North-West Barents Sea Research Articles

Living and dead foraminiferal assemblages of the last decades from Kveithola Trough: Taphonomic processes and ecological highlights

We examine the living and dead benthic foraminiferal assemblages from the topmost 10 cm (using 150 μm sieve fraction) of three sedimentological short records collected in the Kveithola Trough (northwest Barents Sea). Our aim is to reconstruct the environmental variations of the last decades, connected to the interaction among the North Atlantic and the Arctic water masses. Our samples are collected at water depths between 150 and 380 m during the Eurofleets2-BURSTER oceanographic cruise, on board of the R/V Polarstern (June 2016).In the Cell Tracker Green (CTG) labelled living foraminiferal fauna, the main species are Pullenia bulloides, Globobulimina auriculata, and Nonionellina labradorica, while in the dead assemblages the main species are Cassidulina neoteretis, Cibicidoides lobatulus, and Cassidulina reniforme (outer, inner, and shelf stations, respectively). The dead foraminiferal assemblages show no significant traceable environmental changes in the Kveithola Trough area occurred during the last ca. 100 years. Conversely, the living foraminiferal fauna shows that this area is subject to variations related to circulation changes and organic matter burial in sediments, to which the biota adapts quickly. Moreover, the species that are only observed in the dead foraminiferal assemblages and not in the living CTG-labelled foraminiferal assemblages (e.g. C. reniforme) are typical of colder water and highlight the ongoing warming of the Arctic area. We find that the preservation of foraminiferal tests may bias the paleontological results. The agglutinated tests are often disintegrated, and the delicate calcareous ones are broken. The environmental conditions (style of sedimentation, bottom currents, interaction with other communities) can weaken the foraminiferal tests and make them prone to breakage or dissolution.

Paleo Cruise 2018

The Nansen Legacy paleo cruise was carried out from September 26 to October 20, 2018 with RV “Kronprins Haakon”. The cruise took place in the northern Barents Sea and the Nansen Basin, and it went through the sea ice to 83.3 N. The overriding objective of the cruise was to reconstruct the natural variability and range of sea ice cover and Atlantic Water through flow in the Barents Sea on longer time scales. During the cruise four ocean moorings were deployed in northwest Barents Sea, where one ARGO float was also deployed. Twelve “paleo stations” were identified using multibeam and sub bottom profilers. At these stations, short and long sediment cores were obtained. This cruise report gives an overview of methods used and samples taken.

Wave-ice interaction in the North-West Barents Sea

The results of field work on drift ice during wave propagation are analyzed and presented. The field work was performed in the Barents Sea, and the main focus of the paper is on wave processes in the MIZ. A model of wave damping in broken ice is formulated and applied to interpret the field work results. It is confirmed that waves of higher frequencies are subjected to stronger damping when they propagate below the ice. This reduces the frequency of most energetic wave with increasing distance from the ice edge. Difference of wave spectra measured in two relatively close locations within the MIZ is discussed. The complicated geometry and dynamics of the MIZ in the North-West Barents Sea allow waves from the Atlantic Ocean and south regions of the Barents Sea to penetrate into different locations of the MIZ.

Full-scale flexural strength of sea ice and freshwater ice in Spitsbergen Fjords and North-West Barents Sea

The present paper describes the results of a rather long series of full–scale, flexural–strength tests on ice beams (over 70 tests) performed in–situ in seawater and freshwater ice at and near Svalbard archipelago during the period 2010–2018. Ice thickness varied in the range of 0.2–0.8 m. Based on a comprehensive analysis of the test data, characteristic plots of ice flexural strength and effective elastic modulus versus the liquid–brine–volume fraction, which varied over a large range of 0–0.2 and were obtained specifically for the geographic region under consideration. The observed range in flexural strength for seawater ice was 0.109–0.415 MPa, and the same for freshwater ice was 0.275–0.807 MPa. The test results with cantilever beams did not show a dependence of the ice flexural strength on the direction of bending force applied to the free end of a beam. Experiments complemented with numerical analysis have demonstrated that stress concentrations in root sections of cantilever ice beams have significant impact on the accuracy of measurement of flexural strength of freshwater ice. It is noted that modifications have to be introduced in the methodology that is used to measure the effective elastic modulus of ice based on the free–end deflection of cantilever ice beams.

Modeling of iceberg drift in the marginal ice zone of the Barents Sea

The paper is focused on the analysis of the drift of tabular iceberg observed in 2009 in the marginal ice zone of the North-West Barents Sea. Momentum balance equations are derived from the Kirchhoff equations describing plane motion of solid body in an ideal fluid. Field works performed on the drift iceberg and on the drift icenear the iceberg are described. Results of the field works and numerical simulations of the iceberg drift and rotation are performed and discussed. It is shown that acceleration of water flow around the iceberg has visible influence on the iceberg drift. Kinetic energy balance of drift iceberg is used to estimate the forces applied to the iceberg by the drift ice.

Late Cenozoic lithosphere dynamics in Svalbard: Interplay of glaciation, seafloor spreading and mantle convection

In the last 10 Ma, the northwest Barents Sea passive margin and Svalbard archipelago experienced tectonic reactivation including regional uplift, volcanism and fault movements. Previous studies have variously attributed this reactivation to the establishment of continuous seafloor spreading between the North Atlantic and Arctic oceans within the Fram Strait, mantle convection, or a lithospheric response to climate-driven processes such as fluvial and glacial erosion in a late Pliocene-Pleistocene time (∼1-3 Ma). The relative magnitudes, and the physical relationship between surface processes, plate boundaries and mantle flow, has remained unclear. In this work, I jointy interpret seismological models of the upper mantle, gravity anomalies, rates of glacial isostatic adjustment (GIA) and the spatiotemporal characteristics of earthquakes with the aim to i) constrain the thermal state and rheological structure of the upper mantle beneath Svalbard, ii) infer the magnitude of vertical motion in the late Cenozoic time related to various processes, iii) better understand the likely causes of the tectonic and volcanic activity.Most part of the northwest Barents Sea passive margin including Svalbard is underlain by a thin continental lithosphere (∼50–80 km) and a normal thickness of crust (30–35 km). The geophysical data indicate an average excess mantle temperature of ∼40–100°C beneath western Svalbard compared to the central Barents Sea. The peak of the mantle temperature anomaly coincides with the location of Quaternary basalt eruptions. The predicted long-wavelength (>420 km) non-isostatic uplift of ∼600-800 m correlates with the distribution of pre-glacial uplift previously inferred from geological data in the northwest Barents Sea. The gravity anomalies within an intermediate range of wavelengths (30–420 km) allows me to estimate topography changes due to erosion by ice streams to be ∼200–500 m. I conclude that a transient temperature anomaly in the asthenosphere northeast of Jan Mayen, combined with the northwest absolute plate motion of Eurasia, is the likely primary cause of the late Cenozoic tectonic reactivation in Svalbard.

Bivalve growth rate and isotopic variability across the Barents Sea Polar Front

Analysis of bivalve shell increments provides a means to reconstruct long-term patterns in growth histories and assess factors that regulate marine ecosystems, while tissue stable isotopes are indicators of food sources and trophic dynamics. We examined shell growth patterns and tissue stable isotopic composition (δ13C and δ15N) of the hairy cockle (Ciliatocardium ciliatum) in the northwest Barents Sea to evaluate the influence of different water masses and the Polar Front on growth rates and food sources and to assess the influence of climatic variability on ecological processes over seasonal to decadal scales. Shell growth rates were highest in Atlantic water, intermediate in Arctic water, and lowest at the Polar Front. Temporal patterns of ontogenetically-adjusted growth (SGI) were negatively correlated with the Atlantic Multidecadal Oscillation (AMO), local precipitation and ice-free days. The highest growth occurred during colder periods with more sea ice, while lower growth was associated with warmer periods and less sea ice. Stable isotope values of lipid-extracted tissues from Atlantic water cockles were enriched in δ13C by up to 2.1‰ and δ15N by 1.5‰ compared to animals from Arctic waters. Distinct seasonal and water mass variations in stable isotopic values reflect spatial and temporal variability in food supplies to the bivalves in this region on small spatial scales. Overall, Atlantic waters supported the highest growth rates, the most complex trophic webs, and the greatest sensitivity to interannual variability in environmental conditions. Bivalves from Arctic waters were the most distinct of the three groups in their response to regional climate forcing and local environmental manifestations of those conditions. The Polar Front exhibits growth and isotopic characteristics predominantly of the Atlantic domain.These results demonstrate that integrating results of sclerochronological and stable isotopic analyses of benthic bivalves provide independent, corroborative lines of evidence and added insight into the ecological function of these systems when assessing potential effects of changes in water mass distributions in the Barents Sea.

Oil exploration and sea ice projections in the Arctic

ABSTRACTThe aim of this study is to investigate how reduction in the sea ice cover may affect oil activity in the Arctic during the next 30 years. The Arctic is divided into 21 oil provinces. A multidisciplinary approach is applied drawing on both the comparative cost techniques as developed in location theory and sea ice cover projections. The comparative cost technique implies a systematic listing of cost differentials by oil provinces. The sea ice projections are based on the NCAR CCSM3 global climate model under the A1B and A2 emission scenarios. The article concludes that the north Norwegian Sea, and south and west Barents Sea will remain the most attractive areas for oil exploration in the coming 30 years. Furthermore, due to sea ice decline, the north and east Barents Sea and north and west Kara Sea will become more attractive. However, most Arctic provinces will remain high cost regions.

The results of complex geophysical investigations in the northwest Barents Sea shelf (at the junction between the Svalbard Anteclise and East Barents Megatrough)

These studies allowed the tectonic zoning of an area to be performed, as well as the identification of the structural elements of different ranks. Within the studied area, such large positive first-order structures as the Shirshov and Dezhnev hemibars, Voronin Rise, and Nobile Structural Terrace were distinguished. As well, the quality of seismic materials allowed us to confidently determine the fault systems and to map them, as well as to understand the ways in which they were formed.

Seabed morphology and shallow sedimentary structure of the Storfjorden and Kveithola trough-mouth fans (North West Barents Sea)

This study aims to present an overview of the seafloor morphology and shallow sedimentary structure of the Storfjorden and Kveithola Trough Mouth Fans (TMFs) on the northwestern Barents Sea continental margin. Data have been compiled from two International Polar Year (IPY) cruises (SVAIS, of the BIO Hespérides and EGLACOM of the R/V OGS-Explora) that yielded 15,340 km 2 of multi-beam bathymetry and 9500 km of sub-bottom seismic profiles. In this area, the continental shelf edge defines three wide and subdued sedimentary lobes forming Storfjorden TMF, one single lobe on Kveithola TMF, and three inter-TMF areas on the continental slope. The two northernmost lobes of Storfjorden TMF (Lobes I and II) are composed by thick (up to 50 m) sequences of glacially derived debris flow deposits interbedded with thin a few metres de-glacial and interglacial deposits. A network of upper slope gullies incises these debris flow deposits as a consequence of subglacial meltwater release at or near the shelf break. Gullies evolve into channels whose morphologic evidence disappears midslope, leaving place to a subdued chevron-like morphological pattern inherited by the preceeding glacial maximum debris flow deposits. A drastic change occurs on the continental slope of Storfjorden TMF Lobe III and Kveithola TMF, where are several translational submarine landslides mostly originated in the upper slope, the majority of which detach at the contact between Middle Weishelian glacigenic debris flows and the overlying acoustically laminated plumites. Dendritic canyon systems only develop in inter-TMF areas. The data suggest that TMF continental slope progradation depends on short-lived episodes of extreme sedimentation during glacial maxima and during the early deglaciation phase, and that an important controlling factor is the mechanism of ice stream retreat from the continental shelf edge. We suggest that the two northern Storfjorden sub-ice streams were composed of thicker and perhaps faster ice progressively draining a distal and larger ice source mainly located on Svalbard. Conversely, the southernmost Storfjorden sub-ice stream and the Kveithola ice stream were fed by a local, smaller marine-based ice dome grounded on Spitsbergenbanken. The ice dome persisted after the LGM, maintaining a local ice drainage system close to the shelf edge whose sedimentary evidence can be found on the continental slope of the southern lobe of Storfjorden TMF and Kveithola TMF. The high degree of lateral variability in the style of sedimentation on TMF slopes suggests that ice stream dynamics may vary considerably within the same glacial trough, and that such variability affects the long-term development of the architecture of TMFs.

Dolerites of Svalbard, north-west Barents Sea Shelf: age, tectonic setting and significance for geotectonic interpretation of the High-Arctic Large Igneous Province

The dolerites of Svalbard are mineralogically and geochemically homogeneous with geochemical features typical of continental within-plate tholeiites. Their geochemistry is similar to tholeiites belonging to a bimodal suite defined as the High-Arctic Large Igneous Province (HALIP). K-Ar dating of numerous dolerites sampled from many locations across Svalbard define a narrow time span of this magmatism from 125.5±3.6 to 78.3±2.6 Mya. Discrete peaks of intensive activity occurred at 115.3, 100.8, 91.3 and 78.5 Mya corresponding to breakup of the continental crust and formation of an initial rift as a result of mantle plume activity, located in the southern part of the Alpha Ridge; magmatic activity related to spreading along the Alpha Ridge that led to the development of the initial oceanic crust and continuation of spreading along the Alpha Ridge and termination of magmatic activity related to HALIP (last two peaks at 91.3 and 78.5 Mya). Keywords: Dolerite; geochemistry; petrogenesis; K-Ar whole rock ages; Svalbard; Cretaceous (Published: 3 August 2011) Citation: Polar Research 2011, 30 , 7306, DOI: 10.3402/polar.v30i0.7306

Winter distribution of euphausiids (Euphausiacea) in the Barents Sea (2000–2005)

Abstract The purpose of the study is to analyze the state of the Barents Sea euphausiids populations in the warm period (2000–2005) based on the study of their structure dynamics and distribution under the influence of abiotic and biotic factors. For estimation of their aggregations in the bottom layer, the traditional method was used with the help of the modified egg net (0.2 m 2 opening area, 564 μm mesh size). The net is used for collecting euphausiids in the autumn–winter period when their activity is reduced, which results in high-catch efficiency. The findings confirmed the major formation patterns of the euphausiids species composition associated with climate change in the Arctic basin. As before, in the warm years, one can see a clear-cut differentiation of space distribution of the dominant euphausiids Thysanoessa genus with localization of the more thermophilic Thysanoessa inermis in the north-west Barents Sea and Thysanoessa raschii in the east. The major euphausiids aggregations are formed of these species. In 2004, the first data of euphausiids distribution in the northern Barents Sea (77–79°N) were obtained, and demonstrated extremely high concentrations of T. inermis in this area, with the biomass as high as 1.7–2.4 g m −2 in terms of dry weight. These data have improved our knowledge of the distribution and euphausiids abundance during periods of elevated sea-water temperatures in the Barents Sea. The oceanic Atlantic species were found to increase in abundance due to elevated advection to the Barents Sea during the study period. Thus, after nearly a 30-year-long absence of the moderate subtropical Nematoscelis megalops in the Barents Sea, they were found again in 2003–2005. However in comparison with 1960, the north-east border of its distribution considerably shifted to 73°50′N 50°22′E. The portion of Meganyctiphanes norvegica also varied considerably—from 10% to 20% of the total euphausiids population in the warm 1950s–1960s almost to complete disappearing in 1970–1990s. The peak of this species’ occurrence (18–26%) took place in the beginning of warm period (1999–2000) after a succession of cold years. The subsequent reduction of the relative abundance of M. norvegica to 7% might have been mostly caused by fish predation during a period of low population densities of capelin. This high predation pressure may therefore have been mediated both by other pelagic fishes (i.e. herring, blue whiting, polar cod) but also by demersal fishes such as cod and haddock. Similar sharp fluctuations in the capelin stock (the major consumer of euphausiids) created marked perturbations in the food web in the Barents Sea in the middle 1980s and the early 1990s.

Interannual variability of dense shelf water salinities in the north-western Barents Sea

The maximum dense shelf water salinity formed during winter in the Svalbard Bank area of the north-western Barents Sea is reconstructed for the period 1952–2000 by analysing the transformation of summer remnants. The variability of 34.7 - 35.4, waters being at the freezing point, is mainly generated by interannual variations in the near surface salinity. On interannual time scales the latter is strongly linked to the sea ice import. In contrast, no correlation of the salinity of the Atlantic Water (AW) throughflow to the Arctic Ocean with the ice import is found. Salinities of both the dense shelf water site in the north-west Barents Sea and the north-eastward AW throughflow show a long term decrease, which can partly be explained by a less saline inflow of AW from the Norwegian Sea. The unusually low dense water salinities in the north-west Barents Sea during the 1990s appear to have a different origin, consistent with a response to oceanic heat advection and decreasing sea ice extent.

Long-term near-bed observations of velocity and hydrographic properties in the northwest Barents Sea with implications for sediment transport

Combined results from time-series observations of currents and water properties from two moorings and a benthic tripod measuring near-bed velocity profiles are used to evaluate the potential for sediment transport in the Storfjord, east of Hopen Island, and in Olgastretet in the Barents Sea near the southeast Svalbard Archipelago. Current observations include a 15-month time series from each mooring with the lowermost current meter on each mooring positioned at 6 mab and a 5-month time series from the tripod with four current meters located within 1.2 mab. Threshold of grain motion was estimated from seabed sediment characteristics sampled at each site, bed roughness length was calculated from the benthic tripod velocity profiles. Results from the Storfjord and east of Hopen Island suggest that near-bed currents and bottom stresses cannot resuspend sediment in the summer months. Currents exceed the threshold of grain motion during the fall and winter months in response to strong flows forced by surface cooling and winds. Threshold of grain motion occurs for approximately 10 days per year in both the Storfjord and east of Hopen Island. In Olgastretet, measured bottom currents had distinct reversals from north to south over periods of 3–8 days throughout the record. The highest currents (and largest bottom stresses) were directed southward and were high enough to resuspend bottom sediment about 19 days during the deployment period. Near-bottom flows are dominantly southward at all stations during times that sediment threshold velocities are exceeded, thus strong flows exiting the fjords in southern Svalbard during winter may also transport significant quantities of sediment into the deep northern Norwegian Sea.