ALBERT

Description: Highlights: • Lagrangian ocean analysis is a powerful way to analyse the output of ocean circulation models • We present a review of the Kinematic framework, available tools, and applications of Lagrangian ocean analysis • While there are unresolved questions, the framework is robust enough to be used widely in ocean modelling Abstract: Lagrangian analysis is a powerful way to analyse the output of ocean circulation models and other ocean velocity data such as from altimetry. In the Lagrangian approach, large sets of virtual particles are integrated within the three-dimensional, time-evolving velocity fields. Over several decades, a variety of tools and methods for this purpose have emerged. Here, we review the state of the art in the field of Lagrangian analysis of ocean velocity data, starting from a fundamental kinematic framework and with a focus on large-scale open ocean applications. Beyond the use of explicit velocity fields, we consider the influence of unresolved physics and dynamics on particle trajectories. We comprehensively list and discuss the tools currently available for tracking virtual particles. We then showcase some of the innovative applications of trajectory data, and conclude with some open questions and an outlook. The overall goal of this review paper is to reconcile some of the different techniques and methods in Lagrangian ocean analysis, while recognising the rich diversity of codes that have and continue to emerge, and the challenges of the coming age of petascale computing.

Description: New bathymetric and seismic reflection data from the Santorini–Amorgos Tectonic Zone in the southern Cyclades have been analysed and a description of the morphology and tectonic structure of the area has been presented. The basins of Anhydros, Amorgos and Santorini–Anafi have been distinguished together with the intermediate Anhydros Horst within the NE-SW oriented Santorini–Amorgos Tectonic Zone which has a length of 60–70 km and a width of 20–25 km. The basins represent tectonic grabens or semi-grabens bordered by the active marginal normal faults of Santorini–Anafi, Amorgos, Ios, Anhydros and Astypalaea. The Santorini–Anafi, Amorgos and Ios marginal faults have their footwall towards the NW where Alpine basement occurs in the submarine scarps and their hangingwall towards the southeast, where the Quaternary sediments have been deposited with maximum thickness of 700 m. Six sedimentary Units 1–6 have been distinguished in the stratigraphic successions of the Santorini–Anafi and the western Anhydros Basin whereas in the rest area only the upper four Units 3–6 have been deposited. This shows the expansion of the basin with subsidence during the Quaternary due to ongoing extension in a northwest-southeast direction. Growth structures are characterized by different periods of maximum deformation as this is indicated by the different sedimentary units with maximum thickness next to each fault. Transverse structures of northwest-southeast direction have been identified along the Santorini–Amorgos Tectonic Zone with distinction of the blocks/segments of Santorini, Anhydros/Kolumbo, Anhydros islet and Amorgos. Recent escarpments with 7–9 m offset observed along the Amorgos Fault indicate that this was activated during the first earthquake of the 7.5 magnitude 1956 events whereas no recent landslide was found in the area that could be related to the 1956 tsunami.

Description: Highlights • The genetic model for Algoma-type BIF is modified taking into account S-MIF results. • Metal and sulfur sources are decoupled and reflect diverse microbial metabolisms. • Sulfur deposited with oxide-facies BIF is mostly atmospheric in origin. • Little juvenile sulfur is found, despite the proximity to volcanic sources. Abstract Neoarchean Algoma-type banded iron formations (BIFs) are widely viewed as direct chemical precipitates from proximal volcanic–hydrothermal vents. However, a systematic multiple sulfur isotope study of oxide-facies BIF from a type locality in the ca. 2.74 Ga Temagami greenstone belt reveals mainly bacterial turnover of atmospheric elemental sulfur in the host basin rather than deposition of hydrothermally cycled seawater sulfate or sulfur from direct volcanic input. Trace amounts of chromium reducible sulfur that were extracted for quadruple sulfur isotope (32S–33S–34S–36S) analysis record the previously known mass-independent fractionation of volcanic SO2 in the Archean atmosphere (S-MIF) and biological sulfur cycling but only minor contributions from juvenile sulfur, despite the proximity of volcanic sources. We show that the dominant bacterial metabolisms were iron reduction and sulfur disproportionation, and not sulfate reduction, consistent with limited availability of organic matter and the abundant ferric iron deposited as Fe(OH)3. That sulfur contained in the BIF was not a direct volcanic–hydrothermal input, as expected, changes the view of an important archive of the Neoarchean sulfur cycle in which the available sulfur pools were strongly decoupled and only species produced photochemically under anoxic atmospheric conditions were deposited in the BIF-forming environment.

Description: Thyroid hormones (THs) are key regulators of growth, development, and metabolism in vertebrates and influence early life development of fish. TH is produced in the thyroid gland (or thyroid follicles) mainly as T4 (thyroxine), which is metabolized to T3 (3,5,3'-triiodothyronine) and T2 (3,5-diiodothyronine) by deiodinase (DIO) enzymes in peripheral tissues. The action of these hormones is mostly exerted by binding to a specific nuclear thyroid hormone receptor (THR). In this study, we i) cloned and characterized thr sequences, ii) investigated the expression pattern of the different subtypes of thrs and dios, and iii) studied how temperature affects the expression of those genes in artificially produced early life history stages of European eel (Anguilla anguilla), reared in different thermal regimes (16, 18, 20 and 22 °C) from hatch until first-feeding. We identified 2 subtypes of thr (thrα and thrβ) with 2 isoforms each (thrαA, thrαB, thrβA, thrβB) and 3 subtypes of deiodinases (dio1, dio2, dio3). All thr genes identified showed high similarity to the closely related Japanese eel (Anguilla japonica). We found that all genes investigated in this study were affected by larval age (in real time or at specific developmental stages), temperature, and/or their interaction. More specifically, the warmer the temperature the earlier the expression response of a specific target gene. In real time, the expression profiles appeared very similar and only shifted with temperature. In developmental time, gene expression of all genes differed across selected developmental stages, such as at hatch, during teeth formation or at first-feeding. Thus, we demonstrate that thrs and dios show sensitivity to temperature and are involved in and during early life development of European eel.

Description: Highlights • Gases collected from dry seepages and bubbling or dissolved in springs of the ophiolitic body of Kizildag (Turkey). • Large compositional variation (H2- CH4 or N2-dominated) • Hydrogen derives from low temperature serpentinization processes • Methane mainly derives from abiotic processes • Large isotopic fractionation of methane at one site due to biological oxidation Abstract We investigated the geochemical features of the gases released from the Kizildag ophiolitic complex (Hatay, Turkey). Twenty-three samples both dissolved in hyperalkaline waters and free gases (bubbling gases and dry seeps) were collected. Samples were analysed for their chemical (He, H2, O2, N2, CH4 and CO2) and isotopic (He, δ13C-CH4, δ2H-CH4, δ2H-H2) composition including the content and C-isotopic composition of C2 to C5 alkanes in free gases. Analytical results evidence H2 production through low-temperature (〈80 °C) serpentinization processes and subsequent abiogenic CH4 production through Fischer-Tropsch-type reactions. In some sample small additions of methane either of microbial or of thermogenic origin can be hypothesized. At one of the sites (Kisecik) a clear fractionation pattern due to microbial methane oxidation leading to strongly enriched isotopic values (δ13C +15‰ and δ2H −68‰) and depletion in methane concentrations has been evidenced. At the dry gas seep of Kurtbagi methane flux measurements have been made and a preliminary output estimation of about 1000 kg per year has been obtained.

Description: Highlights • Large seafloor depressions with diameters of up 10 km across have been mapped on the southern Chatham Rise, New Zealand. • Seismic reflection data show scarce indications for vertical fluid flow but no clear link between fluid flow and depressions. • Methane gas or methane hydrates appear to be absent on the southern Chatham Rise. • Seismic evidence suggests that vertical fluid flow was likely fuelled by polygonal faulting and silica diagenesis • The depressions are the results of erosion and sediment drift deposition of bottom currents associated with the Subtropical Front. Abstract Several giant seafloor depressions were investigated on the Chatham Rise offshore New Zealand using mainly bathymetric and seismic data, supplemented by sediment cores and reported porewater geochemistry data. The depressions have diameters of up to 11 km and occur on the southern flank of the Chatham Rise in water depths between 600 and 900 m, i.e. roughly underneath the location of the strongest thermal gradients of the Subtropical Front (STF) and characterized by eastward flowing currents. With up to 150 m of relief the depressions cut into post-Miocene deposits. Some of the depressions are partially filled with drift deposits that have similar seismic characteristics as the surrounding sediments and consist of alternations of silty muds and silts. Seismic profiles also show completely filled depressions that no longer have a bathymetric expression. Despite several pipe structures indicating vertical fluid flow, neither active fluid seepage nor indications for past fluid seepage are present at the seafloor of the Chatham Rise. Also, both pore water geochemistry and geophysical data do not show indications for an existing or past gas hydrate system in the area. Instead, seismic data suggest widespread polygonal faulting and the presence of silica diagenetic fronts. The release of mineral-bound water during silica diagenesis or fluid expulsion during sediment compaction can explain the presence of vertical fluid flow features but not the giant depressions themselves. Instead, the depressions are interpreted as the result of scouring by strong bottom currents for which fluid venting may have created the nucleation points.

Description: The spectacular Lusi mud eruption started in northeast Java, Indonesia, the 29th of May 2006 following a M6.3 strike slip seismic event. After the earthquake several mud pools aligned along a NE-SW direction appeared in the Sidoarjo district. The most prominent eruption site was named Lusi. Lusi is located ∼10 km to the NE of the northernmost cone of the Arjuno-Welirang volcanic complex with which it is connected by the Watukosek Fault System. In this study, we applied the HVSR method, which is a common tool used for site effect investigations as well as to infer buried structures and reconstruct sub-surface geology. The method is based on the ratio of the horizontal to vertical components of ground motion and it generally exhibits a peak corresponding to the fundamental frequency of the site. Spectral ratio results highlight a fundamental frequency band between 0.4 and 1.0 Hz in the Lusi neighborhood. We interpret these peaks as related to the velocity lithological contrast at depth between alluvial deposits and bluish grey clay. Our analysis also highlights the presence of a “depocenter”, characterized by fundamental frequency up to 0.3 Hz, which is interpreted as the subsidence caused by withdrawal of mud and fluids from depth (as also shown by the comparison of the HVSR results with gravimetry data). Moreover, in the area of the Lusi vent a broad-band frequency range is related to the Lusi conduit. In this paper, we show that detailed microtremor surveys could be used as a preliminary and fast approach to locate mud conduits with sufficient precision.

Description: Highlights • Morphology and evolution of a Cretaceous contourite drift in the eastern Central Atlantic oceanic basin. • Backstripping of the regional cross section reveals the water-depth range at which the observed sedimentary features occur. • Cretaceous geological interval and oceanic model mirrors the stratification of the Modern Ocean and the morphology of its seafloor. Abstract The evolution and resulting morphology of a Cretaceous contourite drift in the eastern Central Atlantic oceanic basin is investigated in unprecedented detail using seismic imaging and age-calibrated cross-margin sections. The margin, from the shelf, slope to deep-water and abyssal plain is constructed by a succession of erosive and depositional mounded structures that relate to bottom-water currents and sediment winnowing. The regional mapping of these drifts, sediment waves and gravitational sedimentary systems allows us to test the Upper Cretaceous paleocirculation model. Combined with flexural backstripping of the regional cross section, it reveals the water-depth range at which the observed sedimentary features occur. A possible late Albian to Turonian contourite drift system is observed from Guinea to Mauritania. The development of a shallow to deep oceanic circulation system is a key element in the rock record, with implications for the palaeoceanography and layering of the Cretaceous ocean. The Cretaceous geological interval and oceanic model mirrors the stratification of the modern ocean and the morphology of its seafloor from offshore Morocco to Guinea.

Description: Contents of platinum group elements (PGE—Os, Ir, Ru, Rh, Pt, and Pd) and rhenium in basalts of different geochemical types from the ophiolite complex of the Kamchatsky Mys Peninsula have been determined by the isotope dilution-mass spectrometry method. The total contents of PGE in different basalts are commensurate (1.4-3.6 ppb), but the element ratios vary considerably. A specific feature of the rocks is the low degree of PGE fractionation (Pd/Ir = 0.9-6.6, Pt/Pd = 1.0-7.3), which makes them similar to the Hawaiian tholeiitic basalts and picrites. The most fractionated PGE pattern is observed for alkali basalt (Pd/Ir = 6.6), and the least fractionated one, for E-MORB (Pd/Ir = 1.7). The similarity of the PGE patterns of basalts of different geochemical types suggests their similar mantle sources. We propose a model explaining the geochemical features of the basalts of the Kamchatsky Mys ophiolite complex by an impurity of the Earth’s core material in the plume source. The Ir/Pd-Ru/Pd and Pd/10-Ir-Ru discrimination diagrams can be used to identify enriched (plume) basalts based on their PGE content.

Description: Global maps of maximum bottom particle concentration, benthic nepheloid layer thickness, and integrated particle mass in benthic nepheloid layers (BNL) based on 2412 global profiles collected using the Lamont Thorndike nephelometer from 1964 to 1984 are compared with maps of those same properties compiled from 6392 global profiles measured by transmissometers from 1979 to 2016. Outputs from both instruments were converted to particulate matter concentration (PM). The purposes of this paper are to compare global differences and similarities in the location and intensity of BNLs measured with these two independent instruments over slightly overlapping decadal time periods, to combine the data sets in order to expand the time scale of global in situ measurements of BNLs, and to gain insight about the factors creating/sustaining BNLs. The similarity between general locations of high and low particle concentration BNLs during the two time periods indicates that the driving forces of erosion and resuspension of bottom sediments are spatially persistent during recent decadal time spans, though in areas of strong BNLs, intensity is highly episodic. Topography and well-developed current systems play a role. These maps will help to understand deep ocean sediment dynamics, linkage with upper ocean dynamics, the potential for scavenging of adsorption-prone elements near the seafloor, and provide a comprehensive comparison of these data sets on a global scale. During both time periods, BNLs are weak or absent in most of the Pacific, Indian, and Atlantic basins away from continental margins. High surface eddy kinetic energy is associated with the Kuroshio Current east of Japan. Both data sets show weak BNLs south of the Kuroshio, but no transmissometer data have been collected beneath the Kuroshio itself. Sparse nephelometer data show moderate BNLs just north of the Kuroshio Extension, but with much lower concentrations than beneath the Gulf Stream. Strong BNLs are found in areas where eddy kinetic energy in overlying waters, mean kinetic energy near bottom, and energy dissipation within the bottom boundary layer are high. Areas of strongest BNLs include the Western North Atlantic, Argentine Basin (South Atlantic), areas around South Africa tied to the Agulhas Current region, and somewhat random locations in the Antarctic Circumpolar Current of the Southern Ocean.