ALBERT

Description: We present particle optical properties of stratospheric smoke layers observed with multiwavelength polarization Raman lidar over Punta Arenas (53.2∘ S, 70.9∘ W), Chile, at the southernmost tip of South America in January 2020. The smoke originated from the record-breaking bushfires in Australia. The stratospheric aerosol optical thickness reached values up to 0.85 at 532 nm in mid-January 2020. The main goal of this rapid communication letter is to provide first stratospheric measurements of smoke extinction-to-backscatter ratios (lidar ratios) and particle linear depolarization ratios at 355 and 532 nm wavelengths. These aerosol parameters are important input parameters in the analysis of spaceborne CALIPSO and Aeolus lidar observations of the Australian smoke spreading over large parts of the Southern Hemisphere in January and February 2020 up to heights of around 30 km. Lidar and depolarization ratios, simultaneously measured at 355 and 532 nm, are of key importance regarding the homogenization of the overall Aeolus (355 nm wavelength) and CALIPSO (532 nm wavelength) lidar data sets documenting the spread of the smoke and the decay of the stratospheric perturbation, which will be observable over the entire year of 2020. We found typical values and spectral dependencies of the lidar ratio and linear depolarization ratio for aged stratospheric smoke. At 355 nm, the lidar ratio and depolarization ratio ranged from 53 to 97 sr (mean 71 sr) and 0.2 to 0.26 (mean 0.23), respectively. At 532 nm, the lidar ratios were higher (75–112 sr, mean 97 sr) and the depolarization ratios were lower with values of 0.14–0.22 (mean 0.18). The determined depolarization ratios for aged Australian smoke are in very good agreement with respective ones for aged Canadian smoke, observed with lidar in stratospheric smoke layers over central Europe in the summer of 2017. The much higher 532 nm lidar ratios, however, indicate stronger absorption by the Australian smoke particles.

Description: Deeply rooted thrust zones are key features of tectonic processes and the evolution of mountain belts. Exhumed and deeply eroded orogens like the Scandinavian Caledonides allow us to study such systems from the surface. Previous seismic investigations of the Seve Nappe Complex have shown indications of a strong but discontinuous reflectivity of this thrust zone, which is only poorly understood. The correlation of seismic properties measured on borehole cores with surface seismic data can constrain the origin of this reflectivity. To this end, we compare seismic velocities measured on cores to in situ velocities measured in the borehole. For some intervals of the COSC-1 borehole, the core and downhole velocities deviate by up to 2 km s−1. These differences in the core and downhole velocities are most likely the result of microcracks mainly due to depressurization. However, the core and downhole velocities of the intervals with mafic rocks are generally in close agreement. Seismic anisotropy measured in laboratory samples increases from about 5 % to 26 % at depth, correlating with a transition from gneissic to schistose foliation. Thus, metamorphic foliation has a clear expression in seismic anisotropy. These results will aid in the evaluation of core-derived seismic properties of high-grade metamorphic rocks at the COSC-1 borehole and elsewhere.

Description: Turbulence velocity spectra are of high importance for the estimation of loads on wind turbines and other built structures, as well as for fitting measured turbulence values to turbulence models. Spectra generated from reconstructed wind vectors of Doppler beam swinging (DBS) wind lidars differ from spectra based on one-point measurements. Profiling wind lidars have several characteristics that cause these deviations, namely cross-contamination between the three velocity components, averaging along the lines of sight and the limited sampling frequency. This study focuses on analyzing the cross-contamination effect. We sample wind data in a computer-generated turbulence box to predict lidar-derived turbulence spectra for three wind directions and four measurement heights. The data are then processed with the conventional method and with the method of squeezing that reduces the longitudinal separation distances between the measurement locations of the different lidar beams by introducing a time lag into the data processing. The results are analyzed and compared to turbulence velocity spectra from field measurements with a Windcube V2 wind lidar and ultrasonic anemometers as reference. We successfully predict lidar-derived spectra for all test cases and found that their shape is dependent on the angle between the wind direction and the lidar beams. With conventional processing, cross-contamination affects all spectra of the horizontal wind velocity components. The method of squeezing improves the spectra to an acceptable level only for the case of the longitudinal wind velocity component and when the wind blows parallel to one of the lines of sight. The analysis of the simulated spectra described here improves our understanding of the limitations of turbulence measurements with DBS profiling wind lidar.

Description: The use of the noble gas radon (222Rn) as a tracer for different research studies, for example observation-based estimation of greenhouse gas (GHG) fluxes, has led to the need of high-quality 222Rn activity concentration observations with high spatial and temporal resolution. So far a robust metrology chain for these measurements is not yet available. A portable direct atmospheric radon monitor (ARMON), based on electrostatic collection of 218Po, is now running at Spanish stations. This monitor has not yet been compared with other 222Rn and 222Rn progeny monitors commonly used at atmospheric stations. A 3-month intercomparison campaign of atmospheric 222Rn and 222Rn progeny monitors based on different measurement techniques was realized during the fall and winter of 2016–2017 to evaluate (i) calibration and correction factors between monitors necessary to harmonize the atmospheric radon observations and (ii) the dependence of each monitor's response in relation to the sampling height and meteorological and atmospheric aerosol conditions. Results of this study have shown the following. (i) All monitors were able to reproduce the atmospheric radon variability on a daily basis. (ii) Linear regression fits between the monitors exhibited slopes, representing the correction factors, between 0.62 and 1.17 and offsets ranging between −0.85 and −0.23 Bq m−3 when sampling 2 m above ground level (a.g.l.). Corresponding results at 100 m a.g.l. exhibited slopes of 0.94 and 1.03 with offsets of −0.13 and 0.01 Bq m−3, respectively. (iii) No influence of atmospheric temperature and relative humidity on monitor responses was observed for unsaturated conditions at 100 m a.g.l., whereas slight influences (order of 10−2) of ambient temperature were observed at 2 m a.g.l. (iv) Changes in the ratio between 222Rn progeny and 222Rn monitor responses were observed under very low atmospheric aerosol concentrations. Results also show that the new ARMON could be useful at atmospheric radon monitoring stations with space restrictions or as a mobile reference instrument to calibrate in situ 222Rn progeny monitors and fixed radon monitors. In the near future a long-term comparison study between ARMON, HRM, and ANSTO monitors would be useful to better evaluate (i) the uncertainties of radon measurements in the range of a few hundred millibecquerels per cubic meter to a few becquerels per cubic meter and (ii) the response time correction of the ANSTO monitor for representing fast changes in the ambient radon concentrations.

Description: Low ozone and high water vapour mixing ratios are common features in the Asian summer monsoon (ASM) anticyclone; however, low ozone and low water vapour values were observed near the tropopause over Kunming, China, within the ASM using balloon-borne measurements performed during the SWOP (sounding water vapour, ozone, and particle) campaign in August 2009 and 2015. Here, we investigate low ozone and water vapour signatures in the upper troposphere and lower stratosphere (UTLS) using FengYun-2D, FengYun-2G, and Aura Microwave Limb Sounder (MLS) satellite measurements and backward trajectory calculations. Trajectories with kinematic and diabatic vertical velocities were calculated using the Chemical Lagrangian Model of the Stratosphere (CLaMS) trajectory module driven by both ERA-Interim and ERA5 reanalysis data. All trajectory calculations show that air parcels with low ozone and low water vapour values in the UTLS over Kunming measured by balloon-borne instruments originate from the western Pacific boundary layer. Deep convection associated with tropical cyclones over the western Pacific transports ozone-poor air from the marine boundary layer to the cold tropopause region. Subsequently, these air parcels are mixed into the strong easterlies on the southern side of the Asian summer monsoon anticyclone. Air parcels are dehydrated when passing the lowest temperature region (

Description: Deep-sea mining for polymetallic nodules is expected to have severe environmental impacts because not only nodules but also benthic fauna and the upper reactive sediment layer are removed through the mining operation and blanketed by resettling material from the suspended sediment plume. This study aims to provide a holistic assessment of the biogeochemical recovery after a disturbance event by applying prognostic simulations based on an updated diagenetic background model and validated against novel data on microbiological processes. It was found that the recovery strongly depends on the impact type; complete removal of the reactive surface sediment reduces benthic release of nutrients over centuries, while geochemical processes after resuspension and mixing of the surface sediment are near the pre-impact state 1 year after the disturbance. Furthermore, the geochemical impact in the DISturbance and reCOLonization (DISCOL) experiment area would be mitigated to some degree by a clay-bound Fe(II)-reaction layer, impeding the downward diffusion of oxygen, thus stabilizing the redox zonation of the sediment during transient post-impact recovery. The interdisciplinary (geochemical, numerical and biological) approach highlights the closely linked nature of benthic ecosystem functions, e.g. through bioturbation, microbial biomass and nutrient fluxes, which is also of great importance for the system recovery. It is, however, important to note that the nodule ecosystem may never recover to the pre-impact state without the essential hard substrate and will instead be dominated by different faunal communities, functions and services.

Description: Here we describe the design and performance of a new water cluster chemical ionization–atmospheric pressure interface time-of-flight mass spectrometer (CI-APi-TOF). The instrument selectively measures trace gases with high proton affinity such as ammonia and dimethylamine, which are important for atmospheric new particle formation and growth. Following the instrument description and characterization, we demonstrate successful measurements at the CERN CLOUD (Cosmics Leaving OUtdoor Droplets) chamber where very low ammonia background levels of ∼4 pptv were achieved (at 278 K and 80 % RH). The limit of detection of the water cluster CI-APi-TOF is estimated to be ∼0.5 pptv for ammonia. Although no direct calibration was performed for dimethylamine (DMA), we estimate its detection limit is at least 3 times lower. Due to the short ion–molecule reaction time and high reagent ion concentrations, ammonia mixing ratios up to at least 10 ppbv can be measured with the instrument without significant reagent ion depletion. Besides the possibility to measure compounds like ammonia and amines (dimethylamine), we demonstrate that the ionization scheme is also suitable for the measurement of trace gases containing iodine. During CLOUD experiments to investigate the formation of new particles from I2, many different iodine-containing species were identified with the water cluster CI-APi-TOF. The compounds included iodic acid and neutral molecular clusters containing up to four iodine atoms. However, the molecular structures of the iodine-containing clusters are ambiguous due to the presence of an unknown number of water molecules. The quantification of iodic acid (HIO3) mixing ratios is performed from an intercomparison with a nitrate CI-APi-TOF. Using this method the detection limit for HIO3 can be estimated as 0.007 pptv. In addition to presenting our measurements obtained at the CLOUD chamber, we discuss the applicability of the water cluster Ci-APi-TOF for atmospheric measurements.

Description: The southern Black Forest was temporarily covered by a ∼1000 km2 large ice cap during the Late Pleistocene. However, during the last glaciation maximum in the Alps the atmospheric circulation over Europe was presumably characterised by the advection of humid air masses from the Mediterranean Sea. As a consequence, the ice cap of the Black Forest was likely in a leeward position due to its location north of the Alps. This raises the question of whether it reached its last maximum extent simultaneously with the glaciers in the Alps. As modern dating techniques have hitherto not been applied to the southern Black Forest, the timing of the last local glaciation maximum remains poorly constrained. As a first step towards an independent regional glacier chronology, we present a critical re-examination of glacial landforms in the area north-west of the highest summit of the Black Forest (Feldberg, 1493 m a.s.l.). It relies on both the analysis of remote sensing data and field mapping. The review of previous studies highlights important disagreements regarding the location of ice-marginal positions and their correlation. In addition, our findings challenge earlier studies on the glaciation of the Black Forest: some previously described ice-marginal positions could not be confirmed, whereas some of the newly identified moraines are described for the first time. This highlights the need for detailed geomorphological investigations prior to the application of geochronological methods. A multi-ridged series of terminal moraines in one of the studied valleys, Sankt Wilhelmer Tal, is proposed as the main target for future dating. Due to discrepancies with earlier studies, future efforts should reinvestigate other key areas related to the last glaciation of the southern Black Forest.

Description: Gross primary productivity (GPP), the CO2 uptake by means of photosynthesis, cannot be measured directly on the ecosystem scale but has to be inferred from proxies or models. One newly emerged proxy is the trace gas carbonyl sulfide (COS). COS diffuses into plant leaves in a fashion very similar to CO2 but is generally not emitted by plants. Laboratory studies on leaf level gas exchange have shown promising correlations between the leaf relative uptake (LRU) of COS to CO2 under controlled conditions. However, in situ measurements including daily to seasonal environmental changes are required to test the applicability of COS as a tracer for GPP at larger temporal scales. To this end, we conducted concurrent ecosystem-scale CO2 and COS flux measurements above an agriculturally managed temperate mountain grassland. We also determined the magnitude and variability of the soil COS exchange, which can affect the LRU on an ecosystem level. The cutting and removal of the grass at the site had a major influence on the soil flux as well as the total exchange of COS. The grassland acted as a major sink for CO2 and COS during periods of high leaf area. The sink strength decreased after the cuts, and the grassland turned into a net source for CO2 and COS on an ecosystem level. The soil acted as a small sink for COS when the canopy was undisturbed but also turned into a source after the cuts, which we linked to higher incident radiation hitting the soil surface. However, the soil contribution was not large enough to explain the COS emission on an ecosystem level, hinting at an unknown COS source possibly related to dead plant matter degradation. Over the course of the season, we observed a concurrent decrease in CO2 and COS uptake on an ecosystem level. With the exception of the short periods after the cuts, the LRU under high-light conditions was rather stable and indicated a high correlation between the COS flux and GPP across the growing season.

Description: The article examines how to adapt the global production network (GPN) approach to situations of natural resource extraction. Based on an integration of a political ecology perspective into GPN research, we exemplarily apply the GPN framework to the primary sector. Based on extensive qualitative fieldwork regarding Argentine lithium mining and Brazilian soy agribusiness we illustrate that particularly a political ecological environmental perspective allows for a more nuanced and critical analysis of ambiguous local development outcomes. While from a purely economic development perspective in both cases the economic activity (integrated into GPNs) is celebrated as an imperative economic growth driver, our framework helps identify the emergence of unilateral dependencies, a decline of social autonomy and an unequal distribution of environmental risks.