Carbon,hydrogen, and oxygen isotope studies of the regional metamorphic complex at Naxos,Greece

At Naxos, Greece, a migmatite dome is surrounded by schists and marbles of decreasing metamorphic grade. Sillimanite, kyanite, biotite, chlorite, and glaucophane zones are recognized at successively greater distances from the migmatite dome. Quartz-muscovite and quartz-biotite oxygen isotope and mineralogie temperatures range from 350 to 700°C.The metamorphic complex can be divided into multiple schist-rich (including migmatites) and marblerich zones. The δ¹⁸O values of silicate minerals in migmatite and schist units and quartz segregations in the schist-rich zones decrease with increase in metamorphic grades. The calculated δ¹⁸O_H2O values of the metamorphic fluids in the schist-rich zones decrease from about 15‰ in the lower grades to an average of about 8.5‰ in the migmatite.The δD values of OH-minerals (muscovite, biotite, chlorite, and glaucophane) in the schist-rich zones also decrease with increase in grade. The calculated δD_H2O values for the metamorphic fluid decrease from ?5‰ in the glaucophane zone to an average of about ?70‰ in the migmatite. The δD values of water in fluid inclusions in quartz segregations in the higher grade rocks are consistent with this trend.Theδ¹⁸O values of silicate minerals and quartz segregations in marble-rich zones are usually very large and were controlled by exchange with the adjacent marbles. The δD values of the OH minerals in some marble-rich zones may reflect the value of water contained in the rocks prior to metamorphism.Detailed data on 20 marble units show systematic variations of δ¹⁸O values which depend upon metamorphic grade. Below the 540°C isograd very steep δ¹⁸O gradients at the margins and large δ¹⁸O values in the interior of the marbles indicate that oxygen isotope exchange with the adjacent schist units was usually limited to the margins of the marbles with more exchange occurring in the stratigraphic bottom than in the top margins. Above the 540°C isograd lower δ¹⁸O values occur in the interior of the marble units reflecting a greater degree of recrystallization and the occurrence of Ca-Mg-silicates.Almost all the δ¹³C values of the marbles are in the range of unaltered marine limestones. Nevertheless, the δ¹³C values of most marble units show a general correlation with δ¹⁸O values.The $\text{CO}{}_2\text{H}{}_2\text{O}$ mole ratio of fluid inclusions in quartz segregations range from 0.01 to 2. Theδ¹³C values of the CO₂ range from ?8.0 to 3.6‰ and indicate that at some localities CO₂ in the metamorphic fluid was not in carbon isotopic equilibrium with the marbles.     

Stable isotope coherence in the earlywood and latewood of tree-line conifers

Annually resolved and replicated tree-ring stable isotope series have the potential to reconstruct growing season environmental parameters over multi-millennial timescales. As this archive may require only minimal statistical detrending, it has the potential to preserve a large portion of low frequency climate signals. To date, many studies have utilised only the latewood portion of the tree ring, in an attempt to minimize carry-over effects from previous year reserves and maximise the annual nature of the climate signal preserved. However, the old trees from tree-line locations, necessary to build long chronologies, often display narrow ring-widths (< 0.5 mm), making accurate earlywood–latewood separation difficult and particular time consuming. The resulting samples may also be too small for efficient cellulose purification or multiple isotopic determinations. As photosynthates from the current year are predominantly used in conifer ring formation at marginal sites with short growing seasons, latewood separation may not be especially advantageous in determining a useful climate signal and therefore unnecessary where resources are limited. To test this hypothesis, Scots pine from Northern Norway and European larch from the Swiss Alps are used. Both sites are tree-line locations where growth is predominantly temperature limited. Tree rings were cut and extracted to cellulose for both the earlywood and latewood of each annual growth ring and stable carbon isotope ratios were measured. Our results demonstrate a very high common carbon isotope signal between earlywood and latewood in both species (r_larch = 0.68 and r_pine = 0.79), which also show high correlations with summer temperature over the investigated period (AD 1980–2004 for larch and AD 1929–1978 for pine). High turnover rates and small reserve pools at these tree-line locations may account for these high common signals. These results suggest that for European tree-line conifers, the separation of earlywood from latewood is unnecessary to resolve an annual isotopic signal and make a reliable climate calibration. Using the whole ring may provide additional analytical advantages and consequently even improve climate calibrations.     

A 520 year record of summer sunshine for the eastern European Alps based on stable carbon isotopes in larch tree rings

A 520-year stable carbon isotope chronology from tree ring cellulose in high altitude larch trees (Larix decidua Mill.), from the eastern European Alps, correlates more strongly with summer temperature than with summer sunshine hours. However, when instrumental records of temperature and sunshine diverge after AD1980, the tree ring time series does not follow warming summer temperatures but more closely tracks summer sunshine trends. When the tree ring stable carbon isotope record is used to reconstruct summer temperature the reconstruction is not robust. Reconstructed temperatures prior to the twentieth century are higher than regional instrumental records, and the evolution of temperature conflicts with other regional temperature reconstructions. It is concluded that sunshine is the dominant control on carbon isotope fractionation in these trees, via the influence of photosynthetic rate on the internal partial pressure of CO₂, and that high summer (July–August) sunshine hours is a suitable target for climate reconstruction. We thus present the first reconstruction of summer sunshine for the eastern Alps and compare it with the regional temperature evolution.     

Automatic optimized discovery, creation and processing of astronomical catalogs

We present the design of a novel way of handling astronomical catalogs in Astro-WISE in order to achieve the scalability required for the data produced by large scale surveys. A high level of automation and abstraction is achieved in order to facilitate interoperation with visualization software for interactive exploration. At the same time flexibility in processing is enhanced and data is shared implicitly between scientists. This is accomplished by using a data model that primarily stores how catalogs are derived; the contents of the catalogs are only created when necessary and stored only when beneficial for performance. Discovery of existing catalogs and creation of new catalogs is done through the same process by directly requesting the final set of sources (astronomical objects) and attributes (physical properties) that is required, for example from within visualization software. New catalogs are automatically created to provide attributes of sources for which no suitable existing catalogs can be found. These catalogs are defined to contain the new attributes on the largest set of sources the calculation of the attributes is applicable to, facilitating reuse for future data requests. Subsequently, only those parts of the catalogs that are required for the requested end product are actually processed, ensuring scalability. The presented mechanisms primarily determine which catalogs are created and what data has to be processed and stored: the actual processing and storage itself is left to existing functionality of the underlying information system.     

Vegetation impacts soil water content patterns by shaping canopy water fluxes and soil properties

Soil water content is a key variable for biogeochemical and atmospheric coupled processes. Its small‐scale heterogeneity impacts the partitioning of precipitation (e.g., deep percolation or transpiration) by triggering threshold processes and connecting flow paths. Forest hydrologists frequently hypothesized that throughfall and stemflow patterns induce soil water content heterogeneity, yet experimental validation is limited. Here, we pursued a pattern‐oriented approach to explore the relationship between net precipitation and soil water content. Both were measured in independent high‐resolution stratified random designs on a 1‐ha temperate mixed beech forest plot in Germany. We recorded throughfall (350 locations) and stemflow (65 trees) for 16 precipitation events in 2015. Soil water content was measured continuously in topsoil and subsoil (210 profiles). Soil wetting was only weakly related to net precipitation patterns. The precipitation‐induced pattern quickly dissipates and returns to a basic pattern, which is temporally stable. Instead, soil hydraulic properties (by the proxy of field capacity) were significantly correlated with this stable soil water content pattern, indicating that soil structure more than net precipitation drives soil water content heterogeneity. Also, both field capacity and soil water content were lower in the immediate vicinity of tree stems compared to further away at all times, including winter, despite stemflow occurrence. Thus, soil structure varies systematically according to vegetation in our site. We conclude that enhanced macroporosity increases gravity‐driven flow in stem proximal areas. Therefore, although soil water content patterns are little affected by net precipitation, the resulting soil water fluxes may strongly be affected. Specifically, this may further enhance the channelling of stemflow to greater depth and beyond the rooting zone.     

Paleo-Indian procurement of Camelops on the northwestern plains

Camelops have been recorded in a number of Paleo-Indian sites that lack evidence of past procurement methods. Recently, two occurrences of Camelops remains have been recorded in Paleo-Indian animal kills in Wyoming. One kill situation was in a Hell Gap cultural context that produced remains of a single Camelops taken along with about 100 bison in a parabolic sand dune trap. The other Camelops was in a Clovis cultural context and deals with a single animal believed to have been taken in an arroyo trap that was used to take bison at several Paleo-Indian time periods. Identification of geomorphic features involved in these kill sites offers a basis for beginning to interpret Paleo-Indian camel procurement methods.     

Prediction of river temperature surges is dependent on precipitation method

Urban river systems are particularly sensitive to precipitation‐driven water temperature surges and fluctuations. These result from rapid heat transfer from low‐specific heat capacity surfaces to precipitation, which can cause thermally polluted surface run‐off to enter urban streams. This can lead to additional ecological stress on these already precarious ecosystems. Although precipitation is a first‐order driver of hydrological response, water temperature studies rarely characterize rain event dynamics and typically rely on single gauge data that yield only partial estimates of catchment precipitation. This paper examines three precipitation measuring methods (a statutory automatic weather station, citizen science gauges, and radar estimates) and investigates relationships between estimated rainfall inputs and subhourly surges and diurnal fluctuations in urban river water temperature. Water temperatures were monitored at 12 sites in summer 2016 in the River Rea, in Birmingham, UK. Generalized additive models were used to model the relationship between subhourly water temperature surges and precipitation intensity and subsequently the relationship between daily precipitation totals and standardized mean water temperature. The different precipitation measurement sources give highly variable precipitation estimates that relate differently to water temperature fluctuations. The radar catchment‐averaged method produced the best model fit (generalized cross‐validation score [GCV] = 0.30) and was the only model to show a significant relationship between water temperature surges and precipitation intensity (P < 0.001, R² = 0.69). With respect to daily metrics, catchment‐averaged precipitation estimates from citizen science data yielded the best model fit (GCV score = 0.20). All precipitation measurement and calculation methods successfully modelled the relationship between standardized mean water temperature and daily precipitation (P < 0.001). This research highlights the potential for the use of alternative precipitation datasets to enhance understanding of event‐based variability in water quality studies. We conclude by recommending the use of spatially distributed precipitation data operating at high spatial (<1 km²) and temporal (<15 min) resolutions to improve the analysis of event‐based water temperature and water quality studies.     

Modelling late-holocene snow-avalanche activity: Incorporating a new approach to lichenometry

Where snow avalanches descend steeply into large rivers, displacing bedload, avalanche boulder-ramparts may accumulate, retaining a record of late-Holocene snow-avalanche frequency. The age frequency of surface boulders on 12 such features in upper Jostedalen, southern Norway, was investigated using the size-frequency distribution of lichens. A model was constructed to simulate the influence of variations in avalanche frequency since AD 1325 on lichen-size-frequency distributions. Using this modelling approach it is not possible to define a unique pattern of avalanche activity to account for the observed lichen-size-frequency distributions, but it is possible to place strict limits on the range of scenarios that are acceptable. The results suggest that maximum avalanche activity occurred during the 19th century, after the peak of the Little Ice Age. This conflicts with historical records of avalanche damage to property at lower altitude in nearby valleys, which may reflect avalanche activity only during a short period of extreme climatic conditions. Close agreement between the records of snow avalanches and debris flows suggests that both reflect periods of high winter snowfall and rapid spring melting rather than low temperature. Future ‘greenhouse warming’ may therefore result in increased avalanche activity in southern Norway.