Runoff- and erosion-driven transport of cattle slurry: linking molecular tracers to hydrological processes Biogeosciences DOI 10.5194/bg-13-551-2016 1 February 2016 Our interdisciplinary research brings together methodologies from hydrology, soil science and biogeochemistry to address key questions about the transport of cattle slurry in the environment. The paper provides a novel approach to trace dissolved and particulate components of cattle slurry through an experimental hillslope system. This work provides one of the first examples of using biomarkers to assess the effects of slope gradient and rainfall intensity on the movement of slurry derived-OM. Read more
Integrating a mini catchment with mulching for soil water management in a sloping jujube orchard on the semiarid Loess Plateau of China Solid Earth DOI 10.5194/se-7-167-2016 1 February 2016 We integrated fish-scale pits with mulching to test whether this integration could improve soil water conservation. The results showed that integrating fish-scale pits with mulching could conserve significantly more soil water by increasing infiltration and decreasing evaporation, and showed greater soil water storage and degree of soil water compensation compared to fish-scale pits alone. In addition, jujube branches exerted better mulching effects than maize straw. Read more
Does the Budyko curve reflect a maximum-power state of hydrological systems? A backward analysis Hydrology and Earth System Sciences DOI 10.5194/hess-20-479-2016 28 January 2016 We derived mathematical formulations of relations between relative wetness and gradients driving run-off and evaporation for a one-box model such that, when conductances are optimized with the maximum power principle, the model leads exactly to a point on the Budyko curve. With dry spells and dynamics in actual evaporation added, the model compared well with catchment observations without calibrating any parameter. The maximum-power principle may thus be used to derive the Budyko curve. Read more
Efficacy of bedrock erosion by subglacial water flow Earth Surface Dynamics DOI 10.5194/esurf-4-125-2016 27 January 2016 In regions formerly, or currently, covered by glaciers, landscapes have largely been shaped by glaciers. Glaciers erode bedrock through three main mechanisms: abrasion, quarrying, and subglacial meltwater erosion (SME). The latter, however, remains enigmatic. We present the first numerical modelling study of bedrock erosion by subglacial water and find that SME is negligible compared to abrasion and quarrying across the glacier, but its localization can explain the formation of bedrock channels. Read more
Trail impact monitoring in Rocky Mountain National Park, USA Solid Earth DOI 10.5194/se-7-115-2016 26 January 2016 Rocky Mountain National Park is one of the most visited national parks in the United States. 95% of the park is managed as wilderness. This paper examines the impacts of trampling on the vegetation and soil along selected trails. Trail widening and soil loss are the most visible types of trail degradation. Insights into the influence of different factors (use level, topography) can lead to the selection of appropriate management measures to avoid or minimize negative consequences. Read more
CO2 emission and structural characteristics of two calcareous soils amended with municipal solid waste and plant residue Solid Earth DOI 10.5194/se-7-105-2016 26 January 2016 Following the application of organic amendment treatments, the increased organic carbon and total porosity values, as compared to the control treatment, were greater in the loamy sand soil than in the clay loam soil. Moreover, compared to the microbial respiration of control plots, the application of municipal solid waste resulted in higher levels of microbial respiration from the clay loam soil than from the loamy sand soil, whereas the reverse was found for alfalfa residue. Read more
Modeling global water use for the 21st century: the Water Futures and Solutions (WFaS) initiative and its approaches Geoscientific Model Development DOI 10.5194/gmd-9-175-2016 21 January 2016 The Water Futures and Solutions (WFaS) initiative coordinates its work with other ongoing scenario efforts for the sake of establishing a consistent set of new global water scenarios based on the shared socio-economic pathways (SSPs) and the representative concentration pathways (RCPs). The WFaS “fast-track” assessment uses three global water models, H08, PCR-GLOBWB, and WaterGAP, to provide the first multi-model analysis of global water use for the 21st century based on the water scenarios. Read more
Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 2: The IGRF Annales Geophysicae DOI 10.5194/angeo-34-67-2016 19 January 2016 The method of electric field mapping along geomagnetic field lines, derived in an accompanying paper, is applied to the International Geomagnetic Reference Field. Formulae for the geomagnetic field gradient tensor are derived and these are used in a software package developed to map the electric field. A number of examples are presented illustrating the method. The method will be of importance in conjugate studies of ionospheric convection when the external magnetic field can be neglected. Read more
Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 1: Elementary models Annales Geophysicae DOI 10.5194/angeo-34-55-2016 19 January 2016 This paper introduces a new method for mapping electric fields in the magnetosphere along geomagnetic field lines. This is important for conjugate studies of electric fields measured in the ionosphere by SuperDARN radars, and at spacecraft carrying electric field probes. First elementary methods in a dipole field are reviewed and then the theory of of a new method described for general magnetic field models. The method is tested in a dipole model with a Harris magnetotail field. Read more
Overview of the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Forcing on the Mediterranean Climate (ChArMEx/ADRIMED) summer 2013 campaign Atmospheric Chemistry and Physics DOI 10.5194/acp-16-455-2016 19 January 2016 The aim of this article is to present an experimental campaign over the Mediterranean focused on aerosol-radiation measurements and modeling. Results indicate an important atmospheric loading associated with a moderate absorbing ability of mineral dust. Observations suggest a complex vertical structure and size distributions characterized by large aerosols within dust plumes. The radiative effect is highly variable, with negative forcing over the Mediterranean and positive over northern Africa. Read more
Aggregation in environmental systems – Part 1: Seasonal tracer cycles quantify young water fractions, but not mean transit times, in spatially heterogeneous catchments Hydrology and Earth System Sciences DOI 10.5194/hess-20-279-2016 19 January 2016 Catchment mean transit times have been widely inferred from seasonal cycles of environmental tracers in precipitation and streamflow. Here I show that these cycles yield strongly biased estimates of mean transit times in spatially heterogeneous catchments (and, by implication, in real-world catchments). However, I also show that these cycles can be used to reliably estimate the fraction of “young” water in streamflow, meaning water that fell as precipitation less than roughly 2–3 months ago. Read more
Aggregation in environmental systems – Part 2: Catchment mean transit times and young water fractions under hydrologic nonstationarity Hydrology and Earth System Sciences DOI 10.5194/hess-20-299-2016 19 January 2016 Here I show that seasonal tracer cycles yield strongly biased estimates of mean transit times in nonstationary catchments (and, by implication, in real-world catchments). However, they can be used to reliably estimate the fraction of “young” water in streamflow, meaning water that fell as precipitation less than roughly 2–3 months ago. This young water fraction varies systematically between high and low flows and may help in characterizing controls on stream chemistry. Read more
Diagnosing hydrological limitations of a land surface model: application of JULES to a deep-groundwater chalk basin Hydrology and Earth System Sciences DOI 10.5194/hess-20-143-2016 18 January 2016 This paper presents a strategy to diagnose hydrological limitations of a Land Surface Model. It includes the adaptation of the model for hydrological applications and highlights challenges faced while moving towards high resolution modelling. Read more
Topology of sustainable management of dynamical systems with desirable states: from defining planetary boundaries to safe operating spaces in the Earth system Earth System Dynamics DOI 10.5194/esd-7-21-2016 18 January 2016 The debate about a safe and just operating space for humanity and the possible pathways towards and within it requires an analysis of the inherent dynamics of the Earth system and of the options for influencing its evolution. We present and illustrate with examples a conceptual framework for performing such an analysis not in a quantitative, optimizing mode, but in a qualitative way that emphasizes the main decision dilemmas that one may face in the sustainable management of the Earth system. Read more
The Imbert Formation of northern Hispaniola: a tectono-sedimentary record of arc–continent collision and ophiolite emplacement in the northern Caribbean subduction–accretionary prism Solid Earth DOI 10.5194/se-7-11-2016 15 January 2016 New stratigraphical, structural, geochemical, and geochronological data from the northern Caribbean orogenic belt indicate that the Imbert Fm constitutes a coarsening-upward stratigraphic sequence that records the transition of the sedimentation from a pre-collisional forearc to a syn-collisional piggy-back basin in the lower-to-middle Eocene. This piggy-back basin was transported to the top of the Puerto Plata ophiolitic slab as it was emplaced onto the North America continental margin units. Read more
The assessment of a global marine ecosystem model on the basis of emergent properties and ecosystem function: a case study with ERSEM Geoscientific Model Development DOI 10.5194/gmd-9-59-2016 15 January 2016 To use models to inform policy or to forecast the impact of climate change, the model must first be shown to be a valid representation of the ecosystem. Here we show an novel method to validate a marine model using its ability to represent ecosystem function. These relationships are the community structure, the carbon to chlorophyll ratio and the stoichiometric balance of the ecosystem. These methods are powerful, valid over large spatial scales and independent of the circulation model. Read more
Committed retreat of Smith, Pope, and Kohler Glaciers over the next 30 years inferred by transient model calibration The Cryosphere DOI 10.5194/tc-9-2429-2015 21 December 2015 We calibrate a time-dependent ice model through optimal fit to transient observations of surface elevation and velocity, a novel procedure in glaciology and in particular for an ice stream with a dynamic grounding line. We show this procedure gives a level of confidence in model projections that cannot be achieved through more commonly used glaciological data assimilation methods. We show that Smith Glacier is in a state of retreat regardless of climatic forcing for the next several decades. Read more
Hidden biosphere in an oxygen-deficient Atlantic open-ocean eddy: future implications of ocean deoxygenation on primary production in the eastern tropical North Atlantic Biogeosciences DOI 10.5194/bg-12-7467-2015 21 December 2015 The waters of the tropical Atlantic Open Ocean usually contain comparably high concentrations of oxygen. Now, it became clear that there are watermasses related to eddies that are nearly anoxic. We surveyed one of those eddies and found a biosphere that largely differed from the usual biosphere present in this area with a specific community responsible for primary production and for degradation processes. Further, we found the very first indication for active nitrogen loss in the open Atlantic. Read more
Comment on “Ultra low frequency (ULF) electromagnetic anomalies associated with large earthquakes in Java Island, Indonesia by using wavelet transform and detrended fluctuation analysis” by Febriani et al. (2014) Natural Hazards and Earth System Sciences DOI 10.5194/nhess-15-2697-2015 18 December 2015 Reports of possible earthquake precursors have social responsibility. They motivate the idea that earthquakes may be predicted in the future. Thus, these papers should be convincing about the seismogenic origin of the reported precursors. We have reviewed Febriani et al. (2014). We have shown that the pre-earthquake magnetic changes they reported are not seismogenic but global-scale variations in the geomagnetic field in response to Sun–Earth interactions. Read more
Continental-scale temperature variability in PMIP3 simulations and PAGES 2k regional temperature reconstructions over the past millennium Climate of the Past DOI 10.5194/cp-11-1673-2015 16 December 2015 A comparison of model simulations and reconstructions at the continental scale over the past millennium indicates that models are in relatively good agreement with temperature reconstructions for Northern Hemisphere regions, particularly in the Arctic. This is likely due to the relatively large amplitude of the externally forced response across northern and high-latitudes regions. Conversely, models disagree strongly with the reconstructions in the Southern Hemisphere. Read more
Grain sorting in the morphological active layer of a braided river physical model Earth Surface Dynamics DOI 10.5194/esurf-3-577-2015 15 December 2015 A physical scale model of a gravel-bed braided river was used to measure vertical grain size sorting in the morphological active layer defined as the bed material between the maximum and minimum bed elevation. By normalizing active layer thickness and dividing into 10 sublayers we show that all grain sizes occur with almost equal frequency in all sublayers. Occurrence of patches and strings of coarser material relates to preservation of particular morphotextural features within the active layer. Read more
Data-based estimates of the ocean carbon sink variability – first results of the Surface Ocean pCO2 Mapping intercomparison (SOCOM) Biogeosciences DOI 10.5194/bg-12-7251-2015 11 December 2015 This study investigates variations in the CO2 uptake of the ocean from year to year. These variations have been calculated from measurements of the surface-ocean carbon content by various different interpolation methods. The equatorial Pacific is estimated to be the region with the strongest year-to-year variations, tied to the El Nino phase. The global ocean CO2 uptake gradually increased from about the year 2000. The comparison of the interpolation methods identifies these findings as robust. Read more
Updated ozone absorption cross section will reduce air quality compliance Atmospheric Chemistry and Physics DOI 10.5194/acp-15-13627-2015 10 December 2015 As an air pollutant, O3 is monitored photometrically to assess compliance with air quality legislation. A recent study found a 1.8% reduction in its absorption cross section, which would lead to an equivalent increase in observed O3 concentrations. We estimate this would increase the number of sites out of compliance with air quality regulations in the EU and US by 20%. We draw attention to how small changes in gas metrology impacts attainment and compliance with legal air quality standards. Read more
Magnetospheric conditions near the equatorial footpoints of proton isotropy boundaries Annales Geophysicae DOI 10.5194/angeo-33-1485-2015 9 December 2015 Adaptive magnetospheric models based on THEMIS magnetic observations made at 6-9Re in the nightside magnetosphere are used to map the magnetically conjugate 30 and 80keV proton isotropy boundaries (IBs) to investigate the value of Kib=Rc/rc (magnetic curvature radius to particle gyroradius) in the neutral sheet at the IB generation place. For the most accurate mapping, the group Kib spread spans from 4 to 32; its median value is ~13, slightly larger than Kib8 expected for current sheet scatter. Read more
Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems Biogeosciences DOI 10.5194/bg-12-7129-2015 8 December 2015 In this review, we give an overview of the current state of knowledge regarding how permafrost thaw affects aquatic systems. We describe the general impacts of thaw on aquatic ecosystems, pathways of organic matter and contaminant release and degradation, resulting emissions and burial, and effects on ecosystem structure and functioning. We conclude with an overview of potential climate effects and recommendations for future research. Read more
Observations of the spectral dependence of linear particle depolarization ratio of aerosols using NASA Langley airborne High Spectral Resolution Lidar Atmospheric Chemistry and Physics DOI 10.5194/acp-15-13453-2015 7 December 2015 The manuscript describes measurements of particle depolarization ratio from the NASA airborne HSRL-2 at three wavelengths, for two dust cases and a smoke case. Differences in the spectral dependence of particle depolarization ratio are due to the sizes of the non-spherical particles, large for dust and small for smoke. The large depolarization at 355nm for smoke has not been previously reported and may impact aerosol typing when only a single wavelength is available. Read more
Biodegradability of dissolved organic carbon in permafrost soils and aquatic systems: a meta-analysis Biogeosciences DOI 10.5194/bg-12-6915-2015 3 December 2015 We found that dissolved organic carbon (DOC) in arctic soils and aquatic systems is increasingly degradable with increasing permafrost extent. Also, DOC seems less degradable when moving down the fluvial network in continuous permafrost regions, i.e. from streams to large rivers, suggesting that highly bioavailable DOC is lost in headwater streams. We also recommend a standardized DOC incubation protocol to facilitate future comparison on processing and transport of DOC in a changing Arctic. Read more
pH up-regulation as a potential mechanism for the cold-water coral Lophelia pertusa to sustain growth in aragonite undersaturated conditions Biogeosciences DOI 10.5194/bg-12-6869-2015 1 December 2015 We investigated the ability of cold-water corals to deal with changes in ocean pH. We uniquely combined morphological assessment with boron isotope analysis to determine if changes in growth are related to changes in control of calcification pH. We found that the cold-water coral Lophelia pertusa can maintain the skeletal morphology, growth patterns as well as internal calcification pH. This has important implications for their future occurrence and explains their cosmopolitan distribution. Read more
A dynamical systems approach to the surface search for debris associated with the disappearance of flight MH370 Nonlinear Processes in Geophysics DOI 10.5194/npg-22-701-2015 25 November 2015 The disappearance of Malaysia Airlines flight MH370 on 8 March 2014 is one of the great mysteries of our time. The most relevant aspect is that not a piece of debris was found during the intensive surface search carried out for roughly 2 months following the crash. By combining different ocean data with dynamical systems tools, we propose a revised search strategy by showing why debris could not have been expected in some targeted search areas and determining regions where debris could be. Read more
Laboratory evidence of organic peroxide and peroxyhemiacetal formation in the aqueous phase and implications for aqueous OH Atmospheric Chemistry and Physics DOI 10.5194/acp-15-12867-2015 19 November 2015 This paper demonstrates organic peroxide and peroxyhemiacetal formation during aqueous photooxidation of methylglyoxal using ultra-high-resolution Fourier transform ion cyclotron resonance electrospray ionization mass spectrometry (FTICR-MS). Then, we provide simulation results of organic peroxide/peroxyhemiacetal formation in clouds and wet aerosols and discuss organic peroxides as a source of condensed-phase OH radicals and as a contributor to aqueous secondary organic aerosol (SOA). Read more
Ice water content vertical profiles of high-level clouds: classification and impact on radiative fluxes Atmospheric Chemistry and Physics DOI 10.5194/acp-15-12327-2015 9 November 2015 We discuss the shape of ice water content (IWC) vertical profiles in high ice clouds and its effect on radiative properties of these clouds, both in short- and in long-wave bands (SW and LW). We suggest a set of primitive shapes (rectangular, isosceles trapezoid, lower and upper triangle) and propose a statistical parameterization using ice water path (IWP) as a single parameter. We estimate and explain simulated differences in LW/SW atmospheric radiances for suggested IWC shapes. Read more
Reducing uncertainties in projections of Antarctic ice mass loss The Cryosphere DOI 10.5194/tc-9-2043-2015 9 November 2015 Projections of Antarctic dynamics and contribution to sea-level rise are evaluated in the light of intercomparison exercises dedicated to evaluate models’ ability of representing coastal changes. Uncertainties in projections can be substantially decreased if a selection of models is made and models that are unqualified for the representation of coastal dynamics are excluded. Read more
Modelling Mediterranean agro-ecosystems by including agricultural trees in the LPJmL model Geoscientific Model Development DOI 10.5194/gmd-8-3545-2015 5 November 2015 This study presents the inclusion of 10 Mediterranean agricultural plants in an agro-ecosystem model (LPJmL): nut trees, date palms, citrus trees, orchards, olive trees, grapes, cotton, potatoes, vegetables and fodder grasses. The model was successfully tested in three model outputs: agricultural yields, irrigation requirements and soil carbon density. With this development presented, LPJmL is now able to simulate in good detail and mechanistically the functioning of Mediterranean agriculture. Read more
Expanding the validity of the ensemble Kalman filter without the intrinsic need for inflation Nonlinear Processes in Geophysics DOI 10.5194/npg-22-645-2015 3 November 2015 The popular data assimilation technique known as the ensemble Kalman filter (EnKF) suffers from sampling errors due to the limited size of the ensemble. This deficiency is usually cured by inflating the sampled error covariances and by using localization. This paper further develops and discusses the finite-size EnKF, or EnKF-N, a variant of the EnKF that does not require inflation. It expands the use of the EnKF-N to a wider range of dynamical regimes. Read more
Local- and regional-scale measurements of CH4, δ13CH4, and C2H6 in the Uintah Basin using a mobile stable isotope analyzer Atmospheric Measurement Techniques DOI 10.5194/amt-8-4539-2015 30 October 2015 We describe an innovative instrument based on cavity ring-down spectroscopy that analyzes the stable isotopes of methane in the ambient atmosphere. This instrument was used to study atmospheric emissions from oil and gas extraction activities in the Uintah Basin in Utah. These measurements suggest that 85 ± 7% of the total emissions in the basin are from natural gas production. The easy field deployment of this instrument can enable similar regional attribution studies across the world. Read more
Regional analysis of groundwater droughts using hydrograph classification Hydrology and Earth System Sciences DOI 10.5194/hess-19-4327-2015 28 October 2015 To improve the design of drought monitoring networks and water resource management during episodes of drought, there is a need for a better understanding of spatial variations in the response of aquifers to major meteorological droughts. This paper is the first to describe a suite of methods to quantify such variations. Using an analysis of groundwater level data for a case study from the UK, the influence of catchment characteristics on the varied response of groundwater to droughts is explored. Read more
The importance of Asia as a source of black carbon to the European Arctic during springtime 2013 Atmospheric Chemistry and Physics DOI 10.5194/acp-15-11537-2015 20 October 2015 We show that during the springtime of 2013, the anthropogenic pollution particularly from sources in Asia, contributed significantly to black carbon across the European Arctic free troposphere. In contrast to previous studies, the contribution from open wildfires was minimal. Given that Asian pollution is likely to continue to rise over the coming years, it is likely that the radiative forcing in the Arctic will also continue to increase. Read more
Earthquakes and depleted gas reservoirs: which comes first? Natural Hazards and Earth System Sciences DOI 10.5194/nhess-15-2201-2015 7 October 2015 While the debate is on the possibility that the 2012 Emilia quakes could have been triggered by human activity, we studied the inverse relationship between hydrocarbon and seismicity. Overlapping a data set of gas and oil wells with a database of seismic sources, we found that only 1/19 wells falling on the largest faults is currently productive, while the highest ratio of productive wells is found outside the seismogenic sources. In general, productive gas wells are anti-correlated with faults. Read more
ECCO version 4: an integrated framework for non-linear inverse modeling and global ocean state estimation Geoscientific Model Development DOI 10.5194/gmd-8-3071-2015 6 October 2015 The ECCO v4 non-linear inverse modeling framework and its reference solution are made publicly available. The inverse estimate of ocean physics and atmospheric forcing yields a dynamically consistent and global state estimate without unidentified sources of heat and salt that closely fits in situ and satellite data. Any user can reproduce it accurately. Parametric and external model uncertainties are of comparable magnitudes and generally exceed structural model uncertainties. Read more
Recent highlights from Cluster, the first 3-D magnetospheric mission Annales Geophysicae DOI 10.5194/angeo-33-1221-2015 2 October 2015 This paper presents recent highlights from the Cluster mission on solar wind turbulence, magnetopause asymmetries and magnetosheath density enhancements, dipolarisation currents, reconnection variability, FTE in greatest detail, plasmaspheric wind and re-filling of the plasmasphere, radiation belts, updates of magnetospheric electric and magnetic field models, and magnetosheath and magnetopause properties under low Mach number. Public access to all high-resolution data (CSA) is also presented. Read more
Evaluating the climate and air quality impacts of short-lived pollutants Atmospheric Chemistry and Physics DOI 10.5194/acp-15-10529-2015 24 September 2015 This paper presents a summary of the findings of the ECLIPSE EU project. The project has investigated the climate and air quality impacts of short-lived climate pollutants (especially methane, ozone, aerosols) and has designed a global mitigation strategy that maximizes co-benefits between air quality and climate policy. Transient climate model simulations allowed quantifying the impacts on temperature (e.g., reduction in global warming by 0.22K for the decade 2041-2050) and precipitation. Read more
POM.gpu-v1.0: a GPU-based Princeton Ocean Model Geoscientific Model Development DOI 10.5194/gmd-8-2815-2015 9 September 2015 Graphics processing units (GPUs) are an attractive solution in many scientific applications due to their high performance. However, most existing GPU conversions of climate models use GPUs for only a few computationally intensive regions. In the present study, we redesign the mpiPOM (a parallel version of the Princeton Ocean Model) with GPUs. We show that the performance of the new model on a workstation containing four GPUs is comparable to that on a powerful cluster with 408 standard CPU cores, and it reduces the energy consumption by a factor of 6.8. Read more
Impact of climate and land cover changes on tropospheric ozone air quality and public health in East Asia between 1980 and 2010 Atmospheric Chemistry and Physics DOI 10.5194/acp-15-10093-2015 9 September 2015 Historical land cover and land use change alone between 1980 and 2010 could lead to reduced summertime surface ozone by up to 4ppbv in East Asia. Climate change alone could lead to an increase in summertime ozone by 2-10ppbv in most of East Asia. Land cover change could offset part of the climate effect and lead to a previously unknown public health benefit. The sensitivity of surface ozone to land cover change is more dependent on dry deposition than isoprene emission in most of East Asia. Read more
The feasibility of water vapor sounding of the cloudy boundary layer using a differential absorption radar technique Atmospheric Measurement Techniques DOI 10.5194/amt-8-3631-2015 8 September 2015 This paper describes the feasibility of using a differential absorption radar technique for the remote sensing of water vapor within clouds near the Earth surface from a spaceborne platform. The proposed methodology is shown to be theoretically achievable and complimentary to existing water vapor remote sensing methods. Read more
Past changes in the vertical distribution of ozone – Part 3: Analysis and interpretation of trends Atmospheric Chemistry and Physics DOI 10.5194/acp-15-9965-2015 7 September 2015 Trends in the vertical distribution of ozone are reported for new and recently revised data sets. The amount of ozone-depleting compounds in the stratosphere peaked in the second half of the 1990s. We examine the trends before and after that peak to see if any change in trend is discernible. The previously reported decreases are confirmed. Furthermore, the downward trend in upper stratospheric ozone has not continued. The possible significance of any increase is discussed in detail. Read more
Diesel-related hydrocarbons can dominate gas phase reactive carbon in megacities Atmospheric Chemistry and Physics DOI 10.5194/acp-15-9983-2015 7 September 2015 Technological shifts between fuel sources have had unexpected impacts on atmospheric composition and these significant changes can go undetected if source-specific monitoring infrastructure is not in place. We present chemically comprehensive, continuous measurements of organic compounds in a developed megacity (London), that show diesel-related hydrocarbons can dominate reactive carbon and ozone formation potential, highlighting a serious underestimation of this source in emission inventories. Read more
Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core The Cryosphere DOI 10.5194/tc-9-1633-2015 20 August 2015 The oldest paleoclimatic information is buried within the lowermost layers of deep ice cores. It is therefore essential to judge how deep these records remain unaltered. We study the bottom 60 meters of the EPICA Dome C ice core from central Antarctica to show that the paleoclimatic signal is only affected at the small scale (decimeters) in terms of some of the global ice properties. However our data suggest that the time scale has been considerably distorted by mechanical stretching. Read more
Observation of a new type of low-frequency waves at comet 67P/Churyumov-Gerasimenko Annales Geophysicae DOI 10.5194/angeo-33-1031-2015 19 August 2015 We present a first report on magnetic field measurements made in the coma of comet 67P/C-G in its low activity state. The plasma environment is dominated by quasi-coherent, large-amplitude, compressional magnetic field oscillations around 40 mHz, differing from the observations at strongly active comets where waves at the cometary ion gyro-frequencies are the main feature. We propose a cross-field current instability associated with the newborn cometary ions as a possible source mechanism. Read more
Century-scale simulations of the response of the West Antarctic Ice Sheet to a warming climate The Cryosphere DOI 10.5194/tc-9-1579-2015 18 August 2015 We used a high resolution ice sheet model capable of resolving grouding line dynamics (BISICLES) to compute responses of the major West Antarctic ice streams to projections of ocean and atmospheric warming. This is computationally demanding, and although other groups have considered parts of West Antarctica, we think this is the first calculation for the whole region at the sub-kilometer resolution that we show is required. Read more
Tropospheric ozone and its precursors from the urban to the global scale from air quality to short-lived climate forcer Atmospheric Chemistry and Physics DOI 10.5194/acp-15-8889-2015 13 August 2015 Ozone holds a certain fascination in atmospheric science. It is ubiquitous in the atmosphere, central to tropospheric oxidation chemistry, and yet harmful to human and ecosystem health as well as being an important greenhouse gas. It is not emitted into the atmosphere but is a byproduct of the very oxidation chemistry it largely initiates. This review examines current understanding of the processes regulating tropospheric ozone at global to local scales from both measurements and models. Read more