MEDUSA: The ExoMars experiment for in-situ monitoring of dust and water vapour

Dust and water vapour are fundamental components of the Martian atmosphere. In view of tracing the past environmental conditions on Mars, that possibly favoured the appearing of life forms, it is important to study the present climate and its evolution. Here dust and water vapour have (and have had) strong influence. Of major scientific interest is the quantity and physical, chemical and electrical properties of dust and the abundance of water vapour dispersed in the atmosphere and their exchange with the surface. Moreover, in view of the exploration of the planet with automated systems and in the future by manned missions, it is of primary importance to analyse the hazards linked to these environmental factors. The Martian Environmental Dust Systematic Analyser (MEDUSA) experiment, included in the scientific payload of the ESA ExoMars mission, accommodates a complement of sensors, based on optical detection and cumulative mass deposition, that aims to study dust and water vapour in the lower Martian atmosphere. The goals are to study, for the first time, in-situ and quantitatively, physical properties of the airborne dust, including the cumulative dust mass flux, the dust deposition rate, the physical and electrification properties, the size distribution of sampled particles and the atmospheric water vapour abundance versus time.     

Along-Coast Features of Bora-Related Turbulence

The along-coast, offshore turbulence structure of the Bora flow that occurred on 7 November 1999 during the Mesoscale Alpine Programme (MAP) Intensive Observation Period 15 is examined. In this analysis we employ the aircraft and dropsonde data obtained over the Adriatic Sea, where the turbulence structure is determined by estimating turbulent kinetic energy (TKE) and its dissipation rate along the flight legs. The turbulence characteristics of Bora in the lee of the Dinaric Alps is greatly influenced by the mesoscale Bora flow structure over the Adriatic Sea, which in the cross-wind direction features an interchange of jets and wakes related to mountain gaps and peaks. In order to establish the origin of turbulence, the Weather Research and Forecasting—Advanced Research WRF (WRF-ARW) numerical model is used and its results are compared to the measurements. All five TKE-prediction parametrization schemes available in the model show reasonable agreement with the measured values. Since these parametrization schemes do not have horizontal advection included, they suggest that the along-flight structure of the Bora turbulence is principally generated by the local vertical wind shear. Further evidence is needed to support this hypothesis.     

Potential climatic transitions with profound impact on Europe

We discuss potential transitions of six climatic subsystems with large-scale impact on Europe, sometimes denoted as tipping elements. These are the ice sheets on Greenland and West Antarctica, the Atlantic thermohaline circulation, Arctic sea ice, Alpine glaciers and northern hemisphere stratospheric ozone. Each system is represented by co-authors actively publishing in the corresponding field. For each subsystem we summarize the mechanism of a potential transition in a warmer climate along with its impact on Europe and assess the likelihood for such a transition based on published scientific literature. As a summary, the ‘tipping’ potential for each system is provided as a function of global mean temperature increase which required some subjective interpretation of scientific facts by the authors and should be considered as a snapshot of our current understanding.     

Characterising and visualizing spatio-temporal patterns in hourly precipitation records

We develop new techniques to summarise and visualise spatial patterns of coincidence in weather events such as more or less heavy precipitation at a network of meteorological stations. The cosine similarity measure, which has a simple probabilistic interpretation for vectors of binary data, is generalised to characterise spatial dependencies of events that may reach different stations with a variable time lag. More specifically, we reduce such patterns into three parameters (dominant time lag, maximum cross-similarity, and window-maximum similarity) that can easily be computed for each pair of stations in a network. Furthermore, we visualise such three-parameter summaries by using colour-coded maps of dependencies to a given reference station and distance-decay plots for the entire network. Applications to hourly precipitation data from a network of 93 stations in Sweden illustrate how this method can be used to explore spatial patterns in the temporal synchrony of precipitation events.     

Uplift and active tectonics of southern Albania inferred from incision of alluvial terraces

In Albania, the Osum and Vjoje rivers cross the active graben system and the active frontal thrust system of the Albanides. The effects of climatic and geodynamic forcing on the development of these two rivers were investigated by the means of field mapping, topographic surveying and absolute exposure-age dating. We established the chronology of terraces abandonment from the compilation of new dating (¹⁴C and in situ produced ¹⁰Be) and previously published data. We identified nine fluvial terraces units developed since Marine Isotope Stage 6 up to historic times. From this reconstituted history, we quantified the vertical uplift on a time scale shorter than the glacial climatic cycle. Regional bulging produces an overall increase of the incision rate from the west to the east that reaches a maximum value of 2.8 m/ka in the hinterland. Local pulses of incision are generated by activation of normal faults. The most active faults have a SW–NE trend and a vertical slip rate ranging from 1.8 to 2.2 m/ka. This study outlines the geodynamic control in the development of rivers flowing through the Albanides on the scale of 10³–10⁵ka.     

Geochemical investigation and characterisation of Neogene sediments from Valjevo-Mionica Basin (Serbia)

Sediments from the Valjevo-Mionica Basin of Neogene age were investigated in this study using different geochemical methods. The results of the inorganic part analyses suggest that during genesis of the sediments, the contents of Na₂O, B and As changed the most, which indicates that genesis of the investigated sediments was followed by climate changes and volcanic activity. The quantity of other macro- and microelements did not vary significantly. Investigations of the organic substance showed that it is native organic matter, which has been preserved to a significant extent, formed predominantly of algal precursor organisms, which provided good quality, deposited under reducing conditions and that it is at a low maturity level. As it has been established that genesis of the investigated sediments was mostly affected by an arid climate with more intensive salinity, the aim of this study, was also to identify the processes which were the most affected by the change in salinity, as well as biomarkers which are the most sensitive to this change. The results led to the conclusion that the salinity increase in the depositional environment had a primary effect on the preservation of the organic substance and the formation of the mineral searlesite. In addition, it was noticed that besides the Sq/nC₂₆ ratio, the parameters nC₁₇/nC₂₇, CPI and Ph/nC₁₈, are also significantly sensitive to salinity change in a depositional environment in case of immature organic substance deposited under reducing conditions.     

NanoSIMS: Insights to biogenicity and syngeneity of Archaean carbonaceous structures

NanoSIMS is a relatively new technology that is being applied to ancient carbonaceous structures to gain insight into their biogenicity and syngeneity. NanoSIMS studies of well preserved organic microfossils from the Neoproterozoic (0.8 Ga) Bitter Springs Formation have established elemental distributions in undisputedly biogenic structures. Results demonstrate that sub-micron scale maps of metabolically important elements (carbon [C], nitrogen [measured as CN ion], and sulfur [S]) can be correlated with kerogenous structures identified by optical microscopy. Spatial distributions of C, CN, and S in individual microfossils are nearly identical, and variations in concentrations of these elements parallel one another. In elemental maps, C, CN, and S appear as globules, aligned to form remnant walls or sheaths of fossiliferous structures. The aligned character and parallel variation of C and CN are the strongest indicators of biogenicity.Nitrogen/carbon atomic ratios (N/C) of spheroids, filaments, and remnants of a microbial mat suggest that N/C may reflect original biochemical differences, within samples of the same age and degree of alteration. Silicon (Si) and oxygen (O) maps illustrate that silica is intimately interspersed with organic carbon of the microfossils. This relationship is likely to reflect the process of silica permineralization of biological remains and thus may be an indicator of syngeneity of the fossilized material with the mineral matrix.The NanoSIMS characterization of Bitter Springs microfossils can be used as a baseline for interpreting less well preserved carbonaceous structures that might occur in older or even extraterrestrial materials. An example of such an application is provided by comparison of Bitter Springs results with NanoSIMS of Archaean carbonaceous structures from Western Australia, including a spheroid in the 3 Ga Farrel Quartzite and material in a secondary vein in the 3.43 Ga Strelley Pool Chert. Results reinforce a biogenic, syngenetic interpretation for the Archaean spheroid.NanoSIMS has several advantages in the study of ancient organic materials: the technique allows characterization of extremely small structures that are present in low concentrations; organic matter does not have to be isolated by acid treatment but can be analyzed in polished thin section; preparation is simple; samples are minimally altered during analysis; results provide sub-micron scale spatial distribution coupled with concentration information for at least five elements; the biologically important elements of carbon and nitrogen can be assessed; and the ability to study organic remains in situ permits petrographic assessment of spatial relationships between organic matter and mineral constituents. These advantages could be of significant benefit for interpretation of poorly preserved and fragmentary carbonaceous remains that might occur in some of Earth's oldest samples as well as in meteorites or extraterrestrial material brought to Earth in future planetary missions.     

Coupled trace element mobilisation and strain softening in quartz during retrograde fluid infiltration in dry granulite protoliths

This study focuses on the retrograde rheological and chemical evolution of quartz and the behaviour of quartzites during retrograde metamorphism following dry high grade metamorphism at 750°C, 7 kbar. SEM-CL and LA-HR-ICP-MS are applied to document quartz texture and chemistry, respectively. Four generations of quartz were distinguished by SEM-CL; Qz1, Qz2, Qz3 and Qz4. Qz1, brecciated and partly dissolved old grains, is enriched in B, Al and Ti when compared with the other types. Qz2, formed during brecciation and partial dissolution of Qz1, has low Al contents (<50 ppm) but, due to rutile inclusions, variable Ti contents when occurring in amphibolite (210–10 ppm) but more consistent values when occurring in quartzites (peak value 32 ppm). Qz3, dark grey luminescent quartz forming fluid migration channels (fluid pathways), has Ti < 5 ppm and Al contents below 10 ppm and B < 1 ppm. Qz4, comprises are group of quartz later than Qz3 filling micron thick cracks and pods with very low luminescent quartz, i.e. darker than Qz3. The textural and chemical evolution of quartz in our study is explained by two major influxes of aqueous fluids during regional uplift and retrogression. They facilitated rehydration and recrystallisation in the otherwise dry high grade quartzites. The first introduction of aqueous fluids was associated with brecciation of the high grade quartz (Qz1) and dissolution/precipitation of quartz (Qz2). Ti in quartz geothermometry (Wark and Watson, Contrib Mineral Petrol 152(6):637–652) gives 626°C in agreement with the retrograde PT-path deduced from phase diagrams. Later fluid influx associated with scapolitisation of amphibolite caused localised recrystallisation (Qz3) and alteration of biotite to muscovite along mm-wide fluid migration channels. During subsequent deformation, Qz3 deformed plastically and recovered by subgrain rotation recrystallisation (SGR), resulting in a reduction of grain size, whereas Qz1 quartz formed micro faults. Qz2 was plastic but did not experience SGR to the same degree as Qz3 quartz. Increased plasticity and recovery rates most likely relate to an increased H₂O fugacity and the depletion in trace elements of the quartz lattice by promoting strain softening processes dislocation climb and recovery. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Analysis of the Moberg et al. (2005) hemispheric temperature reconstruction

The Moberg et al. (Nature 433(7026):613–617, 2005. doi:10.1038/nature03265; M05) reconstruction of northern hemisphere temperature variations from proxy data has been criticised; the M05 method may artificially inflate low-frequency variance relative to reality. We test this assertion by undertaking several pseudoproxy experiments in three climate model simulations—one control run and two forced simulations that include several time-varying radiative forcings. The pseudoproxy series are designed to have the same variance spectra as the real M05 proxies, primarily to mimic the low-resolution character of several series. A simple composite-plus-scale (CPS) method is also analysed. In the CPS case all input data behave like annually resolved proxies. The spectral domain performance of both M05 and CPS is found to be dependent on the noise type and noise level in pseudoproxies, on the variance spectrum of the climate model simulation, and on the degree of data smoothing. CPS performs better than M05 in most investigated cases with the control run, but leads to deflated low-frequency variance in some cases. With M05, low-frequency variance tend to be inflated for the control run but not for one of the forced runs and only very slightly with the other forced simulation. Hence, the M05 approach does not routinely inflate low-frequency variance. In our experiment, the M05 approach performs better in the spectral domain than CPS when applied to forced climate model simulations. The results underscore the importance of evaluating the variance spectrum of climate reconstructions.     

An evaluation of Arctic cloud and radiation processes during the SHEBA year: simulation results from eight Arctic regional climate models

Eight atmospheric regional climate models (RCMs) were run for the period September 1997 to October 1998 over the western Arctic Ocean. This period was coincident with the observational campaign of the Surface Heat Budget of the Arctic Ocean (SHEBA) project. The RCMs shared common domains, centred on the SHEBA observation camp, along with a common model horizontal resolution, but differed in their vertical structure and physical parameterizations. All RCMs used the same lateral and surface boundary conditions. Surface downwelling solar and terrestrial radiation, surface albedo, vertically integrated water vapour, liquid water path and cloud cover from each model are evaluated against the SHEBA observation data. Downwelling surface radiation, vertically integrated water vapour and liquid water path are reasonably well simulated at monthly and daily timescales in the model ensemble mean, but with considerable differences among individual models. Simulated surface albedos are relatively accurate in the winter season, but become increasingly inaccurate and variable in the melt season, thereby compromising the net surface radiation budget. Simulated cloud cover is more or less uncorrelated with observed values at the daily timescale. Even for monthly averages, many models do not reproduce the annual cycle correctly. The inter-model spread of simulated cloud-cover is very large, with no model appearing systematically superior. Analysis of the co-variability of terms controlling the surface radiation budget reveal some of the key processes requiring improved treatment in Arctic RCMs. Improvements in the parameterization of cloud amounts and surface albedo are most urgently needed to improve the overall performance of RCMs in the Arctic.