Polar Research (E-Journal)
Not a member yet
1388 research outputs found
Sort by
Permafrost dynamics structure species compositions of oribatid mite (Acari: Oribatida) communities in sub-Arctic palsa mires
No full textPalsa mires are sub-Arctic peatland complexes, vulnerable ecosystems with patches of permafrost. Permafrost thawing in palsa mires occurs throughout Fennoscandia, probably due to local climatic warming. In palsa mires, permafrost thaw alters hydrological conditions, vegetation structure and microhabitat composition with unknown consequences for invertebrate fauna. This study's objectives were to examine the role of microhabitat heterogeneity and the effects of permafrost dynamics and thaw on oribatid mite communities in palsa mires. Oribatid mites were sampled in two palsa mires in Finland and Norway. Three different types of microhabitats were examined: graminoid-dominated wet sites, herb-dominated small hummocks and evergreen shrub-dominated permafrost-underlain palsa hummocks. The results indicate that permafrost dynamics are an important factor structuring oribatid mite communities in palsa mires. The community composition of oribatid mites differed remarkably among microhabitats. Six species were significantly more abundant in permafrost-underlain microhabitats in relation to non-permafrost microhabitats. None of the species identified occurred exclusively in permafrost-underlain microhabitats. Findings suggest that permafrost thaw may not have an impact on species diversity but may alter community composition of oribatid mites in palsa mire ecosystems.Keywords: Biodiversity; community composition; habitat heterogeneity; oribatid mites; palsa mires; permafrost dynamics.(Published: 14 October 2014)Citation: Polar Research 2014, 33, 22926, http://dx.doi.org/10.3402/polar.v33.2292
Turbulent fluxes of momentum and heat over land in the High- Arctic summer: the influence of observation techniques
No full textDifferent observation techniques for atmospheric turbulent fluxes of momentum and sensible heat were tested in a High-Arctic valley in Svalbard during two consecutive summers (June–August in 2010 and 2011). The gradient method (GM) and the bulk method (BM) have been compared to the more direct eddy covariance method (ECM) in order to evaluate if relatively robust and cheap instrumentation with low power consumption can be used as a means to increase the number of observations, especially at remote locations where instruments need to be left unattended for extended periods. Such campaigns increase knowledge about the snow-free surface exchange processes, an area which is relatively little investigated compared to snow-covered ground. The GM agreed closely to the ECM, especially for momentum flux where the two methods agree within 5%. For sensible heat flux, the GM produces, on average, approximately 40% lower values for unstable stratification and 67% lower for stable stratification. However, this corresponds to only 20 and 12 W m−2, respectively. The BM, however, shows a greater scatter and larger differences for both parameters. In addition to testing these methods, radiation properties were measured and the surface albedo was found to increase through the summer, from approximately 0.1 to 0.2. The surface energy budget shows that the sensible heat flux is usually directed upwards for the whole summer, while the latent heat flux is upwards in June, but becomes downward in July and August.Keywords: Turbulent fluxes; Svalbard; Arctic; observation techniques; surface energy budget.(Published: 30 June 2014)Citation: Polar Research 2014, 33, 21567, http://dx.doi.org/10.3402/polar.v33.2156
Stratigraphy of the uppermost Old Red Sandstone of Svalbard (Mimerdalen Subgroup)
No full textBetween the fjords Dicksonfjorden and Billefjorden in central Spitsbergen, Svalbard’s youngest deposits (Early Givetian to Famennian in age) of the Old Red Sandstone—the Mimerdalen Subgroup—are exposed. They form a narrow outcrop area parallel to the Billefjorden Fault Zone and overlie unconformably the multicoloured sandstones of the Lower Devonian Wood Bay Formation. Stratigraphic rank and subdivision of the succession were changed repeatedly since its first mention in 1910. Based on student work in 1996, as well as regional mapping by the authors in 1993 and 2003, the present work formalizes the stratigraphic framework of the succession. This framework has already been applied in recent geological maps. At the same time it is a continuation of the lithostratigraphic standardization carried out by the Committee on the Stratigraphy of Svalbard (1999), where only post-Devonian rocks were considered. Except for some small-pebble conglomerate layers in the Wood Bay Formation, the upper part of the Mimerdalen Subgroup contains the first coarse-grained deposits in Svalbard’s Old Red since the lowermost Devonian Red Bay Group. Faulting between its formations as well as conglomerate pebbles derived from the Lower Devonian Wood Bay Formation indicate the onset of the Svalbardian Event after the tectonic stability during the deposition of the Wood Bay Formation. The Mimerdalen Subgroup is probably the detrital fill of a small foreland basin derived from erosion during the uplift of the Ny-Friesland Block to the east of the Billefjorden Fault Zone. It was later affected by compressional tectonic movements during the Svalbardian Event.Keywords: Svalbard; geology; stratigraphy; Mimerdalen Subgroup; Devonian; Old Red.To access the supplementary material for this article, please see supplementary files under Article Tools online.(Published: 30 October 2014)Citation: Polar Research 2014, 33, 19998, http://dx.doi.org/10.3402/polar.v33.1999
Trochammina as opportunist foraminifera in the Lower Jurassic from north Siberia
No full textThe ecostratigraphic analysis of foraminiferal assemblages from Upper Pliensbachian to Lower Toarcian (Lower Jurassic) mudstones, siltstones and black shales from northern Siberia allows for a better understanding of the response to the benthic biotic crisis related to the Toarcian Oceanic Anoxic Event in a high latitude context. The assemblages were dominated by agglutinated taxa with extremely low diversity values and dominance of Trochammina. These features suggest that the foraminiferal assemblages were adapted to restricted conditions, where the main limiting factors were salinity and oxygen degree. The opportunist behaviour of Trochammina enabled this genus to survive and adapt to unfavourable conditions. Trochammina proliferated in relation to the sea-level fall and probable changes in salinity in the Arctic palaeobasin during the Margaritatus Chron and at the beginning of the Viligaensis Chron (Late Pliensbachian). Another Trochammina proliferation is associated with the initial development of the restricted oxygen conditions related to the Toarcian Oceanic Anoxic Event.Keywords: r-strategists; colonization; anoxic event; ecostratigraphy; black shale.(Published: 2 July 2014)Citation: Polar Research 2014, 33, 21653, http://dx.doi.org/10.3402/polar.v33.2165
Atmospheric trace elements in aerosols observed over the Southern Ocean and coastal East Antarctica
No full textAtmospheric aerosol samples were collected over the Southern Ocean (SO) and coastal East Antarctica (CEA) during the austral summer of 2010/11. Samples were analysed for trace elements, including Na, Mg, K, Al, Fe, Mn, Ni, Cd and Se, by inductively coupled plasma mass spectrometry (ICP-MS). The mean atmospheric concentrations over the SO were 1100 ng m−3 for Na, 190 ng m−3 for Mg, 150 ng m−3 for Al, 14 ng m−3 for Fe, 0.46 ng m−3 for Mn and 0.25 ng m−3 for Se. Over CEA, the mean concentrations were 990 ng m−3 for Na, 180 ng m−3 for Mg, 190 ng m−3 for Al, 26 ng m−3 for Fe, 0.70 ng m−3 for Mn and 0.29 ng m−3 for Se. Particle size distributions, enrichment factors (EFs) and correlation analysis indicate that Na, Mg and K mainly came from the marine source, while Al, Fe and Mn were mainly from the crustal source, which also contributed to Mg and K over CEA. High EFs were associated with Ni, Cd and Se, suggesting likely contributions from mixed sources from the Antarctic continent, long-range transport, marine biogenic emissions and anthropogenic emissions. Sea-salt elements (Na, Mg, K) were mainly accumulated in the coarse mode, and crustal elements (Al, Fe, Mn) presented a bimodal size distribution pattern. Bioactive elements (Fe, Ni, Cd) were enriched in the fine mode, especially with samples collected over the SO, possibly affecting biogeochemical cycles in this oceanic region.Keywords: Southern Ocean; coastal East Antarctica; trace elements; size distribution; sources(Published: 17 November 2014)Citation: Polar Research 2014, 33, 23973, http://dx.doi.org/10.3402/polar.v33.2397
Verification of a new NOAA/NSIDC passive microwave sea-ice concentration climate record
No full textA new satellite-based passive microwave sea-ice concentration product developed for the National Oceanic and Atmospheric Administration (NOAA) Climate Data Record (CDR) programme is evaluated via comparison with other passive microwave-derived estimates. The new product leverages two well-established concentration algorithms, known as the NASA Team and Bootstrap, both developed at and produced by the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC). The sea-ice estimates compare well with similar GSFC products while also fulfilling all NOAA CDR initial operation capability (IOC) requirements, including (1) self-describing file format, (2) ISO 19115-2 compliant collection-level metadata, (3) Climate and Forecast (CF) compliant file-level metadata, (4) grid-cell level metadata (data quality fields), (5) fully automated and reproducible processing and (6) open online access to full documentation with version control, including source code and an algorithm theoretical basic document. The primary limitations of the GSFC products are lack of metadata and use of untracked manual corrections to the output fields. Smaller differences occur from minor variations in processing methods by the National Snow and Ice Data Center (for the CDR fields) and NASA (for the GSFC fields). The CDR concentrations do have some differences from the constituent GSFC concentrations, but trends and variability are not substantially different.Keywords: Sea ice; Arctic and Antarctic oceans; climate data record; evaluation; passive microwave remote sensing.(Published: 22 December 2014)Citation: Polar Research 2014, 33, 21004, http://dx.doi.org/10.3402/polar.v33.2100
Review of Botanical excursions on the northern Sørøya (Finnmark, Norway), edited by N. Koroleva, E. Borovichev, A. Melekhin and Tom E. Ness
No full textNo abstract available!
(Published: 10 October 2014)
Citation: Polar Research 2014, 33, 26018, http://dx.doi.org/10.3402/polar.v33.2601
Review of Polar bears: a complete guide to their biology and behavior, by Andrew Derocher
No full textTwo of the world’s leading polar bear scientists have recently released books on their favourite species aimed at the general public. In 2011, Ian Stirling published his second popular book on polar bears, Polar bears: the natural history of a threatened species, a classic-to-be for a general readership and a skilful update on the latest in polar bear science. The following year his former student, Andrew Derocher, came out with his book in the same genre, a volume that sums up three decades of research.
(Published: 19 February 2014)
Citation: Polar Research 2014, 33, 23867, http://dx.doi.org/10.3402/polar.v33.2386
Contrasting strategies of resistance vs. tolerance to desiccation in two polar dipterans
No full textLow water availability is one of the principal stressors for terrestrial invertebrates in the polar regions, determining the survival of individuals, the success of species and the composition of communities. The Arctic and Antarctic dipterans Heleomyza borealis and Eretmoptera murphyi spend the majority of their biennial life cycles as larvae, and so are exposed to the full range of environmental conditions, including low water availability, over the annual cycle. In the current study, the desiccation resistance and desiccation tolerance of larvae were investigated, as well as their capacity for cross-tolerance to temperature stress. Larvae of H. borealis showed high levels of desiccation resistance, only losing 6.9% of their body water after 12 days at 98.2% relative humidity (RH). In contrast, larvae of E. murphyi lost 46.7% of their body water after 12 days at the same RH. Survival of E. murphyi larvae remained high in spite of this loss (>80% survival). Following exposure to 98.2% RH, larvae of E. murphyi showed enhanced survival at −18°C for 2 h. The supercooling point of larvae of both species was also lowered following prior treatment at 98.2% RH. Cross-tolerance to high temperatures (37 or 38.5°C) was not noted following desiccation in E. murphyi, and survival even fell at 37°C following a 12-day pre-treatment. The current study demonstrates two different strategies of responding to low water availability in the polar regions and indicates the potential for cross-tolerance, a capacity which is likely to be beneficial in the ever-changing polar climate.Keywords: Acclimation; dipteran; supercooling point; temperature; cross-tolerance.(Published: 22 May 2014)Citation: Polar Research 2014, 33, 22963, http://dx.doi.org/10.3402/polar.v33.2296
Deterrent activities in the crude lipophilic fractions of Antarctic benthic organisms: chemical defences against keystone predators
No full textGeneralist predation constitutes a driving force for the evolution of chemical defences. In the Antarctic benthos, asteroids and omnivore amphipods are keystone opportunistic predators. Sessile organisms are therefore expected to develop defensive mechanisms mainly against such consumers. However, the different habits characterizing each predator may promote variable responses in prey. Feeding-deterrence experiments were performed with the circumpolar asteroid macropredator Odontaster validus to evaluate the presence of defences within the apolar lipophilic fraction of Antarctic invertebrates and macroalgae. A total of 51% of the extracts were repellent, yielding a proportion of 17 defended species out of the 31 assessed. These results are compared with a previous study in which the same fractions were offered to the abundant circum-Antarctic amphipod Cheirimedon femoratus. Overall, less deterrence was reported towards asteroids (51%) than against amphipods (80.8%), principally in sponge and algal extracts. Generalist amphipods, which establish casual host–prey sedentary associations with biosubstrata (preferentially sponges and macroalgae), may exert more localized predation pressure than sea stars on certain sessile prey, which would partly explain these results. The nutritional quality of prey may interact with feeding deterrents, whose production is presumed to be metabolically expensive. Although optimal defence theory posits that chemical defences are managed and distributed as to guarantee protection at the lowest cost, we found that only a few organisms localized feeding deterrents towards most exposed and/or valuable body regions. Lipophilic defensive metabolites are broadly produced in Antarctic communities to deter opportunistic predators, although several species combine different defensive traits.Keywords: Antarctic invertebrates; Antarctic algae; chemical ecology; sea star Odontaster validus; amphipod Cheirimedon femoratus; chemical defence.(Published: 7 April 2014)Citation: Polar Research 2014, 33, 21624, http://dx.doi.org/10.3402/polar.v33.2162