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The Arctic has warmed at twice the global average over recent decades, which has led to a reduction in the spatial extent and mass balance of snow. The increase in occurrence of winter extreme events such as rain-on-snow, blizzards, and heat waves has a significant impact on snow thickness and density. Dense snowpack conditions can decrease or completely prevent foraging by Peary caribou (Rangifer tarandus pearyi) by creating 'locked pastures,' a situation where forage is present but not accessible under snow or ice. Prolonged and severe weather events have been linked to poor body condition, malnutrition, high adult mortality, calf losses, and major population die-offs in Peary caribou. Previous work has established the link between declines in Peary caribou numbers in the Canadian Arctic Archipelago and snow conditions, however these efforts have been limited by the quality and resolution of data describing snow physical properties in the Arctic. Here, we 1) investigate whether a snow model adapted for the Antarctic (SNOWPACK) can produce snow simulations relevant to Canadian High Arctic conditions, and 2) test snow model outputs to determine their utility in predicting Peary caribou occurrence with MaxEnt modelling software. We model Peary caribou occurrence across three seasons: July--October (summer forage and rut), November--March (fall movement and winter forage), and April--June (spring movement and calving). Results of snow simulations using the Antarctic SNOWPACK model demonstrated that both top and bottom density values were greatly improved when compared to simulations using the original version developed for alpine conditions. Results were also more consistent with field measurements using the Antarctic model, though it underestimated the top layer density compared to on-site measurements. Modelled outputs including snow depth and CT350 (cumulative thickness of snow layers surpassing the critical density value of 350 kg * [m.sup.-3]; a density threshold relevant to caribou) proved to be important predictors of Peary caribou space use in each of the top seasonal models along with vegetation and elevation. All seasonal models were robust in that they were able to predict reasonably well the occurrence of Peary caribou outside the period used to develop the models. This work highlights the need for continued monitoring of snow conditions with climate change to understand potential impacts to the species' distribution. Key words: Arctic; climate change; MaxEnt; Peary caribou; rain-on-snow; snow density; snow depth; locked pastures; SNOWPACK; species distribution modelling L'Arctique s'est rechauffe deux fois plus vite que la moyenne mondiale dans les dernieres decennies. Les modeles de l'etendue spatiale et du bilan de masse de neige montrent une tendance significative vers la baisse. L'augmentation de la frequence des evenements extremes hivernaux tels que la pluie-sur-neige, les blizzards et les vagues de chaleur a un impact significatif sur l'epaisseur et la densite de la neige. Les conditions denses du manteau neigeux diminuent ou empechent completement la recherche de nourriture par le caribou de Peary (Rangifer tarandus pearyi) en creant des << paturages verrouilles >>, une situation ou le fourrage est present, mais non accessible sous la neige ou la glace. Des evenements meteorologiques prolonges et graves ont ete lies a de mauvais etats corporels, de la malnutrition, des mortalites elevees chez les adultes, des pertes de veaux et des evenements massifs de deces chez le caribou de Peary. Des travaux anterieurs ont etabli le lien entre le declin du nombre de caribous de Peary dans l'archipel Arctique canadien et les conditions de neige. Ici, nous tentons premierement de determiner si un modele de simulation de neige (SNOWPACK) adapte a l'Antarctique peut produire des simulations de neige pertinentes aux conditions de l'Extreme-Arctique canadien, et deuxiemement nous mettons a l'epreuve les resultats du modele de simulation de neige pour determiner leur utilite en matiere de prevision de la presence du caribou de Peary a l'aide du logiciel de modelisation de l'habitat MaxEnt. Nous modelisons la presence du caribou de Peary sur trois saisons: juillet-octobre (alimentation estivale et rut); novembre-mars (mouvement d'automne et alimentation hivernale); avril-juin (mouvement printanier et mise bas). Comparativement aux resultats de la version originale confue pour les conditions alpines, les resultats obtenus avec le modele SNOWPACK de l'Antarctique demontrent que les simulations de densite du couvert nival sont grandement ameliorees en utilisant une version adaptee aux conditions polaires, avec une legere sous-estimation des densites de surface. Les sorties du modele d'epaisseur de neige et de CT350 (epaisseur cumulee des couches ayant une densite > 350 kg x [m.sup.-3]; un seuil de densite critique pour le caribou) sont d'importants predicteurs de l'utilisation du territoire par le caribou dans tous les modeles saisonniers avec la vegetation et l'altitude. Tous les modeles saisonniers sont robustes au sens ou les predictions de presence du caribou de Peary sont raisonnablement bonnes en dehors de la periode utilisee pour developper les modeles. Cela souligne l'importance d'une surveillance continue de la neige avec les changements climatiques pour comprendre leurs impacts potentiels sur la repartition de l'espece. Mots cles : Arctique; changements climatiques; MaxEnt; caribou de Peary; pluie-sur-neige; densite de neige; epaisseur de neige; paturages verrouilles; SNOWPACK; modelisation de la distribution des especes, Revise pour la revue Arctic par Nicole Giguere. INTRODUCTION The Arctic has warmed at twice the global average over recent decades because of a number of processes and feedbacks (Serreze [...]

The biotic and abiotic factors responsible for determining ranges of most species are poorly understood. The Canada Jay (Perisoreus canadensis (Linnaeus, 1766)) relies on perishable cached food for over-winter survival and late-winter breeding and the persistence of cached food could be a driver of range limits. We confirmed that the Canada Jay's lower elevational limit on Vancouver Island, British Columbia, Canada, matches that of the subalpine zone (900 m) and then conducted simulated caching experiments to examine the influence of antimicrobial properties of subalpine tree species (biotic) and of temperature (abiotic) on the preservation of cached food. We found that two high-elevation species, yellow cedar (Callitropsis nootkatensis (D. Don) D.P. Little) and Amabilis fir (Abies amabilis Douglas ex J. Forbes), preserved cached blueberries and chicken flesh better than other trees, but they also occurred well below the lower limit of Canada Jays. The effect of temperature was similarly unclear; while food cached at 1150 m retained 17% more mass than food cached at 550 m, there was no difference in percent mass remaining of food placed 70 m above versus 120 m below the Canada Jay's lower elevational limit. Thus, we were unable to provide definitive evidence that either of the proposed abiotic or biotic factors was responsible for setting thelower elevational limit of resident Canada Jays. Key words: food caching, range limit, distribution, climate change, altitudinal distribution, Canada Jay, Perisoreus canadensis. Les facteurs biotiques et abiotiques qui modulent les aires de repartition de la plupart des especes ne sont pas bien compris. Le mesangeai du Canada (Perisoreus canadensis (Linnaeus, 1766)) recourt a de la nourriture perissable mise en cache pour sa survie hivernale et sa reproduction a la fin de l'hiver, et la persistance de la nourriture mise en cache pourrait moduler les limites de son aire de repartition. Nous avons confirme que la limite d'altitude inferieure du mesangeai du Canada dans l'ile de Vancouver (Colombie-Britannique, Canada) coincide avec celle de la zone subalpine (900 m), puis avons mene des experiences de mise en cache simulee afin d'examiner l'influence des proprietes antimicrobiennes d'essences d'arbres subalpines (facteur biotique) et de la temperature (facteur abiotique) sur la preservation de la nourriture mise en cache. Nous avons constate que deux essences de haute altitude, le cypres jaune (Callitropsis nootkatensis (D. Don) D.P. Little) et le sapin gracieux (Abies amabilis Douglas ex J. Forbes), preservent mieux des bleuets et de la chair de poulet mis en cache que d'autres arbres, mais qu'ils se trouvent aussi bien en dessous de la limite inferieure des mesangeais du Canada. L'effet de la temperature est tout aussi mitige; si la nourriture mise en cache a 1150 m d'altitude a conserve 17 % plus de sa masse que la nourriture mise en cache a 550 m, aucune difference n'a ete relevee entre les pourcentages de masse restants de nourriture placee 70 m au-dessus et 120 m en dessous de la limite d'altitude inferieure des mesangeais du Canada. Nous n'avons donc pas ete en mesure d'obtenir des preuves definitives d'un role des facteurs abiotique et biotique proposes dans l'etablissement de la limite inferieure d'altitude des mesangeais du Canada residents. [Traduit par la Redaction] Mots-cles : mise en cache de nourriture, limite de l'aire de repartition, repartition, changement climatique, repartition altitudinale, mesangeai du Canada, Perisoreus canadensis., Introduction With climate change expected to have major effects on the geographic ranges of many plants and animals (Parmesan and Yohe 2003; Oliver et al. 2012; Pearce-Higgins et al. 2017; [...]

High altitude snowfields provide repositories of well-preserved organic remains of considerable antiquity, as spectacular discoveries such as the Similaun Iceman illustrate. In Scandinavia, melting snow patches have been systematically surveyed by volunteer groups for almost a century, and a growing collection of archaeological artefacts has been recovered. Only recently, however, has AMS dating confirmed that some of the finds go back as far as the Neolithic. Here fragments of five Neolithic arrowshafts and a Neolithic longbow discovered in 2010-11 in the Oppdal area of Norway are described. They throw light on Neolithic bow and arrow technology and tangentially on the hunting techniques which may have attracted hunters to these snow patches in search of game. The progressive and accelerated melting of the snow patches in recent years draws attention to processes of climate change and the urgency of discovering and recovering these fragile perishable artefacts. Keywords: Norway, Oppdal, Neolithic, snow patches, archery, climate change, Introduction Snow patches are perennial accumulations of snow and ice, found in the mountains of Norway and other regions of the world at high altitude or latitude. Continually exposed to [...]

Caribou (Rangifer tarandus (L., 1758)) play a central role in the ecology and culture of much of Canada, where they were once the most abundant cervid. Most populations are currently declining, and some face extirpation. In southern Canada, caribou range has retreated considerably over the past century. The ultimate reason for their decline is habitat alterations by industrial activities. The proximate causes are predation and, to a lesser extent, overharvest. The most southerly populations of 'Mountain' caribou are at imminent risk of extirpation. Mountain caribou are threatened by similar industrial activities as Boreal caribou, and face increasing harassment from motorized winter recreational activities. Most populations of 'Migratory Tundra' caribou are currently declining. Although these caribou fluctuate in abundance over decades, changing harvest technologies, climate change, increasing industrial development and human presence in the North raise doubts over whether recent declines will be followed by recoveries. The Peary caribou (Rangifer tarandus pearyi J.A. Allen, 1902), a distinct subspecies endemic to Canada's High Arctic, has suffered drastic declines caused by severe weather, hunting and predation. It faces an increasing threat from climate change. While some questions remain about the reasons for the decline of Migratory Tundra caribou, research has clearly identified several threats to the persistence of 'Boreal', Mountain, and Peary caribou. Scientific knowledge, however, has neither effectively influenced policies nor galvanized public opinion sufficiently to push governments into effective actions. The persistence of many caribou populations appears incompatible with the ongoing pace of industrial development. Le caribou (Rangifer tarandus (L., 1758)) occupe une place centrale dans l'ecologie et la culture de plusieurs regions du Canada. Bien que le caribou ait deja ete le cervide le plus abondant au Canada, la plupart des populations sont presentement en declin et certaines font meme face a l'extinction. Dans les regions du sud du Canada, la distribution du caribou a diminue considerablement au cours du dernier siecle. Le facteur ultime responsable du declin est la modification des habitats par les activites industrielles, alors que les causes proximales sont la predation et, dans une moindre mesure, la surexploitation. Les populations les plus meridionales de caribou Montagnard font face a un risque imminent d'extinction. Le caribou Montagnard est menace par les memes activites industrielles que le caribou de l'ecotype sedentaire et fait face a une augmentation du harcelement par les activites de recreation motorisees en hiver. La plupart des populations de caribou Migrateur sont presentement en diminution. Bien que ces populations fluctuent en abondance au cours des decennies, les modifications des techniques de chasse, les changements climatiques, ainsi que l'augmentation du developpement industriel et de la presence humaine dans les milieux nordiques sement le doute sur la possibilite que les populations recuperent des declins recents. Le caribou de Peary (Rangifer tarandus pearyi J.A. Allen, 1902), une sous-espece endemique au Haut Arctique canadien, a subi des declins drastiques causes par des conditions climatiques difficiles, la chasse et la predation, et fait presentement face a la menace des changements climatiques. Bien que certaines interrogations demeurent sur les raisons du declin du caribou Migrateur, la recherche a identifie plusieurs menaces pour la persistance du caribou des ecotypes sedentaires, Montagnard et de Peary. Les resultats de la recherche, toutefois, n'ont pas influence la legislation efficacement, ni canalise l'opinion publique suffisamment pour forcer des actions concretes de conservation de la part du gouvernement. Le maintien de plusieurs populations de caribou apparait incompatible avec le niveau de developpement industriel actuel., Introduction The status of caribou (Rangifer tarandus (L., 1758)) in Canada is deteriorating, with most current conservation efforts apparently unable to reverse this trend. While concern for this species at [...]

To understand how our global climate will change in response to natural and anthropogenic forcing, it is essential to determine how quickly and by what pathways climate change signals are transported throughout the global ocean, a vast reservoir for heat and carbon dioxide. Labrador Sea Water (LSW), formed by open ocean convection in the subpolar North Atlantic, is a particularly sensitive indicator of climate change on interannual to decadal timescales (1-3). Hydrographic observations made anywhere along the western boundary of the North Atlantic reveal a core of LSW at intermediate depths advected southward within the Deep Western Boundary Current (DWBC) (4-9). These observations have led to the widely held view that the DWBC is the dominant pathway for the export of LSW from its formation site in the northern North Atlantic towards the Equator (10,11). Here we show that most of the recently ventilated LSW entering the subtropics follows interior, not DWBC, pathways. The interior pathways are revealed by trajectories of subsurface RAFOS floats released during the period 2003-2005 that recorded once-daily temperature, pressure and acoustically determined position for two years, and by model-simulated 'e-floats' released in the subpolar DWBC. The evidence points to a few specific locations around the Grand Banks where LSW is most often injected into the interior. These results have implications for deep ocean ventilation and suggest that the interior subtropical gyre should not be ignored when considering the Atlantic meridional overturning circulation., Profiling floats (12) released in the Labrador Sea during the 1990s showed little evidence of southward export of LSW in the DWBC (13-16). This result was surprising because the DWBC [...]

The population cycles of rodents at northern latitudes have puzzled people for centuries (1,2), and their impact is manifest throughout the alpine ecosystem (2,3). Climate change is known to be [...]

Abstract: We estimated the impact of global climate change on lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) site productivity in Alberta based on the Alberta Climate Model [...]

Abstract: The variability of maximum active layer thickness in boreal and tundra environments has important implications for hydrological processes, terrestrial and aquatic ecosystems, and the integrity of northern infrastructure. For [...]

ACCORDING TO THE World Health Organization, zoonoses are diseases naturally transmitted to people from non-human vertebrates. Even before the current concerns about climate change emerged, it was well established that [...]

IMAGINE THE PULSES of biological discovery as a neural net. The neurons are hubs, fields of study, connected in a tangled and ever-changing web of knowledge. Every so often, a [...]

Natural England has defended its research into how to adapt to rising sea levels caused by climate change. Chairman Martin Doughty has responded to criticism of the agency's emerging policy [...]

A new wave of nuclear power stations situated in coastal locations will be vulnerable to extreme weather as a result of climate change, Greenpeace has warned. The campaign group argued [...]