Pingo Canadian Landmark

Natural Environment

• Geography
• Geology
• Climate
• Wildlife
• Vegetation

Geography

The Tuktoyaktuk Peninsula represents one of the most unusual landscapes in the Northwest Territories and Canada. In this region, 1350 conical hills called pingos dot the lake-strewn tundra like miniature volcanoes. Striking features on the otherwise relatively flat landscape, these ice-cored hills are unique to permafrost environments. Approximately one quarter of the world's pingos are concentrated in the Tuktoyaktuk Peninsula area.

Pingo Canadian Landmark protects eight pingos in a 16 square kilometer (4,053 acre) area near the community of Tuktoyaktuk. Two pingos, Ibyuk and Split, dominate the skyline. Reaching the height of a 16 storey office tower (49 meters/160 feet), Ibyuk is the tallest pingo in Canada and the second tallest in the world. Ibyuk Pingo is growing at a rate of approximately two centimeters (3/4 inch) per year and is at least 1,000 years old. Other pingos in the landmark range in height from 5 - 36 meters (16-120 feet) and represent various stages of pingo development.

Pingo Canadian Landmark also contains many other features typical of permafrost areas. One of Canada's best examples of exposed massive ground ice is presently found along the coastal bluffs northeast of Peninsula Point. Other permafrost features, such as ice wedges and tundra polygons, are common throughout the area.

Permafrost

Permafrost is ground that remains at or below 0 °C (32 °F) for two or more years. As the climate becomes colder, the thickness and area of permafrost increases. Average annual temperatures of -11 °C (10.4 °F), and colder conditions during the glacial periods, have helped create a thick layer of permafrost in the region. In parts of the Mackenzie delta area, it penetrates over half a kilometer (1,640 feet) into the ground and is over 50,000 years old.

Because the ground temperature near the surface of permafrost terrain rises above freezing in summer, a seasonally-thawed "active layer" forms above the permafrost . The active layer starts to thaw once the snow has melted in June, and is completely frozen again by the end of November. The roots of most plants and the burrows of animals are confined to the active layer.

Beds of Massive Ice

Peninsula Point in Pingo Canadian Landmark is one of the best places in Canada to see an exposed bed of massive ice. Here coastal erosion during storms has exposed part of a hillside, revealing a half-kilometer long wall of tundra-topped ice, 10 meters (33 feet) tall in places.

Massive ice, a lens of frozen groundwater, is found in the upper layers of permafrost. Common throughout the region and reaching over 40 meters (132 feet) in thickness, beds of massive ice, like pingos, usually develop during the growth of permafrost and may be thousands of years old.

At Peninsula Point, the massive ice formed at the end of the last glaciation as permafrost developed, and was fed by water from the underlying unfrozen ground.

Ice Wedges and Tundra Polygons

Ice wedges develop after the ground becomes so cold in winter that it contracts and cracks apart. In spring, snowmelt trickles into the narrow cracks and freezes. These thin, vertical sheets of ice may penetrate as much as five meters (16 feet) into the ground, creating a weak point that is likely to crack again when the temperatures drop in subsequent winters. Repeated cracking and filling with snowmelt leads to the formation of wedge-shaped, vertical masses of ice, in some cases up to three meters (10 feet) wide at the surface.

Several ice wedges connected together create a pattern in the ground called an ice-wedge polygon. Low-centred polygons develop as ice wedges grow, pushing the adjacent ground upward to form a raised rim. When several ice wedges join together, an irregular polygon is created. The raised rim of this polygon tends to trap water, creating a pattern of small wetlands. Low-centred polygons occur where ice wedges are actively growing. A high-centred polygon develops when plant material eventually fills the central wetland area of a low-centred polygon. The flow of water is reversed. Instead of pooling in the center of the polygon, water now runs off into the bordering troughs.

In summer, particularly during snow melt, water flowing along ice wedges can cause these frozen masses to melt and drain, or partially drain, one or two of the region's numerous lakes each year.

Pingos

The presence of numerous lakes in the Tuktoyaktuk Peninsula, most of which are too deep to freeze solid in winter, is key to the formation of the region's famous pingos.

In this area, lakes over two meters (7 feet) deep do not normally freeze solid in winter. The year-round presence of water at the lake bottom buffers the sandy lakebed from frigid winter temperatures. As a result, the permafrost beneath the lake thaws, creating a zone of unfrozen ground sandwiched between the lake and the deeper underlying permafrost.

A pingo forms when one of these lakes drains, or partially drains, and the water's warming effect is removed. Exposed to frigid winter temperatures, the waterlogged sand of the former lakebed freezes and its water expands. The soil's pores cannot hold this greater volume, so excess water is pushed downward ahead of the freezing ground. At the same time, the ground adjacent to the underlying permafrost begins to freeze, forcing excess water upward. With excess water forced into the still unfrozen ground, the water pressure in this part of the lakebed rises. To relieve the pressure, the surface deforms upwards. If there is an area in the lakebed that has relatively thin permafrost, and so is weaker than the surrounding ground, this permafrost is bent upwards, and is supported on a lens of water. A small, cone-shaped hill grows, and after a few years may be recognized as a pingo.

As the lakebed continues to freeze, the hill grows slowly in height, pushed upward by the pressurized water beneath. At the same time, the water in the lens freezes, creating a core of ice for the pingo. The pingo continues to grow while there is still unfrozen ground in the lakebed. Throughout its growth, the pingo is supported by the pressure in the water lens. In a process that may take hundreds of years, the lens of water gradually freezes solid and the pingo stops growing.

When a pingo is growing, the ground stretches to accommodate its increasing surface area. The tundra splits apart in places, forming cracks - usually along the length of the pingo, especially near its summit - that may reach down as far as the ice core. If these cracks are large enough, the top of a pingo will resemble a crater. Sometimes water ponds in the crater, and this may begin to melt the ice core. More commonly, uplift of the sides of the pingo creates steep slopes that may become unstable and begin to erode. If the ice is exposed to the sun, the core will begin to melt. As its main support melts away, the pingo collapses.

When the ice core has completely melted, all that remains is a doughnut-shaped ring of raised tundra enclosing a small round lake. In warmer regions, such as Ireland and the Netherlands, remnants of collapsed pingos have helped scientists determine that the climate was once cold enough in these areas to support a permafrost environment.

Geology

Pingo Canadian Landmark is in the geological structure called the Beaufort-Mackenzie Basin. For at least the last 100 million years, this area has received sediments from the Richardson Mountains and other more or less extinct landforms around the Mackenzie River. The bedrock in the Tuktoyaktuk area formed from these sediments and is made up of both sandstone and shale. The youngest bedrock is the so-called Beaufort Formation, which contains a range of material from gravel-sized particles to clay.

Above the bedrock lie thick deposits of sand, capped by mixed sediments left by the last glacial advance. The sands form two layers. The lower layer is a grey, well-sorted, medium-grained deposit - called the Kidluit Formation - which was probably deposited in a broad alluvial plain. Above these Kidluit sands is a brown, fine-grained layer called the Kittigazuit Formation. This formation is thought to be the deposits of a large delta, but also includes sand that was blown around in the cold, dry climate leading up to the last glaciation. These sands are exposed at Peninsula Point, where Kilutqusiaq Pingo has been cut and eroded by the ocean. They also underlie the massive icy beds found in the area.

Above the sand layers is mixed sediment, called glacial till, which is a direct remnant of the last ice sheet to cover the region. The massive ice at Peninsula Point formed between the Kittigazuit sands and the glacial till. The top of the massive ice lies between one and ten metres below the ground surface. The ice itself contains enough fine sand and silt to make it appear banded.

Climate

Pingo Canadian Landmark averages 140 mm of precipitation per year, less than half the average annual precipitation of B.C.'s Okanagan valley, the badlands of Alberta, or the dry prairie of southern Saskatchewan.

Ice conditions in the Beaufort Sea largely control precipitation in the Tuktoyaktuk area. When the prevailing wind blows over open water in the southern Beaufort Sea, it picks up the moisture necessary for precipitation . As a result, most of the precipitation falls during the summer and early fall when the southern Beaufort Sea is free of ice. During the remainder of the year the sea ice extends to the shoreline, resulting in very little rain or snow.

In summer, morning fog is common along the coast, especially when there is an onshore wind. Although it can recur day after day at this time of year, the fog usually burns off around noon.

Average temperatures in the Tuktoyaktuk area range from -26 °C (-15 °F) in February to 11 °C (52 °F) in July, with subzero temperatures occurring at any time of the year. Summers are very short. Only June, July and August have average temperatures above freezing. However, with 24-hour sunlight, temperatures have been known to reach 30 °C (86 °F) in summer. In winter, temperatures can drop as low as -50 °C (-58 °F).

Wildlife

Due to its relatively small size, very few animals live in the landmark year-round. However, a wide variety of animals move through the landmark or use the area seasonally.

Mammals

Caribou from the Bluenose West and Cape Bathurst herds are occasionally seen feeding in the landmark, and large carnivores such as grizzly bears, polar bears, and wolves may wander through searching for food. However, smaller animals such as arctic foxes, red foxes, and arctic ground squirrels are more commonly found here. The relatively dry sandy slopes of pingos make ideal denning sites for these small mammals.

Birds

The region contains important habitat for nesting and migrating birds, especially waterfowl. During late spring, the area is a stopover site for migrating geese, including brant, lesser snow geese, and greater white-fronted geese. The area is also important habitat for tundra swans and loons. Ducks such as mallard, green-winged teal, king eider, common eider, and oldsquaw are common to the area, as are a variety of gull and shorebird species.

Fish

The shallow waters of the landmark's bays and coastal areas support a variety of fish species, including Pacific herring, arctic cisco, least cisco, burbot, broad whitefish, and inconnu.

Vegetation

Pingo Canadian Landmark is located in the Southern Arctic ecozone - a major transition area between the open spruce forest to the south and the treeless arctic tundra to the north.

The distribution of plants in the landmark is largely dependent on drainage. The dry slopes of pingos provide good habitat for dwarf shrubs. Sedge communities thrive in the wet center of poorly drained, low-centered tundra polygons, while dwarf shrubs colonize the dryer, raised ridges bordering the polygon. In high-centered polygons the plant community is reversed. Dwarf shrubs grow in the dry interior, while sedge communities fill the wet intersecting troughs.

Typical plants of dry areas in the landmark include willow, crowberry, cranberry, Labrador tea, heath, dwarf birch, and cloudberry. Wet area plant communities include sedges, tussocks, reindeer moss, and some willow species.