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  • Other Sources  (281)
  • Taylor & Francis  (174)
  • AMS (American Meteorological Society)  (97)
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  • 2015-2019  (165)
  • 1990-1994  (96)
  • 1980-1984  (15)
  • 1970-1974  (5)
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  • 1
    Publication Date: 2021-04-23
    Description: Climate change has significant implications for biodiversity and ecosystems. With slow progress towards reducing greenhouse gas emissions, climate engineering (or ‘geoengineering’) is receiving increasing attention for its potential to limit anthropogenic climate change and its damaging effects. Proposed techniques, such as ocean fertilization for carbon dioxide removal or stratospheric sulfate injections to reduce incoming solar radiation, would significantly alter atmospheric, terrestrial and marine environments, yet potential side-effects of their implementation for ecosystems and biodiversity have received little attention. A literature review was carried out to identify details of the potential ecological effects of climate engineering techniques. A group of biodiversity and environmental change researchers then employed a modified Delphi expert consultation technique to evaluate this evidence and prioritize the effects based on the relative importance of, and scientific understanding about, their biodiversity and ecosystem consequences. The key issues and knowledge gaps are used to shape a discussion of the biodiversity and ecosystem implications of climate engineering, including novel climatic conditions, alterations to marine systems and substantial terrestrial habitat change. This review highlights several current research priorities in which the climate engineering context is crucial to consider, as well as identifying some novel topics for ecological investigation.
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  • 2
    Publication Date: 2019-02-01
    Description: The surface chemistry of aquatic organisms determines their biotic interactions. Metabolites in the spatially limited laminar boundary layer mediate processes, such as antifouling, allelopathy and chemical defense against herbivores. However, very few methods are available for the investigation of such surface metabolites. An approach is described in which surfaces are extracted by means of C18 solid phase material. By powdering wet algal surfaces with this material, organic compounds are adsorbed and can be easily recovered for subsequent liquid chromatography/mass spectrometry (LC/MS) and gas chromatography/mass spectrometry (GC/MS) investigations. The method is robust, picks up metabolites of a broad polarity range and is easy to handle. It is more universal compared to established solvent dipping protocols and it does not cause damage to the test organisms. A protocol is introduced for the macroalgae Fucus vesiculosus, Caulerpa taxifolia and Gracilaria vermiculophylla, but it can be easily transferred to other aquatic organisms.
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  • 3
    Publication Date: 2020-01-02
    Description: Different studies on the position of the non-indigenous species Neogobius melanostomus within the coastal food web of the Pomeranian Bay (western Baltic) were performed, resulting in a quantitative and qualitative species list of prey organisms found in the stomachs of the invader and an estimation concerning the importance of round goby as prey for different resident predators. It seems that the colonization process is not fully completed yet, but the results reveal that the species is already established in the food web 16 years after the first observation within the study area. The results show that N. melanostomus feed upon a wide range of different resident organisms. While a direct predation effect on native fish species appears rather unlikely, indirect effects such as competition cannot yet be excluded. In addition, our results reveal an ontogenetic diet shift and that the round goby itself already serves as an important prey for piscivorous fish and seabirds. Finally, we formulate different hypotheses based on our results which will require further research.
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  • 4
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    Taylor & Francis
    In:  South African Journal of Marine Science, 9 (1). pp. 11-26.
    Publication Date: 2020-05-26
    Description: The biology of the chokker squid Loligo vulgaris reynaudii on inshore grounds in the South-East Cape was studied by examination of trends in jig catches, length frequency analyses, length/weight relationships, analyses of maturity stages and SCUBA diving transects in a spawning area. Commercial catches probably reflected the influx of squid into shallow waters to spawn. Modal length at spawning was between 265 and 305 mm mantle length (ML) in males and between 175 and 195 mm ML in females. There was no modal progression to indicate growth, nearly all squid were mature, a percentage of males were spent, the level of feeding on the grounds was very low, and mantle walls were thinner than those of squid offshore. These factors all indicate that the squid population inshore had reached the end of its life cycle and was in the spawning phase. The sex ratio was biased towards males, an indication either of differential inshore migration or of greater longevity in males than in females. The frequency of occurrence of trawled egg capsules was highest in summer and all eggs were between 18 and 25 m deep. The preferred substratum for spawning appeared to be low-relief reef interspersed with coarse sand, and the stalks of egg capsules were always embedded in the sand to form individual clusters, as in most other loliginids. No evidence was found of post-spawning mortality in the areas examined.
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  • 5
    Publication Date: 2020-02-06
    Description: International Ocean Discovery Program (IODP) Expedition 352 recovered a high-fidelity record of volcanism related to subduction initiation in the Bonin fore-arc. Two sites (U1440 and U1441) located in deep water nearer to the trench recovered basalts and related rocks; two sites (U1439 and U1442) located in shallower water further from the trench recovered boninites and related rocks. Drilling in both areas ended in dolerites inferred to be sheeted intrusive rocks. The basalts apparently erupted immediately after subduction initiation and have compositions similar to those of the most depleted basalts generated by rapid sea-floor spreading at mid-ocean ridges, with little or no slab input. Subsequent melting to generate boninites involved more depleted mantle and hotter and deeper subducted components as subduction progressed and volcanism migrated away from the trench. This volcanic sequence is akin to that recorded by many ophiolites, supporting a direct link between subduction initiation, fore-arc spreading, and ophiolite genesis.
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  • 6
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    Taylor & Francis
    In:  Invertebrate Reproduction & Development, 19 (1). pp. 13-24.
    Publication Date: 2017-02-01
    Description: Oogenesis in four commercial Caribbean sponge species, Hippospongia lachne, Spongia barbara, S. cheiris and S. graminea, was studied using light and transmission electron microscopy. Eggs and embryos develop asynchronously in localized endosomal nurseries of these viviparous and gonochoristic species. Statistical analyses of specific morphological characteristics of reproductive elements have unequivocally identified four specific stages in the process of oogenesis. Oogonia undergo mitotic division to produce primary oocytes. Meiotic division occurs producing secondary oocytes which are fertilized before zygotes undergo major growth by phagocytosis and the transfer of nutrients through cytoplasmic bridges. During cleavage of the zygote, umbilici form between embryos and nurse cell layers and these function in the transfer of symbiotic bacteria and other mesohyl substances from the maternal parent to the embryo. These symbionts were observed dispersed between blastomeres of all young and maturing embryos and between internal cells of cytodifferentiated parenchymella larvae. Extracellular transfer of symbiotic bacteria from maternal tissues to developing embryos has not been reported in any other viviparous invertebrate.
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  • 7
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    Taylor & Francis
    In:  New Zealand Journal of Marine and Freshwater Research , 25 . pp. 275-282.
    Publication Date: 2020-06-22
    Description: Before 1985, Martialia hyadesi (Cephalopoda: Ommastrephidae) in the Pacific Ocean was known only from the Eltanin Fracture Zone and Macquarie Island. A joint Japan‐New Zealand squid survey around New Zealand captured many immature ommastrephid squids. Gel electrophoresis confirmed the presence of immature M. hyadesi. Aspects of the external morphology are described. The distinctive tentacle club was evident in the smallest specimen examined, 19 mm dorsal mantle length (ML). Arm trabeculae were first evident in specimens of 40–50 mm ML. Immature squid were distributed around and southward of the Subtropical Convergence Zone. The presence of very small squid (〈 10 mm ML) indicated spawning on or near the Auckland Island Shelf.
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  • 8
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    Taylor & Francis
    In:  Journal of the Royal Society of New Zealand, 22 (4). pp. 243-263.
    Publication Date: 2020-07-16
    Description: The beaks of 9,994 cephalopods of 61 species, obtained mainly from chick regurgitations of wandering albatrosses (Diomedea exulans L.) at Gough, Auckland, Antipodes, Prince Edward and Macquarie Islands and South Georgia, were used to specify and calculate the biomass of cephalopods consumed. Histioteuthidae were most important by numbers and biomass at Gough Island (in warmest seas), but Onycboteuthidae increasingly superseded them southwards; Kondakovia longimana formed 59 to 75% of biomass eaten at the three localities nearest the Antarctic Polar Front. Other important families were Octopoteuthidae, Cranchiidae, Architeuthidae (juveniles) and Ommastrephidae (South Georgia only). Most frequently eaten were Histioteuthis atlantica 13.7%, Galiteuthis glacialis 12.4%, H. eltaninae 12.0% and Kondakovia longimana 11.6%. Wandering albatrosses rearing chicks can forage at least to 3,000 km in a single foray, and may exploit an important food source about 1200 km from the nest (as in the probable commensalism of South Georgian birds with the Falkland Islands fishery). They feed, sometimes opportunistically, on cephalopods active or moribund at the surface, or discarded or lost by trawlers, cetaceans or seals. Vertically migrating cephalopods, especially bioluminescent species, are disproportionately frequent in their non-commensal diet, suggesting that they often feed at night.
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  • 9
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    Taylor & Francis
    In:  South African Journal of Marine Science, 12 (1). pp. 225-235.
    Publication Date: 2020-05-26
    Description: A link is proposed between the processes that led to the evolution of large species of squid and the highly variable, cyclic recruitment seen in squid fisheries. Maximum growth requires maximal feeding and minimal routine metabolism at optimum temperatures, which decrease as squid grow. Topographically induced upwelling zones, inshore of western boundary currents, provide productive environments with appropriate temperatures for all life stages. Most squid are small and live in the tropics or subtropics; locomotor constraints prevent them from swimming long distances. Long annual migrations to spawn upstream in current systems require short-lived squids to maximize rates of growth. Therefore, such systems provide the opportunity and a powerful selective advantage for large size and rapid growth. Increased fecundity and cannibalism provide additional directional selection for large individuals. Current systems show food production peaks (blooms); paralarval release must match these to increase survival. Because squid are semelparous, disruption of delicately balanced lifecycles by physical events can virtually annihilate stocks. Recovery probably requires that populations of large squid "re-evolve" from smaller, more-stable tropical populations of small squid. This recovery phase may extend the "down-side" of abundance cycles. Studies of squid/current systems have focused on western boundary currents, but the Illex complex also associates with eastern boundaries. Such populations are generally smaller than in larger systems, supporting the hypothesis, but more detailed comparisons are required.
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  • 10
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    Taylor & Francis
    In:  South African Journal of Marine Science, 12 (1). pp. 739-752.
    Publication Date: 2020-05-26
    Description: During a cruise in March 1988 dedicated to investigation of the marine resources of South Africa's continental slope, 62 species in 22 families of Cephalopoda were collected from the Cape Canyon and Cape Point Valley. Multivariate analysis revealed a clear distinction between cephalopods of the upper and lower continental slope in both benthic and epibenthic habitats. Todaropsis eblanae and Todarodes angolensis were indicator species for the upper slope benthic, from 300 to 500 m, but on the lower slope, in 700–900 m of water, they were replaced by Histioteuthis miranda and Opisthoteuthis agassizii. In the epibenthic, both upper and lower slopes were dominated by Abraliopsis gilchristi and Lycoteuthis ?diadema, but other species characteristic of the lower slope were the oceanic species Mastigoteuthis hjorti, Ctenopteryx sicula and Taonius sp. A. Cranchia scabra indicated the presence of oceanic water at stations 700–900 m deep. Other species of significance in the catches were Todarodes filippovae, Histioteuthis macrohista, Rossia enigmatica and Bathypolypus valdiviae. Species affinities indicate that the cephalopod fauna of the southern African continental slope includes the following zoogeographic components: southern African endemic, circum-Subantarctic species associated with Antarctic Intermediate Water, circum-global southern tropical/subtropical, tropical Indo-Pacific and cosmopolitan tropical/subtropical.
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  • 11
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    Taylor & Francis
    In:  South African Journal of Marine Science, 12 (1). pp. 651-662.
    Publication Date: 2020-05-26
    Description: Literature on trophic relationships in the Benguela ecosystem has stressed the importance of cephalopods as prey of groundfish. The groundfish community of the shelf and upper slope of southern Africa is dominated by the Cape hakes, and the results presented (1984–1991) confirm that both species of hake are important predators of cephalopods, especially taking into consideration the abundance of hake in the ecosystem. However, geographic, seasonal and species variability are evident in the patterns observed. The main prey species are Sepia spp. (predominantly Sepia australis), Loligo vulgaris reynaudii, Todaropsis eblanae and Lycoteuthis ?diadema. The last-named is an important food organism for fish. Its systematic status needs revision, however. Qualitative results of studies of cephalopod predation are also provided for kingklip and monkfish.
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  • 12
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    Taylor & Francis
    In:  South African Journal of Marine Science, 12 (1). pp. 791-802.
    Publication Date: 2020-05-26
    Description: Cephalopods of importance in the Benguela ecosystem include Loligo vulgaris reynaudii, Todarodes angolensis, Todaropsis eblanae, Lycoteuthis ?diadema, Sepia australis, Octopus spp. (up to three species) and Argonauta spp., and possibly also Ocythoe tuberculata and Rossia enigmatica. Species which may prove important as a result of further research are Lolliguncula mercatoris, Ommastrephes bartramii, Todarodes filippovae, Histioteuthis miranda and Abraliopsis gilchristi. "Importance" is defined on the basis of "survey abundance" (including commercial fisheries) and their trophic links with other organisms. Use of the latter criterion indicates that Sepia australis, Todaropsis eblanae and Lycoteuthis ?diadema are sufficiently abundant to be exploited by fisheries. Unknown factors are dispersal, availability and market considerations. The only examples of cephalopods feeding on commercial species of fish are Loligo v. reynaudii feeding on anchovy Engraulis capensis and Cape hakes Merluccius capensis and/or M. paradoxus in the southern Benguela and Todarodes angolensis preying on Cape hake in the northern Benguela. Such feeding is opportunistic and is not believed to threaten the fish stocks. Predators of cephalopods are mostly opportunistic, switching to other prey when cephalopods are not available. There is no evidence that such predators pose a threat to the Loligo fisheries. The opportunistic nature of cephalopods as prey and predators makes quantification of predation (in both directions) difficult. Data for such quantification are, as yet, unavailable.
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  • 13
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    Taylor & Francis
    In:  Journal of Natural History, 27 (1). pp. 15-46.
    Publication Date: 2020-07-21
    Description: The present study contributes new information on the cephalopods off Namibia, contains the first record of Ornithoteuthis volatilis (Sasaki, 1915) in the Atlantic, and adds records of six species in the Benguela Current and three species in Namibian waters. The presence of certain species seldom encountered in the Benguela Current has been confirmed. A compilation of the cephalopod fauna off Namibia had also been included, listing 65 species. Additional morphological data on Stoloteuthis leucoptera, Lycoteuthis lorigera, Architeuthis sp., Pholidoteuthis boschmai, Ornithoteuthis volatilis, Eledone nigra, and Graneledone sp. have been provided. The status of the genus Lycoteuthis has been reviewed in the light of the first collection of Lycoteuthis lorigera (Steenstrup, 1875) males in the Atlantic, and Lycoteuthis diadema (Chun, 1900) has been considered to be a synonym for Lycoteuthis lorigera
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  • 14
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    Taylor & Francis
    In:  South African Journal of Marine Science, 12 (1). pp. 927-941.
    Publication Date: 2020-05-26
    Description: The results of ichthyoplankton surveys carried out by the Instituto Nacional de Pesca (INAPE) in the Argentine–Uruguayan Common Fishing Zone (AUCFZ) in summer 1980 and the winters of 1980–1982 are presented. In addition, the results of joint research with INIDEP, the Argentine and Japan Fisheries Agency, on larvae, juveniles and adults of the short-finned squid Illex argentinus carried out in winter 1989 are given, as are data obtained during the joint sardine and anchovy recruitment project carried out by R.V. Meteor in November/December 1989. The short-finned squid Illex argentinus is the most important cephalopod resource of the area, and an extended fishery is carried out on the Patagonian shelf and in the proximity of the Falkland Islands. The fishing season in the AUCFZ, for pre-spawning and spawning animals, extends from early autumn to winter (March–August). Abundance of rhynchoteuthion larvae (417–485 larvae·10 m−2) was greatest in winter in surface temperatures of 12,1–16,9°C and surface salinities of 34,8 – 35,2 × 10−3. The distribution of the larvae is related to the western boundary of the Brazil Current and the convergence front.
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  • 15
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    Taylor & Francis
    In:  South African Journal of Marine Science, 12 (1). pp. 903-918.
    Publication Date: 2020-05-26
    Description: The question whether the chokka squid Loligo vulgaris reynaudii resource can be managed effectively is examined in the light of developments in the fishery and knowledge of the resource gathered in recent years. The history of the fishery since its inception in 1985, management controls and the current state of knowledge of stock identity, distribution, seasonality and abundance, life cycle and population dynamics are reviewed as a background to a discussion of management alternatives. Long-term measures, such as fleet limitation, seasonal closures and de facto closed areas and size limits, all appropriate in the early stages of a fishery when knowledge is limited, should be replaced by more-flexible alternatives as knowledge improves. Methods of stock assessment, stock-recruitment studies and further basic biological analyses are recognized as being crucial to improving management methods. An explanation embracing physical oceanographic features and plankton productivity in the vicinity of the spawning grounds is advanced for the mechanisms underlying hatchling survival. The possible contribution of trophic studies to squid management is recognized. Effective management of the chokka squid resource is concluded to be possible provided that the specific areas needing attention be addressed by means of goal-orientated research. Rational, but not necessarily optimal, management decisions can, however, be made even in the absence of stock-recruitment data, by the employment of common-sense measures which generally include some form of effort control.
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  • 16
    Publication Date: 2020-02-06
    Description: The production of shiga toxin (Stx) is a critical step in the establishment and progress of enterohemorrhagic Escherichia coli (EHEC) infections. The possible release of Stx from dead and dying bacteria, and the risk of resistance development have restricted the usage of antibiotics against EHEC. The chlorinated quaternary ammonium compound, strepthonium A, was isolated from the culture of Streptomyces sp. SBT345 that was cultivated from the Mediterranean sponge Agelas oroides. The structure was elucidated and confirmed by spectroscopic analyses including 1D and 2D NMR, ESI-HRMS, as well as ESI-HRMS2. Strepthonium A follows Lipinski's rule of five with respect to its molecular weight, CLogP values and the number of hydrogen acceptors and donors. Verotoxin ELISA assay demonstrated that Strepthonium A reduced the Stx production in EHEC strain EDL933 at 80 μM concentration without growth inhibition. This study demonstrates the potential of strepthonium A in restraining the production of Stx in EHEC infections.
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  • 17
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    Taylor & Francis
    In:  Journal of Maps, 13 (1). pp. 24-30.
    Publication Date: 2020-02-06
    Description: Land-use dynamic is a major challenge for town and country planners especially in developing countries such as Iran. Iran has been under rapid urban expansion and population growth for past three decades which led to lack of resources, environmental deterioration and haphazard landscape development. In this paper, an attempt has been made to map the urbanization dynamics of Tehran in 40 years based on remote sensing imagery and by means of artificial neural networks. The presented scheme could be taken into consideration when planning initiatives aimed at surveying, monitoring, managing and sustainable development of the territory. Moreover, it can serve the experts in the fields of geography, urban studies and planning as a background for number of geographical analyses.
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  • 18
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    Taylor & Francis
    In:  Israel Journal of Zoology, 39 (4). pp. 299-336.
    Publication Date: 2017-08-10
    Description: During the years 1989–1993 an intensive collection of fishes from the aphotic zone (below 150 m) of the northern part of the Gulf of Aqaba was conducted. This survey recorded 69 fish species, 8 elasmobranchs, and 61 teleosts, belonging to 45 families. Fifteen species are endemic to the Red Sea: Mustelus mosis, Narcine bentuviai, Rhinobatos punctifer, Ophichthus echeloides, Rhynchoconger sp., Physiculus marisrubri, Ostichthys hypsipterygion sufensis, Pterygotrigla sp., Uranoscopus marisrubri, Parascolopsis sp.1 and sp. 2, Atrobucca geniae, Chromis pelloura, Samariscus sp., Thamnaconus modestoides erythraeensis. Eleven species are new records for the Red Sea: Gymnothorax johnsoni, Rhynchoconger sp., Synodus doaki, Pterygotrigla sp., Chelidoperca pleurospilus, Carangoides equula, Parascolopsis sp. 1 and sp. 2, Bodianus leucostictus, Paracaesio sordidus, and Samariscus sp. Two species, Cociella crocodilo and Parascolopsis eriomma, are first substantiated records for the Red Sea. None of the species recorded in this list is considered conventional deep-sea fishes. The ichthyofauna of the aphotic zone of the Gulf of Aqaba is composed of species of shallower origin.
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  • 19
    Publication Date: 2020-02-06
    Description: Current antifouling (AF) technologies are based on the continuous release of biocides into the water, and consequently discharge into the environment. Major efforts to develop more environmentally friendly coatings require efficient testing in laboratory assays, followed by field studies. Barnacles are important fouling organisms worldwide, increasing hydrodynamic drag on ships and damaging coatings on underwater surfaces, and thus are extensively used as models in AF research, mostly in static, laboratory-based systems. Reliable flow-through test assays for the screening of biocide-containing AF paints, however, are rare. Herein, a flow-through bioassay was developed to screen for diverse low-release biocide paints, and to evaluate their effects on pre- and post-settlement traits in barnacles. The assay distinguishes between the effects from direct surface contact and bulk-water effects, which are crucial when developing low-emission AF coatings. This flow-through bioassay adds a new tool for rapid laboratory-based first-stage screening of candidate compounds and novel AF formulations.
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  • 20
    Publication Date: 2020-02-06
    Description: Arctic sea ice area (SIA) during late summer and early fall decreased substantially over the last four decades, and its decline accelerated beginning in the early 2000s. Statistical analyses of observations show that enhanced poleward moisture transport from the North Pacific to the Arctic Ocean contributed to the accelerated SIA decrease during the most recent period. As a consequence, specific humidity in the Arctic Pacific sector significantly increased along with an increase of downward longwave radiation beginning in 2002, which led to a significant acceleration in the decline of SIA in the Arctic Pacific sector. The resulting sea ice loss led to increased evaporation in the Arctic Ocean, resulting in a further increase of the specific humidity in mid-to-late fall, thus acting as a positive feedback to the sea ice loss. The overall set of processes is also found in a long control simulation of a coupled climate model.
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  • 21
    Publication Date: 2019-02-01
    Description: One new diterpene, trichocitrin (1), and four known secondary metabolites, nafuredin (2), 5-hydroxy-2,3-dimethyl-7-methoxychromone (3), 24-methylenecycloartanol (4) and citrostadienol (5), were isolated from the culture of marine brown alga-endophytic Trichoderma citrinoviride cf-27. Trichocitrin (1) represents the first Trichoderma-derived and furan-bearing fusicoccane diterpene, and its structure and relative configuration were identified by analysis of 1D/2D NMR and mass spectroscopic data. Compounds 1 and 2 exhibited 8.0- and 9.5-mm inhibition zones, respectively, against Escherichia coli at 20 μg/disc and 54.1 and 36.7% growth inhibition, respectively, of Prorocentrum donghaiense at 80 μg/mL.
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  • 22
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    AMS (American Meteorological Society)
    In:  Journal of Climate, 30 (22). pp. 9321-9337.
    Publication Date: 2020-08-04
    Description: In the present study, the influence of some major tropical modes of variability on northern hemisphere regional blocking frequency variability during boreal winter is investigated. Reanalysis data and an ensemble experiment with the ECMWF model using relaxation towards the ERA-Interim reanalysis data inside the tropics are used. The tropical modes under investigation are El Niño Southern Oscillation (ENSO), the Madden-Julian Oscillation (MJO) and the upper tropospheric equatorial zonal-mean zonal wind . An early (late) MJO phase refers to the part of the MJO cycle when enhanced (suppressed) precipitation occurs over the western Indian Ocean and suppressed (enhanced) precipitation occurs over the Maritime Continent and the western tropical Pacific. Over the North Pacific sector, it is found that enhanced (suppressed) high latitude blocking occurs in association with El Niño (La Niña) events, late (early) MJO phases and westerly (easterly) . Over central to southern Europe and the east Atlantic, it is found that late MJO phases, as well as a suppressed MJO are leading to enhanced blocking frequency. Furthermore, early (late) MJO phases are followed by blocking anomalies over the western North Atlantic region, similar to those associated with a positive (negative) North Atlantic Oscillation. Over northern Europe, the easterly (westerly) phase of is associated with enhanced (suppressed) blocking. These results are largely confirmed by both the reanalysis and the model experiment.
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  • 23
    Publication Date: 2021-02-08
    Description: New biostratigraphical, geochemical, and magnetic evidence is synthesized with IODP Expedition 352 shipboard results to understand the sedimentary and tectono-magmatic development of the Izu–Bonin outer forearc region. The oceanic basement of the Izu–Bonin forearc was created by supra-subduction zone seafloor spreading during early Eocene (c. 50–51 Ma). Seafloor spreading created an irregular seafloor topography on which talus locally accumulated. Oxide-rich sediments accumulated above the igneous basement by mixing of hydrothermal and pelagic sediment. Basaltic volcanism was followed by a hiatus of up to 15 million years as a result of topographic isolation or sediment bypassing. Variably tuffaceous deep-sea sediments were deposited during Oligocene to early Miocene and from mid-Miocene to Pleistocene. The sediments ponded into extensional fault-controlled basins, whereas condensed sediments accumulated on a local basement high. Oligocene nannofossil ooze accumulated together with felsic tuff that was mainly derived from the nearby Izu–Bonin arc. Accumulation of radiolarian-bearing mud, silty clay, and hydrogenous metal oxides beneath the carbonate compensation depth (CCD) characterized the early Miocene, followed by middle Miocene–Pleistocene increased carbonate preservation, deepened CCD and tephra input from both the oceanic Izu–Bonin arc and the continental margin Honshu arc. The Izu–Bonin forearc basement formed in a near-equatorial setting, with late Mesozoic arc remnants to the west. Subduction-initiation magmatism is likely to have taken place near a pre-existing continent–oceanic crust boundary. The Izu–Bonin arc migrated northward and clockwise to collide with Honshu by early Miocene, strongly influencing regional sedimentation.
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  • 24
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    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 48 (4). pp. 757-771.
    Publication Date: 2021-02-08
    Description: The Eddy Kinetic Energy (EKE) associated with the Subtropical Countercurrent (STCC) in the western subtropical South Pacific is known to exhibit substantial seasonal and decadal variability. Using an eddy-permitting ocean general circulation model, which is able to reproduce the observed, salient features of the seasonal cycles of shear, stratification, baroclinic production and the associated EKE, we investigate the decadal changes of EKE. We show that the STCC region exhibits, uniquely among the subtropical gyres of the world’s oceans, significant, atmospherically forced, decadal EKE variability. The decadal variations are driven by changing vertical shear between the STCC in the upper 300 m and the South Equatorial Current below, predominantly caused by variations in STCC strength associated with a changing meridional density gradient. In the 1970s, an increased meridional density gradient results in EKE twice as large as in later decades in the model. Utilizing sensitivity experiments, decadal variations in the wind field are shown to be the essential driver. Local wind stress curl anomalies associated with the Interdecadal Pacific Oscillation (IPO) lead to up- and downwelling of the thermocline, inducing strengthening or weakening of the STCC and the associated EKE. Additionally, remote wind stress curl anomalies in the eastern subtropical South Pacific, which are not related to the IPO, generate density anomalies that propagate westward as Rossby waves and can account for up to 30–40 % of the density anomalies in the investigated region.
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  • 25
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    AMS (American Meteorological Society)
    In:  Bulletin of the American Meteorological Society, 98 (8) (8). AMS (American Meteorological Society), Si-S280, 277 pp.
    Publication Date: 2020-10-21
    Type: Report , NonPeerReviewed
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  • 26
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    Taylor & Francis
    In:  Marine Behaviour and Physiology, 7 (1). pp. 15-24.
    Publication Date: 2018-04-18
    Description: Foraging rate was highly variable among shore crabs of the same size category and for individual crabs from day to day. Possible physiological reasons for this variability are discussed. Shore crab foraging rate, both in terms of mussels eaten per day and energy intake per day, was estimated to be higher at 17°C than at 10°C. The shape of diet curves and their mode for male shore crabs at 17°C closely resembled those for 10°C, indicating that the temperature increase had no effect on their previously demonstrated optimal foraging strategy. Female and certain male shore crabs showed a preference for prey smaller than for other equivalent sized males. These suboptimally feeding male and female crabs attained a relatively higher prédation rate (mussels day‐1), although their energy intake (KJ day‐1) remained lower than that of optimally feeding males. Preferred mussel size, number of mussels eaten per day and energy intake were strongly related to master chela height. The diet curves for female and suboptimally feeding male shore crabs could be explained by these crabs’ proportionately smaller master chelae.
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  • 27
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    Taylor & Francis
    In:  Sarsia, 79 (3). pp. 207-283.
    Publication Date: 2018-04-19
    Description: The holoplanktonic family Miraciidae (Copepoda, Harpacticoida) is revised and a key to the four monotypic genera presented. Amended diagnoses are given for Miracia Dana, Oculosetella Dahl and Macrosetella A. Scott, based on complete redescriptions of their respective type species M. efferata Dana, 1849, O. gracilis (Dana, 1849) and M. gracilis (Dana, 1847). A fourth genus Distioculus gen. nov. is proposed to accommodate Miracia minor T. Scott, 1894. The occurrence of two size-morphs of M. gracilis in the Red Sea is discussed, and reliable distribution records of the problematic O. gracilis are compiled. The first nauplius of M. gracilis is described in detail and changes in the structure of the antennule, P2 endopod and caudal ramus during copepodid development are illustrated. Phylogenetic analysis revealed that Miracia is closest to the miraciid ancestor and placed Oculosetella-Macrosetella at the terminal branch of the cladogram. Various aspects of miraciid biology are reviewed, including reproduction, postembryonic development, vertical and geographical distribution, bioluminescence, photoreception and their association with filamentous Cyanobacteria (Trichodesmium).
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  • 28
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    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 23 (8). pp. 1638-1646.
    Publication Date: 2018-03-23
    Description: New light is shed on Worthington's concept of the North Atlantic circulation, postulating the existence of two anticyclonic gyres. This concept, which seems to have been laid to rest in the last decade, has now been reinforced by the results of a simple linear Sverdrup circulation model yielding a band of westward transport all across the North Atlantic at about the Azores latitude. This narrow band is called the Azores Countercurrent (AzCC) and matches the position of westward flow required by Worthington's “northern gyre.” An anomaly in the meridional change of the wind-stress curl in the eastern North Atlantic has been identified as the driving mechanism. A comparison with observations shows that the AzCC is verified in many analyses of historical datasets and synoptic surveys. A lack of the AzCC in other analyses is probably due to missing meridional sections, strong smoothing, and the superimposed Ekman flow close to the sea surface directed to the southeast. The AzCC has not been verified in low-resolution general circulation models applying simplified wind-stress fields and large friction coefficients, but there is evidence for its existence in recent high-resolution models driven by realistic wind stresses. Based on these findings, a new pattern for the wind-driven upper ocean circulation of the midlatitude North Atlantic is presented.
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  • 29
    Publication Date: 2020-02-06
    Description: The Indian Ocean has sustained robust surface warming in recent decades, but the role of multi-decadal variability remains unclear. Using ocean model hindcasts, characteristics of low-frequency Indian Ocean temperature variations are explored. Simulated upper-ocean temperature changes across the Indian Ocean in the hindcast are consistent with those recorded in observational products and ocean reanalyses. Indian Ocean temperatures exhibit strong warming trends since the 1950s limited to the surface and south of 30°S, while extensive subsurface cooling occurs over much of the tropical Indian Ocean. Previous work focused on diagnosing causes of these long-term trends in the Indian Ocean over the second half of the 20th Century. Instead, the temporal evolution of Indian Ocean subsurface heat content is shown here to reveal distinct multi-decadal variations associated with the Pacific Decadal Oscillation and the long-term trends are thus interpreted to result from aliasing of the low-frequency variability. Transmission of the multi-decadal signal occurs via an oceanic pathway through the Indonesian Throughflow and is manifest across the Indian Ocean centered along 12°S as westward propagating Rossby waves modulating thermocline and subsurface heat content variations. Resulting low-frequency changes in the eastern Indian Ocean thermocline depth are associated with decadal variations in the frequency of Indian Ocean Dipole (IOD) events, with positive IOD events unusually common in the 1960s and 1990s with a relatively shallow thermocline. In contrast, the deeper thermocline depth in the 1970s and 1980s is associated with frequent negative IOD and rare positive IOD events. Changes in Pacific wind forcing in recent decades and associated rapid increases in Indian Ocean subsurface heat content can thus affect the basin’s leading mode of variability, with implications for regional climate and vulnerable societies in surrounding countries.
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  • 30
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    Taylor & Francis
    In:  Sarsia, 53 (1). pp. 71-75.
    Publication Date: 2020-05-28
    Description: Sixtytwo species of radiolarians have been found in surface sediment in Lindåspollene. Some of these are common in deep-sea sediments from tropical and subtropical latitudes. These warm-water radiolarians are believed to have been introduced during a warm, postglacial period.
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  • 31
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    In:  Invertebrate Reproduction & Development, 19 (1). pp. 1-11.
    Publication Date: 2017-02-01
    Description: Sexual reproductive cycles of a Florida, U.S.A., population of four Caribbean commercial sponge species, Hippospongia lachne, Spongia barbara, S. cheiris and S. graminea, were determined by analysis of tissue samples collected over a three-year period. Spermatogenesis in these species was studied using light and transmission electron microscopy. The production of male gametes occurs in cysts within the endosomal tissue of mature specimens. Reproductive elements within an individual cyst develop synchronously while development between cysts is asynchronous. All available evidence suggests that these species are dioecious. Spermatogonia differentiate directly from choanocytes in situ. All cells of the chamber lose their collars and flagella and undergo mitosis to produce primary spermatocytes, each possessing a single flagellum. The ratio of nucleus to cell diameter in these cells is almost double that of choanocytes. Circumstantial evidence suggests that primary spermatocytes undergo meiosis to produce four spermatids, but confirmational chromatid linkage figures are still lacking. The mature spermatozoa lack both intermediate segments and acrosomes. Male gametes displayed a bright yellow-white autofluorescence when excited with blue light (460–485 nm).
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  • 32
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    Taylor & Francis
    In:  South African Journal of Marine Science, 10 (1). pp. 193-201.
    Publication Date: 2020-05-26
    Description: Squid on their spawning grounds feed mainly at night when they are more dispersed. In all, 28,5 per cent of squid sampled at night had food in their stomachs, whereas only 6,7 per cent of those collected by day had food. Most stomachs contained only a single prey species (90,8% of those analysed). Teleosts dominated the prey of squid collected at night (58%M), followed by crustaceans (25%), polychaetes (9%) and cephalopods (3%). By day the prey was dominated by cephalopods (61%), followed by teleosts (20%), crustaceans (14%) and polychaetes (2%). Bregmaceros sp. was the most frequently identified teleost, Loligo vulgaris reynaudii (cannibalism) the dominant cephalopod, ?Betaeus sp. (Alpheidae; pieces of coral were also found) the commonest crustacean and Nereis sp. the commonest polychaete. There were seasonal differences in the diet too: squid caught during summer seemed to have similar proportions of the four main prey components. Also, the incidence of feeding was higher than in winter. There were, however, no significant differences in stomach mass expressed as a percentage of body mass between day and night nor between season nor between sexes. The average stomach mass of all samples was 0,6 per cent of body mass, less than on the feeding grounds, where it is generally about 2 per cent.
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  • 33
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    Taylor & Francis
    In:  South African Journal of Marine Science, 12 (1). pp. 927-941.
    Publication Date: 2020-05-26
    Description: The results of ichthyoplankton surveys carried out by the Instituto Nacional de Pesca (INAPE) in the Argentine–Uruguayan Common Fishing Zone (AUCFZ) in summer 1980 and the winters of 1980–1982 are presented. In addition, the results of joint research with INIDEP, the Argentine and Japan Fisheries Agency, on larvae, juveniles and adults of the short-finned squid Illex argentinus carried out in winter 1989 are given, as are data obtained during the joint sardine and anchovy recruitment project carried out by R.V. Meteor in November/December 1989. The short-finned squid Illex argentinus is the most important cephalopod resource of the area, and an extended fishery is carried out on the Patagonian shelf and in the proximity of the Falkland Islands. The fishing season in the AUCFZ, for pre-spawning and spawning animals, extends from early autumn to winter (March–August). Abundance of rhynchoteuthion larvae (417–485 larvae·10 m−2) was greatest in winter in surface temperatures of 12,1–16,9°C and surface salinities of 34,8 – 35,2 × 10−3. The distribution of the larvae is related to the western boundary of the Brazil Current and the convergence front.
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  • 34
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    American Institute of Physics
    In:  The Journal of the Acoustical Society of America, 138 (3). pp. 1253-1267.
    Publication Date: 2020-05-11
    Description: Responses obtained in consonant perception experiments typically show a large variability across stimuli of the same phonetic identity. The present study investigated the influence of different potential sources of this response variability. It was distinguished between source-induced variability, referring to perceptual differences caused by acoustical differences in the speech tokens and/or the masking noise tokens, and receiver-related variability, referring to perceptual differences caused by within- and across-listener uncertainty. Consonant-vowel combinations consisting of 15 consonants followed by the vowel /i/ were spoken by two talkers and presented to eight normal-hearing listeners both in quiet and in white noise at six different signal-to-noise ratios. The obtained responses were analyzed with respect to the different sources of variability using a measure of the perceptual distance between responses. The speech-induced variability across and within talkers and the across-listener variability were substantial and of similar magnitude. The noise-induced variability, obtained with time-shifted realizations of the same random process, was smaller but significantly larger than the amount of within-listener variability, which represented the smallest effect. The results have implications for the design of consonant perception experiments and provide constraints for future models of consonant perception.
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  • 35
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    Taylor & Francis
    In:  Biodiversity, 17 (1-2). pp. 5-11.
    Publication Date: 2017-03-31
    Description: Antarctica is a still unexplored area in many respects, among which biological diversity and, even more so, chemical diversity are important challenges. Over recent years, our research group has been studying marine benthic ecosystems in different Antarctic areas. These studies yielded several interesting discoveries, including species new to science, as well as new natural products never seen before. Overall, we have been trying to unravel the complex network of interactions that exist between marine benthic organisms in these cold and hardly accessible ecosystems. We present here an overview of our recent results regarding the biological and the chemical diversity of these organisms. In fact, these ecosystems are as complex as many other marine environments on the planet, and indeed, many questions remain yet to be answered.
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  • 36
    Publication Date: 2020-02-06
    Description: IODP Expedition 350 was the first to be drilled in the rear part of the Izu-Bonin, although several sites had been drilled in the arc axis to fore-arc region; the scientific objective was to understand the evolution of the Izu rear arc, by drilling a deep-water volcaniclastic section with a long temporal record (Site U1437). The Izu rear arc is dominated by a series of basaltic to dacitic seamount chains up to ~100-km long roughly perpendicular to the arc front. Dredge samples from these are geochemically distinct from arc front rocks, and drilling was undertaken to understand this arc asymmetry. Site U1437 lies in an ~20-km-wide basin between two rear arc seamount chains, ~90-km west of the arc front, and was drilled to 1804 m below the sea floor (mbsf) with excellent recovery. We expected to drill a volcaniclastic apron, but the section is much more mud-rich than expected (~60%), and the remaining fraction of the section is much finer-grained than predicted from its position within the Izu arc, composed half of ashes/tuffs, and half of lapilli tuffs of fine grain size (clasts 〈3 cm). Volcanic blocks (〉6.4 cm) are only sparsely scattered through the lowermost 25% of the section, and only one igneous unit was encountered, a rhyolite peperite intrusion at ~1390 mbsf. The lowest biostratigaphic datum is at 867 mbsf (~6.5 Ma), the lowest palaeomagnetic datum is at ~1300 mbsf (~9 Ma), and the rhyolite peperite at ~1390 mbsf has yielded a U–Pb zircon concordia intercept age of (13.6 + 1.6/−1.7) Ma. Both arc front and rear arc sources contributed to the fine-grained (distal) tephras of the upper 1320 m, but the coarse-grained (proximal) volcaniclastics in the lowest 25% of the section are geochemically similar to the arc front, suggesting arc asymmetry is not recorded in rocks older than ~13 Ma.
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  • 37
    Publication Date: 2020-07-31
    Description: The population size and breeding success of Emperor Penguins Aptenodytes forsteri at the Auster and Taylor Glacier colonies were estimated during the 1988 breeding season. At Auster a total of 10 963 pairs produced about 6350 fledglings for a breeding success of 58%. At Taylor Glacier about 2900 pairs raised 1774 fledglings for a breeding success of 61%. Fledglings left Taylor Glacier over a period of 33 days at a mean mass of 10.56 kg.
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  • 38
    Publication Date: 2020-02-06
    Description: In this opinion paper, we, a group of scientists from environmental-, geo-, ocean- and information science, argue visual data exploration should become a common analytics approach in Earth system science due to its potential for analysis and interpretation of large and complex spatio-temporal data. We discuss the challenges that appear such as synthesis of heterogeneous data from various sources, reducing the amount of information and facilitating multidisciplinary, collaborative research. We argue that to fully exploit the potential of visual data exploration, several bottlenecks and challenges have to be addressed: providing an efficient data management and an integrated modular workflow, developing and applying suitable visual exploration concepts and methods with the help of effective and tailored tools as well as generating and raising the awareness of visual data exploration and education. We are convinced visual data exploration is worth the effort since it significantly facilitates insight into environmental data and derivation of knowledge from it.
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  • 39
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    American Institute of Physics
    In:  Journal of the Acoustical Society of America, 90 (4, Pt. 2). pp. 2255-2256.
    Publication Date: 2020-07-16
    Description: Seafloor topography is neither spatially homogeneous, nor does it obey Gaussian statistics; deviations from both of these assumptions are important from a geological and acoustic point of view. It has been found that the distribution of topographic slopes can be used as a primary tool for understanding the sources and extent of spatial heterogeneities and patterns on the seafloor. The covariance function has been widely used to characterize seafloor topography, but requires the assumption of Gaussian joint probability statistics to be valid. For heterogeneous topography characterized by large transient signals such as steep scarps and volcanoes, the covariance becomes dominated by the transients; in contrast the family slope distributions can still be used to derive stable descriptors for regions with large transient signals, as well as regions containing asymmetric features, and regions with only limited sampling. Knowledge of slopes is useful because a direct relation exists between the covariance and the slope distributions at different spatial scales. Studies of the slope distribution provide a means of identifying the presence of the non‐Gaussian elements in the topography, and flagging their spatial locations. The methods used here are demonstrated by applying them to three small patches of topography located within 20 km of each other in the Eastern Pacific. It is found that dominant azimuthal directions and dip angles differ widely between the patches. In addition, asymmetries in the cross‐sectional shapes of faulted abyssal hills are documented. [Work supported by ONR.]
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  • 40
    Publication Date: 2021-02-08
    Description: The North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) describe the dominant part of the variability in the Northern Hemisphere extratropical troposphere. Due to the strong connection of these patterns with surface climate, recent years have shown an increased interest and an increasing skill in forecasting them. However, it is unclear what the intrinsic limits of short-term predictability for the NAO and AO patterns are. This study compares the variability and predictability of both patterns, using a range of data and index computation methods for the daily NAO/AO indices. Small deviations from Gaussianity are found and characteristic decorrelation time scales of around one week. In the analysis of the Lyapunov spectrum it is found that predictability is not significantly different between the AO and NAO or between reanalysis products. Differences exist however between the indices based on EOF analysis, which exhibit predictability time scales around 12 - 16 days, and the station-based indices, exhibiting a longer predictability of 18 - 20 days. Both of these time scales indicate predictability beyond that currently obtained in ensemble prediction models for short-term predictability. Additional longer-term predictability for these patterns may be gained through local feedbacks and remote forcing mechanisms for particular atmospheric conditions.
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  • 41
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    AMS (American Meteorological Society)
    In:  Bulletin of the American Meteorological Society, 98 (6). ES139-ES142.
    Publication Date: 2020-07-16
    Description: The 13th European Polar Low Workshop was organized by the European Polar Low Working Group (www.uni-trier.de/index.php?id=20308)and gathered scientists from nine countries focusing on polar mesocyclones in both hemispheres and other mesoscale weather phenomena such as katabatic winds, tip jets, boundary layer fronts, cold air outbreaks, and weather extremes in polar regions. Topics included experimental, climatological, theoretical, modeling, and remote sensing studies. The aim was to bring together scientists and forecasters to present their latest work and recent findings on these topics and to encourage discussions on improving forecasting and understanding of these phenomena.
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  • 42
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    AMS (American Meteorological Society)
    In:  Journal of Climate, 30 (22). pp. 8913-8927.
    Publication Date: 2020-02-06
    Description: The regional climate model COSMOin Climate Limited-AreaMode (COSMO-CLM or CCLM) is used with a high resolution of 15km for the entire Arctic for all winters 2002/03–2014/15. The simulations show a high spatial and temporal variability of the recent 2-m air temperature increase in the Arctic. The maximum warming occurs north of Novaya Zemlya in the Kara Sea and Barents Sea between March 2003 and 2012 and is responsible for up to a 208C increase. Land-based observations confirm the increase but do not cover the maximum regions that are located over the ocean and sea ice.Also, the 30-km version of theArctic SystemReanalysis (ASR) is used to verify the CCLM for the overlapping time period 2002/03–2011/12. The differences between CCLM and ASR 2-m air temperatures vary slightly within 18C for the ocean and sea ice area. Thus,ASR captures the extreme warming as well. The monthly 2-m air temperatures of observations and ERA-Interim data show a large variability for the winters 1979–2016. Nevertheless, the air temperature rise since the beginning of the twenty-first century is up to 8 times higher than in the decades before. The sea ice decrease is identified as the likely reason for the warming. The vertical temperature profiles show that the warming has a maximum near the surface, but a 0.58Cyr21 increase is found up to 2 km. CCLM, ASR, and also the coarser resolved ERA-Interim data show that February and March are the months with the highest 2-m air temperature increases, averaged over the ocean and sea ice area north of 708N; for CCLM the warming amounts to an average of almost 58C for 2002/03–2011/12.
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  • 43
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    Taylor & Francis
    In:  Ophelia, 36 (2). pp. 111-118.
    Publication Date: 2018-03-01
    Description: This paper presents an idea on the possible structuring effect of hex actinellids on Antarctic sponge associations. To this end, information derived from underwater photography performed on the eastern Weddell Sea shelf is reported and original trawl data are presented. Underwater photography shows the existence of different sponge associations; species poor associations are connected to soft bottom, species rich associations exist on substrates characterized by bryozoan debris and especially sponge spicule mats. The trawl. catches show differences in the population structure of a hexactinellid sponge, Rassella racovitzae Topsent at two stations, distinguishable from each other by substrate structure. On average small and therefore probably young specimens were found on bryozoan debris, while a population with larger and probably older specimens was found on solid hexactinellid spicule mats. These observations form the basis for the hypothesis that hexactinellid sponges are a major biological structuring agent for Antarctic sponge associations; they colonize soft substrate and bryozoan debris dominated areas and subsequently change the quality of the substrate by spicule deposition. The ensuing spicule mats are a suitable settling ground for a large number of demosponge species dependent on hard substrates. Mass occurrences of hexactinellids are also found in areas other than Antarctica. The phenomenon recognized in the Weddell Sea probably occurs more widely spread.
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  • 44
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    In:  International Journal of Remote Sensing, 13 (10). pp. 1829-1841.
    Publication Date: 2018-03-09
    Description: A method is proposed for cloud detection over sea using a single infrared channel of a high spatial resolution satellite radiometer. The method combines a spatial coherence test and an absolute threshold test for the temperature field. The threshold for the second test is automatically determined by a histogram analysis of data which were preselected by the coherence test. The coherence test used differs from the classical standard deviation test in the way of the test value computation: the weight of the pixel to be investigated is increased. A simulation shows that under conditions of low cloud cover this makes the proposed coherence test more sensitive than the standard deviation test. When applied to real data the test was also found to be very sensitive compared with visible and IR threshold tests. Cloud cover obtained by the whole method is finally compared with that resulting from the visible and IR histogram analysis procedure of Phulpin et al. This comparison indicates a high reliability of the proposed method.
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  • 45
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    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 23 (11). pp. 2373-2391.
    Publication Date: 2018-03-07
    Description: A sigma-coordinate, primitive equation ocean circulation model is used to explore the problem of the remnant generation of trapped waves about a tall, circular, isolated seamount by an incident oscillatory barotropic current. The numerical solutions are used to extend prior studies into the fully nonlinear regime, and in particular to quantify and interpret the occurrence of residual circulation. Specific attention is also devoted to the dependence of the resonance and rectification mechanisms on stratification, forcing frequency, and choice of subgrid-scale viscous closure. Resonantly generated trapped waves of significant amplitude are found to occur broadly in parameter space; a precise match between the frequency of the imposed incident current and the frequency of the trapped free wave is not necessary to produce substantial excitation of the trapped wave. The maximum amplification factors produced in these numerical solutions, O(100) times the strength of the incident current, are consistent with previous studies. In the presence of nonlinear advection, strong residual currents are produced. The time-mean circulation about the seamount is dominated by a strong bottom-intensified, anticyclonic circulation closely trapped to the seamount. Maximum local time-mean current amplitudes are found to be as large as 37% of the magnitude of the propagating waves. In addition to the strong anticyclonic residual flow, there is a weaker secondary circulation in the vertical-radial plane characterized by downwelling over the top of the seamount at all depths. Maximum vertical downwelling rates of several tens of meters per day occur at the summit of the seamount. The vertical mass flux implied by this systematic downwelling is balanced by a slow radial flux of mass directed outward along the flanks of the seamount. Time-mean budgets for the radial and azimuthal components of momentum show that horizontal eddy fluxes of momentum are responsible for transporting net radial and azimuthal momentum from the far field to the upper flanks of the seamount. There, Coriolis and pressure gradient forces provide the dominant balances in the radial direction. However, the Coriolis force and viscous effects provide the primary balance for the azimuthal component.
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  • 46
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    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 22 (1). pp. 93-104.
    Publication Date: 2018-03-09
    Description: North Atlantic air-sea heat and freshwater flux data from several sources are used to estimate the conversion rate of water from one density to another throughout the range of sea surface density. This cross-isopycnal mass flux varies greatly over the ocean, with a maximum of 32.2 × 106 m3 s−1 at σ = 26.1 kg m−3 (toward greater densities) and a minimum of −7.6 × 106 m3 s−1 (toward lesser densities) at σ = 23.0 kg m−3. The air-sea fluxes force water to accumulate in three density bands: one at the lowest sea surface densities generated by heating; one centered near the density of subtropical mode water; and one spanning subpolar mode water densities. The transfer of water to the highest and lowest densities is balanced by mixing, which returns water to the middle density range, and also by boundary sources or sinks. Integrating the cross-isopycnal flux over all densities gives an annual average sinking of about 9 × 1O6 m3 s−1, which presumably escapes across the equator and must be balanced by a similar inflow. Comparison with estimates from tracer studies suggests that the renewal of tracer characteristics at a given density may occur without the existence of an annual average mass source at that density, because along- and cross-isopycnal mixing can renew a tracer without supplying mass.
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  • 47
    Publication Date: 2018-03-22
    Description: Tests on the effects of two herbivore groups (littorinid snails and gammarid amphipods), on algal succession in high intertidal tidepools dominated by Fucus distichus showed that the grazer groups exert different grazing pressures on the algae. The differences can be related to the feeding morphologies ofthe two grazer guilds. The scraping, microphagous littorinid snails prevent the establishment of both micro- and rnacroalgae at the microscopic level. The biting, macrophagous gammarid amphipods are ineffective at grazing microalgae and prostrate macroalgae from the substratum, but exert a considerable influence on the erect macroalgae which escape littorinid grazing. Despite differences in feeding mechanisms, the magnitude of the effect of the two grazer groups on the canopy cover of macroalgae is similar.
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  • 48
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    Taylor & Francis
    In:  Marine Georesources & Geotechnology, 34 (5). pp. 465-473.
    Publication Date: 2019-02-01
    Description: In this study, Lade's double-surface work-hardening constitutive model was adopted which uses the elasto-plasticity model as a basic conceptual framework. The model can analyze work hardening and work softening of nonlinear stress-strain behavior, and is regarded as superior to other elasto-plasticity constitutive models in terms of estimation. In the double-surface work-hardening constitutive model, 14 soil parameters are needed to estimate soil behaviors. To determine them, laboratory tests—isotropical consolidation test and conventional compression test—were conducted. Determining of soil parameters is highly complicated and time-consuming; randomness cannot be ruled out in determining parameters that are sensitive to stress-strain estimation, and error may occur. For this reason, a linear and nonlinear regression analysis was used to determine soil parameters. In estimation of undrained behavior, the estimated stress-strain behavior based on the two constitutive models largely overlapped with the test results. However, in estimating drained behavior, the outcome of the two models and the test results were mostly the same, but between the two models, the double-surface work-hardening constitutive model had a sharper slope in initial stress state, and a smaller maximum deviatoric stress.
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  • 49
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    In:  Marine Behaviour and Physiology, 9 (2). pp. 139-170.
    Publication Date: 2018-05-22
    Description: The behaviour of Chelophyes has been analysed from the point of view of coordination between stem and nectophores, and an electron microscope study of the effectors and conducting elements has been carried out. Coordination between the stem and anterior nectophore involves two pathways, one epithelial and the other nervous. The nervous link consists of a bundle of small neurites and a single giant axon. There is some evidence that this mediates rapid escape behaviour. After the nerves have been cut, coordination is maintained via the epithelial route. Impulses can jump from epithelial cells into nerves but the transmission process is unclear. Neuro‐epithelial transmission involves conventional synapses. As in physonectid siphonophores, the stem has two nervous systems each with its own giant fibre, and a slow system, the endodermal epithelium. In the nectophore, marginal nerve centres generate a swimming rhythm. Conduction in the subumbrellar muscle is myoid. The exumbrellar epithelium and the subumbrellar endoderm are conducting tissues. Histological study reveals synapses in the predicted locations and gives details of myo‐epithelial organization and nervous layout. Novel histological features include elements resembling steroid‐secreting cells, which ensheath nerves and are innervated by them, and innervated giant non‐nervous cells lying between the nerve ring and the hydroecium. The subumbrellar muscle cells are shown to have sarcolemmal invaginations reminiscent of the f‐tubule system of vertebrate muscle.
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  • 50
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    In:  Journal of the Atmospheric Sciences, 75 (8). pp. 2815-2826.
    Publication Date: 2021-02-08
    Description: The formation of secondary ice in clouds, i.e. ice particles that are created at temperatures above the limit for homogeneous freezing without the direct involvement of a heterogeneous ice nucleus is one of the longest standing puzzles in cloud physics. Here we present comprehensive laboratory investigations on the formation of small ice particles upon the freezing of drizzle-sized cloud droplets levitated in an electrodynamic balance. Four different categories of secondary ice formation (bubble bursting, jetting, cracking, breakup) could be detected and their respective frequencies of occurrence as a function of temperature and droplet size are given. We find that bubble bursting occurs more often than droplet splitting. While we do not observe the shattering of droplets into many large fragments, we find that the average number of small secondary ice particles released during freezing is strongly droplet-size dependent and may well exceed unity for droplets larger than 300 μm in diameter. This leaves droplet fragmentation an important secondary ice process effective at temperatures around -10 °C in clouds where large drizzle droplets are present.
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  • 51
    Publication Date: 2019-02-01
    Description: Well-known problems trouble coupled general circulation models of the eastern Atlantic and Pacific Ocean basins. Model climates are significantly more symmetric about the equator than is observed. Model sea surface temperatures are biased warm south and southeast of the equator, and the atmosphere is too rainy within a band south of the equator. Near-coastal eastern equatorial SSTs are too warm, producing a zonal SST gradient in the Atlantic opposite in sign to that observed. The U.S. Climate Variability and Predictability Program (CLIVAR) Eastern Tropical Ocean Synthesis Working Group (WG) has pursued an updated assessment of coupled model SST biases, focusing on the surface energy balance components, on regional error sources from clouds, deep convection, winds, and ocean eddies; on the sensitivity to model resolution; and on remote impacts. Motivated by the assessment, the WG makes the following recommendations: 1) encourage identification of the specific parameterizations contributing to the biases in individual models, as these can be model dependent; 2) restrict multimodel intercomparisons to specific processes; 3) encourage development of high-resolution coupled models with a concurrent emphasis on parameterization development of finer-scale ocean and atmosphere features, including low clouds; 4) encourage further availability of all surface flux components from buoys, for longer continuous time periods, in persistently cloudy regions; and 5) focus on the eastern basin coastal oceanic upwelling regions, where further opportunities for observational–modeling synergism exist.
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  • 52
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    In:  Marine Behaviour and Physiology, 8 (2). pp. 135-148.
    Publication Date: 2020-07-14
    Description: The major light and dark components of body displays are described and classified for the octopus Eledone cirrhosa (Lamarck) under aquarium conditions. Comparisons are made with Octopus vulgaris and Eledone moschata. Upon the basic similarity of white display components in the three species is superimposed a trend of modification. Dark components are less various in Eledone cirrhosa and although the chromatophores are organised with leucophores into chromatic units these are not clearly limited morphologically by “grooves”. The mottle patterns of Eledone seem to be arranged along the longitudinal and latitudinal (radial) axes of the animal, the grade of mottle does not respond to grade of background contrast.
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  • 53
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    In:  Journal of Natural History, 25 (5). pp. 1121-1133.
    Publication Date: 2020-07-21
    Description: The enoploteuthid cephalopod Abraliopsis lineata is re-described and its generic position discussed. Specimens for the present study were captured during the Indian Ocean Expedition of RV Meteor in 1987, where the species occurred in considerable numbers. The geographical distribution of A. lineata is described and discussed. The detailed analysis of the photophore pattern of the present specimens differs from the original description. The diagnostic features in the male, especially the structure of the hectocotylus which separates A. lineata easily from the members of the subgenus Pfefferiteuthis, are outlined. The morphological differences which separate A. lineata from A. gilchristi, the only other member of the subgenus Micrabralia, are summarized.
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  • 54
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    In:  South African Journal of Marine Science, 12 (1). pp. 843-861.
    Publication Date: 2020-05-26
    Description: The diets of 20 species of smaller Odontoceti were investigated. The material was collected along the southern African coast between 1966 and 1990 and included 158 strandings, 29 animals killed incidentally and 49 animals caught under permit. In total, 57 species in 34 families of fish and 89 species in 24 families of cephalopods were identified from remains in the 236 stomachs investigated. Most Odontoceti fed on commercially unexploited cephalopods and fish, or on fish below commercially utilized sizes. However, the average sizes of anchovy and pilchard eaten by Delphinus delphis and Lagenorhynchus obscurus were larger than the sizes most frequently taken commercially. The species composition of the prey items reflected the onshore-offshore distribution (and possibly the foraging depths) of different Odontoceti. Tursiops truncatus and Cephalorhynchus heavisidii were closest to shore and D. delphis and L. obscurus over the continental shelf. The rest were distributed around the shelf-edge and just off the edge. A comparison of the stomach contents of stranded and non-stranded D. delphis, L. obscurus and C. heavisidii demonstrated that results from stranded animals are biased.
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  • 55
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    In:  Plant Biosystems - An International Journal Dealing with all Aspects of Plant Biology, 150 (1). pp. 152-160.
    Publication Date: 2019-02-01
    Description: The aim of this study was to test the effects of temperature on phenolic content of the brown seaweed Cystoseira amentacea. Phenolic compounds are secondary metabolites involved in different protection mechanisms as, for example, against grazers, epiphytes and UV radiation. Seasonal variations of phenolic content in C. amentacea were analysed and laboratory experiments, in which C. amentacea was exposed to an increase of temperature (25°C and 30°C), were performed. Total phenolic content (TPC) was determined colorimetrically with the Folin–Ciocalteu reagent. In C. amentacea, a seasonal pattern in TPC was observed, with a maximum value in winter-spring. C. amentacea responded significantly to the temperature treatments with a consistent decrease in TPC after 48 h.
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  • 56
    Publication Date: 2020-05-28
    Description: The stomach contents of 723 Loligo vulgaris and 440 Loligo forbesi caught in the northwestern Spanish Atlantic waters have been examined. The diets of both species are described and compared. Loligo vulgaris shows 28 different types of prey belonging to four groups (Teleostei, Crustacea, Cephalopoda and Polychaeta) and Loligo forbesi 27 different types of prey belonging to three groups (Teleostei, Crustacea and Cephalopoda). Both species catch similar prey species but in different proportions. Cannibalism was observed in both species. Estimated prey sizes were smaller than squid sizes. No differences in feeding habits of males and females of both species were observed, but females seem to increase food intake during maturation. No significant changes were found in the diet of Loligo vulgaris within the size (DML) range studied (65–465 mm). Importance of cephalopods increased and importance of fish decreased in the diet of Loligo forbesi with growth (65–685 mm). Diet and food intake varied with seasons in both species. Diets of both squids were significantly different. Los contenidos estomacales de 723 Loligo vulgaris y 440 Loligo forbesi capturados en aguas de Galicia (Noroeste de España) fueron examinados. Se describe y compara la dieta de ambas especies. Se identificaron 28 tipos de presa diferentes en Loligo vulgaris que pertenecen a cuatro grupos (Teleostei, Crustacea, Cephalopoda y Polychaeta); y 27 tipos de presa en Loligo forbesi, pertenecientes a tres grupos (Teleostei, Crustacea y Cephalopoda). Ambas especies comen pres as similares, pero en proporciones diferentes. En ambas especies se observó canibalismo. La talla de las presas fue menor que la de los calamares. No se encontraron diferencias en la dieta entre machos y hembras en ambas especies, pero se observó que las hembras incrementan su tasa de ingestión durante la maduración. No se hallaron cambios significativos en la dieta de Loligo vulgaris en función de la talla (DML) dentro del rango de tamanos estudiado (65–465 mm). En Loligo forbesi, los cefalópodos aumentaron y los peces disminuyeron en importancia con la talla (65–685 mm DML). La dieta y la tasta de ingestión de ambas especies varió con la época del ano. Las dietas de ambas especies fueron significativemente diferentes entre sí.
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  • 57
    Publication Date: 2019-02-01
    Description: Fluorescent-amplified fragment length polymorphism (FAFLP) fingerprinting assay was used to compare the genetic diversity within and between tadpole shrimps (Notostraca) populations of Lepidurus apus (n=7) and Triops cancriformis (n=2) from rain pools in Israel. Each ephemeral water body has revealed a unique fingerprint pattern with an entailed genetic drift between nearby ponds. High similarity of genotypic diversity within each geographic area led to three clusters of water bodies, north, south and center of Israel. FAFLP assays on several newly hatched individuals of T. cancriformis revealed high identity amongst kin, as compared to L. apus where newly hatched from the same maternal source showed high diversity. Results indicate that T. cancriformis populations from Israel are probably parthenogenetic as indicated by clonal structures. The higher genetic variability in the L. apus populations and in laboratory-hatched specimens indicates the existence of sexual reproduction.
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  • 58
    Publication Date: 2020-07-09
    Description: Gammarids from the Caspian complex have invaded many European waters along the rivers and canals of the inland migration corridors. The species examined in this work are well known as invaders of European freshwater environments, so the colonization of brackish habitats is a phenomenon inviting more detailed investigation. The aim of this study was to determine the condition of the Ponto-Caspian gammarids Pontogammarus robustoides (G.O. Sars, 1894), Obesogammarus crassus (G.O. Sars, 1894), Dikerogammarus haemobaphes (Eichwald, 1841) and Dikerogammarus villosus (Sowinsky, 1894) as expressed by the relationship between total length and the wet weight of specimens in the brackish waters of the Gulf of Gdansk (Poland). The relationships can be regarded as responses to a newly expanded habitat after they overcome the salinity barrier of the southern Baltic Sea coastal waters. All these Ponto-Caspian gammarids demonstrated an increase in weight with increasing total length: P. robustoides (b = 2.852), O. crassus (b = 3.3477), D. haemobaphes (b = 3.7855) and D. villosus (b = 2.6917). The results are an indicator of the relatively good condition of the organisms and indicate that the brackish environment of the Gulf of Gdansk affords them excellent possibilities for growth.
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  • 59
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    In:  Journal of Climate, 30 (8). pp. 2921-2935.
    Publication Date: 2020-02-06
    Description: The ratio of global mean surface air temperature change to cumulative CO2 emissions, referred to as transient climate response to cumulative CO2 emissions (TCRE), has been shown to be approximately constant on centennial time scales. The mechanisms behind this constancy are not well understood, but previous studies suggest that compensating effects of ocean heat and carbon fluxes, which are governed by the same ocean mixing processes, could be one cause for this approximate constancy. This hypothesis is investigated by forcing different versions of the University of Victoria Earth System Climate Model, which differ in the ocean mixing parameterization, with an idealized scenario of 1% annually increasing atmospheric CO2 until quadrupling of the preindustrial CO2 concentration and constant concentration thereafter. The relationship between surface air warming and cumulative emissions remains close to linear, but the TCRE varies between model versions, spanning the range of 1.2°–2.1°C EgC−1 at the time of CO2 doubling. For all model versions, the TCRE is not constant over time while atmospheric CO2 concentrations increase. It is constant after atmospheric CO2 stabilizes at 1120 ppm, because of compensating changes in temperature sensitivity (temperature change per unit radiative forcing) and cumulative airborne fraction. The TCRE remains approximately constant over time even if temperature sensitivity, determined by ocean heat flux, and cumulative airborne fraction, determined by ocean carbon flux, are taken from different model versions with different ocean mixing settings. This can partially be explained with temperature sensitivity and cumulative airborne fraction following similar trajectories, which suggests ocean heat and carbon fluxes scale approximately linearly with changes in vertical mixing.
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  • 60
    Publication Date: 2020-02-06
    Description: A bioassay-guided approach was used to identify defense compounds that are present on the surface of Zostera marina and which inhibit settlement of microfoulers at natural concentrations. Moderately polar eelgrass surface extracts inhibited the settlement of seven marine bacteria and one yeast that originated from non-living substrata. In contrast, five other bacterial strains that had been directly isolated from eelgrass surfaces were all insensitive, which suggested a selective effect of surface metabolites on the microbial communities present on eelgrass. Bioassay-guided isolation of active compounds from the extracts in combination with UPLC-MS and 1H-NMR spectroscopy resulted in the identification of rosmarinic acid, luteolin-7-sulfate and diosmetin-7-sulfate or its isomer chrysoeriol-7-sulfate. All three compounds are nontoxic repellents, as they did not inhibit bacterial growth, but prevented bacterial settlement in a dose-dependent manner. Between 15.6 and 106.8 μg ml−1 of rosmarinic acid were present on the eelgrass surface, enough for half maximal settlement inhibition of bacteria.
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  • 61
    Publication Date: 2020-02-06
    Description: The Weddell Sea polynya is a large opening in the open-ocean sea ice cover associated with intense deep convection in the ocean. A necessary condition to form and maintain a polynya is the presence of a strong subsurface heat reservoir. This study investigates the processes that control the stratification and hence the buildup of the subsurface heat reservoir in the Weddell Sea. To do so, a climate model run for 200 years under preindustrial forcing with two eddying resolutions in the ocean (0.25° CM2.5 and 0.10° CM2.6) is investigated. Over the course of the simulation, CM2.6 develops two polynyas in the Weddell Sea, while CM2.5 exhibits quasi-continuous deep convection but no polynyas, exemplifying that deep convection is not a sufficient condition for a polynya to occur. CM2.5 features a weaker subsurface heat reservoir than CM2.6 owing to weak stratification associated with episodes of gravitational instability and enhanced vertical mixing of heat, resulting in an erosion of the reservoir. In contrast, in CM2.6, the water column is more stably stratified, allowing the subsurface heat reservoir to build up. The enhanced stratification in CM2.6 arises from its refined horizontal grid spacing and resolution of topography, which allows, in particular, a better representation of the restratifying effect by transient mesoscale eddies and of the overflows of dense waters along the continental slope.
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  • 62
    Publication Date: 2019-02-01
    Description: For the environmental monitoring of coral, mucus appears to be an appropriate biological matrix due to its array of functions in coral biology and the non-intrusive manner in which it can be collected. The aim of the present study was to evaluate the feasibility of using mucus of the stony coral Lophelia pertusa (L. pertusa) as an analytical matrix for discovery of biomarkers used for environmental monitoring. More specifically, to assess whether a mass-spectrometry-based proteomic approach can be applied to characterize the protein composition of coral mucus and changes related to petroleum discharges at the seafloor. Surface-enhanced laser desorption/ionization–time of flight mass spectrometry (SELDI-TOF MS) screening analyses of orange and white L. pertusa showed that the mucosal protein composition varies significantly with color phenotype, a pattern not reported prior to this study. Hence, to reduce variability from phenotype difference, L. pertusa white individuals only were selected to characterize in more detail the basal protein composition in mucus using liquid chromatography, mass spectrometry, mass spectrometry (LC-MS/MS). In total, 297 proteins were identified in L. pertusa mucus of unexposed coral individuals. Individuals exposed to drill cuttings in the range 2 to 12 mg/L showed modifications in coral mucus protein composition compared to unexposed corals. Although the results were somewhat inconsistent between individuals and require further validation in both the lab and the field, this study demonstrated preliminary encouraging results for discovery of protein markers in coral mucus that might provide more comprehensive insight into potential consequences attributed to anthropogenic stressors and may be used in future monitoring of coral health.
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  • 63
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    In:  Sarsia, 78 (3-4). pp. 255-264.
    Publication Date: 2018-03-05
    Description: A new species of Siboglinum is reported from off the Tejo mouth, Portugal. It was dredged from c. 1100 m. It resembles S. atlanticum and certain other species, in having paired white glandular stripes on the forepart. In the posterior trunk region we found small gram-negative internal symbiotic bacteria. All described species of the genus Siboglinum are equipped with a single tentacle, but one of our specimens bears two tentacles.
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  • 64
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    In:  International Journal of Remote Sensing, 14 (8). pp. 1447-1461.
    Publication Date: 2018-03-22
    Description: Most atmospheric parameters relevant to microbe dissemination into the atmosphere, including aerial transport and deposition, can be monitored by temperature and humidity, aerosols, clouds, precipitation, and wind through current meteorological and other satellite systems. A wide range of these parameters are already extracted and distributed operationally on a regional or global basis like cloudiness, cloud height, cloud motion, winds, surface temperature and atmospheric temperature profiles, and precipitation estimates, Some of these products like cloud motion, winds, and temperature profiles enter weather forecast models for initialization purposes. These models predict the global state of the atmosphere (some include precipitation and cloudiness) quite reliably for several days. Thus, an important part of the necessary technical framework for global disease spread and transmission monitoring exists.
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  • 65
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    In:  Geomechanics and Geoengineering, 12 (4). pp. 221-233.
    Publication Date: 2018-12-17
    Description: The progressive bond breakage of artificially cemented sands induced by shear straining was investigated through conventional isotropically consolidated drained triaxial compression tests. Sand specimens were prepared with a low degree of cementation by adopting a chemical grout. Test results were interpreted in terms of two stress–dilatancy theories for cohesive-frictional materials proposed in literature. The influence of debonding on the stress–dilatancy behaviour of cemented sands was analysed with particular emphasis on the ‘delayed dilatancy’ phenomenon. A bonding degradation curve was determined for each test relating the interparticle cohesion (c) to the magnitude of the total plastic strain vector (εd) and a bond degradation rate factor (Dc) was assessed from each curve. The maximum value of interparticle cohesion (c0) before the onset of bond degradation under shearing was found to correspond with a sharp decrease in the soil stiffness of the specimens. The influence of the effective confining stress (p′c)on both c0 and Dc parameters gathered from each test was also ascertained.
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  • 66
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    In:  In: Energy Geotechnics. , ed. by Wuttke, F., Bauer, S. and Sanchez, M. Taylor & Francis, London, pp. 437-443. ISBN 978-1-138-03299-6
    Publication Date: 2020-07-27
    Description: Results from two recent field trials, onshore in the Alaska permafrost and in the Nankai Trough offshore Japan, suggest that natural gas could be produced from marine gas hydrate reservoirs at compatible yields and rates. However, both field trials were accompanied by different technical issues, the most striking problems resulting from un-predicted geomechanical behaviour, sediment destabilization and catastrophic sand production. So far, there is a lack of experimental data which could help to understand relevant mechanisms and triggers for potential soil failure in gas hydrate production, to guide model development for simulation of soil behaviour in large-scale production, and to identify processes which drive or, further, mitigate sand production. We use high-pressure flow-through systems in combination with different online and in situ monitoring tools (e.g. Raman microscopy, MRI) to simulate relevant gas hydrate production scenarios. Key components for soil mechanical studies are triaxial systems with ERT (Electric resistivity tomography) and high-resolution localstrain analysis. Sand production control and management is studied in a novel hollow-cylinder-type triaxial setup with a miniaturized borehole which allows fluid and particle transport at different fluid injection and flow conditions. We further apply a novel large-scale high-pressure flow-through triaxial test system equipped with μ-CT to evaluate soil failure modes and triggers relevant to gas hydrate production and slope stability. The presentation will emphasize an in-depth evaluation of our experimental approach, and it is our concern to discuss important issues of translating laboratory results to gas hydrate reservoirs in nature. We will present results from high-pressure flow-through experiments which are designed to systematically compare soil mechanical behaviour of gas hydrate-bearing sediments in relevant production scenarios focusing on depressurization and CO2 injection. Experimental datasets are analyzed based on numerical models which are able to simulate coupled process dynamics during gas hydrate formation and gas production.
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  • 67
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    In:  South African journal of marine science, 9 . pp. 189-200.
    Publication Date: 2020-05-26
    Description: Changes in the ovaries and testes during sexual maturation of Loligo vulgaris reynaudii were examined histologically. Fonnation and development of the spermatozoa and oocytes could be divided into four distinct stages for males and five for females, and frequencies of these stages in the morphologically determined categories of development of the whole reproductive System were calculated. These frequencies were then compared between morphological categories. Results showed that microscopic changes are reflected in macroscale changes for Categories I-IV, but differences between Categories IV and V are mostly morphological for both sexes. It is suggested that Loligo v. reynaudii is an intermittent spawner.
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  • 68
    Publication Date: 2017-01-19
    Description: Manganese nodule coverage is estimated based on multi-beam and deep-towed video nodule survey profiles of about 1,700 km in the China Pioneer Area of Eastern Pacific. Two statistical equations for estimating nodule coverage are derived separately from the multi-beam normal incidence amplitude data and angular amplitude data based on theoretical analysis of influence factors on multi-beam amplitude data. Predictions generated by the normal incidence amplitude model fall within 5% of real nodule coverage, and theoretically calculated angular amplitude data fits well with the original multi-beam amplitudes at incident angles larger than 20° according to nodule coverage estimated from the deep-towed video data.
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  • 69
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    In:  Marine Behaviour and Physiology, 18 (1). pp. 1-17.
    Publication Date: 2020-07-14
    Description: General biology of cephalopods is described. First, all commercially important cephalopods are classified and the general morphology and distribution of all major families is described in detail. Mating and spawning characteristics of all major families are discussed in detail. This is followed by a discussion on early life history, growth and principal ecoological changes that occur during the growth period. Schooling and migration characteristics are also taken up in considerable detail. The paper closes with a brief discussion on the trophic relation. The author points out that cephalopods are extremely important to mankind due to their unique position in the food chain extending from the oceans to man.
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  • 70
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    In:  Invertebrate Reproduction & Development, 19 (1). pp. 25-35.
    Publication Date: 2017-02-01
    Description: Larval behaviour, settlement, and metamorphosis were investigated in four Caribbean commercial sponges, Hippospongia lachne, Spongia barbara, S. cheiris and S. graminea, using light and transmission electron microscopy. The parenchymella larvae of these viviparous and gonochoristic species have an average size of 350 μm by 420 μm when released. Symbiotic bacteria occur intercellularly in both larvae and post-larvae. Laboratory behavioural studies demonstrate that free-swimming larvae display directional swimming with constant lateral rotation and negative phototaxis. Larval settlement occurs 26–56 hours after release from the parent and involves the formation of a basal lamella between the post-larva and substrate. There is no evidence of larval substrate selection by type or orientation. The canal system begins to form six days after settlement and oscules are apparent eleven days post-settlement. Available evidence suggests that larval ciliated epithelial cells are terminally differentiated and do not appear to contribute to formation of post larva or adult in this group of Porifera.
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  • 71
    Publication Date: 2019-02-01
    Description: Suspended particulate matter (SPM) causes most of the scattering in natural waters and thus has a strong influence on the underwater light field, and consequently on the whole ecosystem. Turbidity is related to the concentration of SPM which usually is measured gravimetrically, a rather time-consuming method. Measuring turbidity is quick and easy, and therefore also more cost-effective. When derived from remote sensing data the method becomes even more cost-effective because of the good spatial resolution of satellite data and the synoptic capability of the method. Turbidity is also listed in the European Union’s Marine Strategy Framework Directive as a supporting monitoring parameter, especially in the coastal zone. In this study, we aim to provide a new Baltic Sea algorithm to retrieve SPM concentration from in situ turbidity and investigate how this can be applied to satellite data. An in situ dataset was collected in Swedish coastal waters to develop a new SPM model. The model was then tested against independent datasets from both Swedish and Lithuanian coastal waters. Despite the optical variability in the datasets, SPM and turbidity were strongly correlated (r = 0.97). The developed model predicts SPM reliably from in situ turbidity (R2 = 0.93) with a mean normalized bias (MNB) of 2.4% for the Swedish and 14.0% for the Lithuanian datasets, and a relative error (RMS) of 25.3% and 37.3%, respectively. In the validation dataset, turbidity ranged from 0.3 to 49.8 FNU (Formazin Nephelometric Unit) and correspondingly, SPM concentration ranged from 0.3 to 34.0 g m–3 which covers the ranges typical for Baltic Sea waters. Next, the medium-resolution imaging spectrometer (MERIS) standard SPM product MERIS Ground Segment (MEGS) was tested on all available match-up data (n = 67). The correlation between SPM retrieved from MERIS and in situ SPM was strong for the Swedish dataset with r = 0.74 (RMS = 47.4 and MNB = 11.3%; n = 32) and very strong for the Lithuanian dataset with r = 0.94 (RMS = 29.5% and MNB = −1.5%; n = 35). Then, the turbidity was derived from the MERIS standard SPM product using the new in situ SPM model, but retrieving turbidity from SPM instead. The derived image was then compared to existing in situ data and showed to be in the right range of values for each sub-area. The new SPM model provides a robust and cost-efficient method to determine SPM from in situ turbidity measurements (or vice versa). The developed SPM model predicts SPM concentration with high quality despite the high coloured dissolved organic matter (CDOM) range in the Baltic Sea. By applying the developed SPM model to already existing remote sensing data (MERIS/Envisat) and most importantly to a new generation of satellite sensors (in particular OLCI on board the Sentinel-3), it is possible to derive turbidity for the Baltic Sea.
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  • 72
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    Taylor & Francis
    In:  Marine Behaviour and Physiology, 19 (1). pp. 35-38.
    Publication Date: 2020-07-14
    Description: To evaluate the feasibility of feeding Sepia officinalis on artificial food, a food pellet consisting of Palaemon serratus powder and alginate as binding agent was developed and tested. Six of seven cuttlefish clearly ingested the artificial food during the ten days it was supplied.
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  • 73
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    Taylor & Francis
    In:  Marine Behaviour and Physiology, 18 (3). pp. 149-226.
    Publication Date: 2020-07-14
    Description: Knowledge concerning biology of two loliginids and three sepiids which are found in the Japanese waters was reviewed including unpublished information of the authors. The swordtip squid, Photololigo edulis, is one of the most important resources for the coastal fisheries of Kyushu and the prefectures facing the southwest Japan Sea. This species is the only species of genus Photololigo found along the Japanese mainland coast and is easily distinguished from other loliginids, by the light organs on the ink sac. The species is distributed from southern Japan to the Red Sea. The spawning season extends throughout the year. Egg cases are laid in clusters on the sandy bottom. The life span is about one year. In the juvenile stage they feed on Crustacea and after reaching pre‐maturity they prey mainly on fish, but many have empty stomachs. Most catches are made by jigging and trawler. The fishing season extends throughout the year. The fishing grounds are widely spread over the continental shelf. Annual catches are around 25 000 metric tonnes. Although this level varies from year to year, it is fairly stable. Fishing has probably little effect on the stocks. The spear squid, Heterololigo bleekeri, can be easily distinguished from other loliginids by its shorter tentacles. The species is endemic in the Far East waters. The stocks are larger in the north. The spawning season is winter in south Japan, and from spring to early summer in north Japan. Egg cases are laid beneath the undersurfaces of firm substances. The life span is about one year. Its feeding behaviour is similar to that of the swordtip squid. Catches are made mainly with bottom trawler and fixed nets from autumn to spring. Annual landings fluctuate widely from year to year. Several prefectures along the northern Japan Sea coast are promoting the large scale development of artificial spawning beds of the species to increase the stocks. The three sepiids, golden cuttlefish. Sepia esculenta, kisslip cuttlefish. Sepia lycidas, and spineless cuttlefish, Sepiella japonica are important in mainland Japan. Those three spawn from spring to early summer in the innermost waters of semi‐enclosed inlets. Eggs are laid in batches of 50–300 every day for 3–4 days followed by a rest period of 1–2 days. This pattern is repeated until several thousands of eggs have been laid. The life span of Sepia esculenta and Sepiella japonica is one year. They feed mainly on decapod crustaceans and fish but as growth proceeds the proportion of fish increases. They are fished mainly by cuttlefish trap and beam trawler. In the early 1960s annual landings were 20 000 metric tonnes but since 1980 catches have decreased below 10 000 metric tonnes. Of the three species, the stock of Sepiella japonica is the most fluctuable. Judging from the result of the stock assessment studies on Sepiella japonica in the western Inland Sea, their stocks have been over‐exploited.
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  • 74
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    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 47 (7). pp. 1685-1699.
    Publication Date: 2020-02-06
    Description: Seasonal variability in pathways of warm water masses toward the Kangerdlugssuaq Fjord-Glacier system (KF/KG), southeast Greenland, is investigated by backtracking Lagrangian particles seeded at the fjord mouth in a high-resolution regional ocean model simulation in the ice-free and the ice-covered seasons. The waters at KF are a mixture of Atlantic-origin water advected from the Irminger Basin (FF for Faxaflói), the deep waters from the Denmark Strait and the waters from the Arctic Ocean, both represented by the Kögur section (KO). Below 200m depth, the warm water is a mixture of FF and KO water masses, and is warmer in winter than in summer. We find that seasonal differences in pathways double the fraction of FF particles in winter, causing the seasonal warming and salinification. Seasonal temperature variations at the upstream sections (FF and KO) have a negligible impact on temperature variations near the fjord. Successful monitoring of heat flux to the fjord therefore needs to take place close to the fjord, and cannot be inferred from upstream conditions.
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  • 75
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    Taylor & Francis
    In:  Isotopes in Environmental and Health Studies, 53 (6). pp. 563-579.
    Publication Date: 2020-01-02
    Description: The spatial variations in the elemental and stable carbon, nitrogen, and sulphur isotope composition of bladder wrack (Fucus vesiculosus) growing along the shore line of the semi-enclosed urbanized Kiel Fjord (western Baltic Sea) was investigated at more than 60 sites. The analyses of the carbon-nitrogen-sulphur (CNS) stoichiometry and C and N stable isotope signature of F. vesiculosus displayed substantial differences between the north-western and the south-eastern parts of the Kiel Fjord. Different size classes displayed in part differences in C:N and C:S ratios, and the carbon isotope composition, reflecting the impact of the boundary conditions during growth. Whereas the sulphur isotope composition was controlled by the assimilation of seawater sulphate, the carbon isotope composition reflected the difference in the composition of surface waters. The δ15N values of the organic tissue tend to be an integrated monitor of anthropogenic impacts on the fjord. Results are compared to the composition of surface waters.
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  • 76
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    American Institute of Physics
    In:  Journal of the Acoustical Society of America, 92 (2). pp. 962-977.
    Publication Date: 2020-07-16
    Description: High‐frequency bottom acoustic and geoacoustic data from three well‐characterized sites of different bottom composition are compared with scattering models in order to clarify the roles played by interface roughness and sediment volume inhomogeneities. Model fits to backscattering data from two silty sites lead to the conclusion that scattering from volume inhomogeneities was primarily responsible for the observed backscattering. In contrast, measured bottom roughness was sufficient to explain the backscattering seen at a sandy site. Although the sandy site had directional ripples, the model and data agree in their lack of anisotropy.
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  • 77
    Publication Date: 2021-02-08
    Description: The fluttering shearwater (Puffinus gavia) is an abundant seabird endemic to breeding colonies in northern and central New Zealand. The species remains poorly studied, and here we present the first study to examine its breeding biology in detail. Fluttering shearwater nests were monitored daily from laying in September 2015 to fledging in January 2016 on Burgess Island (Mokohinau Islands group) in the outer Hauraki Gulf, northern New Zealand. Burrows were generally simple and non-branched. Eggs were laid over a period of 39 days with laying peaking 12th September. Incubation was 50 ± 3.7 days and chicks fledged after an average of 74 ± 4.3 days, from late December to the end of January. Chick development corresponds to the pattern observed for other Procellariiformes, gaining body mass rapidly to a maximum of 115% of adult mass, and then losing weight until fledging. Chicks were fed most nights throughout chick-rearing, indicating adult birds have access to a stable food supply close to the colony. Breeding success was 63.8% and similar to other Puffinus species. This study provides baseline biological data for a poorly studied, yet common, New Zealand endemics seabird. The obtained new information will allow for further ecological investigations and improved conservation management for the species
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  • 78
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    Taylor & Francis
    In:  Journal of Asian Natural Products Research, 17 (5). pp. 468-474.
    Publication Date: 2017-10-04
    Description: Chemical examination of the fermentation broth of a sponge-associated fungus Trichoderma harzinum HMS-15-3 led to the isolation of four pairs of new C13 lipid enantiomers namely harzianumols A–H (1a–4b). Their structures were elucidated on the basis of extensive spectroscopic (IR, MS, 1D, and 2D NMR) data analysis, including the modified Mosher's method for the assignment of their absolute configurations. The new compounds were evaluated for antihyperlipidemic effects in HepG2 cells.
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  • 79
    Publication Date: 2020-02-06
    Description: This study aimed to differentiate local and migratory spawning groups of the shortfin squid Illex argentinus caught in Brazilian waters using geometric and traditional morphometric methods and size-selective processes. The back-calculated length distributions reconstructed from daily growth increments deposited in the gladius allowed the identification of size-selective processes that may be related to different life history strategies. Landmark analysis on body shape (geometric morphometric) revealed that spawning groups presented significant ontogenetic variations in terms of body outline. In addition, traditional morphometric methods, based on multivariate analysis, associated juveniles of the expected migratory group (large size) and differentiated them from the local group individuals (small size). The changes in form, probably linked to the environmental gradients experienced by individuals throughout ontogeny, were interpreted as adaptations to improve swimming capacity. Migrant individuals have being differentiated from the smaller sizes group by body characteristics (broad fins, elongated and thicker mantle), which may increase the ability to perform long migrations.
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  • 80
    Publication Date: 2020-07-30
    Description: We investigated the biogeochemical constituents, microbial communities and functional genes (mcr and dsr) associated with anaerobic methane oxidation and sulfate reduction, and metabolic activities by sulfate reduction in the sulfate–methane transition zone (SMTZ) of gas-hydrate-bearing sediment of the Ulleung Basin in the East Sea. Maxima in the sulfate reduction rate (12.6 nmol cm¡3 d¡1), CO concentration (83 mM), and gene abundances of dsrA (9.1 £ 106 copies cm¡3) and mcrA (11.6 £ 106 copies cm¡3) occurred in the SMTZ. The peaks of CO consistently found in the SMTZ suggested that CO is an intermediate metabolic product related to methane oxidation. Candidate division JS1, the predominant bacterial group that comprised 59.0–63.7% of the 16S rRNA gene sequences, was recognized as an important organic carbon oxidizer. Both Marine Benthic Group D (MBGD) and Marine Benthic Group B (MBGB), which constituted 40.8–52.9 and 10.3–43.9% of the 16S rRNA gene sequences, respectively, were the dominant archaeal groups. Analysis of functional gene diversity revealed that anaerobic methanotroph-1-related phylotypes appeared to be the major CH4 oxidizer, whereas Firmicutes-like group was a predominant sulfate reducer in the 0.8 mbsf in SMTZ with low SO42¡ concentration. Overall results indicated that JS1 and two archaeal groups (MBGB and MBGD) seem to play a significant role in carbon and elements cycles in the gas-hydrate-bearing subsurface sediment of the Ulleung Basin.
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  • 81
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    AMS (American Meteorological Society)
    In:  Journal of the Atmospheric Sciences, 72 (7). pp. 2786-2805.
    Publication Date: 2019-01-08
    Description: In Ammassalik, in southeast Greenland, downslope winds can reach hurricane intensity and represent a hazard for the local population and environment. They advect cold air down the ice sheet and over the Irminger Sea, where they drive large ocean–atmosphere heat fluxes over an important ocean convection region. Earlier studies have found them to be associated with a strong katabatic acceleration over the steep coastal slopes, flow convergence inside the valley of Ammassalik, and—in one instance—mountain wave breaking. Yet, for the general occurrence of strong downslope wind events, the importance of mesoscale processes is largely unknown. Here, two wind events—one weak and one strong—are simulated with the atmospheric Weather Research and Forecasting (WRF) Model with different model and topography resolutions, ranging from 1.67 to 60 km. For both events, but especially for the strong one, it is found that lower resolutions underestimate the wind speed because they misrepresent the steepness of the topography and do not account for the underlying wave dynamics. If a 5-km model instead of a 60-km model resolution in Ammassalik is used, the flow associated with the strong wind event is faster by up to 20 m s−1. The effects extend far downstream over the Irminger Sea, resulting in a diverging spatial distribution and temporal evolution of the heat fluxes. Local differences in the heat fluxes amount to 20%, with potential implications for ocean convection.
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  • 82
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    AMS (American Meteorological Society)
    In:  Earth Interactions, 22 (1). pp. 1-15.
    Publication Date: 2021-02-08
    Description: Predicting tropical cyclone (TC) activity becomes more important every year while the understanding of what factors impact them continues to be complicated. El Niño–Southern Oscillation (ENSO) is one of the primary factors impacting the activities in both the Pacific and the Atlantic, but an extensive examination of the fluctuation in this system has yet to be studied in its entirety. This article analyzes the ENSO impacts on the Atlantic tropical cyclone activity during the assessed warm and cold years to show the dominant centennial-scale variation impact. This study looks to plausibly link this variation to the Southern Ocean centennial variability, which is rarely mentioned in any factors affecting the Atlantic tropical cyclone activity. This centennial variability could be used to enhance future work related to predicting tropical cyclones.
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  • 83
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    Taylor & Francis
    In:  Expert Review of Anti-infective Therapy, 15 (5). pp. 425-433.
    Publication Date: 2018-12-17
    Description: Introduction: The combination of growing antimicrobial resistance with a dry pipeline has resulted in infections that can no longer be treated. Specific reasons have led to companies’ exit from the antibacterial space, however recent incentives are spurring interest to reinvigorate the pipeline. Areas covered: This article summarizes the available information on the discovery, developmental, and regulatory challenges in antibacterial development that have led to disinterest in the space, as well as ongoing incentives such as public-private partnerships and streamlined pathways to mend these challenges and bring new antibiotics to patients in need. Expert commentary: Clinicians should not only understand the reasons for the decline in antibiotic development that have resulted in the dry pipeline, but also the ongoing initiatives in place to build an appropriate supply. Doing so will result in greater appreciation and prudent use of these life-saving drugs when they become available.
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  • 84
    Publication Date: 2018-03-05
    Description: During the ‘Meteor’ Expedition 13 in July and August 1990 to the northern part of the Norwegian Sea off west Spitsbergen, 7 stations with a depth of 2000 m or more were sampled with Agassiz trawl or hyperbenthos sledge, 14 more with a large box corer. Sponges were found at 6 of the trawl stations and in 2 box cores. A total of 19 species occurred, most of which were new to the area. Eight of the species were encountered more often than the other 11. Literature review and check of unpublished samples showed that by distribution, frequency of occurrence or abundance these species can be defined as the typical sponge association of the Norwegian and Greenland abyssal sea. This sponge association has a wide occurrence over the deep Norwegian-Greenland seas and parts of the Arctic basins. The analysis of substrate utilization of the 8 core species shows that all of them are able to colonize soft bottom, even some that previously had been considered to be dependent on hard substrate exclusively. Alternative substrate utilization and, in some species, the adoption of an infaunallife style are judged to be major reasons for the success of these species in the deep sea. The infaunal life style of the species Thenea abyssorum, Trichostemma sol and Tentorium semisuberites is documented and population structure data are given for the first time.
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  • 85
    Publication Date: 2018-03-07
    Description: The community of benthic organisms in the lower zone of a rocky shore at Praia Rasa, Brazil is distinctly patchy in structure. We examined the hypothesis that two types of patch (a. red algal turf and b. colonial coelenterate) represent different temporal stages in the same successional trajectory. We made observations on a) the stability of patch boundaries, b) successional sequence in experimental clearings within both patch types and c) species composition through time in undisturbed patches. In most cases, the coelenterate overgrew the algae at the patch boundaries, thus showing a competitive asymmetry. In the successional sequence, diatoms were followed by ulvoid species. Thereafter, within clearings in the algal patches, a red algal turf was once more established over one year. In contrast, the mid successional period in clearings within the coelenterate patch was characterized by very low cover of sessile organisms. Colonization by red algal turfs and by the coelenterate colony is largely dependent on vegetative spread. Thus later succession is not predictable on the basis of time alone. Supply-side processes are clearly of equal importance. Therefore it cannot be stated without qualification that patches of red algal turfs and colonial coelenterate at Praia Rasa are part of the same successional sequence.
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  • 86
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    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 22 (1). pp. 83-92.
    Publication Date: 2018-03-09
    Description: Antarctic Bottom Water flows into the western North Atlantic across the equator, shifting from the western side to the eastern side of the trough between the American continents and the Mid-Atlantic Ridge as it continues north. This is puzzling because such large-scale motion is thought to be controlled by dynamics that disallows an eastern boundary current. Previous explanations for the transposition involve a (necessarily small-scale) density current that changes sides because of the change in sign of rotation across the equator, or a topographic effect that changes the sign of the effective mean vorticity gradient and thus requires an eastern boundary current. Here an alternative explanation for the overall structure of bottom flow is given. A source of mass to a thin bottom layer is assumed to upwell uniformly across its interface into a less dense layer at rest. A simple formula for the magnitude of the upwelling and thickness of the layer is derived that depends on the source strength to the bottom layer. For a strong enough source, the bottom layer thickness is zero along a grounding curve that separates the bottom water from the western boundary and confines it to the east. A band of recirculating interior flow occurs, supplied by an isolated northern and western boundary current. Similar structures appear to exist in the Antarctic Bottom Water of the western North Atlantic.
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  • 87
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    Taylor & Francis
    In:  New Zealand Journal of Marine and Freshwater Research, 26 (1). pp. 37-51.
    Publication Date: 2018-03-21
    Description: A vertical mixing model was applied to a location off the west coast of the South Island, New Zealand, with the aim of simulating the seasonal cycle of temperature and mixed layer depth in the region. Observed weather data for 1973–89 were used to drive the model. Model results for sea temperature and mixed layer depth were compared to measurements from ships, moored temperature sensors, and satellites. The main features of the variations in temperature and mixed layer depth can be explained by the local meteorological forcing and vertical mixing, together with a general southward flow in the study area. Superimposed are short‐term variations which are obviously related to variable currents and the associated horizontal heat transport.
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  • 88
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    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 22 (11). pp. 1257-1273.
    Publication Date: 2018-03-16
    Description: Results of a three-dimensional primitive equation model are presented simulating turbulent mesoscale motions in the seasonal thermocline on an f plane. The model is based on a hybrid vertical coordinate scheme and conserves isopycnic potential vorticity. Mesoscale turbulence is modeled in terms of an unstable potential vorticity front. The model integration starts from a purely zonal, 60-km-wide geostrophically balanced jet, on which is superimposed a small initial perturbation. The most unstable mode exhibits a wavelength of 85 km and is driven by a mixed type of instability. Characteristic dynamical ingredients of the wave are enhanced cyclonic and anticyclonic relative vorticity in the troughs and the ridges, respectively, due to the curvature of the flow. Vertical motion of up to 10 m d−1 occurring downstream of the ridges (downwelling) and downstream of the troughs (upwelling) is driven by geostrophic advection of relative vorticity. The contrast of static stability across the front is changing during amplification of the instability: in troughs the stability is decreasing whereas in ridges it is increasing. The density field exhibits local anomalies of the isopycnals' depths (bumps) due to the ageostrophic cross-jet advection of potential vorticity streamers wound up in cyclones and anticyclones. Locally, the potential vorticity gradients are enhanced, creating a multiple front structure. The model results support observations and findings of earlier atmospheric and oceanic models. It is emphasized that mesoscale turbulent structures may have a profound influence on primary productivity, mixed-layer, and internal wave dynamics.
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  • 89
    Publication Date: 2018-03-20
    Description: Specimens of Siboglinum poseidon were collected by box coring and studied together with their undisturbed habitat. Occupied tubes occur in depse aggregations beneath the sediment surface directly at methane seep sites. Fertilized eggs develop into small larvae within the anterior transparent region of the tube. The oldest larvae observed in tubes measure c. 370 µm in length. It is concluded that released larvae develop in the sediment in the oxygenated top layer. Three tube types have been found: 1, the larval envelope; 2, the juvenile, transparent tube and 3, the ringed, adult tube. The smallest specimens recovered from the sediment measure c. 2 mm. They are complete with a tentacle, pyriform glands, bacteriocytes and juvenile opisthosoma. Some larvae were reared under laboratory conditions for 10 weeks. At that stage red blood becomes visible and a small tentacular bud is formed dorsally.
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  • 90
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    Taylor & Francis
    In:  International Journal of Environmental Analytical Chemistry, 47 (3). pp. 201-215.
    Publication Date: 2018-03-21
    Description: Kanechlor-300, -400, -500 and -600, Phenoclor DP-3, -4, -5 and -6 and Sovol mixtures were analyzed for their chlorobiphenyl (CB) composition using high-resolution one-dimensional and multidimensional gas chromatography-electron capture detection (MDGC-ECD) techniques. The congener patterns of tested Kanechlor and Phenoclor mixtures resembled Aroclor 1016, 1242, 1254 and 1260. However, differences in the percentage contribution of minor constituents were noticed among these mixtures, which could be due to variations in the boiling-point fractionation of these commercial products. CB pattern of Sovol was different from the rest of the mixtures tested. It showed a composition in between ca. 30%, 40%, 50% and 60% overall chlorine levels. MDGC-ECD study showed the presence of hitherto unnoticed non-CB compounds coeluting with CBs in some commercial PCBs. The use of these mixtures as quantitation standards should be considered with caution. CB patterns of Sovol and a water extract of the Gulf of Finland matched closely, indicating a point source contamination to these waters.
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  • 91
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    Taylor & Francis
    In:  Tellus B: Chemical and physical meteorology, 44 (2). pp. 150-159.
    Publication Date: 2018-03-21
    Description: A series of field experiments has been made to determine the occurrence of small-scale surface motions that might enhance gas exchange by surface renewal. Out of 93 runs under natural conditions on open bodies of water, only 19 gave no indication of surface streaming within a few seconds. The data cover the wind speed range up to about 6 ms-1. Above 2 or 3 ms-1, predominately line structures were observed. This points to an important r6le of surface renewal in gas exchange.
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  • 92
    Publication Date: 2021-02-08
    Description: Downward wave coupling (DWC) is an important process that characterizes the dynamical coupling between the stratosphere and troposphere via planetary wave reflection. A recent modeling study indicated that natural forcing factors, including sea-surface temperature variability and quasi-biennial oscillation, influence DWC and the associated surface impact in the Northern Hemisphere (NH). In light of this, we further investigate how DWC in the NH is affected by anthropogenic forcings, using a fully coupled chemistry-climate model CESM1 (WACCM). The results indicate that the occurrence of DWC is significantly suppressed in the future, starting later in the seasonal cycle, with more events concentrated in late winter (February-March). The future decrease in DWC events is associated with enhanced wave absorption in the stratosphere due to increased greenhouse gases. The enhanced wave absorption is manifest as more absorbing types of stratospheric sudden warmings, with more events concentrated in early winter. This early winter condition leads to a delay in the development of the upper stratospheric reflecting surface, resulting in a shift in the seasonal cycle of DWC towards late winter. The tropospheric responses to DWC events in the future exhibit different spatial patterns compared to those of the past. In the North Atlantic sector, DWC-induced circulation changes are characterized by a poleward shift and an eastward extension of the tropospheric jet, while in the North Pacific sector, the circulation changes are characterized by a weakening of the tropospheric jet. These responses are consistent with a change in the pattern of DWC-induced synoptic-scale eddy-mean flow interaction.
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  • 93
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    Taylor & Francis
    In:  Tellus A: Dynamic meteorology and oceanography, 45 (1). pp. 72-79.
    Publication Date: 2018-03-22
    Description: Climatological data sets are used to estimate the amount of water changing temperature and salinity at the sea-surface owing to air-sea exchanges. Considering this conversion as a function of sea-surface temperature and salinity leads to the definition of a conversion vector, which represents mass sources and sinks for each water type. The vector representation shows graphically the way the shape of the temperature-salinity relation is driven at the surface by the air-sea heat and fresh water fluxes.
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  • 94
    Publication Date: 2021-02-08
    Description: Decadal variabilities in Indian Ocean subsurface ocean heat content (OHC; 50–300 m) since the 1950s are examined using ocean reanalyses. This study elaborates on how Pacific variability modulates the Indian Ocean on decadal time scales through both oceanic and atmospheric pathways. High correlations between OHC and thermocline depth variations across the entire Indian Ocean Basin suggest that OHC variability is primarily driven by thermocline fluctuations. The spatial pattern of the leading mode of decadal Indian Ocean OHC variability closely matches the regression pattern of OHC on the interdecadal Pacific oscillation (IPO), emphasizing the role of the Pacific Ocean in determining Indian Ocean OHC decadal variability. Further analyses identify different mechanisms by which the Pacific influences the eastern and western Indian Ocean. IPO-related anomalies from the Pacific propagate mainly through oceanic pathways in the Maritime Continent to impact the eastern Indian Ocean. By contrast, in the western Indian Ocean, the IPO induces wind-driven Ekman pumping in the central Indian Ocean via the atmospheric bridge, which in turn modifies conditions in the southwestern Indian Ocean via westward-propagating Rossby waves. To confirm this, a linear Rossby wave model is forced with wind stresses and eastern boundary conditions based on reanalyses. This linear model skillfully reproduces observed sea surface height anomalies and highlights both the oceanic connection in the eastern Indian Ocean and the role of wind-driven Ekman pumping in the west. These findings are also reproduced by OGCM hindcast experiments forced by interannual atmospheric boundary conditions applied only over the Pacific and Indian Oceans, respectively.
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  • 95
    Publication Date: 2020-08-04
    Description: Downward wave coupling occurs when an upward propagating planetary wave from the troposphere decelerates the flow in the upper stratosphere, and forms a downward reflecting surface that redirects waves back to the troposphere. To test this mechanism and potential factors influencing the downward wave coupling, three 145-year sensitivity simulations with NCAR’s Community Earth System Model (CESM-WACCM), a state-of-the-art high-top chemistry-climate model, are analyzed. The results show that the QBO and SST variability significantly impact downward wave coupling. Without the QBO, the occurrence of downward wave coupling is significantly suppressed. In contrast, stronger and more persistent downward wave coupling occurs when SST variability is excluded. The above influence on the occurrence of downward wave coupling is mostly due to a direct influence of the QBO and SST variability on stratospheric planetary wave source and propagation. The strengths of the tropospheric circulation and surface responses to a given downward wave coupling event, however, behave differently. The surface anomaly is significantly weaker (stronger) in the experiment with fixed SSTs (without QBO), even though the statistical signal of downward coupling is strongest (weakest) in this experiment. This apparent mismatch is explained by the differences in the strength of the synoptic-scale eddy-mean flow feedback and the possible contribution of SST anomalies in the North Atlantic during DWC event. The weaker synoptic-scale eddy-mean flow feedback, and the absence of the positive NAO-related SST-tripole pattern in the fixed SST experiment are consistent with a weaker tropospheric response in this experiment. The results highlight the importance of synoptic-scale eddies in setting the tropospheric response to downward wave coupling.
    Type: Article , PeerReviewed
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  • 96
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    Unknown
    Taylor & Francis
    In:  Transactions of the Royal Society of South Africa, 39 (4). pp. 393-418.
    Publication Date: 2020-05-04
    Description: Four marine Cretaceous samples collected from the Agulhas Bank are discussed and their ostracodal assemblages described. Two of the samples are considered to be Lower Cretaceous, and the others Lower-Middle Senonian and Maastrichtian in age. Two new genera, twelve new species, and one new subspecies are described. Details of the foraminiferal assemblages are also given.
    Type: Article , PeerReviewed
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  • 97
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    Unknown
    Taylor & Francis
    In:  Transactions of the Royal Society of South Africa, 40 (3). pp. 155-165.
    Publication Date: 2020-05-04
    Description: Palaeogeographies of the Agulhas Bank for three low sea-level stages during the Pleistocene are presented (−140 m, −100 m and −50 m). Although they are specifically considered in relation to the last transgression (Flandrian, post-Weichsel/Würm), they are applicable to any of the previous glacial periods. In each case, the bedrock geology and expected superficial sediment cover are outlined, and general conclusions as to soil types, terrain, drainage, etc., are presented. The extended courses of local rivers in the Pleistocene are postulated from bathymetric and sedimentological data.
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  • 98
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    Unknown
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 20 (6). pp. 846-859.
    Publication Date: 2020-08-04
    Description: In this paper we use the historical hydrographic data base for the South Atlantic Ocean to investigate (i) the hydrographic boundary between the subtropical gyre and the Antarctic Circumpolar Current (ACC), the Sub-tropical Front (STF), and (ii) the southern current band of the gyre, which is called the South Atlantic Current (SAC). The STF begins in the west in the Brazil-Falkland (Malvinas) confluence zone, but at locations at and west of 45°W this front is often coincident with the Brazil Current front. East of 45°W the STF appears to be a distinct feature to at least the region south of Africa, whereupon it continues into the Indian Ocean. The associated current band of increased zonal speed is the SAC, which, except for one instance, is found at or north of the surface STF until Indian Ocean water from the Agulhas retroflection is reached. A reversal of baroclinicity in the STF is observed south of a highly saline Agulhas ring, causing the SAC to separate from the STF and turn north into the Benguela Current. Zonal flow south of the STF is generally weak and serves to separate the South Atlantic and circumpolar currents. In the Argentine Basin, the SAC has a typical volume transport of 30 Sv (1 Sv = 106m3s−1) in the upper 1000 m relative to a deep potential density surface (σ4 = 45.87 kg m−3), and can be as high as 37 Sv. It is thus comparable to, or stronger than, the Brazil Current. In the Cape Basin, the transport of the SAC is reduced to about 15 SY before it turns north to feed the Benguela Current. In late 1983 this flow was joined by about 8 Sv of water from the Agulhas Current.
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  • 99
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    Unknown
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 24 (10). pp. 2129-2141.
    Publication Date: 2018-04-05
    Description: In this study a scenario is developed of two adjacent Mediterranean Water eddies (meddies) as they were observed merging and drifting through the Iberian Basin. Observations are based on four RAFOS floats (at 850–1050 dbar), two hydrographic surveys (centered roughly at 38°N, 24°W), and trajectories of surface drifters (drogued at 100 m). In April 1991, the meddy A was identified and labeled by surface drifters. During the revisit one month later two meddies were encountered, B1 and B2, in the vicinity of the former meddy A. The coalescence of B1 (subsequently identified as A, one month older) and B2 is inferred from a simple kinematic model describing the observed movement of the RAFOS floats for up to three months after the second CTD survey. The deduced vorticity front, radius ∼15 km, within B1 was of insufficient strength to keep the core waters of B1 isolated and prevent the absorption of B1 by B2. The resulting meddy (B1 + B2) showed a clear near-surface dynamical signal. Its deep root (1800 m) could explain the expulsion from the meddy of the remaining RAFOS float and surface drifter at the time of the meddy's collision with the Josephine Seamount. For the first time, a set of Lagrangian and hydrographic observations give direct evidence that neighboring meddies can merge as predicted by theoretical considerations.
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  • 100
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    Unknown
    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 23 (12). pp. 2667-2682.
    Publication Date: 2018-04-05
    Description: The total transport of Antarctic Bottom Water across the Rio Grande Rise, including the western boundary, the Vema Channel, and the Hunter Channel is estimated from hydrographic measurements across these pathways. The contribution of the Vema Channel is greatest at 3.9 × 106 m3 s−1, which is very close to earlier estimates. The western boundary current contribution is 2.0 × 106 m3 s−1 and that of the Hunter Channel 0.7 × 106 m3 s−1. The lower values outside the Vema Channel are offset by the important source of mass they form to the lower density classes of bottom water. About 40% of the flow is concentrated in the highest density class representing the source of Weddell Sea Deep Water to the Brazil Basin. The flow structure is characterized by horizontal and vertical recirculation.
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