| 1. |
- Anderson, Leif G, 1951, et al.
(författare)
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Arctic ocean shelf–basin interaction: An active continental shelf CO2 pump and its impact on the degree of calcium carbonate solubility
- 2010
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Ingår i: Deep Sea Research Part I: Oceanographic Research Papers. - : Elsevier BV. - 0967-0637. ; 57:7, s. 869-879
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Tidskriftsartikel (refereegranskat)abstract
- The Arctic Ocean has wide shelf areas with extensive biological activity including a high primary productivity and an active microbial loop within the surface sediment. This in combination with brine production during sea ice formation result in the decay products exiting from the shelf into the deep basin typically at a depth of about 150 m and over a wide salinity range centered around S 33. We present data from the Beringia cruise in 2005 along a section in the Canada Basin from the continental margin north of Alaska towards the north and from the International Siberian Shelf Study in 2008 (ISSS-08) to illustrate the impact of these processes. The water rich in decay products, nutrients and dissolved inorganic carbon (DIC), exits the shelf not only from the Chukchi Sea, as has been shown earlier, but also from the East Siberian Sea. The excess of DIC found in the Canada Basin in a depth range of about 50–250 m amounts to 90±40 g C m−2. If this excess is integrated over the whole Canadian Basin the excess equals 320±140×1012 g C. The high DIC concentration layer also has low pH and consequently a low degree of calcium carbonate saturation, with minimum aragonite values of 60% saturation and calcite values just below saturation. The mean age of the waters in the top 300 m was calculated using the transit time distribution method. By applying a future exponential increase of atmospheric CO2 the invasion of anthropogenic carbon into these waters will result in an under-saturated surface water with respect to aragonite by the year 2050, even without any freshening caused by melting sea ice or increased river discharge.
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| 2. |
- Andersson, Helén C., 1968, et al.
(författare)
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Regulation of the Indonesian throughflow by baroclinic draining of the North Australian Basin
- 2005
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Ingår i: Deep-Sea Research Part I-Oceanographic Research Papers. - : Elsevier BV. - 0967-0637. ; 52:12, s. 2214-2233
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Tidskriftsartikel (refereegranskat)abstract
- The Indonesian throughflow (ITF) is studied using historic hydrographical data with purpose of obtaining a description of the characteristics of the large-scale flow and an understanding of both the forcing and control of the flow. The investigation makes use of the steric sea level and the contents of freshwater and heat in the water Column integrated down to the depth of the deepest connection (effective sill depth) between the Pacific and Indian Oceans within the Indonesian seas. It is shown that it is mainly low-saline water of North Pacific origin that fills the upper part of both the Indonesian seas and a downstream buoyant (surface) pool (DBP) that stretches horizontally over a large part of the North Australian Basin. The long-term mean steric sea level in the Indonesian seas is approximately horizontal and equal to the sea level in the neighboring part of the Pacific Ocean. This indicates small frictional losses against the mean throughflow, which is verified using a coupled multiple basin model of the Indonesian seas. The chan e of the steric sea level, from the Pacific Ocean level to the Indian Ocean level, Occurs essentially at the border between the DBP and the adjacent Indian Ocean. It is found that Darwin is situated inside the DBP, indicating that the sea level recorded in this place is a poor representative of mean and low frequency parts of the sea level variability of the Indian Ocean. It is argued that the control of ITF is set by the baroclinic transport capacity of the DBP relative to the adjacent (Indian Ocean) water. The mean ITF, estimated as the Outflow from the DBP to the South Equatorial Current, is about 10 Sv. The integrated ITF imprint is fresh and cold and the net heat transport is estimated to be 0.3 PW. The buffering capacity of the DBP is about 5 years, so variations in the circulation should be modest on shorter time-scales. It is suggested that the atmospheric transfer of freshwater to the North Pacific and vertical mixing in the North Pacific provide the driving of the mean ITF and that ITF is a major branch of the estuarine-type vertical circulation of the North Pacific. (c) 2005 Elsevier Ltd. All rights reserved.
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| 3. |
- Andersson, Helén C., 1968, et al.
(författare)
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Thermohaline circulation in a two-layer model with sloping boundaries and a mid-ocean ridge
- 2004
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Ingår i: DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH. - : Elsevier BV. - 0967-0637. ; 51:1, s. 93-106
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Tidskriftsartikel (refereegranskat)abstract
- A model ocean basin has continental slopes at the west and north and a mid-ocean ridge running north-south. The first problem treated here is Stommel's (Deep-Sea Res. 5 (1958) 80) abyssal flow of a homogeneous fluid in the presence of topography with a source of fluid at the northwest corner. The flow is driven by uniform upwelling everywhere except over the non-flat topography where the fluid is not driven and inviscid. The solution over the topography is determined by conservation of potential vorticity with the flow being driven by matching to the known solution over the flat bottom. A second problem is the two-layer case for which we use an analysis by Salmon (J. Mar. Res. 50 (1992) 341) in which he obtained expressions for the potential vorticity distribution for inviscid, non-forced flow over topography. We produce analytical solutions for the two-layer case. Conservation of potential vorticity over the slopes leads to flows that make large north-south excursions as the fluid crosses the topographic regions over the western slope and the mid-ocean ridge. We justify our procedure by showing a similarity between a wind-driven double gyre solution of Salmon's that shows a cyclonic circulation on the onshore (Gulf Stream) side of the anticyclonic wind gyre and an observed cyclonic gyre in the Slope Sea inshore of the Gulf Stream. For the two-layer case we obtain flow over the midocean ridge in the lower layer that compares favorably with the excursion of particles over the mid-Atlantic Ridge as reported by Defant (Deutsche Atlantische Expedition 'Meteor' 1925-1927, 6, 1941, pp. 191-260; Physical Oceanography, Vol. 1, Pergamon Press, New York, Oxford, London, Paris, 1961). Our inviscid solutions contain sharp discontinuities which will have to be smoothed by friction when viscosity is added, but it is possible that friction will take the flow far from the one that we have derived. A numerical solution of the problem is planned to test this possibility.
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| 4. |
- Belkin, Igor, et al.
(författare)
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On the discovery of ferromanganese nodules in the world ocean
- 2021
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Ingår i: Deep Sea Research Part I. - : Elsevier. - 0967-0637 .- 1879-0119. ; 175
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Tidskriftsartikel (refereegranskat)abstract
- For a century, the discovery of ferromanganese (Fe–Mn) nodules in the World Ocean was universally and indisputably credited to the Challenger circum-global oceanographic expedition of 1872–1876, during which the first manganese nodules and crusts were dredged up from the sea floor in February–March 1873. A century later, a counterclaim appeared in the literature, crediting Nordenskiöld’s expedition on Sofia in 1868, five years before the Challenger findings, for the discovery of Fe–Mn nodules in the ocean. This counterclaim, widely accepted without scrutiny, was based on the Gustaf Lindström (1884) chemical analysis of a single bottom sediment sample among 14 samples from two Arctic expeditions led by Nordenskiöld:Sofia 1868 and Vega 1878–1880. The Lindström (1884) report published as an eight-page brochure in Swedish remained almost unknown to the research community until now. A close examination of this report and other historical evidence revealed that the counterclaim of discovery by the Sofia 1868 expedition to the Kara Sea is invalid based on three notable facts: (1) Sofia never sailed in the Kara Sea; (2) the single bottom sediment sample with an extremely high content of Mn (24%), was collected in the Kara Sea during the Vega Expedition across the Northeast Passage; (3) the Vega sampling was in 1878, not in 1868. Meanwhile, five and a half years prior to the Vega sampling, the first Fe–Mn nodules and crusts were dredged up from the sea floor on 18 February and March 7, 1873 during the Challenger expedition. These findings have been promptly reported and published in May 1873. Thus, the credit for the discovery of ferromanganese nodules in the World Ocean firmly belongs to the Challenger expedition.
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| 5. |
- Björk, Göran, 1956, et al.
(författare)
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Bathymetry and deep-water exchange across the central Lomonosov Ridge at 88°-89°N
- 2007
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Ingår i: Deep-Sea Research I. - : Elsevier BV. ; 54, s. 1197-1208
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Tidskriftsartikel (refereegranskat)abstract
- Seafloor mapping of the central Lomonosov Ridge using a multibeam echo-sounder during the Beringia/Healy–Oden Trans-Arctic Expedition (HOTRAX) 2005 shows that a channel across the ridge has a substantially shallower sill depth than the 2500 m indicated in present bathymetric maps. The multibeam survey along the ridge crest shows a maximum sill depth of about 1870 m. A previously hypothesized exchange of deep water from the Amundsen Basin to the Makarov Basin in this area is not confirmed. On the contrary, evidence of a deep-water flow from the Makarov to the Amundsen Basin was observed, indicating the existence of a new pathway for Canadian Basin Deep Water toward the Atlantic Ocean. Sediment data show extensive current activity along the ridge crest and along the rim of a local Intra Basin within the ridge structure.
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| 6. |
- Björk, Göran, 1956, et al.
(författare)
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Flow of Canadian Basin Deep Water in the Western Eurasian Basin of the Arctic Ocean
- 2010
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Ingår i: Deep Sea Research. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 57:4, s. 577-586
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Tidskriftsartikel (refereegranskat)abstract
- The LOMROG 2007 expedition targeted the previously unexplored southern part of the Lomonosov Ridge north of Greenland together with a section from the Morris Jesup Rise to Gakkel Ridge. The oceanographic data shows that Canadian Basin Deep Water (CBDW) passes the Lomonosov Ridge in the area of the Intra Basin close to the North Pole and then continues along the ridge towards Greenland and further along its northernmost continental slope. The CBDW is clearly evident as a salinity maximum and oxygen minimum at a depth of about 2000 m. The cross slope sections at the Amundsen Basin side of the Lomonosov Ridge and further south at the Morris Jesup Rise show a sharp frontal structure higher up in the water column between Makarov Basin water and Amundsen Basin water. The frontal structure continues upward into the Atlantic Water up to a depth of about 300 m. The observed water mass division at levels well above the ridge crest indicates a strong topographic steering of the flow and that different water masses tend to pass the ridge guided by ridge-crossing isobaths at local topographic heights and depressions. A rough scaling analysis shows that the extremely steep and sharply turning bathymetry of the Morris Jesup Rise may force the boundary current to separate and generate deep eddies.
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| 7. |
- Björk, Göran, 1956, et al.
(författare)
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The deep waters of the Eurasian Basin, Arctic Ocean: Geothermal heat flow, mixing and renewal
- 2006
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Ingår i: Deep-Sea Research Part I-Oceanographic Research Papers. - : Elsevier BV. - 0967-0637. ; 53:7, s. 1253-1271
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Tidskriftsartikel (refereegranskat)abstract
- Hydrographic observations from four separate expeditions to the Eurasian Basin of the Arctic Ocean between 1991 and 2001 show a 300-700 m thick homogenous bottom layer. The layer is characterized by slightly warmer temperature compared to ambient, overlying water masses, with a mean layer thickness of 500 +/- 100 m and a temperature surplus of 7.0 +/- 2 x 10(-3) degrees C. The layer is present in the deep central parts of the Nansen and Amundsen Basins away from continental slopes and ocean ridges and is spatially coherent across the interior parts of the deep basins. Here we show that the layer is most likely formed by convection induced by geothermal heat supplied from Earth's interior. Data from 1991 to 1996 indicate that the layer was in a quasi steady state where the geothermal heat supply was balanced by heat exchange with a colder boundary. After 1996 there is evidence of a reformation of the layer in the Amundsen Basin after a water exchange. Simple numerical calculations show that it is possible to generate a layer similar to the one observed in 2001 in 4-5 years, starting from initial profiles with no warm homogeneous bottom layer. Limited hydrographic observations from 2001 indicate that the entire deep-water column in the Amundsen Basin is warmer compared to earlier years. We argue that this is due to a major deep-water renewal that occurred between 1996 and 2001. (c) 2006 Elsevier Ltd. All rights reserved.
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| 8. |
- Chambault, Philippine, et al.
(författare)
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The Gulf Stream frontal system : A key oceanographic feature in the habitat selection of the leatherback turtle?
- 2017
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Ingår i: Deep Sea Research Part I. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 123, s. 35-47
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Tidskriftsartikel (refereegranskat)abstract
- Although some associations between the leatherback turtle Dermochelys coriacea and the Gulf Stream current have been previously suggested, no study has to date demonstrated strong affinities between leatherback movements and this particular frontal system using thorough oceanographic data in both the horizontal and vertical dimensions. The importance of the Gulf Stream frontal system in the selection of high residence time (HRT) areas by the North Atlantic leatherback turtle is assessed here for the first time using state-of-the-art ocean reanalysis products. Ten adult females from the Eastern French Guianese rookery were satellite tracked during post-nesting migration to relate (1) their horizontal movements to physical gradients (Sea Surface Temperature (SST), Sea Surface Height (SSH) and filaments) and biological variables (micronekton and chlorophyll a), and (2) their diving behaviour to vertical structures within the water column (mixed layer, thermocline, halocline and nutricline). All the turtles migrated northward towards the Gulf Stream north wall. Although their HRT areas were geographically remote (spread between 80-30 degrees W and 28-45 degrees N), all the turtles targeted similar habitats in terms of physical structures, i.e. strong gradients of SST, SSH and a deep mixed layer. This close association with the Gulf Stream frontal system highlights the first substantial synchronization ever observed in this species, as the HRTs were observed in close match with the autumn phytoplankton bloom. Turtles remained within the enriched mixed layer at depths of 38.5 +/- 7.9 m when diving in HRT areas, likely to have an easier access to their prey and maximize therefore the energy gain. These depths were shallow in comparison to those attained within the thermocline (82.4 +/- 5.6 m) while crossing the nutrient-poor subtropical gyre, probably to reach cooler temperatures and save energy during the transit. In a context of climate change, anticipating the evolution of such frontal structure under the influence of global warming is crucial to ensure the conservation of this vulnerable species.
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| 9. |
- Cranston, Alex, et al.
(författare)
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A population specific mitochondrial intron from the sponge Phakellia robusta in the North-East Atlantic
- 2021
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Ingår i: Deep Sea Research Part I. - : Elsevier. - 0967-0637 .- 1879-0119. ; 172
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Tidskriftsartikel (refereegranskat)abstract
- Self-splicing mitochondrial introns are a rarely reported phenomenon in animals, with a sparse and uneven distribution confined to some species of sponges, corals, placozoans, and a single species of annelid. Here, we describe a mitochondrial intron present only in some populations of Phakellia robusta, a sponge distributed across the North-east Atlantic deep-sea. The mitochondrial intron of P. robusta was detected in the position 387 of the COI gene and classified as a Group I intron of class IB. Interestingly, this intron was only detected in the shallower populations of P. robusta from Ireland to Norway, spanning 1000 km and was absent in deeper samples of the species. Such deeper populations have recently been proposed to be the result of hybridization between P. robusta and its congeneric Phakellia hirondellei. We propose that this past hybridization might be behind the absence of the intron in the specimens of P. robusta occurring at deep waters. Our analyses indicate that the intron detected in P. robusta might have a double origin (most likely fungi and other organism), as it has previously suggested for the sponge Stupenda singularis. BLAST searches produced matches with the homing endonuclease gene (HEG) nested within the S. singularis intron and this HEG belongs to the family of LAGLIDADG homing endonucleases (LHEs). The evolutionary relevance of the presence/absence of this intron for this species needs to be determined and potential adaptive advantages should not be ruled out.
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| 10. |
- Dahlgren, Thomas G., 1963, et al.
(författare)
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Fauna of whale falls: systematics and ecology of a new polychaete (Annelida : Chrysopetalidae) from the deep Pacific Ocean
- 2004
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Ingår i: Deep-Sea Research Part I-Oceanographic Research Papers. - : Elsevier BV. - 0967-0637. ; 51:12, s. 1873-1887
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Tidskriftsartikel (refereegranskat)abstract
- Vigtorniella flokati, a new species of polychaete worm associated with decaying whale remains, is described. Three separate V. flokati populations were sampled using submersibles: two associated with implanted gray whale carcasses in the San Diego Trough (1240 m depth) and the Santa Cruz Basin (1670 m) off California, and one from sperm whale and balaeanopterid bones implanted on the slope of Oahu, Hawaii at 1000 m. Extraordinarily large numbers of live specimens were observed and videotaped in situ using submersibles in the San Diego Trough and the Santa Cruz Basin. The populations on the carcass implanted for 4 months in San Diego Trough, and on the bones implanted for 2 years off Oahu, were composed only of small sized individuals (including juveniles). V. flokati most closely resembles the poorly known V. zaikai Kiseleva, 1992, described from the Black Sea. Forty-six morphological characters were used in a phylogenetic analysis of selected nereidiform polychaetes. The resulting most-parsimonious trees indicate sister taxon status between V. flokati and V. zaikai, and that this clade is sister to the putatively ancient polychaete clade Chrysopetalidae. Whale falls, which are intense point sources of organic enrichment at the deep-sea floor, pass through three successional stages. V flokati appears to colonize the middle, "enrichment opportunist" stage, inhabiting organic-rich bones and sediments similar to4-24 months after carcass arrival. V. flokati exhibits remarkable behavior, clinging posteriorly to whale bones or nearby sediments to form a writhing carpet at densities exceeding 8000 m(-2). Its extraordinary abundance on whale falls, and apparent absence from other habitats, suggests it to be a whale-fall specialist. The precise feeding mechanism of the worm remains unknown, but we hypothesize that it may utilize dissolved organic carbon derived from the organic-rich setting of whale falls. The widespread occurrence of V. flokati on ephemeral, food-rich habitat islands in the Pacific suggests life-history strategies analogous to those for hydrothermal-vent and cold-seep species. (C) 2004 Elsevier Ltd. All rights reserved.
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| 11. |
- Darelius, E., et al.
(författare)
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Downward flow of dense water leaning on a submarine ridge
- 2007
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Ingår i: Deep Sea Research Part I. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 54:7, s. 1173-1188
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Tidskriftsartikel (refereegranskat)abstract
- Large-scale dense bottom currents are geostrophic to leading order, with the main flow direction along the continental slope. Bottom friction makes the water descend to greater depths, but only at a small angle to the horizontal. Here the effect of a submarine ridge that intersects the slope is considered. It is shown that the presence of a submarine ridge greatly enhances the downward transport. By leaning against the ridge it is possible for the dense water to flow downhill, perpendicular to the depth contours, even though the first-order dynamics are geostrophic. The requirement for downward flow next to the ridge is that the frictional transport that it induces is sufficiently large to counteract geostrophic advection along the isobaths and out of the ridge region. The dynamics are similar to those of downward flow in submarine canyons, but ridges appear to be more effective in channeling the dense water downhill, in particular for narrow ridges/canyons with small seaward slope of the ridge/canyon axis. The downward flow is analyzed using a simplified analytical model and the results are compared to data from the Filchner Overflow, which agree qualitatively with the model.
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| 12. |
- Eerkes-Medrano, Dafne, et al.
(författare)
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A community assessment of the demersal fish and benthic invertebrates of the Rosemary Bank Seamount marine protected area (NE Atlantic)
- 2020
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Ingår i: Deep Sea Research Part I. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0967-0637 .- 1879-0119. ; 156
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Tidskriftsartikel (refereegranskat)abstract
- The Rosemary Bank Seamount in the NE Atlantic was designated a Marine Protected Area in 2014 by the Scottish Government. Visual and trawl surveys of the seamount have been undertaken since 2007. Here these data are compiled and analysed to provide an assessment of the communities of demersal fish and benthic invertebrates found there. The fish and benthic invertebrate communities changed markedly with depth. Cluster analysis revealed at least four distinct communities of fish: those on the summit, the mid slope, the lower slope and the deep moat at the base of the seamount. The invertebrate community changed at a depth of 1100 m, where mixed-species sponge aggregations dominated to depths of 1500 m. The seamount is an important site for vulnerable marine ecosystems, most notably the extensive and unusually diverse deep-sea sponge grounds on the lower slope. Other prioritised conservation species and habitats recorded included cold water corals, orange roughy, blue ling, leafscale gulper shark and the Portuguese dogfish. Due to sampling constraints some areas of the seamount still remain unknown. A precautionary approach to protecting the entire seamount would achieve multiple conservation objectives. The data presented here serve as a base-line to assess the impact of management intervention in the future.
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| 13. |
- Giongo, Adriana, et al.
(författare)
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Discovery of a chemosynthesis-based community in the western South Atlantic Ocean
- 2016
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Ingår i: Deep Sea Research Part I. - : Elsevier. - 0967-0637 .- 1879-0119. ; 112, s. 45-56
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Tidskriftsartikel (refereegranskat)abstract
- Chemosynthetic communities have been described from a variety of deep-sea environments across the world's oceans. They constitute very interesting biological systems in terms of their ecology, evolution and biogeography, and also given their potential as indicators of the presence and abundance of consistent hydrocarbon-based nutritional sources. Up to now such peculiar biotic assemblages have not been reported for the western South Atlantic Ocean, leaving this large region undocumented with respect to the presence, composition and history of such communities. Here we report on the presence of a chemosynthetic community off the coast of southern Brazil, in an area where high-levels of methane and the presence of gas hydrates have been detected. We performed metagenomic analyses of the microbial community present at this site, and also employed molecular approaches to identify components of its benthic fauna. We conducted phylogenetic analyses comparing the components of this assemblage to those found elsewhere in the world, which allowed a historical assessment of the structure and dynamics of these systems. Our results revealed that the microbial community at this site is quite diverse, and contains many components that are very closely related to lineages previously sampled in ecologically similar environments across the globe. Anaerobic methanotrophic (ANME) archaeal groups were found to be very abundant at this site, suggesting that methane is indeed an important source of nutrition for this community. In addition, we document the presence at this site of a vestimentiferan siboglinid polychaete and the bivalve Acharax sp., both of which are typical components of deep-sea chemosynthetic communities. The remarkable similarity in biotic composition between this area and other deep-sea communities across the world supports the interpretation that these assemblages are historically connected across the global oceans, undergoing colonization from distant sites and influenced by local ecological features that select a stereotyped suite of specifically adapted organisms. (C) 2015 Elsevier Ltd. All rights reserved.
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| 14. |
- Glud, R. N., et al.
(författare)
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Distribution of oxygen in surface sediments from central Sagami Bay, Japan: In situ measurements by microelectrodes and planar optodes
- 2005
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Ingår i: Deep Sea Research Part I: Oceanographic Research Papers. - 0967-0637. ; 51:10, s. 1974-1987
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Tidskriftsartikel (refereegranskat)abstract
- Distributions of oxygen in surface sediments from central Sagami Bay were quantified using an autonomous vehicle carrying both a profiling microelectrode instrument and a planar optode module. Measurements were performed at 16 sites (either by microelectrodes or optodes) along a 175 m long transect and in total 45 electrode microprofiles and 6 O2 images (each covering 6.9×5.1 cm of surface sediment) were obtained. The data revealed an extensive small-scale variation of the in situ O2 distribution. The diffusive O2 uptake (DOU) as derived from the microelectrode data varied by a factor >10 with an average value of 2.6±1.6 mmol m−2 d−1 (n=45) corresponding to 8% of the estimated average primary production for the area. There was no significant difference in the average O2 penetration depth as quantified from the microprofiles and the planar optode images (P<0.05). The O2 penetration depth of the combined dataset varied between 0.5 and 9.2 mm with an average value of 3.9±1.5 mm (n=347). Even though the organic carbon rich sediments of central Sagami Bay may exhibit higher horizontal heterogeneity than normally encountered in deep-sea sediments, the data document that extrapolation from a few in situ data points should be done with caution. A detailed statistical analysis of the spatial autocorrelation in the O2 penetration depth documented that measurements performed less than 2 cm apart were autocorrelated. This implies that the aerobic benthic activity at the investigated site varied in patches with a characteristic size of a few cm. The presented data represent a detailed in situ study on small-scale spatial variability in sediment O2 distribution and document that planar O2 optode images provide a tool to access spatial heterogeneity of natural sediments.
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| 15. |
- Graham, Robert M., et al.
(författare)
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Identifying sources and transport pathways of iron in the Southern Ocean
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Ingår i: Deep Sea Research Part I. - 0967-0637 .- 1879-0119.
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Tidskriftsartikel (refereegranskat)abstract
- Over large regions of the global ocean primary productivity is limited by the availability of dissolved iron. Changes in the supply of iron to these regions could have major impacts on primary productivity and the carbon cycle. One of the largest sources of dissolved iron to the ocean is thought to be from shelf sediments, and this source is often parameterized in biogeochemical models as a depth dependent iron flux through the seafloor. Using the knowledge that Southern Ocean surface waters are iron limited, we infer source regions of iron to the Southern Ocean by identifying where the most intense chlorophyll blooms develop. We further derive surface current patterns from satellite sea surface height fields to assess the role of the ocean circulation in transporting iron away from these source regions. We find a tight relationship between satellite chlorophyll concentrations and sea surface height. Large chlorophyll blooms develop on the shelf and where the western boundary currents detach from the continental shelves and turn eastward into the Southern Ocean. This is likely due to shelf supplied iron becoming entrained into western boundary currents and advected into the Southern Ocean along the Dynamical Subtropical Front. The most intense chlorophyll blooms are located along coastal margins of islands and continents. Blooms do not develop over submerged seamounts or plateaus in the open ocean. This suggests that shelf sediments in coastal regions act as large bioavailable iron sources to the Southern Ocean. We recommend that a more accurate method of parameterizing the shelf sediment iron flux could be to prescribe this flux only through grid cells neighboring coastlines. Finally, we hypothesize how changes in sea level during glacial-interglacial cycles may have altered the distribution of shelf sediment iron sources in the Southern Ocean and helped to drive export production anomalies in the Sub-Antarctic Zone.
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| 16. |
- Graham, Robert M., et al.
(författare)
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Inferring source regions and supply mechanisms of iron in the Southern Ocean from satellite chlorophyll data
- 2015
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Ingår i: Deep Sea Research Part I. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 104, s. 9-25
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Tidskriftsartikel (refereegranskat)abstract
- Primary productivity is limited by the availability of iron over large areas of the global ocean. Changes in the supply of iron to these regions could have major impacts on primary productivity and the carbon cycle. However, source regions and supply mechanisms of iron to the global oceans remain poorly constrained. Shelf sediments are considered one of the largest sources of dissolved iron to the global ocean, and a large shelf sediment iron flux is prescribed in many biogeochemical models over all areas of bathymetry shallower than 1000 m. Here, we infer the likely location of shelf sediment iron sources in the Southern Ocean, by identifying where satellite chlorophyll concentrations are enhanced over shallow bathymetry (< 1000 m). We further compare chlorophyll concentrations with the position of ocean fronts, to assess the relative role of horizontal advection and upwelling for supplying iron to the ocean surface. We show that mean annual chlorophyll concentrations are not visibly enhanced over areas of shallow bathymetry that are located more than 500 km from a coastline. Mean annual chlorophyll concentrations > 2 mg m(-3) are only found within 50 km of a continental or island coastline. These results suggest that sedimentary iron sources only exist on continental and island shelves. Large sedimentary iron fluxes do not seem present on seamounts and submerged plateaus. Large chlorophyll blooms develop where the western boundary currents detach from the continental shelves, and turn eastward into the Sub-Antarctic Zone. Chlorophyll concentrations are enhanced along contours of sea surface height extending off the continental shelves, as shown by the trajectories of virtual water parcels in satellite altimetry data. These analyses support the hypothesis that bioavailable iron from continental shelves is entrained into western boundary currents, and advected into the Sub-Antarctic Zone along the Dynamical Subtropical Front. Our results indicate that upwelling at fronts in the open ocean is unlikely to deliver iron to the ocean surface from deep sources. Finally, we hypothesise how a reduction in sea level may have altered the distribution of shelf sediment iron sources in the Southern Ocean and increased export production over the Sub-Antarctic Zone during glacial intervals.
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| 17. |
- Gustafsson, Örjan, et al.
(författare)
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Th-234-derived surface export fluxes of POC from the Northern Barents Sea and the Eurasian sector of the Central Arctic Ocean
- 2012
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Ingår i: Deep Sea Research Part I. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 68, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Settling-based surface ocean export of particulate organic carbon (POC) in the western Eurasian sector of the Arctic Ocean was investigated from the marginal ice zone (MIZ) of the northern Barents Sea to the North Pole area. Upper ocean profiles of POC were combined with corresponding dissolved and particulate Th-234 activities measured with a low-volume at-sea direct beta counting protocol to constrain the Th-234-derived POC export in July and August of 2001 to 6-32 mmol m(-2) d(-1) for the Barents Sea MIZ dropping to 2-6 mmol m(-2) d(-1) for multi-year-ice (MYI) covered central Arctic stations in Nansen, Amundsen and Makarov basins. Secular equilibrium between Th-234 and U-238 activities in intermediate to deep waters in the Amundsen Basin (n=10) demonstrated that the at-sea measurement protocol was functioning satisfactorily. There was no distinction in POC export efficiency between the MIZ and the MYI-covered interior basins with an average ratio between Th-234-derived POC export and primary production (so-called ThE ratio) of 44%. A projected increase in primary production with retreat in areal extent of sea ice is thus likely to yield increased POC sequestration in the Arctic Ocean interior.
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| 18. |
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| 19. |
- Havenhand, Jonathan N., 1959, et al.
(författare)
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Megalodicopia hians in the Monterey submarine canyon: Distribution, larval development, and culture
- 2006
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Ingår i: Deep-Sea Research Part I-Oceanographic Research Papers. - : Elsevier BV. - 0967-0637. ; 53:2, s. 215-222
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Tidskriftsartikel (refereegranskat)abstract
- The exclusively deep-sea ascidian family Octacnemidae comprises several genera in which the oral siphon has hypertrophied to form two large lips which create an "oral hood" capable of capturing motile prey. Megalodicopia hians is typical of this carnivorous family and has been reported to prey upon small epibenthic crustaceans. Distribution of M. hians in the Monterey Canyon system (36 degrees 45'N, 122 degrees 00'W) (California) was determined with remotely operated vehicles. M hians was found sparsely to depths of at least 3800m throughout the canyon; however, abundance was greatest within the oxygen-minimum zone (400-800m). Eggs, sperm, and recently fertilized embryos were obtained repeatedly from adults returned to the laboratory in vivo, indicating that this species free-spawns routinely. Overall egg diameter (ovum plus chorion, plus follicle cells) was 175-190 mu m-considerably smaller than previously reported for this species. Embryonic development at temperature and oxygen concentrations equivalent to the oxygen-minimum zone was 2-4d and. embryos gave rise to typical phlebobranch "simple" tadpole larvae. Larval period was extremely variable, and settlement/metamorphosis occurred up to 3 months post-hatching. These results are discussed within the context of settlement-site selection and fertilization ecology of the species. (c) 2005 Elsevier Ltd. All rights reserved.
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| 20. |
- Henry, L. A., et al.
(författare)
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Global ocean conveyor lowers extinction risk in the deep sea
- 2014
-
Ingår i: Deep Sea Research Part I: Oceanographic Research Papers. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 88, s. 8-16
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Tidskriftsartikel (refereegranskat)abstract
- General paradigms of species extinction risk are urgently needed as global habitat loss and rapid climate change threaten Earth with what could be its sixth mass extinction. Using the stony coral Lophelia pertusa as a model organism with the potential for wide larval dispersal, we investigated how the global ocean conveyor drove an unprecedented post-glacial range expansion in Earth's largest biome, the deep sea. We compiled a unique ocean-scale dataset of published radiocarbon and uranium-series dates of fossil corals, the sedimentary protactinium-thorium record of Atlantic meridional overturning circulation (AMOC) strength, authigenic neodymium and lead isotopic ratios of circulation pathways, and coral biogeography, and integrated new Bayesian estimates of historic gene flow. Our compilation shows how the export of Southern Ocean and Mediterranean waters after the Younger Dryas 11.6 kyr ago simultaneously triggered two dispersal events in the western and eastern Atlantic respectively. Each pathway injected larvae from refugia into ocean currents powered by a re-invigorated AMOC that led to the fastest postglacial range expansion ever recorded, covering 7500 km in under 400 years. In addition to its role in modulating global climate, our study illuminates how the ocean conveyor creates broad geographic ranges that lower extinction risk in the deep sea. (C) 2014 The Authors. Published by Elsevier Ltd.
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| 21. |
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| 22. |
- Iversen, Morten Hvitfeldt, et al.
(författare)
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High resolution profiles of vertical particulate organic matter export off Cape Blanc, Mauritania : Degradation processes and ballasting effects
- 2010
-
Ingår i: Deep Sea Research Part I. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 57:6, s. 771-784
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Tidskriftsartikel (refereegranskat)abstract
- Vertical carbon fluxes between the surface and 2500 m depth were estimated from in situ profiles of particle size distributions and abundances me/asured off Cape Blanc (Mauritania) related to deep ocean sediment traps. Vertical mass fluxes off Cape Blanc were significantly higher than recent global estimates in the open ocean. The aggregates off Cape Blanc contained high amounts of ballast material due to the presence of coccoliths and fine-grained dust from the Sahara desert, leading to a dominance of small and fast-settling aggregates. The largest changes in vertical fluxes were observed in the surface waters (<250 m), and, thus, showing this site to be the most important zone for aggregate formation and degradation. The degradation length scale (L), i.e. the fractional degradation of aggregates per meter settled, was estimated from vertical fluxes derived from the particle size distribution through the water column. This was compared with fractional remineralization rate of aggregates per meter settled derived from direct ship-board measurements of sinking velocity and small-scale 02 fluxes to aggregates measured by micro-sensors. Microbial respiration by attached bacteria alone could not explain the degradation of organic matter in the upper ocean. Instead, flux feeding from zooplankton organisms was indicated as the dominant degradation process of aggregated carbon in the surface ocean. Below the surface ocean, microbes became more important for the degradation as zooplankton was rare at these depths.
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| 23. |
- Jonasdottir, Sigrun Huld, et al.
(författare)
-
Biological oceanography across the Southern Indian Ocean - basin scale trends in the zooplankton community
- 2013
-
Ingår i: Deep Sea Research Part I. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 75, s. 16-27
-
Tidskriftsartikel (refereegranskat)abstract
- We present a study on the protozooplankton > 5 mu m and copepods larger than 50 mu m at a series of contrasting stations across the Southern Indian Ocean (SIO). Numerically, over 80% of the copepod community across the transect was less than 650 mu m in size, dominated by nauplii, and smaller copepods, while 80% of the biomass (as mg C m(-3)) was larger than 1300 mu m in body length. Predation by the carnivorous copepod Corycaeus sp. was estimated to be able to remove up to 2% d(-1) of the copepods < 1000 mu m in size. By the help of grazing models we estimated that primary producers were mainly grazed upon by ciliates and heterotrophic dinoflagellates (40-80% d(-1) combined) in temperate waters but appendicularians became increasingly important in the tropical waters grazing about 40% of the biomass per day. Despite their high abundance and biomass, copepods contributed less than 20% of the grazing at most stations. Secondary production was low (carbon specific egg production < 0.14 d(-1)) but typical for food limited oligotrophic oceans.
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| 24. |
- Kanhai, La Daana K., et al.
(författare)
-
Deep sea sediments of the Arctic Central Basin: A potential sink for microplastics
- 2019
-
Ingår i: Deep-Sea Research Part I: Oceanographic Research Papers. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 145, s. 137-142
-
Tidskriftsartikel (refereegranskat)abstract
- Deep sea sediments have emerged as a potential sink for microplastics in the marine environment. The discovery of microplastics in various environmental compartments of the Arctic Central Basin (ACB) suggested that these contaminants were potentially being transported to the deep-sea realm of this oceanic basin. For the first time, the present study conducted a preliminary assessment to determine whether microplastics were present in surficial sediments from the ACB. Gravity and piston corers were used to retrieve sediments from depths of 855-4353 m at 11 sites in the ACB during the Arctic Ocean 2016 (AO16) expedition. Surficial sediments from the various cores were subjected to density flotation with sodium tungstate dihydrate solution (Na2WO4 center dot 2H(2)O, density 1.4 g cm(-3)). Potential microplastics were isolated and analysed by Fourier Transform Infrared (FT-IR) spectroscopy. Of the surficial samples, 7 of the 11 samples contained synthetic polymers which included polyester (n = 3), polystyrene (n = 2), polyacrylonitrile (n = 1), polypropylene (n = 1), polyvinyl chloride (n = 1) and polyamide (n = 1). Fibres (n = 5) and fragments (n = 4) were recorded in the samples. In order to avoid mis-interpretation, these findings musi be taken in the context that (i) sampling equipment did not guarantee retrieval of undisturbed surficial sediments, (ii) low sample volumes were analysed (similar to 10 g per site), (iii) replicate sediment samples per site was not possible, (iv) no air contamination checks were included during sampling and, (v) particles < 100 mu m were automatically excluded from analysis. While the present study provides preliminary indication that microplastics may be accumulating in the deep-sea realm of the ACB, further work is necessary to assess microplastic abundance, distribution and composition in surficial sediments of the ACB.
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| 25. |
- Kivimae, Caroline, et al.
(författare)
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A carbon budget for the Barents Sea
- 2010
-
Ingår i: DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS. - 0967-0637. ; 57:12, s. 1532-1542
-
Tidskriftsartikel (refereegranskat)
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| 26. |
- Lin, Yi-Tao, et al.
(författare)
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Phylogenetic placement, morphology and gill-associated bacteria of a new genus and species of deep-sea mussel (Mytilidae: Bathymodiolinae) from the South China Sea
- 2022
-
Ingår i: Deep Sea Research Part I. - Amsterdam : Elsevier. - 0967-0637 .- 1879-0119. ; 190, s. 103894-103894
-
Tidskriftsartikel (refereegranskat)abstract
- Mussels in the subfamily Bathymodiolinae are common inhabitants of deep-sea chemosynthetic habitats, but in many places their diversity remains unknown. Here we describe Nypamodiolus samadiae n. gen. et n. sp. (Mytilidae: Bathymodiolinae) based on samples collected from the Haima cold seep in the South China Sea. Phylogenetic analyses based on fragments of three mitochondrial (cox1, 16S rRNA and nad4) and three nuclear (18S rRNA, 28S rRNA and histone H3) genes show that this new species belongs to a new genus, Nypamodiolus, which includes three named species (Myrina longissima Thiele and Jaeckel, 1931, Myrina simpsoni Marshall, 1900, Idasola japonica Habe, 1976) and a few undescribed species. Nypamodiolus n. gen. is characterized by small-sized, modioliform to fan-shaped shells with the umbones in a non-terminal position, and by robust anterior and posterior byssal retractor muscles arranged in roughly one plane. Most closely related to Nypamodiolus samadiae n. sp. is an undescribed species from the northern Papua New Guinea, to which it has a Kimura-2-parameter genetic distance of 11.8% for cox1. Sequencing the V3–V4 region of the microbial 16S rRNA gene reveals two dominant gill-associated bacteria in the new species, including one sulfur-oxidizing Gammaproteobacteria (relative abundance: 43.8–58.8%) and one unclassified Spirochaetes (relative abundance: 23.9–28.1%). Morphologically, N. samadiae n. sp. is similar to N. simpsoni, while can be distinguished by a larger maximum shell size (45.0 mm vs. 40.0 mm), larger length/height ratio (2.6–2.9 vs. 2.1–2.4), broader posterior end, slightly curved dorsal margin, and more anterior umbones.
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| 27. |
- Olsson, Anders, 1970, et al.
(författare)
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Intermediate water from the Greenland Sea in the Faroe Bank Channel: spreading of released sulphur hexafluoride
- 2005
-
Ingår i: Deep-Sea Research Part I: Oceanographic Research Papers. - : Elsevier BV. - 0967-0637. ; 52:2, s. 279-294
-
Tidskriftsartikel (refereegranskat)abstract
- The Faroe Bank Channel is the deepest passage for dense water leaving the Nordic Seas into the North Atlantic. The contribution to this part of the Greenland-Scotland Overflow by intermediate water from the Greenland Sea is investigated by the tracer sulphur hexafluoride (SF6) that was released into the central Greenland Sea in summer 1996. Continuous monitoring has since traced it around the Nordic Seas and into the connecting areas. It was observed for the first time close to the Faroe Islands in early 1999, indicating a transport time from the Greenland Sea of around 2.5 years. This study estimates that approximately 16 kg of SF6 had passed the Faroe Bank Channel by the end of 2002, that is 5% of the total amount released. Both the arrival time and the amount of exported SF6 deduced from the observations are consistent with the results from a numerical ocean model simulating the tracer release and spreading.
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| 28. |
- Raj, Roshin P., et al.
(författare)
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The Lofoten Vortex of the Nordic Seas
- 2015
-
Ingår i: Deep Sea Research Part I. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 96, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 29. |
- Rebesco, M., et al.
(författare)
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Quaternary contourite drifts of the Western Spitsbergen margin
- 2013
-
Ingår i: Deep-Sea Research Part I-Oceanographic Research Papers. - : Elsevier BV. - 0967-0637. ; 79, s. 156-168
-
Tidskriftsartikel (refereegranskat)abstract
- The study of contourite drifts is an increasingly used tool for understanding the climate history of the oceans. In this paper we analyse two contourite drifts along the continental margin west of Spitsbergen, just south of the Fram Strait where significant water mass exchanges impact the Arctic climate. We detail the internal geometry and the morphologic characteristics of the two drifts on the base of multichannel seismic reflection data, sub-bottom profiles and bathymetry. These mounded features, that we propose to name Isfjorden and Bellsund drifts, are located on the continental slope between 1200 and 1800 m depth, whereas the upper slope is characterized by reduced- or non-deposition. The more distinct Isfjorden Drift is about 25 km wide and 45 km long, and over 200 ms TWT thick. We revise the 13 years-long time series of velocity, temperature, and salinity obtained from a mooring array across the Fram Strait. Two distinct current cores are visible in the long-term average. The shallower current core has an average northward velocity of about 20 cm/s, while the deeper bottom current core at about 1450 m depth has an average northward velocity of about 9 cm/s. We consider Norwegian Sea Deep Water episodically ventilated by relatively dense and turbid shelf water from the Barents Sea responsible for the accumulation of the contourites. The onset of the drift growth west of Spitsbergen is inferred to be about 1.3 Ma and related to the Early Pleistocene glacial expansion recorded in the area. The lack of mounded contouritic deposits on the continental slope of the Storfjorden is related to consecutive erosion by glacigenic debris flows. The Isfjorden and Bellsund drifts are inferred to contain the record of the regional palaeoceanography and glacial history and may constitute an excellent target of future scientific drilling. (C) 2013 Elsevier Ltd. All rights reserved.
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| 30. |
- Siegel, Volker, et al.
(författare)
-
Distribution and abundance of Antarctic krill (Eupausia superba) along the Antarctic Peninsula
- 2013
-
Ingår i: Deep Sea Research Part I: Oceanographic Research Papers. - : Elsevier BV. - 0967-0637. ; 77, s. 63-74
-
Tidskriftsartikel (refereegranskat)abstract
- Net-based data on the abundance, distribution, and demographic patterns of Antarctic krill are quantified from a contemporaneous two ship survey of the Antarctic Peninsula during austral summer 2011. Two survey areas were sampled focussed on Marguerite Bay in the south, and the tip of the Antarctic Peninsula in the north. Data from 177 stations showed that the highest concentrations of krill were found in the southern sampling area. Differences between areas were associated with a few large catches of one year old krill found in anomalously warm and productive waters in Marguerite Bay, and small krill catches in the less-productive, offshore waters in the north. Estimated krill density across the survey area was 3.4 krill m−2, and was low compared to the long-term average of 45 krill m−2 for the Elephant Island area. Overall recruitment between the two survey regions was similar, but per capita recruitment was about 60% lower than historical mean recruitment levels measured at Elephant Island since the late 1970s. Demographic patterns showed small krill concentrated near the coast, and large krill concentrated offshore on the shelf and slope all along the survey area. The offshore distribution of adult krill was delineated by the warm (∼1 °C), low salinity (33.8) water at 30 m, suggesting that most krill were present shoreward of the southern boundary of Antarctic Circumpolar Current Front. Distributions of larvae indicated that three hotspot areas were important for the production of krill: slope areas outside Marguerite Bay and north of the South Shetland Islands, and near the coast around Antarctic Sound. Successful spawning, as inferred from larval abundance, was roughly coincident with the shelf break and not with inshore waters. Given the rapid changes in climate along the Antarctic Peninsula and the lower per capita recruitment observed in recent years, studies comparing and contrasting production, growth, and recruitment across the Peninsula will be critical to better understand how climate change will impact krill populations and their dependent predators in the Scotia Sea.
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| 31. |
- Taboada, Sergi, et al.
(författare)
-
Genetic diversity, gene flow and hybridization in fan-shaped sponges (Phakellia spp.) in the North-East Atlantic deep sea
- 2022
-
Ingår i: Deep Sea Research Part I. - : Elsevier. - 0967-0637 .- 1879-0119. ; 181
-
Tidskriftsartikel (refereegranskat)abstract
- Deep-sea North Atlantic sponge grounds are crucial components of the marine fauna providing a key role in ecosystem functioning. To properly develop effective conservation and management plans, it is crucial to understand the genetic diversity, molecular connectivity patterns and turnover at the population level of the species involved. Here we present the study of two congeneric sponges, Phakellia robusta and Phakellia hirondellei, using multiple sources of evidence. Our phylogenetic study using a fragment of COI placed these two species as sister. Haplotype network analysis using COI revealed no genetic structure for P. hirondellei in samples from the Cantabrian Sea (<100 km). Contrastingly, P. robusta showed a clear genetic structure separating deep-water samples from the Cantabrian Sea and the Hatton-Rockall Basin, from samples from shallower waters from Kerry Head Reefs, NW of Orkney, and Norway. ddRADseq-derived SNPs for P. robusta also segregated samples by bathymetry rather than by geographical distances, and detected a predominant northwards migration for shallow-water specimens connecting sites separated ca. 2,000 km, probably thanks to prevalent oceanographic currents. Importantly, our analysis using SNPs combining the datasets of the two species revealed the presence of potential hybrids, which was corroborated by morphological (spicule) and microbial (16S amplicon sequencing) analyses. Our data suggest that hybridization between these two species occurred at least two times in the past. We discuss the importance of using next-generation techniques to unveil hybridization and the implications of our results for conservation.
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| 32. |
- Taboada, Sergi, et al.
(författare)
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Insights into the symbiotic relationship between scale worms and carnivorous sponges (Cladorhizidae, Chondrocladia)
- 2020
-
Ingår i: Deep Sea Research Part I. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0967-0637 .- 1879-0119. ; 156
-
Tidskriftsartikel (refereegranskat)abstract
- Symbiotic associations between polynoid scale worms and other marine invertebrates are common, but sometimes poorly understood. Compounding this problem is the fact that polynoid systematics is largely unresolved. Here, we transfer the species originally described as Nemidia antillicola chondrocladiae Fauvel (1943), and currently synonymized with Neopolynoe acanellae (Verrill, 1881), to the species Neopolynoe chondrocladiae n. comb. This species is characterized by living in association with the carnivorous sponges Chondrocladia robertballnrdi Cristobo, Rios, Pomponi & Xavier, 2015 and Chondrocladia virgata Thompson, 1873. The existence of specialized chaetae in N. chondrocladiae n. comb. and the occurrence of open galleries in the sponge, derived from a gradual overgrowth of the sponge to accommodate the worm, suggest an obligate symbiotic relationship between worm and sponge. The presence of a gravid female with relatively small oocytes (maximum diameter 56.94 +/- 14.89 mu m) suggests that N. chondrocladiae n. comb. is a gonochoristic broadcaster with a planktotrophic larva, a means of reproduction that would maximize the chances of this species finding new suitable hosts to colonize. We also provide a phylogenetic placement, using four genetic markers (18S, 28S, 16S and COI), for N. chondrocladiae n. comb. and N. acanellae, which confirms they are two different species. In addition, we also report here the occurrence of another deep-water polynoid species in association with the carnivorous sponge Chondrocladia vertical= Topsent, 1920, from the Gulf of Mexico, and place it in a phylogeny.
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| 33. |
- Turnewitsch, Robert, et al.
(författare)
-
Internal tides and sediment dynamics in the deep sea : Evidence from radioactive 234Th/238U disequilibria
- 2008
-
Ingår i: Deep-Sea Research. Part I: Oceanographic Research Papers. - : Elsevier BV. - 0967-0637. ; 55:12, s. 1727-1747
-
Tidskriftsartikel (refereegranskat)abstract
- Residual flow, barotropic tides and internal (baroclinic) tides interact in a number of ways with kilometer-scale seafloor topography such as abyssal hills and seamounts. Because of their likely impact on vertical mixing such interactions are potentially important for ocean circulation and the mechanisms and the geometry of these interactions are a matter of ongoing studies. In addition, very little is known about how these interactions are reflected in the sedimentary record. This multi-year study investigates if flow / topography interactions are reflected in distributional patterns of the natural short-lived (half life: 24.1 d) particulate-matter tracer 234Th relative to its conservative (non-particle-reactive) and very long-lived parent nuclide 238U. The sampling sites were downstream of, or surrounded by, fields of short seamounts and, therefore, very likely to be influenced by nearby flow / topography interactions. Between about 200 m and 1000 m above the seafloor at the sampling sites recurrent ‘fossil’ disequilibria were detected. ‘Fossil’ disequilibria are defined by clearly detectable 234Th/238U disequilibria (total 234Th radioactivity < 238U radioactivity, indicating a history of intense particulate 234Th scavenging and particulate-matter settling from the sampled parcel of water) and conspicuously low particle-associated 234Th activities. ‘Fossil’ disequilibria were centered around levels in the water column which correspond to the average height of the short seamounts near the sampling sites. This suggests the ‘fossil’ disequilibria are formed on the seamount slopes. Moreover, the magnitude of the ‘fossil’ disequilibria suggests that the slopes of the short seamounts in the study region are characterized by particularly vigorous fluid dynamics. Since ‘fossil’ disequilibria already occurred at ~ O(1 – 10 km) away from the seamount slopes it is likely that these vigorous fluid dynamics rapidly decay away from the slopes on scales of O(1 ? 10 km). These conclusions are supported by the horizontal distribution and magnitude of the modeled total (barotropic + baroclinic) tidal current velocities of the predominating tidal M2 constituent: On (near?)critical seamount slopes baroclinic tides lead to localized [~ O(1 km)] increases of the overall tidal current velocity by a factor of ~ 2, thereby pushing the total current velocity well above the threshold for sediment erosion. The results of this and a previous study (Turnewitsch et al. 2004, Earth and Planetary Science Letters 222, 1023-1036) show that kilometer-scale flow / topography interactions leave a marine geochemical imprint which may help to develop sediment proxies for the reconstruction of past changes of fluid dynamics in the deep sea, particularly the internal wave field. Sites with (near?)critical seafloor slopes are the most promising sites to study paleo-changes of internal tides. To reconstruct the paleo-flow of residual currents and barotropic tides, sediments covering isolated topography of comparable breadth and width, and with sub-critical slopes, seem to be more appropriate. For the sediment-based reconstruction of paleo-parameters other than physical oceanographic ones kilometer-scale topography should be avoided altogether.Residual flow, barotropic tides and internal (baroclinic) tides interact in a number of ways with kilometer-scale seafloor topography such as abyssal hills and seamounts. Because of their likely impact on vertical mixing such interactions are potentially important for ocean circulation and the mechanisms and the geometry of these interactions are a matter of ongoing studies. In addition, very little is known about how these interactions are reflected in the sedimentary record. This multi-year study investigates if flow / topography interactions are reflected in distributional patterns of the natural short-lived (half life: 24.1 d) particulate-matter tracer 234Th relative to its conservative (non-particle-reactive) and very long-lived parent nuclide 238U. The sampling sites were downstream of, or surrounded by, fields of short seamounts and, therefore, very likely to be influenced by nearby flow / topography interactions. Between about 200 m and 1000 m above the seafloor at the sampling sites recurrent ‘fossil’ disequilibria were detected. ‘Fossil’ disequilibria are defined by clearly detectable 234Th/238U disequilibria (total 234Th radioactivity < 238U radioactivity, indicating a history of intense particulate 234Th scavenging and particulate-matter settling from the sampled parcel of water) and conspicuously low particle-associated 234Th activities. ‘Fossil’ disequilibria were centered around levels in the water column which correspond to the average height of the short seamounts near the sampling sites. This suggests the ‘fossil’ disequilibria are formed on the seamount slopes. Moreover, the magnitude of the ‘fossil’ disequilibria suggests that the slopes of the short seamounts in the study region are characterized by particularly vigorous fluid dynamics. Since ‘fossil’ disequilibria already occurred at ~ O(1 – 10 km) away from the seamount slopes it is likely that these vigorous fluid dynamics rapidly decay away from the slopes on scales of O(1 ? 10 km). These conclusions are supported by the horizontal distribution and magnitude of the modeled total (barotropic + baroclinic) tidal current velocities of the predominating tidal M2 constituent: On (near?)critical seamount slopes baroclinic tides lead to localized [~ O(1 km)] increases of the overall tidal current velocity by a factor of ~ 2, thereby pushing the total current velocity well above the threshold for sediment erosion. The results of this and a previous study (Turnewitsch et al. 2004, Earth and Planetary Science Letters 222, 1023-1036) show that kilometer-scale flow / topography interactions leave a marine geochemical imprint which may help to develop sediment proxies for the reconstruction of past changes of fluid dynamics in the deep sea, particularly the internal wave field. Sites with (near?)critical seafloor slopes are the most promising sites to study paleo-changes of internal tides. To reconstruct the paleo-flow of residual currents and barotropic tides, sediments covering isolated topography of comparable breadth and width, and with sub-critical slopes, seem to be more appropriate. For the sediment-based reconstruction of paleo-parameters other than physical oceanographic ones kilometer-scale topography should be avoided altogether.
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| 34. |
- Turnewitsch, Robert, et al.
(författare)
-
Recent sediment dynamics in hadal trenches : Evidence for the influence of higher-frequency (tidal, near-inertial) fluid dynamics
- 2014
-
Ingår i: Deep Sea Research Part I. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 90, s. 125-138
-
Tidskriftsartikel (refereegranskat)abstract
- In addition to high hydrostatic pressure, scarcity of food is viewed as a factor that limits the abundance and activity of heterotrophic organisms at great ocean depths, including hadal trenches. Supply of nutritious food largely relies on the flux of organic-rich particulate matter from the surface ocean. It has been speculated that the shape of hadal trenches helps to 'funnel' particulate matter into the deeper parts of the trench, leading to sediment 'focussing' and improved benthic food supply. Here we investigate for five Northwest Pacific trenches the efficiency of sediment focussing by evaluating ratios of measured (sediment-derived) and expected (water-column-derived) sedimentary inventories of the naturally occurring and radioactive particulate-matter tracer Pb-210(xs). The sites comprise a broad range of surface-ocean productivity and physical-oceanographic regimes. Across the five trench-axis settings the inventory ratio varies between 0.5 and 4.1, with four trench-axis settings having ratios > 1 (sediment focussing) and one trench-axis setting a ratio < 1 (sediment winnowing). Although the fluid- and sediment-dynamical forcing behind sediment focussing remains unclear, this study finds evidence for another mechanism that is superimposed on, and counteracts, the focussing mechanism. This superimposed mechanism is related to higher-frequency (tidal, near-inertial) fluid dynamics. In particular, there is evidence for a strong and negative relation between the intensity of propagating internal tides and the extent of sediment focussing in the trench-axis. The relation can be approximated by a power function and the most intense drop in sediment focussing already occurs at moderate internal-tide intensities. This suggests that propagating internal tides may have a subtle but significant influence on particulate-matter dynamics and food supply in hadal trenches in particular, but possibly also in the deep seas in general. A mechanism for the influence of internal tides on sediment dynamics is proposed.
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| 35. |
- Verdugo, Josefa, et al.
(författare)
-
Climate relevant trace gases (N2O and CH4) in the Eurasian Basin (Arctic Ocean)
- 2016
-
Ingår i: Deep Sea Research Part I. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 117, s. 84-94
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Tidskriftsartikel (refereegranskat)abstract
- The concentration of greenhouse gases, including nitrous oxide (N2O), methane (CH4), and compounds such as total dimethylsulfoniopropionate (DMSP), along with other oceanographic variables were measured in the ice covered Arctic Ocean within the Eurasian Basin (EAB). The EAB is affected by the perennial ice-pack and has seasonal microalgal blooms, which in turn may stimulate microbes involved in trace gas cycling. Data collection was carried out on board the LOMROG III cruise during the boreal summer of 2012. Water samples were collected from the surface to the bottom layer (reaching 4300 m depth) along a South-North transect (SNT), from 82.19 degrees N, 8.75 degrees E to 89.26 degrees N, 58.84 degrees W, crossing the EAB through the Nansen and Amundsen Basins. The Polar Mixed Layer and halocline waters along the SNT showed a heterogeneous distribution of N2O, CH4 and DMSPt, fluctuating between 42-111 and 27-649% saturation for N2O and CH4, respectively; and from 3.5 to 58.9 nmol L-1 for DMSPt. Spatial patterns revealed that while CH4 and DMSPt peaked in the Nansen Basin, N2O was higher in the Amundsen Basin. In the Atlantic Intermediate Water and Arctic Deep Water N2O and CH4 distributions were also heterogeneous with saturations between 52% and 106% and 28% and 340%, respectively. Remarkably, the Amundsen Basin contained less CH4 than the Nansen Basin and while both basins were mostly under-saturated in N2O. We propose that part of the CH4 and N2O may be microbiologically consumed via methanotrophy, denitrification, or even diazotrophy, as intermediate and deep waters move throughout EAB associated with the overturning water mass circulation. This study contributes to baseline information on gas distribution in a region that is increasingly subject to rapid environmental changes, and that has an important role on global ocean circulation and climate regulation.
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- Westerberg, Håkan
(författare)
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Evidence of marine mammal predation of the European eel. (Anguilla anguilla L.) on its marine migration
- 2014
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Ingår i: Deep Sea Research Part I: Oceanographic Research Papers. - : Elsevier BV. - 0967-0637 .- 1879-0119. ; 86, s. 32-38
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Tidskriftsartikel (refereegranskat)abstract
- Temperature and depth logging tags were implanted into adult eels released on Atlantic west coasts of France and Ireland to study their oceanic migration behavior. For three of the tags, 25 to 256 days after release there was a dramatic rise in temperature from 10 degrees C to 36 degrees C and the dive profile changed from depths of 300-1000 m to repeated ascents to the surface. This indicated that the eels carrying the tags had been eaten by a mammalian predator. Two of the tags had sufficient sampling rate to resolve the dives in detail. They recorded a total of 91 dives to maximum depths of 250-860 m lasting 11-12 min and with surface intervals of 5-7 min. More than two thirds of the dives included a rapid descent from approximately 500 m to 600-700 m. From this we infer that the predator was most likely a deep-diving toothed whale. The dives logged while the tags were inside the predator revealed that the temperature usually decreased during dives, and increased again during surface periods. The temperature drops during dives were probably caused by the ingestion of prey or water. These observations provide insights into the behavior of toothed whales foraging in the mesopelagic zone. (C) 2014 Elsevier Ltd. All rights reserved.
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