Energy Balance Closure Using Eddy Covariance Above Two Different Land Surfaces and Implications for CO<Subscript>2</Subscript> Flux Measurements

Components of the surface energy balance of a mature boreal jack pine forest and a jack pine clearcut were analysed to determine the causes of the imbalance that is commonly observed in micrometeorological measurements. At the clearcut site (HJP02), a significant portion of the imbalance was caused by: (i) the overestimation of net radiation (R _n ) due to the inclusion of the tower in the field of view of the downward facing radiometers, and (ii) the underestimation of the latent heat flux (λE) due to the damping of high frequency fluctuations in the water vapour mixing ratio by the sample tube of the closed-path infrared gas analyzer. Loss of low-frequency covariance induced by insufficient averaging time as well as systematic advection of fluxes away from the eddy-covariance (EC) tower were discounted as significant issues. Spatial and temporal distributions of the total surface-layer heat flux (T), i.e. the sum of sensible heat flux (H) and λE, were well behaved and differences between the relative magnitudes of the turbulent fluxes for several investigated energy balance closure (C) classes were observed. Therefore, it can be assumed that micrometeorological processes that affected all turbulent fluxes similarly did not cause the variation in C. Turbulent fluxes measured at the clearcut site should not be forced to close the energy balance. However, at the mature forest site (OJP), loss of low-frequency covariance contributed significantly to the systematic imbalance when a 30-min averaging time was used, but the application of averaging times that were long enough to capture all of the low-frequency covariance was inadequate to resolve all of the high-frequency covariance. Although we found qualitative similarity between T and the net ecosystem exchange (NEE) of carbon dioxide (CO₂), forcing T to closure while retaining the Bowen ratio and applying the same factor to CO₂ fluxes (F _C ) cannot be generally recommended since it remains uncertain to what extent long wavelength contributions affect the relationship between T, F _C and C.     

LINET—An international lightning detection network in Europe

During the past years a VLF/LF lightning detection network (LINET) was developed at the University of Munich, which provides continuous data for both research and operational purposes. In particular, the network introduces five new features: a) total lightning capability: both cloud-to-ground strokes (CG) and cloud lightning (IC) are measured; b) low-amplitude reporting: weak lightning events from discharge channel with currents well below 5 kA are detected within the central part of the network, whereby IC events dominate; c) new 3D-discrimination: a time-of-arrival method is utilized to separate CG from IC with good reliability, provided that the sensor baseline does not exceed ~ 250 km; d) IC emission height: for each cloud event a height is determined which is thought to reflect the central region of the involved channel; and e) optimised location accuracy: due to precision and combined action of all influential network components, complemented by site-error corrections, the position accuracy of strokes reaches an average value as small as ~ 150 m, whereby false locations (‘outliers’) rarely occur. During international co-operations LINET has been deployed in four continents: Europe (initially Germany), South America (area of Bauru, Brazil), Australia (around Darwin), and Central Africa (Benin). Since the features quoted above could be verified in the tests, a 65-sensor network was established in Europe and started on May 1, 2006, in co-operation with the service company nowcast. LINET covers a wide area approximately from longitude − 10° to 25° to latitude 35° to 66°; it is available for scientific projects and officially utilized by the German Weather Service for operational purposes. Meanwhile, the network was extended by deployment of additional sites so that it comprises about 90 sensors in 17 countries.     

Major and trace elements in German bottled water,their regional distribution,and accordance with national and international standards

The market for mineral water has been growing steadily over the last few years. Germany is the country with the highest number of bottled mineral water brands (908 bottled water samples from 502 wells/brands were analyzed). The per capita consumption of mineral water in Germany in 2003 was 129 L. A wide range of values of one to seven orders of magnitude was determined for 71 elements in the bottled water samples analyzed by ICP-QMS, ICP-AES, IC, titration, photometric, conductometric and potentiometric methods. A comparison of the element concentrations and the legal limits for both bottled and tap water (EU, Germany, US EPA, WHO) shows that only 70% of the 908 mineral water samples fulfill the German and EU drinking water (i.e., tap water) regulations for all parameters (not including pH) for which action levels are defined. Nearly 5% of the bottled water samples not fulfill the German and EU regulations for mineral and table water. Comparison of our results with the current German and European action levels for mineral and table water shows that only 42 of the bottled water samples exceed the limits for one or more of the following elements: arsenic, nitrate, nitrite, manganese, nickel and barium concentrations. Ten of the bottled water samples contain uranium concentrations above the 10 μg/L recommended limit.     

Formation,fate and leaching of chloroform in coniferous forest soils

Chloroform is a common groundwater pollutant but also a natural compound in forest ecosystems. Leaching of natural chloroform from forest soil to groundwater was followed by regular analysis of soil air and groundwater from multilevel wells at four different sites in Denmark for a period of up to 4 a. Significant seasonal variation in chloroform was observed in soil air 0.5 m below surface ranging at one site from 120 ppb by volume in summer to 20 ppb during winter. With depth, the seasonal variation diminished gradually, ranging from 30 ppb in summer to 20 ppb during winter, near the groundwater table. Chloroform in the shallowest groundwater ranged from 0.5–1.5 μg L⁻¹ at one site to 2–5 μg L⁻¹ at another site showing no clear correlation with season. Comparing changes in chloroform in soil air versus depth with on-site recorded meteorological data indicated that a clear relationship appears between rain events and leaching of chloroform. Chloroform in top soil air co-varied with CO₂ given a delay of 3–4 weeks providing evidence for its biological origin. This was confirmed during laboratory incubation experiments which further located the fermentation layer as the most chloroform producing soil horizon. Sorption of chloroform to soils, examined using ¹⁴C–CHCl₃, correlated with organic matter content, being high in the upper organic rich soils and low in the deeper more minerogenic soils. The marked decrease in chloroform in soil with depth may in part be due to microbial degradation which was shown to occur at all depths by laboratory tests using ¹⁴C–CHCl₃.     

Submarine landslides at the eastern Sunda margin: observations and tsunami impact assessment

Our analysis of new bathymetric data reveals six submarine landslides at the eastern Sunda margin between central Java and Sumba Island, Indonesia. Their volumes range between 1 km3 in the Java fore-arc basin up to 20 km3 at the trench off Sumba and Sumbawa. We estimate the potential hazard of each event by modeling the corresponding tsunami and its run-up on nearby coasts. Four slides are situated remarkably close to the epicenter of the 1977 tsunamigenic Sumba M _w  = 8.3 earthquake. However, comparison of documented tsunami run-up heights and arrival times with our modeling results neither allows us to confirm nor can we falsify the hypothesis that the earthquake triggered these submarine landslides.     

Late Quaternary glaciation history of Isla de los Estados,southeasternmost South America

Isla de los Estados is a mountainous island southeast of Tierra del Fuego, in southernmost South America. Its central and eastern parts have an alpine topography, transected by U-shaped valleys, small, partly over-deepened fjords, and a multitude of abandoned cirques, all associated with extensive former local glaciations. Traces of glacial erosion generally reach 400–450 m a.s.l., and above that trimline a distinct sharp-edged nunatak derived landscape is present. The westernmost part of the island has a lower, more subdued topography, reflecting its “softer” geology but possibly also over-running and erosion by mainland-derived ice streams. The present study concentrated on glacigenic sediment sequences exposed along coastal erosional cliffs. A combination of OSL and ¹⁴C datings show that these sediments mostly date from the latest (Wisconsinan/Weichselian) glacial cycle, i.e. from the last ca. 100 ka with the oldest (glaciolacustrine) deposits possibly as old as 90–80 ka. The upper parts of overlying tills, with associated lateral and terminal moraines from glaciers that expanded onto an eustatically exposed dry shelf north of the island, date from the last global glacial maximum (LGM). Radiocarbon ages of peat and lake sediments indicate that deglaciation began 17–16 cal ka BP.     

Reply to “Reply to comments on defining biominerals and organominerals: Direct and indirect indicators of life [Perry et al., Sedimentary Geology, 201, 157–179]” by R.S. Perry and M.A. Sephton: [Sedimentary Geology 213 (2009) 156]

This is a reply to R.S. Perry and M.A. Sephton's “Reply to comments on defining biominerals and organominerals: direct and indirect indicators of life [Perry et al., Sedimentary Geology, 201, 157–179]” [Sedimentary Geology 213 (2009) 156].     

Single crystal U-Pb zircon age and Sr-Nd isotopic composition of impactites from the Bosumtwi impact structure, Ghana: Comparison with country rocks and Ivory Coast tektites

The 1.07?Myr old Bosumtwi impact structure (Ghana), excavated in 2.1-2.2?Gyr old supracrustal rocks of the Birimian Supergroup, was drilled in 2004. Here, we present single crystal U-Pb zircon ages from a suevite and two meta-graywacke samples recovered from the central uplift (drill core LB-08A), which yield an upper Concordia intercept age of ca. 2145?±?82?Ma, in very good agreement with previous geochronological data for the West African Craton rocks in Ghana. Whole rock Rb-Sr and Sm-Nd isotope data of six suevites (five from inside the crater and one from outside the northern crater rim), three meta-graywacke, and two phyllite samples from core LB-08A are also presented, providing further insights into the timing of the metamorphism and a possibly related isotopic redistribution of the Bosumtwi crater rocks. Our Rb-Sr and Sm-Nd data show also that the suevites are mixtures of meta-greywacke and phyllite (and possibly a very low amount of granite). A comparison of our new isotopic data with literature data for the Ivory Coast tektites allows to better constrain the parent material of the Ivory Coast tektites (i.e., distal impactites), which is thought to consist of a mixture of metasedimentary rocks (and possibly granite), but with a higher proportion of phyllite (and shale) than the suevites (i.e., proximal impactites). When plotted in a Rb/Sr isochron diagram, the sample data points (n?=?29, including literature data) scatter along a regression line, whose slope corresponds to an age of 1846?±?160?Ma, with an initial Sr isotope ratio of 0.703?±?0.002. However, due to the extensive alteration of some of the investigated samples and the lithological diversity of the source material, this age, which is in close agreement with a possible "metamorphic age" of ～?1.8-1.9?Ga tentatively derived from our U-Pb dating of zircons, is difficult to consider as a reliable metamorphic age. It may perhaps reflect a common ancient source whose Rb-Sr isotope systematics has not basically been reset on the whole rock scale during the Bosumtwi impact event, or even reflect another unknown geologic event.     

Iron in plagioclase in the Bushveld and Skaergaard intrusions: implications for iron contents in evolving basic magmas

The evolved, iron-rich rocks of the tholeiitic Bushveld and Skaergaard intrusions are similar in containing cumulus magnetite, ilmenite, plagioclase, clinopyroxene, apatite and olivine, and also orthopyroxenes/pigeonite in Bushveld. Here, we evaluate their liquid evolution trends using the total iron content in plagioclase determined by electron microprobe analyses. To aid this analysis a revised mass balance model for the liquid evolution of Skaergaard is presented. For plagioclase in the Upper Zone of Skaergaard it was previously demonstrated that total FeO increases from ~0.25 to ~0.45 wt% with differentiation and correlates inversely with An% [100 × Ca/(Na + Ca)]. The reverse trend is observed in two recently published datasets for Bushveld, showing that total FeO in plagioclase decreases upward through the magnetite-bearing Upper Zone from ~0.30 to ~0.15% and from ~0.40 to ~0.25% in the western and northern limbs, respectively, and correlates positively with An%. The partition coefficient of total iron between plagioclase and magma increases with oxidation and polymerisation in the liquid. Although Bushveld formed under slightly more oxidizing conditions than Skaergaard, differences in the partition coefficients cannot explain the two observed trends. We therefore conclude that the differentiation trends of the liquids subsequent to magnetite saturation were fundamentally different. The inferred liquid composition for Bushveld contained about 15 wt% total FeO at the level of magnetite-in, which is slightly less than the total FeO content of the subsequent cumulates. In contrast, the Skaergaard liquid contained more total FeO than the ensuing cumulates. As a result, in Bushveld residual liquids total FeO decreased after magnetite saturation, whereas in Skaergaard the residual liquids continued to become enriched in iron. This conclusion is corroborated by simple mass balance calculations between modelled residual liquids and extracted cumulate rocks. Despite the mineralogical similarities of evolved iron-rich rocks of Skaergaard and Bushveld, their liquid evolution trends were very different, and generalizations about the extent of iron enrichment in tholeiitic magmas should be avoided.     

The glaciotectonic deformation of Quaternary sediments by fault-propagation folding

Fault-propagation folding is an important yet seldom recognised structural style within sediments affected by glacier-induced deformation. Fault-propagation folds develop in the hanging wall of low angle thrust faults and compensate part of the slip along the fault. Field examples are recognised across northern Europe, in glaciotectonic complexes of north Germany, Wales and the Isle of Man. The recognition of the fault-propagation fold mechanism in glaciotectonic deformation is important because resultant structures are related to exactly the same phase of deformation (i.e. the same phase of ice advance), and thus play a critical role in analyses of the temporal and spatial evolution of glacier-induced deformation. Some field examples show monoclinal geometries that are in good agreement with predictions of trishear kinematic theory. The trishear approach is appropriate to model these structures because the structures analysed in the field and simulated below show characteristics that are compatible with fault-propagation folds that were produced by trishear kinematics. The curved forelimb and the monocline geometry of the fault-propagation folds fit to the trishear model. The occurrence of footwall synclines is also in good agreement with trishear kinematics. These synclines show the typical thickening of the strata in the hinge. With respect to the modelling output, most important factors for the structural evolution of the fault-propagation folds is the ramp angle of the thrust, the position of the tip line and the propagation-to-slip ratio along the fault. This fits to observations made by previous studies at large scale fault-propagation folds in fold-and-thrust belts.