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