Past glaciation in the tropics

Tropical glaciers are considered along three meridional profiles, for the Australasian sector, Africa and the Americas. Evaluated are the annual mean freezing level 0 °C, modern equilibrium line altitude MEL, and past equilibrium line altitude PEL. The calculation of 0 °C is based on a 1958–1997 global data set; MEL refers to estimates concerning the first half of the 20th century; and the timing of the PEL is not generally known. 0 °C stands around 4000–5000 m, with lower levels in the outer tropics. MEL is reached in the Australasian sector on four mountains, and in Africa on three mountains, near the Equator, near or above 0 °C. In the American cordilleras many peaks are still glaciated, above 0 °C, but in the arid southern tropical Andes even summits above 6000 m do not reach MEL. The PEL stands between 3000 m and 5000 m, high in the equatorial zone, but highest in the arid southern tropical Andes. The height difference between MEL and PEL is of order 1000 m, with regional differences. Deglaciation dates range between 15,000 and 8000 years BP, with later timing towards the higher elevations. This synopsis suggests priority targets for further research: morphological mapping and age determination in the High Atlas of Morocco; timing of deglaciation in the High Semyen of Ethiopia and the Altos de Cuchumatanes of Guatemala; exploration in the highlands of Lesotho and of the Dominican Republic; and glaciation in the arid southern tropical Andes.     

Marine ecosystem-based management in the Southern Cone of South America: Stakeholder perceptions and lessons for implementation

Ecosystem-based management (EBM) has recently received considerable attention. However, examples of empirical approaches to marine EBM are scarce. Therefore, empirical information on the presence of EBM elements within existing policies and the way they may provide settings and lessons for EBM implementation is timely. This study analyses stakeholders’ perceptions on the existence of EBM principles in current marine management practices and policies, and how they determine perceptions for success and satisfaction regarding coastal management within selected case studies drawn from four developing countries in the Southern Cone of South America. Patterns of response across study sites show that although EBM principles as such are not explicitly included in management/conservation plans, there are policies (mainly local), which generate conditions for more explicit inclusion of them. These are based on participatory bottom-up planning, place-based management and consensus reaching: all elements included within the theoretical literature on EBM implementation.     

GNSS processing at CODE: status report

Since May 2003, the Center for Orbit Determination in Europe (CODE), one of the analysis centers of the International GNSS Service, has generated GPS and GLONASS products in a rigorous combined multi-system processing scheme, which promises the best possible consistency of the orbits of both systems. The resulting products, in particular the satellite orbits and clocks, are easily accessible by the user community. In the first part of this article, we focus on the generation of the combined global products at CODE, where we put emphasis not only on accuracy, but also on completeness. We study the impact of GLONASS on the CODE products, and the benefit of using them. Last, but not least, we introduce AGNES (Automated GNSS Network for Switzerland), a regional tracking network of small extensions (roughly 400 km East–West, 200 km North–South), which consequently tracks all GNSS satellites and analyzes their measurements using the CODE products.     

A MATLAB toolbox for attitude determination with GPS multi-antenna systems

In this paper a MATLAB toolbox for determining the attitude of a rigid platform by means of multiple non-dedicated antennas using global positioning system is presented. The programs embedded in this toolbox cover the RINEX data analysis, single point positioning, differential positioning, coordinate conversion, attitude determination, and other auxiliary functions. After forming the baselines through double-differenced (carrier phase smoothed) code observables, the attitude parameters are obtained by applying the direct attitude computation and the least squares attitude estimation. The theoretical background is summarized, and some hints regarding the software implementation are given in the paper. Moreover, improvements yielding an expanded functionality are proposed.

Regular habitat switch as an important feeding strategy of an opportunistic seabird species at the interface between land and sea

During deteriorated prey availability, purely pelagic, specialised seabird species have to alter their feeding strategy by extending foraging radii and/or time spent at sea or reducing feeding intervals of chicks. In contrast, more generalised species such as the opportunistic black-headed gull (Larus ridibundus) breeding at the German North Sea coast, can be assumed to react on prey shortages by switching foraging habitats. The coastal zone of the German North Sea provides a rich habitat mosaic consisting of the offshore zone, tidal flats and terrestrial habitats. Thus, we expected distinct temporal and spatial patterns of habitat switch in accordance with prey availability and environmental constraints. We carried out ship-based and aerial surveys as well as dietary analyses and observations on flight activity. We found a significant switch from terrestrial to marine feeding sites both on a daily basis (related to tidal cycle) and over the whole breeding season. Most likely, the latter switch is the result of lower prey availability in the terrestrial habitats and an increasing quality (in terms of prey abundance and energy intake) of the marine area. While there was only moderate variability in habitat use among different years, we revealed significant differences in the diet of birds from different colonies. The high dietary plasticity and flexible feeding strategy, switching between terrestrial and marine prey is certainly of major importance for the success of an opportunistic avian top predator in a complex coastal zone. It is suggested that – compared to situations elsewhere – the number of breeding pairs of black-headed gulls in the German North Sea coast are still stable due to the switch of foraging habitats performed by individuals in this region.     

Structural uplift and ejecta thickness of lunar mare craters: New insights into the formation of complex crater rims

We investigate the elevated crater rims of lunar craters. The two main contributors to this elevation are a structural uplift of the preimpact bedrock and the emplacement of ejecta on top of the crater rim. Here, we focus on five lunar complex mare craters with diameters ranging between 16 and 45 km: Bessel, Euler, Kepler, Harpalus, and Bürg. We performed 5281 measurements to calculate precise values for the structural rim uplift and the ejecta thickness at the elevated crater rim. The average structural rim uplift for these five craters amounts to S_RU = 70.6 ± 1.8%, whereas the ejecta thickness amounts to E_T = 29.4 ± 1.8% of the total crater rim elevation. Erosion is capable of modifying the ratio of ejecta thickness to structural rim uplift. However, to minimize the impact of erosion, the five investigated craters are young, pristine craters with mostly preserved ejecta blankets. To quantify how strongly craters were enlarged by crater modification processes, we reconstructed the dimensions of the transient crater. The difference between the transient crater diameter and the final crater diameter can extend up to 11 km. We propose reverse faulting and thrusting at the final crater rim to be one of the main contributing factors of forming the elevated crater rim.     

The cosmic‐ray exposure history of the Twannberg iron meteorite (IIG)

The Twannberg iron meteorite is one out of only six members of the group IIG. The combined noble gas and radionuclide data obtained in this new systematic study indicate that Twannberg with its ~570 recently recovered specimens was a large object with a preatmospheric radius in the range of ~2 m, which corresponds to ~250 × 10³ kg. The cosmic‐ray exposure age for Twannberg is 182 ± 45 Ma. The most surprising result is the long terrestrial age of T_terr =  ka, which is unexpected considering the humid conditions in Switzerland. However, this age is in accord with glaciation events, indicating that the less shielded samples from Mt. Sujet were found close to the position of the original strewn field, whereas the samples from Gruebmatt and Twannbach, which are from more shielded positions, were glacially transported to the east–northeast during the second last ice age (185–130 ka ago) from an original position west of Mt. Sujet.     

Phytoscreening for Vinyl Chloride in Groundwater Discharging to a Stream

This study applies an optimized phytoscreening method to locate a chlorinated ethene plume discharging into a stream. To evaluate the conditions most suitable for successful phytoscreening, trees along the stream bank were monitored through different seasons with different environmental conditions and hence different uptake/loss scenarios. Vinyl chloride (VC) as well as cis‐dichloroethylene (cis‐DCE), trichloroethylene (TCE), and tetrachloroethylene (PCE) were detected in the trees, documenting that phytoscreening is a viable method to locate chlorinated ethene plumes, including VC, discharging to streams. The results reveal, that phytoscreening for VC is more sensitive to environmental conditions affecting transpiration than for the other chlorinated ethenes detected. Conditions leading to higher groundwater uptake by transpiration than contaminant loss by diffusion from the tree trunks are optimal (e.g., low relative humidity, plentiful hours of sunshine and an intermediate air temperature). Additionally, low precipitation prior to the sampling event is beneficial, as uptake of infiltrating precipitation dilutes the concentration in the trees. All chlorinated ethenes were sensitive to dilution by clean precipitation and in some months, this resulted in no detection of contaminants in the trees at all. Under optimal environmental conditions the tree cores allowed detection of chlorinated solvents and their metabolites in the underlying groundwater. Whereas, for less ideal conditions there was a risk of no detection of the more volatile VC. This study is promising for the future applicability of phytoscreening to locate shallow groundwater contamination with the degradation products of chlorinated solvents.