Time-dependent greenhouse warming computations with a coupled ocean-atmosphere model     

Ulrich Cubasch  Klaus Hasselmann  Heinke Höck  Ernst Maier-Reimer  Uwe Mikolajewicz  Benjamin D Santer  Robert Sausen 《Climate Dynamics》1993,9(3):165-165

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Scanning electron microscopy,cathodoluminescence, and Raman spectroscopy of experimentally shock‐metamorphosed quartzite     

Arnold Gucsik  Christian Koeberl  Franz Brandsttter  Eugen Libowitzky  Wolf Uwe Reimold 《Meteoritics & planetary science》2003,38(8):1187-1197

Abstract— We studied unshocked and experimentally (at 12, 25, and 28 GPa, with 25, 100, 450, and 750°C pre‐shock temperatures) shock‐metamorphosed Hospital Hill quartzite from South Africa using cathodoluminescence (CL) images and spectroscopy and Raman spectroscopy to document systematic pressure or temperature‐related effects that could be used in shock barometry. In general, CL images of all samples show CL‐bright luminescent patchy areas and bands in otherwise nonluminescent quartz, as well as CL‐dark irregular fractures. Fluid inclusions appear dominant in CL images of the 25 GPa sample shocked at 750°C and of the 28 GPa sample shocked at 450°C. Only the optical image of our 28 GPa sample shocked at 25°C exhibits distinct planar deformation features (PDFs). Cathodoluminescence spectra of unshocked and experimentally shocked samples show broad bands in the near‐ultraviolet range and the visible light range at all shock stages, indicating the presence of defect centers on, e.g., SiO₄ groups. No systematic change in the appearance of the CL images was obvious, but the CL spectra do show changes between the shock stages. The Raman spectra are characteristic for quartz in the unshocked and 12 GPa samples. In the 25 and 28 GPa samples, broad bands indicate the presence of glassy SiO₂, while high‐pressure polymorphs are not detected. Apparently, some of the CL and Raman spectral properties can be used in shock barometry.  相似文献   

Readout Techniques for Drift and Low Frequency Noise Rejection in Infrared Arrays     

Gert Finger  Reinhold J. Dorn  Alan W. Hoffman  Hamid Mehrgan  Manfred Meyer  Alan F. M. Moorwood  Joerg Stegmeier 《Experimental Astronomy》2002,14(2):117-127

Three different methods are presented to subtract thermal drifts and low-frequency noise from the signal of infrared array. The first is dead pixels with open Indium bumps, the second is reference output as implemented on the Hawaii2 multiplexer, and the third is dark pixels to emulate reference cells having a capacity connected to the gate of the unit cell field-effect transistor (FET). The third method is the most effective and yields a reduction in readout noise from15.4–9.4 erms. A novel method will be described to extend this readout technique to the Aladdin 1 K × 1 K InSb array. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Paleoenvironment and sea-level change in the early Cretaceous Barents Sea—implications from near-shore marine sapropels     

Uwe?LangrockEmail author  Ruediger?Stein  Marcus?Lipinski  Hans-Jürgen?Brumsack 《Geo-Marine Letters》2003,23(1):34-42

The late Volgian (early "Boreal" Berriasian) sapropels of the Hekkingen Formation of the central Barents Sea show total organic carbon (TOC) contents from 3 to 36 wt%. The relationship between TOC content and sedimentation rate (SR), and the high Mo/Al ratios indicate deposition under oxygen-free bottom-water conditions, and suggest that preservation under anoxic conditions has largely contributed to the high accumulation of organic carbon. Hydrogen index values obtained from Rock-Eval pyrolysis are exceptionally high, and the organic matter is characterized by well-preserved type II kerogen. However, the occurrence of spores, freshwater algae, coal fragments, and charred land-plant remains strongly suggests proximity to land. Short-term oscillations, probably reflecting Milankovitch-type cyclicity, are superimposed on the long-term trend of constantly changing depositional conditions during most of the late Volgian. Progressively smaller amounts of terrestrial organic matter and larger amounts of marine organic matter upwards in the core section may have been caused by a continuous sea-level rise.  相似文献   

Patterns of heritability of decreased EROD activity and resistance to PCB 126-induced teratogenesis in laboratory-reared offspring of killifish (Fundulus heteroclitus) from a creosote-contaminated site in the Elizabeth River,VA, USA     

Meyer J  Di Giulio R 《Marine environmental research》2002,54(3-5):621-626

Killifish (Fundulus heteroclitus) from a highly contaminated site on the Elizabeth River are resistant to the acute toxicity and the cytochrome P4501A (CYP1A)-inducing activity of both the sediments from the site and chemically pure polycyclic aromatic hydrocarbons (PAHs). These effects are highly heritable for one generation, but heritable to a lesser degree by subsequent generations, in clean conditions in the laboratory. We show that offspring of this population of Elizabeth River killifish are also resistant to the teratogenicity and P4501A-inducing activity of PCB congener 126, a prototypical coplanar halogenated aromatic hydrocarbon (HAH). Furthermore, the pattern of greater resistance to acute toxicity and P4501A-inducing activity in the first generation and less in subsequent generations is also observed upon exposure to PCB-126.  相似文献   

Chalk shore platform erosion in the vicinity of sea defence structures and the impact of construction methods     

Uwe Dornbusch  David A. Robinson  Rendel B.G. Williams  Cherith A. Moses 《Coastal Engineering》2007

Erosion of the intertidal chalk platform in the vicinity of groynes and seawalls is evident to the naked eye along many stretches of the engineered coastline of southeast England, leading to undermining and eventually failure of these structures. However, quantification of the magnitude and spatial extent of the erosion has been difficult to date because of a lack of data about the past elevation of the platform. The application of softcopy photogrammetry makes it possible to recreate past platform elevations from historic air photographs and to compare these with elevations from modern air photographs. Coastal sea defence structures have been installed along the chalk coast east of Brighton at various dates over the past 70 years. During this period, the construction methods have changed from predominantly manual labour to a reliance on heavy machines. The analysis of erosion patterns around structures built since the 1970s using heavy machinery show that surface lowering is 4 to 25 times greater in the vicinity of these structures than across the platform as a whole. In contrast, there is no similar pattern of increased erosion around structures built using predominantly manual labour in the 1930s. A four fold increase in average surface lowering is found also along a vehicle trackway that crosses the mid platform. Depressions developed by enhanced lowering in the front of seawalls generate their own dynamic of increased erosion by trapping pebbles and cobbles that enhance the abrasion of the chalk through bedload transport under standing waves in front of the walls.  相似文献   

Observations of the Labrador Sea eddy field   总被引：2，自引：0，他引：2  

Jonathan M. Lilly  Peter B. RhinesFriedrich Schott  Kara LavenderJohn Lazier  Uwe SendEric D’Asaro 《Progress in Oceanography》2003,59(1):75-176

This paper is an observational study of small-scale coherent eddies in the Labrador Sea, a region of dense water formation thought to be of considerable importance to the North Atlantic overturning circulation. Numerical studies of deep convection emphasize coherent eddies as a mechanism for the lateral transport of heat, yet their small size has hindered observational progress. A large part of this paper is therefore devoted to developing new methods for identifying and describing coherent eddies in two observational platforms, current meter moorings and satellite altimetry. Details of the current and water mass structure of individual eddy events, as they are swept past by an advecting flow, can then be extracted from the mooring data. A transition is seen during mid-1997, with long-lived boundary current eddies dominating the central Labrador Sea year-round after this time, and convectively formed eddies similar to those seen in deep convection modeling studies apparent prior to this time. The TOPEX / Poseidon altimeter covers the Labrador Sea with a loose “net” of observations, through which coherent eddies can seem to appear and disappear. By concentrating on locating and describing anomalous events in individual altimeter tracks, a portrait of the spatial and temporal variability of the underlying eddy field can be constructed. The altimeter results reveal an annual “pulsation” of energy and of coherent eddies originating during the late fall at a particular location in the boundary current, pinpointing the time and place of the boundary current-type eddy formation. The interannual variability seen at the mooring is reproduced, but the mooring site is found to be within a localized region of greatly enhanced eddy activity. Notably lacking in both the annual cycle and interannual variability is a clear relationship between the eddies or eddy energy and the intensity of wintertime cooling. These eddy observations, as well as hydrographic evidence, suggest an active role for boundary current dynamics in shaping the energetics and water mass properties of the interior region.  相似文献   

The utility of the terms "bioavailability" and "bioavailable fraction" for metals   总被引：1，自引：0，他引：1  

Meyer JS 《Marine environmental research》2002,53(4):417-423

Because concentrations of total or dissolved metal usually are not good predictors of the acute toxicity of metals to aquatic biota (i.e. not all of the metal appears to be bioavailable), it has been tempting for researchers and regulators to attempt to identify a form or combination of forms of a metal that is the bioavailable fraction. But from geochemical, biological, and analytical perspectives, the term 'bioavailable fraction" is context-specific (i.e. not generalizable) and quantitatively elusive. Although the term "bioavailability" conveys a useful, general concept and should be retained in the aquatic-toxicology lexicon, the term "bioavailable fraction" should be avoided.  相似文献   

The GeoForschungsZentrum Potsdam/Groupe de Recherche de Gèodésie Spatiale satellite-only and combined gravity field models: EIGEN-GL04S1 and EIGEN-GL04C   总被引：2，自引：1，他引：1  

Christoph Förste  Roland Schmidt  Richard Stubenvoll  Frank Flechtner  Ulrich Meyer  Rolf König  Hans Neumayer  Richard Biancale  Jean-Michel Lemoine  Sean Bruinsma  Sylvain Loyer  Franz Barthelmes  Saskia Esselborn 《Journal of Geodesy》2008,82(6):331-346

The recent improvements in the Gravity Recovery And Climate Experiment (GRACE) tracking data processing at GeoForschungsZentrum Potsdam (GFZ) and Groupe de Recherche de Géodésie Spatiale (GRGS) Toulouse, the availability of newer surface gravity data sets in the Arctic, Antarctica and North-America, and the availability of a new mean sea surface height model from altimetry processing at GFZ gave rise to the generation of two new global gravity field models. The first, EIGEN-GL04S1, a satellite-only model complete to degree and order 150 in terms of spherical harmonics, was derived by combination of the latest GFZ Potsdam GRACE-only (EIGEN-GRACE04S) and GRGS Toulouse GRACE/LAGEOS (EIGEN-GL04S) mean field solutions. The second, EIGEN-GL04S1 was combined with surface gravity data from altimetry over the oceans and gravimetry over the continents to derive a new high-resolution global gravity field model called EIGEN-GL04C. This model is complete to degree and order 360 and thus resolves geoid and gravity anomalies at half- wavelengths of 55 km at the equator. A degree-dependent combination method has been applied in order to preserve the high accuracy from the GRACE satellite data in the lower frequency band of the geopotential and to form a smooth transition to the high-frequency information coming from the surface data. Compared to pre-CHAMP global high-resolution models, the accuracy was improved at a spatial resolution of 200 km (half-wavelength) by one order of magnitude to 3 cm in terms of geoid heights. The accuracy of this model (i.e. the commission error) at its full spatial resolution is estimated to be 15 cm. The model shows a reduced artificial meridional striping and an increased correlation of EIGEN-GL04C-derived geostrophic meridional currents with World Ocean Atlas 2001 (WOA01) data. These improvements have led to select EIGEN-GL04C for JASON-1 satellite altimeter data reprocessing. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Sediment oxygen profiles in a super-oxygenated antarctic lake     

Wharton RA  Meyer MA  McKay CP  Mancinelli RL  Simmons GM 《Limnology and oceanography》1994,39(4):839-853

Perennially ice-covered lakes are found in the McMurdo Dry Valleys of southern Victoria Land, Antarctica. In contrast to temperate lakes that have diurnal photic periods, antarctic (and arctic) lakes have a yearly photic period. An unusual feature of the antarctic lakes is the occurrence of O2 at supersaturated levels in certain portions of the water column. Here we report the first sediment O2 profiles obtained using a microelectrode from a perennially ice-covered antarctic lake. Sediment cores collected in January and October 1987 from Lake Hoare in Taylor Valley show oxygenation down to 15, and in some cases, 25 cm. The oxygenation of sediments several centimeters below the sediment-water interface is atypical for lake sediments and may be characteristic of perennially ice-covered lakes. There is a significant difference between the observed January and October sediment O2 profiles. Several explanations may account for the difference, including seasonality. A time-dependent model is presented which tests the feasibility of a seasonal cycle resulting from the long photoperiod and benthic primary production in sediments overlain by a highly oxygenated water column.  相似文献