Polar Research (E-Journal)
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Historical ablation rates on south-east Greenland glaciers measured in the 1933 warm summer
No full textIce ablation rates measured on four glaciers in south-east Greenland in summer 1933 are recovered from an old field book of geologist K. Milthers. These unpublished ablation data are among the first measured in Greenland and were obtained during a warm period comparable to that of recent years. Ablation rates of up to 45 mm ice eq. d−1 were observed. Using the Tasiilaq meteorological record, we calculate degree-day factors of ca. 3–5 mm ice eq. d−1°C−1. Comparing these results with 1996–2012 observations at one of Milthers’ glaciers (Mittivakkat), we find that ablation rates and degree-day factors are significantly higher (61±50%) in recent years. We speculate this to be due to a reduction in surface albedo, and perhaps the retreat of the glaciers out of the cold maritime inversion layer. Our findings suggest that using a temperature-index method that assumes constant degree-day factors may produce inaccurate long-term ablation estimates for south-east Greenland glaciers, further emphasizing the value of the rare 1933 measurements for validation of ablation models.Keywords: Surface mass balance; positive degree-days; climate change; Mittivakkat Glacier; Milthers; 7th Thule Expedition.(Published: 12 July 2016)To access the supplementary material for this article, please see the supplementary file in the column to the right (under Article Tools).Citation: Polar Research 2016, 35, 28858, http://dx.doi.org/10.3402/polar.v35.2885
Algal biomass and pigments along a latitudinal gradient in Victoria Land lakes, East Antarctica
No full textIt is generally accepted that Antarctic terrestrial diversity decreases as latitude increases, but latitudinal patterns of several organisms are not always as clear as expected. The Victoria Land region is rich in lakes and ponds and spans 8 degrees of latitude that encompasses gradients in factors such as solar radiation, temperature, ice cover and day length. An understanding of the links between latitudinally driven environmental and biodiversity changes is essential to the understanding of the ecology and evolution of Antarctic biota and the formulation of hypotheses about likely future changes in biodiversity. As several studies have demonstrated that photosynthetic pigments are an excellent, although underused, tool for the study of lacustrine algal communities, the aim of the present study was to investigate variations in algal biomass and biodiversity across the latitudinal gradient of Victoria Land using sedimentary pigments. We test the hypothesis that the biodiversity of freshwater environments decreases as latitude increases. On the basis of our results, we propose using the number of sedimentary pigments as a proxy for algal diversity and the sum of chlorophyll a and bacteriochlorophyll a with their degradation derivatives as an index of biomass. Overall, our data show that biomass and diversity decrease as latitude increases but local environmental conditions, in particular, natural levels of eutrophy, can affect both productivity and diversity.Keywords: Biodiversity; photosynthetic pigments; proxy; continental Antarctica; sediments; biogeography.(Published: 13 May 2016)To access the supplementary material for this article, please see the supplementary files in the column to the right (under Article Tools).Citation: Polar Research 2016, 35, 20703, http://dx.doi.org/10.3402/polar.v35.2070
Arctic plants are capable of sustained responses to long-term warming
No full textPrevious studies have shown that Arctic plants typically respond to warming with increased growth and reproductive effort and accelerated phenology, and that the magnitude of these responses is likely to change over time. We investigated the effects of long-term experimental warming on plant growth (leaf length) and reproduction (inflorescence height, reproductive phenology and reproductive effort) using 17–19 years of measurements collected as part of the International Tundra Experiment (ITEX) at sites near Barrow and Atqasuk, Alaska. During the study period, linear regressions indicated non-significant tendencies towards warming air temperatures at our study sites. Results of our meta-analyses on the effect size of experimental warming (calculated as Hedges’ d) indicated species generally responded to warming by increasing inflorescence height, increasing leaf length and flowering earlier, while reproductive effort did not respond consistently. Using weighted least-squares regressions on effect sizes, we found a significant trend towards dampened response to experimental warming over time for reproductive phenology. This tendency was consistent, though non-significant, across all traits. A separate analysis revealed significant trends towards reduced responses to experimental warming during warmer summers for all traits. We therefore propose that tendencies towards dampened plant responses to experimental warming over time are the result of regional warming. These results show that Arctic plants are capable of sustained responses to warming over long periods of time but also suggest that, as the region continues to warm, factors such as nutrient availability, competition and herbivory will become more limiting to plant growth and reproduction than temperature.Keywords: Species traits; International Tundra Experiment; meta-analysis; plant–climate interactions; tundra vegetation; warming response.(Published: 5 May 2016)To access the supplementary material for this article, please see the supplementary file in the column to the right (under Article Tools).Citation: Polar Research 2016, 35, 25405, http://dx.doi.org/10.3402/polar.v35.2540
Wing and body size polymorphism in populations of the stonefly Arcynopteryx dichroa McL. (Plecoptera: Perlodidae) in the Ural Mountains, Russia
No full textSpecimens from five Arcynopteryx dichroa (McL.) populations were examined to study wing length and body size at different latitudes and altitudes. In northern Europe, female A. dichroa are usually long winged, while males are short winged. During the past 20 years, only two short-winged populations have been found, in a nameless lake, herein called Lake Ozernoe, and in Bolshaya Lagorta Lake, in Russia’s Ural Mountains. In the isolated population of Ozernoe Lake (850 m a.s.l.), both sexes were micropterous. In Bolshaya Lagorta Lake (380 m a.s.l.), females were brachypterous. However, at a higher altitude (560 and 760 m a.s.l.), a population was found with macropterous females. Specimens of both short-winged populations had smaller body length than long-winged populations. Our findings give limited support to the idea that stonefly wings are reduced with altitude and latitude and more support to the supposition that small wing size is associated with population isolation resulting from lengthy geological isolation.Keywords: Wing length; short-winged population; Urals; mountain lakes; latitude; isolation.(Published: 21 April 2016)To access the supplementary material for this article, please see the supplementary files in the column to the right (under Article Tools).Citation: Polar Research 2016, 35, 26596, http://dx.doi.org/10.3402/polar.v35.2659
Parasites of the Antarctic toothfish (Dissostichus mawsoni Norman, 1937) (Perciformes, Nototheniidae) in the Pacific sector of the Antarctic
No full textThe Antarctic toothfish (Dissostichus mawsoni Norman, 1937) is one of the main target species of commercial fisheries in the Antarctic. It is an endemic and is found along the shelf of Antarctica, as well as on the slopes of seamounts, underwater elevations and islands in the sub-Antarctic. It feeds on a variety of fish and cephalopods and can be an intermediate/paratenic host of some helminthes, whose final hosts are whales, seals, large rays and sharks. This article presents new data on toothfish infection in the Pacific sector of the Antarctic. Specimens were examined during commercial longline fishing in the Ross Sea and the Amundsen Sea in January–February 2013. Fourteen species of parasites were found using standard parasitological methods and genetic analysis.Keywords: Toothfish; parasites; Antarctic fisheries; CCAMLR; infection; Southern Ocean.(Published: 24 June 2016)Citation: Polar Research 2016, 35, 29364, http://dx.doi.org/10.3402/polar.v35.2936
Freshwater ostracods (Crustacea) and environmental variability of polygon ponds in the tundra of the Indigirka Lowland, north-east Siberia
No full textFreshwater ostracods (Crustacea, Ostracoda) are valuable biological indicators. In Arctic environments, their habitat conditions are barely known and the abundance and diversity of ostracods is documented only in scattered records with incomplete ecological characterization. To determine the taxonomic range of ostracod assemblages and their habitat conditions in polygon ponds in the Indigirka Lowland, north-east Siberia, we collected more than 100 living ostracod individuals per site with a plankton net (mesh size 65 µm) and an exhaustor system from 27 water bodies and studied them in the context of substrate and hydrochemical data. During the summer of 2011, a single pond site and its ostracod population was selected for special study. This first record of the ostracod fauna in the Indigirka Lowland comprises eight species and three additional taxa. Fabaeformiscandona krochini and F. groenlandica were documented for the first time in continental Siberia. Repeated sampling of a low-centre polygon pond yielded insights into the population dynamics of F. pedata. We identified air temperature and precipitation as the main external drivers of water temperatures, water levels, ion concentrations and water stable isotope composition on diurnal and seasonal scales.Keywords: Arctic limnology; permafrost; patterned ground; ecological indication; freshwater ostracods.(Published: 1 March 2016)To access the supplementary material for this article, please see the supplementary files in the column to the right (under Article Tools).Citation: Polar Research 2016, 35, 25225, http://dx.doi.org/10.3402/polar.v35.2522
Local controls on sediment accumulation and distribution in a fjord in the West Antarctic Peninsula: implications for palaeoenvironmental interpretations
No full textWe analyse surface sediment and its distribution in Flandres Bay, West Antarctic Peninsula, in order to understand modern day sediment dispersal patterns in a fjord with retreating, tidewater glaciers. The surface sediment descriptions of 41 cores are included in this study. The sediment facies described include muddy diatomaceous ooze, diatomaceous mud, pebbly mud, sandy mud and mud, with scattered pebbles present in most samples. In contrast to a traditional conceptual model of glacial sediment distribution in fjords, grain size in Flandres Bay generally coarsens from the inner to outer bay. The smallest grain size sediments were found in the bay head and are interpreted as fine-grained deposits resulting from meltwater plumes and sediment gravity flows occurring close to the glacier front. The middle of the bay is characterized by a high silt percentage, which correlates to diatom-rich sediments. Sediments in the outer bay have a high component of coarse material, which is interpreted as being the result of winnowing from currents moving from the Bellingshausen Sea into the Gerlache Strait. Palaeoenvironmental reconstructions of glacial environments often use grain size as an indicator of proximity to the ice margin. After a detailed analysis of a large number of cores collected in the study area, our findings highlight the variability in sedimentation patterns within a fjord and provide a valuable evidence of the complexity that may occur in the sedimentary record.Keywords: Flandres Bay; Antarctic Peninsula; sediment distribution; grain size.(Published: 12 August 2016)To access the supplementary material for this article, please see the supplementary files in the column to the right (under Article Tools).Citation: Polar Research 2016, 35, 25284, http://dx.doi.org/10.3402/polar.v35.2528
Icelandic volcanic dust can have a significant influence on the cryosphere in Greenland and elsewhere
No full textNo abstract available.(Published: 24 July 2016)Citation: Polar Research 2016, 35, 31313,http://dx.doi.org/10.3402/polar.v35.313
Transpression and tectonic exhumation in the Heimefrontfjella, western orogenic front of the East African/Antarctic Orogen, revealed by quartz textures of high strain domains
No full textThe metamorphic basement of the Heimefrontfjella in western Dronning Maud Land (Antarctica) forms the western margin of the major ca. 500 million year old East African/East Antarctic Orogen that resulted from the collision of East Antarctica and greater India with the African cratons. The boundary between the tectonothermally overprinted part of the orogen and its north-western foreland is marked by the subvertical Heimefront Shear Zone. North-west of the Heimefront Shear Zone, numerous low-angle dipping ductile thrust zones cut through the Mesoproterozoic basement. Petrographic studies, optical quartz c-axis analyses and x-ray texture goniometry of quartz-rich mylonites were used to reveal the conditions that prevailed during the deformation. Mineral assemblages in thrust mylonites show that they were formed under greenschist-facies conditions. Quartz microstructures are characteristic of the subgrain rotation regime and oblique quartz lattice preferred orientations are typical of simple shear-dominated deformation. In contrast, in the Heimefront Shear Zone, quartz textures indicate mainly flattening strain with a minor dextral rotational component. These quartz microstructures and lattice preferred orientations show signs of post-tectonic annealing following the tectonic exhumation. The spatial relation between the sub-vertical Heimefront Shear Zone and the low-angle thrusts can be explained as being the result of strain partitioning during transpressive deformation. The pure-shear component with a weak dextral strike-slip was accommodated by the Heimefront Shear Zone, whereas the north–north-west directed thrusts accommodate the simple shear component with a tectonic transport towards the foreland of the orogen.Keywords: Dronning Maud Land; quartz microfabrics; X-ray texture goniometry; shear zones; mylonites.(Published: 15 June 2016)To access the supplementary material for this article, please see the supplementary file under Article Tools, online.Citation: Polar Research 2016, 35, 25420, http://dx.doi.org/10.3402/polar.v35.2542
Characterization of sea-ice kinematic in the Arctic outflow region using buoy data
No full textData from four ice-tethered buoys deployed in 2010 were used to investigate sea-ice motion and deformation from the Central Arctic to Fram Strait. Seasonal and long-term changes in ice kinematics of the Arctic outflow region were further quantified using 42 ice-tethered buoys deployed between 1979 and 2011. Our results confirmed that the dynamic setting of the transpolar drift stream (TDS) and Fram Strait shaped the motion of the sea ice. Ice drift was closely aligned with surface winds, except during quiescent conditions, or during short-term reversal of the wind direction opposing the TDS. Meridional ice velocity south of 85°N showed a distinct seasonal cycle, peaking between late autumn and early spring in agreement with the seasonality of surface winds. Inertia-induced ice motion was strengthened as ice concentration decreased in summer. As ice drifted southward into the Fram Strait, the meridional ice speed increased dramatically, while associated zonal ice convergence dominated the ice-field deformation. The Arctic atmospheric Dipole Anomaly (DA) influenced ice drift by accelerating the meridional ice velocity. Ice trajectories exhibited less meandering during the positive phase of DA and vice versa. From 2005 onwards, the buoy data exhibit high Arctic sea-ice outflow rates, closely related to persistent positive DA anomaly. However, the long-term data from 1979 to 2011 do not show any statistically significant trend for sea-ice outflow, but exhibit high year-to-year variability, associated with the change in the polarity of DA.Keywords: Sea ice; kinematics; dipole anomaly; transpolar drift stream; Arctic Ocean; Fram Strait.(Published: 27 January 2016)Citation: Polar Research 2016, 35, 22658,http://dx.doi.org/10.3402/polar.v35.2265