Global Warming in the North:
Extreme Climate, Unpredictable Change

Author: Jennifer Jozic, Centre for Studies in Agriculture, Law and the Environment Page 1 | Page 2 | Page 3

 

Climate Change and the Canadian High North

Average global surface temperatures have increased by 0.6°C over the past century, with nine of the ten hottest years recorded occurring between 1990 and 2002 (recordings have occurred since 1860). Scientists now expect that the average global surface temperature could rise between 0.6°C – 2.5°C in the next five decades, and as dramatically as 5.8°C in the next century. The Earth’s climate is always changing and rapid climate change has occurred in the past. However, the degree and speed of the climate change that is currently underway is associated with an accrual of carbon dioxide, methane, and nitrous oxide in the atmosphere. The heat-trapping property of these “greenhouse gases” is undisputed and it is widely accepted that human activities have contributed to the accumulation.

Computer modeling suggests that if warming and greenhouse gas levels continue to increase most of the permanent ice pack is likely to melt and be replaced by seasonal winter ice. Although seasonal warming does bring with it increased biological production, the distribution of plant and animal species usually changes. An Arctic meltdown would threaten the productivity of the Arctic Ocean as well as the continued existence of many Arctic animals including walrus, many seal species and polar bears.

Lifestyles under threat.

It has been observed that the extent and thickness of Arctic ice cover has steadily declined, and current permafrost boundaries are projected to continue moving poleward. Thawing permafrost can seriously alter landscape and drainage patterns and can cause severe damage to buildings, transportation infrastructure and pounded lakes.

The Ocean Conveyor and Carbon Cycling

The polar area can be thought of as a "refrigerator” that plays a fundamental role in the driving of ocean currents. Several million cubic kilometres of water sink and move south along the bottom of the Atlantic Ocean, joining what is termed the Ocean Conveyor and eventually resurfacing in the Indian and Pacific oceans. There it is warmed and returned to the Atlantic in a northwards current.

The Ocean Conveyor is also tied to the cycling of carbon because the process of creating deepwater dissolves carbon dioxide from the atmosphere and effectively removes it. When warm, salty water from the North Atlantic is cooled by Arctic water it releases heat into the atmosphere. The water sinks to deeper layers of the ocean and is accompanied by salt (a by-product of sea ice formation).

The Ocean Conveyor appears to have operated reliably for several thousand years. Abrupt climatic changes have occurred in the past, however, and are associated with changes in the volume of sea ice in the North Atlantic. A persistent freshening trend could threaten the continued functioning of the Labrador Sea deepwater formation, stifling the Conveyor Belt and eliminating an important sink for greenhouse gases.

The Tree Line

The tree line, or timber line, is the edge of the habitat at which trees are capable of growing. Generally, the trees continue to grow as far north as they can until the climate becomes too inhospitable for growing. Vegetation at the tree line is often stunted because of weather conditions such as strong winds. The last trees in the ‘line’ are densely tangled bushes. Trees are unable to grow beyond this natural borderline as a result of unsustainable environmental conditions.

From a distance a tree line may look like a sharp, defining cut-off between two areas, but upon closer inspection it becomes clear that the 'line' is a gradual transition zone. It stretches around the globe from Alaska to northern Quebec, and from Norway to the far east of Siberia. In most areas this zone generally spreads over tens of kilometres, but in central Canada the tree line extends over several hundred kilometres.

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The tree line at Churchill.

The tree line corresponds with the southernmost limit of continuous permafrost. In the Arctic, temperatures generally do not increase to the point where the permafrost and ice melt completely away. Softer ground conditions and the vegetation it supports tend to absorb and store heat, making the surrounding climate warmer. The natural reflectivity of the Arctic surface, however, generally prevents warming weather conditions from disrupting the tree line and keeps the area's overall climate stable and predictable. As temperature rises and the permafrost melts away, this defining ‘line’ begins to move north bringing with it new species of trees, wildlife and other organisms.

Climatic conditions create the tree line and, in turn, the location of the tree line can influence the climate in a region. In fact, computer modelling suggests that movement of the tree line in either direction can affect the global climate. As scientists consider the resulting impact a shifting tree line can have on a climate, more attention and concern is being paid to how the tree line might respond to greenhouse warming:

Warming produced by the movement of the tree line north has adverse effects on local populations. Communities near the tree line will have to prepare for the challenges of the encroaching bush, which may include a need to cut paths and create fire breaks.

The northward movement of the tree line creates new concerns.

The Ice Edge Zone

Unique among Earth’s ecosystems, the Arctic ice-edge zone moves northwards in spring and southwards in fall across thousands of kilometres each year. Most Arctic marine species depend upon the presence of this sea ice to exist. Ice algae clings to the underside of the dark ice pack during winter and supports a springtime phytoplankton bloom along the ice edge. The organic material releases the phytoplankton bloom, enriches the floor of the vast Arctic continental shelves and sustains a community of shellfish and other invertebrates. This highly productive ice-edge ecosystem feeds fish species such as Arctic cod and other marine life including walrus, numerous species of seals and cetaceans such as belugas and narwhals. Polar bears and humans hunt the larger animals.

Should sea ice melt rapidly in the spring, withdrawing past the continental shelf areas to the deep ocean of the central Arctic, it would affect animals that use the ice for hunting, birthing and transportation. Walrus, who travel long distances on floating sea ice, using it as a platform to feed on shellfish, may be particularly vulnerable. Polar bears would be threatened by any decline in the seal population. In the Hudson and James bays, polar bears are already required to fast during the four ice-free summer months that they spend ashore, and pregnant females must fast for twice that length of time. Any extension in this ice-free period would increase starvation rates for the Polar bears and decrease birth rates. Many species of seal, like the walrus, are similarly ice-dependent: the spotted seal breeds exclusively at the ice edge in spring; the ringed seal births and nurses its young on sea ice; the harp seal, the ribbon seal and the bearded seal live at the ice edge all year.

Arctic scientist Vera Alexander warns that the overall biological productivity of the arctic seas would be severely reduced by a temperature increase. She goes so far as to claim that “[e]ssentially all the distinctive Arctic animals would disappear." It is expected that the first regions to be affected by the changing climate will be ice-dependent seas that are adjacent to the Arctic Ocean. This indicates that seasonal winter ice could vanish altogether in the Bering Sea, the Sea of Okhotsk, and Hudson’s Bay.

Signs of the shift are already underway. The polar bear population was severely threatened several decades ago, but had been recovering in numbers since the late 1970s. In 1990, strong May winds carried unusually warm air masses from Siberia out over the Arctic Ocean. Continued warmth in June promoted early break-up and consistent winds in July pushed ice away from the Siberian coast and towards the North Pole. By August the ice cover was 21 percent below normal and the low ice conditions persisted into September. No significant sea ice appeared within several hundred kilometres of Wrangel Island, leaving walrus colonies and several hundred polar bears stranded. The bears had no food supply beyond the walrus colonies, and only fully-grown and experienced male polar bears are able to kill walrus. Similar disasters could push polar bears to the brink of extinction.

Sea ice changes are also affecting the Inuit communities. In 1996 Rosemarie Kuptana, President of the Inuit Circumpolar Conference, addressed a meeting of signatories to the Framework Convention on Climate Change:

"…our hunters are noticing changes in our homeland -- such as discolourations and thinning of sea ice, changes in the leads and open water areas, and the presence of animals not previously found in our region ... Highly experienced and knowledgeable hunters have had experiences falling through areas of sea ice they have previously known to be safe."

Communities near her home on Bank Island in the Northwest Territories are being forced to adapt to dramatic landscape changes. This region includes the town of Aklavik.

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