Northeast Atlantic Region Research Articles

The remarkable parallels between the North East Atlantic and Arctic regions

Geological understanding of the NE Atlantic and Arctic regions has increased greatly over the last two decades, revealing remarkable similarities. Continental extension in both regions onset during pausing or cessation of adjacent orogenies – the Verkhoyansk-Chukotka and Alpine orogenies – which relaxed compressional stresses and permitted extension. Severe extension accompanied by high-volume magmatism did not onset abruptly but was the culmination of long-term, regional tectonic and magmatic unrest. It was complex and piecemeal, with extension and volcanism occurring along multiple axes simultaneously, a process still ongoing in Iceland today. Large Igneous Province emplacement did not drive breakup but occurred as a consequence of continental extension. The High Arctic Large Igneous Province did not progress to breakup. As a result, much of the Arctic Ocean is floored by hyper-extended continental crust overlain by seaward-dipping reflectors. This crust resembles the passive margins of the NE Atlantic. The Alpha-Mendeleev Rise in the Arctic Ocean is a double-sided passive margin underlain by hyper-extended continental crust draped with seaward-dipping reflectors. A similar structure has been proposed for the Greenland-Iceland-Faroe Ridge. If correct, present-day volcanism in Iceland is building SDRs today. Up to ∼50% of the NE Atlantic Ocean oceanward of the continental shelves is likely underlain by at least some continental crust. For the Arctic Ocean this figure is ∼80%. Similar structures are found elsewhere, including the Madagascar Channel, the NW Indian Ocean, and the South Atlantic. These new ideas suggest promising directions of future study including assessing the true extent of continental crust in the oceans globally.

Climate Change and Extreme Events in Northeast Atlantic and Azores Islands Region

In small island regions, the influence of climate change assumes particular relevance. In the Azores archipelago, made up of nine islands, the geographical circumstances, oceanic condition, territorial dispersion, land use model and other physiographic constraints reinforce and enhance the vulnerability of the islands to changes in current weather patterns. Coupled Model Intercomparison Phase 6 (CMIP6) projections are used for the northeast Atlantic region to evaluate daily extreme climate events in large scale for the Azores region. Results shows changes in the annual maximum number of consecutive dry days, the annual number of wet days, and especially in the annual number of tropical nights. Despite limitations due to the lack of spatial detail, the large-scale framework suggests changes that may be enhanced by topography, particularly with respect to precipitation. The conclusions point to the need to establish standard rules in the processes of design, reviewing and/or amending territorial management instruments at the municipal scale in the Autonomous Region of the Azores, with the goal of adapting to a different climate from the recent past.

Origin of paired extension-compression during rotational rifting: An early Paleogene example from the northeast Atlantic region and its implications

Abstract The formation of paired extension-compression (PEC) postulated by rotational kinematics of rift propagation is demonstrated by analogue models but rarely observed in nature. In our study of the early Paleogene continental rift in the northeast Atlantic, a PEC is proposed based on the northeastward propagation and the coeval compression at the rift tip. The propagation is deduced from tectono-magmatic trends, including along-axis development of magmatism, and migration of tectonic faulting inward and toward the rift tip. Where this propagation terminated, we documented coeval extension and compression in the form of a horst-and-graben system (H&G) and V-shaped anticline (VA), respectively. Given their structural characteristics and spatiotemporal relationships with the rift, their origin is best illustrated by a three-stage model: (1) Rifting initiated at the site of mantle upwelling and propagated northeastward in the Paleocene. (2) The rift tip was stalled by an elevated mafic-ultramafic body at the Barents Shelf, which led to forward projection of the rift’s driving force to create the H&G and the VA (PEC), dissipating the along-axis force component. (3) Domination of axis-perpendicular components then promoted orthogonal extension and sheared margin development. Our study suggests that PEC has a crucial role in both termination of propagation and rift-mode conversion.

Winter Precipitation Responses to Projected Arctic Sea Ice Loss and Global Ocean Warming and Their Opposing Influences over the Northeast Atlantic Region

Abstract Using a large ensemble of simulations from the Polar Amplification Model Intercomparison Project (PAMIP) and phase 6 of the Coupled Model Intercomparison Project (CMIP6), we compare the response of winter-mean precipitation and daily extremes across the Northern Hemisphere to future Arctic sea ice loss and global ocean warming. The North Atlantic is simulated to become drier in response to future Arctic sea ice loss, with reduced precipitation intensity and more dry days. A wetting response to sea ice loss is simulated over the midlatitude Atlantic Ocean. These responses are robust across the eight models analyzed, albeit with differences in their magnitude and spatial pattern. The precipitation response to global ocean warming is broadly opposite in sign, but larger in magnitude, compared to the response to sea ice loss, over these regions. The precipitation responses to both sea ice loss and ocean warming are strongly related to coincident changes in storm density and intensity. More specifically, there is an equatorward shift of the North Atlantic storm track in response to sea ice loss, and a northeastern extension of the North Atlantic storm track and a weakening of the Mediterranean storm track in response to ocean warming. The linear combination of the responses of future Arctic sea ice loss and global ocean warming explain well the spatial pattern of the precipitation change at 2°C global warming projected in CMIP6. Our results suggest that the projected future precipitation change over the North Atlantic reflects a “tug of war” between Arctic sea ice loss and global ocean warming, but the latter dominates over the former.

Blondes do it better? A comparative study on the morphometry and life-history traits of commercially important skates blonde ray Raja brachyura, thornback ray Raja clavata, and spotted ray Raja montagui, with management implications

Due to data limitation and challenges with species-specific reporting, the management of European skate fisheries currently lacks measures tailored to individual species. Given these caveats, detailed information about skate stocks at the species level is warranted. The morphometry and life-history parameters were determined for samples of 170 individuals (58 Raja brachyura, 92 R. clavata, 20 R. montagui) collected by observers in commercial fisheries, and two bottom trawl surveys (December 2020 – August 2021) in the Southern North Sea and Eastern English Channel. A combination of three morphometric measurements were considered and proven successful (3.846% misclassification, N = 78) in species discrimination for easily confusable species R. brachyura and R. montagui. Through the application of these morphometric descriptors in electronic catch monitoring via Artificial Intelligence (AI), the misidentification of easily confusable species may be reduced in future catch reporting from surveys, fisheries-dependent data, and market sampling. Additionally, the morphometric differences between species may have implications for species’ catchability, and gear modification to avoid bycatch of skates under the European Landing Obligation (LO). The length-weight relationships indicated a faster rate of increase in body mass per unit of size for R. montagui. Life-history trait parameter estimates were obtained for R. clavata and R. brachyura. Age was determined through digital processing of images from visually enhanced whole vertebral centra (0.01% crystal violet staining). Age reading precision was low (CV > 45%, PA < 60%). The von Bertalanffy and logistic growth models provided more accurate fits for the length-at-age data than the Gompertz model. Macroscopic maturity assessment revealed that male R. montagui matured at the smallest size (Lm = 57.5 cm), while female R. brachyura matured at the largest size (Lm = 87.6 cm). Maturity ogives were fitted for males (L50 = 65.4 cm) and females (L50 = 84.1) of R. clavata and females of R. brachyura (L50 = 82.7 cm), with statistically significant intersexual differences for R. clavata. The Legal Minimum Landing Size (LMLS) measures of smaller sizes may not offer adequate protection (to immature specimens) of the skate species in the present study, that mature at larger sizes. The life-history trait parameters for growth and maturity are discussed in relation to published results of earlier studies, and no major changes in the life-history parameter traits were observed in recent years. The interspecific differences in the morphometries and life-history traits of R. brachyura, R. clavata, and R. montagui highlight the need for species-specific data collection and management considerations of skate stocks in the Northeast Atlantic Region at the local and EU level.

MLVA genotyping of Moritella viscosa reveals serial emergence of novel, host-specific clonal complexes in Norwegian salmon farming.

A Multi-Locus Variable number of tandem repeat Analysis (MLVA) genotyping scheme was developed for the epidemiological study of Moritella viscosa, which causes 'winter ulcer' predominantly in sea-reared Atlantic salmon (Salmo salar L.). The assay involves multiplex PCR amplification of six Variable Number of Tandem Repeat (VNTR) loci, followed by capillary electrophoresis and data interpretation. A collection of 747 spatiotemporally diverse M. viscosa isolates from nine fish species was analysed, the majority from farmed Norwegian salmon. MLVA distributed 76% of the isolates across three major clonal complexes (CC1, CC2 and CC3), with the remaining forming minor clusters and singletons. While 90% of the salmon isolates belong to either CC1, CC2 or CC3, only 20% of the isolates recovered from other fish species do so, indicating a considerable degree of host specificity. We further highlight a series of 'clonal shifts' amongst Norwegian salmon isolates over the 35-year sampling period, with CC1 showing exclusive predominance prior to the emergence of CC2, which was later supplanted by CC3, before the recent re-emergence of CC1. Apparently, these shifts have rapidly swept the entire Norwegian coastline and conceivably, as suggested by typing of a small number of non-Norwegian isolates, the Northeast Atlantic region as a whole.

Refining the Resolution of DUACS Along-Track Level-3 Sea Level Altimetry Products

This paper describes the demonstration of a regional high-resolution level-3 (L3) altimeter data unification and altimeter combination system (DUACS) developed with support from the French space agency (CNES). Deduced from full-rate (20 Hz to 40 Hz) level-2 (L2) altimeter measurements, this product provides sea level anomalies (SLA) and other essential physical variables at a spatial resolution of one sample every ~1 km over the North Atlantic Ocean. This allows us to resolve wavelengths from ~35 km to ~55 km depending on the altimeter considered. This was made possible by recent advances in radar altimeter processing for both synthetic aperture radar (SAR) and low-resolution-mode (LRM) measurements, as well as improvements made to different stages of the DUACS processing chain. Firstly, the new adaptive and low-resolution with range migration correction (LR-RMC) processing techniques were considered for Jason and Sentinel-3 (S3A), respectively. They significantly reduce errors at short wavelengths, and the adaptive processing also reduces possible land contamination near the coast. Next, up-to-date geophysical and environmental corrections were selected for this production. This includes specific corrections intended to reduce the measurement noise on LRM measurements and thus enhance the observability at short wavelengths. Compared with the 1 Hz product, the observable wavelengths reached with the demonstration high-resolution product are reduced by up to one third, or up to half in the northeast Atlantic region. The residual noises were optimally filtered from full-rate measurements, taking into consideration the different observing capabilities of the altimeters processed. A specific data recovery strategy was applied, significantly optimizing the data availability, both in the coastal and open ocean areas. This demonstration L3 product is thus better resolved than the conventional 1 Hz product, especially near the coast, where it is defined up to ~5 km against ~10 km for the 1 Hz version. Multi-mission cross-calibration processing was also optimized with an improved long-wavelength error (LWE) correction, leading to a better consistency between tracks, with a 9–15% reduction in SLA variance at cross-overs. The new L3 product improves the overall consistency with tide gauge measurements, with a reduction in SLA differences variance by 5 and 17% compared with the 1 Hz product from the S3A and Jason-3 (J3) measurements, respectively. Primarily intended for regional applications, this product can significantly contribute to improving high-resolution numerical model output via data assimilation. It also opens new perspectives for a better understanding of regional sea-surface dynamics, with an improved representation of the coastal currents and a refined spectral content revealing the unbalanced signal.

Conditional sea surface statistics and their impact on geophysical sea surface parameters retrieved from SAR altimetry signals

In this study we present an analytical formulation of synthetic-aperture radar (SAR) altimetry signals including narrow banded nonlinear wave fields and conditional statistics between wave elevation displacements, horizontal wave slopes and vertical wave particle velocities. Considering the wave elevation displacements coskewness with respect to horizontal slopes leads to an analytical formulation of the electromagnetic bias within a SAR-mode altimeter stack. This formulation can be either parametrized by the significant wave height (SWH) and mean wave steepness, or in terms of the variance of vertical wave velocities. The effect of conditional vertical wave particle velocity variances with respect to the observed horizontal wave slopes close to nadir incidence angles leads to an effective reduction of the azimuth blurring of SAR-mode stacks. We present here a formulation of this effect by examining JONSWAP ocean wave spectra. In most cases this effect reduces the azimuth blurring by 10% to 30%. Additionally we investigate the effect of a nonlinear wave elevation displacement probability density function (PDF) on estimated geophysical parameters. We were able to show that including an elevation displacement skewness of 0.13 improves significantly the SWH consistency between altimetry and ECMWF Reanalysis v5 ERA5 results.All of these effects are validated with respect to ERA5 model data in the North East Atlantic region and in situ data located in the German Bight and Baltic Sea.The developed model can be used in both SAR and conventional altimetry retrackers.

Connectivity patterns and gene flow among Chelon ramada populations

Catadromous species, such as the thinlip grey mullet Chelon ramada (Risso 1827), exhibit complex life history traits and migratory behaviours that have different repercussions at the population level and species genetic structure. To study the genetic variation and infer patterns of gene flow and population connectivity along species’ distribution across the Northeast Atlantic coast and the Mediterranean Sea, 457 individuals from sixteen locations were genotyped using eleven microsatellite markers. The existence of a metapopulation with high gene flow was supported by the absence of significant genetic differentiation among locations or geographic clustering of samples. The Portuguese populations are important for the maintenance of connectivity among populations of the Mediterranean and Northeast Atlantic regions, as evidenced by the high degree of gene flow observed between the Portuguese coast and all populations from these two regions.Our findings suggest that the thinlip grey mullet display a high dispersal capability, that combined with continuous habitat availability and large population numbers (low commercial exploitation in the Atlantic region), allow the maintenance of a unique genetic group.

Regional microbiome differentiation of the invasive Sargassum muticum (Fucales, Phaeophyceae) follows the generalist host hypothesis across the North East Atlantic

ABSTRACT Over 90% of introduced marine species are seaweeds. Seaweeds rely on their microbiome for host settlement, nutrition, development and health. As such, it is likely that microbiomes are involved in seaweed invasions. Sargassum muticum, indigenous to Southeast Asia, inhabits the North-east Atlantic from Norway to Morocco. This is the only known successful case of a non-clonal marine invader with almost no genetic variation over its large NE Atlantic introduced range. This makes it a very interesting model to study an invasive seaweeds microbiome, as it practically uncouples host genetic variation from microbiome variation. Associated bacteria potentially contribute to the plasticity and acclimation of S. muticum leading to its success over the last 50 years. Dispersing host organisms can either bring their acquired microbes along or obtain new ones locally, following the mutualist and generalist host hypothesis, respectively. We used partial 16S rRNA gene amplicon sequencing to characterize the total and core microbiome across S. muticum structures/tissues from five NE Atlantic regions, from Norway to Morocco, covering over 30° of latitude. In contrast to host genotypes, highly diverse, regional, total and core microbiomes, with differentiation levels depending on tissue, bacterial community structure were detected. Atlantic S. muticum follows the generalist host hypothesis, possibly recruiting a new microbiome in each new region. This host promiscuity may promote the invasiveness of S. muticum. Diversity was lower in the young/annual tissues compared with the older tissues for the total bacterial community, suggesting that these are mostly transitory bacteria accumulating over time in the older parts. The total core microbiome included 10 OTUs, representing dominant community members commonly found in other seaweeds’ cores. The core Granulosicoccus OTU followed a clear regional pattern where northern and southern regions clustered differentially, suggesting a regional signature even at an OTU level. HIGHLIGHTS North-east (NE) Atlantic Sargassum muticum microbiome differentiation does not match host genetic background. NE Atlantic S. muticum shows a geographic region and tissue-specific total and core bacterial community matching bestthe generalist host hypothesis. Core OTU – the bacterium Granulosicoccus – shows a strong regional specialization.

Spotlight on coarse sediments: Comparative characterization of a poorly investigated seafloor biotope in the German Bight (SE North Sea)

Extensive marine benthos surveys have resulted in a solid understanding of the broad distribution pattern of seafloor biotopes in the southeastern North Sea (temperate northeast Atlantic region). However, due to the low spatial resolution of large-scale surveys, specific smaller-scale biotopes with scattered distribution have been insufficiently captured. Consequently, knowledge regarding the environmental characteristics and species inventories of some specific biotopes is still limited. We investigated the habitat characteristics and the macro-infauna (i.e., organisms in samples collected by a sediment grab and retained in a sieve with a mesh size of 1000 μm) of a spatially restricted, patchy coarse sediment (i.e., grain size fraction >500 μm accounting for ≥60% of the total sample mass) biotope in the German Bight over three consecutive years. Habitat and faunal characteristics were contrasted with four other benthic biotopes sampled at the same time to allow for a comparative evaluation. Our study revealed considerable fluctuations in grain size distribution among samples of the coarse sediment, potentially resulting from a frequent redistribution of sediments. A total number of 243 infauna taxa were identified at the 66 stations sampled over three consecutive years (16–33 stations per year) with a considerable proportion of endangered and rare species. The results highlight that previous studies have underestimated the species richness of the biotope. The focus on this previously poorly studied biotope type allowed us to detect species in the study region that were formerly unreported. The macro-infauna in the coarse sediments was characterized by comparatively high abundance and biomass, which may provide a rich food resource for organisms from higher trophic levels. Therefore, coarse sediments likely are an ecologically valuable seafloor biotope despite its limited coverage.

Current interaction in large-scale wave models with an application to Ireland

A nested large-scale wave model that covers most of the Atlantic Ocean and focuses on generating accurate swell conditions for Ireland is presented and validated over the two years 2016−2017. A sensitivity analysis for the βmax parameter appearing in the wind input formulation is carried out, optimising the extreme significant wave heights from the model against altimetry data in the North-East Atlantic region around Ireland. An optimal value of 1.75 is found using the ERA5 reanalysis corrected beforehand for a well-known negative bias for the high wind speed values. The impact of currents is studied using the surface currents from the GLORYS12 product. Currents slightly reduce by 1% the root-mean-square and bias errors for significant wave height compared to altimetry data. However, they explain most of the wave energy at scales less than 50m. The variability induced by currents is found to be more noticeable when looking at the satellite tracks. Track following observations indicate that wave refraction and advection induced by mesoscale eddies are correctly captured by the model, inducing a spatial variability reaching up to 0.5m. However, this modulation is of the same order as a shorter-scale variability appearing in the altimetry data. An averaging operator is used to smooth the data and remove those high-frequency variations. The main finding is that a spatial shift seems to appear between the model and the observations, attributed to the relatively poor resolution of the current product used for the scales observed.

Observation of Abrupt Changes in the Sea Surface Layer of the Adriatic Sea

We observed interannual changes in the temperature and salinity of the surface layer of the Adriatic Sea when measured during the period 2005–2020. We observed non-stationarity and a positive linear trend in the series of mixed layer depth, heat storage, and potential energy anomalies. This non-stationarity was related to the climate regime that prevailed between 2011 and 2017. We observed significant changes in the interannual variability of salinity above and below the mixed layer depth and a positive difference in the surface barrier layer. In an effort to reconstruct the cause of this phenomenon, a multi-stage investigation was conducted. The first suspected culprit was the change in wind regime over the Mediterranean and Northeast Atlantic regions in September. Using the growing neural gas algorithm, September wind fields over the past 40 years were classified into nine distinct patterns. Further analysis of the CTD data indicated an increase in heat storage, a physical property of the Adriatic Sea known to be strongly influenced by the inflow of warm water masses controlled by the bimodal oscillating system (BiOS). The observed increase in salinity confirmed the assumption that BiOS activity affects heat storage. Unexpectedly, this analysis showed that an inverse vertical salinity profile was present during the summer months of 2015, 2017, and 2020, which can only be explained by salinity changes being a dominant factor. In addition, the aforementioned wind regime caused an increase in energy loss through latent energy dissipation, contributing to an even larger increase in salinity. While changes in the depth of the mixed layer in the Adriatic are usually due to temperature changes, this phenomenon was primarily caused by abrupt changes in salinity due to a combination of BiOS and local factors. This is the first record of such an event.

Achieving greater policy coherence and harmonisation for marine litter management in the North-East Atlantic and Wider Caribbean Region

The effects of marine litter pose ecological, economic and optional value threats to the countries and territories on the margins of the Atlantic Basin. As the abundance of transboundary marine litter increases, this in turn has triggered the development of marine litter policy action plans and inter-regional collaboration. The OSPAR Commission and Cartagena Convention of North-East Atlantic (NEA) and the Wider Caribbean Region (WCR) respectively, have established a memorandum of understanding to facilitate collaboration for enhanced marine litter management. In light of this development, this paper conducts a scoping review of management measures of marine litter within these regions as well as a coherence analysis between their regional action plans (RAPs). The analysis uses a proactive framework based on a modified categorization by Chen (2015) and Williams and Rangel-Buitrago (2019) for comparatively analyse management measures. The analytical categorizations include legislation and enforcement measures, prevention, removal, monitoring, research, information management and exchange and education and outreach. Although specific approaches differed among the regions depending upon geographical and individual situations, each categorization included detailed management activities except for prevention in NEA and removal in the WCR. The comparative analysis demonstrates that there are opportunities for inter-regional cooperation, knowledge sharing and overall enhanced and informed marine litter management.

Shipping in the north-east Atlantic: Identifying spatial and temporal patterns of change

Maritime traffic is increasing globally, with a four-fold increase in commercial vessel movements between 1992 and 2012. Vessels contribute to noise and air pollution, provide pathways for non-native species, and collide with marine wildlife. While knowledge of shipping trends and potential environmental impacts exists at both local and global levels, key information on vessel density for regional-scale management is lacking. This study presents the first in-depth spatio-temporal analysis of shipping in the north-east Atlantic region, over three years in a five-year period. Densities increased by 34%, including in 73% of Marine Protected Areas. Western Scotland and the Bay of Biscay experienced the largest increases in vessel density, predominantly from small and slow vessels. Given well-documented impacts that shipping can have on the marine environment, it is crucial that this situation continues to be monitored – particularly in areas designated to protect vulnerable species and ecosystems which may already be under pressure.

Plastic pollution pathways from marine aquaculture practices and potential solutions for the North-East Atlantic region

Aquaculture practices at sea are far from impact neutral and remain an important source of marine plastic pollution. With projected rapid continual growth in the sector, if left unmanaged, aquaculture pollution can have detrimental environmental and social implications. Using the DPSIR framework, the paper examines current practices and pathways of plastic pollution from marine aquaculture in the NE-Atlantic, drawing on findings from literature, stakeholder consultations and beach litter assessments. Pathways for aquaculture-related litter identified include rough weather, farmer behavior, inadequate access to recycling facilities, low price of consumable plastics and high cost of recycling. Beach litter analyses conducted as part of the study exposed serious issues of under quantification, resulting from difficulties in source identification and a lack of detailed categorization in official monitoring systems. The paper makes recommendations to improve litter quantification and waste management, including the use of local knowledge and experts to identify sources of marine litter.

Probabilistic Linear Inversion of Satellite Gravity Gradient Data Applied to the Northeast Atlantic

AbstractWe explore the mantle density structure of the northeast Atlantic region using constrained linear inversion of the satellite gravity gradient data based on statistical prior information and assuming a Gaussian model. The uncertainty of the residual gravity gradient signal is characterized by a covariance matrix obtained using geostatistical analysis of controlled‐source seismic data. The forward modeling of the gravity gradients in the 3D reference crustal model is performed using a global spherical harmonics analysis. We estimate the model covariance function in the radial and angular directions using a variogram method. We compute volumetric gravity gradient kernels for a spherical shell covering the northeast Atlantic region down to the mantle transition zone (410 km depth). The solution of the linear inverse problem in the form of the mean density model and the posterior covariance matrix follows a least squares approach. The results indicate that on average the seismic velocity variation is proportional to the density variation in the northeast Atlantic region. However, a noticeable mismatch or anti‐correlation exists in some areas, such as the Greenland‐Iceland‐Faroe ridge and southwestern Norway. The predicted low‐density anomalies at depths of 100–150 km underneath the northeast Atlantic Ocean are correlated with the distribution of Cenozoic submarine volcanoes and seamount‐like features of the seafloor.

The Increasing Frequency of Tropical Cyclones in the Northeastern Atlantic Sector

North Atlantic Tropical Cyclones (TCs) are major atmospheric hazards that can cause large disruptions to coastal and near-coastal societies. Although most studies focus on those areas with highest impact (e.g., Caribbean Islands, the Gulf and western coast of United States), there is an increasing interest in characterizing changes in occurrence and impacts in areas usually less affected by TCs, particularly in the framework of a changing climate. Here we provide a long-term context evaluating changes in the frequency of TC in the Northeast Atlantic (NEA) basin during the 1978–2019 period. In the last decades, scattered information has shown an impact both from TCs and Post-Tropical Cyclones (PTC) in the NEA. We compute several complementary linear trends and show a significant (p ≤ 0.1) increase in the number of stronger storms in the entire North Atlantic basin, and the amount of TCs and PTCs that reach the NEA, in agreement with previous works. A highly significant relation (p ≤ 0.05) is found between the Atlantic Multidecadal Oscillation (AMO) index and TC activity in both the entire North Atlantic and the NEA basin. Sea surface temperature anomaly maps are produced to better encapsulate the annual variability without the multidecadal oscillation effects and, important cold (warm) pools in cyclogenesis and development zones are found in years with low (high) TC activity. It is also found that the sea surface temperature field plays a minor role in the guiding of storms into the NEA sector. Long-term trends as well as high/low seasonal activity analysis suggest that atmospheric circulation (vertical wind shear, lapse rate, mean sea level pressure and upper-level steering) is more relevant than sea surface temperature in the NEA region.

Seasonal Trends of Aerosol Hygroscopicity and Mixing State in Clean Marine and Polluted Continental Air Masses Over the Northeast Atlantic

AbstractFive years of nearly continuous measurements of aerosol hygroscopicity by a Humidified Tandem Differential Mobility Analyzer (HTDMA) at Mace Head research station are presented, making it the longest aerosol hygroscopicity data set in marine environment and Northeast Atlantic region in particular. The main goal of this work was to examine seasonal patterns of aerosol hygroscopicity and mixing state in a variety of air masses. The entire data set was categorized into clean marine and polluted continental sectors to reveal contrasting physicochemical features. Distinct seasonal patterns were revealed where hygroscopicity of the clean sector aerosol was significantly higher than that of the polluted sector aerosol. The median growth factors (GF) of clean and polluted sectors were 1.67 and 1.31, respectively. Clean sector aerosol median GF reached the lowest values in summer and the highest in winter pointing at an impact of marine biological activity and wind speed driven sea spray production to aerosol hygroscopicity. Conversely, polluted sector aerosol reached the highest median GF of all sizes in summer due to the decrease of anthropogenic emission, enhanced photochemical aging, and secondary inorganic aerosol formation. Wintertime aerosols in both sectors were largely externally mixed, while summertime aerosols were relatively internally mixed. A distinct subset of near‐hydrophobic Aitken mode particles smaller than 50 nm in diameter was observed in the wintertime clean sector which most likely originated in the clean marine atmosphere based on the evolution of air mass back trajectory clustering.

Six steps to produce stock assessments for the Marine Strategy Framework Directive compliant with Descriptor 3

Abstract In the European Union (EU), the ecosystem approach to fisheries is implemented through several directives and polices, which are overarched by the Marine Strategy Framework Directive (MSFD). The MSFD requires the assessment of the environmental status of exploited fish and shellfish stocks, among others, to advise the EU Common Fisheries Policy (CFP) on sustainable catch options. The stock assessments for the CFP and the MSFD are supposed to be congruent, yet they differ in several substantial subjects. While the annual CFP assessment is based on two indicators, fishing mortality (F) and spawning stock biomass (SSB), in its Descriptor 3 (D3) the MSFD requires the assessment of three criteria (F, SSB, and age or size structure) within a six year period. Assessing exploited fish and shellfish stocks under the MSFD by using existing CFP assessments has therefore been a half-completed task, which had to be fulfilled by the member states of the EU. This paper suggests six easy steps, referred to as “quick wins” (QW), which are based on existing information from CFP stock assessments. The implementation of these six QW would allow for assessments of exploited fish and shellfish stocks that are compliant to D3. These QW are to (i) assess length/age structure within a stock, (ii) analyse and assess selectivity by fisheries, (iii) use all available information to assess a stock, (iv) use response indicators to assess environmental targets, (v) provide integrated stock-specific advice, and (vi) provide assessments with a mid-term perspective over a-period of six years. International Council for the Exploration of the Sea (ICES) combines the infrastructure and expertise to produce stock-specific assessment products tailored to the requirements of MSFD D3. Thereby, ICES could provide a valuable service to EU member states in the north-east Atlantic region by providing scientifically validated, quality-assured, and MSFD-compliant single-stock assessment products. This would be a big advancement towards implementing the ecosystem approach to fisheries management within Europe.