Polar Research (E-Journal)
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Middle to late Quaternary grain size variations and sea-ice rafting on the Lomonosov Ridge
No full textSea ice and icebergs are the dominant transport agents for sand-sized material to the central Arctic Ocean. However, few studies have investigated concurrent changes in the silt-sized fraction of Arctic sediments. Here we present an analysis of the coarse fraction content and silt grain size composition from middle and late Quaternary sediments recovered from the Lomonosov Ridge, in the central Arctic Ocean. A significant shift in the grain size record occurs at the marine isotope stage (MIS) 6/7 boundary, where larger amplitude variability in the sand fraction is seen in glacial and stadial periods. Below the MIS6/7 boundary, variations in the coarse fraction content are less pronounced, but prominent changes in the silt size fraction appear to define glacial and interglacial periods. Throughout the record, the percent weight of sortable silt in the fine fraction (SS % wtfines), sortable silt mean size, and coarse silt content all increase as the >63 µm % wt content increases. This is consistent with observations of grain size spectra obtained from modern sea-ice samples, and indicates a strong overprint from sea ice on the silt distribution. The mechanism by which this sea-ice signal is preserved in the sediments across glacial and interglacial periods remains unclear. We suggest that the coarsening of silt-sized material during glacial periods could be attributed to either the entrainment of larger size fractions during suspension/anchor ice formation when sea levels are lowered, or diminished input and advection of fine fraction material during glacial periods.Keywords: Pleistocene; Lomonosov Ridge; grain size; sea ice.(Published: 26 June 2014)Citation: Polar Research 2014, 33, 23672, http://dx.doi.org/10.3402/polar.v33.2367
Late Holocene climate change recorded in proxy records from a Bransfield Basin sediment core, Antarctic Peninsula
No full textThe glacimarine environment of the Antarctic Peninsula region is one of the fastest warming places on Earth today, but details of changes in the recent past remain unknown. Large distances and widespread variability separate late Holocene palaeoclimate reconstructions in this region. This study focuses on a marine sediment core collected from ca. 2000 m below sea level in the Central Bransfield Strait that serves as a key for understanding changes in this region. The core yielded a high sedimentation rate and therefore provides an exceptional high-resolution sedimentary record composed of hemipelagic sediment, with some turbidites. An age model has been created using radiocarbon dates that span the Late Holocene: 3560 cal yr BP to present. This chronostratigraphic framework was used to establish five units, which are grouped into two super-units: a lower super-unit (3560–1600 cal yr BP) and an upper super-unit (1600 cal yr BP–present), based on facies descriptions, laser particle size analysis, x-ray analysis, multi-sensor core logger data, weight percentages and isotopic values of total organic carbon and nitrogen. We interpret the signal contained within the upper super-unit as an increase in surface water irradiance and/or shortening of the sea-ice season and the five units are broadly synchronous with climatic intervals across the Antarctic Peninsula region. While the general trends of regional climatic periods are represented in the Bransfield Basin core we have examined, each additional record that is obtained adds variability to the known history of the Antarctic Peninsula, rather than clarifying specific trends.
Keywords: Antarctic Peninsula; palaeoclimate; Holocene; marine; isotopes.
(Published: 11 June 2014)
Citation: Polar Research 2014, 33, 17236, http://dx.doi.org/10.3402/polar.v33.1723
Topography, ice thickness and ice volume of the glacier Pedersenbreen in Svalbard, using GPR and GPS
No full textPedersenbreen is a small valley glacier (ca. 6 km2 in 2009), ending on land, located in north-western Spitsbergen, Svalbard. Ground-based radio-echo sounding in April 2009, using a 100-MHz commercial radar and a self-made low-frequency radar, revealed a polythermal structure. The radar was coupled with a global positioning system device to geo-reference the traces. Each radar profile was manually edited to pick the reflection arrival time from the interface between ice and bedrock. Travel times were converted to ice thickness using a velocity of 0.165 m/ns, which was estimated from common mid-point measurement. Then the surface topography, bedrock topography, ice thickness contours and ice volume were derived using interpolation methods. Because it was difficult to distinguish the reflection wave from the background with the 100-MHz radar in some of the thickest areas of Pedersenbreen, we used a 5-MHz radar of our own design to fill in this gap. The maximum thickness of Pedersenbreen reaches 183±9 m, and the ice volume is 0.393±0.047 km3 in 2009. Comparing these data with the surface topographical data available for 1936 indicates a mass loss of nearly 12% during the past 73 years.Keywords: GPR; GPS; glacier topography; ice volume; ice thickness; Pedersenbreen(Published: 20 February 2014)Citation: Polar Research 2014, 33, 18533, http://dx.doi.org/10.3402/polar.v33.1853
Plant co-existence patterns and High-Arctic vegetation composition in three common plant communities in north-east Greenland
No full textArctic regions are expected to experience substantial changes in climate in the coming decades. In order to predict potential changes of Arctic vegetation, it is important to understand the distinct role of life forms of plants and of individual species in relation to plant co-existence patterns. Our aim is to investigate if three common Arctic plant patch types dominated by contrasting life forms (by the dwarf shrubs Salix arctica or Dryas octopetala×intermedia or by mosses) are related (a) to the co-existence of vascular plants and species richness at patch scale and (b) to the floristic composition in three distinct plant communities (Salix snowbed, Dryas heath and fell-field) associated with contrasting abiotic regimes. The study was conducted at Zackenberg, in north-east Greenland. Dryas patches showed a clear negative effect on small-scale plant richness and co-existence in the fell-field. Salix and moss patches showed a similar pattern in all the plant communities, although the number of individuals growing in Salix patches was lower than in moss patches. Salix and mosses in the fell-fields hosted a high number of species in spite of the much less vegetated aspect of this harsh, upper zone. The floristic composition varied between plant communities, but it did not change substantially between patch types within each community. This study provides novel background knowledge of plant co-existence patterns at patch scale and of the structure of contrasting Arctic plant communities, which will help to better assess the potential effects of varying abiotic stress regimes on Arctic vegetation.To access the supplementary material for this article, please see the supplementary files in the column to the right (under Article Tools).Keywords: Abiotic stress; Arctic vegetation; co-existence patterns; plant community; species richness.(Published: 25 September 2014)Citation: Polar Research 2014, 33, 19235, http://dx.doi.org/10.3402/polar.v33.1923
Alien invasions in Antarctica - is anyone liable?
No full textThe introduction of non-native species to Antarctica in association with human activities is a major threat to indigenous biodiversity and the region's unique ecosystems, as has been well-demonstrated in other ecosystems globally. Existing legislation contained in the Protocol on Environmental Protection to the Antarctic Treaty does not specifically make the eradication of non-native species mandatory, although it is implicit that human-assisted introductions should not take place. Furthermore, to date, eradications of non-native species in the Treaty area have been infrequent and slow to progress. In 2005 an additional Annex (VI) to the Protocol was agreed concerning “Liability arising from environmental emergencies.” This annex focusses on prevention of environmental emergencies, contingency planning and reclaiming costs incurred when responding to an environmental emergency caused by another operator within the Antarctic Treaty area. However, the types of environmental emergencies covered by the annex are not defined. In this paper we highlight potential difficulties with the application of Annex VI in the context of non-native species control and eradication, including, for example, whether a non-native species introduction would be classified as an “environmental emergency” and therefore be considered under the terms of the annex. Even if this were the case, we conclude that the slow pace of approval of the annex by Antarctic Treaty Parties may prevent it coming into force for many years and, once in force, in its current form it is unlikely to be useful for reclaiming costs associated with the eradication or management of a non-native species.Keywords: Liability Annex; non-native species; Environmental Protocol; Antarctic Treaty area; eradication; environmental emergency(Published: 12 May 2014)To access the supplementary material for this article, please see Supplementary files in the column to the right (under Article Tools).Citation: Polar Research 2014, 33, 22103, http://dx.doi.org/10.3402/polar.v33.2210
Palaeoenvironments and palaeoceanography changes across the Jurassic/Cretaceous boundary in the Arctic realm: case study of the Nordvik section (north Siberia, Russia)
No full textThe Jurassic/Cretaceous transition was accompanied by significant changes in palaeoceanography and palaeoenvironments in the Tethyan Realm, but outside the Tethys such data are very scarce. Here we present results of a study of the most complete section in the Panboreal Superrealm, the Nordvik section. Belemnite δ18O data show an irregular decrease from values reaching up to +1.6‰ in the Middle Oxfordian and from +0.8 to −1.7‰ in the basal Ryazanian, indicating a prolonged warming. The biodiversity changes were strongly related to sea-level oscillations, showing a relatively low belemnite and high ammonite diversity during sea-level rise, accompanied by a decrease of the macrobenthos taxonomical richness. The most prominent sea-level rise is marked by the occurrence of open sea ammonites with Pacific affinities. Peak abundances of spores and prasinophytes correlate with a negative excursion in organic carbon δ13C near the J/K boundary and could reflect blooms of green algae caused by disturbance of the marine ecosystem.Keywords: Biodiversity; stable isotopes; J/K boundary; Arctic Realm; palaeoceanography(Published: 25 March 2014)Citation: Polar Research 2014, 33, 19714, http://dx.doi.org/10.3402/polar.v33.1971
Complete breeding failures in ivory gull following unusual rainy storms in North Greenland
No full textNatural catastrophic events such as heavy rainfall and windstorms may induce drastic decreases in breeding success of animal populations. We report the impacts of summer rainfalls on the reproductive success of ivory gull (Pagophila eburnea) in north-east Greenland. On two occasions, at Amdrup Land in July 2009 and at Station Nord in July 2011, we observed massive ivory gull breeding failures following violent rainfall and windstorms that hit the colonies. In each colony, all of the breeding birds abandoned their eggs or chicks during the storm. Juvenile mortality was close to 100% at Amdrup Land in 2009 and 100% at Station Nord in 2011. Our results show that strong winds associated with heavy rain directly affected the reproductive success of some Arctic bird species. Such extreme weather events may become more common with climate change and represent a new potential factor affecting ivory gull breeding success in the High Arctic.Keywords: Pagophila eburnea; breeding failure; Greenland; endangered species; summer precipitation; climate change.(Published: 13 March 2014)Citation: Polar Research 2014, 33, 22749, http://dx.doi.org/10.3402/polar.v33.2274
Changes in the marine carbonate system of the western Arctic: patterns in a rescued data set
No full textA recently recovered and compiled set of inorganic carbon data collected in the Canadian Arctic since the 1970s has revealed substantial change, as well as variability, in the carbonate system of the Beaufort Sea and Canada Basin. Whereas the role of this area as a net atmospheric carbon sink has been confirmed, high pCO2 values in the upper halocline underscore the potential for CO2 outgassing as sea ice retreats and upwelling increases. In addition, increasing total inorganic carbon and decreasing alkalinity are increasing pCO2 and decreasing CaCO3 saturation states, such that undersaturation with respect to aragonite now occurs regularly in both deep waters and the upper halocline.Keywords: Carbonate system; Arctic Ocean; time series; Beaufort Sea; ocean acidification(Published: 26 November 2014)Citation: Polar Research 2014, 33, 20577, http://dx.doi.org/10.3402/polar.v33.2057
Ice volume changes (1936-1990-2007) and ground-penetrating radar studies of Ariebreen, Hornsund, Spitsbergen
No full textAriebreen is a small (0.37 km2)-valley glacier located in southern Spitsbergen. Our ground-penetrating radar surveys of the glacier show that it is less than 30 m thick on average, with a maximum thickness of 82 m, and it appears to be entirely cold. By analysing digital terrain models of the ice surface from different dates, we determine the area and volume changes during two periods, 1936-1990 and 1990-2007. The total ice volume of the glacier has decreased by 73% during the entire period 1936-2007, which is equivalent to a mean mass balance rate of -0.61±0.17 m y-1 w.eq. The glacier thinning rate has increased markedly between the first and second periods, from -0.50±0.22 to -0.95±0.17 m y-1 w.eq.Keywords: Ice-volume changes; ground-penetrating radar; thinning rate; Ariebreen; Spitsbergen; Svalbard(Published: 1 August 2013)To access the supplementary material for this article, please see Supplementary files in the column to the right (under Article Tools)Citation: Polar Research 2013, 32, 11068, http://dx.doi.org/10.3402/polar.v32i0.1106
Biogenic and detrital-rich intervals in central Arctic Ocean cores identified using x-ray fluorescence scanning
No full textX-ray fluorescence (XRF) scanning of sediment cores from the Lomonosov Ridge and the Morris Jesup Rise reveals a distinct pattern of Ca intensity peaks through Marine Isotope Stages (MIS) 1 to 7. Downcore of MIS 7, the Ca signal is more irregular and near the detection limit. Virtually all major peaks in Ca coincide with a high abundance of calcareous microfossils; this is particularly conspicuous in the cores from the central Arctic Ocean. However, the recorded Ca signal is generally caused by a combination of biogenic and detrital carbonate, and in areas influenced by input from the Canadian Arctic, detrital carbonates may effectively mask the foraminiferal carbonates. Despite this, there is a strong correlation between XRF-detected Ca content and foraminiferal abundance. We propose that in the Arctic Ocean north of Greenland a common palaeoceanographic mechanism is controlling Ca-rich ice-rafted debris (IRD) and foraminiferal abundance. Previous studies have shown that glacial periods are characterized by foraminfer-barren sediments. This implies that the Ca-rich IRD intervals with abundant foraminifera were most likely deposited during interglacial periods when glaciers left in the Canadian Arctic Archipelago were still active and delivered a large amount of icebergs. At the same time, conditions were favourable for planktic foraminifera, resulting in a strong covariance between these proxies. Therefore, we suggest that the XRF scanner’s capability to efficiently map Ca concentrations in sediment cores makes it possible to systematically examine large numbers of cores from different regions to investigate the palaeoceanographic reasons for the calcareous microfossils’ spatial and temporal variability.Keywords: Foraminifera; Arctic Ocean; IRD; calcareous microfossils; XRF scanning(Published: 7 February 2013)Citation: Polar Research 2013, 32, 18386, http://dx.doi.org/10.3402/polar.v32i0.1838