Search results for "Arctic"
showing 10 items of 565 documents
Sea ice extent and seasonality for the Early Pliocene northern Weddell Sea
2010
Abstract Growth increment analysis coupled with stable isotopic data ( δ 18 O/ δ 13 C) from Early Pliocene (ca 4.7 Ma) Austrochlamys anderssoni from shallow marine sediments of the Cockburn Island Formation, northern Antarctic Peninsula, suggest these bivalves grew through much of the year, even during the coldest parts of winter recorded in the shells. The high frequency fluctuation in growth increment width of A. anderssoni appears to reflect periodic, but year-round, agitation of the water column enhancing benthic food supply from organic detritus. This suggests that Austrochlamys favoured waters that were largely sea ice free. Our data support interpretation of the Cockburn Island Forma…
South Pole glacial climate reconstruction from multi-borehole laser particulate stratigraphy
2013
AbstractThe IceCube Neutrino Observatory and its prototype, AMANDA, were built in South Pole ice, using powerful hot-water drills to cleanly bore>100 holes to depths up to 2500 m. The construction of these particle physics detectors provided a unique opportunity to examine the deep ice sheet using a variety of novel techniques. We made high-resolution particulate profiles with a laser dust logger in eight of the boreholes during detector commissioning between 2004 and 2010. The South Pole laser logs are among the most clearly resolved measurements of Antarctic dust strata during the last glacial period and can be used to reconstruct paleoclimate records in exceptional detail. Here we use…
Growth of nucleation mode particles in the summertime Arctic: a case study
2016
Abstract. The summertime Arctic lower troposphere is a relatively pristine background aerosol environment dominated by nucleation and Aitken mode particles. Understanding the mechanisms that control the formation and growth of aerosol is crucial for our ability to predict cloud properties and therefore radiative balance and climate. We present an analysis of an aerosol growth event observed in the Canadian Arctic Archipelago during summer as part of the NETCARE project. Under stable and clean atmospheric conditions, with low inversion heights, carbon monoxide less than 80 ppbv, and black carbon less than 5 ng m−3, we observe growth of small particles, < 20 nm in diameter, into sizes ab…
Dietary plasticity of Arctic charr (Salvelinus alpinus) facilitates coexistence with competitively superior European whitefish (Coregonus lavaretus)
2011
– Habitat use and diet of Arctic charr (Salvelinus alpinus) coexisting with European whitefish (Coregonus lavaretus) and grayling (Thymallus thymallus) were studied in one deep and two relatively shallow subarctic lakes in northern Norway. Stomach content and stable isotope analyses revealed clear and temporally stable resource partitioning between the species in all three lakes. Arctic charr had a wide and flexible trophic niche and was the only piscivorous species. In contrast, whitefish and grayling had remarkably stable planktivorous and benthivorous niches, respectively. In the deepest lake, Arctic charr together with grayling mainly utilised littoral benthos, while piscivory was more…
Global phylogeography and geographical variation in warning coloration of the wood tiger moth (Parasemia plantaginis)
2015
Aim To investigate the phylogeography of the aposematic wood tiger moth (Parasemia plantaginis) across its Holarctic distribution and to explore how its genetic structure relates to geographical differences in hindwing warning coloration of males and females. Males have polymorphic hindwing coloration, while female hindwing coloration varies continuously, but no geographical analyses of coloration or genetic structure exist. Location The Holarctic. Methods We sequenced a fragment of the mitochondrial cytochrome c oxidase subunit I gene (COI) from 587 specimens. We also examined more current population structure by genotyping 569 specimens at 10 nuclear microsatellite loci. Species distribut…
A Revision of the Nearctic Species of Hecamedoides Hendel (Diptera: Ephydridae)
2008
Abstract Species of the shore-fly genus Hecamedoides Hendel from the Nearctic Region are revised, including description of H. lattini, new species (Virginia. Stafford: Falmouth (38°19.2′N, 77°28.1′W; Rappahannock River; 9 m). To provide context and also to facilitate identification, diagnoses are provided for the tribe Discocerinini and genus in addition to a key to the genera and species, H. lattini and H. unispinosus, occurring in the New World. Diagnostic characters, especially of the male terminalia, are illustrated, and distribution maps are also provided.
Temperature-related changes in polar cyanobacterial mat diversity and toxin production
2012
This study documents the effects of warming on cyanobacterial mats from the Arctic and Antarctica. It describes toxin production in such mats and provides experimental evidence that increased temperatures could shift mat cyanobacterial species diversity from cold-loving species towards predominance of cold-tolerant and toxin-producing species.
Island Geographies of Separation and Cohesion: The Coronavirus (COVID-19) Pandemic and the Geopolitics of Kalaallit Nunaat (Greenland).
2020
Abstract Kalaallit Nunaat (Greenland) is an Arctic highly autonomous subnational island jurisdiction (SNIJ) of Denmark, its former coloniser. The coronavirus (COVID‐19) pandemic of 2020 has influenced both Kalaallit Nunaat’s relations with the outside world and relations between people and places within the territory. The Kalaallit Nunaat government’s response to the pandemic, including both internal and external travel bans and restrictions on movement, has focused on eradicating the disease from the territory. This strategy, however, is challenged both by the SNIJ’s economic reliance on Denmark and by the Danish government’s own strategy of mitigating the disease. This paper explores the …
Solar UV-B radiation affects leaf quality and insect herbivory in the southern beech tree Nothofagus antarctica
2004
We examined the effects of solar ultraviolet-B (UV-B) radiation on plant-insect interactions in Tierra del Fuego (55°S), Argentina, an area strongly affected by ozone depletion because of its proximity to Antarctica. Solar UV-B under Nothofagus antarctica branches was manipulated using a polyester plastic film to attenuate UV-B (uvb-) and an Aclar film to provide near-ambient UV-B (uvb+). The plastic films were placed on both north-facing (i.e., high solar radiation in the Southern Hemisphere) and south-facing branches. Insects consumed 40% less leaf area from north- than from south-facing branches, and at least 30% less area from uvb+ branches than from uvb-branches. The reduced herbivory …
Individual and combined effects of disturbance and N addition on understorey vegetation in a subarctic mountain birch forest
2011
Questions: What are the effects of repeated disturbance and N-fertilization on plant community structure in a mountain birch forest? What is the role of enhanced nutrient availability in recovery of understorey vegetation after repeated disturbance? How are responses of soil micro-organisms to disturbance and N-fertilization reflected in nutrient allocation patterns and recovery of understorey vegetation after disturbance? Location: Subarctic mountain birch forest, Finland. Methods: We conducted a fully factorial experiment with annual treatments of disturbance (two levels) and N-fertilization (four levels) during 1998‐2002. We monitored treatment effects on above-ground plant biomass, plan…