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  • Other Sources  (1,095)
  • Institut für Meereskunde  (964)
  • AGU
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  • 1
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    Modeling the shape and velocity of magmatic intrusions, a new numerical approach (2023)
    Wiley | AGU
    Details
    Publication Date: 2024-02-07
    Description: Dykes are magma-filled fractures propagating through the brittle crust. Understanding the physics of dyking process is essential to mitigate the volcanic hazard associated with the opening of new eruptive fissures at the surface. Often, physics-based models view either fracturing of the host rock or viscous flow of the magma as the dominating energy sink during dyke propagation. Here, we provide a numerical model that captures the coupling of fracturing at the crack tip and the transport of a viscous fluid. Built with the boundary element technique, our model allows for computation of the shape and velocity of a growing fluid-filled crack accounting for the viscosity of the fluid: The fluid flow induces a viscous pressure drop acting at the crack walls, and modifies the shape of the crack. The energy conservation equation provides the constraints to solve for the crack growth velocity, assuming that brittle fracturing and viscous flow are the main processes that dissipate energy. Using a parameter range that represents typical magmatic intrusions, we obtain crack shapes displaying some typical characteristics, including a tear-drop head and an open tail that depend on rock rigidity, magma viscosity and buoyancy. We show that viscous forces significantly contribute to the energy dissipated during the propagation of magmatic dykes. Applied to the 1998 intrusion at Piton de la Fournaise (La Réunion Island), we provide ranges of dyke lengths and openings by adjusting the numerical velocity to the one deduced from the migration of volcano-tectonic events. Key Points We present a new modeling scheme to compute the shape and velocity of a growing fluid-filled crack Our magmatic dykes show a tear drop head and open tail, on a wide range of propagation velocities We reproduce the velocity and fit important parameters for the 1998 Piton de la Fournaise intrusion
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  • 2
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    The Mid‐Lithospheric Discontinuity Caused by Channel Flow in Proto‐Cratonic Mantle (2023)
    Wiley | AGU
    Details
    Publication Date: 2024-02-07
    Description: Global geophysical observations show the presence of the enigmatic mid‐lithospheric discontinuity (MLD) at depths of ca. 80–150 km which may question the stability and internal structure of the continental lithosphere. While various mechanisms may explain the MLD, the dynamic processes leading to the seismic observations are unclear. Here we present a physical mechanism for the origin of MLD by channel flow in the cratonic mantle lithosphere, triggered by convective instabilities at cratonic margins in the Archean when the mantle was hot. Our numerical modeling shows that the top of the frozen‐in channel flow creates a shear zone at a depth comparable to the globally observed seismic MLD. Grain size reduction in the shear zone and accumulation of percolated melts or fluids along the channel top may reduce seismic wave speeds as observed below the MLD, while the channel flow itself may explain radial anisotropy of seismic wave speeds and change in direction of the seismic anisotropic fast axis. The proposed mechanism is valid for a broad range of physically realistic parameters and that MLD may have been preserved since its formation in the Archean. The intensity of the channel flow ceased with time due to secular cooling of the Earth's interior. The new mechanism may reshape our understanding of the evolution and stability of cratonic lithosphere.
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  • 3
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    Relation between oceanic plate structure, patterns of interplate locking and microseismicity in the 1922 Atacama Seismic Gap (2023)
    AGU | Wiley
    Details
    Publication Date: 2024-02-07
    Description: We deployed a dense geodetic and seismological network in the Atacama seismic gap in Chile. We derive a microseismicity catalog of 〉30,000 events, time series from 70 GNSS stations, and apply a transdimensional Bayesian inversion to estimate interplate locking degree. We identify two highly locked regions of different sizes whose geometries appear to control seismicity patterns. Interface seismicity concentrates beneath the coastline just downdip of the highest locking. A region of lower interplate locking around 27.5ºS coincides with higher seismicity levels, a high number of repeating earthquakes and events extending further towards the trench. Having shown numerous signs of aseismic deformation (slow-slip events and earthquake swarms), this area is situated where the Copiapó Ridge is subducted. While these findings suggest that the structure of the downgoing oceanic plate prescribes patterns of interplate locking and seismicity, we note that the Taltal Ridge further north lacks a similar signature.
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  • 4
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    Hindered Trench Migration Due To Slab Steepening Controls the Formation of the Central Andes (2022)
    AGU | Wiley
    Details
    Publication Date: 2024-02-07
    Description: The formation of the Central Andes dates back to ∼50 Ma, but its most pronounced episode, including the growth of the Altiplano-Puna Plateau and pulsatile tectonic shortening phases, occurred within the last 25 Ma. The reason for this evolution remains unexplained. Using geodynamic numerical modeling we infer that the primary cause of the pulses of tectonic shortening and growth of the Central Andes is the changing geometry of the subducted Nazca plate, and particularly the steepening of the mid-mantle slab segment which results in a slowing down of the trench retreat and subsequent increase in shortening of the advancing South America plate. This steepening first happens after the end of the flat slab episode at ∼25 Ma, and later during the buckling and stagnation of the slab in the mantle transition zone. Processes that mechanically weaken the lithosphere of the South America plate, as suggested in previous studies, enhance the intensity of the shortening events. These processes include delamination of the mantle lithosphere and weakening of foreland sediments. Our new modeling results are consistent with the timing and amplitude of the deformation from geological data in the Central Andes at the Altiplano latitude. Key Points The steepening of the slab due to slab buckling hinders the trench retreating and explains the main pulsatile phases of the deformation during the last 25 Ma The absolute motion of the overriding plate controls the regime of subduction dynamics Flat slab and eclogitization are required to weaken and then shorten the overriding plate when the slab steepens and the trench is hindered
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 5
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    Quantifying the Contribution of Ocean Mesoscale Eddies to Low Oxygen Extreme Events (2022)
    Wiley | AGU
    Details
    Publication Date: 2024-02-07
    Description: Ocean mesoscale eddies have been identified as drivers of localized extremely low dissolved oxygen concentration ([O2]) conditions in the subsurface. We employ a global physical-biogeochemical ocean model at eddy-permitting resolution to conduct a census of open-ocean eddies near Eastern Boundary Upwelling Systems adjacent to tropical Oxygen Minimum Zones (OMZs). We track cyclonic and anticyclonic eddies with a surface signature over the period 1992–2018 and isolate their subsurface oxygen characteristics. We identify strongly deoxygenating eddies and quantify their contribution to low [O2] extreme events. Our results show that model simulated low [O2] extreme event frequency is 2–7 times higher in eddies versus non-eddying locations, with regionally more than half of low [O2] extreme events outside of the permanent OMZs being associated with eddies. Our study highlights the need for further work to investigate the drivers, characteristics and potential ecosystem impacts of low [O2] extreme events.
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  • 6
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    Constraining the Particle Size Distribution of Large Marine Particles in the Global Ocean With In Situ Optical Observations and Supervised Learning (2022)
    AGU
    Details
    Publication Date: 2024-02-07
    Description: The abundance and size distribution of marine particles control a range of biogeochemical and ecological processes in the ocean, including carbon sequestration. These quantities are the result of complex physical-biological interactions that are difficult to observe, and their spatial and temporal patterns remain uncertain. Here, we present a novel analysis of particle size distributions (PSDs) from a global compilation of in situ Underwater Vision Profiler 5 (UVP5) optical measurements. Using a machine learning algorithm, we extrapolate sparse UVP5 observations to the global ocean from well-sampled oceanographic variables. We reconstruct global maps of PSD parameters (biovolume [BV] and slope) for particles at the base of the euphotic zone. These reconstructions reveal consistent global patterns, with high chlorophyll regions generally characterized by high particle BV and flatter PSD slope, that is, a high relative abundance of large versus small particles. The resulting negative correlations between particle BV and slope further suggests synergistic effects on size-dependent processes such as sinking particle fluxes. Our approach and estimates provide a baseline for an improved understanding of particle cycles in the ocean, and pave the way to global, three-dimensional reconstructions of PSD and sinking particle fluxes from the growing body of UVP5 observations.
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  • 7
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    Turbulent Mixing and the Formation of an Intermediate Nepheloid Layer Above the Siberian Continental Shelf Break (2021)
    AGU | Wiley
    Details
    Publication Date: 2024-02-07
    Description: Intermediate nepheloid layers (INLs) form important pathways for the cross-slope transport and vertical export of particulate matter, including carbon. While intermediate maxima in particle settling fluxes have been reported in the Eurasian Basin of the Arctic Ocean, direct observations of turbid INLs above the continental slope are still lacking. In this study, we provide the first direct evidence of an INL, coinciding with enhanced mid-water turbulent dissipation rates, over the Laptev Sea continental slope in summer 2018. Current velocity data show a period of enhanced downslope flow with depressed isopcynals, suggesting that the enhanced turbulent dissipation is probably the consequence of the presence of an unsteady lee wave. Similar events occur mostly during ice free periods, suggesting an increasing frequency of episodic cross-slope particle transport in the future. The discovery of the INL and the episodic generation mechanism provide new insights into particle transport dynamics in this rapidly changing environment.
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  • 8
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    Origin and transformation of light hydrocarbons ascending at an active pockmark on Vestnesa Ridge, Arctic Ocean (2020)
    AGU | Wiley
    Details
    Publication Date: 2023-02-08
    Description: We report on the geochemistry of hydrocarbons and pore waters down to 62.5 mbsf, collected by drilling with the MARUM‐MeBo70 and by gravity coring at the Lunde pockmark in the Vestnesa Ridge. Our data document the origin and transformations of volatiles feeding gas emissions previously documented in this region. Gas hydrates are present where a fracture network beneath the pockmark focusses migration of thermogenic hydrocarbons characterized by their C1/C2+ and stable isotopic compositions (δ2H‐CH4, δ13C‐CH4). Measured geothermal gradients (~80°C km‐1) and known formation temperatures (〉70°C) suggest that those hydrocarbons are formed at depths 〉800 mbsf. A combined analytical/modeling approach, including concentration and isotopic mass balances, reveals that pockmark sediments experience diffuse migration of thermogenic hydrocarbons. However, at sites without channeled flow this appears to be limited to depths 〉 ~50 mbsf. At all sites we document a contribution of microbial methanogenesis to the overall carbon cycle that includes a component of secondary carbonate reduction (CR) – i.e. reduction of dissolved inorganic carbon (DIC) generated by anaerobic oxidation of methane (AOM) in the uppermost methanogenic zone. AOM and CR rates are spatially variable within the pockmark and are highest at high‐flux sites. These reactions are revealed by δ13C‐DIC depletions at the sulfate‐methane interface at all sites. However, δ13C‐CH4 depletions are only observed at the low methane flux sites because changes in the isotopic composition of the overall methane pool are masked at high‐flux sites. 13C‐depletions of TOC suggest that at seeps sites, methane‐derived carbon is incorporated into de novo synthesized biomass.
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  • 9
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    Intensification of Near‐Surface Currents and Shear in the Eastern Arctic Ocean (2020)
    AGU | Wiley
    Details
    Publication Date: 2023-02-08
    Description: A 15-year (2004–2018) record of mooring observations from the upper 50 m of the ocean in the eastern Eurasian Basin reveals increased current speeds and vertical shear, associated with an increasing coupling between wind, ice, and the upper ocean over 2004–2018, particularly in summer. Substantial increases in current speeds and shears in the upper 50 m are dominated by a two times amplification of currents in the semidiurnal band, which includes tides and wind-forced near-inertial oscillations. For the first time the strengthened upper ocean currents and shear are observed to coincide with weakening stratification. This coupling links the Atlantic Water heat to the sea ice, a consequence of which would be reducing regional sea ice volume. These results point to a new positive feedback mechanism in which reduced sea ice extent facilitates more energetic inertial oscillations and associated upper-ocean shear, thus leading to enhanced ventilation of the Atlantic Water.
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  • 10
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    Interplay of subduction tectonics, sedimentation, and carbon cycling (2019)
    AGU | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 20 (11). pp. 4939-4955.
    Details
    Publication Date: 2022-01-31
    Description: Distinct differences were observed in geochemical signatures in sediments from two sites drilled in the upper plate of the Costa Rica margin during Integrated Ocean Drilling Program (IODP) Expedition 334. The upper 80 m at Site U1379, located on the outer shelf, show pore water non‐steady state conditions characteristic of a declining methane flux. These contrast with analyses of the upper sediment layers at the middle slope site (U1378) that reflect steady state conditions. Distinct carbonate‐rich horizons up to 11 meters thick were recovered between 63 and 310 meters below seafloor at Site U1379 but were not found at Site U1378. The carbonates and dissolved inorganic carbon from Site U1379 have a depleted carbon stable isotope signal (up to ‐25‰) that indicates anaerobic methane oxidation. This inference is further supported by distinct δ34S‐pyrite and magnetic susceptibility records that reveal fluctuations of the sulfate‐methane transition in response to methane flux variations. Tectonic reconstructions of this margin document a marked subsidence event after arrival of the Cocos Ridge, 2.2 ± 0.2 million years ago (Ma), followed by increased sedimentation rates and uplift. As the seafloor at Site U1379 rose from ~2000 m to the present water depth of ~126 m, the site moved out of the gas hydrate stability zone (GHSZ) at ~1.1 Ma, triggering upward methane advection, methane oxidation, and the onset of massive carbonate formation. Younger carbonate occurrences and the non‐steady state pore profiles at Site U1379 reflect continued episodic venting likely modulated by changes in the underlying methane reservoir.
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  • 11
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    Polar Low Workshop (2019)
    American Meteorological Society
    In:  Bulletin of the American Meteorological Society, 100 (2). ES89-ES92.
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    Publication Date: 2022-01-31
    Description: The workshop on polar lows (PLs) and mesoscale weather extremes attracted 30 scientists from China, France, Germany, Japan, Norway, Russia, the United Kingdom, and the United States to present the most recent findings on PL research and to summarize our present understanding of PLs and mesocyclones (MCs) as well as mesoscale weather extremes in the Arctic and Antarctic (see sidebar for the definition of PLs). The workshop had the following main themes: PL studies using satellite data and in situ observations, climatological aspects, PLs in reanalyses and model simulations, environments for PL genesis and operational aspects, polar mesoscale weather phenomena, and air–ocean–ice interactions. The workshop was concluded by a roundtable discussion resulting in recommendations for future research and actions.
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  • 12
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    CO2 Release from Pockmarks on the Chatham Rise‐Bounty Trough at the Glacial Termination (2019)
    AGU | Wiley
    In:  Paleoceanography and Paleoclimatology, 34 (11). pp. 1726-1743.
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    Publication Date: 2022-01-31
    Description: Seafloor pockmarks of varying size occur over an area of 50,000 km2 on the Chatham Rise, Canterbury Shelf and Inner Bounty Trough, New Zealand. The pockmarks are concentrated above the flat‐subducted Hikurangi Plateau. Echosounder data identifies recurrent episodes of pockmark formation at ~100,000yr frequency coinciding with Pleistocene glacial terminations. Here we show that there are structural conduits beneath the larger pockmarks through which fluids flowed upward toward the seafloor. Large negative Δ14C excursions are documented in marine sediments deposited next to these subseafloor conduits and pockmarks at the last glacial termination. Modern pore waters contain no methane and there is no negative δ13C excursion at the glacial termination that would be indicative of methane or mantle‐derived carbon at the time the Δ14C excursion and pockmarks were produced. An ocean general circulation model equipped with isotope tracers is unable to simulate these large Δ14C excursions on the Chatham Rise by transport of hydrothermal carbon released from the East Pacific Rise as previous studies suggested. Here we attribute the Δ14C anomalies and pockmarks to release of 14C‐dead CO2 and carbon‐rich fluids from subsurface reservoirs, the most likely being dissociated Mesozoic carbonates that subducted beneath the Rise during the Late Cretaceous. Because of the large number of pockmarks and duration of the Δ14C anomaly, the pockmarks may collectively represent an important source of 14C‐dead carbon to the ocean during glacial terminations.
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  • 13
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    Influence of Ocean Circulation and Benthic Exchange on Deep Northwest Atlantic Nd Isotope Records During the Past 30,000 Years (2019)
    AGU
    In:  Geochemistry, Geophysics, Geosystems, 20 (9). pp. 4457-4469.
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    Publication Date: 2022-01-31
    Description: Neodymium (Nd) isotopes extracted from authigenic sediment phases are increasingly used as a proxy for past variations in water mass provenance. To better constrain the controls of water mass provenance and nonconservative effects on the archived Nd isotope signal, we present a new depth transect of Nd isotope reconstructions from the Blake Bahama Outer Ridge along the North American continental margin covering the past 30 ka. We investigated five sediment cores that lie directly within the main flow path of the Deep Western Boundary Current, a major advection route of North Atlantic Deep Water. We found offsets between core tops and seawater Nd isotopic compositions that are observed elsewhere in the Northwest Atlantic. A possible explanation for this is the earlier suggested redistribution of sediment by nepheloid layers at intermediate as well as abyssal depths, transporting material downslope and along the continental margin. These processes potentially contributed to Nd isotope excursions recorded in Northwest Atlantic sediment cores during the Bølling-Allerød and early Holocene. An Atlantic-wide comparison of Nd isotope records shows that the early Holocene excursions had an additional contribution from conservative advection of unradiogenic dissolved Nd. Nevertheless, the trends of the Nd isotope records are in general agreement with previous reconstructions of water mass provenance from the entire Atlantic and also reveal millennial-scale changes during the last deglaciation in temporal high resolution, which have rarely been reported before. Further, the new records confirm that during cold periods the Northwest Atlantic was bathed by an increased contribution of southern sourced water.
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  • 14
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    Chlorophyll a reconstruction from in situ measurements: 2. Marked carbon uptake decrease in the last century (2015)
    AGU
    In:  Journal of Geophysical Research: Biogeosciences, 120 (2). pp. 246-253.
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    Publication Date: 2020-07-23
    Description: A chlorophyll a hindcast in the Madeira Basin from 1871 to 2008 was used to analyze the long-term variability in the oligotrophic, subtropical gyres in relation to the climate change of the last century. The deep chlorophyll maximum (DCM), as dominant pattern of the chlorophyll a field, showed a fast decrease in its strength in the 1940s. An absolute minimum was reached between 1967 and 1973 when no DCM established with a recovering to the end of the time series. Long-term variability of the DCM was related to the North Atlantic Oscillation with a time delay of 9 years. The marked decrease in the 1940s was correlated to the drop of the solar radiation in transition from early brightening to global dimming. Caused by the influence of the solar radiation and maybe related to increasing global temperatures in the last century, the integrated chlorophyll a concentration decreased by about 0.7 mg m−2 in 2008 compared to 1871. The high-resolved chlorophyll a hindcast allowed an estimation of the carbon uptake by the ocean due to primary production in the euphotic zone. A rough calculation over the area of the global subtropical oceans showed 700 megaton less carbon uptake in 2008.
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  • 15
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    Discontinuous Daily Temperatures in the WATCH Forcing Datasets (2015)
    American Meteorological Society
    In:  Journal of Hydrometeorology, 16 (1). pp. 465-472.
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    Publication Date: 2020-07-23
    Description: The Water and Global Change (WATCH) forcing datasets have been created to support the use of hydrological and land surface models for the assessment of the water cycle within climate change studies. They are based on 40-yr ECMWF Re-Analysis (ERA-40) or ECMWF interim reanalysis (ERA-Interim) with temperatures (among other variables) adjusted such that their monthly means match the monthly temperature dataset from the Climatic Research Unit. To this end, daily minimum, maximum, and mean temperatures within one calendar month have been subjected to a correction involving monthly means of the respective month. As these corrections can be largely different for adjacent months, this procedure potentially leads to implausible differences in daily temperatures across the boundaries of calendar months. We analyze day-to-day temperature fluctuations within and across months and find that across-months differences are significantly larger, mostly in the tropics and frigid zones. Average across-months differences in daily mean temperature are typically between 10% and 40% larger than their corresponding within-months average temperature differences. However, regions with differences up to 200% can be found in tropical Africa. Particularly in regions where snowmelt is a relevant player for hydrology, a few degrees Celsius difference can be decisive for triggering this process. Daily maximum and minimum temperatures are affected in the same regions, but in a less severe way.
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  • 16
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    Chlorophyll a reconstruction from in situ measurements: 1. Method description (2015)
    AGU
    In:  Journal of Geophysical Research: Biogeosciences, 120 (2). pp. 237-245.
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    Publication Date: 2020-07-23
    Description: Understanding the development of primary production is essential for projections of the global carbon cycle in the context of climate change. A chlorophyll a hindcast that serves as a primary production indicator was obtained by fitting in situ measurements of nitrate, chlorophyll a, and temperature. The resulting fitting functions were adapted to a modeled temperature field. The method was applied to observations from the Madeira Basin, in the northeastern part of the oligotrophic North Atlantic Subtropical Gyre and yielded a chlorophyll a field from 1989 to 2008 with a monthly resolution validated with remotely measured surface chlorophyll a data by SeaWiFS. The chlorophyll a hindcast determined with our method resolved the seasonal and interannual variability in the phytoplankton biomass of the euphotic zone as well as the deep chlorophyll maximum. Moreover, it will allow estimation of carbon uptake over long time scales.
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  • 17
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    Constraints on fluid flow processes in the Hellenic Accretionary Complex (eastern Mediterranean Sea) from numerical modeling (2014)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 119 (4). pp. 3601-3626.
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    Publication Date: 2020-07-23
    Description: The dynamics of accretionary convergent margins are severely influenced by intense deformation and fluid expulsion. To quantify the fluid pressure and fluid flow velocities in the Hellenic subduction system, we set up 2-D hydrogeological numerical models following two seismic reflection lines across the Mediterranean Ridge. These profiles bracket the along-strike variation in wedge geometry: moderate compression and a 〉4 km thick underthrust sequence in the west versus enhanced compression and 〈1 km of downgoing sediment in the center. Input parameters were obtained from preexisting geophysical data, drill cores, and new geotechnical laboratory experiments. A permeability-porosity relationship was determined by a sensitivity analysis, indicating that porosity and intrinsic permeability are small. This hampers the expulsion of fluids and leads to the build up of fluid overpressure in the deeper portion of the wedge and in the underthrust sediment. The loci of maximum fluid pressure are mainly controlled by the compactional fluid source, which generally decreases toward the backstop. However, pore pressure is still high at the decollement level at distances 〈100 km from the deformation front, either by the incorporation of low permeability evaporites or additional compaction of the wedge sediments in the two profiles. In the west, however, formation of a wide accretionary complex is facilitated by high pore pressure zones. When compared to other large accretionary complexes such as Nankai or Barbados, our results not only show broad similarities but also that near-lithostatic pore pressures may be easier to maintain in the Hellenic Arc because of accentuated collision, some underthrust evaporates, and a thicker underthrust sequence.
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  • 18
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    Structure and variability of the abyssal water masses in the Ionian Sea in the period 2003-2010 (2013)
    AGU
    In:  Journal of Geophysical Research: Oceans, 118 (2). pp. 931-943.
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    Publication Date: 2020-07-23
    Description: This study presents aspects of the spatial and temporal variability of abyssal water masses in the Ionian Sea, as derived from recent temperature, salinity, dissolved oxygen and velocity observations and from comparisons between these and former observations. Previous studies showed how in the Southern Adriatic Sea the Adriatic Deep Water (AdDW) became fresher (ΔS ≈ −0.08) and colder (ΔT ≈ −0.1°C) after experiencing warming and salinification between 2003 and 2007. Our data, collected from October 2009 to July 2010 from two bottom moorings, one within the Strait of Otranto and the other in the northern Ionian, confirm this tendency: a bottom vein of southward-flowing AdDW, whose temperature and salinity continuously decreased during the observation time, was detected there. Typically, the vein travel time between the two stations ranged between 45 and 50 days. This gave us a temporal estimate for AdDW anomaly propagation towards the Ionian abyss from their Adriatic generation region. The density excess of the observed vein was always enough to enable its existence as a bottom-arrested current. This evidence confirms that, at that time (2009 and 2010), the Adriatic Sea was greatly contributing to the formation of Eastern Mediterranean Deep Water (EMDW), the bottom water of the Eastern Mediterranean. Hence, based on these results and on the evidence that, from 2003 to 2009, abyssal Ionian waters became saltier and warmer under the time-lagged influence of AdDW, possible future changes in the EMDW characteristics, as a response to Adriatic variability, are discussed.
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  • 19
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    A Comparative Stability Analysis of Atlantic and Pacific Nino Modes (2013)
    American Meteorological Society
    In:  Journal of Climate, 26 (16). pp. 5965-5980.
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    Publication Date: 2020-07-24
    Description: El Niño–Southern Oscillation (ENSO) in the Pacific and the analogous Atlantic Niño mode are generated by processes involving coupled ocean–atmosphere interactions known as the Bjerknes feedback. It has been argued that the Atlantic Niño mode is more strongly damped than ENSO, which is presumed to be closer to neutrally stable. In this study the stability of ENSO and the Atlantic Niño mode is compared via an analysis of the Bjerknes stability index. This index is based on recharge oscillator theory and can be interpreted as the growth rate for coupled modes of ocean–atmosphere variability. Using observational data, an ocean reanalysis product, and output from an ocean general circulation model, the individual terms of the Bjerknes index are calculated for the first time for the Atlantic and then compared to results for the Pacific. Positive thermocline feedbacks in response to wind stress forcing favor anomaly growth in both basins, but they are twice as large in the Pacific compared to the Atlantic. Thermocline feedback is related to the fetch of the zonal winds, which is much greater in the equatorial Pacific than in the equatorial Atlantic due to larger basin size. Negative feedbacks are dominated by thermal damping of sea surface temperature anomalies in both basins. Overall, it is found that both ENSO and the Atlantic Niño mode are damped oscillators, but the Atlantic is more strongly damped than the Pacific primarily because of the weaker thermocline feedback.
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  • 20
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    MIMOC: A global monthly isopycnal upper-ocean climatology with mixed layers (2013)
    AGU
    In:  Journal of Geophysical Research: Oceans, 118 (4). pp. 1658-1672.
    Details
    Publication Date: 2020-07-23
    Description: A monthly, isopycnal/mixed-layer ocean climatology (MIMOC), global from 0 to 1950 dbar, is compared with other monthly ocean climatologies. All available quality-controlled profiles of temperature (T) and salinity (S) versus pressure (P) collected by conductivity-temperature-depth (CTD) instruments from the Argo Program, Ice-Tethered Profilers, and archived in the World Ocean Database are used. MIMOC provides maps of mixed layer properties (conservative temperature, Θ, absolute salinity, SA, and maximum P) as well as maps of interior ocean properties (Θ, SA, and P) to 1950 dbar on isopycnal surfaces. A third product merges the two onto a pressure grid spanning the upper 1950 dbar, adding more familiar potential temperature (θ) and practical salinity (S) maps. All maps are at monthly 0.5° × 0.5° resolution, spanning from 80°S to 90°N. Objective mapping routines used and described here incorporate an isobath-following component using a “Fast Marching” algorithm, as well as front-sharpening components in both the mixed layer and on interior isopycnals. Recent data are emphasized in the mapping. The goal is to compute a climatology that looks as much as possible like synoptic surveys sampled circa 2007–2011 during all phases of the seasonal cycle, minimizing transient eddy and wave signatures. MIMOC preserves a surface mixed layer, minimizes both diapycnal and isopycnal smoothing of θ-S, as well as preserves density structure in the vertical (pycnoclines and pycnostads) and the horizontal (fronts and their associated currents). It is statically stable and resolves water mass features, fronts, and currents with a high level of detail and fidelity.
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  • 21
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    Mechanical aspects of postglacial volcanism and tectonics of the Reykjanes Peninsula, southwest Iceland (2012)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 91 (B12). pp. 12711-12721.
    Details
    Publication Date: 2020-07-23
    Description: Four major NE trending postglacial volcanic and tectonic fissure swarms (volcanic systems) occur on the Reykjanes Peninsula, and the westernmost three are the main subject of this paper. Two main types of basaltic volcanoes are associated with these systems: shields of picrite and olivine tholeiite and tholeiite fissures. The average volume of 26 shields is 1.11 km3, and the total production is 29 km3, whereas the corresponding figures for lavas from 101 volcanic fissures are 0.11 km3 and 11 km3. The tectonic fractures are either tension fractures or normal faults of widths up to 20 m, throws up to 10 m, and lengths up to several kilometers. The volcanism and tectonics can be explained by magmatic pressure changes in ellipsoidal magma reservoirs located beneath the fissure swarms. A magmatic pressure increase of the order of 10 MPa is found to be sufficient for an excess uplift of the order of several meters, which is all that is needed to account for the fractures and measured dilation in the fissure swarms. It is concluded that most shield volcanoes, in particular the picrite shields and the large olivine tholeiite shields, formed during the early postglacial period and that their formation was facilitated by the stress field generated as a result of rapid uplift and bending of the crust above the reservoirs. Since that time the reservoirs have become independent systems, the volcanism has been confined to fissures, and the production rate has decreased significantly. During typical fissure eruptions (0.015 km3), only the uppermost several hundred meters of the source reservoir, depending on its magma content, supply magma to the eruption.
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  • 22
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    Variability of the Denmark Strait overflow: Moored time series from 1996–2011 (2012)
    AGU
    In:  Journal of Geophysical Research: Oceans, 117 (C12). C12003.
    Details
    Publication Date: 2020-07-23
    Description: The Denmark Strait overflow provides about half of the total dense water overflow from the Nordic Seas into the North Atlantic Ocean. The velocity of the overflow has been monitored in the Strait with two moored Acoustic Doppler Current Profilers since 1996 with several interruptions due to mooring losses or instrument failure. So far, overflow transports were only calculated when data from both moorings were available. In this work, we introduce a linear model to fill gaps in the time series when data from only one instrument is available. The mean overflow transport is 3.4 Sv and exhibits a variance of 2.0 Sv2. No significant trend was detected in the time series. The highest variability in the transport is associated with the passage of mesoscale eddies with time scales of 2–10 days (associated with a variance of 1.5 Sv2). Seasonal variability is weak and explains less than 5% of the variance in all time series, which is in contrast to the strong seasonal cycle found in high resolution model simulations. Interannual variability is on the order of 10% of the mean. A relation to atmospheric forcing such as the local wind stress curl, as well as to larger scale phenomena, e.g. the North Atlantic Oscillation, is not detected. Since 2005 data from moored temperature, conductivity and pressure recorders have been available as well, monitoring the hydrographic variability at the bottom of Denmark Strait. In recent years the temperature time series of the Denmark Strait overflow revealed a cooling, while the salinity stayed nearly constant.
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  • 23
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    Observed and modeled surface eddy heat fluxes in the eastern Nordic Seas (2012)
    AGU
    In:  Journal of Geophysical Research: Oceans, 117 (C8).
    Details
    Publication Date: 2020-07-23
    Description: Large-scale budget calculations and numerical model process studies suggest that lateral eddy heat fluxes have an important cooling effect on the Norwegian Atlantic Current (NwAC) as it flows through the Nordic Seas. But observational estimates of such fluxes have been lacking. Here, wintertime surface eddy heat fluxes in the eastern Nordic Seas are estimated from surface drifter data, satellite data and an eddy-permitting numerical model. Maps of the eddy heat flux divergence suggest advective cooling along the path of the NwAC. Integrating the flux divergence over temperature classes yields consistent estimates for the three data sets; the waters warmer than about 6°C are cooled while the cooler waters are warmed. Similar integrations over bottom depth classes show that regions shallower than about 2000 m are cooled while deeper regions are warmed. Finally, integrating the flux divergence along the core of the NwAC suggests that the highest eddy-induced heat loss at the surface is along the steepest part of the continental slope, east of the Lofoten Basin. The model fields indicate that cooling of the current by lateral eddy fluxes is comparable to or larger than the local heat loss to the atmosphere.
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  • 24
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    Structure and seismogenic properties of the Mentawai segment of the Sumatra subduction zone revealed by local earthquake traveltime tomography (2012)
    AGU
    In:  Journal of Geophysical Research: Oceans, 117 (B1). B01312.
    Details
    Publication Date: 2020-07-23
    Description: On 12 September 2007, an Mw8.4 earthquake occurred within the southern section of the Mentawai segment of the Sumatra subduction zone, where the subduction thrust had previously ruptured in 1833 and 1797. Traveltime data obtained from a temporary local seismic network, deployed between December 2007 and October 2008 to record the aftershocks of the 2007 event, was used to determine two-dimensional (2-D) and three-dimensional (3-D) velocity models of the Mentawai segment. The seismicity distribution reveals significant activity along the subduction interface and within two clusters in the overriding plate either side of the forearc basin. The downgoing slab is clearly distinguished by a dipping region of highVp (8.0 km/s), which can be a traced to ∼50 km depth, with an increased Vp/Vs ratio (1.75 to 1.90) beneath the islands and the western side of the forearc basin, suggesting hydrated oceanic crust. Above the slab, a shallow continental Moho of less than 30 km depth can be inferred, suggesting that the intersection of the continental mantle with the subducting slab is much shallower than the downdip limit of the seismogenic zone despite localized serpentinization being present at the toe of the mantle wedge. The outer arc islands are characterized by low Vp (4.5–5.8 km/s) and high Vp/Vs (greater than 2.0), suggesting that they consist of fluid saturated sediments. The very low rigidity of the outer forearc contributed to the slow rupture of the Mw 7.7 Mentawai tsunami earthquake on 25 October 2010.
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  • 25
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    Young mafic back arc volcanic rocks as indicators of continental lithospheric delamination beneath the Argentine Puna Plateau, central Andes (2012)
    AGU
    In:  Journal of Geophysical Research: Oceans, 99 (B12). pp. 24323-24339.
    Details
    Publication Date: 2020-07-23
    Description: The spatial distribution of some major and trace element and isotopic characteristics of backarc Plio-Quaternary basaltic to high-Mg andesitic (51% to 58% SiO2) lavas in the southern Puna (24°S to 27°S) of the Central Andean Volcanic Zone (CVZ) reflect varying continental lithospheric thickness and the thermal state of the underlying mantle wedge and subducting plate. These lavas erupted from small cones and fissures associated with faults related to a change in the regional stress system in the southern Puna at ≈ 2 to 3 Ma. Three geochemical groups are recognized: (1) a relatively high volume intraplate group (high K; La/Ta ratio 〈25) that occurs over a thin continental lithosphere above a gap in the modern seismic zone and represents the highest percentage of mantle partial melt, (2) an intermediate volume, high-K calc-alkaline group ( La/Ta ratio 〉25) that occurs over intermediate thickness lithosphere on the margins of the seismic gap and behind the main CVZ and represents an intermediate percentage of mantle partial melt, and (3) a small-volume shoshonitic group (very high K) that occurs over relatively thick continental lithosphere in the northeast Puna and Altiplano and represents a very small percentage of mantle partial melt. Mantle-generated characteristics of these lavas are partially overprinted by mixing with melts of the overlying thickened crust as shown by the presence of quartz and feldspar xenocrysts, negative Eu anomalies (Eu/Eu 〈 0.90; most 〈 0.80), and radiogenic Sr (〉 0.7055) and Pb and nonradiogenic Nd ( εNd 〈 −0.4) isotopic ratios. Mixing calculations show that the lavas generally contain more than 20% to 25% crustal melt. The eruption of the intraplate group mafic lavas, the change in regional stress orientation, and the high elevation of the southern Puna are suggested to be the result of the late Pliocene mechanical delamination of a block (or blocks) of continental lithosphere (mantle and possibly lowermost crust). The loss of this lithosphere resulted in an influx of asthenosphere that caused heating of the subducting slab and yielded intraplate basic magmas that produced extensive melting at the base of the thickened crust. Heating of the subducting slab led to formation of the seismic gap and trenchward depletion of the slab component. Backarc calc-alkaline group lavas erupted on the margins of this delaminated block, whereas shoshonitic group lavas erupted over a zone of relatively thick nondelaminated lithosphere to the north.
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    Marine geology of the Hess Rise: 1. Bathymetry, surface sediment distribution, and environment of deposition (2012)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 86 (B11). pp. 10734-10752.
    Details
    Publication Date: 2020-07-23
    Description: New charts of bathymetry, acoustic character, and sediment distribution describe the Hess Rise, a large oceanic plateau in the central north Pacific. Discrete physiographic provinces on the Hess Rise are the High Plateau, shallower than 3900 m, trending N30°W; the Northeastern Flank, a smooth, gentle slope gradually increasing in depth to the northeast; the Woollard Abyssal Plain, extending farther to the northeast; the Volcanic Province with its high peaks and ridges along the southern margin of the Hess Rise; the Mendocino Fracture Zone to the south, expressed by broad, planar seafloor regions bordered by ridges and scarps; the Western Steps, formed by structural benches on the western side of the Rise; and the Emperor Deep, between the rise and the Emperor Seamounts. Five types of acoustic units have been mapped and interpreted: a transparent layer, predominantly of biosiliceous pelagic clay; a stratified layer, predominantly of nannofossil ooze; a diffuse layer of debris flows that seem to have originated mostly in the Volcanic Province; an opaque horizon commonly formed of volcaniclastic sediments that are usually found on the seafloor of the Mendocino Fracture Zone; and a hyperbolic horizon, indicating outcrops of igneous rock. The pronounced effect of bottom currents on the present-day environment of deposition in the Hess Rise is evidenced by the presence of the opaque horizon, which is interpreted as an erosion surface, and by current moating, abrupt thinning of surface layers and truncation of subbottom reflectors. The widespread erosion on the seafloor of the Mendocino Fracture Zone is attributed to the flow of Antarctic bottom water.
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  • 27
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    Mapping the fluid flow of the Mariana Mounds ridge flank hydrothermal system: Pore water chemical tracers (2012)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 100 (B5). pp. 8115-8131.
    Details
    Publication Date: 2020-07-23
    Description: We present a conceptual model of fluid circulation in a ridge flank hydrothermal system, the Mariana Mounds. The model is based on chemical data from pore waters extracted from piston cores and from push cores collected by deep‐sea research vessel Alvin in small, meter‐sized mounds situated on a local topographic high. These mounds are located within a region of heat flow exceeding that calculated from a conductive model and are zones of strong pore water upflow. We have interpreted the chemical data with time‐dependent transport‐reaction models to estimate pore water velocities. In the mounds themselves pore water velocities reach several meters per year to kilometers per year. Within about 100 m from these zones of focused upflow velocities decrease to several centimeters per year up to tens of centimeters per year. A larger area of low heat flow surrounds these heat flow and topographic highs, with upwelling pore water velocities less than 2 cm/yr. In some nearby cores, downwelling of bottom seawater is evident but at speeds less than 2 cm/yr. Downwelling through the sediments appears to be a minor source of seawater recharge to the basaltic basement. We conclude that the principal source of seawater recharge to basement is where basement outcrops exist, most likely a scarp about 2–4 km to the east and southeast of the study area.
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    Precipitation downscaling under climate change: Recent developments to bridge the gap between dynamical models and the end user (2010)
    AGU
    In:  Reviews of Geophysics, 48 (3). RG3003.
    Details
    Publication Date: 2020-06-03
    Description: Precipitation downscaling improves the coarse resolution and poor representation of precipitation in global climate models and helps end users to assess the likely hydrological impacts of climate change. This paper integrates perspectives from meteorologists, climatologists, statisticians, and hydrologists to identify generic end user (in particular, impact modeler) needs and to discuss downscaling capabilities and gaps. End users need a reliable representation of precipitation intensities and temporal and spatial variability, as well as physical consistency, independent of region and season. In addition to presenting dynamical downscaling, we review perfect prognosis statistical downscaling, model output statistics, and weather generators, focusing on recent developments to improve the representation of space-time variability. Furthermore, evaluation techniques to assess downscaling skill are presented. Downscaling adds considerable value to projections from global climate models. Remaining gaps are uncertainties arising from sparse data; representation of extreme summer precipitation, subdaily precipitation, and full precipitation fields on fine scales; capturing changes in small-scale processes and their feedback on large scales; and errors inherited from the driving global climate model.
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  • 29
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    Response of the eastern subtropical Atlantic SST to Saharan dust: A modeling and observational study (2010)
    AGU
    In:  Journal of Geophysical Research: Oceans, 115 (C8).
    Details
    Publication Date: 2020-07-23
    Description: Retrievals of aerosol optical depth (AOD) from MODIS, and of sea surface temperature (SST) from TMI are analyzed jointly with the output of a numerical model for the period 2000-2006 to determine the impact of Saharan dust on the eastern subtropical North Atlantic SST. Simultaneously with, or shortly after strong dust outbreaks, a decrease in SST of 0.2 degrees to 0.4 degrees C can be observed in the microwave SST data set, which is consistent with an independent estimate of SST decrease simulated here by a local mixed layer model. However, low wind conditions and a shallow mixed layer are required to reach this response, and it is therefore unlikely that a clear response of SST to dust lasting more than a few days can be seen in the microwave SST observations. An inspection of microwave SST observations suggests that about 30% of SST variance could be explained by dust-induced cooling in our study region that is not represented in existing AVHRR SST fields nor represented in reanalysis centers-provided surface heat fluxes. On longer time scales, a comparison between observed SST fields and simulated SST, using an eddy-permitting model of the North Atlantic, suggests a cooling of about 0.5 degrees C on the local SST on sub-seasonal to interannual time scales which is significantly correlated and consistent with a dust-induced cooling. However, while supportive of the hypothesis that Saharan dust lead to a reduction in SST, the eddy-resolving model results are not by themselves conclusive. Moreover, the effects of dust-induced cooling on simulations of the ocean circulation, on atmospheric forecasts and on climate simulations remains to be investigated in future studies.
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  • 30
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    Dynamics of wind-forced coherent anticyclones in the open ocean (2009)
    AGU
    In:  Journal of Geophysical Research, 114 (C8).
    Details
    Publication Date: 2020-07-23
    Description: We numerically study the dynamics of coherent anticyclonic eddies in the ocean interior. For the hydrostatic, rotating, stably stratified turbulence we use a high-resolution primitive equation model forced by small-scale winds in an idealized configuration. Many properties of the horizontal motions are found to be similar to those of two-dimensional and quasi-geostrophic turbulence. Major differences are a strong cyclone-anticyclone asymmetry linked to the straining field exerted by vortex Rossby waves, which is also found in shallow water flows, and the complex structure of the vertical velocity field, which we analyze in detail. Locally, the motion can become strongly ageostrophic, and vertical velocities associated with vortices can reach magnitudes and levels of spatial complexity akin to those reported for frontal regions. Transport and mixing properties of the flow field are further investigated by analyzing Lagrangian trajectories. Particles released in the pycnocline undergo large vertical excursions because of the vertical velocities associated to the vortices, with potentially important consequences for marine ecosystem dynamics.
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    Nitrate isotope anomalies reflect N2fixation in the Azores Front region (subtropical NE Atlantic) (2009)
    AGU
    In:  Journal of Geophysical Research: Oceans, 114 (C3). C03003.
    Details
    Publication Date: 2020-07-23
    Description: The subtropical northeast Atlantic has previously been identified as a marine environment with an apparent imbalance between low nitrate supply to the surface and concurrent high export production. To better constrain the sources and fluxes of mixed layer nitrate and to assess the potential role of N2 fixation in providing new nitrogen (N), we investigated the depth distribution of nitrate δ15N and δ18O at six stations across the Azores Front in the NE Atlantic. In addition, we measured the δ15N of dissolved organic N (DON) in surface waters and of sinking particulate N collected in sediment traps at 2000 m depth between 2003 and 2005 at Station KIEL276. The nitrate isotope profiles at the majority of the hydrographic stations displayed a decrease in the δ15N from depth toward low-nitrate surface waters, concomitant with an increase in δ18O. Given that nitrate uptake by phytoplankton leads to a proportional increase in nitrate δ15N and δ18O, the observed surface water nitrate isotope anomalies (Δ(15;18) up to −6‰) indicate that nitrate assimilation is not the sole process controlling the isotopic composition of nitrate in the photic zone and implicate a significant addition of newly fixed N that is remineralized in surface and subsurface waters. Both the concentration of DON and its δ15N in surface water were spatially invariant, showing mean values of 4.7 ± 0.5 μmol L−1 and 2.6 ± 0.4‰ (n = 35), respectively, supporting the conjecture of a mostly recalcitrant DON pool. The weighted biannual mean δ15N of sinking particulate N (1.8 ± 0.8‰, n = 33) was low with respect to thermocline nitrate. The anomalous dual nitrate isotope signatures together with the low δ15N of export production and elevated nitrate-to-phosphate ratios in surface and subsurface waters strongly suggest that N2 fixation represents a substantive source of N in this part of the subtropical northeast Atlantic. Simple isotope mass balance suggests that, locally, N2 fixation supplies between 56 and 259 mmol N m−2 a−1 for phytoplankton growth in the photic zone, accounting for up to ∼40% of the estimated export production.
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    Lithospheric geometry of the Wopmay orogen from a Slave craton to Bear Province magnetotelluric transect (2009)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 114 (B1). B01101.
    Details
    Publication Date: 2020-07-23
    Description: Two‐dimensional inversions of lithospheric‐probing magnetotelluric (MT) data at a total of 20 sites acquired along an approximately east–west 300‐km‐long profile across the Wopmay orogen in the Northwest Territories, Canada, provide electrical resistivity models of the boundary between the Archean Slave craton and the adjacent Proterozoic Bear Province. An analysis of distortion effects and structural dimensionality indicates that the MT responses are primarily one‐dimensional or only weakly two‐dimensional with a depth‐independent geoelectric strike angle of N32°E, consistent with regional structural geology. The regional‐scale model, generated from the longer period responses from all of the sites along the profile, reveals significant lateral variations in the lithospheric mantle. Resistive cratonic roots are imaged to depths of ∼200 km beneath both the Slave craton and the Hottah terrane of the Bear Province. These are separated by a less resistive region beneath the Great Bear magmatic zone, which is speculatively interpreted as a consequence of a decrease in the grain size of olivine in the Wopmay mantle, caused by localized shearing, compared to its neighboring cratonic roots. Focused two‐dimensional models, from higher frequency responses at sites on specific sections of the profile, reveal the resistivity structure at crustal depths beneath the region. These suggest that the root of the Slave craton crosses beneath the Wopmay orogen, and that the Wopmay fault zone does not penetrate into the lower crust. A comparison of these results with those obtained during the Lithoprobe project farther south shows striking along strike variations in the conductivity structure associated with the Wopmay orogen.
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    Monitoring temporal variability of bubble release at seeps: The hydroacoustic swath system GasQuant (2008)
    AGU
    In:  Journal of Geophysical Research: Oceans, 113 (C7). C07048.
    Details
    Publication Date: 2020-07-23
    Description: A lander-based hydroacoustic swath system, GasQuant, was deployed in an intensely bubbling seep area at the shelf west of the Crimea Peninsula, Black Sea. With its horizontally oriented swath (21 beams, 63° swath angle, 180 kHz) GasQuant operates in a sonar-like mode and monitors bubbles remotely, exploiting their strong backscattering when crossing the swath. All active seep spots were monitored simultaneously within the covered area (2075 m2). Even applying simple processing and visualization techniques (moving average for filtering, FFT for spectrum analyses; swath and trace plots) identified 17 seeps of different activity patterns that have been grouped as follows: (1) sporadically active with one to a few long bursts (up to 18 min) or randomly occurring short bursts (〈200 bursts and active for 〈5% of the observation time); (2) regularly active seeps showing mainly short bursts of less than one minute but also longer burst of a few minutes (200–350 bursts and 5 to 20% active); (3) frequently active spots with sometimes very periodic bubble release (〉350 bursts or 〉20% active). Studying the bubble release variability of single seeps and of the entire area allows speculation about the external and internal processes that modulate the bubble release. In the study area none of the 17 seeps was found to be permanently active. Only one was active for 75% and another one for 45% of the time monitored. The rest only released bubbles during less than 20% of the time with an overall average of only 12%. This would have strong implications for flux extrapolations if these were based on very accurate but few short-term measurements. Both strong overestimates and underestimates are possible. High-resolution monitoring over at least one tidal cycle as with the GasQuant system might help to get an idea of the temporal variability. Thus flux extrapolations can be corrected to better reflect the real seep activity.
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  • 34
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    Coupled chemistry climate model simulations of the solar cycle in ozone and temperature (2008)
    AGU
    In:  Journal of Geophysical Research: Atmospheres, 113 (D11). pp. 1-20.
    Details
    Publication Date: 2020-07-24
    Description: The 11-year solar cycles in ozone and temperature are examined using new simulations of coupled chemistry climate models. The results show a secondary maximum in stratospheric tropical ozone, in agreement with satellite observations and in contrast with most previously published simulations. The mean model response varies by up to about 2.5% in ozone and 0.8 K in temperature during a typical solar cycle, at the lower end of the observed ranges of peak responses. Neither the upper atmospheric effects of energetic particles nor the presence of the quasi biennial oscillation is necessary to simulate the lower stratospheric response in the observed low latitude ozone concentration. Comparisons are also made between model simulations and observed total column ozone. As in previous studies, the model simulations agree well with observations. For those models which cover the full temporal range 1960–2005, the ozone solar signal below 50 hPa changes substantially from the first two solar cycles to the last two solar cycles. Further investigation suggests that this difference is due to an aliasing between the sea surface temperatures and the solar cycle during the first part of the period. The relationship between these results and the overall structure in the tropical solar ozone response is discussed. Further understanding of solar processes requires improvement in the observations of the vertically varying and column integrated ozone.
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  • 35
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    Decadal-scale periodicities in the stratosphere associated with the solar cycle and the QBO (2008)
    AGU
    In:  Journal of Geophysical Research: Atmospheres, 113 (D5).
    Details
    Publication Date: 2020-07-24
    Description: An interactive two-dimensional model is used to analyze the response of the stratosphere to the 11-year solar cycle in the presence of a quasi-biennial oscillation (QBO). The purpose of the paper is to demonstrate how the solar cycle response of stratospheric ozone and temperature diagnosed from model simulations depends on the QBO. The analyses show that (1) the simulated response to the solar flux when no QBO is imposed is very similar in different periods, despite differences in the magnitude and variability of the solar forcing; (2) the apparent solar response of temperature and ozone is modified by the presence of an imposed QBO; and (3) the impact of the QBO on the derived solar response is greatly reduced when the observed QBO forcing is replaced by an idealized sinusoidal forcing. The impact of the QBO on the solar cycle analysis is larger when only two solar cycles are analyzed but is not negligible even for analysis of four solar cycles. Differences in the QBO contribution account for most of the differences in analyses of separate 22-year periods. The statistical significance is not always a reliable indicator that the QBO effect has been separated.
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    Dynamics of the middle atmosphere as simulated by the Whole Atmosphere Community Climate Model, version 3 (WACCM3) (2008)
    AGU
    In:  Journal of Geophysical Research: Atmospheres, 113 (D8).
    Details
    Publication Date: 2020-07-24
    Description: The Whole Atmosphere Community Climate Model, version 3 (WACCM3) is a state-of-the-art climate model extending from the Earth's surface to the lower thermosphere. In this paper we present a detailed climatology of the dynamics of the middle atmosphere as represented by WACCM3 at various horizontal resolutions and compare them to observations. In addition to the mean climatological fields, we examine in detail the middle atmospheric momentum budget as well as several lower and upper atmosphere coupling phenomena including stratospheric sudden warmings, the 2-day wave, and the migrating diurnal tide. We find that in large part, differences between WACCM3 and observations and the mean state of the model at various horizontal resolutions are related to gravity wave drag, which is parameterized in WACCM3 (and similar models). All three lower and upper atmosphere coupling processes examined show high sensitivity to the model's resolution.
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    Assessment of skill and portability in regional marine biogeochemical models: Role of multiple planktonic groups (2007)
    AGU
    In:  Journal of Geophysical Research: Oceans, 112 (C8).
    Details
    Publication Date: 2020-07-23
    Description: Application of biogeochemical models to the study of marine ecosystems is pervasive, yet objective quantification of these models' performance is rare. Here, 12 lower trophic level models of varying complexity are objectively assessed in two distinct regions (equatorial Pacific and Arabian Sea). Each model was run within an identical one-dimensional physical framework. A consistent variational adjoint implementation assimilating chlorophyll-a, nitrate, export, and primary productivity was applied and the same metrics were used to assess model skill. Experiments were performed in which data were assimilated from each site individually and from both sites simultaneously. A cross-validation experiment was also conducted whereby data were assimilated from one site and the resulting optimal parameters were used to generate a simulation for the second site. When a single pelagic regime is considered, the simplest models fit the data as well as those with multiple phytoplankton functional groups. However, those with multiple phytoplankton functional groups produced lower misfits when the models are required to simulate both regimes using identical parameter values. The cross-validation experiments revealed that as long as only a few key biogeochemical parameters were optimized, the models with greater phytoplankton complexity were generally more portable. Furthermore, models with multiple zooplankton compartments did not necessarily outperform models with single zooplankton compartments, even when zooplankton biomass data are assimilated. Finally, even when different models produced similar least squares model-data misfits, they often did so via very different element flow pathways, highlighting the need for more comprehensive data sets that uniquely constrain these pathways.
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  • 38
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    Modeling the whole atmosphere response to solar cycle changes in radiative and geomagnetic forcing (2007)
    AGU
    In:  Journal of Geophysical Research: Atmospheres, 112 (D23).
    Details
    Publication Date: 2020-07-23
    Description: The NCAR Whole Atmosphere Community Climate Model, version 3 (WACCM3), is used to study the atmospheric response from the surface to the lower thermosphere to changes in solar and geomagnetic forcing over the 11-year solar cycle. WACCM3 is a general circulation model that incorporates interactive chemistry that solves for both neutral and ion species. Energy inputs include solar radiation and energetic particles, which vary significantly over the solar cycle. This paper presents a comparison of simulations for solar cycle maximum and solar cycle minimum conditions. Changes in composition and dynamical variables are clearly seen in the middle and upper atmosphere, and these in turn affect terms in the energy budget. Generally good agreement is found between the model response and that derived from satellite observations, although significant differences remain. A small but statistically significant response is predicted in tropospheric winds and temperatures which is consistent with signals observed in reanalysis data sets.
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  • 39
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    Seismic Earth: Array Analysis of Broadband Seismograms (2005)
    AGU
    In:  Washington, D.C., 280 pages, AGU, vol. 81A and 81B, no. 22, pp. 65-70, (ISBN 0-87590-422-X)
    Details
    Publication Date: 2005
    Keywords: Seismology ; Seismic arrays ; Data analysis / ~ processing ; Ray seismics ; Synthetic seismograms ; Modelling ; Wave propagation ; Waves ; Earth model, also for more shallow analyses ! ; Physical properties of rocks ; Broad-band
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  • 40
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    Freshwater and brine behaviours in the Arctic Ocean deduced from historical data of ð​18O and alkalinity (1929-2002 AD) (2005)
    AGU
    In:  Journal of Geophysical Research: Oceans, 110 (C10003).
    Details
    Publication Date: 2020-07-23
    Description: The long-term data sets of total alkalinity (TA) (1929–2002 A.D.) and δ18O (1966–2002 A.D.) are used to investigate freshwater and brine distributions in the Arctic Ocean. Fractions of sea ice meltwater and other freshwaters (OF) (precipitation, river runoff, and freshwater carried by Pacific water implied as salinity deficit) are calculated on the basis of salinity-TA and salinity-δ18O relationships. Rejected brine during sea ice growth resides in surface water in the central Arctic Ocean, while net melting is found along the surface flow of water from the Pacific and Atlantic oceans. Distribution of OF at 10 m water depth suggests that Russian runoff leaves the shelf mainly west of the Mendeleyev Ridge, enters into the deep basin, and exits from the ocean through the western part of Fram Strait. The influence of Mackenzie River water is limited in the region and in depth. Accumulation of freshwater in the Canadian Basin is caused by deep penetration of OF with brine, indicating the transport of freshwater by shelf-derived water. The major origin of shelf-derived water entering into the upper halocline layer in the Canadian Basin should be the Chukchi and East Siberian Sea shelves, and the main freshwater sources are the salinity deficit of Pacific water and/or Russian runoff. An increase in OF inventory accompanied by an increase in brine content may suggest an increase of the shelf-derived water supply into the western Canadian Basin in anticyclonic years.
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  • 41
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    Earth's Core: Dynamics, Structure, Rotation (2003)
    AGU
    In:  Washington, D.C., 277 pp., AGU, vol. 31, no. 3, pp. 2-203, (ISBN 0-87590-533-1)
    Details
    Publication Date: 2003
    Keywords: earth Core ; GeodesyY ; Earth rotation ; Handbook of geophysics ; Handbook of geodesy
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  • 42
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    Crustal Structure of the Ocean-Continent Transition at Flemish Cap: Seismic Refraction Results (2003)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 108 (B11). p. 2531.
    Details
    Publication Date: 2020-07-23
    Description: We conducted a seismic refraction experiment across Flemish Cap and into the deep basin east of Newfoundland, Canada, and developed a velocity model for the crust and mantle from forward and inverse modeling of data from 25 ocean bottom seismometers and dense air gun shots. The continental crust at Flemish Cap is 30 km thick and is divided into three layers with P wave velocities of 6.0–6.7 km/s. Across the southeast Flemish Cap margin, the continental crust thins over a 90-km-wide zone to only 1.2 km. The ocean-continent boundary is near the base of Flemish Cap and is marked by a fault between thinned continental crust and 3-km-thick crust with velocities of 4.7–7.0 km/s interpreted as crust from magma-starved oceanic accretion. This thin crust continues seaward for 55 km and thins locally to ~1.5 km. Below a sediment cover (1.9–3.1 km/s), oceanic layer 2 (4.7–4.9 km/s) is ~1.5 km thick, while layer 3 (6.9 km/s) seems to disappear in the thinnest segment of the oceanic crust. At the seawardmost end of the line the crust thickens to ~6 km. Mantle with velocities of 7.6–8.0 km/s underlies both the thin continental and thin oceanic crust in an 80-km-wide zone. A gradual downward increase to normal mantle velocities is interpreted to reflect decreasing degree of serpentinization with depth. Normal mantle velocities of 8.0 km/s are observed ~6 km below basement. There are major differences compared to the conjugate Galicia Bank margin, which has a wide zone of extended continental crust, more faulting, and prominent detachment faults. Crust formed by seafloor spreading appears symmetric, however, with 30-km-wide zones of oceanic crust accreted on both margins beginning about 4.5 m.y. before formation of magnetic anomaly M0 (~118 Ma).
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  • 43
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    Structure of the SE Greenland margin from seismic reflection and refraction data: Implications for nascent spreading center subsidence and asymmetric crustal accretion during N Atlantic opening (2003)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 108 (B5). p. 2269.
    Details
    Publication Date: 2020-07-23
    Description: Seismic reflection and refraction data from the SE Greenland margin provide a detailed view of a volcanic rifted margin from Archean continental crust to near-to-average oceanic crust over a spatial scale of 400 km. The SIGMA III transect, located ∼600 km south of the Greenland-Iceland Ridge and the presumed track of the Iceland hot spot, shows that the continent-ocean transition is abrupt and only a small amount of crustal thinning occurred prior to final breakup. Initially, 18.3 km thick crust accreted to the margin and the productivity decreased through time until a steady state ridge system was established that produced 8–10 km thick crust. Changes in the morphology of the basaltic extrusives provide evidence for vertical motions of the ridge system, which was close to sea level for at least 1 m.y. of subaerial spreading despite a reduction in productivity from 17 to 13.5 km thick crust over this time interval. This could be explained if a small component of active upwelling associated with thermal buoyancy from a modest thermal anomaly provided dynamic support to the rift system. The thermal anomaly must be exhaustible, consistent with recent suggestions that plume material was emplaced into a preexisting lithospheric thin spot as a thin sheet. Exhaustion of the thin sheet led to rapid subsidence of the spreading system and a change from subaerial, to shallow marine, and finally to deep marine extrusion in ∼2 m.y. is shown by the morphological changes. In addition, comparison to the conjugate Hatton Bank shows a clear asymmetry in the early accretion history of North Atlantic oceanic crust. Nearly double the volume of material was emplaced on the Greenland margin compared to Hatton Bank and may indicate east directed ridge migration during initial opening.
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  • 44
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    Cruise Report F.S. ALKOR Cruise No. 229 (2003)
    Institut für Meereskunde
    In:  Alkor-Berichte, AL229 . Institut für Meereskunde, Kiel, Germany, 30 pp.
    Details
    Publication Date: 2021-01-28
    Description: Dates of Cruise: 15.09. to 18.09.2003 Projects: BASEWECS and Student course in physical oceanography; Port Calls: Warnemünde (15.09. and 18.09.2003)
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  • 45
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    Cruise Report F.S. ALKOR Cruise No. 223 (2003)
    Institut für Meereskunde
    In:  Alkor-Berichte, AL223 . Institut für Meereskunde, Kiel, Germany, 22 pp.
    Details
    Publication Date: 2021-01-28
    Description: Dates of Cruise: 07.07. - 09.07.2003 Projects: BASEWECS and Student course in physical oceanography; Port Calls: Warnemünde, 07.07.-08.07.2003
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  • 46
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    On the generation of microseismics observed in north and central Europe (2003)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 108 (B10). p. 2506.
    Details
    Publication Date: 2020-07-23
    Description: Microseism recordings from four European broadband stations and from three seismic arrays in Scotland, Norway, and Germany are compared with model wave data of the oceanic wave field in the North Atlantic and local ocean wave data from the Norwegian coast at 60�N, both measured during February–March 2000. Two approaches have been tested to locate generation areas of microseismic energy: a new amplitude correlation technique and beam backprojection from the three seismic arrays. Both techniques reveal that the main generation areas are located in specific regions off the coast of Southwest Norway and North Scotland. Seismic stations distant from these generation areas record a superposition of seismic energy from different source regions. Those close to a specific source region also show a high correlation with it. Both techniques give upper limits for the extent of the generation area of the strongest storm on 6/7 March at the southwest Norwegian coast of about 500 km. By using marine X-band radar measurements of the two-dimensional wave height spectrum, we estimate that the relative change of the extension of the generation area off the coast of southwest Norway during several storms is less than a factor of 3. This indicates that the size of the generation area is controlled by static features as coastline or bathymetry, and not by the extent of the storms. Microseism energy appears to be mainly controlled by the wave height in distinct and identifiable generation regions, so that the wave climate in these regions can be studied using historical records of microseisms.
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  • 47
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    A comparison of the impact of major mesozooplankton taxa on marine, brackish and freshwater phytoplankton during summer (2003)
    Institut für Meereskunde
    Details
    Publication Date: 2023-01-30
    Description: The impact by freshwater and marine mesozooplankton on phytoplankton particle size and stoichiometry was studied. Additionally, zooplankton d15N were determined as an inidicator of trophic level. Mesocosm studies, using logarithmically scaled zooplankton density gradients, were performed at three locations (lake Schoehsee, the marine Hopavagen lagoon, Norway, and Kiel Fjord) in August 2000, July 2001 and September 2002. In two of the three studies (Schoehsee, Hopavagen), zooplankton shifted phytoplankton size structure predictably to small or large species, respectively, with freshwater zooplankton (copepods, Daphnia) being complementary in their impact. Stoichiometrically, both Daphnia and marine copepods increased the carbon to nutrient ratios (C:P or C:N) of POM, indicative of phytoplankton nutrient limitation. Yet, while the depletion of P in freshwater POM was due to its retention in ‘new’ Daphnia biomass (numerical increase), the mechanism for marine copepods was different: copepods triggered the growth of nanoflagellates via a a trophic cascade (‘copepods-ciliates-nanoflagellates’), which increased at the expense of their intracellular nitrogen pool. Measurements of zooplankton d15N showed that differences were large between Daphnia and freshwater copepods (3.2 to 4.8‰), while negligible between marine copepods and the appendicularian Oikopleura dioica. Moreover, stable isotope analysis revealed different patterns of d15N enrichment for cruising versus stationary suspension feeding copepods, and also traced the (indirect) transfer of isotopically ‘light’ nitrogen from diazotrophic cyanobacteria to zooplankton.
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  • 48
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    Plate Boundary Zones (2002)
    AGU
    In:  Washington, D.C., vii + 425 pp., AGU, vol. 30, no. Publ. No. 12, pp. 95-104, (ISBN 0-87590-532-3, AGU Code: GD0305323)
    Details
    Publication Date: 2002
    Keywords: Textbook of geophysics ; Plate tectonics ; Seismicity ; Seismology
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  • 49
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    The global moment rate distribution within plate boundary zones (2002)
    AGU
    In:  Bull., Polar Proj. OP-O3A4, Plate Boundary Zones, Washington, D.C., AGU, vol. 30, no. 2, pp. 173-190, (ISBN 0-87590-532-3, AGU Code: GD0305323)
    Details
    Publication Date: 2002
    Keywords: Crustal deformation (cf. Earthquake precursor: deformation or strain) ; Strain ; GSRM ; map ; Paleomagnetism ; Plate tectonics ; Seismicity
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  • 50
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    Radiogenic isotopes: Tracers of past ocean circulation and erosional input (2002)
    AGU
    In:  Reviews of Geophysics, 40 (1).
    Details
    Publication Date: 2020-06-03
    Description: The radiogenic isotope composition of dissolved trace metals in the ocean represents a set of relatively new and not yet fully exploited tracers with a large potential for oceanographic and paleoceanographic research on timescales from the present back to at least 60 Ma. The main topic of this review are those trace metals with oceanic residence times on the order of or shorter than the global mixing time of the ocean (Nd, Pb, Hf, and, in addition, Be). Their isotopic composition in the ocean has varied as a function of changes in paleocirculation, source provenances, style and intensity of weathering on the continents, as well as orogenic processes. The relative importance of these processes for each trace metal is evaluated, which is a prerequisite for reliable interpretation of their time series in terms of changes in paleocirculation or weathering inputs. This analysis of processes includes a discussion of the long-term isotopic evolution of Sr and Os, which are well mixed in the ocean and have thus not been influenced by circulation changes. The radiogenic isotope evolution of those trace metals with intermediate oceanic residence times can be used as paleoceanographic proxies to reconstruct paleocirculation and weathering inputs into the ocean. This is demonstrated by studies from different ocean basins, mainly carried out on ferromanganese crusts, which show that radiogenic trace metal isotopes provide important new insights and can complement results obtained by other well-established paleoceanographic tracers such as carbon isotopes.
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  • 51
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    Magma flow regimes in sills deduced from Ar isotope systematics of host rocks (2001)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 106 (B3). pp. 4017-4036.
    Details
    Publication Date: 2020-07-23
    Description: The best place to seek evidence of the style of past magma flow through a conduit is in the country rock. Heat flow has been studied in country rock adjacent to two Tertiary dolerite sills intruding the Caledonian schists and quartzites, on the Isle of Mull, Scotland. Radiogenic 40Ar loss within mica grains in the thermal aureoles of the intrusions has been measured at high spatial resolution using the Ultra-Violet Laser Ablation Micro-Probe, to discriminate between a history of prolonged magma flow, a history of conductive cooling following laminar flow, and instantaneous emplacement of the intrusions. The 40Ar/39Ar mica data and thermal modeling suggest that a prolonged period of magma flow of 3–5 months resulted in extensive argon loss from the micas, country rock melting, and mineral breakdown adjacent to a 6-m sill. These features were absent from the wall rocks of a smaller 2.7-m-thick sill, which exhibited even less argon loss than might have been predicted for an instantaneous intrusion. If the heat loss from the 6-m sill observed in one locality had been repeated along its length, it would have formed an important magma conduit to the Mull volcano, but dolerite is not a common flow composition on Mull. If on the other hand, the heat loss from the sill varies along strike, it constitutes strong evidence for channelling and heterogeneous flow within the sill.
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  • 52
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    Mikrowellenfernerkundung bei inhomogener Bewölkung (2001)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 321 . Institut für Meereskunde, Kiel, Germany, 137 pp.
    Details
    Publication Date: 2017-01-03
    Type: Report , NonPeerReviewed
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  • 53
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    Stability and variability of the thermohaline circulation in the past and future: A study with a coupled model of intermediate complexity (2001)
    AGU
    In:  Oceans and rapid past and future climate changes: North-South connections
    Details
    Publication Date: 2022-03-21
    Type: info:eu-repo/semantics/bookPart
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  • 54
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    KAPEX RAFOS Float Data Report 1997-1999, part A: The Agulhas- and South Atlantic Current Components (2000)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 318 . Institut für Meereskunde, Kiel, Germany, 194 pp.
    Details
    Publication Date: 2019-09-23
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  • 55
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    Stability and variability of the thermohaline circulation in the past and future: A study with a coupled model of intermediate complexity (2000)
    AGU
    In:  Oceans and rapid past and future climate changes: North-south connections
    Details
    Publication Date: 2022-03-21
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  • 56
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    The Extended OMP Analysis: An Analysis Package for MATLAB Version 1 (1999)
    Institut für Meereskunde
    In:  Technical report / Institute of Oceanography, University of Hamburg, 99,1 . Institut für Meereskunde, Hamburg, Germany, 28 pp.
    Details
    Publication Date: 2021-02-15
    Type: Report , NonPeerReviewed
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  • 57
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    Checklist of metazoan fish parasites of German coastal waters (1999)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 307 . Institut für Meereskunde, Kiel, Germany, 148 pp.
    Details
    Publication Date: 2019-07-26
    Type: Report , NonPeerReviewed
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  • 58
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    Bildung, Zusammensetzung und Sinkgeschwindigkeiten mariner Aggregate (1998)
    Institut für Meereskunde
    In:  (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 145 pp . Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 300 . DOI 10.3289/IFM_BER_300 〈http://dx.doi.org/10.3289/IFM_BER_300〉.
    Details
    Publication Date: 2013-07-31
    Type: Thesis , NonPeerReviewed
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  • 59
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    SI-Einheiten in der Ozeanographie = SI units in oceanography (1998)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 101C . Institut für Meereskunde, Kiel, Germany, 18 pp.
    Details
    Publication Date: 2013-03-14
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  • 60
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    Modellierung der mittleren Zirkulation im Südatlantik (1997)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 287 . Institut für Meereskunde, Kiel, Germany, IV, 130 pp.
    Details
    Publication Date: 2013-03-18
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  • 61
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    DYNAMO : dynamics of North Atlantic models : simulation and assimilation with high resolution models (1997)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 294 . Institut für Meereskunde, Kiel, Germany, 334 pp.
    Details
    Publication Date: 2019-09-23
    Type: Report , NonPeerReviewed
    Format: text
    Format: text
    Format: text
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  • 62
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    Data report to "Estimation of the total fish biomass in the Baltic Sea during the 20th century" : with addition to "Estimation of some fish species' biomasses in the Baltic Sea during the 20th century" (1997)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 285 . Institut für Meereskunde, Kiel, Germany, 82 pp.
    Details
    Publication Date: 2013-02-19
    Type: Report , NonPeerReviewed
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  • 63
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    The Impact of Data Assimilation on ENSO Simulations and Predictions (1997)
    American Meteorological Society
    In:  Monthly Weather Review, 125 (5). pp. 819-830.
    Details
    Publication Date: 2020-06-30
    Description: In this study, the impact of oceanic data assimilation on ENSO simulations and predictions is investigated. The authors’ main objective is to compare the impact of the assimilation of sea level observations and three-dimensional temperature measurements relative to each other. Three experiments were performed. In a control run the ocean model was forced with observed winds only, and in two assimilation runs three-dimensional temperatures and sea levels were assimilated one by one. The root-mean-square differences between the model solution and observations were computed and heat content anomalies of the upper 275 m compared to each other. Three ensembles of ENSO forecasts were performed additionally to investigate the impact of data assimilation on ENSO predictions. In a control ensemble a hybrid coupled ocean–atmosphere model was initialized with observed winds only, while either three-dimensional temperatures or sea level data were assimilated during the initialization phase in two additional forecast ensembles. The predicted sea surface temperature anomalies were averaged over the eastern equatorial Pacific and compared to observations. Two different objective skill measures were computed to evaluate the impact of data assimilation on ENSO forecasts. The authors’ experiments indicate that sea level observations contain useful information and that this information can be inserted successfully into an oceanic general circulation model. It is inferred from the forecast ensembles that the benefit of sea level and temperature assimilation is comparable. However, the positive impact of sea level assimilation could be shown more clearly when the forecasted temperature differences rather than the temperature anomalies themselves were compared with observations.
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  • 64
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    The Coupled GCM ECHO-2. Part I: The Tropical Pacific (1997)
    American Meteorological Society
    In:  Monthly Weather Review, 125 . pp. 703-720.
    Details
    Publication Date: 2020-06-30
    Description: In this paper the performance of the global coupled general circulation model (CGCM) ECHO-2, which was integrated for 10 years without the application of flux correction, is described. Although the integration is rather short, strong and weak points of this CGCM can be clearly identified, especially in view of the model's performance of the annual cycle in the tropical Pacific. The latter is simulated with more success relative to the earlier version, ECHO-I. A better representation of the low-level stratus clouds in the atmosphere model associated with a reduction in the shortwave radiative flux at the air-sea interface improved the coupled model's performance in the southeastern tropical oceans, with a strongly reduced warm bias in these regions. Modifications in the atmospheric convection scheme also eliminated the AGCM's tendency to simulate a double ITCZ, and this behavior is maintained in the CGCM simulation. Finally, a new numerical scheme for active tracer advection in the ocean model strongly reduced the numerical mixing, which seems to enhance considerably the level of interannual variability in the equatorial Pacific. One weak point is an overall cold bias in the Tropics and midlatitudes, which typically amounts to 1°C in open ocean regions. Another weak point is the still too strong equatorial cold tongue, which penetrates too far into the western equatorial Pacific. Although this model deficiency is not as pronounced as in ECHO-1, the too strong cold tongue reduces the level of interannual rainfall variability in the western and central equatorial Pacific. Finally, the interannual fluctuations in equatorial Pacific sea surface temperatures (SSTs) are too equatorially trapped, a problem that is also found in ocean-only simulations. Overall, however, the authors believe that the ECHO-2 CGCM has been considerably improved relative to ECHO-1.
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    To Boldy Go - A Practical Career Guide for Scientists (1996)
    AGU
    In:  Washington, D.C., AGU, vol. 283, no. 2, pp. 15-17, (ISBN: 3-7643-7044-0)
    Details
    Publication Date: 1996
    Keywords: resumes ; CVs ; Bewerbungen ; applications
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  • 66
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    Niederschlagsmessung auf dem Ozean von fahrenden Schiffen (1996)
    Institut für Meereskunde
    In:  (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 112 pp . Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 278 . DOI 10.3289/ifm_ber_278 〈http://dx.doi.org/10.3289/ifm_ber_278〉.
    Details
    Publication Date: 2016-11-30
    Type: Thesis , NonPeerReviewed
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  • 67
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    Systematische Einflüsse auf die Bestimmung der Schubspannung mit der "Dissipationsmethode" auf See (1996)
    Institut für Meereskunde
    In:  (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 116 pp . Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 279 . DOI 10.3289/IFM_BER_279 〈http://dx.doi.org/10.3289/IFM_BER_279〉.
    Details
    Publication Date: 2013-11-19
    Type: Thesis , NonPeerReviewed
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  • 68
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    Study of passive remote sensing of the atmosphere and surface ice (1996)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 297 . Institut für Meereskunde, Kiel, Germany, 241 pp.
    Details
    Publication Date: 2016-10-07
    Type: Report , NonPeerReviewed
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  • 69
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    Hydrography above the Mid-Atlantic Ridge (33°–40°N) and within the Lucky Strike segment (1995)
    AGU
    In:  Journal of Geophysical Research: Oceans, 100 (C10). p. 20555.
    Details
    Publication Date: 2020-07-23
    Description: As part of the French-American Ridge Atlantic program the French-American Zero-Angle Photon Spectrometer and Rocks (FAZAR) cruise conducted water column studies between 33 and 40 degrees N along the Mid-Atlantic Ridge (MAR)) to detect hydrothermal activity and map its influence, This paper describes the large-scale hydrography within the axial valley, with particular emphasis on the hydrothermally active Lucky Strike segment (37 degrees 17'N). The FAZAR study area is affected be the presence of the Azores Current and Mediterranean Water (MW). Although the MW core has been mapped as far north as 50 degrees N off the ridge; the northern boundary Of the MW within the MAR in the FAZAR study area exists as a strong front south of the Azores platform. This front is most likely caused by the shallower ridge crest becoming a physical barrier to the MW. The Lucky Strike segment lies within this front and, as a result, has complicated hydrography which can obscure hydrothermal temperature and salinity anomalies.
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  • 70
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    The Seasonal Cycle over the Tropical Pacific in Coupled Ocean–Atmosphere General Circulation Models (1995)
    American Meteorological Society
    In:  Monthly Weather Review, 123 (9). pp. 2825-2838.
    Details
    Publication Date: 2020-06-30
    Description: The seasonal cycle over the tropical Pacific simulated by 11 coupled ocean–atmosphere general circulation models (GCMs) is examined. Each model consists of a high-resolution ocean GCM of either the tropical Pacific or near-global means coupled to a moderate- or high-resolution atmospheric GCM, without the use of flux correction. The seasonal behavior of sea surface temperature (SST) and eastern Pacific rainfall is presented for each model. The results show that current state-of-the-art coupled GCMs share important successes and troublesome systematic errors. All 11 models are able to simulate the mean zonal gradient in SST at the equator over the central Pacific. The simulated equatorial cold tongue generally tends to be too strong, too narrow, and extend too far west. SSTs are generally too warm in a broad region west of Peru and in a band near 10°S. This is accompanied in some models by a double intertropical convergence zone (ITCZ) straddling the equator over the eastern Pacific, and in others by an ITCZ that migrates across the equator with the seasons; neither behavior is realistic. There is considerable spread in the simulated seasonal cycles of equatorial SST in the eastern Pacific. Some simulations do capture the annual harmonic quite realistically, although the seasonal cold tongue tends to appear prematurely. Others overestimate the amplitude of the semiannual harmonic. Nonetheless, the results constitute a marked improvement over the simulations of only a few years ago when serious climate drift was still widespread and simulated zonal gradients of SST along the equator were often very weak.
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  • 71
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    Untersuchungen zur Systematik von Rüsselbandwürmern (Cestoda: Trypanorhyncha) aus atlantischen Fischen (1995)
    Institut für Meereskunde
    In:  (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 238 pp . Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 275 . DOI 10.3289/ifm_ber_275 〈http://dx.doi.org/10.3289/ifm_ber_275〉.
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    Publication Date: 2013-07-31
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  • 72
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    Bio-C-Flux : biologischer Kohlenstofffluß in der bodennahen Wasserschicht des küstenfernen Ozeans ; Schlußbericht für den Förderzeitraum 1.1.1990 - 31.12.1994 (1995)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 280 . Institut für Meereskunde, Kiel, Germany, 114 pp.
    Details
    Publication Date: 2016-03-18
    Type: Report , NonPeerReviewed
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  • 73
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    Anthropogenes CO2 im Nordatlantik - Methodische Entwicklungen und Messungen zur Quantifizierung des anthropogenen CO2-Signals (1995)
    Institut für Meereskunde
    Details
    Publication Date: 2023-03-22
    Type: Thesis , NonPeerReviewed
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  • 74
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    Geochemical effects of dynamic melting beneath ridges: Reconciling major and trace element variations in Kolbeinsey (and global) mid-ocean ridge basalt (1994)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 99 (B5). pp. 9077-9095.
    Details
    Publication Date: 2020-07-23
    Description: Zero-age basalts dredged from the Kolbeinsey Ridge directly north of Iceland are mafic quartz tholeiites (MgO 6-10 wt. %), strongly depleted in incompatible elements. Fractionation-corrected Na2O contents ('Na(sub 8)') are amongst the lowest found on the global ridge system, implying that the degree of partial melting at Kolbeinsey is amongst the highest for all mid-ocean ridge basalt (MORB). In contrast, the basalts show large ranges of incompatible-element ratios (e.g., K2O/TiO2 of 0.01 to 0.12 and Nd/Sm of 2.1 to 2.9) not related to variations in radiogenic isotope ratios; this suggests recent enrichment/depletion events associated with small-degree partial melting as their cause, rather than long-lived source heterogeneity. Tholeiitic MORB from many regions globally show similar or more extreme variations in K2O/TiO2. Dynamic melting of an adiabatically upwelling source can reconcile these conflicting indications of the degree of melting. Through dynamic melting, the incompatible elements are partially separated into different melt fractions based on their bulk partition coefficients, more incompatible elements being concentrated in deeper, smaller-degree partial melts. The final erupted magma is a mix of melts from all depths in the melting column. The concentration of highly incompatible elements in the mix will be very sensitive to the physical processes allowing the deep melts to separate and migrate to the site of mixing, and small fluctuations in the efficiency of the separation process can account for the large range of trace element ratios seen at Kolbeinsey. The major element chemistry of the erupted mix (and Na(sub 8) is much more robust, depending mainly on the integrated total amount of melting. The large variations of incompatible element ratios seen at Kolbeinsey, and in MORB in general, therefore give no information about the total degree of melting occuring beneath the ridge, nor do they require a heterogeneous source.
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  • 75
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    Samuel REYHER (1635-1714) und sein "Experimentum Novum" (1994)
    Institut für Meereskunde
    In:  In: 300 Jahre Meeresforschung an der Universität Kiel : ein historischer Rückblick. Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 246 . Institut für Meereskunde, Kiel, Germany, pp. 3-12.
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    Publication Date: 2015-11-26
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  • 76
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    Leichtflüchtige Halogenkohlenwasserstoffe: Austauschprozesse zwischen Atmosphäre und Meerwasser (1994)
    Institut für Meereskunde
    In:  (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 145 pp . Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 247 . DOI 10.3289/ifm_ber_247 〈http://dx.doi.org/10.3289/ifm_ber_247〉.
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    Publication Date: 2014-10-14
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  • 77
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    Großräumige Zirkulation und meridionale Transporte im Südatlantik (1994)
    Institut für Meereskunde
    In:  (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 96 pp . Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 260 . DOI 10.3289/ifm_ber_260 〈http://dx.doi.org/10.3289/ifm_ber_260〉.
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    Publication Date: 2013-05-22
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  • 78
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    300 Jahre Meeresforschung an der Universität Kiel (1994)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 246 . Institut für Meereskunde, Kiel, Germany, 58 pp.
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    Publication Date: 2017-07-12
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  • 79
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    Sonderforschungsbereich 133 Warmwassersphäre des Atlantiks - Eine Dokumentation - (1994)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 258 . Institut für Meereskunde, Kiel, Germany, 129 pp.
    Details
    Publication Date: 2014-10-13
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  • 80
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    Fahrtbericht zur Aal-Expedition mit FS Poseidon (Reise 200/1) in die Sargasso-See im Frühjahr 1993 (1994)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 248 . Institut für Meereskunde, Kiel, Germany, 33 pp.
    Details
    Publication Date: 2014-11-07
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  • 81
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    A moared array along the southern boundary of the Brazil Basin for the Deep Basin Experiment - Report on a joint experiment 1991-1992 (1994)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 243 . Institut für Meereskunde, Kiel, Germany, 107 pp.
    Details
    Publication Date: 2016-10-11
    Description: The Deep Basin Experiment (DBE) is an international effort and apart of the World Ocean Circulation Experiment with the principal objective of improving our knowledge of the subthermocline circulation. The DBE fieldwork is focussed on the Brazil Basin and this report is concemed with a moored array situated along its southem boundary which was installed in early 1991 to measure the inflow and outflow to the Basin and to investigate the Brazil Current near 30S. This moored array was a joint undertaking by the Institut für Meereskunde of the University of Kiel and the Woods Hole Oceanographic Institution. Moorings were deployed on Meteor Cruise 15, leg I and retrieved on Meteor cruise 22, legs 3 and 4. A total of 57 conventional current meters and two Acoustic Doppler Current Profilers were set on 13 moarings with some concentration within the Brazil Current and the Vema Channel. CTDs were taken at each mooring site as well as in between. Some of the recovered instruments were reset in the Hunter Channel, a suspected additional connection between the Argentine Basin and the Brazil Basin. A later report will summarize this data after it is recovered in May 1994.
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  • 82
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    Plate kinematics in a global and European scale by Lageos laser data from 1983 to 1990 (1993)
    AGU
    In:  Professional Paper, Contribution of Space Geodesy to Geodynamics: Crustal Dynamics, Washington, AGU, vol. 23, no. Subvol. b, pp. 311-329, (ISBN: 3-540-23712-7)
    Details
    Publication Date: 1993
    Keywords: Plate tectonics ; Crustal deformation (cf. Earthquake precursor: deformation or strain) ; ranging ; Geodesy ; Review article
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  • 83
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    Space geodesy and plate motions (1993)
    AGU
    In:  Bull., Open-File Rept., Contribution of Space Geodesy to Geodynamics: Crustal Dynamics, Washington, AGU, vol. 23, no. 16, pp. 5-20, (ISBN 1-86239-165-3, vi + 330 pp.)
    Details
    Publication Date: 1993
    Keywords: Plate tectonics ; Crustal deformation (cf. Earthquake precursor: deformation or strain) ; ranging ; Geodesy ; Review article
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  • 84
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    A simple rheological framework for comparative subductology (1993)
    AGU
    In:  Bull., Open-File Rept., Relating Geophysical Structures and Processes, Washington, D. C., AGU, vol. 76, no. 16, pp. 39-52, (ISBN 1-86239-165-3, vi + 330 pp.)
    Details
    Publication Date: 1993
    Keywords: Subduction zone ; Rheology
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  • 85
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    Assimilation hydrographischer Daten in ein Zirkulationsmodell des Atlantiks auf der Grundlage des adjungierten Verfahrens (1993)
    Institut für Meereskunde
    In:  (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 157 pp . Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 235 . DOI 10.3289/ifm_ber_235 〈http://dx.doi.org/10.3289/ifm_ber_235〉.
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    Publication Date: 2013-08-01
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  • 86
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    Spatial and temporal variability of selected trace metals in Kiel Bight and Mecklenburg Bight : data report from 1990/92 = Räumliche und zeitliche Variabilität ausgewählter Spurenmetalle in der Kieler und Mecklenburger Bucht (1993)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 238 . Institut für Meereskunde, Kiel, Germany, 83 pp.
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    Publication Date: 2018-03-05
    Type: Report , NonPeerReviewed
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  • 87
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    Wissenschaftliche Grundlagen für ökosystem-orientiertes Fischereimanagement in den Gewässern vor Grönland (1993)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 234 . Institut für Meereskunde, Kiel, Germany, 78 pp.
    Details
    Publication Date: 2014-08-19
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  • 88
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    BIO-C-FLUX : biologischer Kohlenstofffluß in der bodennahen Wasserschicht des küstenfernen Ozeans ; Abschlußbericht für den Förderzeitraum 1.1.1990 - 31.12.1992 (1993)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 242 . Institut für Meereskunde, Kiel, Germany, 130 pp.
    Details
    Publication Date: 2014-10-14
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  • 89
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    Das biologische Monitoring der Ostsee im Institut für Meereskunde Kiel 1985-1992 (1993)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 240 . Institut für Meereskunde, Kiel, Germany, 207 pp.
    Details
    Publication Date: 2014-08-15
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  • 90
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    Saisonale und langzeitliche Veränderungen chemisch-hdyrographischer Parameter in der Kieler Bucht (1993)
    Institut für Meereskunde
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    Publication Date: 2023-03-09
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  • 91
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    Fluids in accretionary prisms (1992)
    AGU
    In:  Reviews of Geophysics, 30 (2). p. 113.
    Details
    Publication Date: 2020-06-03
    Description: Accretionary prisms are composed of initially saturated sediments caught in subduction zone tectonism. As sediments deform, fluid pressures rise and fluid is expelled, resembling a saturated sponge being tectonically squeezed. Fluid flow from the accretionary prism feeds surface biological cases, precipitates and dissolves minerals, and causes temperature and geochemical anomalies. Structural and metamorphic features are affected at all scales by fluid pressures or fluid flow in accretionary prisms. Accordingly, this dynamic tectonic environment provides an accessible model for fluid/rock interactions occurring at greater crustal depths. Porosity reduction and to a lesser degree mineral dehydration and the breakdown of sedimentary organic matter provide the fluids expelled from accretionary prisms. Mature hydrocarbons expulsed along prism faults indicate deep sources and many tens of kilometers of lateral transport of fluids. Many faults cutting accretionary prisms expel fluids fresher than seawater, presumably generated by dehydration of clay minerals at depth. Models of fluid flow from accretionary prisms use Darcy's law with matrix and fractures/faults being assigned different permeabilities. Fluid pressures in accretionary prisms are commonly high but range from hydrostatic to lithostatic. Matrix or intergranular permeability ranges from less than 10−20 m² to 10−13 m². Fracture permeability probably exceeds 10−12 m². A global estimate of fluid flux into accretionary prisms suggests they recycle the oceans every 500 m.y. Fluid flow out of accretionary prisms occurs by distributed flow through intergranular permeability and along zones of focused flow, typically faults. Focused fluid flow is 3 to 4 orders of magnitude faster than distributed flow, probably representing the mean differences in permeability along these respective expulsion paths. During the geological evolution of accretionary prisms, distributed flow through pore spaces decreases as a result of consolidation and cementation, whereas flow along fracture systems becomes dominant. Although thrust faults are most common in the compressional environment of accretionary prisms, normal and strike-slip faults are efficient fluid drains, because they are easier to dilate. Observations from both modern and ancient prisms suggest episodic fluid flow which is probably coupled to episodic fault displacement and ultimately to the earthquake cycle.
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  • 92
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    Beitrag zum Schwermetallgehalts-Monitoring (Zn, Cd, Hg, Cn, Ag, Pb, Cr, Ni)in Miesmuscheln an der schleswig-holsteinischen Ostseeküste (1988/89) (1992)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 221 . Institut für Meereskunde, Kiel, Germany, 146 pp.
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    Publication Date: 2014-06-03
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  • 93
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    Principles of RAFOS technology at the Institut für Meereskunde Kiel (1992)
    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 222 . Institut für Meereskunde, Kiel, Germany, 99 pp.
    Details
    Publication Date: 2014-06-03
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  • 94
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    On the seasonal phytoplankton concentration and sea surface temperature cycles of the Gulf of Mexico as determined by satellites (1991)
    AGU
    In:  Journal of Geophysical Research: Oceans, 96 (C7). pp. 12645-12665.
    Details
    Publication Date: 2020-07-23
    Description: Monthly climatologies of near-surface phytoplankton pigment concentration and sea surface temperature (SST) were derived for the Gulf of Mexico from multiyear series of coastal zone color scanner (CZCS) (November 1978 to November 1985) and advanced very high resolution radiometer (AVHRR) (January 1983 to December 1987) images. We complement these series with SST from the comprehensive ocean-atmosphere data set (1946–1987) and Climate Analysis Center (1982–1990), and hydrographic profile data from the NOAA National Oceanographic Data Center (1914–1985). The CZCS ocean color satellite data provide the first climatological time series of phytoplankton concentration for the region. The CZCS images show that seasonal variation in pigment concentration seaward of the shelf is synchronous throughout the gulf, with highest values (〉0.18 mg m−3) in December to February and lowest values (∼0.06 mg m−3) in May to July. Variation in SST is also synchronous throughout the gulf, with maxima in July to September and minima in February to March, The amplitude of the SST variation in the western gulf is about twice that observed in the eastern gulf, and SST maxima and minima persist longer in the west. Larger amplitudes in SST variation are also observed toward the margins. While annual cycles of SST and pigment concentrations are out of phase relative to each other, the phases of mixed layer depth change and pigment concentration change are similar. Model simulations suggest that the single most important factor controlling the seasonal cycle in surface pigment concentration is the depth of the mixed layer. The combined use of ocean color and infrared images permits year-round observation of spatial structure of the surface circulation in the gulf and the pattern of dispersal of the Mississippi River plume. Infrared images are most useful between November and mid-May, when strong SST gradients occur. During this time, pigment concentrations are high and can be horizontally homogeneous. In contrast, between late May and October, SST fields are uniform, but the Loop Current and large anticyclonic eddies could be traced with the CZCS. Three anticyclonic eddies were observed in 1979, and at least two were observed in 1980. No eddies were observed during summers of subsequent years in the CZCS time series, but this may be a result of the dramatic decrease in the satellite sampling rate. The series of color images showed that small parcels of Mississippi River water were frequently (2–4 times a year) entrained in the cyclonic edge of the Loop Current, stretched along the Current, and carried to the southeast along the western Florida shelf. However, most of the Mississippi River water flowed to the west, following the Louisiana-Texas coast as far south as the Mexico-United States border. Here, a persistent cyclone may reside, exporting shelf constituents to deeper regions of the gulf.
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  • 95
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    Detection of limiting factors for bacterial activity using protease activity (1991)
    Institut für Meereskunde
    Details
    Publication Date: 2022-06-02
    Description: Responses in protease activity, caused by adding nutrients to batch cultures of a Vibrio sp., grown to equilibria in a chemostat system at 5 °C with C, N or P-limited media, was measured after O, 6 - 8 and 24 C±) hrs. Addition of the limiting nutrient gave the largest response in activity, due to an increase in bacterial numbers. Reduction in activity per cell was, however, observed in some cases. In field samples from the Skagerak, clear responses within 24 hrs were either absent or found when both C, N and P-sources were added. In the field samples, less changes were found in activity per cell. At three coastal stations, detectable responses were found to additions of P04 3- alone, or in some combinations. When measured, leucine incorporation gave a response pattern to P04 3- additions similar to that of protease activity.
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  • 96
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    Denitrifying Blastobacter sp. from marine intertidal sediments (1991)
    Institut für Meereskunde
    Details
    Publication Date: 2022-06-03
    Type: Article , NonPeerReviewed
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  • 97
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    Limitations of nalidixic acid dependent viable direct counts in sediment samples (1991)
    Institut für Meereskunde
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    Publication Date: 2022-06-03
    Description: A direct microscopic method based on the response of bacterial cells to inhibition of DNA synthesis by nalidixic acid in the presence of growth-supporting yeast extract and designed to determine the number of viable bacteria, was tested in marine sediments bioturbated by the deposit-feeding polychaete Arenicola marina. The number of responsive cells in sediment samples ingested and egested by the polychaete, reflected similar differences and trends as total direct counts or plate counts. Nevertheless, application of that viable direct count technique in marine sediments suffered also from considerable systematic errors.
    Type: Article , NonPeerReviewed
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  • 98
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    Phytoplankton : bacteria relationship and incidence of vibrios in brackish coastal waters (1991)
    Institut für Meereskunde
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    Publication Date: 2022-06-03
    Description: For brackish water bodies at the North Sea coast which harbor red tide algal blooms during the summer months, phytoplankton densities and chlorophyll a data were compared with bacterial counts including plate counts of TCBS-agar-selected vibrios. Concentrations of chlorophyll a, the ratios of total viable counts on ZoBell agar to acridine orange direct counts (CFU/ AODC), and vibrio counts on TCBS-agar followed largely the same trends suggesting a strong linkage between phytoplankton biomass and heterotrophic cacteria. Enrichment experiments based on macroalgal extracts confirmed the extremely copiotrophic nature of TCBS-selected vibrios. Vibrio counts peaked during the bloom of a Cryptomonas sp. that was presumably grazed upon by a ciliate, Strombidium sp.. On the other hand, there were no indications of an analogous coincidence during mass developments of the potentially toxic dinoflagellate Glenodinium foliaceum.
    Type: Article , NonPeerReviewed
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  • 99
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    Isolation and identification of anaerobic sulfur dependent thermophilic bacteria from two new hydrothermal sites in SW Pacific (Lau Basin and North Fiji Basin) (1991)
    Institut für Meereskunde
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    Publication Date: 2022-06-03
    Type: Article , NonPeerReviewed
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  • 100
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    Resistance to cadmium in a marine bacterium (1991)
    Institut für Meereskunde
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    Publication Date: 2022-06-03
    Type: Article , NonPeerReviewed
    Format: text
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