 104: 20,837-20,856.

Siegstad, H. and Heide-Jorgensen, M.P.  1994.  Ice entrapments of narwhals (Monodon monoceros) and white whales (Delphinapterus leucas) in Greenland.  Meddeleser om Gronland Bioscience 39: 151-160.

Stern, H.L. and Heide-Jorgensen, M.P.  2003.  Trends and variability of sea ice in Baffin Bay and Davis Strait.  Polar Research 22: 11-18.