5. Extrapolating polar bear populations

In light of these considerations we do not consider it a sound methodology to assume that local air temperature trends adequately explain WH population conditions and that extrapolating WH results generates predictions for polar bears and their habitat over the circumpolar Arctic (e.g., Stirling and Derocher, 1993; World Wide Fund for Nature 2002; Derocheret al., 2004). We take particular exception to the suggestion by Derocher et al. (2004, p. 163) that polar bears will not likely survive ‘‘as a species’’[5] if several computer-generated scenarios of air temperature-driven disappearance of sea-ice ‘‘by the middle of the present century’’ come true. The conjecture seems errant for two reasons. First, most climate models predict a complete disappearance of sea-ice over the central Arctic for only the late summer (i.e., September) while the whole Hudson Bay is always ice-free during this time regardless of the forcing by anthropogenic greenhouse gases(see for example Figs. 8 and 9 in Johannessen et al., 2004).Second, in the cited climate model projections, sea-ice at the Hudson Bay for the late winter or early spring (i.e., March) was never predicted to completely disappear by the end of this century, even under scenarios that posit greenhouse gas accumulations at rates considerably faster than currently or historically observed. In a recent multi-model study of climate projection in the Hudson Bay region, Gagnon and Gough(2005b, p. 291) concluded that ‘‘Hudson Bay is expected to remain completely ice covered in those five models by the end of this century for at least part of the year.’’

It should also be noted that Gough et al. (2004) had earlier reported that the observed thickening of sea-ice cover during the last few decades on the western coast of Hudson Bay was in direct contradiction to the thinning ice scenario that is

posited by warming due to an enhanced CO2 atmosphere. Under these CO2-warming scenarios, the models predicted not only an earlier spring break-up of sea-ice but also later fall freeze-up at Hudson Bay (Gagnon and Gough, 2005b). Available observations from 1971 to 2003, by contrast, do not show any tendency for a later freeze-up of ice especially at WH or southwestern Hudson Bay (Stirling et al., 1999; Gagnon and Gough, 2005a). Further to the north, Melling (2002, pp. 2–18), in his study of sea-ice around the northern Canadian Arctic archipelago, concluded that ‘‘[i]nterannual fluctuations in

late-summer ice coverage obscure any evidence of trend [in the Sverdrup Basin]. A decadal cycle contributes variability to the times series of both total and multiyear ice concentrations. Because the reputedly extreme conditions of 1998 are similar to occurrences in 1962 and 1971, there is little basis on which to view them as evidence for anthropogenic change.’ We therefore conclude that it is highly premature to argue for the extinction of polar bear across the circumpolar Arctic with in this century as incorrectly suggested in Derocher et al. (2004).

Finally, we wish to encourage a renewed archaeological search for information related to polar bear population ecology from 1760 to 1820, when historical evidence (based on early thermometers at trading posts of Churchill Factory and York Factory) suggests that the climatic regimes at WH had shifted from temperate to arctic conditions (see Ball,1995; Catchpole, 1995). Ball (1983, 1986) documented large changes and abrupt shifts in both floral (i.e., tree  line boundary between the boreal forest and the tundra) and fauna (i.e., migration of wild geese) ecosystem responses of the Hudson Bay region that occurred naturally as a consequence of the varying mean locations of the Arctic Front (Bryson, 1966). Ball (1995) suggested that the three consecutive decades from 1770 to 1800 at York Factory consisted of very wet and variable winter conditions oscillating between extremes of heavy snow versus almost snow-free conditions, which made the thriving of wildlife populations difficult. Heavy late winter rains, for example, have been proposed as a cause of the collapse of maternity dens, suffocating the occupants (Stirling and Derocher, 1993). Excessive snowfall was noted to alter oxygen flux through the snow layer of maternity dens and could negatively impacting survival rates of young altricial cubs that need to be nursed for 3 months before they are able to leave the den with their mothers (Derocher et al., 2004). The records compiled by Ball and Kingsley (1984) suggested an interval with a relatively warm late spring (April–May–June)at York Factory of about 2.9 8C for 1779, 1780, and 1782 (no data for 1781) when monthly air temperature readings were available from the Hudson Bay’s Company and Royal Society’s archives. These data may be applied to assess the resiliency of polar bears under adverse climate conditions. The latest research by Scott and Stirling (2002) have successfully dated, through sophisticated timing and fingerprinting techniques of dendro-sciences, polar bear maternity dens and dens activities inland from the coast of WH, south of Churchill and north of York Factory, since at least 1795,while reports of polar bears have been recorded at least since1619. These authors concluded that ‘‘there does not appear to be a relationship between climate trends and the rates of den disturbance during the overall 1850–1993 period’’ and that ‘‘changes in the frequency and pattern of disturbances at den sites may be related to the pattern of hunting and trading of hides at York Factory during the 19th and early20th century’’ (p. 163). Thus, the reality of human activity impacting population ecology of polar bears at WH is clear while empirical evidence for polar bear resiliency under extended records of weather extremes and a wide range of climatic conditions may be stronger than previously thought.

6. Conclusions

The interactions among sea-ice, atmospheric and oceanic circulations, and air and sea temperatures are complex and our understanding of these issues in the Arctic context is

limited. We suggest that large interannual variability, which we view as stochastic in nature (e.g., Wunsch, 1999), dominates the climatic changes in WH. Improved understanding of polar bear resiliency and adaptive strategy to climatic changes must consider human–bear interactions, natural population dynamics, and the dominant components of variability of the Arctic ice, ocean and atmosphere that operate naturally on decadal to multidecadal timescales (Vinje, 2001; Polyakov et al., 2003a,b; Soon, 2005). The clear evidence for strong regional differences in the spatial pattern of historical climate change around the Hudson Bay region add a layer of uncertainty to the task of explaining empirical evidence. It is certainly premature, if not impossible, to tie recent regional climatic variability in this part of central Canada to anthropogenic greenhouse gases and, further, to extrapolate species-level conditions on this basis. These complex interactions of man-made and natural factors will ultimately bring about particular ecosystem responses (perhaps yet unintelligible to us) but we find that late spring air temperature has not emerged as a decisive causal factor or reliable predictor. Such a complexity within the Hudson Bay’s ecosystem clearly challenges the usefulness of the original proposal in considering polar bears as indicators of climatic warming made by Stirling undercover (1993).

The broad claim for the sea-ice to be ‘‘gone by the middle of the present century’’ could be both misleading and confusing in that existing model predictions are for the complete disappearance of late summer, rather than spring, sea-ice over the central Arctic ocean. Climate models actually expected Hudson Bay to be fully covered with sea-ice at least part of the year (including early spring) even under rather extreme forcing assumptions by involving rapid increases in anthropogenic greenhouse gases by the end of this century. This is why extrapolation studies arguing for severe negative impacts of polar bears under a global warming scenario are neither scientifically convincing nor appropriate.

The fate of the charismatic polar bear population is of considerable public concern, and rightly so. Science can best contribute to the goals of conservation by providing the most accurate possible understanding of the factors affecting the population ecology of these impressive animals. Our concern in this paper is that if attention is inappropriately confined to a single mechanism, namely greenhouse warming, opportunities to understand other relevant mechanisms behind changes in bear population and health parameters may be lost in the process. It is also abundantly clear that relying on such a strict single-variable-driven scenarios of global warming by increasing atmospheric carbon dioxide and related melting sea-ice in discussing an issue as complex as the population and well being of polar bears runs counter to the underlying realities and challenges of ecological complexity that emphasizes at least the six co-dimensions of spatial, temporal, structural, process, behavioral and geometric complexities (as e.g., outlined in viewpoints of Li,2004; Loehle,2004; Cadenasso et al., 2006).

Therefore, we believe it is premature to make the ‘‘one dimensional’’predictions about how climate change may affect polar bears in general and there is no ground for raising public alarm about any imminent extinction of Arctic polar bears. The multiple known and likely stresses interact dynamically and may contribute in an additive fashion to negative effects on polar bears. To quantify the severity of these stress co-factors, however, is very difficult, if not almost impossible, with current limitations on data. Areas of research we would particularly encourage include archaeological investigations, improved data on prey population dynamics, and examination of lower trophic levels to provide more insight into the proximate effects of climate change on Arctic species. We further suggest that the A circulation index may be useful in tracking the propagation of climatic and meteorological signals through the coupled ecosystems of the Arctic land and sea that promises only the undeniable complexity of multi-trophic level interactions(Fortier et al., 1996; Steinke et al., 2002; Hansen et al.,2003).

Acknowledgements

We thank our colleagues (especially those sharing our concerns for the well beings of polar bears) for important conversations and lessons throughout the years about this topic. We further thank R. McKitrick for performing the Granger causality tests on statistical associations shown in Fig. 2 of this paper and other substantial contributions. We are grateful for the constructive comments on earlier versions of the manuscript from S. Polischuk, S.-L. Han, and A. Derocher, which were critical for the improvement of the final version. (The open review on a 2002–2003 version of our manuscript by A. Derocher is available at http://cfa-www.harvard.edu/_wsoon/polarbearclimate05-d/.) All views and conclusions are strictly our own and do not reflect upon any of those acknowledged (especially A. Derocher) or any institutions with whom we are affiliated. Dyck and W. Soon initiated this scientific study around2002–2003 without seeking research funding and both have contributed equally. W. Soon’s effort for the completion of this paper was partially supported by grants from the Charles G. Koch Charitable Foundation, American Petroleum Institute, and Exxon-Mobil Corporation. The views expressed herein are solely of the authors and are independent of sources providing support.

References

Aanes, R., Sæther, B.-E., Smith, F.M., Cooper, E.J., Wookey, P.A.,

Øritsland, N.A., 2002. The Arctic oscillation predicts effects of climate change in two trophic levels in a high-arctic ecosystem. Ecol. Lett. 5, 445–453.

Amstrup, S.C., Wiig, Ø. (Eds.), 1991. Polar Bears: Proceedings of the 10th Working Meeting of the IUCN/SSC Polar Bear Specialist Group, IUCN, Gland, Switzerland, p. 107.

Arnould, J.Y.P., 1990. The energetics of lactation in polar bears (Ursus maritimus Phipps). M.Sc. Thesis. University of Saskatchewan, Saskatoon, 80 pp.

Baldwin, M.P., 2001. Annular modes in global daily surface pressure. Geophys. Res. Lett. 28, 4115–4118.

Ball, T.F., 1983. The migration of geese as an indicator of climate change in the southern Hudson Bay region between 1715and 1851. Clim. Change 5, 85–93.

Ball, T.F., 1986. Historical evidence and climatic implications of a shift in the boreal forest-tundra transition in central Canada. Clim. Change 8, 121–134.

Ball, T.F., 1995. Historical and instrumental evidence of climate: western Hudson Bay, Canada, 1714–1850. In:

Bradley, R.S., Jones, P.D. (Eds.), Climate Since A.D. 1500.Routledge, pp. 40–73.

Ball, T.F., Kingsley, R.A., 1984. Instrumental temperature records at two sites in central Canada: 1768 to 1910. Clim. Change 6, 39–56.

Bryson, R.A., 1966. Air masses, streamlines and the boreal forest. Geogr. Bull. 8, 228–269.

Cadenasso, M.L., Pickett, S.T.A., Grove, J.M., 2006. Dimensions of ecosystem complexity: heterogeneity, connectivity, and history. Ecol. Complex. 3, 1–12.

Calvert, W., Stirling, I., Taylor, M., Lee, L.J., Kolenosky, G.B., Kearney, S., Creˆ te, M., Smith, B., Luttich, S., 1991a. Research on polar bears in Canada 1985–87. In: Amstrup, S.C., Wiig,Ø. (Eds.), Polar Bears: Proceedings of the 10th Working Meeting of the IUCN/SSC Polar Bear Specialist Group, IUCN, Gland, Switzerland, pp. 11–24.Calvert, W., Stirling, I., Taylor, M., Lee, J.L., Kolenosky, G.B.Kearney, S., Crete, M., Smith, B., Luttich, S., 1991b. Polar bear management in Canada 1985–87. In: Amstrup, S.C.,Wiig, Ø. (Eds.), Polar Bears: Proceedings of the 10th Working Meeting of the IUCN/SSC Polar Bear Specialist Group, IUCN, Gland, Switzerland, pp. 1–10.

Calvert, W., Stirling, I., Taylor, M., Ramsay, M.A., Kolenosky,G.B., Creˆ te, M., Kearney, S., Luttich, S., 1995a. Research on polar bears in Canada 1988–92. In: Wiig, Ø.,Born, E.W.,

Garner, G.W. (Eds.), Polar Bears: Proceedings of the 11thWorking Meeting of the IUCN/SSC Polar Bear Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK, pp.33–59.

Calvert, W., Taylor, M., Stirling, I., Kolenosky, G.B., Kearney, S., Crete, M., Luttich, S., 1995b. Polar bear management in Canada 1988–92. In: Wiig, Ø., Born, E.W., Garner,G.W.(Eds.), Polar Bears: Proceedings of the 11th Working Meeting of the IUCN/SSC Polar Bear Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK,pp. 61–76.

Calvert, W., Taylor, M., Stirling, I., Atkinson, S., Ramsay, M.A.,Lunn, N.J., Obbard, M., Elliott, C., Lamontagne, G., Schaefer, J., 1998. Research on polar bears in Canada 19931996. In: Derocher, A.E., Garner, G.W., Wiig, Ø. (Eds.), Polar Bears: Proceedings of the 12th Working Meeting of the IUCN/SSC Polar Bear Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK, pp. 69–91.

Catchpole, A.J.W., 1995. Hudson’s Bay Company ships’ logbooks as sources of sea ice data, 1751–1870. In: Bradley,R.S., Jones, P.D. (Eds.), Climate Since A.D. 1500. Routledge,pp. 17–39.

Cohen, J., Barlow, M., 2005. The NAO, the AO and global warming: how closely related? J. Clim. 18, 4498–4513.

Derocher, A.E., Andriashek, D., Stirling, I., 1993. Terrestrial foraging by polar bears during the ice-free period in western Hudson Bay. Arctic 46, 251–254.

Derocher, A.E., Garner, G.W., Lunn, N.J., Wiig, Ø. (Eds.), 1998.Polar Bears: Proceedings of the 12th Working Meeting of the IUCN/SSC Polar Bear Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK 159 pp.

Derocher, A.E., Lunn, N.J., Stirling, I., 2004. Polar bears in a warming climate. Integr.Comp. Biol. 44,163–176.

Derocher, A.E., Stirling, I., 1990a. Distribution of polar bears(Ursus maritimus) during the ice-free period in western Hudson Bay. Can. J. Zool. 68, 1395–1403.

Derocher, A.E., Stirling, I., 1990b. Aggregating behaviour of adult male polar bears(Ursus maritimus). Can. J. Zool. 68, 1390–1394.

Derocher, A.E., Stirling, I., 1992. The population dynamics of polar bears in western Hudson Bay. In: McCullough, D.R.,Barrett, R.H. (Eds.), Wildlife 2001: Populations. Elsevier Science Publishers, pp. 1150–1159.

Derocher, A.E., Stirling, I., 1995. Estimation of polar bear population size and survival in western Hudson Bay. J. Wildlife Manage. 59, 215–221.

Derocher, A.E., Stirling, I., 1996. Aspects of survival in juvenile polar bears. Can. J. Zool. 74, 1246–1252.

Derocher, A.E., Stirling, I., 1998a. Offspring size and maternal investment in polar bears (Ursus maritimus). J. Zool. (Lond.)245, 253–260.

Derocher, A.E., Stirling, I., 1998b. Geographic variation in growth of polar bears (Ursus maritimus). J. Zool. (Lond.) 245, 65–72.

Dyck, M.G., 2001. Effects of tundra vehicle activity on polar bears(Ursus maritimus) at Churchill, Manitoba. MNRM Thesis. University of Manitoba, Winnipeg.

Dyck, M.G., Baydack, R.K., 2004. Vigilance behaviour of polar bears (Ursus maritimus) in the context of wildlife-viewing activities at Churchill, Manitoba, Canada. Biol.Conserv. 116,343–350.

Dyck, M.G., Baydack, R.K., 2006. Aspects of human activities associated with polar bear viewing at Churchill, Manitoba, Canada. Hum. Dimensions Wildlife 11, 143–145.

Eberhardt, L.L., Siniff, D.B., 1977. Population dynamics and marine mammal policies. J. Fish. Res. Bd. Can. 34, 183–190.

Fortier, L., Gilbert, M., Ponton, D., Ingram, R.G., Robineau, B.,Legendre, L., 1996.Impact of freshwater on a sub arctic coastal ecosystem under seasonal sea ice(southeastern Hudson Bay, Canada). III. Feeding success of marine fish larvae. J. Mar.Syst. 7, 251–265.

Fowler, C.W., 1990. Density dependence in northern fur seals(Callorhinus ursinus). Mar.Mamm. Sci. 6, 171–196.

Gagnon, A.S., Gough, W.A., 2005a. Trends in the dates of freeze up and breakup over Hudson Bay, Canada. Arctic 58, 370–382.

Gagnon, A.S., Gough, W.A., 2005b. Climate change scenarios for the Hudson Bay region: an intermodel comparison. Clim.Change 69, 269–297.

Gong, D.-Y., Ho, C.-H., 2003. Arctic oscillation signals in the East Asian summer monsoon. J. Geophys. Res. 108 (D2), 4066,doi:10.1029/2002JD002193: 1–7.

Gough, W.A., Gagnon, A.S., Lau, H.P., 2004. Interannual variability of Hudson Bay ice thickness. Polar Geogr. 28, 222–238.

Hamilton, J.D., 1994. Time Series Analysis. Princeton University Press, Princeton, 820pp.

Hansen, A.S., Nielsen, T.G., Levinsen, H., Madsen, S.D.,Thingstad, T.F., Hansen, B.W., 2003. Impact of changing ice cover on pelagic productivity and food web structure in Disko Bay, West Greenland: a dynamic model approach. Deep Sea Res. I 50, 171–187.

Herrero, J., Herrero, S., 1997. Visitor safety in polar bear viewing activities in the Churchill region of Manitoba, Canada. Report for Manitoba Natural Resources and Parks Canada, Calgary.

Houser, C., Gough, W.A., 2003. Variations in sea ice in the Hudson Strait: 1971–1999. Polar Geogr. 27, 1–14.

IUCN (International Union for the Conservation of Nature and Natural Resources)/Polar Bear Specialist Group, 2005.

Resolution #3-2005: status of the Western Hudson Bay (WH)population analysis. Available at http://pbsg.npolar.no/Meetings/Resolutions/14-resolutions.htm.

Johannessen, O.M., Bengtsson, L., Miles, M.W., Kuzmina, S.L.,Semenov, V.A., Alekseev, G.V., Nagurnyi, A.P., Zakhorov, V.F., Bobylev, L.P., Pettersson, L.H., Hasselman, K., Cattle, P.,2004. Arctic climate change: observed and modelled temperature and sea-ice variability. Tellus 56A, 328–341(plus Corrigendum in Tellus 56A, 559–560).

Kearney, S.R., 1989. The Polar Bear Alert Program at Churchill,Manitoba. In: Bromely, M. (Ed.), Bear–People Conflict: Proceedings of a Symposium on Management Strategies, Yellowknife, Northwest Territories Department of Renewable Resources, pp. 83–92.

Kie, J.G., Drawe, D.L., Scott, G., 1980. Changes in diet and nutrition with increased herd size in Texas white-tailed deer. J. Range Manage. 33, 28–34.

Kie, J.G., Bowyer, R.T., Stewart, K.M., 2003. Ungulates in western forests: habitat relationships, population dynamics, and ecosystem processes. In: Zabel, C., Anthony, R. (Eds.),Mammal Community Dynamics in Western Coniferous Forests: Management and Conservation. The John Hopkins University Press, Baltimore, pp. 296–340.

Kimura, N., Wakatsuchi, M., 2001. Mechanisms for the variation of sea ice extent in the Northern Hemisphere. J. Geophys.Res. 106, 31319–31331.

Kolenosky, G.B., Abraham, K.F., Greenwood, C.J., 1992. Polar bears of southern Hudson Bay. Polar Bear Project, 1984–88.

Final Report. 107 pp. Available from: Wildlife Research and Development Section, Ontario Ministry of Natural Resources, 300 Water St., 3rd Floor N, Peterborough, OntarioK9J 8M5, Canada.

Kryjov, V.N., 2002. The influence of the winter Arctic Oscillation

on the Northern Russian spring temperature. Int. J. Clim. 22,

779–785.

Kurte´ n, B., 1964. The evolution of the polar bear, Ursus maritimus Phipps. Acta Zool. Fenn. 108, 1–30.

Lee, J., Taylor, M., 1994. Aspects of the polar bear harvest in the Northwest Territories, Canada. Int. Conf. Bear Res. Manage.9, 237–243.

Lehner, P.N., 1979. Handbook of Ethological Methods. Garlan STPM Press, New York, NY, 403 pp.

Li, B.-L., 2004. Editorial. Ecol. Complex. 1, 1–2.

Loehle, C., 2004. Challenges of ecological complexity. Ecol.Complex. 1, 3–6.

Lunn, N.J., Stirling, I., Andriashek, D., Kolenosky, G.B., 1997a. Reestimating the size of the polar bear population in western Hudson Bay. Arctic 50, 234–240.

Lunn, N.J., Stirling, I., Nowicki, S.N., 1997b. Distribution and abundance of ringed (Phoca hispida) and bearded seals(Erignathus barbatus) in western Hudson Bay. Can. J.Fish.Aquat. Sci. 54, 914–921.

Lunn, N.J., Taylor, M., Calvert, W., Stirling, I., Obbard, M., Elliott,C., Lamontagne, G., Schaeffer, J., Atkinson, S., Clark, D., Bowden, E., Doidge, B., 1998. Polar bear management in

Canada 1993–1996. In: Derocher, A.E., Garner, G.W., Wiig, Ø.(Eds.), Polar Bears: Proceedings of the 12th Working Meeting of the IUCN/SSC Polar Bear Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK, pp. 51–66.

Lunn, N.J., Schliebe, S., Born, E.W. (Eds.), 2002. Polar Bears: Proceedings of the 13th Working Group Meeting of the IUCN/SSC Polar Bear Specialist Group. Nuuk, Greenland, IUCN, Gland, Switzerland and Cambridge, UK,153 pp.

Mayor, S.J., Schaefer, J.A., 2005. Many faces of population density. Oecologia 145, 276–281.

Melling, H., 2002. Sea ice of the northern Canadian Arctic archipelago. J. Geophys. Res. 107, 3181, doi:10.1029/2001JC001102.

Overland, J.E., Wang, M., Bond, N.A., 2002. Recent temperature changes in the Western Arctic during spring. J. Clim. 15,1702–1716.

Pielke Sr., R.A., Stohlgren, T., Schell, L., Parton, W., Doeksen, N.,Redmond, K., Moeny, J., McKee, T., Kittel, T.G.F., 2002.Problems in evaluating regional, and local trends in temperature: an example from eastern Colorado, USA. Int. J.Clim. 22, 421–434.

Polyakov, I.V., Johnson, M.A., 2000. Arctic decadal and interdecadal variability. Geophys. Res. Lett. 27,4097–4100.

Polyakov, I.V., Bekryaev, R.V., Alekseev, G.V., Bhatt, U., Colony,

R.I., Johnson, M.A., Makshtas, A.P., Walsh, D., 2003a.Variability and trends of air temperature and pressure in the maritime Arctic, 1875–2000. J. Clim. 16,2067–2077.

Polyakov, I.V., Alekseev, G.V., Bekryaev, R.V., Bhatt, U., Colony,R.I., Johnson, M.A., Karklin, V.P., Walsh, D., Yulin, A.V.,2003b. Long-term ice variability in Arctic marginal seas. J.Clim. 16, 2078–2085.

Ramsay, M.A., Stirling, I., 1986. Long-term effects of drugging and handling free-ranging polar bears. J. Wildlife Manage.50, 619–626.

Ray, C., Hastings, A., 1996. Density dependence: are we searching at the wrong spatial scale? J. Anim. Ecol. 65, 556–566.

Rigor, I.G., Colony, R.L., Martin, S., 2000. Variations in surface air temperature observations in the Arctic, 1979–97. J. Clim. 13,896–914.

Rigor, I.G., Wallace, J.M., Colony, R.L., 2002. Response of sea ice to the Arctic Oscillation. J. Clim. 15, 2648–2663.

Russell, R.H., 1975. The food habits of polar bears of James Bay and southwest Hudson Bay in summer and autumn. Arctic28, 117–129.

Rysgaard, S., Nielsen, T.G., Hansen, B.W., 1999. Seasonal variation in nutrients, pelagic primary production and grazing in a high-Arctic coastal marine ecosystem, Young Sound, Northeast Greenland. Mar. Ecol. Prog. Ser. 179, 13–25.

Saucier, F.J., Senneville, S., Prinsenberg, S., Roy, F., Smith, G.,

Gachon, P., Caya, D., Laprise, R., 2004. Modeling the sea ice-ocean seasonal cycle in Hudson Bay, Foxe Basin and Hudson Strait, Canada. Clim. Dyn. 23,303–326.

Scott, P.A., Stirling, I., 2002. Chronology of terrestrial den use by polar bears in Western Hudson Bay as indicated by tree growth anomalies. Arctic 55, 151–166.

Seber, G.A.F., 1973. The Estimation of Animal Abundance and Related Parameters. Charles Griffin and Co., London, UK,506 pp.

Shimada, K., Kamoshida, T., Itoh, M., Nishino, S., Carmack, E.,McLaughlin, F.,Zimmermann, S., Proshutinsky, A., 2006.Pacific Ocean inflow: influence on catastrophic reduction of sea ice cover in the Arctic Ocean. Geophys. Res. Lett. 33, 2005GL025624.

Skinner, W.R., Jefferies, R.L., Carleton, T.J., Rockwell, R.F.,Abraham, K.F., 1998. Prediction of reproductive success and failure in lesser snow geese based on early season climatic variables. Glob. Change Biol. 4, 3–16.

Smith, T.G., 1980. Polar bear predation of ringed and bearded seals in the land-fast ice habitat. Can. J. Zool. 58, 2201–2209.

So¨ derkvist, J., Bjo¨ rk, G., 2004. Ice thickness variability in the Arctic Ocean between 1954–1990, results from a coupled ocean-ice-atmosphere column model. Clim. Dyn. 22,57–68.

Soon, W., 2005. Variable solar irradiance as a plausible agent for multidecadal variations in the Arctic-wide surface air temperature record of the past 130 years. Geophys. Res.Lett. 32, 2005GL023429.

Soon, W., Baliunas, S., 2003. Annual progress report on ‘‘Global Warming’’. Prog. Phys. Georgr. 27 (3), 448–455.

Soon, W., Baliunas, S., Idso, S.B., Kondratyev, K.Ya., Posmentier,E.S., 2001. Modeling climatic effects of anthropogenic carbon dioxide emissions: unknowns and uncertainties.Clim. Res. 18, 259–275.

Steinke, M., Malin, G., Liss, P.S., 2002. Trophic interactions in the sea: an ecological role for climate relevant volatiles? J.Phycol. 38, 630–638.

Stewart, K.M., Bowyer, R.T., Dick, B.L., Johnson, B.K., Kie, J.G.,2005. Density dependent effects on physical condition and reproduction in North American elk: an experimental test. Oecologia 143, 85–93.

Stirling, I., 1997. The importance of polynyas, ice edges, and leads to marine mammals and birds. J. Mar. Syst. 10, 9–21.

Stirling, I., Archibald, W.R., 1977. Aspects of predation of seals by polar bears. J. Fish. Res. Bd. Can. 34, 1126–1129.

Stirling, I., Derocher, A.E., 1993. Possible impacts of climatic warming on polar bears. Arctic 46, 240–245.

Stirling, I., Jonkel, C., Smith, P., Robertson, R., Cross, D., 1977.

The ecology of the polar bear (Ursus maritimus) along the western shore of Hudson Bay. Can. Wild. Serv. Occas. Pap.No. 33.

Stirling, I., Lunn, N.J., Iacozza, J., 1999. Long-term trends in the population ecology of polar bears in western Hudson Bay in relation to climatic change. Arctic 52, 294–306.

Stirling, I., Lunn, N.J., Iacozza, J., Elliott, C., Obbard, M., 2004.Polar bear distribution and abundance on the southwestern Hudson Bay coast during open water season, in relation to population trends and annual ice patterns. Arctic 57,15–26.

Taylor, M.K., Akeeagok, S., Andriashek, D., Barbour, W., Born,E.W.,Calvert, W.,Cluff,H.D., Ferguson, S., Laake, J., Rosing-Asvid, A., Stirling, I., Messier, F., 2001. Delineating Canadian and Greenland polar bear (Ursus maritimus)populations by cluster analysis of movements. Can. J. Zool.79, 690–709.

Taylor, M.K., Laake, J., McLoughlin, P.D., Born, E.W., Cluff, H.D.,Ferguson, S.H., Rosing-Asvid, A., Schweinsburg, R., Messier,F., 2005. Demography and viability of a hunted population of polar bear. Arctic 58, 203–214.

Thompson, D.W.J., Wallace, J.M., 2001. Regional impacts of the Northern Hemisphere annular mode. Science 293,85–89.

Vinje, T., 2001. Anomalies and trends of sea-ice extent and atmospheric circulation in the Nordic Seas during the period 1864–1998. J. Clim. 14, 255–267.

Wallace, J.M., 2000. North Atlantic mode/annular mode: two paradigms—one phenomenon. Q. J. Roy. Meteorol. Soc. 126,791–805.Washington Post, 2005. Experts predict polar bear decline (July7th article by Blaine Harden), p. A03.

Watts, P.D., Hansen, S.E., 1987. Cyclic starvation as reproductive strategy in the polar bear. Symp. Zool. Soc.Lond. 57, 305–318.

Watts, P.D., Ratson, P.S., 1989. Tour operator avoidance of deterrent use and harassment of polar bears. In: Bromley, M.(Ed.), Bear–People Conflict: Proceedings of a Symposium on Management Strategies, Yellowknife, Northwest Territories Department of Renewable Resources, pp. 189–193.

Wiig, Ø., Born, E.W., Garner, G.W. (Eds.), 1995. Polar Bears: Proceedings of the 11th Working Meeting of the IUCN/SSCPolar Bear Specialist Group. IUCN, Gland, Switzerland, and Cambridge, UK 192 pp.

World Wide Fund for Nature, 2002. Vanishing Kingdom—The Melting Realm of the Polar Bear. World Wide Fund for Nature, Gland, Switzerland, 6 pp.

Wunsch, C., 1999. The interpretation of short climate records, with comments on the North Atlantic and Southern Oscillations. Bull. Am. Meteorol. Soc. 80, 245–255.