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
