Northwestern Barents Sea Research Articles

Background concentrations of polycyclic aromatic hydrocarbons (PAHs) in deep core sediments from the Norwegian Sea and the Barents Sea: A proposed update of the OSPAR Commission background values for these sea areas

Geochemical studies of 174 sediment cores collected by the MAREANO mapping program in Norwegian waters of the North Atlantic Ocean give new sets of values of background concentrations (BCs) for polycyclic aromatic hydrocarbons (PAHs) for the studied regions. The study is based on deep core sediment samples representing background levels of PAHs. The samples selected were only from the deeper parts of undisturbed sediment cores with low, stable concentrations of petrogenic and pyrogenic PAHs, with low variation for individual PAH compounds between the samples within the same core, and from below the parts of the cores dated with 210Pb to approximately the last 100–150 years. The results show that the main part of the studied area has BCs different from those previously established by OSPAR Commission (OSPAR) for the North-East Atlantic. Another area in central Barents Sea has a separate set of BCs of pyrogenic PAHs, apparently due to the influence from marginal ice zone mechanisms. A third area with its own set of BCs has been established for north-western Barents Sea off the coast of Svalbard, due to high natural contents of PAHs in this area. BCs for several PAHs not included in the present OSPAR list are also provided.

Phytoplankton communities of the Barents Sea frontal zone during the early spring period

In April 2018, complex studies of phytoplankton communities were carried out in the northwestern Barents Sea in the region of the Polar Front (74.8°-76.2° N) in a layer of 0-50 m. The region under study encompassed surface Arctic water and Atlantic water of the Fram branch (which conditionally corresponds to the Arctic water mass) divided from the Atlantic water mass by the Polar Front. Phytoplankton community on both sides of the front were represented by early spring complex, 90% of biomass was formed by diatoms (Achnanthes taeniata, Nitzschia grunowii, Thalassiosira antarctica). In water of Atlantic origin Phaeocystis pouchetii were found among the dominants. However, the level of development of microplankton was significantly higher in water from the Arctic Basin. The highest chlorophyll-a concentrations referred to surface Arctic water (3.13±0.43 mg/m3) and Atlantic Fram water (2.04±0.29 mg/m3). The concentration of chlorophyll-a at the stations performed in the Atlantic water mass was an order of magnitude lower - 0.50±0.26 mg/m3. Thus, during the early-spring period, the Polar Front is a powerful boundary that limits exclusively the level of development and quantitative indicators of the early spring microphytoplankton complex. The front line separates the more productive Arctic water, with average chlorophyll-a concentrations of 2-3 mg/m3, from the Atlantic water, in which concentrations of this pigment are an order of magnitude lower.

Trends in cyclones in the high‐latitude North Atlantic during 1979–2016

AbstractWe report an increase in winter (DJF) cyclone densities in the areas around Svalbard and in northwestern Barents Sea and a decrease in cyclone densities in southeastern Barents Sea during 1979–2016. Despite high interannual variability, the trends are significant at the 90% confidence level. The changes appear as a result of a shift into a more meridional winter storm track in the high‐latitude North Atlantic, associated with a positive trend in the Scandinavian Pattern. A significant decrease in the Brunt–Väisälä frequency east of Svalbard and a significant increase in the Eady Growth Rate north of Svalbard indicate increased baroclinicity, favouring enhanced cyclone activity in these regions. For the first time, we apply composite analysis to explicitly address regional consequences of these wintertime changes in the high‐latitude North Atlantic. We find a tendency toward a warmer and more moist atmospheric state in the Barents Sea and over Svalbard with increased cyclone activity around Svalbard.

A refined age calibrated paleosecular variation and relative paleointensity stack for the NW Barents Sea: Implication for geomagnetic field behavior during the Holocene

Reconstruction of Paleomagnetic Secular Variation (PSV) of the geomagnetic field is fundamental both to assess geodynamo models and to obtain age constraints for rocks, sediments and archaeological material. We present refined age-calibrated Holocene PSV and relative paleointensity (RPI) stack curves derived from Arctic marine sediments (Northwestern Barents Sea). The Holocene sections of four sedimentary cores were correlated on the basis of paleomagnetic trends and age models, and stacked. The resultant composite PSV and RPI Holocene records (NBS stack) and the reconstructed Holocene Virtual Geomagnetic Pole (VGP) path were evaluated in comparison with the most recent paleomagnetic stack curves and geomagnetic field models. The data indicate that during the Holocene time, the VGPs moved within the superficial projection of the inner core tangent cylinder, with the exception of short time intervals around 5600 and 3200 cal yr BP when VGPs extended to lower latitudes. These deviations might reflect regional geomagnetic features, such as persistent geomagnetic flux lobes at core-mantle boundary. Our data confirm that the large VGP shift observed around 5600 cal yr BP is the result of an increased radial magnetic field at the core-mantle boundary over North America, whilst the VGP shift around 3200 cal yr BP represents a major swing to middle latitudes toward the Middle East and might be associated to a regional high paleointensity peak, known as Levantine Iron Age Anomaly (LIAA).

Methane-fuelled biofilms predominantly composed of methanotrophic ANME-1 in Arctic gas hydrate-related sediments

Sedimentary biofilms comprising microbial communities mediating the anaerobic oxidation of methane are rare. Here, we describe two biofilm communities discovered in sediment cores recovered from Arctic cold seep sites (gas hydrate pingos) in the north-western Barents Sea, characterized by steady methane fluxes. We found macroscopically visible biofilms in pockets in the sediment matrix at the depth of the sulphate-methane-transition zone. 16S rRNA gene surveys revealed that the microbial community in one of the two biofilms comprised exclusively of putative anaerobic methanotrophic archaea of which ANME-1 was the sole archaeal taxon. The bacterial community consisted of relatives of sulphate-reducing bacteria (SRB) belonging to uncultured Desulfobacteraceae clustering into SEEP-SRB1 (i.e. the typical SRB associated to ANME-1), and members of the atribacterial JS1 clade. Confocal laser scanning microscopy demonstrates that this biofilm is composed of multicellular strands and patches of ANME-1 that are loosely associated with SRB cells, but not tightly connected in aggregates. Our discovery of methanotrophic biofilms in sediment pockets closely associated with methane seeps constitutes a hitherto overlooked and potentially widespread sink for methane and sulphate in marine sediments.

Postglacial paleoceanography and paleoenvironments in the northwestern Barents Sea

AbstractThe Barents Sea offers a suitable location for documenting advection of warm and saline Atlantic Water (AW) into the Arctic and its impact on deglaciation and postglacial conditions. We investigate the timing, succession, and mechanisms of the transition from proximal glaciomarine to marine environment in the northwestern Barents Sea. Two studied sediment cores demonstrate diachronous retreat of the grounded ice sheet from the Kvitøya Trough (core S2528) to Erik Eriksen Trough (core S2519). Oxygen isotope records from core S2528 depict a two-step pattern, with lower δ18O values prior to the Younger Dryas (YD), and higher values afterward because of advection of the more saline,18O-enriched AW. At this location, subsurface AW penetration increased during the Allerød and YD/Preboreal transition. In the study area, foraminiferal and dinocyst data from the YD interval suggest cold conditions, extensive sea-ice cover, and brine formation, along with the flow of chilled AW at subsurface and the development of a high-productivity polynya in the Erik Eriksen Trough. Dense winter sea-ice cover with seasonal productivity persisted in the Kvitøya Trough area during the early Holocene, whereas surface warming seems to have occurred during the middle Holocene interval.

Geological Controls on Fluid Flow and Gas Hydrate Pingo Development on the Barents Sea Margin

AbstractIn 2014, the discovery of seafloor mounds leaking methane gas into the water column in the northwestern Barents Sea became the first to document the existence of nonpermafrost‐related gas hydrate pingos (GHPs) on the Eurasian Arctic shelf. The discovered site is given attention because the gas hydrates occur close to the upper limit of the gas hydrate stability, thus may be vulnerable to climatic forcing. In addition, this site lies on the regional Hornsund Fault Zone marking a transition between the oceanic and continental crust. The Hornsund Fault Zone is known to coincide with an extensive seafloor gas seepage area; however, until now lack of seismic data prevented connecting deep structural elements to shallow seepages. Here we use high‐resolution P‐Cable 3‐D seismic data to study the subsurface architecture of GHPs and underlying glacial and preglacial deposits. The data show gas hydrates, authigenic carbonates, and free gas within the GHPs on top of gas chimneys piercing a thin section of low‐permeability glacial sediments. The chimneys connect to faults within the underlying tilted and folded fluid and gas‐hydrate‐bearing sedimentary rocks. Correlation of our data with regional 2‐D seismic surveys shows a spatial connection between the shallow subsurface fluid flow system and the deep‐seated regional fault zone. We suggest that fault‐controlled Paleocene hydrocarbon reservoirs inject methane into the low‐permeability glacial deposits and near‐seabed sediments, forming the GHPs. This conceptual model explains the existence of climate‐sensitive gas hydrate inventories and extensive seabed methane release observed along the Svalbard‐Barents Sea margin.

Late Cenozoic Erosion Estimates for the Northern Barents Sea: Quantifying Glacial Sediment Input to the Arctic Ocean

AbstractA compilation of seismic data has been used to characterize the Neogene‐Quaternary sedimentary succession of the northwestern Barents Sea continental margin to better understand the paleoenvironmental evolution and the sedimentary processes involved. The Neogene strata are dominated by contourites related to the ocean circulation established from the opening of the Fram Strait connecting the Atlantic and the Arctic Oceans (< ~17.5 Ma). The upper Plio‐Pleistocene strata (< ~2.7 Ma) are dominated by stacked gravity‐driven deposits forming trough‐mouth fans that were sourced from paleo‐ice streams. Within the interfan areas, contouritic sedimentation prevailed. Thus, this margin provides an example of interaction of glacigenic debris flows, contour currents, and hemipelagic/glacimarine sedimentary processes. A total of ~29,000 km3 of sediments with an average sedimentation rate of about 0.24 m/Kyr were estimated. These numbers reflect the sediment input to this part of the Arctic Ocean from the northwestern Barents Sea shelf and adjacent land areas. For the first time, the average erosion and erosion rates for this source area are estimated using a mass balance approach. Approximately 410–650 m of erosion has on average occurred, corresponding to an average erosion rate of ~0.15–0.24 m/Kyr. These rates are comparable to those reported from other glaciated margins, including the western Svalbard and mid‐Norway margin, but up to only half the rates reported from the western Barents Sea margin. This variation is interpreted due to the size and bedrock types of the drainage area, ice dynamics, and the continental slope gradient.

Early Holocene Establishment of the Barents Sea Arctic Front

A main feature of the Barents Sea oceanography is the Arctic front. The Arctic front marks the transition between the southern Atlantic water and northern Arctic water dominated parts of the Barents Sea. Presently, the Barents Sea Arctic front is directed by the topography of the Bear Island Trough and to some degree the location of the Marginal Sea Ice Zone. During the last glacial maximum, the Svalbard-Barents Sea and Scandinavian Ice Sheets covered the Barents Sea. Hence, no water entered the Barents Sea, neither from the south nor from the north. Following the deglaciation of the Barents Sea, the present-day ocean circulation developed. The evolution of how the present location of the Barents Sea Arctic front established during the early Holocene is documented by foraminiferal relative assemblage data from six core sites along the western Barents Sea margin and entrance. The relative abundance of Arctic front indicator Turborotalita quinqueloba, in combination with the cold, polar Neogloboquadrina pachyderma and warm, Atlantic Neogloboquadrina incompta, are used to infer the location of the Barents Sea Arctic front relative to the individual core sites. Until ca. 11 ka BP, the Barents Sea Arctic front followed the western margin of the Barents Sea. All sites along the Barents Sea margin where still dominated by Arctic water between ca. 11 and 10.2 ka BP, however, the Barents Sea Arctic front turned eastwards into the southwestern Barents Sea. From ca. 10 to 8.8 ka BP, the Barents Sea Arctic front followed the Barents Sea margin and the northern and southern borders of the Bear Island Trough. Hence, from this time on the topography of the Bear Island Trough became a steering component. The northwestern Barents Sea Arctic front was close to the present location from ca. 8.8 to 7.4 ka BP, however, it was still confined to the southwestern Barents Sea. From ca. 7.4 ka BP, the Barents Sea Arctic front has been located close to the present position, along the margin southwards from Svalbard, turning eastwards along and beyond the northern Bear Island Trough margin.

A new multi‐proxy investigation of Late Quaternary palaeoenvironments along the north‐western Barents Sea (Storfjorden Trough Mouth Fan)

ABSTRACTA new integrated micropalaeontological study on planktonic and benthic foraminifera, calcareous nannofossils and diatoms was performed on three sediment cores from the Storfjorden Trough Mouth Fan to reconstruct the Late Quaternary palaeoenvironmental and climatic history. Two main intervals were discussed: the last deglaciation (16.2–11.7 ka BP) and the Holocene. The age model relies on palaeomagnetic parameters together with 10 radiocarbon dates. Deglacial sediments had largely diluted the biogenic content which was scarce and poorly preserved. The first occurrence of Cibicidoides wuellerstorfi (benthic foraminifer), together with Turborotalita quinqueloba (planktonic foraminifer) and Coscinodiscus spp. (diatoms) at 11.3 ka BP followed the end of the Younger Dryas cold event and marked the beginning of the early Holocene warm period. Diatoms and planktonic foraminifers indicated a warming of the surface water from 10.5 to 9.2 ka BP, identifying the Holocene Thermal Maximum event. Bottom water fauna registered these warming conditions less clearly. Cooling events were identified during the Holocene, in particular the 8.2 ka BP event and the Neoglacial between 3.2 and 2 ka BP, as shown by the presence of cold‐water taxa such as Gephyrocapsa muellerae (nannoplankton) and Neogloboquadrina pachyderma (planktonic foraminifer). These events were influenced by sea ice extent, cold or relatively warm current influxes.

Cenozoic tectonostratigraphy and pre-glacial erosion: A mass-balance study of the northwestern Barents Sea margin, Norwegian Arctic

The evolution of the northwestern Barents Sea continental margin, part of a NW-SE trending mega shear zone, has been reconstructed in order to quantify the sedimentation and erosion affecting this area during and after its formation in the Paleogene–Neogene. This development was closely related to the sea-floor opening of the Norwegian-Greenland Sea. Our study incorporated 2D seismic data, well data, and information from shallow cores.During the Paleocene–Eocene, the northwesternmost Barents Sea margin was subjected to compression-transpression that led to the development of the West Spitsbergen Fold-Thrust Belt (WSFTB) and largely affected the northern part of the study area. To the south, the Vestbakken volcanic province developed in a pull-apart setting. A transition zone separates these two areas marked by a basin morphology becoming more pronounced to the south suggesting increasing subsidence and extension. Subsequently, during the Oligocene, extension and sea-floor spreading were initiated along the whole margin, resulting in the opening of the Fram Strait between Spitsbergen and NE Greenland in the Miocene.During the Paleocene, the Stappen High and a part of the NE Greenland shelf sourced sediments into the newly developing basins. The southwestern part of the WSFTB, the Stappen High, and part of the NE Greenland margin are interpreted as the main sediment source areas in the Eocene. During the Oligocene and Neogene, a larger part of the northwestern Barents Sea shelf is interpreted to have acted as source area including the Edgeøya platform. As a result of this development, the wider Barents Sea shelf itself is inferred to have been a lowland prior to the northern hemisphere glaciations.We found that the average sedimentation rate for the Paleogene–Neogene at the northwestern Barents Sea margin is about 0.034 m/k.y. This number is in agreement with the sedimentation rate reported from present-day fluvial systems and modern rates coastal erosion. By using a mass-balance approach, we have also estimated the average net erosion and erosion rate for the Paleogene–Neogene period to be ∼2440 m and 0.038 m/k.y, respectively. This erosion rate is two times higher compared to the southwestern Barents Sea margin, probably reflecting erosion of a more tectonically active northwestern margin. Thus, for the western Barents Sea margin, a general increasing trend of pre-glacial erosion northwards can be inferred. This study also suggests that more than half of the Cenozoic erosion affecting the studied part of the northwestern Barents Sea were of pre-glacial origin.

Reconstruction of ice sheet retreat after the Last Glacial maximum in Storfjorden, southern Svalbard

Storfjorden is a large north-south trending sound located in the southern part of Svalbard in the northwestern Barents Sea. Presently, several glaciers drain into the northern and western part of Storfjorden. Our study area covers the southern part of the sound, which is divided by a north-south striking basement ridge (the ‘Mid-ridge’) into a narrow western trough (‘Little-Storfjorden’) and a broader eastern trough (‘Storfjorden’). In the latter, three grounding-zone wedges (GZWs) were discovered in 2005 showing evidence of former grounded ice. Here we confirm the existence and map the extent of the GZWs and reconstruct the pattern and timing of ice retreat in Storfjorden during the deglaciation. The study is based on high-resolution seismic and shallow-acoustic profiles and swath bathymetry, combined with information of lithology and radiocarbon dates from sediment cores. The results show that the three GZWs stretch across the fjord, and that all three are located south of higher basement areas that were upstream of the GZWs and which acted as pinning points during ice retreat. The Mid-ridge imposed a lateral drag to the ice, resulting in an uneven ice retreat across the fjord. Outside of the GZWs only a thin cover of glacial deposits was found. The cores were taken in vicinity of the GZWs and all reached till deposits overlain by glacimarine or hemipelagic sediments, enabling dating of the GZWs. Altogether we find that the fjord and basement topography played an important role in the ice retreat. AMS-14C dates show that the formation of the three GZWs correlate with three well-known atmospheric warming phases (start of Bølling interstadial, Allerød interstadial and Holocene interglacial, respectively) associated with inflows of warm Atlantic water, indicating a strong ocean/climate control on the deglaciation of Storfjorden.

Paleomagnetism and rock magnetism from sediments along a continental shelf-to-slope transect in the NW Barents Sea: Implications for geomagnetic and depositional changes during the past 15 thousand years

Abstract Paleomagnetic and rock magnetic data were measured on glaciomarine silty-clay successions along an E-W sediment-core transect across the continental shelf and slope of the Kveithola paleo-ice stream system (south of Svalbard, north-western Barents Sea), representing a stratigraphic interval spanning the last deglaciation and the Holocene. The records indicate that magnetite is the main magnetic mineral and that magnetic minerals are distinctly less abundant on the shelf than at the continental slope. The paleomagnetic properties allow for the reconstruction of a well-defined characteristic remanent magnetization (ChRM) throughout the sedimentary successions. The stratigraphic trends of rock magnetic and paleomagnetic parameters are used for a shelf-slope core correlation and sediment facies analysis is applied for depositional processes reconstruction. The new paleomagnetic records compare to the PSV and RPI variation predicted for the core sites by a simulation using the global geomagnetic field variation models SHA.DIF.14k and CALS7K.2 and closest PSV and RPI regional stack curves. The elaborated dataset, corroborated by available 14C ages, provides a fundamental chronological framework to constrain the coupling of shelf-slope sedimentary processes and environmental changes in the NW Barents Sea region during and after deglaciation.

Velocity anisotropy of Upper Jurassic organic-rich shales, Norwegian Continental Shelf

This study investigates the seismic velocity anisotropy of two organic-rich shales from the Norwegian Continental Shelf. The tested organic-rich shale samples were from the Upper Jurassic Draupne and Hekkingen formations collected from two wells (16/8-3S and 7125/1-1) drilled in the central North Sea and western Barents Sea, respectively. The two tested shales are different in organic matter richness and thermal maturation, and they have experienced different burial histories. The shale core plugs were tested in a triaxial cell under controlled pore pressure. Seismic velocities ([Formula: see text] and [Formula: see text]) were measured along different orientations with respect to layering to identify the complete tensor of the rock elastic moduli, and to investigate the velocity anisotropy as a function of increasing effective stress. The measured velocity values exhibit strong anisotropy for the two tested organic-rich shales. The anisotropy for both shales is strongest for [Formula: see text]. Seismic velocities follow an increasing trend as the effective stress increases. The anisotropy decreases somewhat with increasing consolidation, probably due to the closing of preexisting fractures and microcracks. The reduction of anisotropy is more evident for the P-wave because it decreases from 0.32 to 0.25 for the Draupne sample and from 0.28 to 0.24 for the Hekkingen sample when the vertical effective stress increases from 26 to 50 MPa. In general, the Hekkingen sample indicates slightly higher velocity values than the Draupne sample due to more compaction and lower porosity. In spite of major differences between the two shale formations in terms of organic matter content, maturity and burial history, they indicate almost the same degree of velocity anisotropy. The outcomes of this study can contribute to better imaging of organic-rich Draupne and Hekkingen shales by constraining the rock-physics properties.

Sea-ice thickness from field measurements in the northwestern Barents Sea

The Barents Sea is one of the fastest changing regions of the Arctic, and has experienced the strongest decline in winter-time sea-ice area in the Arctic, at -23 +/- 4% per decade. Sea-ice thickness in the Barents Sea is not well studied. We present two previously unpublished helicopter-borne electromagnetic (HEM) ice thickness measurements from the northwestern Barents Sea acquired in March 2003 and 2014. The HEM data are compared to ice thickness calculated from ice draft measured by ULS deployed between 1994 and 1996. These data show that ice thickness varies greatly from year to year; influenced by the thermodynamic and dynamic processes that govern local formation vs long-range advection. In a year with a large inflow of sea-ice from the Arctic Basin, the Barents Sea ice cover is dominated by thick multiyear ice; as was the case in 2003 and 1995. In a year with an ice cover that was mainly grown in situ, the ice will be thin and mechanically unstable; as was the case in 2014. The HEM data allow us to explore the spatial and temporal variability in ice thickness. In 2003 the dominant ice class was more than 2 years old; and modal sea-ice thickness varied regionally from 0.6 to 1.4 m, with the thinner ice being either first-year ice, or multiyear ice which had come into contact with warm Atlantic water. In 2014 the ice cover was predominantly locally grown ice less than 1 month old (regional modes of 0.5–0.8 m). These two situations represent two extremes of a range of possible ice thickness distributions that can present very different conditions for shipping traffic; or have a different impact on heat transport from ocean to atmosphere.

Svalbard ice-sheet decay after the Last Glacial Maximum: New insights from micropalaeontological and organic biomarker paleoceanographical reconstructions

A marine sediment core retrieved from the middle continental slope of the northwestern Barents Sea was analyzed for its geochemical (alkenones) and micropalaeontological (diatoms, coccolithophores and dinocyst) content in order to reconstruct the evolution of upper ocean conditions and ice-sheet dynamics during the last 25kyr. Additionally, quantitative reconstructions of sea surface conditions (temperature, salinity and sea-ice cover extent) were conducted based on the best analogue technique applied to dinocyst assemblages and on the alkenone unsaturation index. The sediment core contains a post Last Glacial Maximum depositional sequence unaffected by stratigraphic discontinuities. Low salinity and laminated sediments after 20calkyr BP, indicate a massive settling of meltwater sediment-laden plumes from the initial melting of the Svalbard-Barents Sea Ice Sheet on Western Svalbard. First record of measurable alkenones, together with a drop of the number of months of sea-ice cover and increase in SSTs suggests an intensification of the influx of Atlantic waters into the study area at ~15calkyr BP representing the termination of the last glacial period and onset of the Bølling interstadial. The first occurrence of diatoms and increase in the abundance of all microfossils marked the onset of the Holocene at 11.2calkyr BP when modern-type sea surface conditions were rapidly established in Western Svalbard. Reconstructions based on dinocyst data and alkenone unsaturation index suggest relatively warm and stable temperatures between 9.9 and 8.9kyr BP and a decrease of SSTs from 4.2calkyr BP to present coinciding with the Holocene Thermal Maximum and the decrease of summer insolation in the high latitude northern hemisphere, respectively.

Anomalous hydrographic conditions in the western Barents Sea observed in March 2014

Observational data have been collected during a cruise to the western Barents Sea in March 2014 covering 33 stations along three west–east sections at 76.34°N, 77.26°N and 78.49°N and along one south–north section at 19.47°E. Our observations suggest a wedge-like water masses structure with colder and fresher Arctic Water moving southward, gliding over warmer and more saline Atlantic Water which below the surface moves to the north. Atlantic Water in the Storfjorden Trench reached farther north than 76.5°N and was present on the eastern and western slopes of the Spitsbergen Bank. Our measurements indicate limited dense water formation in the Storfjorden. A comparison with historical data over the years 1923–2011 reveal an anomalous northern location of the Polar Front for this time of the year in March 2014. A point by point comparison with ten historical stations in 1983 and 1986 shows significantly warmer (by up to 3.8°C) and saltier (by up to 2.49psu) conditions in 2014 for nine out of ten stations. Moreover, stations dominated by the Atlantic inflow experienced the largest changes, whereas in stations located in the area of the Arctic outflow the changes were smallest. Furthermore, we used satellite and decadal reanalysis data to estimate the climate variability defined by a range of two standard deviations. We found that in the Storfjorden Trench in March 2014 the water transport was within the range, while the water temperature exceeded the upper limit of climate variability. The sea ice extent in the western Barents Sea was below the lower limit of climate variability from mid-February to mid-March 2014. Combining in situ, satellite and model data, we were able to attribute the warm anomaly observed in March 2014 to two main reasons: (1) an increase of Atlantic water temperature which was evident already in the beginning of 2014 and (2) very little cooling in February and March 2014. From these results we conclude that the north-western Barents Sea is a key region to monitor local response on climate change signals in the Arctic Ocean.

Late Quaternary development of the Storfjorden and Kveithola Trough Mouth Fans, northwestern Barents Sea

The development of two Arctic Trough Mouth Fans (TMFs), the Storfjorden and Kveithola TMFs, is investigated by means of sub-bottom and seismic reflection profiles, multibeam bathymetry and sediment samples allowing their detailed stratigraphic architecture to be defined. We find that the TMFs mainly consist of an alternation of rapidly deposited glacigenic debris flows during glacial maxima and a sequence of well-layered plumites and hemipelagic sediments, which were mainly deposited during the deglaciation phase of the adjacent glacial trough. We have identified eight units above regional reflector R1, which indicate that the ice sheet reached the shelf edge within the Storfjorden Trough on at least three occasions during the last ∼200 ka. A shallow subsurface unit of glacigenic debris flows suggests that the ice sheet had a short re-advance over the northern and central part of Storfjorden after the Last Glacial Maximum. From stratigraphy, core and literature data, we estimate that ice sheets reached the shelf edge between 19.5 to 22.5 ka, 61 to 65 ka and 135 to 167 ka. Detailed seismic imaging allows us to refine the sedimentary model of Arctic TMFs. The main differences to previous models involve gully formation during not only the deglaciation phase, but also during interglacials by dense shelf water cascading, and a specific timing for the occurrence of slope failures (i.e., shortly after the deglaciation phase). High mean sedimentation rates during glacial maxima of up to 18 kg m−2 yr−1 likely allow excess pore pressure to develop in the water rich plumites and hemipelagic sediments deposited in the previous deglacial period, particularly where such plumites attain a significant thickness. The position of the submarine landslides in the stratigraphic record suggest that such excess pore pressure is not enough to trigger the slope failures and suggests that earthquakes related to isostatic rebound are likely involved in the final activation.

Vulnerability of megabenthic species to trawling in the Barents Sea

Abstract The development of ecosystem-based fisheries management over the last two decades has increased attention on the protection of vulnerable resources that are of little or no economic significance including bycatch of benthos in bottom trawling. Current knowledge on the response of benthic communities to the impact of trawling is still rudimentary. In the present study, we used data collected in the Barents Sea during 2011 to assess the vulnerability of benthic species to trawling, based on the risk of being caught or damaged by a bottom trawl. Using trait table analysis, we identified 23 “high-risk” benthic species, which include “large weight and upraised” taxa as “easily caught” by a bottom trawl. We further identified a “low-risk” category containing 245 taxa/species and a “medium-risk” category with 80 species. A clear decline in biomass was noted for all three categories when comparing trawled vs. untrawled areas. This suggests that trawling significantly affects the biomass of all species, but predominantly the “high-risk” taxa. Some Barents Sea regions were particularly susceptible to trawling due to the dominance of the “high-risk” species, including Geodia sponges in the southwestern Barents Sea, basket stars ( Gorgonocephalus ) in the northern Barents Sea, sea pen ( Umbellula encrinus ) on the shelf facing the Arctic Ocean, and sea cucumber ( Cucumaria frondosa ) in shallow southern areas. These findings can guide management decisions to meet targets set by the United Nations Convention of Biological Diversity and the OSPAR Commission (“Protecting and Conserving the North-East Atlantic and its Resources”). We specifically recommend management action in the southwestern and the northwestern Barents Sea and on the Arctic shelf facing the Arctic Ocean.

A lithosphere-scale structural model of the Barents Sea and Kara Sea region

Abstract. We introduce a regional 3-D structural model of the Barents Sea and Kara Sea region which is the first to combine information on the sediments and the crystalline crust as well as the configuration of the lithospheric mantle. Therefore, we have integrated all available geological and geophysical data, including interpreted seismic refraction and reflection data, seismological data, geological maps and previously published 3-D models into one consistent model. This model resolves four major megasequence boundaries (earliest Eocene, mid-Cretaceous, mid-Jurassic and mid-Permian) the top crystalline crust, the Moho and a newly calculated lithosphere–asthenosphere boundary (LAB). The thickness distributions of the corresponding main megasequences delineate five major subdomains (the northern Kara Sea, the southern Kara Sea, the eastern Barents Sea, the western Barents Sea and the oceanic domain comprising the Norwegian–Greenland Sea and the Eurasia Basin). Relating the subsidence histories of these subdomains to the structure of the deeper crust and lithosphere sheds new light on possible causative basin forming mechanisms that we discuss. The depth configuration of the newly calculated LAB and the seismic velocity configuration of the upper mantle correlate with the younger history of this region. The western Barents Sea is underlain by a thinned lithosphere (80 km) resulting from multiple Phanerozoic rifting phases and/or the opening of the NE Atlantic from Paleocene/Eocene times on. Notably, the northwestern Barents Sea and Svalbard are underlain by thinnest continental lithosphere (60 km) and a low-velocity/hot upper mantle that correlates spatially with a region where late Cenozoic uplift was strongest. As opposed to this, the eastern Barents Sea is underlain by a thicker lithosphere (~ 110–150 km) and a high-velocity/density anomaly in the lithospheric mantle. This anomaly, in turn, correlates with an area where only little late Cenozoic uplift/erosion was observed.