Search

The northeastern part of the North Atlantic subpolar gyre is a key passage for the Atlantic Meridional Overturning Circulation upper cell. To this day, the precise pathway and intensity of bottom currents in this area is not clear. In this study, we make use of regional high resolution numerical modeling to suggest that the main bottom current flowing south of Iceland originates from both the Faroe‐Banks Channel and the Iceland‐Faroe Ridge and then flows along the topographic slope. When flowing over the rough topography, this bottom current generates a 200 m large bottom mixed layer. We further demonstrate that many submesoscale structures are generated at the southernmost tip of the Icelandic shelf, which subsequently spread water masses in the Iceland Basin. These findings have major implication for the understanding of the water masses transport in the North Atlantic, and also for the distribution of benthic species along the Icelandic shelf. Plain Language Summary: Water masses formed in the Arctic Ocean overflow into the North Atlantic at the bottom of the ocean, forming the so‐called upper cell of the Atlantic Meridional Overturning Circulation (AMOC). The pathway of the currents carrying these water masses is still under debate due to a lack of observations. In this study, we discuss in details the pathway of these bottom currents in the specific area south of Iceland. We show that a steady current flows along the Icelandic continental shelf, and then divide in smaller structures when reaching the southernmost tip of Iceland. We also show that on its way, the current mixes the bottom layer of the ocean. These findings have major implication in the understanding of heat and carbon transport at depth in this area, which constitute an important response of the climate to anthropogenic forcing. Key Points: An intense bottom boundary current originating from the Iceland‐Faroe Ridge and the Faroe Bank Channel flows along the Icelandic ShelfThe rough topography and the intensity of the current lead to bottom mixing and sustain a large bottom mixed layerSubsmesoscale structures generated locally participate in the spreading of deep water masses in the Iceland Basin [ABSTRACT FROM AUTHOR]

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. • Orogenic stress relaxation allowed the NE Atlantic and Arctic Oceans to open. • LIP magmatism did not drive breakup but was a consequence of extension. • ∼80% the Arctic Ocean and ∼ 50% of the NE Atlantic Ocean contains hybrid crust. • The Arctic Alpha-Mendeleev Rise is a continental, double-sided passive margin. • The Greenland-Iceland-Faroe Ridge is underlain by hybrid crust. [ABSTRACT FROM AUTHOR]

Presented here is an illustrated checklist of benthic marineOstracoda (Crustacea) recorded fromRecent surface sediments of the sub-polar North Atlantic Ocean (SPNA). It presents 142 species (and species groups) belonging to 62 genera from 41 sampling sites collected from the water depths of 144-2749 m. We provide census datawith scanning electron microscope images of representative specimens of most species, aswell as geographical and bathymetrical distributionmaps of selected species and genera. Samples from the Nordic seas (i.e., Greenland Sea, Norwegian Sea), as well as North Atlantic proper waters (i.e., Irminger Sea, Iceland Sea) are included. The bathymetry covers shelf to continental rise surface sediments from the Irminger Basin, the Iceland Basin, the Iceland Plateau, the Denmark Strait, the Faeroe-Shetland Channel, the Iceland-Faeroe Ridge, the Reykjanes Ridge, and the Faeroe Plateau. The data presented here is an important taxonomic and biogeographical baseline of the SPNA benthic ostracod fauna. [ABSTRACT FROM AUTHOR]

The European eel hatches in the Sargasso Sea and migrates across the Atlantic Ocean toward Europe. At the continental shelf, larvae metamorphose into glass eels and then recruit to coastal habitats and estuaries. Among other cues, glass eels orient in situ using lunar cues, but what role this lunar compass plays in their recruitment to the coast is unknown. To assess this, we incorporated empirical in situ observations of glass eel swimming and lunar‐driven orientation into a biophysical advection model. We simulated dispersal of glass eels drifting with the North Atlantic Current to test the hypothesis that lunar‐driven swimming and orientation behavior affects recruitment to North Sea coasts. Particles were released from the continental slope north of Scotland, an obligate passage for migrating eel larvae. Four numerical experiments were conducted: one with passive drift and three including glass eel swimming speeds (ranging from 3 to 12 cm/s) and lunar‐driven orientation. With a speed of 3 cm/s, the lunar compass increased recruitment to the North Sea coasts of Southwestern Norway and Scotland by 34%–40%. Conversely, orientation behavior decreased recruitment to northern areas like Iceland (−46%), the Faroe Islands (−39%) and Northern Norway (−49%). Behavior affected the timing of recruitment to Southwestern Norway, causing peaks of abundance in May–June, but not to other regions. These results show that lunar‐driven orientation and swimming behavior observed in glass eels substantially increases their recruitment to North Sea coasts. Results agree with the distribution of eel in northern Europe, which decreases in abundance with increasing latitude. [ABSTRACT FROM AUTHOR]

Although grey seals (Halichoerus grypus) are the focus of considerable research effort throughout much of their North Atlantic breeding range, little is known about grey seal movement ecology in Iceland. This is surprising given the long history of grey seal exploitation in Iceland and because grey seals are common bycatch in commercial fisheries. Here, for the first time, we deployed satellite tags on five grey seals in Iceland to quantify the at-sea spatial usage of recently weaned pups during their first year of life. Maximum foraging trip distance ranged from 20 to 160 km for individual pups, while maximum duration ranged from 4.3 to 20.8 days. Individual differences in foraging trip metrics indicated two broad strategies. Specifically, pups either remained near the deployment location or dispersed to the east of Iceland, reaching a total distance of > 300 km from the deployment location. Foraging trips were, however, typically restricted to the continental shelf, which presumably reflects a preference for benthic foraging, as is reported for grey seals at other breeding locations. Our preliminary findings highlight the importance of near-shore waters to recently weaned grey seal pups in Iceland and suggests that coastal fisheries are a prevalent threat. However, additional research is required to quantify interactions between grey seals and commercial fisheries, which in turn, would improve the efficacy of conservation and management efforts. [ABSTRACT FROM AUTHOR]

The fragmentary glacial-geological record across the Icelandic continental shelf has hampered reconstruction of the volume, extent and chronology of the Late Weichselian ice sheet particularly in key offshore zones. Marine geophysical data collected over the last two decades reveal that the ice sheet likely attained a continental shelf-break position in all sectors during the Last Glacial Maximum, though its precise timing and configuration remains largely unknown. Within this context, we review the available empirical evidence and use a well-constrained three-dimensional thermomechanical model to investigate the drivers of an extensive Late Weichselian Icelandic ice-sheet, its sensitivity to environmental forcing, and phases of deglaciation. Our reconstruction attains the continental shelf break across all sectors with a total ice volume of 5.96 × 10 5 km 3 with high precipitation rates being critical to forcing extensive ice sheet flow offshore. Due to its location astride an active mantle plume, a relatively fast and dynamic ice sheet with a low aspect ratio is maintained. Our results reveal that once initial ice-sheet retreat was triggered through climate warming at 21.8 ka BP, marine deglaciation was rapid and accomplished in all sectors within c. 5 ka at a mean rate of 71 Gt of mass loss per year. This rate of ice wastage is comparable to contemporary rates observed for the West Antarctic ice sheet. The ice sheet subsequently stabilised on shallow pinning points across the near shelf for two millennia, but abrupt atmospheric warming during the Bølling Interstadial forced a second, dramatic collapse of the ice sheet onshore with a net wastage of 221 Gt a −1 over 750 years, analogous to contemporary Greenland rates of mass loss. Geothermal conditions impart a significant control on the ice sheet's transient response, particularly during phases of rapid retreat. Insights from this study suggests that large sectors of contemporary ice sheets overlying geothermally active regions, such as Siple Coast, Antarctica, and NE Greenland, have the potential to experience rapid phases of mass loss and deglaciation once initial retreat is initiated. [ABSTRACT FROM AUTHOR]

The common minke whale (Balaenoptera acutorostrata) is the most abundant mammalian top predator in Icelandic continental shelf waters. Here, an account is given on the first systematic research programme into the feeding ecology of common minke whales in Icelandic waters based on an analysis of minke whale stomach contents data collected in Icelandic waters during 2003–2007. The results show pronounced spatial and temporal variation in the diet. The temporal changes include a decrease in the proportion of sandeel in the diet over the study period and a corresponding increase in herring (Clupea haerengus) and haddock (Melanogrammus aeglefinus), particularly in the southern area. The diet also differed markedly from the previously available, limited data from Icelandic waters with less krill and the cold water species capelin (Mallotus villosus) and more gadoids and herring in the more recent period. These changes in diet composition are consistent with recent changes in the Icelandic continental shelf ecosystem, including increased sea surface and bottom temperatures and changes in distribution and abundance of several fish species, including sandeel (Ammodytidae) and capelin. Although natural fluctuations cannot be ruled out at this stage, these dietary changes, together with decreased abundance in coastal waters, may reflect the responses of minke whales to a changed environment possibly driven by global warming. [ABSTRACT FROM AUTHOR]

Abstract: A large collection of ampeliscids (15,454 specimens from 366 sampling sites) from Icelandic waters was identified to species and distributional patterns analysed. The specimens were sampled during the BIOICE programme, the main objective of which was to map the invertebrate species diversity within the Icelandic economical zone (758,000km2). Nineteen species were identified: ten Ampelisca (8018 specimens), six Byblis (4887 specimens), three Haploops (1673 specimens), plus a complex of Haploops spp. (876 specimens). Four of these 19 species are new records for Icelandic waters: A. dalmatina Karaman, 1975 was previously known around the Faroe Islands; B. abyssi Sars, 1879 and B. affinis Sars, 1879 were known from the NE Atlantic and B. medialisMills (1971) from the NW Atlantic. The three most abundant species were B. minuticornis Sars, 1879, B. gaimardi (Kröyer, 1846) and A. uncinata Chevreux, 1887, while the three most frequently occurring species at all stations were H. setosa Boeck, 1871, A. uncinata and A. macrocephala Lilljeborg, 1852. Species were grouped according to three geographical patterns: northern species (six species), southern species (nine species) and circum-Icelandic species (four species). The species were also grouped according to three depth categories: nine species were confined to the continental shelf and the upper part of the continental slopes around Iceland; nine species had a wide bathymetric range and one species (A. islandica) occurred only in deep waters. Factors related to water depth exerted the main influence on ampeliscid distribution patterns around Iceland. A comparison of the Icelandic Ampeliscidae fauna with five areas of the North Atlantic Ocean showed a strong similarity to the fauna of Faroe Islands and a lesser similarity to the NW Atlantic fauna. [Copyright &y& Elsevier]

The diversity, taxonomy and distribution of the Opheliidae (Annelida: Polychaeta) in Icelandic waters is reviewed based on material collected during the BIOICE project. Nine opheliid species are recorded from Iceland; of these, three were previously reported in the area ( Ophelia limacina, Ophelina cylindricaudata and O. acuminata), four are new for Icelandic waters ( Ammotrypanella cf. arctica, Ophelina abranchiata, O. helgolandica and Tachytrypane jeffreisii), and two are new to science. Ophelina basicirra sp. nov. is distinguished by having a narrow anal tube with one short proximal anal cirrus in ventral position. Ophelina bowitzi sp. nov. is characterized by the small size of its anterior branchiae, which become larger in the middle and posterior body regions, and by an upwardly bent anal tube that is wide at the base and narrowing distally. The genera Euzonus, Armandia and Polyophthalmus are not represented in the BIOICE samples. The distribution of each species off Iceland is presented; one species is restricted to shallow waters of northwestern fjords, three species are found south of the GIF Ridge, and five species are circumicelandic. Several body characters with taxonomic relevance in some species are reviewed based on SEM images. Furthermore, as a first step towards a future revision of the genus Ophelina Örsted in North Atlantic waters, the status of each species originally described or subsequently reported from the area is commented on, and a key to the currently valid species is presented. Ophelina longicephala Hartmann-Schröder, , formerly a subspecies of O. delapidans (Kinberg, ), is raised to species status. [ABSTRACT FROM AUTHOR]

Abstract: The Irminger Current (IC) transports heat and nutrients to the Icelandic shelf and its fluctuations are strongly linked to variations in the strength of the North Atlantic surface flow from the south. By using benthic foraminiferal assemblages and their stable isotopic composition in two marine sediment cores located in the pathway of the IC on the West Iceland shelf we were able to derive bottom water temperature estimates at a ~100year resolution and define the temperature difference between the core sites throughout the Holocene. These are the first transfer function bottom water temperatures presented from the Icelandic shelf based on benthic foraminiferal assemblages. Our findings demonstrate a delayed Holocene Thermal Maximum in the marine current system around Iceland compared to the Northern Hemisphere summer insolation receipts. The maximum heat transport in the IC occurred between 8 and 4kayears, later than some previous records report. A reconstruction of the ambient seawater δ18O based on paired samples of C2 transfer function temperature estimates and oxygen isotopic composition indicates repeated freshwater input to the N-Atlantic inflow in the early Holocene impacting the current system before 8ka. Two fundamental regime shifts are evident in the paleoceanography and foraminiferal properties during the Holocene, occurring around 8ka towards more stable conditions and again around 4ka towards more unstable conditions. Increasing fluctuation with similarities to the Great Salinity Anomaly in the 1970s occur after 4ka. [ABSTRACT FROM AUTHOR]