The environment and permafrost of the Mackenzie Delta area

Abstract

The Mackenzie Delta, prograding northwestwards into the Beaufort Sea, is North America's largest arctic delta. This Holocene feature is bounded by rolling uplands to the east and the Richardson Mountains to the west. Treeline traverses the region, separating the subarctic boreal forest in southern parts from low-shrub tundra and sedge wetlands at the coast. The region is experiencing rapid climate change, and mean annual air temperature has increased by more than 2.58C since 1970. The area was at the margin of the Wisconsinan ice sheet, so that in the uplands the mean annual ground temperature and glacial history control permafrost thickness, which varies from >700 m to <100 m. Ground temperatures in the delta are distinct from the uplands due to the thermal influence of numerous lakes and shifting channels. In the uplands, ground temperatures decrease northwards across treeline in association with a decrease in the thickness of snow cover. Ground temperatures have increased since 1970 in the uplands by approximately 1.58C in association with rising annual mean air temperature. The increase has been less in the delta south of treeline due to the extensive thermal influence of water bodies on ground temperature. However, in the outer delta, the ground is currently more than 2.58C warmer than in 1970. The impact of climate change on permafrost is also evident in the thickness of the active layer, which increased on average by 8 cm at 12 tundra sites on northern Richards Island from 1983-2008.

Sub-seasonal thaw slump mass wasting is not consistently energy limited at the landscape scale

“…A further advantage is that reliable height measurements can also be made when the soil moisture changes and when the surface structure is disrupted -a common occurrence in rapid mass movements. This is in contrast to the closely related technique differential radar interferometry, 20 which is capable of providing synoptic estimates of more subtle elevation changes associated with seasonal and secular thaw subsidence (Liu et al, 2015;Zwieback et al, 2016). Single-pass data, by contrast, are typically not sensitive enough to capture these slow processes over yearly time scales, but instead are ideal for more rapid thermokarst phenomena.…”

Variability and change in the Canadian cryosphere

“…3b). Greater changes in permafrost temperature are observed in the colder tundra environments of the western Arctic, with increases of up to 0.8°C per decade since the early 1970s (Burn and Kokelj 2009;Burn and Zhang 2009). In the eastern Canadian Arctic and in northern Quebec warming has been more recent, beginning in the mid 1990s, and varies from no change in the discontinuous permafrost zone to up to +1.2°C per decade in colder permafrost or at bedrock sites.…”

“…There can be considerable local variability within the continuous permafrost zone, especially in areas such as the Mackenzie Delta due to the abundance of water bodies, seasonal flooding, and variable snow conditions associated with differing vegetation cover (e.g. Burn and Kokelj 2009;Smith et al 2010b). Although terrestrial permafrost was the main focus of the IPY project, recent investigations also provided new information on the thermal state of subsea permafrost in the Mackenzie Delta region (e.g.…”

Detecting Landscape Changes in High Latitude Environments Using Landsat Trend Analysis: 2. Classification

“…The region is entirely underlain by continuous permafrost [10] with 10% or more ice content, creating landforms characteristic of periglacial environments such as ice wedge polygons, thaw slumps and pingos [11]. Shallow lakes and ponds are widespread in the Delta and along the Tuktoyaktuk Peninsula where surficial geology consists mainly of colluvial, alluvial and lacustrine deposits.…”