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The HYCOM-NORWECOM modeling system is used both for basic research and as a part of the forecasting system for the Arctic Marine Forecasting Centre through the MyOcean project. Here we present a revised version of this model. The present model, as well as the sensitivity simulations leading up to this version, has been compared to a dataset of in-situ measurements of nutrient and chlorophyll from the Norwegian Sea and the Atlantic sector of the Arctic Ocean. The revisions having most impact included adding diatoms to the diet of micro-zooplankton, increasing micro-zooplankton grazing rate and decreased silicate-to-nitrate ratio in diatoms. Model runs are performed both with a coarse- (~ 50km) and higher-resolution (~ 15 km) model configuration, both covering the North Atlantic and Arctic Ocean. While the new model formulation improves the results in both the coarse- and high-resolution model, the nutrient bias is smaller in the high-resolution model, probably as a result of the better resolution of the main processes and with that improved circulation. The final revised version delivers satisfactory results for all three nutrients as well as improved result for chlorophyll in terms of the annual cycle amplitude. However, for chlorophyll the correlation with in-situ data remains relatively low. Besides the large uncertainties associated with observational data this is possibly caused by the fact that constant C/N and Chl/N ratios are implemented in the model. [ABSTRACT FROM AUTHOR]

Accurate information about ocean surface currents is of high importance for many purposes. Traditional ways of measuring surface currents using instruments immersed in water are associated with various challenges, as well as high installation and maintenance costs. Algorithms and hardware used to measure surface currents based on marine X-band radar images have been steadily improved during the recent decades. Such systems can now provide the user with current measurements with high accuracy in local areas of interest and with no need for underwater equipment, both from fixed sites and from moving installations, such as vessels. The primary focus of the work presented in this paper is to examine the measurement accuracy of an X-band radar-based system. For this purpose, field trials have been arranged and data acquired from a fixed platform in the North Sea in November 2015 and December 2015 and from a research vessel in the Norwegian Sea and the Barents Sea in November 2016. Data are analyzed, measured time series are compared to reference measurements and tidal current models, and statistical estimates of the measurement accuracy are calculated. Root-mean-square measurement errors of 0.032 m/s and 9.1° for magnitude and direction, respectively, are estimated for the fixed installation. Correlation coefficients are 0.93 and 0.94 for east–west and north–south components, respectively. A pooled standard deviation of 0.059 m/s is estimated for the moving installation. [ABSTRACT FROM AUTHOR]

The paper presents description of the relief, open fracture system, and submarine slides west of the Spitsbergen Archipelago in the Vestnesa Ridge area based on the data collected during cruises of the R/V Akademik Nikolaj Strakhov. Data pertaining to seismicity, as well as gas flares, chimneys, and holes are given based on the published sources. Analysis of the full information suggests the development of conditions favorable for large submarine landslides west of the Spitsbergen Archipelago. [ABSTRACT FROM AUTHOR]

This paper is focused on the potential impact of planktivorous fish in shaping the life history of Calanus finmarchicus in the Norwegian Sea. It is suggested that seasonally migrating fish species influence the timing of spawning and descent, and hence the number of generations of C. finmarchicus annually, and that the presence of resident mesopelagic fish influences the selection of winter habitat. C. finmarchicus ascends from overwintering and starts spawning 1–2 months prior to the spring bloom, which is exploited by the developing copepodites. Mortality risks increase upon arrival of fish on their oceanic feeding migrations, which for herring is prior to the spring bloom. Spawning early in the season may therefore reduce parental risks of exposure to such predators. Late-stage copepodites are heavily exploited by seasonally migrating fish during summer, so representing a driving force for the seasonal descent of C. finmarchicus. Overwintering takes place below the main domain of mesopelagic fish. [ABSTRACT FROM PUBLISHER]

Surveys have been conducted in the Norwegian Sea to evaluate the existing human factors standards and their implementations on two different offshore supply vessels designs. The results are reported in two parts. This paper (Part I) covers the theoretical background and reports all the technical aspects of the research: noise, motion and slamming that includes measurements, analyses and evaluations. Noise level and motion were measured on board along the survey by means of sound level meter and accelerometer respectively. Data collections were conducted in two periods: summer and winter. Results of measurements were compared with the existing criteria and discrepancies are identified. It can be concluded that the existing human factors criteria are inadequate and less relevant to the actual experience on board and they are ineffective to induce comfort. Improvements and revisions are strongly recommended with respect to noise, motion and slamming criteria. An extended methodology to predict MII is also advised. The other paper (Part II) reports the human factors subjective evaluation performed by the seafarers along the survey where multivariate analyses were performed to reveal a human factors model in ship design and operations. [ABSTRACT FROM AUTHOR]

The Lofoten Basin of the Norwegian Sea is characterized by a local maximum of eddy kinetic energy and it is an important transit region for the warm and saline Atlantic waters on their way towards the Arctic Ocean. Eddies are generated by the Norwegian Atlantic Current and propagate anticlockwise around the center of the basin. In situ and satellite observations have discovered a rather small (with a radius of a few tens of km), but strong quasi-permanent anticyclonic vortex that resides in the center of the Lofoten Basin near 3°E, 69.8°N. The objective of this paper is to understand how and why the vortex is formed and to investigate what processes support its stability and drive its variability. To achieve this objective, we have conducted three high-resolution numerical experiments with the mean horizontal grid spacing of 18 km, 9 km, and 4 km. The Lofoten Vortex did not form in the 18-km experiment. The most realistic (compared to available observations) simulation of the vortex is provided by the 4-km experiment, which better reproduces eddy variability in the region. The experiments thus provide experimental evidence of the importance of eddies in the formation and stability of the vortex. We demonstrate how anticyclonic eddies, that are usually stronger and more numerous in the basin than cyclonic eddies, contribute to the intensification of the Lofoten Vortex. The Lofoten Vortex itself is not stationary and drifts cyclonically within the area bounded by approximately the 3250 m isobath. The analysis of the barotropic vorticity budget in the 4-km experiment shows that the advection of the relative vorticity gradient by eddies is the main mechanism that drives the variability of the Lofoten Vortex. The direct impact of wind/buoyancy forcing is found to be small to negligible. [ABSTRACT FROM AUTHOR]

Abstract: Large waves pose risks to ships, offshore structures, coastal infrastructure and ecosystems. This paper analyses 10 years of in-situ measurements of significant wave height (H s ) and maximum wave height (H max ) from the ocean weather ship Polarfront in the Norwegian Sea. During the period 2000 to 2009, surface elevation was recorded every 0.59s during sampling periods of 30min. The H max observations scale linearly with H s on average. A widely-used empirical Weibull distribution is found to estimate average values of H max /H s and H max better than a Rayleigh distribution, but tends to underestimate both for all but the smallest waves. In this paper we propose a modified Rayleigh distribution which compensates for the heterogeneity of the observed dataset: the distribution is fitted to the whole dataset and improves the estimate of the largest waves. Over the 10-year period, the Weibull distribution approximates the observed H s and H max well, and an exponential function can be used to predict the probability distribution function of the ratio H max /H s . However, the Weibull distribution tends to underestimate the occurrence of extremely large values of H s and H max . The persistence of H s and H max in winter is also examined. Wave fields with H s >12m and H max >16m do not last longer than 3h. Low-to-moderate wave heights that persist for more than 12h dominate the relationship of the wave field with the winter NAO index over 2000–2009. In contrast, the inter-annual variability of wave fields with H s >5.5m or H max >8.5m and wave fields persisting over ~2.5 days is not associated with the winter NAO index. [Copyright &y& Elsevier]

SUMMARY In this contribution, we present a model of microcontinent architecture within a system that involves a complex rifted margin setting and different phases of deformation and continental breakup. Our case study is the Jan Mayen Microcontinent (JMMC) located in the central part of the Norwegian-Greenland Sea. We have revised its basement and sedimentary geometries using modern and vintage seismic reflection profiles, and updated potential field data. The northern part of the JMMC consists of a ∼10-15 km thick continental crust body flanked by two major sedimentary basins. We propose that the microcontinent is divided into six distinct segments, characterized by different basement and sedimentary architectures. The shallow stratigraphy is well imaged and has been detailed. Three distinct sedimentary units have been defined together with pronounced reflectors (JA, Red, JO and F), related to erosional, magmatic, thermal or uplift events. The continent-ocean boundary has been revised together with the mapping of the distinct volcanic events that characterize the evolution of the microcontinent. A companion paper aims to further detail the interpretation of the JMMC structure presented here by constraining the conjugated mid-Norwegian and mid-East Greenland structures. [ABSTRACT FROM AUTHOR]

With the rapid development of information technology, natural disaster prevention is growing as a new research field dealing with surveillance systems. To forecast and prevent the damage caused by natural disasters, the development of systems to analyze natural disasters using remote sensing geographic information systems (GIS), and vision sensors has been receiving widespread interest over the last decade. This paper provides an up-to-date review of five different types of natural disasters and their corresponding warning systems using computer vision and pattern recognition techniques such as wildfire smoke and flame detection, water level detection for flood prevention, coastal zone monitoring, and landslide detection. Finally, we conclude with some thoughts about future research directions. [ABSTRACT FROM AUTHOR]

Place-based management is any management action having implications for a specified area. Place-based management is seen as a key component to practical implementation of ecosystem approach to management, with marine spatial planning (MSP) being the currently most promoted approach. In the present paper we address the challenges of place-based management at local, regional and global (oceanic) spatial scales using case studies from the Northeast Atlantic with examples from Norway. Both ecological, governance and management complexity increases with increasing geographic scale, with associated increases in uncertainty and thus increasing need for managing under the precautionary approach. A process where (ecologically) valuable and vulnerable areas are defined early on is essential to successful place-based management under the ecosystem approach. Integrating across sectors and achieving necessary cooperation between involved institutions and stakeholders is also necessary. [ABSTRACT FROM AUTHOR]

The early to mid-Holocene thermal optimum is a well-known feature in a wide variety of paleoclimate archives from the Northern Hemisphere. Reconstructed summer temperature anomalies from across northern Europe show a clear maximum around 6000 years before present (6 ka). For the marine realm, Holocene trends in sea-surface temperature reconstructions for the North Atlantic and Norwegian Sea do not exhibit a consistent pattern of early to mid-Holocene warmth. Sea-surface temperature records based on alkenones and diatoms generally show the existence of a warm early to mid-Holocene optimum. In contrast, several foraminifer and radiolarian based temperature records from the North Atlantic and Norwegian Sea show a cool mid-Holocene anomaly and a trend towards warmer temperatures in the late Holocene. In this paper, we revisit the foraminifer record from the Vøring Plateau in the Norwegian Sea. We also compare this record with published foraminifer based temperature reconstructions from the North Atlantic and with modelled (CCSM3) upper ocean temperatures. Model results indicate that while the seasonal summer warming of the sea-surface was stronger during the mid-Holocene, sub-surface depths experienced a cooling. This hydrographic setting can explain the discrepancies between the Holocene trends exhibited by phytoplankton and zooplankton based temperature proxy records. [ABSTRACT FROM AUTHOR]

Bathymetric patterns of macrofaunal species diversity are best documented in the western North Atlantic where diversity is a unimodal function of depth, peaking in the mid-bathyal zone and being depressed in the upper slope and abyss. There are few inter-basin studies of diversity-depth trends that are controlled for taxonomy, sampling gear, and diversity measures. In this paper, we compare gastropod diversity gradients in the North American Basin of the Atlantic to estimates of diversity in 9 other regions: the Norwegian Sea, West European Basin, Guiana Basin, Gambia Basin, Equatorial Mid-Atlantic, Brazil Basin, Angola Basin, Cape Basin and Argentine Basin. All samples were collected with epibenthic sleds, and diversity calculated by the Sanders-Hurlbert normalized expected number of species. While sampling in other regions is generally less complete than in the western North Atlantic, results indicate that a unimodal pattern is not universal. Diversity can increase, decrease or show no relationship with depth. The level of diversity also varies among basins relative to the western North Atlantic, being depressed in the Norwegian Sea, at bathyal depths in the eastern North Atlantic, and below an oxygen minimum zone in the Cape Basin, and generally elevated at tropical latitudes and in abyssal regions where food supply is high. Associations between gastropod diversity and the ecology and geology of basins suggest that productivity, oxygen concentration, hydrographic disturbance and evolutionary-historical processes may be implicated in shaping bathymetric diversity gradients, but specific causes are difficult to discern. Much more intensive sampling, analyses of other major taxa, and more detailed ecological data are necessary to understand deep-sea biogeography at within- and between-basin spatial scales. [ABSTRACT FROM AUTHOR]

Study of redfish migration by traditional tagging methods is difficult because captured redfish usually prove to be nonviable. The main purpose of the present paper is to determine movement patterns of the beaked redfish (Sebastes mentella) juveniles based on data from Russian and Norwegian scientific trawl surveys conducted during autumn and winter of 1982-1995. The Petersen method was applied to analyse size composition of the beaked redfish catches. The conclusion made from prior researches that the beaked redfish year classes of 1982 and 1988 were strong compared to their neighbouring ones was confirmed. On the assumption that 'peaks' in the length distributions of survey catches display strong year classes, the annual corresponding lengths were defined for the 1982 and 1988 year classes of beaked redfish at different ages (from 0 to 7 years). Subsequently, using the database from trawl surveys and knowing the length of the beaked redfish from strong year classes at different ages, the distribution of these year classes by year was mapped. Based on these maps, migration patterns of the beaked redfish juveniles in the Barents and Norwegian Seas were inferred. The present study shows that the duration of the period from spawning to nursery area for one year class of the beaked redfish takes at least 2 years (age 0-1). Seasonal movements within the nursery area seem to last for 3-4 (5) years when the redfish is 2-4 (5) years old. The beaked redfish of the Norwegian-Barents sea population start leaving the nursery areas at age 5-6. [ABSTRACT FROM AUTHOR]

This paper introduces a pickup and delivery problem encountered in servicing of offshore oil and gas platforms in the Norwegian Sea. A single vessel must perform pickups and deliveries at several offshore platforms. All delivery demands originate at a supply base and all pickup demands are also destined to the base. The vessel capacity may never be exceeded along its route. In addition, the amount of space available for loading and unloading operations is limited at each platform. The problem, called the Single Vehicle Pickup and Delivery Problem with Capacitated Customers consists of designing a least cost vehicle (vessel) route starting and ending at the depot (base), visiting each customer (platform), and such that there is always sufficient capacity in the vehicle and at the customer location to perform the pickup and delivery operations. This paper describes several construction heuristics as well as a tabu search algorithm. Computational results are presented. [ABSTRACT FROM AUTHOR]

Abstract: The topographic steering of the baroclinic western branch of the Norwegian Atlantic Current (NwAC) determines the extent of Atlantic Water and location of the Arctic Front in the Nordic Seas. In this paper the geographical spread of hydrographic measurements at the Ocean Weather Station M (OWSM, ) is utilized to create mean sections across the Vøring Plateau Escarpment in the Norwegian Sea. In concert with a theoretical framework involving the impact of low pressure systems on frontal jets over steep bathymetry, the behaviour of the front-current system at this location is described. It is shown that the halocline and thermocline are sloped from about 200m in the west and down to 400m in the east over 40km centred on the station, indicating that the western branch of the NwAC is located here. The horizontal gradients introduced by this slope are and 0.1 for salinity. The frontal slope is not seen to change its inclination on seasonal, multi-annual, nor decadal timescales, indicating that the dynamic control of this frontal slope does not change appreciably. Further supported by the theoretical framework it is shown that the subsurface part of this front and the associated western branch of the NwAC is strongly locked by topography along the Vøring Plateau also on short timescales. From large scale bathymetry it is also shown how this kind of frontal locking can be expected over most of the ridges and continental slopes in the Nordic Seas. [Copyright &y& Elsevier]

When a force is applied to the Earth's surface, there is an immediate elastic deformation, proportional to the stress. This paper reports the calculations of the elastic deflections caused by the unloading of the Late Weichselian ice sheets in Fennoscandia. The deflections caused by the unloading of the maximum Late Weichselian ice sheet are calculated to be 76 m in the central parts of the former glaciated area. This is less than 8% of the isostatic response in the same area. When taking into consideration that this displacement is gradually recovered as the Earth readjusts towards isostatic equilibrium, the elastic mechanism can be assumed to be of little importance for the overall postglacial uplift. Maximum elastic deflection in Fennoscandia is calculated to be a subsidence of 12 m in the central parts of the former glaciated area, and 4–5 m along the Norwegian coast, over the last 10,000 years. [ABSTRACT FROM AUTHOR]

Calanus finmarchicus is the dominant copepod species in the Norwegian Sea, where it plays a key role in the ecosystem by transferring energy from primary producers to higher trophic levels. This paper analyses a 17-year time series, 1996–2012, on C. finmarchicus collected within the Atlantic Water mass along the Svinøy transect in the southeastern Norwegian Sea. We use the spring abundance of adult as a proxy for the size of C. finmarchicus ’ overwintered population. The inter-annual trend in spring abundance of adult C. finmarchicus in the 200–0 m depth-stratum is assessed while accounting for spring population development to the adult stage represented by day of year for sampling, inter-annual changes in timing of population development, and spatial differences. For the most oceanic stations, a significant inter-annual trend in spring abundance of adult C. finmarchicus was revealed using generalized additive models (GAM). This trend primarily consists in an increase prior to year 2000 and a decrease between years 2000 and ca. 2011. For the stations closer to the coast, the identified inter-annual trend is a decrease during a longer period from the late 90s until ca. 2011. From 2000 to 2011, our estimates suggest a 50% decrease for the most oceanic stations, and as much as an 81% decrease for the stations closer to the coast. In addition the results suggest a consistent change in phenology over the years and the stations. The predicted spring peak of overwintered adult population abundance is suggested to become shorter by 3 days, and the predicted maximum of abundance to take place 4 days earlier over the 17 years of the time-series. The results highlight significant changes in intensity and timing of the overwintered population of a key zooplankton species in the Norwegian Sea that may have important implications on the scale of an entire ecosystem. [ABSTRACT FROM AUTHOR]

Surveys have been conducted in the Norwegian Sea to evaluate the adequacy of human factors criteria in ship design by taking two offshore supply vessels as the samples. Two reports are being published to present the results. Part 1 covers the theoretical background and reports the technical aspects of the research that include noise, motion and slamming. It is concluded that the existing human factors criteria are unjustifiable and need to be revised. This paper aims to discover important factors that are relevant to seafarers' conditions and performance at sea. Physical measurements were performed together with crew member's subjective evaluation of ship board conditions. Surveys were conducted in two periods: summer and winter. The environmental conditions such as significant wave height (Hs) and peak period (Tp) were recorded during the survey. Noise and motion were measured on the vessel. Sleep, sleep problems, seafarers' conditions and performance were evaluated by means of self-administered questionnaires. Interconnectivities between variables of interest were investigated using multivariate analysis and a structural model was developed. [ABSTRACT FROM AUTHOR]

Abstract: This paper analyses 10years of in-situ measurements of significant wave height (Hs ) and maximum wave height (H max) from the ocean weather ship Polarfront in the Norwegian Sea. The 30-minute Ship-Borne Wave Recorder measurements of H max and Hs are shown to be consistent with theoretical wave distributions. The linear regression between H max and Hs has a slope of 1.53. Neither Hs nor H max show a significant trend in the period 2000–2009. These data are combined with earlier observations. The long-term trend over the period 1980–2009 in annual Hs is 2.72±0.88cm/year. Mean Hs and H max are both correlated with the North Atlantic Oscillation (NAO) index during winter. The correlation with the NAO index is highest for the more frequently encountered (75th percentile) wave heights. The wave field variability associated with the NAO index is reconstructed using a 500-year NAO index record. Hs and H max are found to vary by up to 1.42m and 3.10m respectively over the 500-year period. Trends in all 30-year segments of the reconstructed wave field are lower than the trend in the observations during 1980–2009. The NAO index does not change significantly in 21st century projections from CMIP5 climate models under scenario RCP85, and thus no NAO-related changes are expected in the mean and extreme wave fields of the Norwegian Sea. [Copyright &y& Elsevier]

Abstract: A White Paper on a new integrated management plan for the Norwegian Sea was launched by the Norwegian government in May 2009. Following international guidelines for ecosystem-based management, the plan provides an overall framework for managing all human activities (mainly oil and gas industry, fishing, and shipping) in the area to ensure the continued production and function of the ecosystem. The plan is based on an assessment of the present and projected future impact of human activities and of the interactions between them, taking into account deficits in current knowledge of ecosystem state and dynamics. Areas of particular value in terms of biodiversity or biological production were identified. In each of these valuable areas, any access for substantial human activity is to be carefully managed. To monitor the overall development of the Norwegian Sea, a set of indicators with associated environmental quality objectives have been selected. The approach used builds upon experience gained from the first integrated Norwegian management plan for a marine area, the Barents Sea–Lofoten region, developed in 2002–2006. Work towards a Norwegian management plan for the North Sea, including Skagerrak, was initiated in 2009. [ABSTRACT FROM AUTHOR]

Abstract: As part of a project comparing the structure and function of four marine ecosystems off Norway and the United States, this paper examines the oceanographic responses to climate forcing, with emphasis on recent changes. The four Northern Hemisphere ecosystems include two in the Pacific Ocean (Bering Sea and Gulf of Alaska) and two in the Atlantic Ocean (Georges Bank/Gulf of Maine and the Barents/Norwegian Seas). Air temperatures, wind forcing and heat fluxes over the four regions are compared as well as ocean hydrography and sea-ice conditions where seasonal sea ice is found. The long-term interannual variability in air temperatures, winds and net heat fluxes show strong similarity between adjacent ecosystems and within subregions of an ecosystem, but no significant correlations between Pacific and Atlantic ecosystems and few across the Atlantic. In spite of the lack of correlation between climate forcing and ocean conditions between most of the ecosystems, recent years have seen record or near record highs in air and sea temperatures in all ecosystems. The apparent causes of the warming differ. In the Atlantic, they appear to be due to advection, while in the Pacific temperatures are more closely linked to air-sea heat exchanges. Advection is also responsible for the observed changes in salinity in the Atlantic ecosystems (generally increasing salinity in the Barents and Norwegian Seas and decreasing in the Gulf of Maine and Georges Bank) while salinity changes in the Gulf of Alaska are largely related to increased local runoff. [Copyright &y& Elsevier]

Abstract: The purpose of this paper is to investigate the influence of horizontal grid resolution in a physical model on an embedded primary production model. The area for the experiment was along the west coast of Norway, from 60° N to 70° N, an area of high mesoscale activity. The HYbrid Coordinate Ocean Model was coupled with the NORWegian ECOlogical Model system, and run in a nested system, consisting of three model grids with horizontal resolution of 50 km, 16 km and 4.5 km (hereafter: COARSE, MEDIUM and FINE) in the focus area. Two main results were obtained, first, the composition of the phytoplankton functional groups changed with increasing model grid resolution. In FINE, the diatoms produced a larger part (60%) of the total annual primary production than the flagellates, whereas in COARSE and MEDIUM, the primary production from the two phytoplankton groups was the same. This was explained by a higher transport of silicate into the euphotic layer in FINE compared to the other two. Second, the differences in the primary production first became large when the resolution of the model grid reached the Rossby radius of deformation. Whereas the total net primary production in MEDIUM only was 5% larger than in COARSE, the total net primary production in FINE was 20% higher than in COARSE. This was explained by the models ability to resolve mesoscale activity. [Copyright &y& Elsevier]

As part of the Lofote Cyclone experiment (Lofoten Zyklonen Experiment) 21 drift buoys were deployed in a 700 km × 400 km area of the Norwegian Sea situated to the west of the Lofote Islands. The buoys measured sea-level pressure (SLP), surface air temperature (SAT), and sea surface temperature (SST) at hourly intervals for a 6-month period from March to August 2005. This unique data set is used to validate the operational model analyses of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the German Weather Service [Deutscher Wetterdienst (DWD)]. Comparisons were performed in both time and space. Generally, biases are small and amount to 0.2 hPa for SLP and −0.2 K for SAT. Temporal correlations are higher than 0.99 for SLP and 0.93 for SAT. Spatial correlations as a measure of pattern coincidence are lower then for temporal correlations, but still amount to values higher than 0.97 for SLP and 0.76 for SAT on average. SST, which is externally prescribed and not a model variable, shows surprisingly large and persistent errors of up to 6 K for latitudes above 76°N. This points towards basic errors in the SST source for both models. Taking all comparisons (SLP, SAT, and SST) together, agreement is slightly worse for DWD than for ECMWF. [ABSTRACT FROM AUTHOR]

Occurrences of fossil marine diatom resting spore genus Liradiscus Greville are described from the middle Eocene to middle Miocene samples of Deep Sea Drilling Project Leg 38 Site 338 in the Norwegian Sea. The genus Liradiscus is characterized by a thick frustule sculptured by numerous veins. In this paper, five new taxa (L. cucurbitus, L. castaneus, L. castaneus vat. reticulatus, L. caepus and L. nimbus) are described, and their stratigraphical ranges are presented. These species are short-ranging and may be potentially useful biostratigraphic markers to improve resolution of diatom biostratigraphy of the Norwegian Sea. Liradiscus castaneus var. castaneus may be evolved from var. reticulatus in the middle part of the Zone NPD 2A (18.4-20.3 Ma). The geologic ranges of L. reticulatus and L. petasus in the Norwegian Sea (L. reticulatus: early Miocene, L. petasus: late early Oligocene to middle early Miocene) are differentiated from those in the North Pacific (L. reticulatus: middle late Miocene, L. petasus: early late Miocene), suggesting possible the regional environmental differences. [ABSTRACT FROM AUTHOR]

Abstract: Measurements of the inflow of Atlantic Water to the Norwegian Sea show that a narrow jet forms along the shelf slope in the Svinøy and Ormen Lange areas west of mid Norway. The main density stratification can be divided into the warm Atlantic Water located on top and the colder and fresher Norwegian Sea Water masses below. The relatively thin interface is located at approximately 500–600m depth. Eddies with periods between 20 and 80h are found to develop in the flow of the Atlantic Water. In this paper a three-dimensional -coordinate ocean model is used to study the formation of eddies in an idealised shelf area with a constant jet. Two numerical simulations are performed. The first simulation is barotropic, and the second is a two layer simulation with a barotropic jet. The numerical results show that eddies are generated by the inflowing jet in both simulations, but the eddies in the two layer simulation are weaker than in the barotropic simulation. The numerical results show that the length scale and the strength of the eddies depend on the stratification. For the barotropic case the growth rate agrees well with corresponding results from linear stability analysis. In the two layer simulation the jet loses the forced bell shape profile, the growth of the barotropic eddies is reduced, and an intensification occurs for the along shelf velocities in the interface. [Copyright &y& Elsevier]

Abstract: This paper describes a strategy for effective discrimination and provenance evaluation of sandstones transported by different sediment dispersal systems using an integrated programme of heavy mineral analysis, mineral chemistry and zircon age dating. Sandstones derived from different source regions are initially discriminated using provenance–sensitive heavy mineral parameters (ratios of abundances of stable, hydraulically equivalent minerals). Differences between the heavy mineral populations are reinforced by single-grain mineral chemical analysis, which also provides further information on the nature of the source terrains. Zircon age dating of representative samples places further constraints on the location of the source areas, by identifying the main crust-forming events. In addition, the validity of the mineralogical discrimination can be tested by the zircon age data. The value of this integrated approach is illustrated by a case study of deep marine Late Cretaceous–Paleocene sandstones in the Norwegian Sea. Potential sources of coarse clastic sediment lie both to the east, in mid-Norway, and the west, in East Greenland. Three main sand types (MN1, MN2 and MN3) have been identified, each of which has a unique combination of heavy mineral ratios (rutile/zircon, monazite/zircon, chrome spinel/zircon and apatite/tourmaline) and mineral chemistry (garnet and tourmaline). Sand type MN1 has a simple zircon age spectrum, with a large Early–Middle Proterozoic group and a small Early Paleozoic group, indicating derivation from northern mid-Norway. Sand type MN2 has a complex age structure including Archaean and early Proterozoic zircons. It can be divided into two subtypes, MN2a and MN2b, and can be ascribed to a source in East Greenland. Sand type MN3 has a simple age structure dominated by Middle Proterozoic zircons, and it was sourced from southern mid-Norway. Since reservoir presence is a major area of uncertainty in the deep water Norwegian Sea, the use of heavy mineral, mineral chemical and zircon age data to discriminate sandstones of eastern and western origin is crucial to hydrocarbon exploration of the area. [Copyright &y& Elsevier]

We validate a new high-resolution (3 km) numerical mesoscale weather simulation for offshore wind power purposes for the time period 2004-2016 for the North Sea and the Norwegian Sea. The 3 km Norwegian reanalysis (NORA3) is a dynamically downscaled data set, forced with state-of-the-art atmospheric reanalysis as boundary conditions. We conduct an in-depth validation of the simulated wind climatology towards the observed wind climatology to determine whether NORA3 can serve as a wind resource data set in the planning phase of future offshore wind power installations. We place special emphasis on evaluating offshore wind-power-related metrics and the impact of simulated wind speed deviations on the estimated wind power and the related variability. We conclude that the NORA3 data are well suited for wind power estimates but give slightly conservative estimates of the offshore wind metrics. In other words, wind speeds in NORA3 are typically 5% (0.5ms-1) lower than observed wind speeds, giving an underestimation of offshore wind power of 10 %-20% (equivalent to an underestimation of 3 percentage points in the capacity factor) for a selected turbine type and hub height. The model is biased towards lower wind power estimates due to overestimation of the wind speed events below typical wind speed limits of rated wind power (u < 11-13ms-1) and underestimation of high-wind-speed events (u > 11-13ms-1). The hourly wind speed and wind power variability are slightly underestimated in NORA3. However, the number of hours with zero power production caused by the wind conditions (around 12% of the time) is well captured, while the duration of each of these events is slightly overestimated, leading to 25-year return values for zero-power duration being too high for the majority of the sites. The model performs well in capturing spatial co-variability in hourly wind power production, with only small deviations in the spatial correlation coefficients among the sites. We estimate the observation-based decorrelation length to be 425.3 km, whereas the model-based length is 19% longer. [ABSTRACT FROM AUTHOR]

We interpret Cretaceous sedimentation in the Norwegian Sea, following the Jurassic rift episode and until the onset of Campanian rifting, to represent a post-rift thermal subsidence stage (ca. 140–80 Ma), i.e. a setting characterized by tectonic quiescence. This contrasts with previously published models, which emphasize the importance of tectonism in the Cretaceous evolution. The proposed model includes a significant tectonic relief and water depths in the Norwegian Sea, following Jurassic crustal stretching and associated tilting of major fault-blocks. Variation in sediment rate, type of sediment and thickness distribution, described to be indicative of Cretaceous tectonic events, are, in this paper, interpreted to reflect variations during infilling of the inherited Jurassic rift architecture, as well as responses to post-rift thermal subsidence, sediment loading and differential compaction during burial. The near perfect onlap of Cretaceous horizons along pre-existing fault scarps, later deformed by compaction, demonstrates the progressive post-rift sedimentary infill of deep-water basins by sedimentary bodies with a variety of depositional profiles. Cretaceous sediments in the Møre and Vøring Basins reached thickness (after compaction) of some 7–9 km, and this load produced a downward flexure of the lithosphere. Westward tilting of the Mid-Norway continental shelf area during the Cretaceous and onlap of post-rift sediments along basin margins, where the Cretaceous succession is relatively thin, demonstrate this. The infilling package of Lower Cretaceous sediments, which represents the immediate post-rift deposits, assume the wedge-shaped geometry of the remnant Jurassic rift topography and may display divergent reflector configurations induced by compaction. Early Cretaceous sedimentation rates, in major parts of the Norwegian Sea, are interpreted to be lower than the subsidence rate and accordingly Late Jurassic fault scarps remained significant features on the basin floor for a considerable time. The Early to Late Cretaceous transition saw a remarkable increase in sedimentation rate; the Cenomanian–Santonian rate was four-fold that of the average rate during the Early Cretaceous. The increased sediment supply outpaced subsidence and the topographic relief was levelled in the Santonian causing the different depocentres of Early Cretaceous time to merge into a wider depocentre. We interpret this as a mature stage of the post-rift development, when thermal equilibrium was obtained. The period of tectonic quiescence was terminated by a new rift episode, which was initiated in the Early Campanian and culminated with the final opening of the North Atlantic 55 Ma ago. [Copyright &y& Elsevier]

Mortality rates in the early life-history stages of fishes are generally high yet identifying the causes remain unclear. Faltering recruitment rates of Atlantic herring (Clupea harengus) in the Norwegian Sea indicate a need to identify which mortality factors influence larval herring survival. Previous research suggests that increased predation pressure by Atlantic mackerel (Scomber scombrus) may contribute to the disconnect between spawning stock biomass and recruitment. To quantify the contribution of predation pressure by Atlantic mackerel to herring larval mortality, two research cruises were conducted within a probable "hot spot" (67–72° N) for intensified mackerel predation based on particle drift simulations. Mackerel stomach contents were analysed for herring larvae content using droplet digital polymerase chain reaction (ddPCR) with a quantitative molecular detection assay specific for herring. The ddPCR results demonstrate clear predation by mackerel on herring larvae and also suggest that the alternative use of visual examination may give misleading results. Our results show that mackerel should be considered a potentially important predator on herring larvae. The quantitative molecular assay presented here shows great promise as an efficient and specific tool to correctly identify and quantify predation pressure on early life-history stages of fishes. [ABSTRACT FROM AUTHOR]

Along‐track altimeter and sea surface temperature satellite observations and ARGO in situ measurements of temperature and salinity are used to investigate the heat transport by mean currents and eddies in the ocean region adjacent to the Greenland‐Scotland Ridge from 2003 to 2008. Our results show that the heat advection by the mean flow in the surface layer is zonally asymmetric with a higher magnitude in the western part of the region. This asymmetry is associated with an excessive mean heat advection in an area adjacent to the Denmark Strait. The advection of heat is high and positive south of the strait and low and negative north of it. We suggest that this heat advection impacts the local budgets of heat and potential energy of the mean flow in the surface layer. The mesoscale eddies are identified and their characteristics, including radius, sea level anomaly, lifetime, and paths of propagation, are assessed by using along‐track altimeter data. About 70% of the eddies are observed in the eastern part of the studied region. The eddy‐induced heat transport by warm mesoscale eddies in the Norwegian Sea was found to be about 2.5 times larger than the mean advection by the Norwegian Atlantic Current. We suggest, therefore, that the eddy‐induced transport is a dominant factor in the heat budget of this region. Plain Language Summary: The ocean circulation and transport over the Greenland Scotland Ridge are of crucial significance for maintaining the heat transport between the Arctic and North Atlantic Oceans. Warm and salty waters of Atlantic Ocean flow through the eastern part of the Greenland‐Scotland Ridge. The return flow into the Atlantic Ocean includes cold and fresh surface and intermediate Arctic waters. The contrast in the characteristics of the inflow and outflow through the Greenland‐Scotland Ridge implies a large net heat into the Nordic Seas and the Arctic. In this article, we study the horizontal mean and eddy heat advection in the ocean region adjacent to the Greenland‐Scotland Ridge. The focus of our work is on the rather on the local impact of the heat transport on the heat content of the ocean region over the ridge. We use ocean observations to estimate and study this transport. Key Points: Mean and eddy‐induced heat advection in the ocean region adjacent to the Greenland‐Scotland Ridge are derived from satellite and ARGO dataThe advective heat flux in the surface layer was found to have the largest magnitude in the area adjacent to the Denmark StraitThe estimate of the heat transport by warm eddies in the Norwegian Sea is about 2.5 times larger than the mean advection of heat [ABSTRACT FROM AUTHOR]

To better understand fin whale vocalization behaviour in the Norwegian and Barents Seas, a large-aperture densely sampled coherent hydrophone array was deployed in late winter 2014 to monitor their vocalizations instantaneously over wide areas via passive ocean acoustic waveguide remote sensing (POAWRS). Here, we (i) provide a time-frequency characterization for different call types observed (20 Hz pulses, 130 Hz upsweeps, 30–100 Hz downsweep chirps, and 18–19 Hz backbeats); (ii) compare their relative abundances in three different coastal regions off Alesund, Lofoten, and Northern Finnmark; (iii) estimate the temporal and spatial distributions; (iv) source level distributions; and (v) probability of detection (PoD) regions for the more abundant 20 Hz pulse and 130 Hz upsweep call types. The fin whale vocalizations received over the diel cycle (24 h) were significantly more abundant by a factor of roughly seven off Northern Finnmark than the other two regions, associated with fish feeding activities. The source levels are estimated to be 190.5 ± 7.4 dB for the fin whale 20 Hz pulses and 170.3 ± 5.2 dB for the 130 Hz upsweeps. We find that fin whales are capable of producing each vocalization type either independently or simultaneously with other types, and the 20 Hz sound production in the fin whales involves a mechanism that generates a significantly less-intense second-order harmonic of the fundamental. [ABSTRACT FROM AUTHOR]

The biogeochemistry from a global climate model (Norwegian Earth System Model) has been compared with results from a regional model (NORWECOM.E2E), where the regional model is forced by downscaled physics from the global model. The study should both be regarded as a direct comparison between a regional and its driving global model to investigate at what extent a global climate model can be used for regional studies, and a study of the future climate change in the Nordic and Barents Seas. The study concludes that the global and regional model compare well on trends, but many details are lost when a coarse resolution global model is used to assess climate impact on regional scale. The main difference between the two models is the timing of the spring bloom, and a non-exhaustive nutrient consumption in the global model in summer. The global model has a cold (in summer) and saline bias compared with climatology. This is both due to poorly resolved physical processes and oversimplified ecosystem parameterization. Through the downscaling the regional model is to some extent able to alleviate the bias in the physical fields, and the timing of the spring bloom is close to observations. The summer nutrient minimum is one month early. There is no trend in future primary production in any of the models, and the trends in modelled pH and Ω Ar are also the same in both models. The largest discrepancy in the future projection is in the development of the CO2 uptake, where the regional suggests a slightly reduced uptake in the future. [ABSTRACT FROM AUTHOR]

The aim of the study was to increase knowledge regarding baseline biology of Arctic mussels (Mytilus spp.) in terms of lipid class content at different stages of reproductive development throughout the year. Lipid composition in the mantle and digestive glands were studied in mussels from the intertidal and subtidal zones of mussel beds located in the Norwegian Sea and the White Sea. Thin-layer chromatography was used to quantify phospholipids, triacylglycerols, sterols and their esters. The differences in climatic and hydrological conditions between the studied geographical locations of mussel beds were reflected not only in the timing and duration of the mussel’s reproductive stages, mainly active gametogenesis (stage II) and maturity (stage III), but also in the lipid composition of mussel mantle and digestive gland. The differences in environmental conditions between intertidal and subtidal zones of the studied mussel beds were also reflected in the lipid composition of mussels from both geographic locations, and determined the modifications of their lipid composition during the reproductive development. Although environmental conditions caused specificity in the distribution of the lipid composition in the mantle and digestive gland of Arctic Mytilus spp., the lipid composition variations that accompany the reproductive processes in bivalve mollusks were not affected. [ABSTRACT FROM AUTHOR]

Ocean microstructure, current, and hydrography observations from June 2016 are used to characterize the turbulence structure of the Lofoten Basin eddy (LBE), a long-lived anticyclone in the Norwegian Sea. The LBE had an azimuthal peak velocity of 0.8 m s−1 at 950-m depth and 22-km radial distance from its center and a core relative vorticity reaching −0.7f (f is the local Coriolis parameter). When contrasted to a reference station in a relatively quiescent part of the basin, the LBE was significantly turbulent between 750 and 2000 m, exceeding the dissipation rates ε in the reference station by up to two orders of magnitude. Dissipation rates were elevated particularly in the core and at the rim below the swirl velocity maximum, reaching 10−8 W kg−1. The sources of energy for the observed turbulence are the background shear (gradient Richardson number less than unity) and the subinertial energy trapped by the negative vorticity of the eddy. Idealized ray-tracing calculations show that the vertical and lateral changes in stratification, shear, and vorticity allow subinertial waves to be trapped within the LBE. Spectral analysis shows increased high-wavenumber clockwise-polarized shear variance in the core and rim regions, consistent with downward-propagating near-inertial waves (vertical wavelengths of order 100 m and energy levels 3 to 10 times the canonical open-ocean level). The energetic packets with a distinct downward energy propagation are typically accompanied with an increase in dissipation levels. Based on these summer observations, the time scale to drain the volume-integrated total energy of the LBE is 14 years. [ABSTRACT FROM AUTHOR]

The Last Millennium Reanalysis (LMR) employs a data assimilation approach to reconstruct climate fields from annually resolved proxy data over years 0-2000 CE. We use the LMR to examine Atlantic multidecadal variability (AMV) over the last 2 millennia and find several robust thermodynamic features associated with a positive Atlantic Multidecadal Oscillation (AMO) index that reveal a dynamically consistent pattern of variability: the Atlantic and most continents warm; sea ice thins over the Arctic and retreats over the Greenland, Iceland, and Norwegian seas; and equatorial precipitation shifts northward. The latter is consistent with anomalous southward energy transport mediated by the atmosphere. Net downward shortwave radiation increases at both the top of the atmosphere and the surface, indicating a decrease in planetary albedo, likely due to a decrease in low clouds. Heat is absorbed by the climate system and the oceans warm. Wavelet analysis of the AMO time series shows a reddening of the frequency spectrum on the 50- to 100-year timescale, but no evidence of a distinct multidecadal or centennial spectral peak. This latter result is insensitive to both the choice of prior model and the calibration dataset used in the data assimilation algorithm, suggesting that the lack of a distinct multidecadal spectral peak is a robust result. [ABSTRACT FROM AUTHOR]

For the first time, the concepts of the theory of helical vortices have been applied to the Lofoten vortex of the Norwegian Sea. The estimates for azimuthal and vertical velocities have been obtained from the Massachusetts Institute of Technology general circulation model (MITgcm) for 1992-2012. The columnar vortex model with helical vorticity lines and distributions has been adapted to Scully and Rayleigh vortices. It has been shown that the vortex parameters can be determined simply from mass balance equations. The parameters of the helical vortex simulating the structure of the Lofoten vortex have been found and the radial distributions of azimuthal and vertical velocity components have been constructed. The resulting data can be interesting for an analysis of the three-dimensional structure of mesoscale vortices in the ocean. [ABSTRACT FROM AUTHOR]

ABSTRACT A depositional sequence bounded by upper and lower erosion surfaces covering a 35-km × 20-km area within the northern embayment of the Early Pleistocene Central North Sea is dated close to the Jaramillo Normal sub-chron at approximately 1.0-1.1 Ma. The basal surface cuts shallow marine clays of the upper Nordland Group and is characterized by furrow incisions, mega-scale glacial lineation textures and bedforms that are all orientated NNW-SSE. The sequence comprises a suite of distinctive bedforms, including a chaotic deposit up to 60 m thick, a series of moulded and lineated depositional bodies and some more complex bedforms, with lithologies shown by petrophysical data to be dominated by overconsolidated clays and thin sand layers. This sequence is considered to represent deposition from the advance and subsequent decay of a marine-terminating ice-sheet. The upper surface of the sequence coincides with the so-called 'Crenulate Reflection' and is characterized by a fluvial channel system, representing final retreat of the ice-sheet, which was followed by shallow marine conditions and deposition of the Aberdeen Ground Formation. It is considered that the Aberdeen Ground Formation comprises at least two main sequences spanning the Early to Middle Pleistocene. [ABSTRACT FROM AUTHOR]

North Atlantic average sea surface temperatures have increased since the 1970s, and how the marine environment is responding to the temperature increase is of considerable interest. Several zooplankton taxa have been reported to have undergone shifts in distributional ranges driven by climate change. We present a study on interannual variability of adult Pseudocalanus spp. from the Norwegian Sea and two fjords of Spitsbergen, collected between 2003 and 2009. Species are identified based on the combination of morphological features and molecular methods (mitochondrial cytochrome oxidase I gene, COI and nuclear internal transcribed spacer 1, ITS 1 sequences). Based on multivariate statistics, our observations suggest that Pseudocalanus species differ markedly in their environmental preferences; three species appear to be oceanic: P. elongatus is associated with relatively high temperatures and shares domain with P. minutus, P. moultoni tolerates a wide range of temperatures and is widely distributed, while P. acuspes is a coastal/shelf species that is strongly associated with cold and less saline waters. We conclude that with a climate change and increasing sea water temperatures, P. elongatus is likely to shift its distribution northward; for P. acuspes, it may result in smaller populations in the future; while P. minutus and P. moultoni may not be affected. [ABSTRACT FROM AUTHOR]

The Norwegian spring-spawning (NSS) herring (Clupea harengus), blue whiting (Micromesistius poutassou) and Northeast Atlantic (NEA) mackerel (Scomber scombrus) are extremely abundant pelagic planktivores that feed in the Norwegian Sea (NS) during spring and summer. This study investigated the feeding ecology and diet composition of these commercially important fish stocks on the basis of biological data, including an extensive set of stomach samples in combination with hydrographical data, zooplankton samples and acoustic abundance data from 12 stock monitoring surveys carried out in 2005–2010. Mackerel were absent during the spring, but had generally high feeding overlap with herring in the summer, with a diet mainly based on calanoid copepods, especially Calanus finmarchicus, as well as a similar diet width. Stomach fullness in herring diminished from spring to summer and feeding incidence was lower than that of mackerel in summer. However, stomach fullness did not differ between the two species, indicating that herring maintain an equally efficient pattern of feeding as mackerel in summer, but on a diet that is less dominated by copepods and is more reliant on larger prey. Blue whiting tended to have a low dietary overlap with mackerel and herring, with larger prey such as euphausiids and amphipods dominating, and stomach fullness and feeding incidence increasing with length. For all the species, feeding incidence increased with decreasing temperature, and for mackerel so did stomach fullness, indicating that feeding activity is highest in areas associated with colder water masses. Significant annual effects on diet composition and feeding-related variables suggested that the three species are able to adapt to different food and environmental conditions. These annual effects are likely to have an important impact on the predation pressure on different plankton groups and the carrying capacity of individual systems, and emphasise the importance of regular monitoring of pelagic fish diets. [ABSTRACT FROM AUTHOR]

There are few in situ observations of deep-sea macrofauna, due to the remoteness of this ecosystem. Visual surveys conducted for marine management by MAREANO, (marine area database for Norwegian waters) and the petroleum industry (by SERPENTS, scientific and environmental remotely operated vehicle partnership using existing industrial technology) have provided unique material of visual information from large areas in the Norwegian Sea. The distribution, density and behaviour of the deep-sea amphipodNeohela monstrosa(Boeck, 1861) is described based on videos and samples from the Norwegian Sea. This amphipod is common on mud bottoms at 200–2181 m depth in the area. Dense communities were found in stands of the arctic sea penUmbellula encrinusat more than 1000 m depth where temperatures were below 0° C. The mean density ofN. monstrosaobserved for larger areas was 4/100 m2but densities of 15–36 individuals per m2were found in local patches. It is domicolous which is characteristic of the superfamily Corophiida and digs burrows in soft muddy bottoms primarily by using large shovel-like gnathopods to scoop the sediment out. The amphipod was observed pushing and rolling sediment balls out of its burrow, which were probably held together with amphipod silk. It digs out an upper 3 to 4 cm wide burrow with a horizontal side burrow a couple of centimetres down.Neohela monstrosaappears to feeds on newly settled detritus that it collects from the surface sediment through the use of its long antennae while the burrow is mainly used for protection against predators such as demersal fish. Newly released juveniles are probably kept in the burrow for protection. Based on the local high density ofN. monstrosatogether with its habit of making long burrows, we suggest that there is significant bioturbation associated with the presence ofN. monstrosain deep sedimentary habitats of the Norwegian Sea, which likely provides an important ecosystem function. [ABSTRACT FROM AUTHOR]

Foraminiferal assemblages from a red sediment interval of the uppermost Santonian-middle Campanian Nise Formation, offshore Norway were examined for taxonomy and their paleoenvironmental implications using morphogroup analysis. The relatively highly diversified assemblages are composed only of deep-water agglutinated forms, and in total 61 taxa were identified. The taxonomic and morphogroup composition of the assemblages resemble both the slope flysch-type biofacies in containing robust tubular forms and rzehakinids, and assemblages described from Cretaceous Oceanic Red Beds (CORBs) in the North Atlantic and the Carpathians in the high abundance of infaunal forms in supposedly environments with low flux of organic matter. The intermediate nature of the assemblages in the red sediment interval is probably related to the shallower bathyal depositional settings and higher flux of organic matter due to the proximity to land in a narrow seaway inferred frommorphogroup analysis than abyssal settings of other CORBs. The foraminifera from the red sediment may be regarded as the background deep-water assemblage which reflectswell-oxygenated and low-nutrient environments only with small terrigenous input in the Norwegian Sea which was tectonically active during the Cretaceous. [ABSTRACT FROM AUTHOR]

The distributions of the coccolithophore species Emiliania huxleyi and Coccolithus pelagicus (heterococcolith-bearing phase) in the northern North Atlantic were investigated along two zonal transects crossing Fram Strait and the Norwegian–Iceland Sea, respectively, each conducted during both July 2011 and September–October 2007. Remote-sensing images as well as CTD and ARGO profiles were used to constrain the physico-chemical state of the surface water and surface mixed layer at the time of sampling. Strong seasonal differences in bulk coccolithophore standing stocks characterized the northern and southern transects, where the maximum values of 53×10 3 cells/l (fall) and 70×10 3 cells/l (summer), respectively, were essentially explained by E. huxleyi . This pattern confirms previous findings of a summer to fall northwestward shift in peak coccolithophore cell densities within the Nordic Seas. While depicting an overall zonal shift in high cell densities between the summer (Norwegian Sea) and fall (northern Iceland Sea) conditions, the southern transects were additionally characterized by local peak coccolithophore concentrations associated with a geographically and temporally restricted convective process (Lofoten Gyre, summer), as well as an island mass effect (in the vicinity of Jan Mayen Island, fall). Maximum coccolithophore abundances within Fram Strait were found during both seasons close to the western frontal zone (Polar and Arctic Fronts) an area of strong density gradients where physical and chemical properties of the surface mixed layer are prone to enhance phytoplankton biomass and productivity. Here, changes in species dominance from E. huxleyi in summer, to C. pelagicus in fall, were related to the strengthened influence during summer, of surface AW, as well as to high July solar irradiance, within an area usually characterized by C. pelagicus -dominated low density populations. [ABSTRACT FROM AUTHOR]

The Lofoten Basin is the largest reservoir of ocean heat in the Nordic Seas. A particular feature of the basin is ‘the Lofoten Vortex’, a most anomalous mesoscale structure in the Nordic Seas. The vortex resides in one of the major winter convection sites in the Norwegian Sea, and is likely to influence the dense water formation of the region. Here, we document this quasi-permanent anticyclonic vortex using hydrographic and satellite observations. The vortex’ uniqueness in the Nordic Seas, its surface characteristics on seasonal, inter-annual, and climatological time-scales, are examined together with the main forcing mechanisms acting on it. The influence of the vortex on the hydrography of the Lofoten Basin is also shown. We show that the Atlantic Water in the Nordic Seas penetrate the deepest inside the Lofoten Vortex, and confirm the persistent existence of the vortex in the deepest part of the Lofoten Basin, its dominant cyclonic drift and reveal seasonality in its eddy intensity with maximum during late winter and minimum during late autumn. Eddy merging processes are studied in detail, and mergers by eddies from the slope current are found to provide anticyclonic vorticity to the Lofoten Vortex. [ABSTRACT FROM AUTHOR]

We present evidence of mitochondrial and nuclear introgression from the Atlantic herring Clupea harengus into the Pacific herring C. pallasii in northern European seas, where the two species have come into secondary contact following the post-glacial trans-Arctic invasion of Pacific herring to the Atlantic realm. Although the breeding areas of the two species are thought to be separate, 7 % of the resident Pacific herring in samples from the White Sea were found to possess Atlantic herring mitochondria. The percentage was even higher (21 %) in the local Balsfjord stock of the Norwegian Sea, whereas it was nil in Pechora Sea samples. Similar or somewhat lower levels of genomic admixture were estimated from four diagnostic or nearly diagnostic nuclear allozyme loci. The absences of inter-locus and cytonuclear disequilibria, together with the patterns of mtDNA haplotype diversity, suggest recurrent backcrossing and hybridization over a long period in the post-glacial time frame. From a reassessment of published allozyme data, a hypothesis is presented that the patterns of intra-species geographical variation previously recorded in North European herrings may largely reflect varying levels of introgression. The study presents new information on the processes that affect the genetic structure of one of the most abundant fishes of the northern seas. It also adds to the knowledge on the occurrence of inter-species gene flow in marine fishes and on the consequences of trans-Arctic biotic invasions in general. [ABSTRACT FROM AUTHOR]

To develop a 14-winter (October-April; 1999-2013) climatic description of polar low (PL) occurrence for the Nordic Seas, systems have been tracked using images acquired from the Very High Resolution Radiometer (AVHRR). Also, the dominant PL characteristics - their temporal and spatial distributions, size, lifespan, distance travelled, speed of propagation and directions - have been determined. On average, 14 PL events occur per winter but there is strong inter-annual and intra-seasonal variability. Although systems may form and travel over the whole Nordic Seas, their genesis is enhanced in areas characterised by warm oceanic currents. At the start of the season (October-November), systems mainly form over the Greenland and Norwegian Seas, but further into winter they form increasingly over the Barents Sea. In connection with recent low-ice winters, new areas of PL formation are evident, particularly to the west of Spitsbergen and in the Barents Sea. PL speeds of propagation range between 5 and 13 m/s but are observed to be highly variable among cases and even during the lifespan of individual PLs. To a considerable extent, the direction of movement is controlled by the large-scale flow in the lowest atmospheric layers, but we also observed cyclonic co-rotation of some pairs of PLs due to their influence on the ambient flow. Although these generally move southward or southeastward, a substantial number of PLs have westward and even northward tracks. PLs in the western part of the region average larger than their eastern counterparts. This study also highlights that PLs characteristics and tracks differ according to weather regimes. [ABSTRACT FROM AUTHOR]

Short-lived halocarbons were measured in Arctic sea–ice brine, seawater and air above the Greenland and Norwegian seas (~81°N, 2–5°E) in mid-summer, from a melting ice floe at the edge of the ice pack. In the ice floe, concentrations of C 2 H 5 I, 2-C 3 H 7 I and CH 2 Br 2 showed significant enhancement in the sea ice brine, of average factors of 1.7, 1.4 and 2.5 times respectively, compared to the water underneath and after normalising to brine volume. Concentrations of mono-iodocarbons in air are the highest ever reported, and our calculations suggest increased fluxes of halocarbons to the atmosphere may result from their sea–ice enhancement. Some halocarbons were also measured in ice of the sub-Arctic in Hudson Bay (~55°N, 77°W) in early spring, ice that was thicker, colder and less porous than the Arctic ice in summer, and in which the halocarbons were concentrated to values over 10 times larger than in the Arctic ice when normalised to brine volume. Concentrations in the Arctic ice were similar to those in Antarctic sea ice that was similarly warm and porous. As climate warms and Arctic sea ice becomes more like that of the Antarctic, our results lead us to expect the production of iodocarbons and so of reactive iodine gases to increase. [ABSTRACT FROM AUTHOR]

The Norwegian Sea is a migration and feeding ground for fin whales ( Balaenoptera physalus) and humpback whales ( Megaptera novaeangliae) in summer. During the last decade, significant structural changes in the prey community, including northerly expansion and movement in the distribution of pelagic fish species, have been reported from this ecosystem. However, little information on whale feeding ecology exists in the Norwegian Sea and surrounding waters. A total of 59 fin whales and 48 humpback whales were sighted during 864 h of observation over an observation distance of about 8200 nmi (15,200 km) in the Norwegian Sea from 15 July to 6 August 2006 and 2007. The fin whale group size, as mean (± SD), varied between one and five individuals (2.1 ± 1.2 ind.) and humpback whale group size varied between one and six individuals (2.5 ± 1.7 ind.). Fin- and humpback whales were observed mainly in the northern part of the study area, and were only found correlated with the presence of macro-zooplankton in cold Arctic water. Humpback whales were not correlated with the occurrence of adult Norwegian spring-spawning herring ( Clupea harengus) except for the northernmost areas. Despite changes in the whale prey communities in the Norwegian Sea, no apparent changes in fin- or humpback whale distribution pattern could be found in our study compared to their observed summer distribution 10-15 years ago. [ABSTRACT FROM AUTHOR]

A method for estimating return values from ensembles of forecasts at advanced lead times is presented. Return values of significant wave height in the northeast Atlantic, the Norwegian Sea, and the North Sea are computed from archived +240-h forecasts of the ECMWF Ensemble Prediction System (EPS) from 1999 to 2009. Three assumptions are made: First, each forecast is representative of a 6-h interval and collectively the dataset is then comparable to a time period of 226 years. Second, the model climate matches the observed distribution, which is confirmed by comparing with buoy data. Third, the ensemble members are sufficiently uncorrelated to be considered independent realizations of the model climate. Anomaly correlations of 0.20 are found, but peak events (> P97) are entirely uncorrelated. By comparing return values from individual members with return values of subsamples of the dataset it is also found that the estimates follow the same distribution and appear unaffected by correlations in the ensemble. The annual mean and variance over the 11-yr archived period exhibit no significant departures from stationarity compared with a recent reforecast; that is, there is no spurious trend because of model upgrades. The EPS yields significantly higher return values than the 40-yr ECMWF Re-Analysis (ERA-40) and ECMWF Interim Re-Analysis (ERA-Interim) and is in good agreement with the high-resolution 10-km Norwegian Reanalyses (NORA10) hindcast, except in the lee of unresolved islands where EPS overestimates and in enclosed seas where it has low bias. Confidence intervals are half the width of those found for ERA-Interim because of the magnitude of the dataset. [ABSTRACT FROM AUTHOR]

The recently erected amphipod genusExitomelita(Tandberg et al., 2012) has so far been found only associated with the deep-water hydrothermal vent field “Loki's Castle” in the Norwegian-Greenland Sea. There it was found on the black smoker chimney walls as well as within fields of the tubewormSclerolinum contortumin sulphide- and methane-rich sediments surrounding the vent field. A new species has now been found in a large wood fall of pine at 2800 m depth close to this vent field. This group of amphipods is apparently confined to reduced habitats, and our data support the theory that the vent fauna in this area is closely related to fauna found on cold seeps and wood falls in the northernmost Atlantic and Arctic Oceans. Here we present morphological and molecular data and a short discussion of the habitat of the new species, in addition to a comparison with the previously described species ofExitomelita.http://www.zoobank.org/urn:lsid:zoobank.org:pub:2B0B3CC2-AB6A-4006-83BB-182280CB22B8 [ABSTRACT FROM PUBLISHER]