Search

We evaluated the spatial distribution and morphological variability of thermal contraction crack polygon (TCCP) networks across Nunavik, a 440,000‐km2 region of northern Québec that spans the northward transition from discontinuous to continuous permafrost. A population of 4,567 TCCP sites was sampled and analyzed from 80,737 georeferenced high‐resolution aerial photographs and 264,504 km2 of ESRI satellite basemaps. For each site, six parameters were inventoried and compiled into a database: (a) network geometric arrangement; (b) intersection angles; (c) number of subdivisions and nested polygons (referred to as generations of development); (d) dominant polygon morphology; (e) surficial geology; and (f) vegetation cover. Statistical analyses of the tabulated data revealed a strong association between Holocene glacial, glacio‐fluvial, fluvial, marine, and organic landforms and the different intersections angles in the networks, providing insight into how the processes of thermal contraction cracking function and manifest geomorphically across varied permafrost landscapes. Orthogonal polygons (intersection angle of 90°) dominate on flat terrains where the thermo‐mechanical stresses are probably spatially homogeneous. Hexagonal (angles of 120°) and poorly structured polygons tend to form where topography variability probably generates heterogeneous heat flow patterns and thermo‐mechanical stresses in the ground, resulting in irregular cracking patterns. [ABSTRACT FROM AUTHOR]

Simulations with a one‐dimensional heat transfer model (TONE) were performed to reproduce the near surface ground temperature regime in the four main types of soil profiles found in Narsajuaq River Valley (Nunavik, Canada) for the period 1990–2100. The permafrost thermal regime was simulated using climate data from a reanalysis (1948–2002), climate stations (1989–1991, 2002–2019) and simulations based on climate warming scenarios RCP4.5 and RCP8.5 (2019–2100). The model was calibrated based on extensive field measurements made between 1989 and 2019. The results were used to estimate when soil thermal contraction cracking will eventually stop and to forecast the melting of ice wedges due to active‐layer thickening. For the period 1990–2019, all soil profiles experienced cracking every year until 2006, when cracking became intermittent during a warm period before completely stopping in 2009–2010, after which cracking resumed during colder years. Ice‐wedge tops melted from 1992 to 2010 as the active layer thickened, indicating that top‐down ice‐wedge degradation can occur simultaneously with cracking and growth in width. Our predictions show that ice wedges in the valley will completely stop cracking between 2024 and 2096, first in sandy soils and later in soils with thicker organic horizons. The timing will also depend on greenhouse gas concentration trajectories. All ice wedges in the study area will probably experience some degradation of their main body before the end of the century, causing their roots to become relict ice by the end of the 21st century. [ABSTRACT FROM AUTHOR]

Boulder barricades are poorly documented Holocene coastal landforms of Arctic and Subarctic regions. To understand the terrain factors and coastal processes explaining the occurrences of boulder barricades, we mapped and described these periglacial landforms along the emerging hypertidal coast of Ungava Bay, in Nunavik, northern Quebec, Canada. This study examines the spatial distribution as well as the different types and configurations of boulder barricades, and identifies and discusses the formation processes of these ridges, which are affected by the ongoing glacial isostatic adjustment (GIA) process. We distinguish four types of ice-formed boulder ridges: low-tide-, intertidal-, high-tide- and raised boulder barricades. Our results highlight the importance of specific terrain factors (coastal configurations, intertidal and backshore slopes, widths of intertidal zones, susceptibility to coastal erosion) and related coastal processes (ice-pushing and ice-rafting intensified by strong tidal currents), forming these different types of barricades. Due to the GIA process, this coastal region is characterized by a large number of evolutionary sequences (i.e. flights) of boulder barricades, from the intertidal zone to the emerged landscape. These sea-ice-related landforms have significant effects on the coastal geomorphology of the Ungava Bay region by successively enclosing and isolating many ponds and lakes. [ABSTRACT FROM AUTHOR]