Holes of Refuge

Global cooling?

Temperatures are rising in many areas of the Arctic but in some areas the winters are becoming cooler due to abrupt climate change. Perpared by the Arctic Climate Research Centre at the University of Illinois

Contrary to the name global warming, we do not see temperatures increasing everywhere in the world. In the Arctic region western North America and Siberia are following the global trend of warming, but in areas of Hudson Bay and Greenland the temperature on average has been decreasing over the last 50 years during the winter months [1]. Ecosystems in these areas and the organisms that live there may become threatened by this climate cooling. Reserachers are still working on understanding the causes of the cooling, including changing patterns in ocean and air currents due to climate change[2]. In many areas they have experienced an average decrease in temperature of 4°C [1]. This decrease in temperature may not sound like a large amount, but it is enough to disturb the natural cycles of the Arctic, and the unqiue ecosystems found there.

An island of water

One of the most extraordinary systems of the Arctic that is being threatened by climate change are polynyas, which is the Russian word for ice hole. These are open areas of water surrounded by pack ice. They occur where ocean currents, wind, and upwelling warm water prevent ice from forming at the surface [3]. In the Arctic Ocean these open areas can be surrounded by sea ice that is greater than 2 meters thick! Many Arctic polynyas are small at only a few square kilometers, and some are large, such as the North Water Polynya, which is about 50,000 km² [4]. These regions are important to many local species such as polar bears, marine mammals, and seabirds [3]. Many animals have adapted to not migrate south during the winter months, and instead use polynyas as refuge from the miles and miles of ice and snow [5].

In some areas abrupt climate change is contributing to climate cooling in areas such as south east Hudson's Bay where polynyas are freezing over more often than seen in the past. For the species that depend on these areas this means that their holes of refuge disappear when needed most. While in other areas climate change is causing ploynyas to open earlier in the season. This may lead to increased primary productivity in some areas, but the reduction sea ice will have negative impacts on ice dependant species.

Very productive areas

Common eiders, Somateria mollissima, packed tightly on a Polynya in the Belcher Islands courtesy of Joel Heath.

During the warmer months, these open areas of water have higher then average primary productivity, which is thought to be the main reason why many animals congregate there. The algae and phytoplankton, which feed the upper levels of the food chain, have been observed to start blooming 2 months earlier in polynyas than nearby waters covered with ice [3]. With a higher level of primary production, scientists have observed double the amount of ringed seals around polynyas when compared to other areas, and polar bears mature faster and have healthier young [3].

Marine birds are also highly dependant on polynyas. Many of the major nesting colonies of seabirds in the Canadian Arctic are located beside a recurring polynya. The North Water Polynya alone sustains tens of millions of birds that come to nest nearby. [3]

Polynya dependence

Polynyas are threatened by warmer temperatures throughout much of the Arctic. These ice edges provide areas for mating, spawning and feeding for many species. The amount of phytoplankton found in polynyas make them great areas for fish species to also thrive. Arctic Cod are dependent on polynyas for food and shelter. At six months of age, the small cod inhabit cracks in sea ice where plankton prey are plentiful. The small breaks in the sea ice also provide the fish with shelter from predators like seabirds and seals [6]. One of the concerns of warmer temperatures in the Arctic is that many polynyas will disappear with the melting of the ice.

Common eiders, S. mollissima, in Eastern Hudson's Bay courtesy of Joel Heath. Eiders are having to battle the cold, with some becoming frozen on the waterin the extreme cold of the Arctic winter.

One bird in particular is highly dependant on polynyas is the Common Eider. This duck species spends all year in the Arctic. In the winter while many other birds travel south this species stays on the open water patches in the sea ice. The Inuit of the Belcher Islands, in south eastern Hudson Bay depend on the harvest of the Common Eider. Joel Heath, a graduate student from Simon Fraser University, is working with the community of Sanikiluaq to better understand how these birds are being impacted by arbupt climate change, and the shrinking of the local polynyas during the colder than normal winters. The people of the Sanikiluaq use these birds as a food source, to make clothing, and the down for warm insulation against the winter cold. With more extreme cold winter days [2] in the last decade many polynyas are freezing over more and more resulting in declines in eider populations [7]. When the ice cover increased and reduces the polynya size the eiders can not feed on the bottom and may even become frozen into the icy edges.

People need them, too.

First Nations people of the north have also depended on the polynyas to support life throughout the cold winter months. Archaeologists hypothesize that these northern waters were able to support human colonies because of the highly productive polynyas. Archaeological sites throughout the Arctic show a large amount of settlements that specialized in hunting marine mammals near recurring polynyas [8] . The Inuit of the Arctic today still rely on these areas of refuge to hunt and trap animals throughout the winter [5] .

While global warming may seem like a positive thing to some with sunny weather moving north, the climate is not changing equally around the earth. Many think of global warming when we think climate change but in reality with abrupt climate change we are going to experience more extremes in climate, including extremes in cold. Climate disruptions are making life for many species a challenge, and environments are changing so rapidly that many organisms can not keep up. In the north this means that an entire set of ecosystems may be eliminated in some areas not because of the heat, but because the lack of it.

Polynya lesson plan

1. Schrank, W.E., The ACIA, climate change and fisheries. Marine Policy, 2007. 31 : p. 5-18.

2. Vavrus, S., et al., The behaviour of extreme cold air outbreaks under greenhouse warming. International Journal of Climatology, 2006. 26: p. 1133-1147.

3. Stirling, I., The importance of polynyas, ice edges, and leads to marine mammals and birds. Journal of Marine Science, 1997. 10 : p. 9-21.

4. What's a polynya , International North Water Polynya Study.

5. Mallory, M.L., et al., Marine birds as indicators of Arctic marine ecosystem health: linking the Northern ecosystem initiative to long-term studies. Environmental Monitoring and Assessment, 2006. 113 : p. 31-48.

6. Fortier, L. et al. Survival of Arctic cod larvae (Boreogadus saida) in relation to sea ice and temperature in the Northeast Water Polynya (Greenland Sea) . Canadian Journal of Fisheries and Aquatic Science, 2006. 63: 1608-1616.

7. Heath, J., Joel Heath, Ph.D. Candidate. 2004, Simon Fraser University.

8. Sila: clue in to climate change. 2006, Canadian Museum of Nature.