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  • Other Sources  (125)
  • Elsevier  (84)
  • AGU (American Geophysical Union)  (39)
  • American Association of Petroleum Geologists (AAPG)
  • Wiley-Blackwell
  • 2000-2004  (125)
  • 1980-1984
  • 1945-1949
  • 2001  (125)
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  • 2000-2004  (125)
  • 1980-1984
  • 1945-1949
Year
  • 1
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    Geochemistry and Fluid Flow (2001)
    Elsevier
    In:  Amsterdam, 300 pp., Elsevier, vol. 34, no. 22, pp. 65-70, (ISBN 3-7643-0253-4)
    Details
    Publication Date: 2001
    Keywords: Fluids ; Textbook of geophysics ; Geochemistry
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Processes and consequences of deep subduction (2001)
    Elsevier
    In:  Amsterdam, 298 pp., Elsevier, vol. 70, no. Publ. No. 12, pp. 1039-1054, (ISBN 0-444-50971-2)
    Details
    Publication Date: 2001
    Keywords: Subduction zone ; Review article ; Hypocentral depth ; Fault plane solution, focal mechanism ; Seismicity ; Mineralogy ; Hilst ; triggering ; Stress ; Rheology ; Geochemistry ; Strength ; Fluids ; ConvolutionE
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    BIBLIOGRAPHY SEISMOLOGY
  • 3
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    Seismic Signatures and Analysis of Reflection Data in Anisotropic Media (2001)
    Elsevier
    In:  Amsterdam, Elsevier, vol. 10, no. ALEX(01)-FR-77-01, AFTAC Contract F08606-76-C-0025, pp. 329, (ISBN: 0-08-043649-8)
    Details
    Publication Date: 2001
    Description: Following the breakthrough in the last decade in identifying the key parameters for time and depth imaging in anisotropic media and developing practical methodologies for estimating them from seismic data, this title primarily focuses on the far reaching exploration benefits of anisotropic processing. This volume provides the first comprehensive description of reflection seismic signatures and processing methods in anisotropic media. It identifies the key parameters for time and depth imaging in transversely isotropic media and describes practical methodologies for estimating them from seismic data. Also, it contains a thorough discussion of the important issues of uniqueness and stability of seismic velocity analysis in the presence of anisotropy. The book contains a complete description of anisotropic imaging methods, from the theoretical background to algorithms to implementation issues. Numerous applications to synthetic and field data illustrate the improvements achieved by the anisotropic processing and the possibility of using the estimated anisotropic parameters in lithology discrimination.
    Keywords: Textbook of geophysics ; Seismics (controlled source seismology) ; Reflection seismics ; Anisotropy
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    BIBLIOGRAPHY SEISMOLOGY
  • 4
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    The Theory of Inductive Prospecting (2001)
    Elsevier
    In:  Amsterdam, 680 pp., Elsevier, vol. 33, no. 2, pp. 125-169, (ISBN: 3-540-42642-6, Approx. 620 p. 30 illus., Hardcover)
    Details
    Publication Date: 2001
    Keywords: Borehole geophys. ; Textbook of geophysics ; Electromagnetic methods/phenomena
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    BIBLIOGRAPHY SEISMOLOGY
  • 5
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    Statistics for Petroleum Engineers and Geoscientists (2001)
    Elsevier
    In:  Amsterdam, 356 pp., Elsevier, vol. 2, no. XVI:, pp. 1-14, (ISBN: 0-387-30752-4)
    Details
    Publication Date: 2001
    Keywords: Textbook of engineering ; Textbook of geophysics ; Statistical investigations
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    BIBLIOGRAPHY SEISMOLOGY
  • 6
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    Submarine landslides around the Canary Islands (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Solid Earth, 106 (B3). pp. 3977-3997.
    Details
    Publication Date: 2019-04-08
    Description: The morphology and structure of the submarine flanks of the Canary Islands were mapped using the GLORIA long-range side-scan sonar system, bathymetric multibeam systems, and sediment echosounders. Twelve young (〈2 Ma) giant landslides have been identified on the submarine flanks of the Canary Islands up to now. Older landslide events are long buried under a thick sediment cover due to high sedimentation rates around the Canary Islands. Most slides were found on the flanks of the youngest and most active islands of La Palma, El Hierro, and Tenerife, but young giant landslides were also identified on the flanks of the older (15–20 Ma) but still active eastern islands. Large-scale mass wasting is an important process during all periods of major magmatic activity. The long-lived volcanic constructive history of the islands of the Canary Archipelago is balanced by a correspondingly long history of destruction, resulting in a higher landslide frequency for the Canary Islands compared to the Hawaiian Islands, where giant landslides only occur late in the period of active shield growth. The lower stability of the flanks of the Canaries is probably due to the much steeper slopes of the islands, a result of the abundance of highly evolved intrusive and extrusive rocks. Another reason for the enhanced slope instability is the abundance of pyroclastic deposits on Canary Islands resulting from frequent explosive eruptions due to the elevated volatile contents in the highly alkalic magmas. Dike-induced rifting is most likely the main trigger mechanism for destabilization of the flanks. Flank collapses are a major geological hazard for the Canary Islands due to the sector collapses themselves as well as triggering of tsunamis. In at least one case, a giant lateral blast occurred when an active magmatic or hydrothermal system became unroofed during flank collapse.
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  • 7
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    The earliest Pleistocene(?) Orange River fan-delta: an example of successful exploration delivery aided by applied Quaternary research in diamond placer sedimentology and palaeontology (2001)
    Elsevier
    In:  Quaternary International, 82 (1). pp. 63-73.
    Details
    Publication Date: 2017-07-07
    Description: Understanding how complex, highly variable sedimentary systems interact in time and space to release, transport and concentrate diamonds is the basis for successful exploration strategies for placer diamond deposits. De Beers’ and Namdeb's West Coast operations are widely involved in a variety of applied scientific research to unravel the complex interactions of Cainozoic fluvial, marine and aeolian systems that have contributed to the formation of the most spectacular gem diamond placer in the world. Geological models produced not only provide the basis for exploration target selection but also high-resolution orebody characterisation, a prerequisite for high confidence geostatistical evaluation, mining system design and mine planning. This paper draws on some of the many applied research projects that have contributed to De Beers’ and Namdeb's placer exploration success that continues to deliver new mineral resources on the West Coast. The history of the Orange River has, and continues to be intensively studied both on- and offshore as the principal conduit for diamond introduction to the continental margin. Use of the “Jago” submersible has introduced a new dimension to offshore sedimentological studies on the continental shelf through direct seafloor observation, which helped us to identify the latest deep-water offshore development—the late Pliocene/early Pleistocene Orange River fan-delta.
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  • 8
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    Coelacanths: a human responsibility (2001)
    Wiley-Blackwell
    In:  Journal of Fish Biology, 59 . pp. 332-338.
    Details
    Publication Date: 2017-07-06
    Description: The living coelacanth Latimeria chalumnae has a unique position in world biodiversity which raises important questions about conservation and ethics. Some relevant details of coelacanth biology are summarized, including those obtained by direct observation from submersibles. The importance of the coelacanth for evolutionary theory and palaeontology is shown to be paralleled in cultural, literary and artistic areas of human heritage. Threats to the Comoran coelacanths from artisanal fishing are described and conservation measures discussed in relation to local customs and economies as well as the promotion of tourism to spread a new awareness and concern for coelacanths worldwide.
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  • 9
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    The timing of partial melting, Barrovian metamorphism and granite intrusion in the Naxos metamorphic core complex, Cyclades, Aegean Sea, Greece (2001)
    Elsevier
    In:  Tectonophysics, 342 (3-4). pp. 275-312.
    Details
    Publication Date: 2020-05-13
    Description: The relationship between partial melting and granite intrusion in a classic Barrovian metamorphic terrane has been assessed. Thirteen samples were dated by SHRIMP U–Pb zircon geochronology from the island of Naxos, Greece, one of the Aegean metamorphic core complexes. The effect of partial melting during peak Barrovian metamorphism on Naxos is recorded by fine (〈30 mm) zircon overgrowths surrounding older cores in seven of nine samples of migmatite analyzed. The ages of these overgrowths suggest that partial melting commenced prior to 20.7 Ma. The timing of partial melting on Naxos also constrainsthe onset of extensional tectonism in the area to pre-20.7 Ma. The preservation of zircon overgrowth rims with distinctly different concordant ages, ranging from 20.7 to 16.8 Ma, both from different samples and from within the one handspecimen, suggests that zircon precipitation, associated with the partial melting process, was episodic over this age range on both local(cm) and regional (km) scales. Zircons from four granite intrusives were also dated and range in age from 15.4 to 11.3 Ma, with the main period of magmatic activity at ca. 12 Ma, clearly post-dating metamorphism. The sequence of partial melting, Barrovian metamorphism and magmatism in the Naxos metamorphic core complex can be related to a change from overall crustal shortening to extensional tectonism in the Aegean region, caused by post-collisional roll-back of the subducting African slab along the Hellenic trench system.
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  • 10
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    Tectono-metamorphic evolution of Syros and Sifnos islands (Cyclades, Greece) (2001)
    Elsevier
    In:  Tectonophysics, 338 (2). pp. 179-206.
    Details
    Publication Date: 2020-05-13
    Description: Miocene exhumation of metamorphic rocks in the Aegean Sea is partly a consequence of post-orogenic extension. If the post-orogenic mechanism of exhumation is rather well understood, the earlier syn-orogenic Eocene exhumation is still largely enigmatic. Previous authors have argued in terms of extension or compression. New structural and petrological data on Sifnos and Syros islands show that exhumation of high pressure–low temperature (HP–LT) rocks involves crustal-scale extensional ductile shear zones during the Eocene. We observe a continuum of top-to-the-NE and -E ductile shear from the Eocene (in the blueschist facies) to the Miocene (in the greenschist facies). This deformation is distributed in the eclogites and blueschists, whereas it is rather localised along ductile shear zones in the greenschists. Eclogites, which are preserved only at the top of the structural pile, are exhumed with a ‘cold’ retrograde P–T path. In the lower part of the structural pile we observe a progressive retrogression of eclogites in blueschist then greenschist facies. This lower part of pile is subsequently exhumed with P–T paths showing a nearly isothermal decompression before cooling. P–T–t-deformation data suggest that the Cycladic blueschists are progressively exhumed by a continuum of accretion at the base of the orogenic wedge, and by a partly non-coaxial extensional deformation above, distributed during the syn-orogenic stage, then localised during the post-orogenic stage. We then compare the mechanism of syn-orogenic exhumation of Crete and the Cyclades and we discuss a simple geodynamic scenario for the Aegean domain and the external Hellenides which accounts for (1) the southward migration of the Hellenic trench and arc during the Cenozoic; (2) the P–T–t-deformation data for the Cycladic blueschists and the Phyllite–quartzite nappe; and (3) the transition from syn-orogenic to post-orogenic in the Cyclades.
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  • 11
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    Protein synthesis (2001)
    Elsevier
    In:  In: Nitrogen Excretion. Fish physiology, 20 . Elsevier, San Diego, pp. 31-75. ISBN 0-12-350444-9
    Details
    Publication Date: 2018-03-08
    Description: Protein synthesis is fundamental to all living organisms and it has been studied intensively and at varying levels of complexity. This chapter provides a comprehensive review of research on protein synthesis in fish, examines data to produce simple models describing protein synthesis in terms of key variables, and provides explanations for variations from expected or predicted rates of protein synthesis. The underlying there is to integrate information at the organismal level. A variety of methods for measuring protein synthesis have been used and comparison suggest they give similar results for fish. Major influences on protein synthesis are species, life-history stage, temperature, feeding, and nutrition. The effects of other factors such as pollutants, anoxia, salinity, and hormones have also been investigated. In growing fish between 20 and 50% of energy expenditure is associated with protein synthesis. Protein synthesis is, therefore, a major energy-demanding process in fish that is influenced by many environmental and biotic factors.
    Type: Book chapter , NonPeerReviewed
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  • 12
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    Spatial and temporal variability of particle flux at the N.W. European continental margin (2001)
    Elsevier
    In:  Deep Sea Research Part II: Topical Studies in Oceanography, 48 (14-15) . pp. 3083-3106.
    Details
    Publication Date: 2020-08-05
    Description: A synopsis of results from two sediment trap moorings deployed at the mid- and outer slope (water depths 1450 and 3660 m, respectively) of the Goban Spur (N.E. Atlantic Margin) is presented. Fluxes increase with trap deployment depth; below 1000 m resuspended and advected material contributes increasingly to bulk flux. Fluxes of dry weight, POC and diatoms in the traps 400 m above bottom (mab) are smaller than those recorded at the sediment surface due to lateral fluxes in the benthic nepheloid layer. These near-bottom fluxes are larger at shallower water depths. 231Pa/230Th ratios in sedimenting material suggest that boundary scavenging is not significant at the Goban Spur. Fluxes of 210Pb in the intermediate and deep traps are comparable to the 210Pb supply rate at this site. At the outer slope, sediment 210Pb fluxes are similar to those measured in the traps 400 mab; at the mid-slope they are a factor of 2 higher, once again indicating large near-bottom lateral particle input. Based on POC-normalised biomarkers in sedimenting material, we followed changes in the quality of sedimenting material with differing trap depth and on seasonal and event-related time scales. In spring fresh, diatom-dominated sedimentation occurs, with progressive degradation of POC with time (to winter) and depth (from 600 to 3220 m). Deeper traps are distinguished on the basis of opal and aluminium fluxes that are dominant in lateral input. A storm event during late September 1993 was clearly reflected in the δ15N isotope ratio of sedimenting material, with a time lag of 2–3 weeks. Diatom and opal fluxes were elevated in this storm-related signal, and its biomarker composition in the 600-m trap was similar to that during spring. An estimate made of upward nitrate flux (new production) at the shelf break and at the outer slope indicated a 2-fold higher new (export) production at the shelf break. Particulate organic carbon export from the shelf break to below the depth of maximal seasonal mixing ranges between 3 and 9% of primary production.
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  • 13
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    Circulation Characteristics in Three Eddy-Permitting Models of the North Atlantic (2001)
    Elsevier
    In:  Progress in Oceanography, 48/2-3 . pp. 123-162.
    Details
    Publication Date: 2016-10-07
    Description: A systematic intercomparison of three realistic eddy-permitting models of the North Atlantic circulation has been performed. The models use different concepts for the discretization of the vertical coordinate, namely geopotential levels, isopycnal layers, terrain-following (sigma) coordinates, respectively. Although these models were integrated under nearly identical conditions, the resulting large-scale model circulations show substantial differences. The results demonstrate that the large-scale thermohaline circulation is very sensitive to the model representation of certain localised processes, in particular to the amount and water mass properties of the overflow across the Greenland–Scotland region, to the amount of mixing within a few hundred kilometers south of the sills, and to several other processes at small or sub-grid scales. The different behaviour of the three models can to a large extent be explained as a consequence of the different model representation of these processes.
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  • 14
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    A 300000 years coral reef record of sea level changes, Mururoa atoll (Tuamotu archipelago, French Polynesia) (2001)
    Elsevier
    In:  Palaeogeography, Palaeoclimatology, Palaeoecology, 175 . pp. 325-341.
    Details
    Publication Date: 2020-08-07
    Description: The accurate dating of fossil coral reefs is of prime importance in determining the timing of deglaciation events and thus understanding the mechanisms driving glacial–interglacial cycles. So far, the most useful coral reef records of past sea level changes are those related to the last deglaciation and the Last Interglacial period. U/Th ages for older isotopic stages are more limited, due to the scarcity of datable material, reflecting diagenetic alteration. Most data are from emergent parts of reefs and reef terraces in active subduction zones where relative sea level records may be biased by variations in rates of tectonic uplift. New constraints on sea level changes over the past 300 000 yr are based on high-precision U-series age measurements of successive reef units on Mururoa. These have been cored in four continuous 300-m-long drill holes with seaward inclinations of 30 to 45° on the northeastern rim of the atoll. Past sea level positions have been calculated from the radiometric ages of corals by correcting the present depth of subsurface horizons both for thermal subsidence and for depositional palaeodepth. The location of this atoll at a considerable distance from former ice sheets (‘far field’) minimises the influence of glacio–isostatic rebound. Prominent units formed during four periods of relative sea level highstands, including the Holocene and stages 5 (∼125 ka), 7 (∼212 ka) and 9 (∼332 ka). These are primarily composed of coralgal frameworks that grew in very shallow water. Three periods of relative low stand correspond to stages 2 (∼17–23 ka), 4 (∼60 ka) and 8 (∼270 ka) during which small reefs developed in association with large bioclastic accumulations. Good agreement with the timing of sea level changes based on oxygen isotope measurements in deep-sea cores is noted for most of the dated reef units. We report here the first accurate coral record of the Last Glacial Maximum in the Pacific, 135–143 m below the present sea surface, suggesting that sea level may have been lower than expected during this period.
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  • 15
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    A comprehensive phylogeny of the Phaeophyceae based on nrDNA sequences resolves the earliest divergences (2001)
    Elsevier
    In:  Comptes Rendus de l Academie des Sciences - Series III - Sciences de la Vie, 324 (4). pp. 305-319.
    Details
    Publication Date: 2019-09-24
    Description: The present study is the first comprehensive phylogeny of the class of the Phaeophyceae. For 67 species representing all orders of the class, the sequences of the 3’-end of the small and the 5ˈ-end of the large subunit nrRNA genes were aligned and analysed. A further analysis based on sequences of the 3’-end of the small and of the complete sequences of the 28S gene of the large subunits was also performed, but for only eight taxa. In both analyses, Tribonema marinum (Xanthophyceae) was used as outgroup. The analyses showed the Dictyotales as diverging first, followed by the Sphacelariales, then the Syringodermatales. Most of the orders currently accepted were confirmed as monophyletic groups but the Laminariales and Tilopteridales remained polyphyletic. The relationships of the remaining orders to each other were not resolved with the present data set. Ascoseira, included for the first time in a molecular study, appeared as a separate lineage without any clear relationship with other algae possessing conceptacles (Splachnidium and Fucales). Algae with stellate plastids, never studied in a global context, were polyphyletic; this result is consistent with their plastid ultrastructure and is discussed in detail. As further result of the present study, the South African genus Bifurcariopsis appeared as the sister taxon of the North Atlantic genus Himanthalia, and Xiphophora appeared as the sister taxon of Hormosira rather than as a member of the Fucaceae; the taxonomic position of these genera is discussed.
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  • 16
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    Assimilation of Altimetric Data into an Eddy-Permitting Model of the North Atlantic (2001)
    Elsevier
    In:  Progress in Oceanography, 48 (2-3). pp. 313-315.
    Details
    Publication Date: 2019-09-23
    Description: This paper shows that the mean flow of an eddy-permitting model can be altered by assimilation of surface height variability, providing that information about the mean sea surface is included, using an adaption of a statistical–dynamical method devised by Oschlies and Willebrand. We show that for a restricted depth range (about 1000 m), dynamical knowledge can make up for the null space present in surface data whose temporal extent may be too short to distinguish between vertical modes. The lack of an accurate geoid has meant that most assimilation methods, while representing variability well, have been unable to modify the mean flow to any extent. However, we show that by including several approximate forms for the mean sea surface, the mean interior flow in the upper kilometer can be rapidly adjusted towards reality by the assimilation, with the location of major current systems moved by hundreds of kilometers.
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  • 17
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    The role of variable wind forcing in generating eddy energy in the North Atlantic (2001)
    Elsevier
    In:  Progress in Oceanography, 48 (2-3). pp. 289-312.
    Details
    Publication Date: 2016-10-07
    Description: Seasonal changes in eddy energy are used to investigate the role of high-frequency wind forcing in generating eddy kinetic energy in the oceans. To this end, we analyze two experiments of an eddy-permitting model of the North Atlantic driven by daily and monthly mean wind stress fields, and compare results with corresponding changes in the variance of the wind fields, and related results from previous studies using altimeter and current meter data. With daily wind-stress forcing the model is found to be in general agreement with altimetric observations and reveal a complex pattern of temporal changes in variability over the North Atlantic. Observations and the model indicate enhanced levels of eddy energy during winter months over several areas of the northern and, particularly northeastern North Atlantic. Since the wind-generated variability is primarily barotropic, its signal can be detected mostly in the low-energy regions of the northern and north-eastern North Atlantic, which are remote from baroclinically unstable currents. There the winter-to-summer difference in simulated eddy kinetic energy caused by the variable wind forcing is 〈0.5 cm2 s2 between 30° and 55°N, and is 1–3 cm2 s2 north of 55°N. Seasonal changes in kinetic energy are insignificant along the path of the North Atlantic current and south of about 30°N. The weak depth dependence of the seasonal changes in eddy energy implies that the relative importance of wind-generated eddy energy is maximum at depth where the general (baroclinic) variability level is low. Accordingly, a significant correlation is found between the seasonal cycle in the variance of wind stress and the seasonal cycle in eddy energy over a substantially wider area than near the surface, notably across the entire eastern North Atlantic between the North Atlantic Current and the North Equatorial Current.
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  • 18
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    Changes of ENSO Stability due to Greenhouse Warming (2001)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 28 . pp. 2064-2066.
    Details
    Publication Date: 2018-02-14
    Description: Based on a Coupled General Circulation Model (CGCM) simulation we study the influence of anthropogenic greenhouse warming on the stability of the El Niño-Southern Oscillation phenomenon (ENSO). The linear stability of such a complex model cannot be assessed directly, hence we will derive empirical low order models for ENSO from the CGCM simulation under consideration. These models capture essential features of ENSO and are sensitive also to temporal changes in ENSO statistics. An eigenvalue analysis of these reduced models reveals that as greenhouse warming progresses a transition takes place from a stable oscillatory behavior to an unstable oscillation. This transition coincides with an abrupt change in simulated ENSO activity and can be explained in terms of changing ocean dynamics.
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  • 19
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    Mixing analysis of nutrients, oxygen and inorganic carbon in the Canary Islands region (2001)
    Elsevier
    In:  Journal of Marine Systems, 28 . pp. 183-201.
    Details
    Publication Date: 2017-07-12
    Description: We show the distribution of nutrients, oxygen, total dissolved inorganic carbon (CT) and total alkalinity (AT) along three sections close to the Canary Islands, between 18°W and the African coast during Meteor 37/2 cruise (January 1997). From the thermohaline properties of Eastern North Atlantic Central Water (ENACW), Mediterranean Water (MW), Antarctic Intermediate Water (AAIW) and North Atlantic Deep Water (NADW), a mixing model has been established based on the water mass description. It can explain most of the variabilities found in the distribution of the chemical variables, including the carbon system, and it is validated through the use of conservative chemical variables like ‘NO.’ From nutrients, oxygen, AT and CT, the chemical characterisation of the water masses was performed by calculating the concentration of these variables in the previously defined thermohaline end-members. The relative variation of nutrient concentrations, resulting from the regeneration of organic matter, was estimated. Close to the African shelf-break, a poleward undercurrent conveying as much as a 11% of AAIW was observed only in the southern section (28.5°N). From the chemical and thermohaline properties of the end-members, a comparison with data from other oceanic regions was made in respect to conservative chemical variables (‘NO’). In addition, a north–south gradient in the ventilation pattern of water masses is observed from the residuals of the model.
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  • 20
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    On the dynamics of internal waves in a nonlinear, weakly nonhydrostatic three-layer ocean (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 106 . 26,899-26,916.
    Details
    Publication Date: 2018-04-18
    Description: Aspects of the dynamics of internal solitary waves evolving in a three-layer ocean are investigated using a new numerical multilayer model that solves the nonlinear, weakly nonhydrostatic Boussinesq equations and uses high-resolution in situ data. The model applications refer to two different phenomena frequently observed in the real ocean, which can be described using a three-layer model rather than a two-layer model. In the first application the influence of the strength of a shallow seasonal thermocline superimposed on a two-layer permanent stratification on the structure of internal solitary waves is studied. It is found that while for small to medium wave amplitudes a decrease in the strength of the thermocline yields an increase in the simulated wavelengths, for large wave amplitudes this dependence is no longer monotonic. In particular, in the limiting case of a vanishing thermocline, first-mode internal solitary wave solutions of the three-layer numerical model tend to the analytical internal solitary wave solutions of the Miyata equations, a two-layer model, in which the full nonlinearity of the shallow-water theory up to first-order phase dispersion is retained. In the second application that refers particularly to high-resolution observations made north and south of the Strait of Messina in the Eurafrican Mediterranean basin the generation of internal solitary waves by the evolution of surface and subsurface water jets is investigated. The analysis of the in situ data shows in fact that from very energetic surface and subsurface jet-like disturbances subject to strong turbulent mixing internal solitary waves emerge as robust, quasi-nondissipative oceanic features. Idealized flow conditions aimed at approximating possible initial stages of the observed water jets are imposed to force our numerical model. In general, good agreement is found between characteristics of observed and simulated wave fields. Our investigation identifies the observed water jets as peculiar features of the complex ocean dynamics and suggests that layered numerical models can represent helpful tools in understanding fundamental processes inherent in their intricate dynamics.
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  • 21
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    The importance of water storage variations for water balance studies of the Baltic Sea (2001)
    Elsevier
    In:  Physics and Chemistry of The Earth Part B-Hydrology Oceans and Atmosphere, 26 (5-6). pp. 383-389.
    Details
    Publication Date: 2019-09-23
    Description: The closing of the water and energy cycle of the Baltic Sea is one of the main aims of BALTEX (Baltic Sea Experiment), which particularily focuses on the exploration, modelling and quantification of the various processes determining the space and time variability of the energy and water budget. On the long-term mean the water budget of the Baltic Sea is determined by river runoff, net precipitation (precipitation minus evaporation) and the in- and outflows through the Baltic Sea entrance area, assuming that the mean sea level remains constant, i.e. the ability of the Baltic Sea to store a huge amount of water is averaged out over the long-term period. For shorter periods, the water storage which can be expressed by the mean sea level plays an important role on the water budget. The objective of the present study is to investigate the variability of the water storage of the Baltic Sea and relate its fluctuations to the different components of the water balance equation. The anomaly of the mean sea level of the Baltic Sea shows a well pronounced seasonal cycle, with negative values between the end of February to the end of June (minimum in the middle of May), and positive anomalies from July to mid-February (maximum in January). There is a high correlation between the mean sea level expressed by the Landsort tide gauge and the local atmospheric conditions over the Baltic Sea. The annual course of the total water balance is controlled by the local atmospheric conditions with the net fresh-water inflow only controls the general outflow conditions. Sea level, precipitation and river runoff have been obtained from observations provided by the SMHI. For the in- and outflow through the entrance area of the Baltic Sea and evaporation over the open ocean, coupled sea ice-ocean model simulations for a 10-years period have been utilized.
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  • 22
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    Transport estimates in the Strait of Gibraltar with a tidal inverse model (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 106 (C12). 31,033-31,044.
    Details
    Publication Date: 2018-04-18
    Description: To estimate the volume transport through the Strait of Gibraltar and to study the spatial structure of the time-variable flow, a varying number of current meter moorings were maintained at the eastern entrance of the strait between October 1994 and April 1998, and was complemented with intensive shipboard measurements during the European Union project Canary Island Azores Gibraltar Experiment (CANIGO). A tidal inverse model is used to merge these data sets in order to investigate the flow at the eastern entrance of the strait. The two-dimensional structure of the tidal flow was described by simple analytical functions. Harmonics with the seven most important tidal frequencies were used as temporal functions. With this model, the tidal currents can be predicted for any time and location at the eastern entrance of the strait, and more than 92% of the variance of the lower layer flow is explained. It was used to remove the tidal currents from the individual measurements and to calculate the mean flow through the strait from the residuals. Combined with a similar inverse model for determining the depth of the interface between Mediterranean and Atlantic water, the volume transport was estimated to be 0.81 ± 0.07 Sv for the upper layer and −0.76 ± 0.07 Sv for the lower layer. The correlation of the tidal currents and the fluctuations of the interface accounts for ∼7% of the transport at the eastern entrance.
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  • 23
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    Export of Weddell Sea Deep and Bottom Water (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 106 . pp. 9005-9017.
    Details
    Publication Date: 2018-04-18
    Description: An extensive set of conductivity-temperature-depth (CTD)/lowered acoustic Doppler current profiler (LADCP) data obtained within the northwestern Weddell Sea in August 1997 characterizes the dense water outflow from the Weddell Sea and overflow into the Scotia Sea. Along the outer rim of the Weddell Gyre, there is a stream of relatively low salinity, high oxygen Weddell Sea Deep Water (defined as water between 0° and −0.7°C), constituting a more ventilated form of this water mass than that found farther within the gyre. Its enhanced ventilation is due to injection of relatively low salinity shelf water found near the northern extreme of Antarctic Peninsula's Weddell Sea shelf, shelf water too buoyant to descend to the deep-sea floor. The more ventilated form of Weddell Sea Deep Water flows northward along the eastern side of the South Orkney Plateau, passing into the Scotia Sea rather than continuing along an eastward path in the northern Weddell Sea. Weddell Sea Bottom Water also exhibits two forms: a low-salinity, better oxygenated component confined to the outer rim of the Weddell Gyre, and a more saline, less oxygenated component observed farther into the gyre. The more saline Weddell Sea Bottom Water is derived from the southwestern Weddell Sea, where high-salinity shelf water is abundant. The less saline Weddell Sea Bottom Water, like the more ventilated Weddell Sea Deep Water, is derived from lower-salinity shelf water at a point farther north along the Antarctic Peninsula. Transports of Weddell Sea Deep and Bottom Water masses crossing 44°W estimated from one LADCP survey are 25 × 106 and 5 × 106 m3 s−1, respectively. The low-salinity, better ventilated forms of Weddell Sea Deep and Bottom Water flowing along the outer rim of the Weddell Gyre have the position and depth range that would lead to overflow of the topographic confines of the Weddell Basin, whereas the more saline forms may be forced to recirculate within the Weddell Gyre.
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  • 24
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    Small scale variability of benthic assemblages: biogenic neighborhood effects (2001)
    Elsevier
    In:  Journal of Experimental Marine Biology and Ecology, 258 (1). pp. 101-114.
    Details
    Publication Date: 2014-01-23
    Description: In this study, patterns of community development were investigated within vs. outside 'habitats'. These habitats represented five different monospecific assemblages of one of the following species: the brown alga Fucus serratus, the red alga Delesseria sanguinea, the green alga Enteromorpha intestinalis, the seagrass Zostera marina and the blue mussel Mytilus edulis. Natural assemblages were allowed to develop on paired artificial substrata-separated by ca. 1 m -within (treatment) vs, outside (control) of habitats. The same colonizer species settled on treatment and control substrata for given habitats. However, after 5 months of settlement and post-settlement dynamics, their proportional abundance and the structure of treatment and control assemblages differed in many instances. Variability among replicates of a given treatment, seperated by up to 50 m, was large, indicating a patchy spatial distribution of organisms. Despite this spatial heterogeneity among within-treatment replicates, analysis of similarity revealed that in most instances significantly different assemblages developed between treatments on a small spatial scale depending on whether substrate were positioned within as compared to outside a, given habitat. Consequently, the algae, seagrass or mussels constituting a habitat seem to control the structure of the benthic assemblage developing in their vicinity by one or more possible mechanisms: reduction of larval advection, exudation of metabolites that influence settlement and/or post-settlement survival, and/or-in the case of mussel assemblages-predation on larvae. In addition to spatial variability in larval supply, stochasticity in succession, substratum heterogeneity, competition and predation effects, this investigation reveals the potential of a further assemblage structuring factor: the impact of neighboring organisms
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  • 25
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    Age Tracers in an Ocean GCM (2001)
    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 48 (6). pp. 1423-1441.
    Details
    Publication Date: 2016-09-30
    Description: Observations of transient tracers such as tritium and helium-3 Full-size image (〈1 K) are frequently combined to construct “age-like” quantities generally interpreted to represent time elapsed since a fluid parcel was last at the surface. In a turbulent (“diffusive”) environment such as the ocean, we must regard the fluid parcel as being composed of material fluid elements that have spent different lengths of time since their last contact with the surface. Hence, they are characterized by an age spectrum or distribution of transit times. In this study we explore the concepts of tracer-derived “ages” and the transit-time probability density function (PDF) with the aim of improving our understanding of their interpretation. Using an ocean general circulation model, we illustrate the effect of mixing on tracer-derived “ages” within the Atlantic Ocean. The mixing biases such ages towards younger values with respect to the ideal or mean age of a water parcel. In the North Atlantic, this bias is particularly pronounced in the thermocline because of large vertical gradients in tracer concentration, and in the deep ocean, where the penetration of recently ventilated water creates large gradients along the isopycnal surfaces. In contrast, the effect of mixing appears to be relatively small in the subtropical subduction region. Calculations of the transit-time PDF in the ocean model show, however, that the mean age can potentially be very large because of contributions from long transit-time pathways, in spite of the fact that such pathways make up a small fraction of the fluid parcel. These results illustrate the key idea that tracer-derived ages are weighted towards the leading part of the transit-time distribution, while the ideal age is more sensitive to its “tail”. These tracers are thus sensitive to and help constrain different time scales. We also find that the ideal age converges much more rapidly to the mean age compared with the first moment of the age spectrum, an important consideration in numerical studies.
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  • 26
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    Pathogenicity islands: the tip of the iceberg (2001)
    Elsevier
    In:  Microbes and Infection, 3 (7). pp. 545-548.
    Details
    Publication Date: 2020-07-01
    Description: Pathogenicity islands represent distinct genetic elements encoding virulence factors of pathogenic bacteria. Pathogenicity islands belong to the class of genomic islands, which are common genetic elements sharing a set of unifying features. Genomic islands have been acquired by horizontal gene transfer. In recent years many different genomic islands have been discovered in a variety of pathogenic as well as non-pathogenic bacteria. Because they promote genetic variability, genomic islands play an important role in microbial evolution
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  • 27
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    A multiproxy reconstruction of the evolution of deep and surface waters in the subarctic Nordic seas over the last 30,000yr (2001)
    Elsevier
    In:  Quaternary Science Reviews, 20 (4). pp. 659-678.
    Details
    Publication Date: 2019-09-23
    Description: On the basis of various lithological, mircopaleontological and isotopic proxy records covering the last 30,000 calendar years (cal kyr) the paleoenvironmental evolution of the deep and surface water circulation in the subarctic Nordic seas was reconstructed for a climate interval characterized by intensive ice-sheet growth and subsequent decay on the surrounding land masses. The data reveal considerable temporal changes in the type of thermohaline circulation. Open-water convection prevailed in the early record, providing moisture for the Fennoscandian-Barents ice sheets to grow until they reached the shelf break at ∼26 cal. kyr and started to deliver high amounts of ice-rafted debris (IRD) into the ocean via melting icebergs. Low epibenthic δ18O values and small-sized subpolar foraminifera observed after 26 cal. kyr may implicate that advection of Atlantic water into the Nordic seas occurred at the subsurface until 15 cal. kyr. Although modern-like surface and deep-water conditions first developed at ∼13.5 cal. kyr, thermohaline circulation remained unstable, switching between a subsurface and surface advection of Atlantic water until 10 cal. kyr when IRD deposition and major input of meltwater ceased. During this time, two depletions in epibenthic δ13C are recognized just before and after the Younger Dryas indicating a notable reduction in convectional processes. Despite an intermittent cooling at ∼8 cal. kyr, warmest surface conditions existed in the central Nordic seas between 10 and 6 cal. kyr. However, already after 7 cal. kyr the present day situation gradually evolved, verified by a strong water mass exchange with the Arctic Ocean and an intensifying deep convection as well as surface temperature decrease in the central Nordic seas. This process led to the development of the modern distribution of water masses and associated oceanographic fronts after 5 cal. kyr and, eventually, to today's steep east–west surface temperature gradient. The time discrepancy between intensive vertical convection after 5 cal. kyr but warmest surface temperatures already between 10 and 6 cal. kyr strongly implicates that widespread postglacial surface warming in the Nordic seas was not directly linked to the rates in deep-water formation.
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  • 28
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    Symbiosis and pathogenesis: common themes, different outcomes (2001)
    Elsevier
    In:  Trends in Microbiology, 9 (12). p. 585.
    Details
    Publication Date: 2020-04-30
    Description: Refers to: Werner Goebel, Roy Gross Intracellular survival strategies of mutualistic and parasitic prokaryotes Trends in Microbiology, Volume 9, Issue 6, 1 June 2001, Pages 267-273 doi:10.1016/S0966-842X(01)02040-6
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  • 29
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    High temporal resolution field monitoring of phosphate in the River Frome using flow injection with diode array detection (2001)
    Elsevier
    In:  Analytica Chimica Acta, 440 (1). pp. 55-62.
    Details
    Publication Date: 2017-05-30
    Description: The design and deployment of an in situ flow injection (FI) monitor for high temporal resolution monitoring of phosphate in the River Frome, Dorset, UK, is described. The monitor incorporates solenoid, self-priming micropumps for propulsion, solenoid-operated switching valves for controlling the fluidics and a miniature CCD spectrometer for full spectrum (200-1000 nm) acquisition and operates in a graphical programming environment. A tangential filtration unit is attached to the sample inlet line to remove suspended particulate matter and prevent blockage of the micropumps and valves. Detection (at 7 10 nm) is based on molybdenum blue chemistry with tin(II) chloride reduction. The detection limit is 0.67 muM PO4 and the linear range can be adjusted by using different wavelengths for detection. Pump noise is eliminated by subtraction of the signal at a non-absorbing wavelength (447 nm). Data from an intensive (sample every 30 min) field trial on the River Frome performed in October 2000 are presented, and the implications of the data for refining an export coefficient model for phosphorus from the catchment are discussed.
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  • 30
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    Gas Hydrates Along the Peru and Middle America Trench Systems (2001)
    AGU (American Geophysical Union)
    In:  In: Natural Gas Hydrates: Occurence, distribution, and Detection. , ed. by Paull, C. K. and Dillon, W. P. Geophysical Monograph Series, 124 . AGU (American Geophysical Union), Washington, DC, pp. 257-271.
    Details
    Publication Date: 2019-08-06
    Type: Book chapter , NonPeerReviewed
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  • 31
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    Oxygen isotopes of marine diatoms and relations to opal-A maturation (2001)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 65 . pp. 201-211.
    Details
    Publication Date: 2017-09-26
    Description: In order to develop the potential tool of diatom oxygen isotopes for paleoenvironmental studies we compared oxygen isotopes of natural marine diatoms sampled from ocean surface water, sediment traps and surface sediments with oxygen isotopic fractionations determined for laboratory diatom cultures. Freshly grown natural diatoms (phytoplankton samples and sediment trap material) and cultured diatoms reveal similar oxygen isotope fractionation factors. The fresh diatoms have 3 to 10 parts per thousand lower isotope fractionation factors than fossil (sedimentary) diatoms. A temperature-related oxygen isotope fractionation could not be established for the laboratory cultures (and the natural phytoplankton samples), and there is evidence that diatom growth rate until reaching the stationary growth state also controls the measured silica-water oxygen isotope fractionation factor. It is possible, however, that slow diatom growth in sea surface water may well lead to a temperature-dependent silica-water oxygen isotope fractionation which is the prerequisite for a use of diatom oxygen isotopes in palco-surface water studies. FTIR-spectroscopic analyses of various diatomaceous materials revealed that the ratio of integrated peak intensities for Si-O-Si/Si-OH correlates with the 3 to 10 parts per thousand delta O-18(silica) increase from fresh to fossil diatoms. Open-system (flow-through) silica dissolution experiments suggest that the diatom frustules are isotopically homogenous and that the increase in O-18 is therefore not due to dissolution of isotopically light surficial Si-OH groups. It is concluded that slow internal condensation reactions during silica maturation in surface sediments cause both an increase in the intensity ratio of Si-O-Si/Si-OH and the O-18 content of framework oxygen. These findings also indicate that the oxygen isotope compositions of marine sediment diatoms do not indicate sea surface water temperature but rather reflect variable O-18 contents of surface sediments. Copyright (C) 2001 Elsevier Science Ltd.
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  • 32
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    Cephalopod prey of king pengiuns (Aptenodytes patagonicus) breeding at Volunteer Beach, Falkland Islands, during austral winter 1996 (2001)
    Elsevier
    In:  Fisheries Research, 52 . pp. 79-90.
    Details
    Publication Date: 2021-06-25
    Description: The beaks of 10 cephalopod species were found in the diet of foraging and moulting king penguins (Aptenodytes patagonicus) from a breeding colony at Volunteer Beach, Falkland Islands during austral winter (September/October 1996). A total of 486 lower cephalopod beaks were collected, identified and measured (LRL: lower rostral length). Six cephalopod families occurred in the penguins’ diet with Onychoteuthidae being the most abundant (256 lower beaks) and represented by Moroteuthis ingens (168; LRL range 2.1–6.8 mm), Moroteuthis knipovitchi (79; LRL range 1.9–5.5 mm), and Kondakovia longimana (9; LRL range 2.1–7.4 mm). Other families were Ommastrephidae (135) with Martialia hyadesi (127; LRL range 2.6–8.7 mm), Illex argentinus (6; LRL range 5.0–6.0 mm), and Ommastrephes bartrami (2; LRL range 7.9–8.8 mm); Loliginidae with Loligo gahi (60; LRL range 0.8–2.1 mm); Gonatidae with Gonatus antarcticus (28; LRL range 1.3–3.3 mm); Neoteuthidae with Alluroteuthis antarcticus (4; LRL range 2.4–3.9 mm), and Histioteuthidae with Histioteuthis eltaninae (3; LRL range 3.3–3.4 mm). Allometric equations were used to relate lower rostral beak length with cephalopod body size and mass. M. ingens was the dominating cephalopod prey in terms of numbers (n=168), whereas M. hyadesi was most important in terms of biomass (64 682 g). The present study provides first information on the cephalopod prey of Falkland Islands king penguins. The data suggest that penguins take squid at coastal islands slope regions as well as in oceanic waters which demonstrates their ability to forage in a wide geographical area and to alternate between specific foraging sites. Possible competition with the commercial squid fishery off the Falkland Islands is discussed.
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  • 33
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    Late Quaternary changes of western equatorial Atlantic surface circulation and Amazon lowland climate recorded in Ceará Rise deep sea sediments (2001)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 16 . pp. 293-305.
    Details
    Publication Date: 2017-01-18
    Description: Today the western tropical Atlantic is the most important passage for cross-equatorial transfer of heat in the form of warm surface water flowing from the South into the North Atlantic. Circulation changes north of South America may thus have influenced the global thermohaline circulation system and high northern latitude climate. Here we reconstruct late Quaternary variations of western equatorial Atlantic surface circulation and Amazon lowland climate obtained from a multiproxy sediment record from Ceará Rise. Variations in the illite/smectite ratio suggest drier climatic conditions in the Amazon Basin during glacials relative to interglacials. The 230Thex-normalized fluxes and the 13C/12C record of organic carbon indicate that sea level fluctuations, shelf topography, and changes of the surface circulation pattern controlled variations and amplitude of terrigenous sediment supply to the Ceará Rise. We attribute variations in thermocline depth, reconstructed from vertical planktic foraminiferal oxygen isotope gradients and abundances of the phytoplankton species Florisphaera profunda, to changes in southeast trade wind intensity. Strong trade winds during ice volume maxima are associated with a deep western tropical Atlantic thermocline, strengthening of the North Brazil Current retroflection, and more vigorous eastward flow of surface waters.
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  • 34
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    The link between bottom simulating reflections and methane flux into the gas hydrate stability zone – New evidence from Lima Basin, Peru Margin (2001)
    Elsevier
    In:  Earth and Planetary Science Letters, 185 . pp. 343-354.
    Details
    Publication Date: 2016-11-15
    Description: Bottom-simulating reflections (BSRs) are probably the most commonly used indicators for gas hydrates in marine sediments. It is now widely accepted that BSRs are primarily caused by free gas beneath gas-hydrate-bearing sediments. However, our insight into BSR formation to date is mostly limited to theoretical studies. Two endmember processes have been suggested to supply free gas for BSR formation: (i) dissociation of gas hydrates and (ii) migration of methane from below. During a recent campaign of the German Research Vessel Sonne off the shore of Peru, we detected BSRs at locations undergoing both tectonic subsidence and non-sedimentation or seafloor erosion. Tectonic subsidence (and additionally perhaps seafloor erosion) causes the base of gas hydrate stability to migrate downward with respect to gas-hydrate-bearing sediments. This process rules out dissociation of gas hydrates as a source of free gas for BSRs at these locations. Instead, free gas at BSRs is predicted to be absorbed into the gas hydrate stability zone. BSRs appear to be confined to locations where the subsurface structure suggests focusing of fluid flow. We investigated the seafloor at one of these locations with a TV sled and observed fields of rounded boulders and slab-like rocks, which we interpreted as authigenic carbonates. Authigenic carbonates are precipitations typically found at cold vents with methane expulsion. We retrieved a small carbonate-cemented sediment sample from the seafloor above a BSR about 20 km away. This supported our interpretation that the observed slabs and boulders were carbonates. All these observations suggest that BSRs in Lima Basin are maintained predominantly by gas that is supplied from below, demonstrating that this endmember process for BSR formation exists in nature. Results from Ocean Drilling Program Leg 112 showed that methane for gas hydrate formation on the Peru lower slope and the methane in hydrocarbon gases on the upper slope is mostly of biogenic origin. The δ13C composition of the recovered carbonate cement was consistent with biologic methane production below the seafloor (although possibly above the BSR). We speculate that the gas for BSR formation in Lima Basin also is mainly biogenic methane. This would suggest the biologic productivity beneath the gas hydrate zone in Lima Basin to be relatively high in order to supply enough methane to maintain BSRs.
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  • 35
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    Sea ice transports in the Weddell Sea (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 106 (C5). pp. 9057-9073.
    Details
    Publication Date: 2019-09-23
    Description: Time series of sea ice draft in the Weddell Sea are evaluated together with hydrographic observations, satellite passive microwave data, and ice drift for estimation of the freshwater fluxes into and out of the Weddell Sea. Ice draft is measured with moored upward looking sonars since 1990 along two transects across the Weddell Gyre. One transect, extending from the tip of the Antarctic Peninsula to Kapp Norvegia, was sampled between 1990 and 1994 and covers the flow into and out of the southern Weddell Sea. The other transect, sampled since 1996 and extending from the Antarctic continent northward along the Greenwich meridian, covers the exchange of water masses between the eastern and the western Weddell Sea. In order to relate results obtained during the different time periods, empirical relationships are established between the length of the sea ice season, derived from the satellite passive microwave data and defined as the number of days per year with the sea ice concentration exceeding 15%, and (1) the annual mean ice draft and (2) the annual mean ice volume transport. By using these empirical relationships, estimates of annual mean ice drafts and ice volume transports are derived at all mooring sites for the period February 1979 through February 1999. Wind and current force a westward ice transport in the coastal areas of the eastern Weddell Sea and a northward ice transport in the west. During the 2-year period 1991/1992 the mean ice volume export from the Weddell Sea is (50 ± 19) × 103 m3 s−1. This freshwater export is representative for a longer-term (20-year) mean and exceeds the average amount of freshwater gained by precipitation and ice shelf melt by about 19×103 m3 s−1, yielding an upper bound for the formation rate of newly ventilated bottom water in the Weddell Sea of 2.6 Sv.
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  • 36
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    The Hf isotope composition of global seawater and the evolution of Hf isotopes in the deep Pacific Ocean from Fe-Mn crusts (2001)
    Elsevier
    In:  Chemical Geology, 178 . pp. 23-42.
    Details
    Publication Date: 2017-12-06
    Description: This paper presents a revised chemical purification method of Hf for the measurement of Hf isotope ratios of Fe–Mn crusts on a new generation of double focusing multiple collector plasma source mass spectrometer (MC-ICP-MS). By measuring surface scrapings of hydrogenetic Fe–Mn crusts distributed over the three major ocean basins, the present-day Hf isotope distribution of oceanic deep water is assessed in detail. The results show an εHf provinciality correlated with those of other radiogenic isotope tracers such as Nd and Pb in agreement with previous studies. This supports the use of Hf isotopes as tracer of element source provenance and water masses. Fe–Mn crusts display the same present-day Hf–Nd isotope array as given before for Mn nodules. The smaller isotopic variability of Hf compared with Nd may either be caused by a more efficient mixing of Hf than Nd in the ocean due to a longer residence time or may be a consequence of a systematically more radiogenic Hf than Nd isotope signature delivered to the oceans by weathering of continental crust. A Hf isotope time series was measured on crust VA13/2 to assess the Hf isotope compositions of the Central Pacific deep water over the past 26 Ma. No consistency is observed between the Hf and Pb isotope time series. In contrast, Hf and Nd isotope time series display similar patterns which are, however, apparently offset by 2 Ma prior to 14 Ma. Differential diffusion of Hf and Nd does not explain this offset. The smaller amplitude in the Hf isotope variations compared with the Nd isotopes rather argues for more efficient mixing of Hf in the ocean. We suggest that both isotope systems have responded in a similar way to the processes affecting the dissolved radiogenic isotope composition of Pacific deep water during this time interval. The parallel increase in εHf and εNd observed between 14 and 3 Ma may probably be attributed to the increased inputs of Hf and Nd into the Central Pacific Ocean derived from the weathering of the Pacific Islands Arcs. Over the past 3 Ma an increased aeolian continental input derived from Asia most likely caused negative shifts in εNd and εHf recorded by VA13/2. The fact that Hf and Nd isotope compositions plot along the present-day array for Fe–Mn crusts and Mn nodules over the entire past 26 Ma suggests that aeolian supply of Hf to the Pacific Ocean has been a long-term important feature.
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  • 37
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    Intensive ship-board observations of the flow through the Strait of Gibraltar (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 106 (C12). 31,017-31,032.
    Details
    Publication Date: 2018-04-18
    Description: During the European project Canary Island Azores Gibraltar Experiment (CANIGO), intensive shipboard observations were carried out in April 1996 and October 1997 in order to observe the spatial and temporal variability of the flow and of the water mass structure in the Strait of Gibraltar. At the sill and the eastern and western entrances to the strait, repeated cross-strait sections and station time series of the flow and of T–S profiles were measured using vessel-mounted and lowered acoustic Doppler current profilers (ADCP) and conductivity-temperature-depth probes (CTD)/expendable bathythermographs (XBT), yielding new views of the rapid changes over tidal cycles and of approximate tidal means. It is argued that transport observations might be easier to carry out away from the sill, in the eastern part of the strait, even though maximum resolved shears were comparable in both places, 0.03–0.04 s−1 in the vertical and 0.001–0.016 s−1 in the horizontal. In the east, coordinated changes in the stratification and the flow field are documented via four time series over M 2 tidal cycles, showing a sharpening/diffusing of the vertical gradients in the water masses and the flow. Maximum shear and maximum water mass gradients do not always coincide there, and both are much shallower (50–80 m) than the delimiter between inflow and outflow (120–150 m). The mean salinity of the outflow core decreases from 38.43 in the east to 38.17 west of the sills as a result of the mixing processes. The internal bore was followed and directly observed with rapid CTD-yoyo stations and with XBT/vessel-mounted ADCP measurements. It generates extreme changes in currents and shears on timescales of minutes, with directly measured vertical velocities reaching ±50 cm s−1. Patches of density inversions were observed as the bore passed by, consistent with active turbulent mixing along the interface. The time series of flow and CTD measurements allow the direct calculation of Froude numbers at various locations and over tidal cycles. These and along-strait sections suggest that the exchange through the strait is maximal in April 1996 and submaximal in October 1997, supporting the expectations of Garrett et al. [1990].
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  • 38
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    Flow of bottom water in the northwestern Weddell Sea (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 106 . pp. 2761-2778.
    Details
    Publication Date: 2019-09-23
    Description: The Weddell Sea is known to feed recently formed deep and bottom water into the Antarctic circumpolar water belt, from whence it spreads into the basins of the world ocean. The rates are still a matter of debate. To quantify the flow of bottom water in the northwestern Weddell Sea data obtained during five cruises with R/V Polarstern between October 1989 and May 1998 were used. During the cruises in the Weddell Sea, five hydrographic surveys were carried out to measure water mass properties, and moored instruments were deployed over a time period of 8.5 years to obtain quasi-continuous time series. The average flow in the bottom water plume in the northwestern Weddell Sea deduced from the combined conductivity-temperature-depth and moored observations is 1.3±0.4 Sv. Intensive fluctuations of a wide range of timescales including annual and interannual variations are superimposed. The variations are partly induced by fluctuations in the formation rates and partly by current velocity fluctuations related to the large-scale circulation. Taking into account entrainment of modified Warm Deep Water and Weddell Sea Deep Water during the descent of the plume along the slope, between 0.5 Sv and 1.3 Sv of surface-ventilated water is supplied to the deep sea. This is significantly less than the widely accepted ventilation rates of the deep sea. If there are no other significant sources of newly ventilated water in the Weddell Sea, either the dominant role of Weddell Sea Bottom Water in the Southern Ocean or the global ventilation rates have to be reconsidered.
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  • 39
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    Mitochondrial phylogeny and biogeographic affinities of sea breams of the genus Diplodus (Sparidae) (2001)
    Wiley-Blackwell
    In:  Journal of Fish Biology, 59 . pp. 1638-1652.
    Details
    Publication Date: 2017-09-08
    Description: Phylogenetic analyses, using 482 bp of the mitochondrial 16S rDNA and 461 bp of the control region of 16 Diplodus species and Oblada melanura, Pagellus bogaraveo and Pagellus acarne, all close relatives of Diplodus, identified the two representatives of Pagellus as the sister group of Diplodus. Oblada melanura was confirmed as the sister taxon of D. puntazzo, despite its different dental morphology and ecology. Within the genus Diplodus, three clades were identified, the first containing D. annularis and D. bellottii, the second D. vulgaris and D. prayensis, and the third comprising three subclades. These were formed by O. melanura clustering with D. puntazzo, D. fasciatus with D. cervinus, and by the Diplodus sargus sub-species assemblage which also included the West Atlantic taxa D. argenteus, D. bermudensis, D. holbrooki, and the Red Sea endemic D. noct. All members of the D. sargus assemblage were genetically closely related. Among them, D. sargus lineatus from the Cape Verde islands was resolved as most ancestral branch, pointing to the possibility that the diversification and spread of the D. sargus assemblage originated in this region. The hypothesis of stepwise speciation following colonization events within the D. sargus complex is fully supported by phylogenetic reconstruction.
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  • 40
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    Mesoscale subduction at the Almeria–Oran front - Part 2. Biophysical interactions (2001)
    Elsevier
    In:  Journal of Marine Systems, 30 (3-4). pp. 287-304.
    Details
    Publication Date: 2017-07-12
    Description: The Almeria–Oranfront forms where surface waters of Atlantic and Mediterranean origin meet at the eastern end of the Alboran Sea. A multidisciplinary field experiment on RRS Discovery in December 1996, in the second observational phase of the EU-funded Observations and Modelling of Eddy scale Geostrophic and Ageostrophic motions (OMEGA) project, observed the biological impact of mesoscale frontal instability of the Almeria–Oran frontal jet. It is concluded that periodic vertical velocities of ∼20 m/day, associated with the propagation of wave-like meanders along the front, have a significant effect on the vertical distribution of zooplankton across the front despite their ability to migrate at greater speeds. Observations of a layer of fluorescence coincident with subducted surface waters indicated that phytoplankton were drawn down and along isopycnals, by cross-front ageostrophic motion, to depths of 200 m. From the study of sound-scattering layers (SSL) identified in acoustic backscatter data, a layer of zooplankton was found coincident with the drawn-down phytoplankton. This layer persisted during and despite diel vertical migration. High-resolution optical plankton counter (OPC) data showed smaller zooplankton, which did not undertake diel vertical migration, remained concentrated near the surface in the fast-flowing frontal jet.
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  • 41
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    Mean transport and seasonal cycle of the Kuroshio east of Taiwan with comparison to the Florida Current (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 106 (C10). pp. 22143-22158.
    Details
    Publication Date: 2017-11-24
    Description: Moored observations of Kuroshio current structure and transport variability were made across the channel between northeast Taiwan and the Ryukyu Islands at 24 degreesN from September 19, 1994, to May 27, 1996. This was a cooperative, effort between the United States and Taiwan. The moored array was designated PCM-1, for the World Ocean Circulation Experiment (WOCE) transport resolving array. The dominant current and transport variability occurred on 100-day timescales and is shown by Zhang et al. [2001] to be caused by warm mesoscale eddys merging with the Kuroshio south of the array causing offshore meandering and flow splitting around the Ryukyu Islands. An annual transport cycle could not be resolved from our 20-month moored record because of abasing from the 100-day period events. Sea level difference data were used to extend the transport time series to 7 years giving a variation in the range of the annual transport cycle of 4-10 Sv, with a mean range closer to 4 Sv. The seasonal maximum of 24 Sv occurred in the summer and the seasonal minimum of 20 Sv occurred in the fall. A weaker secondary maximum also occurred in the winter. The cycle of Kuroshio transport appears to result from a combination of local along-channel wind forcing and Sverdrup forcing over the Philippine Sea. Our estimate of the mean transport of the Kuroshio at the entrance to the East China Sea from the moored array is 21.5 +/- 2.5 Sv. The mean transpacific balance of meridional flows forced by winds and thermohaline processes at this latitude requires an additional mean northward flow of 12 Sv with an annual cycle of +/-8 Sv along the eastern boundary of the Ryukyu Islands. The mean transport and annual cycle of the Kuroshio were found to be in reasonable agreement with basin-scale wind-forced models. Remarkable similarities are shown to exist between the mean western boundary currents and their seasonal cycles in the Atlantic (Florida Current and Antilles Current) and Pacific (Kuroshio and boundary current east of Ryukyu Island chain) at the same latitude. However, detailed comparison shows that the mean Kuroshio is weaker and more surface intensified than the mean Florida Current, while the Kuroshio-transport variability is significantly larger.
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  • 42
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    Qualité biologique de l’eau de mer évaluée in situ par le test embryo-larvaire de Crassostrea gigas et Mytilus galloprovincialis = In situ monitoring of sea water quality with the embryo-larval bioassay of Crassostrea gigas and Mytilus galloprovincialis (2001)
    Elsevier
    In:  Comptes Rendus de l Academie des Sciences - Series III - Sciences de la Vie, 324 . pp. 1149-1155.
    Details
    Publication Date: 2017-12-11
    Description: Embryos and larvae of bivalves are frequently used in marine ecotoxicology for the purpose of assessing seawater quality, because they are very sensitive to pollutants and provide rapid responses. Laboratory studies, however, cannot accurately simulate natural conditions. We conducted bivalve embryo-larval studies in situ at the marina of Arcachon (southwest French Atlantic coast), in order to assess ‘biological quality’ of the water. One experiment conducted in winter 1999 (temperatures of 10 °C) with embryos of the Mediterranean mussel, Mytilus galloprovincialis, has shown that such tests are practicable in winter at low temperatures. This study did not show any deterioration in ‘biological quality’ of the water. Four series of experiments were subsequently performed during summer 2000 (ambient water temperatures of 19 to 22.4 °C) with embryos of the Japanese oyster, Crassostrea gigas. The results show that the ‘sea water biological quality’ deteriorates from the port entrance towards its inner part. To our knowledge, this is the first investigation of the marine environment in which bivalve embryos have been used in situ. They are very suitable for this type of study, because bivalve embryos and larvae are more sensitive to pollutants than the adults, and also because they belong to euryhaline species and the embryos tolerate summer temperatures (both species) as well as winter temperatures (mussels), allowing biomonitoring to be conducted all over the year.
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  • 43
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    Formation of a basin-scale surface chlorophyll pattern by Rossby waves (2001)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 28 . pp. 4139-4142.
    Details
    Publication Date: 2018-02-14
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  • 44
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    The behaviour of dissolved Cd, Co, Zn, and Pb in North Atlantic near-surface waters (30°N/60°W-60°N/2°W) (2001)
    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 48 (12). pp. 2541-2567.
    Details
    Publication Date: 2020-08-05
    Description: In September 1993 (M26) and June/July 1996 (M36), a total of 239 surface samples (7 m depth) were collected on two transects across the open Atlantic Ocean (224 samples) and northwest European shelf edge area. We present an overview of the horizontal variability of dissolved Cd, Co, Zn, and Pb in between the northwest and northeast Atlantic Ocean in relation to salinity and the nutrients. Our data show a preferential incorporation of Cd relative to P in the particulate material of the surface ocean when related to previously published parallel measurements on suspended particulate matter from the same cruise. There is a good agreement with results recently estimated from a model by Elderfield and Rickaby (Nature 405 (2000) 305), who predict for the North Atlantic Ocean a best fit for αCd/P=[Cd/P]POM/[Cd/P]SW of 2.5, whereas the approach of our transect shows a αCd/P value of 2.6. The Co concentrations of our transects varied from 〈5 to 131 pmol kg−1, with the lowest values in the subtropical gyre. There were pronounced elevations in the low-salinity ranges of the northwest Atlantic and towards the European shelf. The Co data are decoupled from the Mn distribution and support the hypothesis of marginal inputs as the dominant source. Zinc varied from a minimum of 〈0.07 nmol kg−1 to a maximum of 1.2 and 4.8 nmol kg−1 in regions influenced by Labrador shelf or European coastal waters, respectively. In subtropical and northeast Atlantic waters, the average Zn concentration was 0.16 nmol kg−1. Zinc concentrations at nearly three quarters of the stations between 40°N and 60°N were 〈0.1 nmol kg−1. This suggests that biological factors control Zn concentrations in large areas of the North Atlantic surface waters. The Pb data indicated that significant differences in concentration between the northwest and northeast Atlantic surface waters presently (1996) do not exist for this metal. The transects in 1993 and 1996 exhibited Pb concentrations in the northeast Atlantic surface waters of 30 to 40 pmol kg−1, about a fifth to a quarter of the concentrations observed in 1981. This decline is supported by our particle flux measurements in deep waters of the same region.
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  • 45
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    A Comparison of Precipitation In-Situ Measurements and Model Predictions over the Baltic Sea Area (2001)
    Elsevier
    In:  Physics and Chemistry of The Earth Part B-Hydrology Oceans and Atmosphere, 26 (5-6). pp. 437-442.
    Details
    Publication Date: 2017-01-02
    Description: Precipitation plays an important role in the hydrological cycle. But to date, nearly no in-situ precipitation measurements are available over the Baltic Sea. This paper presents first results of rain measurements made by the Institut für Meereskunde at the University of Kiel over a period of two years (1997–1998). A simple interpolation method using autocorrelation functions was used to get a first insight of the spatial distribution in precipitation over the Baltic Proper.
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  • 46
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    L'ouverture océanique au sud de la Tasmanie durant le Paléogène et ses conséquences paléocéanographiques : résultats préliminaires de la minéralogie des argiles (leg ODP 189) = Palaeogene ocean opening south of Tasmania, and palaeoceanographic implications: preliminary results of clay mineral analyses (ODP Leg 189) (2001)
    Elsevier
    In:  Comptes Rendus de l'Académie des Sciences - Series IIA - Earth and Planetary Science, 332 (5). pp. 323-329.
    Details
    Publication Date: 2017-12-11
    Description: ODP Leg 189 was designed to test the hypothesis that opening of the Tasmanian Seaway and initiation of circumpolar circulation contributed to the thermal isolation of Antarctica, leading to the development of initial ice-sheet and oceanic thermohaline circulation. The clay assemblages of the Tasmanian region contain the traces of two tectonic stages associated with ocean opening south of the south Tasman Rise near the Palaeocene–Eocene boundary and strike-slip activity between the western Tasmanian land-bridge and Antarctica during the Late Eocene. Earliest Oligocene clays indicate that cooling of Antarctic margins and activity of western boundary circulation progressed with the regional subsidence.
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  • 47
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    Retention of dissolved iron and FeII in an iron induced Southern Ocean phytoplankton bloom. (2001)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 28 (18).
    Details
    Publication Date: 2018-02-19
    Description: During the 13 day Southern Ocean Iron RE-lease Experiment (SOIREE), dissolved iron concentrations decreased rapidly following each of three iron-enrichments, but remained high (〉1 nM, up to 80% as FeII) after the fourth and final enrichment on day 8. The former trend was mainly due to dilution (spreading of iron-fertilized waters) and particle scavenging. The latter may only be explained by a joint production-maintenance mechanism; photoreduction is the only candidate process able to produce sufficiently high FeII, but as such levels persisted overnight (8 hr dark period) —ten times the half—life for this species—a maintenance mechanism (complexation of FeII) is required, and is supported by evidence of increased ligand concentrations on day 12. The source of these ligands and their affinity for FeII is not known. This retention of iron probably permitted the longevity of this bloom raising fundamental questions about iron cycling in HNLC (High Nitrate Low Chlorophyll) Polar waters.
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  • 48
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    Cooling and ventilating the abyssal ocean (2001)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 28 . pp. 2923-2926.
    Details
    Publication Date: 2018-02-14
    Description: The abyssal ocean is filled with cold, dense waters that sink along the Antarctic continental slope and overflow sills that lie south of the Nordic Seas. Recent integrations of chlorofluorocarbon‐11 (CFC) measurements are similar in Antarctic Bottom Water (AABW) and in lower North Atlantic Deep Water (NADW), but Antarctic inputs are ≈ 2°C colder than their northern counterparts. This indicates comparable ventilation rates from both polar regions, and accounts for the Southern Ocean dominance over abyssal cooling. The decadal CFC‐based estimates of recent ventilation are consistent with other hydrographic observations and with longer‐term radiocarbon data, but not with hypotheses of a 20th‐century slowdown in the rate of AABW formation. Significant variability is not precluded by the available ocean measurements, however, and interannual to decadal changes are increasingly evident at high latitudes.
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  • 49
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    Seasonal cycle of meridional heat transport in the subtropical North Atlantic: a model intercomparison in relation to observations near 25°N (2001)
    Elsevier
    In:  Progress in Oceanography, 48 (2-3). pp. 231-254.
    Details
    Publication Date: 2016-10-07
    Description: Three different, eddy-permitting numerical models are used to examine the seasonal variation of meridional mass and heat flux in the North Atlantic, with a focus on the transport mechanisms in the subtropics relating to observational studies near 25°N. The models, developed in the DYNAMO project, cover the same horizontal domain, with a locally isotropic grid of 1/3° resolution in longitude, and are subject to the same monthly-mean atmospheric forcing based on a three-year ECMWF climatology. The models differ in the vertical-coordinate scheme (geopotential, isopycnic, and sigma), implying differences in lateral and diapycnic mixing concepts, and implementation of bottom topography. As shown in the companion paper of Willebrand et al. (2001), the model solutions exhibit significant discrepancies in the annual-mean patterns of meridional mass and heat transport, as well as in the structure of the western boundary current system. Despite these differences in the mean properties, the seasonal anomalies of the meridional fluxes are in remarkable agreement, demonstrating a robust model behavior that is primarily dependent on the external forcing, and independent of choices of numerics and parameterization. The annual range is smaller than in previous model studies in which wind stress climatologies based on marine observations were used, both in the equatorial Atlantic (1.4 PW) and in the subtropics (0.4–0.5 PW). This is a consequence of a weaker seasonal variation in the zonal wind stresses based on the ECMWF analysis than those derived from climatologies of marine observations. The similarities in the amplitude and patterns of the meridional transport anomalies betwen the different model realizations provide support for previous model conclusions concerning the mechanism of seasonal and intraseasonal heat flux variations: they can be rationalized in terms of a time-varying Ekman transport and their predominantly barotropic compensation at depth. Analysis for 25°N indicates that the net meridional flow variation at depth is concentrated near the western boundary, but cannot be inferred from transport measurements in the western boundary current system, because of significant and complex recirculations over the western half of the basin. The model results instead suggest that the main requirement for estimating the annual cycle of heat flux through a transoceanic section, and the major source of error in model simulations, is an accurate knowledge of the wind stress variation.
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  • 50
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    On the accuracy of the independent column approximation in calculating the downward fluxes in the UVA, UVB and PAR spectral ranges (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Atmospheres, 106 (D13). pp. 14301-14312.
    Details
    Publication Date: 2019-07-31
    Description: In order to investigate the accuracy of simplification in modeling the radiative transfer in those solar spectral regions with major impacts on bio-organisms, i.e., the UVA (0.32–0.4 μm), the UVB (0.28–0.32 μm), and the photosynthetically active radiation (PAR, 0.4–0.7 μm), radiative transfer calculations with varying treatments of cloud geometries (plane-parallel homogeneous (PPHOM), independent column approximation (ICA), and three-dimensional (3-D) inhomogeneous) have been performed. The complete sets of atmospheric information for 133 cloud realizations are taken from the three-dimensional nonhydrostatic mesoscale atmospheric model (GESIMA). A Monte Carlo radiative transfer model (GRIMALDI) has been developed that simulates scattering and absorption for arbitrarily three-dimensional distributions of cloud hydrometeors, air molecules, and water vapor. Results are shown for domain-averaged direct and total transmission (and so, implicitly, diffuse transmission) at the ground surface. In the UVA the PPHOM assumption leads to an underestimation in direct (total) downward flux by as much as 43 (28) W m−2, which is about 49% (32%) of the incoming irradiation, whereas results based on the ICA are almost identical to the 3-D case, except for convective clouds where the error in the UVA for direct (total) downward flux reaches 5 (2) W m−2, or 6% (2%) of the incoming solar irradiation.
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  • 51
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    Comparative analysis of food webs based on flow networks: effects of nutrient supply on structure and function of coastal plankton communities (2001)
    Elsevier
    In:  Continental Shelf Research, 21 (18-19). pp. 2043-2053.
    Details
    Publication Date: 2016-09-21
    Description: The objective of COMWEB was to develop efficient analytical, numerical and experimental methods for assessing and predicting the effects of nutrient (N, P, Si) supply on the stability and persistence of pelagic food web structure and function in coastal waters. The experimental comparative work included a geographic gradient covering Baltic, Mediterranean, and NE Atlantic waters and a NE Atlantic gradient in state of eutrophication. COMWEB has been an experimental approach to coastal eutrophication, studying effects of enhanced nutrient supply on components and flows of the entire lower pelagic food web. Flow network representations of pelagic food webs has been a framework of data reduction and flows were established by sophisticated inverse modelling. Fundamental information on physiological properties of functional key species in the pelagic food web was used to constrain flow estimations. A main conclusion derived from the flow networks was that very little energy and materials were transferred from the microbial food web to the main food chain. The lower food web could therefore be described as two parallel food chains with relatively limited interaction between heterotrophic groups. Short-term effects of nutrient perturbations were examined in mesocosms along the geographic gradient. The response was comparable in all systems, with a stronger effect on the activity and biomass of autotrophic groups than those of heterotrophic ones. Mediterranean waters showed much lower autotrophic biomass response than Baltic and NE Atlantic waters, which responded almost equally. The response of primary production was, however, more comparable. High phytoplankton lysis rate explained this low accumulation of biomass in Mediterranean waters. The study of Atlantic coastal waters of different eutrophic states revealed that the ecological response was higher in the closed nutrient perturbed mesocosms than in open systems exposed for 〉4 summer months (summer/autumn season). The Atlantic lagoon evolved gradually from the natural oligotrophic situation towards the more eutrophicated North Sea during fertilisation. The responses observed on seasonal and long-term scale (〉10 years) may therefore be equal. The differences between short-term (weeks) and intermediate-term (seasonal) responses is most likely a result of the different time scales of perturbation and observation and the variable exchange rates with surrounding waters (water dilution rate). The analysis of pelagic flow networks provided a framework of diagnostic criteria for state and quality assessment of coastal waters. The nutrient loading rates related better to estimates of biotic fluxes than to concentrations of biotic compartments and total nutrients. On the contrary, the concentration of biotic compartments, or the biomasses, related better to total nutrient concentrations. Primary production, mesozooplankton grazing and growth, fraction of primary production consumed by grazers, bacterial production relative to primary production, cycling indices, and path lengths were all well related to nutrient loading rate. Autotrophic biomass, ratio of autotrophic to heterotrophic biomass, and fraction of pico-cyanobacteria of total autotrophic biomass were all related to total nutrients. Some of these variables, which responded equally in all systems, have the potential of becoming unified response functions in a management model for European coastal waters. COMWEB has provided further insight into the mechanisms behind coastal eutrophication. A main achievement is the conceptual framework for unified response functions, important components of management models for nutrient emission to coastal waters.
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  • 52
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    Methane and pCO2 in the Kuroshio and the South China Sea during maximum summer surface temperatures (2001)
    Elsevier
    In:  Marine Chemistry, 75 . pp. 89-108.
    Details
    Publication Date: 2017-08-22
    Description: The methane concentration and pCO2 in surface waters and the overlying marine air were continuously surveyed along the pathway of the Kuroshio, from the eastern coast of Honshu to Taiwan, and then across the eastern part of the East China and South China Seas in September of 1994. Off Honshu, the CH4 content was controlled by the confluence of the relatively CH4-poor waters of the Kuroshio and the Oyashio and the CH4-rich Tsugaru Warm Current, the latter carrying water into the Pacific Ocean with a methane content more than twice the equilibrium value with the atmospheric CH4 partial pressure. Along the Kuroshio, the surface water was supersaturated in methane with respect to the atmosphere by 10–15% and appears considerably enriched relative to open Pacific surface waters at same latitudes. The northeastern part of the South China Sea, part of the deep basin of this marginal sea, showed CH4 concentrations similar to those found in open-ocean waters. In contrast, highly variable oversaturations up to 700% were observed along the northwestern coast of Borneo, most probably related to known seepage from oil and gas deposits in this area. The pCO2 of surface water was higher than the atmospheric pCO2 throughout the area surveyed. However, the ΔpCO2 of the surface waters varied from close to 0 to more than 60 μatm. The observed oversaturation in areas influenced by the Kuroshio confirm that, during a short period in late summer, the surface waters of this current between Taiwan and Japan act as a moderate source for atmospheric CO2.
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  • 53
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    Taxon-specific growth and selective microzooplankton grazing of phytoplankton in the Northeast Atlantic (2001)
    Elsevier
    In:  Journal of Marine Systems, 30 . pp. 241-261.
    Details
    Publication Date: 2017-07-12
    Description: Taxon-specific microzooplankton dynamics were studied along a transect through the North Atlantic Drift from 70°N 04°E to 40°N 20°W during July 1997 using serial dilution and nutrient-enrichment experiments. Nutrient concentrations and microzooplankton composition indicated postbloom conditions at 40°N, 47°N, and 50°N, a transitional system at 54°N, and bloom conditions at 62°N and 70°N. The ratio of microzooplankton to phytoplankton biomass was inversely related to nitrate and phosphate concentrations. Potential grazing thresholds were observed in four of nine experiments at 40–66% of the initial phytoplankton concentration. Grazing losses were determined for six pigment-specific classes of phytoplankton. Selective grazing losses of phytoplankton taxa ranged from 73% to 248% of the nonselective grazing losses predicted according to their biomass contributions. The grazing selectivity varied considerably between communities, with the microherbivores showing positive selection for cyanobacteria and dinoflagellates and predominantly avoidance of chlorophyta and bacillariophyceae. Microzooplankton did not show a preference for the dominant phytoplankton taxa, but grazed preferentially on fast-growing phytoplankton with minor contributions (〈15%) to the phytoplankton biomass. However, bacillariophyceae were the major contributors to phytoplankton biomass and accounted for major fractions of the total losses through microzooplankton grazing. Microzooplankton consumed the equivalent of 0.12–5.5 times their own biomass daily on a carbon basis, amounting to 65–197% of gross phytoplankton production. With the conservative assumption that 20% of the consumed phytoplankton was converted to microzooplankton biomass, the latter was estimated to contribute 27–381% to the net production of the entire microzooplankton community. We therefore conclude that the taxonomic structure and the net production of the microzooplankton communities were significantly affected by the intensity and selectivity of herbivorous microzooplankton grazing.
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  • 54
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    Hot vents in an ice-cold ocean: Indications for phase separation at the southernmost area of hydrothermal activity, Bransfield Strait, Antarctica (2001)
    Elsevier
    In:  Earth and Planetary Science Letters, 193 (3-4). pp. 381-394.
    Details
    Publication Date: 2016-11-15
    Description: During the expeditions ANT-XV/2 with R/V Polarstern in 1997/98 and NBP 99-04 with R/V IB N.B. Palmer in 1999, the first samples of hydrothermally influenced sediments of Bransfield Strait were obtained at Hook Ridge, a volcanic edifice in the Central Basin of the Strait. The vent sites are characterized by white siliceous crusts on top of the sediment layer and temperatures measured immediately on deck are up to 48.5°C. The shallow depth of these vent sites (1050 m) particularly controls the chemistry of the pore fluids that are enriched in silica and sulfide and show low pH values. Chloride is depleted up to 20% and the calculated hydrothermal endmember concentration is in the range of 1–84 mM. Since other mechanisms for Cl depletion can be ruled out clearly, the composition of this fluid is attributed to phase separation. While the Cl-depleted fluid is emanating at Hook Ridge, a Cl-enriched fluid can be identified in the adjacent King George Basin. Using a p,x diagram the two corresponding endmember concentrations reveal that the phase separation takes place at subcritical conditions (total depth: ∼2500 m), probably along the whole volcanic edifice
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  • 55
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    On the role of the Azores Current in the ventilation of the North Atlantic Ocean (2001)
    Elsevier
    In:  Progress in Oceanography, 48 (2-3). pp. 163-194.
    Details
    Publication Date: 2016-10-07
    Description: Three high-resolution ocean circulation models of the North Atlantic, differing chiefly in their description of the vertical coordinate, are used to examine the ventilation of the North Atlantic subtropical gyre. All the models produce mode waters of realistic densities in the Sargasso Sea and the European Basin, but have Azores Currents of differing strengths, which are categorised as strong (of realistic transport), intermediate, and weak. These differences have a critical impact upon the ventilation of the gyre. Most importantly, the strong Azores Current forms an effective barrier to the southward ventilation of Eastern North Atlantic Water from the northern European Basin, initially driving it southwestwards into the central gyre, before turning it back eastwards again in a general cyclonic circulation north of the Current. The intermediate and weak Azores Currents instead allow the southward ventilation of this water mass near the European and African coasts. The situation in Nature appears to be intermediate between these two cases, with the Azores Current acting as a partial block. The study also raises the possibility of the Azores Current forming an advective connection between the Sargasso Sea Mode Waters in the western basin and modes of similar densities found in the eastern basin on the southern side of the Current. Although there are high levels of variability in the extent of these lighter modes in the eastern basin in Nature, this postulate is supported by a number of observational studies. In addition, the present study also provides some support for the local production of Madeira Mode Water in the eastern basin, associated with retroflecting current branches on the southern side of the Azores Current. Overall, the Azores Current is, therefore, likely to have a critical impact upon the ventilation of the subtropical gyre over a large area, rather than just locally, affecting the potential vorticity and density structure of the upper ocean between subtropical latitudes and the northern European Basin. The study also contributes to an ongoing community effort to assess the realism of our current generation of ocean models.
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  • 56
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    Organic carbon flux and remineralization in surface sediments from the northern North Atlantic derived from pore-water oxygen microprofiles (2001)
    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 48 (2). pp. 529-553.
    Details
    Publication Date: 2017-06-29
    Description: Organic carbon fluxes through the sediment/water interface in the high-latitude North Atlantic were calculated from oxygen microprofiles. A wire-operated in situ oxygen bottom profiler was deployed, and oxygen profiles were also measured onboard (ex situ). Diffusive oxygen fluxes, obtained by fitting exponential functions to the oxygen profiles, were translated into organic carbon fluxes and organic carbon degradation rates. The mean Corg input to the abyssal plain sediments of the Norwegian and Greenland Seas was found to be 1.9 mg C m−2 d−1. Typical values at the seasonally ice-covered East Greenland continental margin are between 1.3 and 10.9 mg C m−2 d−1 (mean 3.7 mg C m−2 d−1), whereas fluxes on the East Greenland shelf are considerably higher, 9.1–22.5 mg C m−2 d−1. On the Norwegian continental slope Corg fluxes of 3.3–13.9 mg C m−2 d−1 (mean 6.5 mg C m−2 d−1) were found. Fluxes are considerably higher here compared to stations on the East Greenland slope at similar water depths. By repeated occupation of three sites off southern Norway in 1997 the temporal variability of diffusive O2 fluxes was found to be quite low. The seasonal signal of primary and export production from the upper water column appears to be strongly damped at the seafloor. Degradation rates of 0.004–1.1 mg C cm−3 a−1 at the sediment surface were calculated from the oxygen profiles. First-order degradation constants, obtained from Corg degradation rates and sediment organic carbon content, are in the range 0.03–0.6 a−1. Thus, the corresponding mean lifetime of organic carbon lies between 1.7 and 33.2 years, which also suggests that seasonal variations in Corg flux are small. The data presented here characterize the Norwegian and Greenland Seas as oligotrophic and relatively low organic carbon deep-sea environments.
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    On the seasonal variability and eddies in the North Brazil Current: insights from model intercomparison experiments (2001)
    Elsevier
    In:  Progress in Oceanography, 48 (2-3). pp. 195-230.
    Details
    Publication Date: 2016-10-07
    Description: The time dependent circulation of the North Brazil Current is studied with three numerical ocean circulation models, which differ by the vertical coordinate used to formulate the primitive equations. The models are driven with the same surface boundary conditions and their horizontal grid-resolution (isotropic, 1/3° at the equator) is in principle fine enough to permit the generation of mesoscale eddies. Our analysis of the mean seasonal currents concludes that the volume transport of the North Brazil Current (NBC) at the equator is principally determined by the strength of the meridional overturning, and suggests that the return path of the global thermohaline circulation is concentrated in the NBC. Models which simulate a realistic overturning at 24°N of the order of 16–18 Sv also simulate a realistic NBC transport of nearly 35 Sv comparable to estimates deduced from the most recent observations. In all models, the major part of this inflow of warm waters from the South Atlantic recirculates in the zonal equatorial current system, but the models also agree on the existence of a permanent coastal mean flow to the north-west, from the equator into the Carribean Sea, in the form of a continuous current or a succession of eddies. Important differences are found between models in their representation of the eddy field. The reasons invoked are the use of different subgrid-scale parameterisations, and differences in stability of the NBC retroflection loop because of differences in the representation of the effect of bottom friction according to the vertical coordinate that is used. Finally, even if differences noticed between models in the details of the seasonal mean circulation and water mass properties could be explained by differences in the eddy field, nonetheless the major characteristics (mean seasonal currents, volume and heat transports) appears to be at first order driven by the strength of the thermohaline circulation.
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    Variability in the Deep Western Boundary Current in the equatorial Atlantic at 44°W (2001)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 28 . pp. 1623-1626.
    Details
    Publication Date: 2018-02-14
    Description: The variability of the North Atlantic Deep Water (NADW) was studied by ten hydrographic repeat sections taken along 44 degreesW off Brazil between September 1989 and March 1994. This data set allowed for the first time to describe the seasonal signal in the Deep Western Boundary Current at the equator from hydrographic data. Annual and semiannual layer thickness modulations were observed similar to such signals in transport time series, however with a time lag of 2 months. A comparison of the interannual variability of the Labrador Sea Water component of the NADW at 44 degreesW at the equator with the formation region indicated a time lag of 13 to 17 years. The effective spreading velocities in the Labrador Sea Water are in the range 2 to 5 cms(-1) for the tropical Atlantic Ocean.
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  • 59
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    The geological water cycle and the evolution of marine δ 18O values (2001)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 65 (15). pp. 2469-2485.
    Details
    Publication Date: 2017-08-03
    Description: The turnover of water and 18O in the outer terrestrial sphere is investigated considering mantle degassing, subduction zone processes, hydrothermal circulation at spreading centers, seafloor alteration, and continental weathering processes. Mass balances indicate that the ocean currently loses water to the mantle because the water emission by mantle degassing proceeds at a significantly slower rate than the subduction of water structurally bound in the down-going slab. The current input of 18O into the ocean through hydrothermal circulation and water emissions at arc volcanoes surpasses the fixation of 18O via low-temperature water/rock interactions at the seafloor and on continents, inducing an increase in marine δ 18O values. Results of a box model simulating the Phanerozoic water and 18O cycles suggest that the mass of seawater decreased significantly causing a continuous drop in global sea-level by several hundred meters over the Phanerozoic. Model results and mass balances also allow for an enhanced estimate of current water fluxes in subduction zones consistent with the secular changes in sea-level and marine δ 18O observed in the geological record. Moreover, the model generates a secular trend for seawater δ 18O - produced by the surplus of 18O inputs and through internal feed-backs associated with isotopic exchange reactions at the seafloor - comparable to that observed in Phanerozoic carbonates. This coincidence suggests that the marine carbonates record a continuous change in isotopic composition of seawater with superimposed temperature-related fluctuations. A continuous record of near-surface temperatures was calculated using the model curve for seawater δ 18O and the corresponding carbonate data. This new climate record indicates three icehouse-greenhouse cycles with a duration of 127 My between the Cambrian and the Triassic followed by an additional cycle with extended periodicity spanning the Jurassic to Cenozoic. Simulations of the Precambrian water and 18O cycles imply that the strong 18O depletion in seawater during the early Cambrian (δ 18O around -8 ‰) was caused by enhanced weathering, diminished hydrothermal activity and extreme glaciations during the preceding late Neo- proterozoic.
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  • 60
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    Earlier history of the 〉70-Ma-old Canary hotspot based on the temporal and geochemical evolution of the Selvagen Archipelago and neighboring seamounts in the eastern North Atlantic (2001)
    Elsevier
    In:  Journal of Volcanology and Geothermal Research, 111 (1-4). pp. 55-87.
    Details
    Publication Date: 2019-09-23
    Description: Major element, trace element and Sr–Nd–Pb isotope data, combined with 40Ar/39Ar age determinations, of volcanic rocks from the Selvagen Islands and neighboring seamounts in the eastern North Atlantic reveal the earlier history of the ≥70 Ma old Canary hotspot. A basanitic to phonolitic late shield stage intrusive complex (29 Ma) is exposed on Selvagem Pequena. The evolution of Selvagem Grande can be divided into three magmatic phases: a tephritic to phonolitic late shield stage intrusive complex (24–26 Ma) and two rejuvenated or post-erosional stages (8–12 and 3.4 Ma) consisting of alkali basalt, basanite and rare phonolite. During the early to mid-Miocene volcanic hiatus (12–24 Ma), the top of the volcano was beneath sea level as evidenced by marine carbonate sediments (13–24 Ma, dated through correlation of 87Sr/86Sr with the seawater Sr isotope curve). The geochemistry of the shield stage lavas indicates that they derive from plume sources, whereas the post-erosional lavas are derived from metasomatized lithospheric sources. Five sampled seamounts to the east and northeast of the islands range in composition from alkali basalt and basanite to phonolite. Samples from Dacia, Conception Bank and Lars were dated at 9, 17 and 68 Ma, respectively. Geochemical data suggest that the dredged samples come from the post-erosional stage of volcanism, and therefore, the dates represent minimum ages for the seamount volcanoes. The elevation of erosional platforms formed at wave base decrease from Selvagen Grande (∼100 m above sea level) to Lars seamount (∼900 m below sea level), suggesting a southwest to northwest age progression and that all of these seamounts are older than the Selvagen Islands. Trace element and Sr–Nd–Pb isotopic composition of the Selvagen Islands and neighboring seamounts are consistent with their origin from the Canary plume. Interaction of the weak Canary mantle plume with a slow moving plate appears to be responsible for generating a 450-km-wide, irregular hotspot track extending 800 km from the youngest Canary Island of Hierro in the southwest to Lars seamount in the northeast.
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    The Grimsey hydrothermal field offshore North Iceland: crustal structure, faulting and related gas venting (2001)
    Elsevier
    In:  Earth and Planetary Science Letters, 193 (3-4). pp. 409-421.
    Details
    Publication Date: 2017-08-09
    Description: The results of a combined geophysical and geochemical research program are presented that focused on Grimsey hydrothermal field (GHF) which is located at 66 degrees 35'30"N, 17 degrees 39'30"W east of the island of Grimsey in the Tjornes Fracture Zone. The vent field is situated at the sourthernmost tip of a submarine ridge which is connected to the offshore part of the Theistareykir Fissure Swarm. Reflection seismic recordings were interpreted in conjunction with earthquake catalogue data to detect active fault structures and potential heat sources in the subsurface. An inter-linked fracture network forming a downwards converging system of faults connected to a deep-reaching normal fault is assumed to provide the preferential pathways for gases (He-3, CO2, CH4 etc.) migrating from a possible deep-seated gas source (lower crust/upper mantle) to the surface. The location of hydrothermal vents was detected by concentration measurements of dissolved methane in the water column, which coincide with polarity reversals in the seismic seafloor reflection. Both the molecular composition of the gas and the isotopic composition of methane at GHF indicate a predominating abiogenic source (Fischer-Tropsch reactions at 250-500 degreesC) mixed with thermogenic hydrocarbons. New seismic data from the GHF were compared with gas geochemical data which indicate that the thermogenic hydrocarbons are related to (up to 60 m thick) sediments deposited in a basin located east of the ridge.
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    Deep‐sea, high‐resolution, hydrography and current measurements using an autonomous underwater vehicle: The overflow from the Strait of Sicily (2001)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 28 (13). p. 2645.
    Details
    Publication Date: 2018-02-14
    Description: AUTOSUB‐2, an autonomous underwater vehicle (AUV) developed by the Southampton Oceanography Centre, was used for high resolution hydrographic surveys in the Sicily Strait. A combination of “seasoar” type profiling and terrain following missions were undertaken and velocity and hydrographic measurements taken from AUTOSUB‐2 were compared with concurrent shipboard hydrographic and velocity profiles. Even though shipboard stations were separated by just 5 to 8 km along the mission path, data from the AUV showed small scale variability that was missed by the shipboard sampling. In this paper we present the example of an intense jet, with maximum speed greater than 0.50 m s−1, less than 4 km wide.
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    Hydrography of the Pontevedra Ria: Intra-annual spatial and temporal variability in a Galician coastal system (NW Spain) (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 106 (C9). p. 19845.
    Details
    Publication Date: 2018-04-18
    Description: In order to ameliorate the dearth of existing scientific knowledge concerning the hydrography of the Pontevedra Ria, a systematic investigation was carried out between October 1997-98. Salinity variations were closely related to river discharge whereas bottom waters presented oceanic characteristics over the whole year. Current was controlled by tide, river discharge, and wind in the internal ria where the highest velocities were directed along the ria channel with a low transverse component. Favorable atmospheric conditions in spring induced coastal upwelling up the continental shelf. In May the upwelling was sufficiently strong to be detected in the inner ria and intensified in July and August, cooling the ria water to 12 degrees -14 degreesC. Upwelling ceased in September, and from November to March seawater transported by the poleward current (35.9; 15 degreesC) was detected on the shelf. From January until March, unanticipated favorable upwelling conditions provoked an influx of poleward inside the ria. Ria intrusion of poleward water and association with occasional winter upwelling conditions has not been observed previously. Isopycnic three-dimensional (3-D) surface and 2-D isopycnal maps show that with high river runoff or intense upwelling, lower-salinity water leaves the ria near the northern margin in the surface layer. Under negative upwelling conditions, the water is partially dammed inside the ria and exits the ria when the wind speed falls. During upwelling events, ENACW penetrated the ria, especially near the southern shore. Arrival of ENACW at the northern entrance impedes the outward water flow through this mouth.
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    Dynamical and cloud-radiation feedbacks in El Nino and greenhouse warming (2001)
    AGU (American Geophysical Union)
    In:  Geophysical Research Letters, 28 (8). p. 1539.
    Details
    Publication Date: 2018-02-14
    Description: An El Niño‐like steady response is found in a greenhouse warming simulation resulting from coupled ocean‐atmosphere dynamical feedbacks similar to those producing the present‐day El Niños. There is a strong negative cloud‐radiation feedback on the sea surface temperature (SST) anomaly associated with this enhanced eastern equatorial Pacific warm pattern. However, this negative feedback is overwhelmed by the positive dynamical feedbacks and cannot diminish the sensitivity of the tropical SST to enhanced greenhouse gas concentrations. The enhanced eastern‐Pacific warming in the coupled ocean‐atmosphere system suggests that coupled dynamics can strengthen this sensitivity.
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  • 65
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    Marine dissolved organic matter: can its C:N ratio explain carbon overconsumption? (2001)
    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 48 (1). pp. 49-62.
    Details
    Publication Date: 2016-10-28
    Description: Carbon overconsumption, i.e. the consumption of inorganic carbon relative to inorganic nitrogen in excess of the Redfield ratio at the sea surface, was examined in relation to the dynamics of dissolved organic carbon and nitrogen (DOC and DON) in the northeast Atlantic. We observed the presence of N-poor dissolved organic matter (DOM) in surface water during summer, requiring the consumption of inorganic carbon and nitrogen in a ratio exceeding the Redfield ratio. The C : N ratio of bulk DOM is not only different from the Redfield ratio but also variable, i.e. no fixed conversion factor of C and N exists where DOM is important in C and N transformations. The existence of N-poor DOM is recognized as a feature typical of oligotrophic systems. At the same time, the C : N ratios of particles conform to Redfield stoichiometry as does deep-ocean chemistry. The implications of this finding are discussed, the conclusion being that, while DOM buildup contributes to CO2 drawdown seasonally, its impact on long-term carbon and nitrogen balance of the ocean is small.
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    Reversal of density dependence of juvenile Littorina littorea (Gastropoda) growth in response to periphyton nutrient status (2001)
    Elsevier
    In:  Journal of Sea Research, 45 (2). pp. 95-103.
    Details
    Publication Date: 2017-07-14
    Description: Experimental periphyton communities were grown in aquaria receiving media of differently enriched seawater (fully enriched, without Si enrichment, without N and P enrichment) and supplied differently with medium (batch and weekly replacement). Periphyton was subject to grazing by 1-6 individuals of juvenile Littorina littorea. Periphyton biomass was higher in the replacement aquaria than in the batch aquaria and higher in the full and the -Si medium than in the -NP medium. The N:C ratio of the periphyton increased with Littorina number in the batch aquaria and was unaffected by Littorina number in the replacement aquaria. Diatoms were most dominant in the -NP treatments and rarest in the -Si treatments. Chlorophytes were dominant in the -Si and the fully enriched treatments, but also Cyanobacteria contributed significantly to periphyton biomass in those treatments under nutrient replacement. Somatic growth of Littorina was negatively correlated to Littorina density in the replacement aquaria and positively density dependent in the batch aquaria. The latter is explained by improved food quality under stronger grazing pressure.
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    Radiogenic isotopes: New tools help reconstruct paleocean circulation and erosional input (2001)
    AGU (American Geophysical Union)
    In:  Eos, Transactions American Geophysical Union, 82 (6). pp. 66-71.
    Details
    Publication Date: 2017-02-10
    Description: Ocean and atmosphere circulation and continental weathering regimes have undergone great changes over thousands of years as well as tens of millions of years. During the glacial stages of the Pleistocene, ocean circulation was generally more sluggish and deep water circulation in the Atlantic had a shallower flow. At the same time, weathering on the continents was enhanced by glacial erosion, particularly in high northern latitudes, which increased the input of erosional detritus into the ocean. In addition, atmospheric pressure gradients were larger, leading to higher wind speeds and increased supply of aeolian dust to the ocean. Prior to the onset of Northern Hemisphere glaciation and pronounced glacial/interglacial cyclicity at ∼3 m.ya., global climate was warmer than at present. There is also evidence for a more vigorous thermohaline circulation during the early Pliocene.
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    Wintertime nutrients in the North Atlantic - New approaches and implications for estimates of seasonal new production (2001)
    Elsevier
    In:  Marine Chemistry, 74 (4). pp. 245-260.
    Details
    Publication Date: 2017-08-22
    Description: Observations of wintertime nutrient concentrations in surface waters are scarce in the temperate and subarctic North Atlantic Ocean. Three new methods of their estimation from spring or early summer observations are described and evaluated. The methods make use of a priori knowledge of the vertical distribution of oxygen saturation and empirical relationships between nutrient concentrations and oxygen saturation. A south–north increase in surface water winter nutrient concentration is observed. Winter nitrate concentrations range from very low levels of about 0.5 μmol dm−3 at 33°N to about 13.5 μmol dm−3 at 60°N. Previous estimates of winter nitrate concentrations have been overestimates by up to 50%. At the Biotrans Site (47°N, 20°W), a typical station in the temperate Northeast Atlantic, a mean winter nitrate concentration of 8 μmol dm−3 is estimated, compared to recently published values between 11 and 12.5 μmol dm−3. It is shown that most of the difference is due to a contribution of remineralised nitrate that had not been recognized in previous winter nutrient estimates. Mesoscale variation of wintertime nitrate concentrations at Biotrans are moderate (less than ±15% of the regional mean value of about 8 μmol dm−3). Interannual variation of the regional mean is small, too. In the available dataset, there was only 1 year with a significantly lower regional mean winter nitrate concentration (7 μmol dm−3), presumably due to restricted deep mixing during an atypically warm winter. The significance of winter nitrate estimates for the assessment of spring-bloom new production and the interpretation of bloom dynamics is evaluated. Applying estimates of wintertime nitrate concentrations of this study, it is found that pre-bloom new production (0.275 mol N m−2) at Biotrans almost equals spring-bloom new production (0.3 mol N m−2). Using previous estimates of wintertime nitrate yields unrealistically high estimates of pre-bloom new production (1.21–1.79 mol N m−2) which are inconsistent with observed levels of primary production and the seasonal development of biomass.
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    Analysis of fluid inclusions in seafloor hydrothermal precipitates: testing and application of an integrated GC/IC technique (2001)
    Elsevier
    In:  Chemical Geology, 177 (3-4). pp. 443-470.
    Details
    Publication Date: 2016-05-11
    Description: The principal research objective was to test an integrated gas (GC) and ion chromatographic (IC) technique for analysis of trapped fluids in seafloor hydrothermal precipitates and to compare the results with independently analyzed vent fluids. Twenty-three samples of chalcopyrite, pyrite, sphalerite, barite and anhydrite from hydrothermal chimneys from four seafloor sites, Axial Seamount (Juan de Fuca Ridge), the Vai Lili vent field (Lau Basin), the TAG hydrothermal field (Mid-Atlantic Ridge), and the 21°N vent field (East Pacific Rise), as well as of pyrite/marcasite and quartz from the TAG mound, were analyzed. A new type of blank for sulphides and sulphates was also developed. Water contents obtained by GC analysis are in agreement with known compositions of seafloor hydrothermal solutions. Also, the volatiles occur in the same order of abundance as in vent fluids CO2〉N2(±CO±Ar±O2)≥CH4〉COS〉C2–C3 hydrocarbons. For all analyzed hydrothermal fluids, the mean Cl− concentrations are similar to those for the respective measured vent fluid compositions. Furthermore, the GC/IC results are directly comparable to salinity data determined by microthermometric methods. NH4+ can be enriched and is most probably formed by decomposition of organic matter. Volatile concentrations in fluid inclusions and data from vent fluids differ significantly for some of the investigated sites. Furthermore, the GC data indicate systematic variations regarding the volatile contents of trapped fluids from different active seafloor hydrothermal systems. Fluid inclusion volatile data of samples from the ASHES vent field at Axial Seamount define an inclined array consistent with phase separation.
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    Potassic igneous rocks from the vicinity of epithermal gold mineralization, Lihir Island, Papua New Guinea (2001)
    Elsevier
    In:  Lithos, 57 (2-3). pp. 163-186.
    Details
    Publication Date: 2016-05-12
    Description: Many world-class porphyry copper–gold and epithermal gold deposits worldwide are hosted by volatile-rich and oxidized alkaline rocks. This study investigates potassic igneous rocks from the vicinity of epithermal gold mineralization at Lihir Island, Papua New Guinea. The island consists of five Pliocene–Pleistocene stratovolcanoes, one of which hosts Ladolam, one of the largest epithermal gold deposits discovered to date. Petrographically, the rocks range from porphyritic trachybasalts, trachyandesites and latites to rare phonolites and olivine–clinopyroxene cumulates. In some places, these rocks are cut by monzodiorite stocks. According to Al-in-hornblende barometry, the main crystallization of these rocks occurred close to the surface. Titanium-in-hornblende thermometry as well as olivine–spinel geothermometry and oxygen barometry indicate temperatures of 787–965°C at elevated oxygen fugacities (fO2) of 1.4–4.8 log units above that of the FMQ buffer. Although previous studies have suggested high fO2 of alkaline rocks associated with copper–gold mineralization based on abundant primary magnetite contents, this is the first direct determination of the fO2 of such rocks. High fO2 of parental melts commonly delays the early crystallization of magmatic sulphides; this is important because metals such as Au and Cu preferentially partition into sulphide phases resulting in their depletion in the melt during increasing fractionation. Geochemically, the rocks range from primitive to relatively evolved compositions, as reflected by their SiO2 (45.8–55.0 wt.%) and MgO (1.4–15.3 wt.%) contents and variable concentrations of mantle-compatible elements (130–328 ppm V, 1–186 ppm Ni). Their high K2O content (up to 4.7 wt.%), high average K2O/Na2O ratios (0.8) and high average Ce/Yb ratios (14) are typical of high-K igneous rocks transitional to shoshonites. Although these rocks formed by decompression melting related to back-arc rifting in the Manus Basin, the high LILE, low LREE and very low HFSE concentrations are typical of potassic igneous rocks from oceanic (island) arc settings. The reason for this remarkable composition is the partial melting of subduction-modified lithospheric mantle, which developed in a stalled subduction zone. Mica phenocrysts in the rocks reveal unusually high halogen concentrations. Magmatic phlogopites contain high F (up to 5.6 wt.%) and elevated Cl contents (〈0.08 wt.%). Hydrothermal biotites from rocks that display potassic alteration have low F (〈0.08 wt.%), but very high Cl concentrations (up to 0.15 wt.%). It is suggested that chloride complexing largely controlled the abundances of Au and Cu in the aqueous fluids responsible for the hydrothermal gold mineralization at Ladolam.
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    Decadal upper ocean temperature variability in the tropical subtropical Pacific (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 106 . pp. 8971-8988.
    Details
    Publication Date: 2018-04-18
    Description: Decadal variability in upper ocean temperature in the Pacific is studied by using observations and results from model experiments. Especially propagation of upper ocean thermal anomalies from the midlatitudes to the tropics is studied as a possible source for decadal equatorial thermocline variability. In the observations, propagation along the subtropical gyre of the North Pacific is clear. However, no propagation into the equatorial region is found. Model experiments with an ocean model forced with observed monthly wind and wind stress anomalies are performed to study the apparent propagation. Distinct propagation of thermal anomalies in the subtropics is found in the model, although the amplitude of the anomalies is small. The anomalies clearly propagate into the tropics, but they do not reach the equatorial region. The small response at the equator to extratropical variability consists of a change in the mean depth of the thermocline. It appears that most variability in the subtropics and tropics is generated by local wind stress anomalies. The results are discussed by using results from a linear shallow water model in which similar features are found
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    Nitrous oxide cycling in the Arabian Sea (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 106 (C1). pp. 1053-1066.
    Details
    Publication Date: 2017-11-24
    Description: Depth profiles of dissolved nitrous oxide (N2O) were measured in the central and western Arabian Sea during four cruises in May and July–August 1995 and May–July 1997 as part of the German contribution to the Arabian Sea Process Study of the Joint Global Ocean Flux Study. The vertical distribution of N2O in the water column on a transect along 65°E showed a characteristic double-peak structure, indicating production of N2O associated with steep oxygen gradients at the top and bottom of the oxygen minimum zone. We propose a general scheme consisting of four ocean compartments to explain the N2O cycling as a result of nitrification and denitrification processes in the water column of the Arabian Sea. We observed a seasonal N2O accumulation at 600–800 m near the shelf break in the western Arabian Sea. We propose that, in the western Arabian Sea, N2O might also be formed during bacterial oxidation of organic matter by the reduction of IO3 − to I−, indicating that the biogeochemical cycling of N2O in the Arabian Sea during the SW monsoon might be more complex than previously thought. A compilation of sources and sinks of N2O in the Arabian Sea suggested that the N2O budget is reasonably balanced.
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  • 73
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    Controls on the Cretaceous and Cenozoic evolution of seawater composition, atmospheric CO2 and climate (2001)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 65 (18). pp. 3005-3025.
    Details
    Publication Date: 2019-09-23
    Description: A new box model for the global carbon-calcium-strontium cycle is developed to simulate the evolution of Cretaceous and Cenozoic seawater and atmosphere. The model accounts for carbon masses in ocean and atmosphere, in carbonate, in particulate organic carbon (POC), and in the mantle. Major processes considered in the model are mantle degassing and hydrothermal fluxes, alteration of oceanic crust, chemical weathering, metamorphism of carbonates, carbonate accumulation, carbonate turnover in subduction zones, and the turnover of POC. Model outputs are partial pressure of CO2 (pCO2), seawater pH, concentrations of Ca, Sr, and HCO3 in seawater as well as the C and Sr isotopic composition of seawater and marine carbonates. A comprehensive review of current fluxes is given to define the flux equations and parameters. Secular trends recorded in marine carbonates are used to constrain the remaining open model parameters. The model includes a new parameterization of silicate weathering considering the contribution of young volcanic deposits. The weathering of these deposits consumes a large fraction of volcanically-released CO2 and maintains moderate pCO2 levels during periods of intense mantle degassing and volcanic/tectonic activity. Further negative feed-back is provided by POC burial which is coupled to pCO2-dependent weathering rates. The model produces high Ca concentrations during the Cretaceous and a strong increase in both pH and carbonate alkalinity during the late Cenozoic. Moreover, it predicts high atmospheric CO2 and surface temperatures for the mid-Cretaceous and early Cenozoic and low values for the late Cenozoic icehouse world thus suggesting a close coupling between climate and pCO2. Finally, it demonstrates that the mid-Cretaceous greenhouse was caused by enhanced volcanic/tectonic activity and confirms that the late Cenozoic cooling has been induced by an increase in silicate weatherability caused by enhanced mountain building and erosion.
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  • 74
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    Sea Floor Methane Hydrates at Hydrate Ridge, Cascadia Margin (2001)
    AGU (American Geophysical Union)
    In:  In: Natural gas hydrates: occurrence, distribution, and detection. , ed. by Paull, C. Geophysical Monograph Series, 124 . AGU (American Geophysical Union), Washington, DC, pp. 87-99.
    Details
    Publication Date: 2017-06-27
    Type: Book chapter , NonPeerReviewed
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  • 75
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    Seismic architecture and sediment distribution within the Holocene barrier reef–lagoon complex of Mayotte (Comoro archipelago, SW Indian Ocean) (2001)
    Elsevier
    In:  Palaeogeography, Palaeoclimatology, Palaeoecology, 175 . pp. 343-368.
    Details
    Publication Date: 2017-01-23
    Description: Twenty gravity cores and a large set of high-resolution seismic profiles from various lagoonal settings were studied to determine the Holocene sediment distribution and sequence architecture within the Mayotte barrier reef–lagoon complex. The Holocene seismic sequence comprises a type 1 sequence with lowstand, transgressive and highstand systems tracts. The lowstand systems tract consists of a paleosoil horizon formed during subaerial exposure. The transgressive systems tract is composed of four depositional systems: (1) inner transgressive layer, (2) proximal and distal incised valley fills, (3) mid-lagoonal layer and (4) keep-up or catch-up fringing and barrier reef sequence. The highstand systems tract comprises three depositional systems: (1) of a proximal terrigenous wedge, (2) mid-lagoonal and distal carbonate sands or muds and (3) reefal carbonates. Our studies show that the nature of the Holocene sequence is controlled by the rate and amplitude of sea-level rise and environmental changes, which are expressed by changes in clastic sediment supply and carbonate production. The pre-Holocene topography and water dynamics steer the vertical and spatial sediment thickness distribution of the Holocene. Additional important parameters are the proximity to a source area (carbonate or terrigenous) and the width of the depositional area. Climate dynamics are also of great importance while they determine carbonate production and terrigenous runoff. Sedimentation rates in the subtidal settings always lacked behind sea-level rates. Thus, a steep relief was created keeping most lagoonal parts within the deep subtidal realm in which sediment production was not efficient enough to fill up accommodation space. In addition, wave and/or current energy might prevent the fill up of the lagoon. This ultimately resulted in a typical empty bucket morphology. Only a high amplitude sea-level fall would allow the subtidal lagoon to build up to base-level. Unfilled accommodation space, therefore, must be a very common feature in the geologic record.
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  • 76
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    Supply and demand of nutrients and dissolved organic matter at and across the NW European shelf break in relation to hydrography and biogeochemical activity (2001)
    Elsevier
    In:  Deep Sea Research Part II: Topical Studies in Oceanography, 48 (14-15) . pp. 3023-3047.
    Details
    Publication Date: 2020-08-05
    Description: As part of the OMEX I project, nutrient determinations were made on 17 cruises in the region of the Goban Spur and La Chapelle Bank between 46 and 51°N, in all seasons of the year, between 1993–1995. Over this period no change was detectable in the structure of the water masses below the deep winter mixed layer. The N : P (dissolved nitrate-to-phosphate) ratio changed from 16 at 100-m depth to less than 15 at 3300-m depth. At intermediate depths nutrient and oxygen data indicate the presence of Mediterranean Outflow water overlying Labrador Sea Water at its most eastern extension. Estimated maximum levels of production in the spring bloom are the total N-limited new primary production equivalent between 24 and 41 gC m−2, the equivalent maximum diatom production is 11 gC m−2. Measurements during the spring bloom suggest a conversion factor of 1 μM nitrate to 1 μg l−1 chlorophyll, at the shelf break, which is consistent with other recent measurements in European shelf seawaters. Sediment trap data suggest that 80% (5.4 g m−2) of the opal produced in the spring bloom dissolved before reaching the sediment trap at 600 m. A comparison of the winter and summer profiles for dissolved silicon suggests a similar dissolution of 9±3 g opal m−2 above 300-m depth. Measurements of dissolved organic carbon (DOC) in September 1994 show an enrichment of 7 μM-C above the seasonal thermocline relative to the winter values (52±4 μM). In winter dissolved organic nitrogen represents 40% of the pool of total dissolved nitrogen. There is no consistent evidence of an increase in the concentration of DON during summer. Measurements of nitrate in surface waters in January 1994 show that concentrations off-shelf vary with the temperature of the water and are related to the depth of winter mixing. Mixing in surface waters is discontinuous at the shelf break, demonstrating the degree to which exchange across the shelf break is limited even in winter. OMEX winter measurements of nitrate concentrations can be used to estimate the flow of water across the shelf break that would be required to maintain the nitrogen balance in the North Sea at a steady state. The estimate is 0.6 Sv (1 Sv=106 m3 s−1), which is similar to an earlier estimate of a total flow of 1.7 Sv based on salt budgets (cf. Huthnance, Deutsche Hydrographische Zeitschrift, 49 (1997) 153).
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  • 77
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    Particle transport processes at slope environments - event driven flux across the Barents Sea continental margin (2001)
    Elsevier
    In:  Marine Geology, 175 . pp. 237-250.
    Details
    Publication Date: 2017-06-27
    Description: Recent studies of the vertical flux of organic matter into the deep ocean have prompted the search for key organic compounds (biomarkers) as tracers for its production, flux and burial into the sediment. Particulate matter was collected with sediment traps moored at the Barents Sea continental margin (75°11.78′N/12°29.21′E; water depth 2050 m) at 610, 1840 and 1950 m depth. The compositions of the organic material in the two bottoms near traps differ significantly. This difference cannot be the result of a change of the vertical sedimentation alone. A combination of biomarker analyses, quantitative microscopy and bulk parameter determinations on water and sediment trap samples is used in this study to demonstrate that a turbidity plume event at the shelf edge is a vehicle to transport organic and lithogenic particles at high velocities to the benthos of the lower continental margin. It is suggested that fine particles were advected into the trap at 1850 m, whereas the coarser fraction of higher settling velocities, passing several resuspension loops entered the lower trap.
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  • 78
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    Introduction to Special Section: Ocean Measurements and Models of Carbon Sources and Sinks (2001)
    AGU (American Geophysical Union)
    In:  Global Biogeochemical Cycles, 15 . pp. 3-10.
    Details
    Publication Date: 2018-03-15
    Description: This issue of Global Biogeochemical Cycles contains a remarkable set of papers, which critically evaluate a variety of model- and observation-based approaches addressing the oceanic distribution, storage, and transport of CO2. Three of the papers are concerned with observation-based estimates of excess (or anthropogenic) CO2 [Coatanoan et al., this issue; Sabine and Feely, this issue; Chen, this issue]. They focus on the approaches, assumptions, and uncertainties involved in detecting the excess CO2 signal above the ocean's large and variable natural dissolved inorganic carbon (DIC) background.
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  • 79
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    Gas Hydrate-Associated Carbonates and Methane-Venting at Hydrate Ridge: Classification, Distribution, and Origin of Authigenic Lithologies (2001)
    AGU (American Geophysical Union)
    In:  In: Natural Gas Hydrates: Occurrence, Distribution, and Detection. , ed. by Paull, C. K. and Dillon, W. P. Geophysical Monograph Series, 124 . AGU (American Geophysical Union), Washington, DC, pp. 99-113. ISBN 0-87590-982-5
    Details
    Publication Date: 2016-01-28
    Description: Hydrate Ridge is part of the accretionary complex at the Cascadia margin and is an area of widespread carbonate precipitation induced by the expulsion of methane-rich fluids. All carbonates on Hydrate Ridge are related to the methanecarbon pool either through anaerobic methanotrophy or through methanogenesis. Several petrographically distinct lithologies occur in boulder fields or in massive autochtonous chemoherm complexes which include methane-associated diagenetic mudstones and venting-induced breccias. The mudstones result from methane diagenesis in different sediment horizons and geochemical environments related to very slow methane venting. Cemented bioturbation casts occur as fragments, complex framework or as clasts together with bivalve shells as part of intraformational breccias, which are restricted to chemoherm complexes. Here, fluids ascend from the sub-seafloor and support aragonite-dominated carbonate precipitation near or at the sediment surface. Voids within mudclast breccias are either aragonite-rich indicating a formation near the surface at vent sites or are cemented by dolomite, which indicates formation in deeper parts of the sediment column. Brecciation is caused by tectonic or slump processes. In addition, we recognized a direct relationship between gas hydrates and sediment fracturing as well as the oxygen isotope composition of carbonate lithologies. Such gas hydrate-associated carbonates either show layered megapores and veins as relics of the original gas hydrate fabric or consist of aragonite-cemented intraclast breccias formed by growing and decomposing gas hydrate near the sediment surface. Both rock fabrics and the enrichment of 180 in high Mg-calcite demonstrate carbonate-forming mechanisms of gas hydrate.
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  • 80
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    Hydrous metasomatism of oceanic sub-arc mantle, Lihir, Papua New Guinea: petrology and geochemistry of fluid-metasomatised mantle wedge xenoliths (2001)
    Elsevier
    In:  Earth and Planetary Science Letters, 188 (1-2). pp. 169-183.
    Details
    Publication Date: 2016-05-11
    Description: Ultramafic, mafic and sedimentary xenoliths have been recovered from a recently erupted, shoshonitic submarine cinder cone (Tubaf and Edison volcanoes) from the Tabar–Lihir–Tanga–Feni island arc, located in the New Ireland basin of Papua New Guinea. These samples represent a proxy drill hole that can be re-assembled into an ‘ophiolite-type’ model of oceanic lithosphere. Petrographic and geochemical examination of the gabbroic and depleted mantle xenoliths indicates that the New Ireland fore-arc lithosphere is a fragment of ancient Pacific Plate generated at a mid-ocean ridge spreading centre and transported to the Pacific–Australian Plate margin. Convergent margin processes subjected the harzburgitic mantle wedge to hydrofracturing and hydration metasomatism at T=790–1030°C as a consequence of dewatering of a subducted slab. Advection of a high-density, H2O-rich fluid containing a substantial dissolved component (alkali aluminosilicate melt and aqueous carbon and sulphur species) through these mantle fractures caused a net transfer of soluble elements from the lower to upper mantle wedge and created a network of oxidised (ΔFMQ≈1.8–2.0) metasomatised peridotite enriched in orthopyroxene, clinopyroxene, phlogopite, amphibole, magnetite, and Fe–Ni sulphides. The vein mineral assemblage magnetite+sulphide indicates precipitation from a hydrous fluid with high SO2/H2S, consistent with the hydrous fluid being derived from dehydration of subducted, altered oceanic crust. Preferential partial melting of these metasomatically enriched mantle wedge regions could account for the highly oxidised, sulphur- and alkali-rich nature of the high-K calc-alkaline volcanoes of the Tabar–Lihir–Tanga–Feni island chain.
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  • 81
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    Carbon isotopes of biomarkers derived from methane-oxidizing microbes at Hydrate Ridge, Cascadia convergent margin (2001)
    AGU (American Geophysical Union)
    In:  In: Natural Gas Hydrates: Occurrence, Distribution, and Detection. , ed. by Paull, C. K. and Dillon, W. P. Geophysical Monograph Series, 124 . AGU (American Geophysical Union), Washington, DC, pp. 115-129.
    Details
    Publication Date: 2017-06-27
    Type: Book chapter , NonPeerReviewed
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  • 82
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    First observations of high-temperature submarine hydrothermal vents and massive anhydrite deposits off the north coast of Iceland (2001)
    Elsevier
    In:  Marine Geology, 177 (3-4). pp. 199-220.
    Details
    Publication Date: 2018-01-02
    Description: High-temperature (250°C) hydrothermal vents and massive anhydrite deposits have been found in a shallow water, sediment-filled graben near 66°36′N in the Tjornes Fracture Zone north of Iceland. The site is located about 30 km offshore, near the small island of Grimsey. The main vent field occurs at a depth of 400 m and consists of about 20 large-diameter (up to 10 m) mounds and 1–3 m chimneys and spires of anhydrite and talc. A north–south alignment of the mounds over a 1-km strike length of the valley floor suggests that their distribution is controlled by a buried fault. Widespread shimmering water and extensive white patches of anhydrite in the sediment between the mounds indicates that the entire 1-km2 area occupied by the vents is thermally active. A 2-man research submersible JAGO was used to map the area and to sample vent waters, gases, and chimneys. Actively boiling hydrothermal vents occur on most of the mounds, and extensive two-phase venting indicates that the field is underlain by a large boiling zone (200×300 m). The presence of boiling fluids in shallow aquifers beneath the deposits was confirmed by sediment coring. The highest-temperature pore fluids were encountered in talc- and anhydrite-rich sedimentary layers that occur up to 7 m below the mounds. Baked muds underlie the talc and anhydrite layers, and pyrite is common in stockwork-like fractures and veins in the hydrothermally altered sediments. However, massive sulfides (pyrite–marcasite crusts) were found in only one relict mound. Subseafloor boiling has likely affected the metal-carrying capacity of the hydrothermal fluids, and deposition of sulfides may be occurring at greater depth. Although the mounds and chimneys at Grimsey resemble other deposits at sedimented ridges (e.g. Middle Valley, Escanaba Trough, Guaymas Basin), the shallow water setting and extensive boiling of the hydrothermal fluids represent a distinctive new type of seafloor hydrothermal system.
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  • 83
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    Metal biogeochemistry in the Tinto-Odiel rivers (Southern Spain) and in the Gulf of Cadiz: A synthesis of the results of TOROS project (2001)
    Elsevier
    In:  Continental Shelf Research, 21 (18-19). pp. 1961-1973.
    Details
    Publication Date: 2014-02-04
    Description: TOROS (Tinto-Odiel-River-Ocean Study) has been studying the biogeochemical processes which control metals and nutrients cycling in the mixing zone of the Tinto and Odiel rivers (SW Spain) and has established the fate of metals in the Gulf of Cadiz in relation to hydrodynamics and biological activity. The Tinto and Odiel rivers are small, with a combined mean discharge of 18m 3/s. They drain the largest sulphide mineralisation in the world. Predominantly, Zn-Cu-Pb mineralisation has been worked since 2500yr BC. The estuarine zone includes both an extensive area of salt marsh and an intensively industrialised urban area. As a consequence of pyrite oxidation, the Tinto and Odiel rivers are strongly acidic (pH〈3) with extremely high and variable metal concentrations. Transition metals are poorly removed from the water column in the mixing zone. Moreover, drainage from large phosphogypsum waste deposits contributes to As, Hg, U and phosphate contamination of the estuary. The collapse of the tailing reservoir at los Frailes in 1998 had not impacted the chemistry of the coastal waters up to 6 months later. A large plume of metal-rich waters due to the Tinto and Odiel discharges occurs along the coast of the Gulf of Cadiz. This plume affects seasonally the Atlantic inflow through the Strait of Gibraltar. The dispersion of the metal discharges has been simulated by injection of a tracer in the 3-D hydrodynamical model. Both model and field study clearly show the inflow of metal contaminated Spanish Shelf Water through the Strait of Gibraltar. © 2001 Elsevier Science Ltd. All right reserved.
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  • 84
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    Comparison of sample storage protocols for the determination of nutrients in natural waters (2001)
    Elsevier
    In:  Water Research, 35 (15). pp. 3670-3678.
    Details
    Publication Date: 2017-05-30
    Description: There have been several reports on storage protocols for the determination of nutrients in natural waters but each one has been limited to a particular sample matrix and they have reached different, matrix specific conclusions. The aim of this study was therefore to systematically apply the various recommended storage protocols to a range of natural water matrices. Samples from four contrasting sites in the UK, collected in late winter (February, 1999), were filtered and stored under different conditions (-80°C, -20°C, 4°C and at 4°C and -20°C with 0.1 (v/v) chloroform) for up to 247 days prior to analysis. The sites were the River Frome in Dorset (a chalk stream catchment) and three sites from the Tamar Estuary (draining a non-chalk catchment) with salinities of 0.5‰, 10‰ and 34‰. Samples and controls were analysed for total oxidised nitrogen (TON) and filterable reactive phosphorus (FRP) using a segmented flow analyser with spectrophotometric detection. To investigate possible seasonal effects (particularly changes in biological and chemical matrix composition), a second sampling campaign was undertaken in early autumn (October, 1999). The results showed that the optimum storage conditions for the determination of TON and FRP were highly matrix dependent, with significant differences in FRP stability between the Frome and Tamar catchments (due to different calcium concentrations) and between samples of different salinities (due to different bacterial populations and/or dissolved organic matter). General guidelines for sample handling and storage are listed and matrix specific recommendations presented for samples rich in calcium and dissolved organic matter. Copyright © 2001 Elsevier Science Ltd.
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    Determination of iron in seawater (2001)
    Elsevier
    In:  Analytica Chimica Acta, 442 (1). pp. 1-14.
    Details
    Publication Date: 2014-02-04
    Description: Iron plays an important role in oceanic biogeochemistry and is known to limit biological activity in certain ocean regions. Such regions have a replete complement of major nutrients but low primary production of phytoplankton due to low ambient iron concentrations. The determination of iron in seawater is a major challenge, although much progress has been made during the last two decades. Techniques for total dissolved iron and iron speciation have been developed in order to rationalise its biogeochemical cycling and better understand its role in limiting phytoplankton growth. In this paper, a critical review of historical and current analytical methods for the determination of iron in seawater is presented and their capabilities evaluated. The need for standard protocols for the clean sampling and storage of low-level (〈1 nM) iron seawater in order to maintain sample integrity is emphasised. The importance of laboratory and shipboard intercomparison exercises to distinguish between environmental variability and operationally measured fractions is also considered. © 2001 Elsevier Science B.V. All rights reserved.
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  • 86
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    UV digestion of seawater samples prior to the determination of copper using flow injection with chemiluminescence detection (2001)
    Elsevier
    In:  Analytica Chimica Acta, 440 (1). pp. 27-36.
    Details
    Publication Date: 2014-02-04
    Description: A purpose built UV digestion system was successfully used for the breakdown of Cu complexing organic ligands in seawater samples, prior to total dissolved Cu determination using flow injection with chemiluminescence detection (FI-CL) and on-line micro-column preconcentration/matrix removal. Residual dissolved organic carbon (DOC) was quantified using a DOC analyser. Humic acid (1.8-7.2 mg l-1C) in ultra high purity (UHP) water was completely broken down within 4h in all batch experiments (125 and 400 W lamps; with and without 15 mM H2O2 and, as expected, was more rapid with the 400 W lamp, in the presence of H2O2, and for lower humic acid concentrations. UV digestion experiments with seawater showed that the residual DOC concentration after batch UV treatment (4h) was 〈0.08 mg l-1C compared with >0.32 mg l-1C after on-line irradiation (residence time 11.2 min). Therefore, the batch method was more efficient than on-line UV digestion at breaking down added humic acid and naturally present organic compounds in seawater. However, the release of Cu from metal complexing organic matter in seawater and estuarine water was the same using both on-line and batch UV digestion (sample irradiation residence time: 5.6 min and 8h, respectively). UV digestion is, therefore, a contamination-free approach for seawater pretreatment prior to micro-column preconcentration and FI-CL determination of total dissolved Cu and should also be applicable to the selective determination of the total dissolved fractions of other trace metals in seawater (e.g. Co, Fe, Mn). © 2001 Elsevier Science B.V. All rights reserved.
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  • 87
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    The fate of added iron during a mesoscale fertilisation experiment in the Southern Ocean (2001)
    Elsevier
    In:  Deep-Sea Research Part II-Topical Studies in Oceanography, 48 (11-12). pp. 2703-2743.
    Details
    Publication Date: 2014-02-04
    Description: The first Southern Ocean Iron RElease Experiment (SOIREE) was performed during February 1999 in Antarctic waters south of Australia (61°S, 140°E), in order to verify whether iron supply controls the magnitude of phytoplankton production in this high nutrient low chlorophyll (HNLC) region. This paper describes iron distributions in the upper ocean during our 13-day site occupation, and presents a pelagic iron budget to account for the observed losses of dissolved and total iron from waters of the fertilised patch. Iron concentrations were measured underway during daily transects through the patch and in vertical profiles of the 65-m mixed layer. High internal consistency was noted between data obtained using contrasting sampling and analytical techniques. A pre-infusion survey confirmed the extremely low ambient dissolved (0.1 nM) and total (0.4 nM) iron concentrations. The initial enrichment elevated the dissolved iron concentration to 2.7 nM. Thereafter, dissolved iron was rapidly depleted inside the patch to 0.2-0.3 nM, necessitating three re-infusions. A distinct biological response was observed in iron-fertilised waters, relative to outside the patch, unequivocally confirming that iron limits phytoplankton growth rates and biomass at this site in summer. Our budget describing the fate of the added iron demonstrates that horizontal dispersion of fertilised waters (resulting in a quadrupling of the areal extent of the patch) and abiotic particle scavenging accounted for most of the decreases in iron concentrations inside the patch (31-58 and 12-49 of added iron, respectively). The magnitude of these loss processes altered towards the end of SOIREE, and on days 12-13 dissolved (1.1 nM) and total (2.3 nM) iron concentrations remained elevated compared to surrounding waters. At this time, the biogenic iron pool (0.1 nM) accounted for only 1-2 of the total added iron. Large pennate diatoms (〉 20 μm) and autotrophic flagellates (2-20 μm) were the dominant algal groups in the patch, taking up the added iron and representing 13 and 39 of the biogenic iron pool, respectively. Iron regeneration by grazers was tightly coupled to uptake by phytoplankton and bacteria, indicating that biological Fe cycling within the bloom was self-sustaining. A concurrent increase in the concentration of iron-binding ligands on days 11-12 probably retained dissolved iron within the mixed layer. Ocean colour satellite images in late March suggest that the bloom was still actively growing 42 days after the onset of SOIREE, and hence by inference that sufficient iron was maintained in the patch for this period to meet algal requirements. This raises fundamental questions regarding the biogeochemical cycling of iron in the Southern Ocean and, in particular, how bioavailable iron was retained in surface waters and/or within the biota to sustain algal growth. © 2001 Elsevier Science Ltd.
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  • 88
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    Plasticity and stabilization of neuromuscular and CNS synapses: interactions between thrombin protease signaling pathways and tissue transglutaminase (2001)
    Elsevier
    In:  International Review of Cytology, 211 . pp. 153-177.
    Details
    Publication Date: 2019-08-29
    Description: The first association of the synapse as a potential site of neurodegenerative disease burden was suggested for Alzheimer's disease (AD) almost 30 years ago. Since then protease:protease inhibitor (P:PI) systems were first linked to functional regulation of synaptogenesis and synapse withdrawal at the neuromuscular junction (NMJ) more than 20 years ago. Confirmatory evidence for the involvement of the synapse, the rate-limiting or key unit in neural function, in AD did not become clear until the beginning of the 1990s. However, over the past 15 years evidence for participation of thrombin, related serine proteases and neural PIs, homologous and even identical to those of the plasma clot cascade, has been mounting. Throughout development a balance between stabilization forces, on the one hand, and breakdown influences, on the other, becomes established at synaptic junctions, just as it does in plasma clot proteins. The formation of protease-resistant cross-links by the transglutaminase (TGase) family of enzymes may add to the stability for this balance. The TGase family includes coagulation factor XIIIA and 8 other different genes, some of which may also influence the persistence of neural connections. Synaptic location of protease-activated, G-protein-coupled receptors (PARs) for thrombin and related proteases, their serpin and Kunitz-type PIs such as protease nexin I (PNI), α1-antichymotrypsin (α-ACT), and the Kunitz protease inhibitor (KPI)-containing secreted forms of β-amyloid protein precursor (β-APP), along with the TGases and their putative substrates, have all been amply documented. These findings strongly add to the conclusion that these molecules participate in the eventual structural stability of synaptic connections, as they do in coagulation cascades, and focus trophic activity on surviving terminals during periods of selective contact elimination. In disease states, this imbalance is likely to be shifted in favor of destabilizing forces: increased and/or altered protease activity, enhanced PAR influence, decreased and/or altered protease inhibitor function, reduction and/or alteration in tTG expression and activity, and alteration in its substrate profile. This imbalance further initiates a cascade of events leading to inappropriate programmed cell death and may well be considered evidenced of synaptic apoptisis.
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  • 89
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    Sampling of sub-seafloor aquifers by a temporary well for CFC age dating and natural tracer investigations (2001)
    Elsevier
    In:  Journal of Sea Research, 46 (2). pp. 177-185.
    Details
    Publication Date: 2019-09-23
    Description: Based on a sediment vibro corer, a tool for the sampling of sub-seafloor groundwater aquifers has been developed and successfully deployed in a coastal area of the western Baltic. The device was designed to obtain pure groundwater samples from coarse sediments to be used for tracer investigations and CFC age dating. Operated from a medium size research vessel, a well pipe tipped with a filter segment is vibrated into the sediment down to the aquifer. Groundwater entering the filter is pumped to the ship by a conventional submersible pump situated in the well's filter tip. Groundwater is continuously analysed on board for O2, salinity, pH, Eh and temperature, prior to sampling for CFC and radioisotope analysis. All parameters indicate that pure groundwater had been obtained. CFC concentrations are very low suggesting that the groundwater of this shallow sub-seafloor aquifer recharged prior to 1950. This finding is in accordance with other hydrogeological evidence that this aquifer, located only 4–5 m below the seafloor, is connected to fairly deep confined sandy aquifers on land of Pleistocene or Miocene age. Applying the method described, it is possible to obtain sufficient sample volumes for analyses of natural groundwater tracers such as radon-222 and CFCs which can be used to trace submarine groundwater discharge as well as the origin of groundwater in such environments.
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  • 90
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    The late Quaternary stratigraphy and environments of northern Eurasia and the adjacent Arctic seas—new contributions from QUEEN (2001)
    Elsevier
    In:  Global and Planetary Change, 31 (1-4). vii-x.
    Details
    Publication Date: 2019-09-23
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  • 91
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    A Holocene pollen record from the Laptev Sea shelf, northern Yakutia (2001)
    Elsevier
    In:  Global and Planetary Change, 31 (1-4). pp. 141-153.
    Details
    Publication Date: 2019-09-23
    Description: Holocene shelf deposits from the Laptev Sea shelf (northern Yakutia) were investigated with palynological means. Data were obtained from a 467-cm-long sediment sequence from the southeastern Laptev Sea (74°30 N/136°00 E). The chronology of the core reaches back to 9.4 calendar years (cal. ka), yielding an average sample resolution of ∼100 years. The temporal changes in pollen and spore spectra of the marine record are primarily the result of variations of transport mechanisms, i.e., the large rivers draining into the shelf sea, the atmospheric circulation, and the coastal erosion. Because of the close land-shelf linkage due to riverine connections, the trends observed in the shelf data seem to be in good agreement with the Holocene vegetational evolution of the coastal hinterland. An enhanced transfer of tree pollen onto the shelf during the middle Holocene began around 7.5 cal. ka and is interpreted as the result of the northernmost occurrence of the treeline between 9 and 3.8 cal. ka. A similar time-coeval accordance between land and shelf pollen records is observed for the late Holocene climatic cooling trend in Arctic Siberia. In the shelf record, this cooling is characterized by increasing abundance of herbaceous pollen that commenced after 2.7 cal. ka, which is about 1 cal. ka later than on land.
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  • 92
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    Detailed mineralogical evidence for two nearly identical glacial/deglacial cycles and Atlantic water advection to the Arctic Ocean during the last 90,000 years (2001)
    Elsevier
    In:  Global and Planetary Change, 31 (1-4). pp. 23-44.
    Details
    Publication Date: 2019-09-23
    Description: Three cores recovered off the northwest of Svalbard were studied with respect to glacial/interglacial changes of clay and bulk mineralogy, lithology and organic geochemistry. The cores cover the Late Quaternary Marine Isotope Stages (MIS) 6–1 (ca. 170,000 years) and are located in the vicinity of the Polar Front which separates the warm Atlantic water of the Westspitsbergen Current and the cold Polar Water of the Transpolar Drift. Globally driven changes in the paleoenvironment like the variable advection of warm Atlantic water into the Arctic Ocean can be distinguished from regional events by means of source mineral signatures and organic geochemistry data. In particular, a combination of high organic carbon and low carbonate contents, high C/N-ratios, a particular lithology and a distinct bulk and clay mineral assemblage can be related to Svalbard ice sheet developments between 23,000 and 19,500 14C years. This complex sediment pattern has been traced to the northwest of Spitsbergen as far north as 82°N. Additionally, the same signature has been recognized in detail in upper MIS 5 sediments. The striking similarity of the history of the Svalbard/Barents Sea Ice Sheet during the late and early/middle Weichselian is elaborated. Both sediment horizons are intercalated between biogenic calcite rich core sequences which contain the so-called “High Productivity Zones” or “Nordway Events” related to the increased advection of warm Atlantic water to the Arctic Ocean. This study provides further evidence that the meridional circulation pattern has been present during most of the Weichselian and that the ice cover was often reduced in the northeastern Fram Strait and above the Yermak Plateau. Our findings contradict the widely used reconstructions in modelling of the last glaciation cycle and reveal a much more dynamic system in the Fram Strait and southwestern Eurasian Basin of the Arctic Ocean.
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  • 93
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    The 1997/1998 Mass Mortality of Corals: Effects on Fish Communities on a Tanzanian Coral Reef (2001)
    Elsevier
    In:  Marine Pollution Bulletin, 42 (2). pp. 127-131.
    Details
    Publication Date: 2020-01-29
    Description: The abnormally high surface temperatures in the world's oceans during 1997/1998 resulted in widespread coral bleaching and subsequent coral mortality. An experiment was performed to study the effects of this coral mortality as well as the influence of the structural complexity on fish communities on a Tanzanian coral reef. Changes in fish communities were investigated on plots of transplanted corals after 88% of these corals had died. A distinct shift in fish community composition was found, although diversity was not affected. Fish abundance rose by 39% mostly due to an increase in herbivores, which seemed to benefit from enhanced algal growth on the dead corals. Fish abundance, species diversity and community composition were also strongly influenced by the structural complexity provided by the live and dead corals. This suggests that a coral reef can support abundant and diverse fish populations also after the corals have died as long as the reef structure is sustained.
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  • 94
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    Amino acid sequence of squid troponin C (2001)
    Elsevier
    In:  Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology, 129 (4). pp. 787-796.
    Details
    Publication Date: 2021-07-01
    Description: The complete amino acid sequence of squid Todarodes pacificus troponin C (TnC), which was shown to bind only 1 mol Ca2+/mol, was determined by both the Edman and cDNA methods. The squid TnC is composed of 147 amino acids including an unblocked Pro at the N-terminus and the calculated molecular weight is 17 003.9. Among the four potential Ca2+-binding sites, namely sites I–IV from the N-terminus, only site IV completely satisfied the consensus amino acid sequence for the active Ca2+-binding loop. This indicates that squid TnC possesses a single Ca2+-binding site at the site IV as scallop TnCs [Nishita et al., J. Biol. Chem. 269 (1994) 3464–3468; Ojima et al., Arch. Biochem. Biophys. 311 (1994) 272–276). The sequence homology of squid TnC to TnCs of scallop, arthropods, and rabbit was 61%, 31–38%, and 31%, respectively. In the sequence of the central D/E-helix region of squid and scallop TnCs, a deletion of three amino acids was required to maximize the homology with the other TnCs.
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  • 95
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    The Late Quaternary evolution of the western Laptev Sea continental margin, Arctic Siberia — implications from sub-bottom profiling (2001)
    Elsevier
    In:  Global and Planetary Change, 31 (1-4). pp. 105-124.
    Details
    Publication Date: 2021-03-11
    Description: High-resolution seismic profiles (PARASOUND, 4 kHz) of the western Laptev Sea continental margin and the adjacent Vilkitsky Strait were studied in order to gain new evidence about the Weichselian glaciations in Central Siberia and to test reconstructions of maximum ice sheet extents. Four regionally correlatable seismic units, named I (youngest) to IV, were identified in the upper Quaternary sedimentary succession: (I) a thin drape; (II) prograding wedge-shaped deposits along the shelf edge; (III) layered sediments of draping and infilling character with increasing thickness towards the western Laptev Sea shelf edge and the Vilkitsky Strait; (IV) stacked debris-flow deposits. The thin drape of unit I is radiocarbon-dated to Holocene and mainly deposited during the transgression of the Laptev Sea. The wedge-shaped deposits of unit II are interpreted as river deltas, referring to point sources along the shelf edge during the Late Weichselian sea-level lowstand. This indicates that the river input across the Laptev Sea shelf was continuous during marine isotope stage (MIS) 2. The layered sediments of unit III suggest hemipelagic conditions indicative of a sea-level highstand. The pronounced thickening of unit III towards the shelf edge of the western Laptev Sea reflects the lowering of the global sea level during MIS 3. This is associated with increased riverine input due to the northward shift of the Siberian coastline. The stacked debris-flow deposits of unit IV extend continuously from the shelf edge in the Vilkitsky Strait to the continental rise of the western Laptev Sea continental margin. They indicate that large quantities of sediments were deposited directly on the upper continental slope during advances of the Kara Sea ice sheet to the shelf break. These ice-proximal conditions are presumably linked to the Middle Weichselian glaciation (MIS 4). Our evidence confirm earlier reconstructions, suggesting that in central Siberia, the Middle Weichselian glaciation (MIS 4) was of larger extent than the Late Weichselian glaciation (MIS 2).
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  • 96
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    A Molecular Phylogeny of the Octopoda (Mollusca: Cephalopoda) Evaluated in Light of Morphological Evidence (2001)
    Elsevier
    In:  Molecular Phylogenetics and Evolution, 21 (3). pp. 388-397.
    Details
    Publication Date: 2021-07-05
    Description: In this paper we examine the phylogenetic relationships of the Octopoda utilizing molecular sequence data from the cytochrome c oxidase subunit I (COI) gene and compare results from analyses of molecular data with classifications and phylogenies based on previous morphological studies. Partial COI sequences (657 bp, excluding primers) were obtained from 28 species representing most of the diversity in the Order Octopoda, along with a sequence from the established sister taxon to the Octopoda, Vampyroteuthis infernalis. Our results exhibit a number of basic differences from inferences based on standard morphological data. We attempt to resolve these differences based on our confidence in various morphological features. An important finding is the failure of the molecular data to support the monophyly of the Octopodidae. This family contains over 90% of the species in the Suborder Incirrata and has always been difficult to define. Statistical tests constraining Octopodidae monophyly by use of parsimony and maximum-likelihood techniques suggest that all incirrates may be derived from octopodids.
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  • 97
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    Isolation and characteristics of trypsin inhibitor from the hepatopancreas of a squid (Todarodes pacificus) (2001)
    Elsevier
    In:  Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology, 130 (1). pp. 117-123.
    Details
    Publication Date: 2021-07-01
    Description: Trypsin inhibitor was purified from the hepatopancreas of squid (Todarodes pacificus). The final inhibitor preparation was nearly homogeneous by SDS-PAGE with an estimated molecular weight of approximately 6300. The squid trypsin inhibitor was acid- and heat-stable, and active against trypsins from the pyloric ceca of starfish (Asterias amurensis) and saury (Cololabis saira) and porcine pancreatic trypsin. Amino acid composition of the squid trypsin inhibitor was compared with other invertebrate trypsin inhibitors. The squid trypsin inhibitor inhibited the autolysis of walleye pollock (Theragra chalcogramma) myofibrillar proteins.
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  • 98
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    Polarized light scattering by inhomogeneous hexagonal monocrystals. Validation with ADEOS-POLDER measurements (2001)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Atmospheres, 106 (D11). pp. 14301-14312.
    Details
    Publication Date: 2018-01-24
    Description: Various in situ measurements of the light-scattering diagram in ice clouds were performed with a new nephelometer during several airborne campaigns. These measurements were favorably compared with a theoretical scattering model called Inhomogeneous Hexagonal Monocrystal (IHM) model. This model consists in computing the scattering of light by an ensemble of randomly oriented hexagonal ice crystals containing spherical impurities of soot and air bubbles. It is achieved by using a combination of ray tracing, Mie theory, and Monte Carlo techniques and enables to retrieve the six independent elements of the scattering matrix. This good agreement between nephelometer measurements and IHM model provides an opportunity to use this model in order to analyze ADEOS-POLDER total and polarized reflectance measurements over ice clouds. POLDER uses an original concept to observe ice cloud properties, enabling to measure reflectances and polarized reflectances, for a given scene, under several (up to 14) viewing directions. A first analysis of ice cloud spherical albedoes over the terrestrial globe for November 10, 1996, and April 23, 1997, shows a rather good agreement between measurements and modeling. Moreover, polarized reflectances are also calculated and show a satisfactory agreement with measurements.
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  • 99
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    Combined sensitive analytical methods for cholecystokinin levels and tryptic activity in individual fish larvae (2001)
    Elsevier
    In:  Journal of Experimental Marine Biology and Ecology, 265 . pp. 101-115.
    Details
    Publication Date: 2017-07-10
    Description: A protocol for combined analysis of cholecystokinin (CCK) levels based on radioimmunoassay (RIA) and fluorescence tryptic enzyme activity (FTA) was developed in order to accomplish a sensitive analysis of individual bodies and gut segments of fish larvae. Methanol was used for CCK extraction. The gut of herring larvae contained 8.9±1.2 fmol CCK/mg dry weight and in the post-larval Atlantic halibut the CCK levels varied significantly (p〈0.05) from 20.9±15.6 to 101.8±56.7 fmol/mg dry weight for separated intestinal and pyloric segments, respectively. Acid solution, 0.02 mol/l HCl–CaCl2 (pH 1.8), and alkaline solution, 0.1 mol/l Tris–0.02 mol/l CaCl2 (pH 8.0) were tested to prepare crude trypsin extracts from Coregonids and Atlantic halibut larvae. The tryptic activity of crude extracts prepared with acid solution was enhanced by a factor of 3.19±0.52 compared to the tryptic activity of crude extracts prepared with alkaline solution. The larval trypsins (from yolk sac larvae) were stable in methanol, preserving 88% of its starting activity after 6 days of storage. Based on the results, the method of extraction using methanol and acid solution (pH 1.8) was suitable for the combined analysis for CCK levels and FTA in gut segments or single larvae. The potential application of these analytical tools may allow a better understanding of the individual variability of gut functionality, nutritional condition and the feeding activity of developing fish based on their content of CCK and tryptic activity.
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  • 100
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    Molecular phylogeny of small brown algae, with special reference to the systematic position of Caepidium antarcticum (Adenocystaceae, Ectocarpales) (2001)
    Elsevier
    In:  Cryptogamie, Algologie, 22 (2). pp. 187-200.
    Details
    Publication Date: 2020-01-07
    Description: Nuclear ribosomal DNA (3′-SSU, ITS, 5′-LSU) and plastid-encoded (rbcL and Rubisco spacer) sequences were determined in Caepidium antarcticum and compared to homologous sequences of relatives from Ectocarpales, Scytothamnales, and other brown algae. Plastidial sequences confirmed a previous conclusions from nuclear ribosomal sequences that some taxa with stellate plastids (Asterocladon and relatives) form the closest outgroup to the Ectocarpales as yet identified. To reconcile nomenclature with the clades resolved in recent molecular studies, we propose a subdivision of the Ectocarpales in five families. Plastidial sequences support the recent proposal of Adenocystaceae, and all sequences suggest that Caepidium should be included in this family. As a further result, Geminocarpus was shown to belong to the same clade as Pylaiella and a number of other brown algae with an isomorphic life history and discoid plastids. We recognise this clade, whose correct name is Acinetosporaceae, as another family in the Ectocarpales. We also propose to unite a number of genetically related taxa, which were formely classified in different families, in an extended Chordariaceae. The remaining species of the Ectocarpales belong to Scytosiphonaceae and to Ectocarpaceae, the latter containing only Ectocarpus and Kuckuckia.
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