Search

Ground ice distribution and abundance have wide-ranging effects on periglacial environments and possible impacts on climate change scenarios. In contrast, very few studies measure ground ice in the High Arctic, especially in polar deserts and where coarse surficial material complicates coring operations. Ground ice volumes and cryostructures were determined for eight sites in a polar desert, near Resolute Bay, Nunavut, chosen for their hydrogeomorphic classification. Dry, unvegetated polar desert sites exhibited ice content close to soil porosity, with a Key words: ground ice, polar desert, permafrost, Arctic, geocryology, geomorphology. La répartition spatiale et l'abondance de la glace de sol ont d'importants effets sur les milieux périglaciaires et de possibles impacts sur les scénarios de changements climatiques. Très peu d'études mesurent cependant la glace de sol dans le Haut Arctique, en particulier dans les déserts polaires et là où des matériaux meubles grossiers rendent le carottage difficile. Les volumes et les cryostructures de la glace de sol ont été déterminés dans huit sites dans un désert polaire à proximité de Resolute Bay (Nunavut), sélectionnés selon leur classification hydrogéomorphologique. Les sites de désert polaire secs et exempts de végétation présentaient des teneurs en glace semblables aux valeurs de porosité du sol, ainsi qu'une zone de transition riche en glace de < 45 cm d'épaisseur. Dans les sites en milieu humide, des cryostructures suspendues et des cryofaciès dominés par la glace (de teneur en glace au moins deux fois plus grande que la porosité) prédominaient dans les deux premiers mètres du pergélisol. La saturation en glace moyenne du sol dans ces sites était de 1,8 à 20,1 fois plus grande que leur porosité, atteignant un facteur de plus de 2 ordres de grandeurs à une échelle verticale de ~10 cm. Les teneurs en glace les plus importantes ont été observées dans des sites qui étaient historiquement des milieux humides submergés caractérisés par un apport de sédiments, une disponibilité soutenue d'eau et un accroissement syngénétique et quasi-syngénétique du pergélisol. L'enrichissement qui se produisit surtout par aggradation de glace sous le front de dégel et par un engel vers le haut, causant du soulèvement gélival et formant des plateaus lithalsiques. La plupart des sites démontraient des indices cryostratigraphiques de dégradation de pergélisol. Dans le cas des milieux humides, cette dégradation est conséquentielle, car ces lieux sont des oasis opérant les fonctions essentielles d'écologie, d'hydrologie et des cycles des nutriments et contaminants. [Traduit par la Rédaction] Mots-clés : glace de sol, désert polaire, pergélisol, Arctique, géocryologie, géomorphologie., Introduction Ground ice formation and abundance is a foundational topic of geocryology. Among the focuses, knowing the spatial distribution of ground ice and identifying ice-rich areas is an important issue [...]

To gain better insight into the cascading impact of warming-induced changes in the physical landscape on biodiversity, it is crucial to better understand links between abiotic and ecological processes governing species distribution. Abiotic processes shaping the physical characteristics of the environment could significantly influence predator movements in the landscape and ultimately affect biodiversity through interspecific interactions. In the Arctic tundra, the main terrestrial predator (Arctic fox) avoids patches of wetlands composed of ponds with islets that can act as refuges for prey. Little is known about the geomorphological processes generating islets selected by prey species. Our study aimed to identify (i) the physical characteristics of islets selected by Arctic-nesting birds and (ii) the geomorphological processes generating islets available in the landscape. Over two breeding seasons, we determined the occurrence of nesting birds (cackling goose, glaucous gull, and red-throated loon) on islets (N=396) found over a 165 km 2 area on Bylot Island (Nunavut, Canada). Occupied islets were located further away from the shore (10.6 m ± 7.3 SD vs. 7.4 m ± 6.8 SD) and surrounded by deeper water (33.6 cm ± 10.6 SD vs. 28.1 cm ± 11.5 SD) than unoccupied islets. As expected, all three bird species selected islets less accessible to Arctic foxes, with nesting occurrence increasing with distance to shore and water depth around islets. Based on high-resolution satellite imagery and field observations, we found that ice-wedge polygon degradation generated the majority of islets (71 %) found in the landscape. Those islets were on average farther from the shore and surrounded by deeper water than those generated by other processes. As polygon degradation is projected to accelerate in response to warming, new refuges will likely emerge in the Arctic landscape, but current refuges could also disappear. Changes in the rate of polygon degradation may thus affect Arctic tundra biodiversity by altering predator–prey interactions. [ABSTRACT FROM AUTHOR]

Ponds and lakes are abundant in Arctic permafrost lowlands. They play an important role in Arctic wetland ecosystems by regulating carbon, water, and energy fluxes and providing freshwater habitats. However, ponds, i.e., waterbodies with surface areas smaller than 1. 0 × 104ĝ€m2, have not been inventoried on global and regional scales. The Permafrost Region Pond and Lake (PeRL) database presents the results of a circum-Arctic effort to map ponds and lakes from modern (2002-2013) high-resolution aerial and satellite imagery with a resolution of 5ĝ€m or better. The database also includes historical imagery from 1948 to 1965 with a resolution of 6ĝ€m or better. PeRL includes 69 maps covering a wide range of environmental conditions from tundra to boreal regions and from continuous to discontinuous permafrost zones. Waterbody maps are linked to regional permafrost landscape maps which provide information on permafrost extent, ground ice volume, geology, and lithology. This paper describes waterbody classification and accuracy, and presents statistics of waterbody distribution for each site. Maps of permafrost landscapes in Alaska, Canada, and Russia are used to extrapolate waterbody statistics from the site level to regional landscape units. PeRL presents pond and lake estimates for a total area of 1. 4 × 106ĝ€km2 across the Arctic, about 17ĝ€% of the Arctic lowland ( < ĝ€300ĝ€mĝ€a.s.l.) land surface area. PeRL waterbodies with sizes of 1. 0 × 106ĝ€m2 down to 1. 0 × 102ĝ€m2 contributed up to 21ĝ€% to the total water fraction. Waterbody density ranged from 1. 0 × 10 to 9. 4 × 101ĝ€kmĝ'2. Ponds are the dominant waterbody type by number in all landscapes representing 45-99ĝ€% of the total waterbody number. The implementation of PeRL size distributions in land surface models will greatly improve the investigation and projection of surface inundation and carbon fluxes in permafrost lowlands. Waterbody maps, study area boundaries, and maps of regional permafrost landscapes including detailed metadata are available at https://doi.pangaea.de/10.1594/PANGAEA.868349.

Thermo-erosion gullies (TEGs) are one of the most common forms of abrupt permafrost degradation. They generally form in ice-wedge polygonal networks where the interconnected troughs can channel runoff water. Although TEG can form within a single thawing season, it takes them several decades for their complete stabilization. While the inception of TEGs has been examined in several studies, the processes of their stabilization remain poorly documented, especially the ground ice patterns that form following permafrost aggradation in stabilizing TEGs. For this study, we investigated the impacts of two TEGs in the Canadian High Arctic (Bylot Island, NU, Canada) on ground ice content, cryostratigraphic patterns, and geomorphology to examine permafrost recovery following thermal erosion in ice-wedge polygonal tundra. We sampled 17 permafrost cores from two TEGs – one still active (since 1999) and one stabilized (>100 years old) – to describe the surface conditions, interpret the cryostratigraphic patterns, and characterize the state of permafrost after TEG stabilization. We observed that although the TEG caused discernable cryostratigraphic patterns, ground ice content and active layer thickness of the TEGs were comparable to measurements made in undisturbed conditions. We also noted that once stabilized, TEGs permanently (at the Anthropocene scale) alter landscape morphology and hydrological connectivity. We concluded that although the formation of a TEG has profound effects on the short/medium term and leaves near permanent geomorphological and hydrological scars in periglacial landscapes, on the long term, High Arctic permafrost can recover and return to geocryological conditions similar to those pre-dating the initial disturbance. This suggests that in stable environmental conditions undergoing natural variability, permafrost can persist longer than the geomorphological landforms in which it forms. [ABSTRACT FROM AUTHOR]

To gain better insight into the cascading impact of warming-induced changes in the physical landscape on biodiversity, it is crucial to establish stronger links between abiotic and ecological processes governing species distribution. Abiotic processes shaping the physical characteristics of the environment could significantly influence predator movements in the landscape and ultimately affect biodiversity through interspecific interactions. In the Arctic tundra, the main terrestrial predator (Arctic fox) avoids patches of wetlands composed of ponds with islets that can act as refuges for prey. Little is known about the geomorphological processes generating islets selected by prey species. Our study aimed to identify i) the physical characteristics of islets selected by Arctic-nesting birds and ii) the geomorphological processes generating islets available in the landscape. Over two breeding seasons, we determined the occurrence of nesting birds (Glaucous gull, Cackling goose, Red-throated loon) on islets (N=396) found over a 150 km2 area on Bylot Island (Nunavut, Canada). Occupied islets were located further away from the shore (10.6 m ± 7.3 vs 7.4 m ± 6.8) and surrounded by deeper water (33.6 cm ± 10.6 vs 28.1 cm ± 11.5). As expected, all three bird species selected islets less accessible to Arctic foxes, with nesting occurrence increasing (linearly or nonlinearly) with distance to shore and/or water depth around islets. Based on high-resolution satellite image and field observations, we found that ice-wedge polygon degradation generated the majority of islets (71 %) found in the landscape. Those islets were on average farther from the shore and surrounded by deeper water than those generated by other processes. As polygon degradation is projected to accelerate in response to warming, new refuges will likely emerge in the Arctic landscape, but current refuges could also disappear. Changes in the rate of polygon degradation may thus affect Arctic tundra biodiversity by altering predator-prey interactions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ground ice distribution and abundance have wide-ranging effects on periglacial environments and possible impacts on climate change scenarios. In contrast, very few studies measure ground ice in the High Arctic, especially in polar deserts and where coarse surficial material complicates coring operations. Ground ice volumes and cryostructures were determined for eight sites in a polar desert, near Resolute Bay, Nunavut, chosen for their hydrogeomorphic classification. Dry, unvegetated polar desert sites exhibited ice content close to soil porosity, with a <45 cm thick ice-enriched transition zone. In wetland sites, suspended cryostructures and ice dominated cryofacies (ice content at least 2× soil porosity values) were prevalent in the upper ∼2 m of permafrost. Average ground ice saturation at those locations exceeded porosity values by a factor between 1.8 and 20.1 and by up to two orders of magnitude at the ∼10 cm vertical scale. Sites with the highest ice contents were historically submerged wetlands with a history of sediment supply, sustained water availability, and syngenetic and quasi-syngenetic permafrost aggradation. Ice enrichment in those environments were mainly caused by the strong upward freezing potential beneath the thaw front, which, combined with abundant water supply, caused ice aggradation and frost heaving to form lithalsa plateaus. Most of the sites already expressed cryostratigraphic evidence of permafrost degradation. Permafrost degradation carries important ecological ramifications, as wetland locations are the most productive, life-supporting oases in the otherwise relatively barren landscape, carrying essential functions linked with hydrological processes and nutrient and contaminant cycling. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)