Search

The present article explores the structure of and recent developments in research activities in the polar regions. Based on a bibliographic study of published papers indexed in the ISI Web of Science during the period 1981-2007, we have analyzed trends in publication, scientific disciplines and subdisciplines, coauthorship, and international collaboration within the field of polar research. We have uncovered several rather striking trends. Scientific output in terms of refereed publications has increased far more rapidly in polar research compared to science in general, quadrupling rather than doubling over the surveyed period. There is a nearly 1:1 ratio between papers covering the Arctic relative to the Antarctic, with the vast majority within either the geosciences (40%) or biology (33%). There has been particularly a steep rise in the number of climate-related papers. The U.S.A. is by far the largest contributor to polar research on both the Arctic and the Antarctic, followed by Canada, the U.K., Germany, Norway, and Russia. The number of coauthored papers has grown markedly, reflecting geopolitical shifts and changing national and international funding priorities during the period. We believe our publication-based survey reveals interesting developments in scientific activities and international cooperation in general, and in polar science strategies and priorities in particular. [ABSTRACT FROM AUTHOR]

Subarctic ecosystems are experiencing rapid changes as a result of climate warming and more frequent and severe disturbances. There is considerable uncertainty regarding ecological trajectories following disturbance in forested ecosystems underlain by permafrost because their structure and function is controlled by feedbacks among soil conditions, vegetation, and ground thermal regime. In this paper, we studied post-disturbance ecosystem recovery in an area of discontinuous permafrost 32 years after construction and abandonment of a winter access road in Nahanni National Park Reserve (NNPR). Ecosystem recovery was examined by comparing disturbed (road) and undisturbed (adjacent to the road) sites in the following terrain types: spruce peatland, black spruce parkland, deciduous forest, and alpine treeline terrain. Our field data show that disturbances to discontinuous permafrost terrain can lead to large and persistent changes to ecosystem composition and structure. Our findings indicate that the ecological response of discontinuous permafrost to disturbance and climate warming will depend on interactions between soil conditions and vegetation communities. In instances where disturbance to discontinuous permafrost fundamentally disrupts stabilizing interactions between soil conditions and vegetation communities, we should expect lasting changes to ecosystem structure and function. [ABSTRACT FROM AUTHOR]

Bryophytes are ecologically essential to northern ecosystem restoration after disturbance. In this study, native bryophytes were used to revegetate two Arctic restoration sites. Different propagation types (small, medium, large fragments) and substrates (crushed rock, lake sediment, processed kimberlite in Canada; volcanic silt loam and crushed lava rock in Iceland) with two erosion control treatments (with and without cheesecloth) were evaluated. After two growing seasons, large bryophyte fragments resulted in the greatest density and total and live cover with erosion control and medium fragments resulted in the highest density and species occurrence without erosion control. Erosion control significantly increased live cover, total cover, species occurrence, and density, including a tempering effect on soil volumetric water content and temperature. Substrates with more heterogeneous surfaces (crushed rock, volcanic silt loam, crushed lava rock) yielded higher live cover, density, and spontaneous colonization than more homogeneous substrates (processed kimberlite, lake sediment) and can be more suitable for use in arctic ecosystems revegetation. The positive outcomes in both Canada and Iceland led to the conclusion that bryophyte propagation with large to medium fragments, erosion control with cheesecloth, and substrates with heterogeneous surfaces would be effective restoration approaches where bryophyte revegetation is a focus. [ABSTRACT FROM AUTHOR]

A correction to the article "Temporal and Spatial Dynamics of Ice-Covered Upper Dumbell Lake (Ellesmere Island, Arctic Canada) during the Summer of 1959" that was published in a 2014 issue is presented.

Climate warming in the North could lead to lichen decline within critical woodland caribou habitat. We used repeat measurements of sixty-nine plots over ten years (2007-2008 and 2017-2018) to assess lichen biomass changes under a warming climate along a latitudinal/climatic gradient in northwestern Canada. We compared lichen biomass on sensitive landscape features, including peat plateaux (permafrost-containing bogs), areas of permafrost thaw within the peat plateaux (collapse scars), and low-productivity upland forests occurring on mineral soils. Field-based measures of lichen cover and height were coupled with samples of lichen biomass to develop biomass prediction equations. The optimal model incorporated both cover and height, with landscape feature as a covariate. Although height significantly improved the equation fit, models were successfully developed with cover alone. Modeled lichen biomass differed significantly between landscape features, declining from peat plateau (502 g m-2) to upland forest (54.0 g m-2) and collapse scar (0.690 g m-2) environments. In the absence of permafrost collapse at any monitoring location, lichen biomass declined significantly over the ten years for peat plateaux (-75.6 g m-2) and upland forests (-17.5 g m-2). These results will be important for quantifying landscape-level lichen biomass changes under climate warming in boreal and subarctic environments. [ABSTRACT FROM AUTHOR]

Optimal foraging theory predicts tradeoffs in animals balancing net energy intake and predator avoidance. In particular, overall foraging activity could be low if (1) perception of predation risk is high or (2) abiotic conditions are suboptimal. American pikas ( Ochotona princeps) are small, food-hoarding mammals whose foraging opportunities are restricted by heat and risk of predation. If hiking disturbance is perceived by pikas as predation risk, it could reduce the amount of food stored overwinter, possibly affecting survival. We simulated hiker disturbance events for 48 pikas in Mount Revelstoke and Glacier National Parks, British Columbia, to estimate foraging time lost due to hikers. We tested risk avoidance hypotheses using four indicators of risk behavior: alert distance (DA), flight initiation distance (DF), exit delay (TE), and delay in return to forage (TR). All hiker disturbance events elicited antipredator behaviors in foraging pikas and reduced foraging time; however, when compared to increasing temperatures over 4-6 hour observation periods, the latter best predicted a reduction in pikas' foraging activity. For every 1 °C increase in temperature, pika foraging activity decreased by 3%. Pikas near trails (<50 m) lost an average of 4.1 (SE = 0.6) minutes of foraging time per disturbance event compared to 13.2 (SE = 1.7) minutes lost by pikas with territories >100 m away from trails. Such differences might reflect habituation in pikas undergoing frequent disturbance. Monitoring pika populations for declines would be sensible given projected trends in warming climate and potential increases in hiking traffic. [ABSTRACT FROM AUTHOR]

We report on a limnological study of ice-covered Upper Dumbell Lake (Ellesmere Island, Canada) conducted during the summer of 1959. The lake was vertically profiled for physical (temperature, light), chemical (alkalinity, pH, oxygen, nutrients), and biological (chlorophyll a, gross and net primary productivity) variables on 21 dates spanning from early July to early September. Zooplankton density and age structure were also determined on four dates. Factors such as temperature, alkalinity, pH, and oxygen varied little with depth or over time, whereas nutrients (nitrate, dissolved silica, soluble reactive phosphorus), light, chlorophyll a, and gross and net photosynthesis varied substantially. Comparing July to August, nitrate and light intensity decreased while dissolved silica, chlorophyll a, and gross and net primary production increased, with two distinct peaks in algal biomass occurring over the month of August. Chlorophyll a in this lake was negatively correlated with nitrate concentrations, suggesting uptake of nitrogen as algal biomass increased. The copepod Limnocalanus macrurus was the dominant zooplankton taxon present; the age structure of the population advanced over the summer. This study reveals the dynamic nature of vertical habitat gradients even under the ice of Arctic lakes and provides important baseline data for conditions in an Arctic lake during the mid-20th century. [ABSTRACT FROM AUTHOR]

Although widely distributed throughout Arctic and subarctic regions, thermokarst ponds and lakes remain relatively unexplored regarding geomorphological changes in their catchments and their internal properties in relation to climate change over the past decades. This study synthesizes recent landscape evolution and modern sedimentology of limnologically diverse thermokarst ponds near southeastern Hudson Bay, Canada. Spatio-temporal analysis of permafrost mounds, thermokarst ponds, and vegetation surface areas over the past five decades revealed that the recent climate-induced decrease of permafrost-affected areas was not primarily compensated by thermokarst pond development, but rather by a remarkable increase in vegetation cover. These changes appeared to be modulated by topographical and hydrological gradients at the study site, which are associated with east-ward increasing thickness of postglacial marine deposits. At a more contemporary timescale, physico-chemical measurements made on sedimenting materials (sediment traps) and freshly deposited lacustrine sediments of selected thermokarst ponds revealed striking differences both among ponds and between the oxic epilimnion and the oxygen-depleted hypolimnion. These findings underscore the major influence of local landscape properties and oxycline development on pond sedimentology and geochemistry, such as the transport of detritic particles and the concentration of redox-sensitive elements. [ABSTRACT FROM AUTHOR]

The Hudson Bay Lowlands (HBL) constitute a globally significant carbon pool; the paleoecological record provides an opportunity to investigate long-term drivers of change in carbon accumulation and related changes in vegetation. We present a Holocene record from the Victor Fen site (VM-3-3) in Ontario's HBL to reconstruct vegetation history, quantify rates of carbon accumulation, and determine the role of paleoclimatic drivers. Pollen analysis indicates initiation of peat accumulation over a mineral substrate, accompanied by relatively rapid rates of carbon accumulation, following emergence from the Tyrrell Sea ∼6900 yrs BP. The earliest vegetation assemblage consisted of a tidal marsh, quickly succeeding to a Typha marsh, then a poor fen dominated by Sphagnum and Cyperaceae by 6400 yrs BP. Rapid rates of isostatic uplift at the time likely contributed to these changes. Once established, this fen community persisted without major vegetation change until the most recent century, when the abundance of shrub and Cyperaceae pollen increased, suggesting increasingly minerotrophic conditions. Average rate of long-term carbon accumulation (LORCA) for the whole record (mean = 22.8 g C m-2 yr-1) is similar to other northern peatlands, and higher than the Holocene average for an adjacent bog. Increased precipitation after ∼2400 yrs BP may have contributed to the higher LORCA reconstructed for the late Holocene, but the increased precipitation did not coincide with any apparent changes in vegetation as inferred from pollen assemblages. [ABSTRACT FROM AUTHOR]

We examined the influence of leaf size on forage selection by collared pikas (Ochotona collaris) living in alpine meadows in the Yukon Territory, Canada, by comparing the winter diets of individually recognized pikas to the available vegetation within their territories and by conducting cafeteria-style preference experiments. Pikas consistently preferred forage with larger leaves in the cafeteria trials. They also collected larger leaves from deciduous shrubs and graminoid species compared to other plant types such as lichens and evergreen shrubs for their winter diets. Pikas assessed differences in leaf size when selecting their winter diets and this appears to be an energetically efficient foraging strategy for surviving seasonal food scarcity. [ABSTRACT FROM AUTHOR]

This study explores the physical, chemical and microclimatological properties of soils along a High Arctic glacier foreland and adjacent moraine in relation to the development of biological soil crusts. We examine various edaphic properties: soil temperature, volumetric water content, organic carbon content, and texture in surface samples (∼1 cm) with and without a cover of biological soil crust as well as changes in nitrogen, phosphorus, potassium, organic carbon, pH, volumetric water content, bulk density, and texture in crusted surfaces (<1 cm) and soil cores (5 cm) along a chronosequence following deglaciation. Soil crusts developed within four years of deglaciation and subsequent peaks in crust cover and thickness coincided with an accumulation of nitrogen and organic carbon in the crust. Crusted surfaces had significantly higher volumetric water content, organic carbon, a greater silt and clay fraction, and lower temperature compared to uncrusted soils. A steady supply of water from glacier melt promoted rapid development of biological soil crusts, creating an edaphic environment with enhanced moisture and nutrient properties which contributed to the high rate of vascular plant succession previously observed on this foreland. Results presented in this study are compared with edaphic conditions at other circumpolar sites and glacier forelands. [ABSTRACT FROM AUTHOR]

The combined effects of multiple ecological stressors determine the net impact of global change on environmentally sensitive alpine and polar environments. For example, climate warming and nitrogen deposition both increasingly affect ecosystems at high elevations. We hypothesized that the net impact of warming and nitrogen on alpine plankton differs between consumers and producers because of the greater environmental sensitivity of higher trophic levels. Also, we expected that habitat conditions would mediate the responses of plankton to these two stressors as sediments function as ecological buffers against environmental change. These hypotheses were tested in a growth chamber by applying temperature (8 vs. 15°C) and nitrogen (200 vs. 1000 μg N L-1) treatments to a planktonic alpine community in the presence and absence of sediments obtained from Pipit Lake, Banff National Park, Alberta. A significant nitrogen-temperature interaction affected phytoplankton abundance because the positive effect of fertilization depended on warming. Warming also amplified the effect of nitrogen on herbivores while suppressing the fecundity of omnivores. The presence of sediments suppressed the positive effect of warming on herbivores, but stimulated omnivores. The observed prevalence of non-additive effects highlights the strong potential for global change causing future ecological surprises in alpine environments. [ABSTRACT FROM AUTHOR]

Fresh snow samples were collected following seven snow accumulation events along an altitudinal transect of the Robertson Valley. This glacierized valley is on the eastern slopes of the Canadian Rockies at the Continental Divide and receives precipitation from both westerly (Pacific) air masses and from easterly (upslope) systems. Snow samples were collected over two winter seasons and were analyzed for δ18O, revealing altitudinal gradients that ranged from -0.3%/100 m to +1.8‰/100 m. Five of seven snow events had positive (inverse) isotopic gradients with altitude: 18O enrichment at higher altitudes. Surface and upper-air meteorological data were analyzed to classify the type of weather systems bringing precipitation to the area for each accumulation event. Three storm classifications were developed: westerly, upslope, and mixed/ northwesterly systems. Positive δ18O-elevation gradients were found under strong westerly and northwesterly flow, when the Robertson Valley acts as a leeward slope, while more conventional negative gradients correspond with upslope flow, when easterly winds make the Robertson Valley a windward snow deposition environment. We interpret the inverse isotopic gradients as evidence of ongoing Rayleigh distillation as westerly systems cross the Continental Divide. Position on the Rayleigh distillation curve had a strong influence on the magnitude of δ18O-elevation gradients. [ABSTRACT FROM AUTHOR]

The present extent of glacier ice on Bylot Island, Arctic Canada, is mapped using high-resolution Landsat 7 ETM+ satellite imagery. The island is 43% ice covered, with 4783 km² of ice. Most ice is centered on the northwest-southeast--trending Byam Martin Mountains, flowing outward as radial valley glaciers and piedmont lobes. The largest glacier is 49 km long and 6.5 km wide. The majority of glaciers terminate on land, but many have margins ending in lakes and two calve into the sea. The late summer snowline, mapped from satellite imagery, is highest along the southern and central parts of the island at about 1050 m, with lower values along the east-northeastern margin of the ice down to about 700 m. These snowline-elevation differences suggest a predominant moisture source from the northeast. Several valley glaciers and piedmont lobes have deformed medial moraines and ice-surface foliation suggesting past surge activity. Ten glaciers are interpreted to be of possible surgetype. The modern extent of glaciers is compared with that of two earlier time intervals. First, we have mapped glacier margins in several areas of Bylot Island from aerial photographs acquired in 1958 and 1961. Secondly, former positions of ice fronts are mapped from moraine systems deposited during the Neoglacial maximum and identified on satellite data. Glaciers have retreated from 0.9 to 1.8 km since the Neoglacial maximum about 120 years ago, with most retreat occurring between 1958/1961 and 2001. Approximately 253 km² or 5% of the 1958/1961 ice-covered area has been lost. Overall, marked glacier retreat has occurred, although a few glaciers, possibly of surge-type, show small readvances. This retreat is consistent with observed climate warming in the Canadian Arctic, especially since the 1960s. [ABSTRACT FROM AUTHOR]

Much of the low Arctic is covered with shrubs that are partially buried by snow in winter and become exposed during melt. This study presents measurements and modeling of shortwave radiation reflection and extinction by a deciduous shrub canopy emerging from a melting snowcover in the mountains of the Yukon Territory, Canada. Shrubs shade most of the snow surface at low solar elevation angles, so only a fraction of the incoming radiation reaches the surface, but there is greater direct shortwave transmission to the surface in gaps between shrubs for higher solar elevations. A simple model is developed to incorporate the changing contributions of sun-lit gaps, shaded gaps, and shrubs to the landscape-averaged (areal) transmission and reflection of shortwave radiation. The areal transmissivity and albedo in this model are lower than in a two-stream approximation that neglects gap shading. A simple shadow parameterization is proposed for calculating shrub tundra snowmelt rates and surface energy balances in hydrological and land-surface models. [ABSTRACT FROM AUTHOR]

Over the course of the last century, the 9000-km² "Ellesmere Ice Shelf" (82-83°N, 64-90°W) fragmented into six main ice shelves now totaling 1043 km². This ensemble of thick ice environments lies along the northern coast of Ellesmere Island in the Canadian High Arctic and provides a cryohabitat for microbial communities that occur in association with eolian and glacially entrained sediments on the ice surface. We undertook a comparative analysis of physical, chemical, and biological characteristics of five of the remnant ice shelves including geographic information system (GIS) mapping of ice types. Each of these remnants is a thick (<20 m) mass of ice with substantial sediment overburden that promotes the formation of oligotrophic meltwaters in the summer. Microbiota occurred in all sampled sediment, forming a continuum of abundance from sparse to loosely cohesive and pigmented microbial mats. Using digital images from over-flight transects we determined that 8% of the combined ice-shelf area was suitable microbial mat habitat, and contained an estimated 34 Gg of organic matter stocks for the entire system. A gradient of increasing chlorophyll a, organic content, and conductivity was found from west to east. This is likely related to the surface ice type (meteoric versus marine) and to the relative availability of sediment. Our results indicate that differences in phototrophic community structure (microalgae and cyanobacterial morphotypes) were associated with different ice and microbial mat types. In addition, the relative abundance of dominant taxa was significantly associated with environmental gradients of conductivity, soluble reactive phosphorus, and nitrate and ammonium concentrations. There were distinct differences between each ice shelf with regards to ice type and sediment availability but no differences in taxonomic richness or diversity, indicating little effect of habitat fragmentation on these community attributes. However, the ensemble of ice shelves that compose this unique cryoecosystem remains vulnerable to habitat attrition and complete loss with ongoing climate warming. [ABSTRACT FROM AUTHOR]

Meteorological records from about 30 British Navy ships that overwintered in the Canadian Arctic islands between 1818 and 1859 are the earliest detailed baseline of direct historical data in this region against which modern and future climate trends can be assessed. We describe the types of meteorological instruments and the observational methods employed aboard these ships. For measuring air temperatures, both mercurial and spirit thermometers were used. Observations of atmospheric pressure were made using marine and aneroid barometers. Wind direction and speed were also logged. The Royal Navy's ordered and disciplined daily regime was well-suited to regular scientific observations. Individual instruments on most Navy ships were calibrated against established Royal Observatory standards before and after expeditions. Many recording officers commented on the relative unreliability of spirit thermometers below the freezing point of mercury. Little contemporary written evidence exists regarding absolute accuracy or precision of meteorological instruments taken to the Arctic, but some calibration data are available to assess typical instrument errors between 32° and -388F (0° and -39°C). Our comparison of minimum daily temperatures from four overwintering ships in 1853 and 1854 shows very high correlation coefficients. The mutual consistency of these records implies good instrumental precision. Although the absolute accuracy of temperatures recorded below the freezing point of mercury is in doubt, those above this point are relatively accurate. Guidance on the preferred methods of observing and recording were codified in, for example, the Admiralty's Manual of Scientific Enquiry (Herschel, 1851). Meteorological registers were regarded as official documents that were, as far as possible, required to be complete and no attempt was to be made to fill in missing data. The need to screen or cover instruments from both solar and terrestrial radiation was also recognized from the earliest expeditions. It was not until the 1850s that standardizing the exposure of thermometers was resolved through the introduction of louvered screens. This unique set of ships' meteorological registers presents opportunities to investigate a variety of meteorological parameters for the Canadian High Arctic in the 19th century, allowing quantitative assessment of change relative to contemporary climate. [ABSTRACT FROM AUTHOR]