Europrobe seismic reflection profiling across the eastern Middle Urals and West Siberian Basin

New deep seismic reflection data provide images of the crust and uppermost mantle underlying the eastern Middle Urals and adjacent West Siberian Basin. Distinct truncations of reflections delineate the late-orogenic strike-slip Sisert Fault extending vertically to ∼28 km depth, and two gently E-dipping reflection zones, traceable to 15–18 km depth, probably represent normal faults associated with the opening of the West Siberian Basin. A possible remnant Palaeozoic subduction zone in the lower crust under the West Siberian Basin is visible as a gently SW-dipping zone of pronounced reflectivity truncated by the Moho. Continuity of shallow to intermediate-depth reflections suggest that Palaeozoic accreted island-arc terranes and overlying molasse sequences exposed in the hinterland of the Urals form the basement for Triassic and younger deposits in the West Siberian Basin. A highly reflective lower crust overlies a transparent mantle at about 43 km depth along the entire 100 km long seismic reflection section, suggesting that the lower crust and Moho below the eastern Middle Urals and West Siberian Basin have the same origin.     

Response of precipitation over Greenland and the adjacent ocean to North Pacific warm spells during Dansgaard–Oeschger stadials

ABSTRACT Palaeoceanographic reconstructions from the North Atlantic indicate massive ice breakouts from East Greenland near the onset of cold Dansgaard–Oeschger (D–O) stadials. In contrast to these coolings in the North Atlantic area, a new sea-surface temperature record reveals concomitant warm spells in the northern North Pacific. A sensitivity experiment with an atmospheric general circulation model is used to test the potential impact of sea-surface warmings by 3.5 °C in the North Pacific, on top of otherwise cold stadial climate conditions, on the precipitation regime over the Northern Hemisphere ice sheets. The model predicts a maximum response over East Greenland and the Greenland Sea, where a 40% increase in net annual snow accumulation occurs. This remote effect of North Pacific warm spells on the East Greenland snow-accumulation rate may play an important role in generating D–O cycles by rebuilding the ice lost during ice breakouts. In addition, the increased precipitation over the Greenland Sea may help to sustain the D–O stadial climate state.     

Neon produced by solar cosmic rays in ordinary chondrites

Solar‐cosmic‐ray‐produced Ne (SCR‐Ne), in the form of low cosmogenic ²¹Ne/²²Ne ratios (²¹Ne/²²Ne_cos <0.8), is more likely to be found in rare meteorite classes, like Martian meteorites, than in ordinary chondrites. This may be the result of a sampling bias: SCR‐Ne is better preserved in meteorites with small preatmospheric radii and these specimens are often only studied if they belong to unusual or rare classes. We measured He and Ne isotopic concentrations and nuclear tracks in 25 small unpaired ordinary chondrites from Oman. Most chondrites have been intensively heated during atmospheric entry as evidenced by the disturbed track records, the low ³He/²¹Ne ratios, the low ⁴He concentrations, and the high peak release temperatures. Concentration depth profiles indicate significant degassing; however, the Ne isotopes are mainly undisturbed. Remarkably, six chondrites have low ²¹Ne/²²Ne_cos in the range 0.711–0.805. Using a new physical model for the calculation of SCR production rates, we show that four of the chondrites contain up to ~20% of SCR‐Ne; they are analyzed in terms of preatmospheric sizes, cosmic ray exposure ages, mass ablation losses, and orbits. We conclude that SCR‐Ne is preserved, regardless of the meteorite class, in specimens with small preatmospheric radii. Sampling bias explains the predominance of SCR‐Ne in rare meteorites, although we cannot exclude that SCR‐Ne is more common in Martian meteorites than it is in small ordinary chondrites.     

PSF-fitting techniques for crowded field 3D spectroscopy

From a historical point of view, it was only through the advent of the CCD as a linear, high dynamic range panoramic detector that it became possible to overcome the source confusion problem for stellar photometry, e.g., in star clusters or nearby galaxies. The ability of accurately sampling the point-spread-function (PSF) in two dimensions and to use it as a template for fitting severely overlapping stellar images is of fundamental importance for crowded-field photometry, and has thus become the foundation for the determination of accurate color-magnitude diagrams of globular clusters and the study of resolved stellar populations in nearby galaxies. Analogous to CCDs, the introduction of integral field spectrographs has opened a new avenue for crowded-field 3D spectroscopy, which benefits in the same way from PSF-fitting techniques as CCD photometry does. This paper presents first experience with sampling the PSF in 3D spectroscopy, reviews the effects of atmospheric refraction, discusses background subtraction problems, and presents several science applications as obtained from observations with the PMAS instrument at Calar Alto Observatory.     

Geostrophic Wind, Gradient Wind, Thermal Wind And The Vertical Wind Profile – A Sample Analysis Within A Planetary Boundary Layer Over Arctic Sea-Ice

For the interpretation of many boundary-layer field experiments the geostrophic wind is needed as an external parameter. However, quite often and especially in remote areas this wind is not known at all or difficult to determine because there are not enough measurements of the surface pressure.Here it is shown how measurements carried out with the HELIPOD system, a helicopter-borne meteorological turbulence measuring system, may be used to evaluate the geostrophic wind. This is done by the analysis of the pressure field at different heights. An additional analysis of the temperature field in the same heights allows for the discussion of the quality of the derived geostrophic wind. An intercomparison with the vertical wind profile enables us to discuss the influence of the curvature of the isobars. From this, finally, also the gradient wind can be estimated.     

The Euro3D data format: A common FITS data format for integral field spectrographs

As integral field spectrographs have become more common around the world and in Europe in particular, the need for a common data format has been recognized. Here, we present the Euro3D format that is adapted as a post‐instrumentalsignature‐removal format for all instruments within the Euro3D network. It follows the FITS standard, and includes several extensions, all of them being binary FITS tables. This article is intended to give a comprehensive overview, but does not attempt to serve as a full definition document. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Estimating Runoff Using Hydro-Geodetic Approaches

Given the continuous decline in global runoff data availability over the past decades, alternative approaches for runoff determination are gaining importance. When aiming for global scale runoff at a sufficient temporal resolution and with homogeneous accuracy, the choice to use spaceborne sensors is only a logical step. In this respect, we take water storage changes from Gravity Recovery And Climate Explorer (grace) results and water level measurements from satellite altimetry, and present a comprehensive assessment of five different approaches for river runoff estimation: hydrological balance equation, hydro-meteorological balance equation, satellite altimetry with quantile function-based stage–discharge relationships, a rudimentary instantaneous runoff–precipitation relationship, and a runoff–storage relationship that takes time lag into account. As a common property, these approaches do not rely on hydrological modeling; they are either purely data driven or make additional use of atmospheric reanalyses. Further, these methods, except runoff–precipitation ratio, use geodetic observables as one of their inputs and, therefore, they are termed hydro-geodetic approaches. The runoff prediction skill of these approaches is validated against in situ runoff and compared to hydrological model predictions. Our results show that catchment-specific methods (altimetry and runoff–storage relationship) clearly outperform the global methods (hydrological and hydro-meteorological approaches) in the six study regions we considered. The global methods have the potential to provide runoff over all landmasses, which implies gauged and ungauged basins alike, but are still limited due to inconsistencies in the global hydrological and hydro-meteorological datasets that they use.