ALBERT

Description: 〈b〉High variability of particulate organic carbon export along the North Atlantic GEOTRACES section GA01 as deduced from 〈sup〉234〈/sup〉Th fluxes〈/b〉〈br〉 Nolwenn Lemaitre, Frédéric Planchon, Hélène Planquette, Frank Dehairs, Debany Fonseca-Batista, Arnout Roukaerts, Florian Deman, Yi Tang, Clarisse Mariez, and Géraldine Sarthou〈br〉 Biogeosciences, 15, 6417-6437, https://doi.org/10.5194/bg-15-6417-2018, 2018〈br〉 We investigated the surface particulate organic carbon export fluxes in the North Atlantic with the objective of better understanding the biological carbon pump. Our results highlighted that exports depended on the intensity and stage of the bloom, the phytoplankton size and community structures. After comparing with primary production, we concluded that, during our study, the North Atlantic behaves like most of the highly productive areas in the world's ocean, with a low export efficiency.

Description: 〈b〉Retrieval of liquid water cloud properties from POLDER-3 measurements using a neural network ensemble approach〈/b〉〈br〉 Antonio Di Noia, Otto P. Hasekamp, Bastiaan van Diedenhoven, and Zhibo Zhang〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-345,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉This paper describes a neural network algorithm for the estimation of liquid water cloud optical properties from the Polarization and Directionality of Earth's Reflectances-3 (POLDER-3) instrument, on board the Polarization & Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar (PARASOL) satellite. The algorithm has been trained on synthetic multi-angle, multi-wavelength measurements of reflectance and polarization, and has been applied to the processing of one year of POLDER-3 data. Comparisons of the retrieved cloud properties with Moderate resolution Imaging Spectroradiometer (MODIS) products show negative biases around −2 in retrieved cloud optical thicknesses (COTs) and between −1 and −2 μm in retrieved cloud effective radii. Comparisons with existing POLDER-3 datasets suggest that the proposed scheme may have enhanced capabilities for cloud effective radius retrieval at least over land. An additional feature of the presented algorithm is that it provides COT and effective radius retrievals at the native POLDER-3 Level 1B pixel level.〈/p〉

Description: 〈b〉Evaluation of atmospheric nitrogen inputs into marine ecosystems of the North Sea and Baltic Sea – part B: contribution by shipping and agricultural emissions〈/b〉〈br〉 Daniel Neumann, Hagen Radtke, Matthias Karl, and Thomas Neumann〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-365,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 The contribution of atmospheric nitrogen deposition to the marine dissolved inorganic nitrogen (DIN) pool of the North and Baltic Sea was assessed for the year 2012. Atmospheric deposition accounted for approximately 10 % to 15 % of the DIN but its residence time differed between both water bodies. The nitrogen contributions of atmospheric shipping and agricultural imissions also were assessed. Particularly the latter source had a large impact in coastal regions.

Description: 〈b〉Recovery of the three-dimensional wind and sonic temperature data from a physically deformed sonic anemometer〈/b〉〈br〉 Xinhua Zhou, Qinghua Yang, Xiaojie Zhen, Yubin Li, Guanghua Hao, Hui Shen, Tian Gao, Yirong Sun, and Ning Zheng〈br〉 Atmos. Meas. Tech., 11, 5981-6002, https://doi.org/10.5194/amt-11-5981-2018, 2018〈br〉 The three-dimensional wind and sonic temperature data from a physically deformed sonic anemometer was successfully recovered by developing equations, algorithms, and related software. Using two sets of geometry data from production calibration and return re-calibration, this algorithm can recover wind with/without transducer shadow correction and sonic temperature with crosswind correction, and then obtain fluxes at quality as expected. This study is applicable as a reference for related topics.

Description: 〈b〉Doppler W-band polarization diversity space-borne radar simulator for wind studies〈/b〉〈br〉 Alessandro Battaglia, Ranvir Dhillon, and Anthony Illingworth〈br〉 Atmos. Meas. Tech., 11, 5965-5979, https://doi.org/10.5194/amt-11-5965-2018, 2018〈br〉 A new technique is proposed to simulated winds in clouds as they could be observed by a space-borne Doppler 3 mm wavelength radar. Results show that, in the presence of cloud inhomogeneity and of vertical wind shear, measured winds can be corrected and produce unbiased estimates of line-of-sight winds that can then be assimilated in numerical models to improve weather forecasts.

Description: 〈b〉Nitric oxide (NO) in the Bohai and Yellow Seas〈/b〉〈br〉 Ye Tian, Chao Xue, Chun-Ying Liu, Gui-Peng Yang, Pei-Feng Li, Wei-Hua Feng, and Hermann W. Bange〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-446,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 1 comment)〈br〉 Nitric oxide (NO) seems to be widespread with different functions in marine ecosystem but know little about it. Concentrations of NO were in the range of from below the detection limit to 616 pmol L〈sup〉−1〈/sup〉 in the surface and to 482 pmol L〈sup〉−1〈/sup〉 in the bottom of the Bohai and Yellow Seas. The study region was a source of the atmospheric NO. NO sea-to-air fluxes were much lower than NO photoproduction rates, implying that the NO produced in the mixed layer was rapidly consumed before enter the atmosphere.

Description: 〈b〉Towards a more complete quantification of the global carbon cycle〈/b〉〈br〉 Miko U. F. Kirschbaum, Guang Zeng, Fabiano Ximenes, Donna L. Giltrap, and John R. Zeldis〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-436,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 Globally, we add carbon to the atmosphere from fossil fuels and deforestation, balanced by ocean uptake and atmospheric increase. The difference is a residual sink equated to plant uptake. But this omits cement carbonation and pools of plastic, bitumen, wood, landfills and lakes, and transport by wind erosion, volatile C compounds and river transport. This reduces the residual sink from 3.6 to 2.1 GtC yr〈sup〉−1〈/sup〉 with important implications for natural feedbacks to amplify or negate human C emissions.

Description: 〈b〉Evaluation of the seasonal formation of subsurface negative preformed nitrate anomalies in the subtropical North Pacific and North Atlantic〈/b〉〈br〉 Robert T. Letscher and Tracy A. Villareal〈br〉 Biogeosciences, 15, 6461-6480, https://doi.org/10.5194/bg-15-6461-2018, 2018〈br〉 The formation rates of oxygen to nitrogen anomalies in the subtropical North Pacific and North Atlantic were estimated from time series data. We find that vertically migrating phytoplankton, which traverse ~ 100–150 m in the upper ocean over days to acquire nutrients from waters at depth and return to the surface for photosynthesis, likely explain the observed anomalies and help sustain surface ocean productivity and the biological pump throughout the annual cycle in the subtropical ocean.

Description: 〈b〉Dynamic mercury methylation and demethylation in oligotrophic marine water〈/b〉〈br〉 Kathleen M. Munson, Carl H. Lamborg, Rene M. Boiteau, and Mak A. Saito〈br〉 Biogeosciences, 15, 6451-6460, https://doi.org/10.5194/bg-15-6451-2018, 2018〈br〉 Methylmercury accumulates in marine organisms and is produced by bacterial processes in sediment systems. To date, the contribution of these processes to the marine water column is poorly understood. We measured noncellular production and breakdown of methylmercury in equatorial Pacific waters. We observed enhanced production in filtered waters that suggests noncellular processes result in rapid mercury transformations and, in turn, control methylmercury concentrations in the open ocean.

Description: 〈b〉Constraints on Enhanced Weathering and related carbon sequestration – a cropland mesocosm approach〈/b〉〈br〉 Thorben Amann, Jens Hartmann, Eric Struyf, Wagner de Oliveira Garcia, Elke K. Fischer, Ivan Janssens, Patrick Meire, and Jonas Schoelynck〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-398,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 1 comment)〈br〉 Weathering is a major control on atmospheric CO〈sub〉2〈/sub〉 at geologic time scales. Enhancement of this process can be used to actively remove CO〈sub〉2〈/sub〉 from the atmosphere. Field results are still scarce and with this experiment we try to add some near natural insights into dissolution processes. Results show CO〈sub〉2〈/sub〉 sequestration potentials but also highlight the strong variability of outcomes that can be expected in natural environments. Such experiments are of utmost importance to identify key processes.

Description: 〈b〉Isotopic fractionation corrections for the radiocarbon composition of CO〈sub〉2〈/sub〉 in the soil gas environment must include diffusion and mixing〈/b〉〈br〉 Jocelyn E. Egan, David R. Bowling, and David A. Risk〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-451,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 1 comment)〈br〉 Traditionally a mass-dependent correction is made when measuring the radiocarbon composition in organic samples. This correction has not been evaluated for the soil gas environment where gas transport processes are important. Here, we show using theory, analytical models and field data that this traditional correction is not appropriate for estimating the radiocarbon composition of soil biological production. We also propose a new solution that accounts for soil gas transport processes.

Description: 〈b〉Ideas and perspectives: Tree–atmosphere interaction responds to water-related stem variations〈/b〉〈br〉 Tim van Emmerik, Susan Steele-Dunne, Pierre Gentine, Rafael S. Oliveira, Paulo Bittencourt, Fernanda Barros, and Nick van de Giesen〈br〉 Biogeosciences, 15, 6439-6449, https://doi.org/10.5194/bg-15-6439-2018, 2018〈br〉 Trees are very important for the water and carbon cycles. Climate and weather models often assume constant vegetation parameters because good measurements are missing. We used affordable accelerometers to measure tree sway of 19 trees in the Amazon rainforest. We show that trees respond very differently to the same weather conditions, which means that vegetation parameters are dynamic. With our measurements trees can be accounted for more realistically, improving climate and weather models.

Description: 〈b〉Potential of INSAT-3D sounder-derived total precipitable water product for weather forecast〈/b〉〈br〉 Shailesh Parihar, Ashim Kumar Mitra, Mrutyunjay Mohapatra, and Rajjev Bhatla〈br〉 Atmos. Meas. Tech., 11, 6003-6012, https://doi.org/10.5194/amt-11-6003-2018, 2018〈br〉 This paper is based on operational work carried out at IMD, New Delhi using the INSAT-3D satellite-derived sounder product TPW for weather events such as rainfall and thunderstorms. The INSAT-3D TPW has been used by forecasters as well as many other users over the last 2 years. This work mainly brings out an in-depth validation with in situ ground measurement data as well as a GNSS system for its suitability in weather prediction. This paper can be utilized operationally for weather purposes.

Description: 〈b〉High-precision measurements of nitrous oxide and methane in air with cavity ring-down spectroscopy at 7.6 μm〈/b〉〈br〉 Jing Tang, Bincheng Li, and Jing Wang〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-385,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 A high-sensitivity CH〈sub〉4〈/sub〉 and N〈sub〉2〈/sub〉O sensor based on mid-IR (7.6 µm) cavity ring-down spectroscopy was developed. The effect of temperature fluctuation on measurement sensitivity was analyzed and corrected, and detection limits of 3.62 pptv for CH〈sub〉4〈/sub〉 and 4.67 pptv for N〈sub〉2〈/sub〉O were experimentally achieved. Separate and continuous measurements of CH〈sub〉4〈/sub〉 and N〈sub〉2〈/sub〉O concentrations of in-/out-door air at different locations showed the spatial and temporal concentration variations of CH〈sub〉4〈/sub〉 and N〈sub〉2〈/sub〉O in air.

Description: 〈b〉Calibration of isotopologue-specific optical trace gas analysers: a practical guide〈/b〉〈br〉 David W. T. Griffith〈br〉 Atmos. Meas. Tech., 11, 6189-6201, https://doi.org/10.5194/amt-11-6189-2018, 2018〈br〉 In recent years optical spectroscopic techniques have become commonly used in the determination of mole fractions of trace gases in air. These techniques in many cases determine the mole fractions of only individual isotopic variants (〈q〉isotopologues〈/q〉) of the trace gas, while for many applications the total mole fraction of all isotopologues is required. This paper sets out the measurements and calculations required to convert between individual isotopologue and total trace gas amounts.

Description: 〈b〉Global, Satellite-Driven Estimates of Heterotrophic Respiration〈/b〉〈br〉 Alexandra G. Konings, A. Anthony Bloom, Junjie Liu, Nicholas C. Parazoo, David S. Schimel, and Kevin W. Bowman〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-466,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 We estimate heterotrophic respiration (Rh) – the respiration from microbes in the soil – using satellite estimates of the net carbon flux and other quantities. Rh is an important carbon flux but is rarely studied by itself. Our method is the first to estimate how Rh varies in both space and time. The resulting new estimate of Rh is compared to the best currently available alternative – which is based on interpolating field measurements globally. The two estimates disagree and are both uncertain.

Description: 〈b〉Variation of key elements in soils and plant tissues in subalpine forests of the northern Rocky Mountains, USA〈/b〉〈br〉 David P. Pompeani, Kendra K. McLauchlan, Barrie V. Chileen, Kyra D. Wolf, and Philip E. Higuera〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-443,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉The essential elements for the structure and function of forest ecosystems are found in relatively predictable proportions in living tissues and soils; however, both the degree of spatial variability in elemental concentrations and their relationship with wildfire history are unclear. Quantifying the association between nutrient concentrations in living plant tissue and surface soils within fire-affected forests can help determine how these elements contribute to biogeochemical resilience. Here, we present elemental concentration data (C, N, P, K, Ca, Mg, S, Fe, Mn, Zn) from 72 foliar and 44 soil samples from a network of 15 sites located in the fire-prone subalpine forests of the northern Rocky Mountains, USA Plant functional type is strongly correlated with carbon (C) and nitrogen (N) – C concentrations are highest in coniferous needles, and N concentrations are highest in broadleaved plant species. The average N / P ratio of foliage among samples is 9.8 ± 0.6 (μ ± 95 % confidence). This suggests that N is the limiting nutrient for these plants, however several factors can complicate the use of N / P ratios to evaluate nutrient status. Average C concentrations in organic soil horizons that were burned in regionally extensive fires in 1910 or 1918 CE are lower than those from sites that burned prior to 1901 CE (p 〈/p〉

Description: 〈b〉Reviews and syntheses: 〈sup〉210〈/sup〉Pb-derived sediment and carbon accumulation rates in vegetated coastal ecosystems – setting the record straight〈/b〉〈br〉 Ariane Arias-Ortiz, Pere Masqué, Jordi Garcia-Orellana, Oscar Serrano, Inés Mazarrasa, Núria Marbà, Catherine E. Lovelock, Paul S. Lavery, and Carlos M. Duarte〈br〉 Biogeosciences, 15, 6791-6818, https://doi.org/10.5194/bg-15-6791-2018, 2018〈br〉 Efforts to include tidal marsh, mangrove and seagrass ecosystems in existing carbon mitigation strategies are limited by a lack of estimates of carbon accumulation rates (CARs). We discuss the use of 〈sup〉210〈/sup〉Pb dating to determine CARs in these habitats, which are often composed of heterogeneous sediments and affected by sedimentary processes. Results show that obtaining reliable geochronologies in these systems is ambitious, but estimates of mean 100-year CARs are mostly secure within 20 % error.

Description: 〈b〉Improving the Mean and Uncertainty of Ultraviolet Multi-Filter Rotating Shadowband Radiometer In-Situ Calibration Factors: Utilizing Gaussian Process Regression with a New Method to Estimate Dynamic Input Uncertainty〈/b〉〈br〉 Maosi Chen, Zhibin Sun, John M. Davis, Yan-An Liu, Chelsea A. Corr, and Wei Gao〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-295,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉To recover the actual responsivity for Ultraviolet Multi-Filter Rotating Shadowband Radiometer (UV-MFRSR), the complex (e.g. unstable, noisy, and with gaps) time series of its in-situ calibration factors (Vo) need to be smoothed. Many smoothing techniques require accurate input uncertainty of the time series. A new method is proposed to estimate the dynamic input uncertainty by examining overall variation and subgroup means within a moving time window. Using this calculated dynamic input uncertainty within Gaussian Process regression (GP) provides the mean and uncertainty functions of the time series. This proposed GP solution was first applied on a synthetic signal and showed significant smaller RMSEs than a Gaussian Process regression performed with constant values of input uncertainty and the mean function. GP was then applied to three UV-MFRSR Vo time series at three ground sites; The method appropriately accounted for variation in slopes, noises, and gaps at all sites. The validation results demonstrated that the agreement between aerosol optical depths (AODs) calculated using Vo determined by the GP mean function and AERONET AODs were consistently better than those calculated using Vo from standard techniques (e.g. moving average). The improved accuracy of in-situ UVMRP Vo values suggests the GP solution is a robust technique for accurate analysis of complex time series and may be applicable to other fields.〈/p〉

Description: 〈b〉Quantitative mapping and predictive modeling of Mn nodules' distribution from hydroacoustic and optical AUV data linked by random forests machine learning〈/b〉〈br〉 Iason-Zois Gazis, Timm Schoening, Evangelos Alevizos, and Jens Greinert〈br〉 Biogeosciences, 15, 7347-7377, https://doi.org/10.5194/bg-15-7347-2018, 2018〈br〉 The use of high-resolution hydroacoustic and optic data acquired by an autonomous underwater vehicle can give us detailed sea bottom topography and valuable information regarding manganese nodules' spatial distribution. Moreover, the combined use of these data sets with a random forest machine learning model can extend this spatial prediction beyond the areas with available photos, providing researchers with a new mapping tool for further investigation and links with other data.

Description: 〈b〉Insights from year-long measurements of air-water CH〈sub〉4〈/sub〉 and CO〈sub〉2〈/sub〉 exchange in a coastal environment〈/b〉〈br〉 Mingxi Yang, Thomas G. Bell, Ian J. Brown, James R. Fishwick, Vassilis Kitidis, Philip D. Nightingale, Andrew P. Rees, and Timothy J. Smyth〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-503,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 1 comment)〈br〉 We quantify the emissions and uptake of greenhouse gases carbon dioxide and methane from the coastal seas of the UK over 1 year using the state-of-the-art eddy covariance technique. Our measurements show how these air-sea fluxes vary twice a day (tidal), diurnally (circadian), and seasonally. We also estimate the air-sea gas transfer velocity, which is essential for modeling and predicting coastal air-sea exchange.

Description: 〈b〉Underestimation of denitrification rates from field application of the 〈sup〉15〈/sup〉N gas flux method and its correction by gas diffusion modelling〈/b〉〈br〉 Reinhard Well, Martin Maier, Dominika Lewicka-Szczebak, Jan-Reent Köster, and Nicolas Ruoss〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-495,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 1 comment)〈br〉 〈p〉Common methods for measuring soil denitrification in situ include monitoring the accumulation of 〈sup〉15〈/sup〉N-labelled N〈sub〉2〈/sub〉 and N〈sub〉2〈/sub〉O evolved from 〈sup〉15〈/sup〉N-labelled soil nitrate pool in closed chambers that are placed on the soil surface. Gas diffusion is considered to be the main transport process in the soil. Because accumulation of gases within the chamber decreases concentration gradients between soil and chamber over time, the surface efflux of gases decreases as well and gas production rates are underestimated if calculated from chamber concentrations without consideration of this mechanism. Moreover, concentration gradients to the non-labelled subsoil exist, inevitably causing downward diffusion of 〈sup〉15〈/sup〉N labelled denitrification products. A numerical 3-D model for simulating gas diffusion in soil was used in order to determine the significance of this source of error. Results show that subsoil diffusion of 〈sup〉15〈/sup〉N-labelled N〈sub〉2〈/sub〉 and N〈sub〉2〈/sub〉O – and thus potential underestimation of denitrification derived from chamber fluxes – increases with chamber deployment time as well as with increasing soil gas diffusivity. Simulations based on the range of typical soil gas diffusivities of unsaturated soils showed that the fraction of N〈sub〉2〈/sub〉 and N〈sub〉2〈/sub〉O evolved from 〈sup〉15〈/sup〉N-labelled NO〈sub〉3〈/sub〉 that is not emitted at the soil surface during one hour chamber closing is always significant with values up to 〉 50 % of total production due to accumulation in the pore space of the 〈sup〉15〈/sup〉N-labelled soil and diffusive flux to the unlabelled subsoil. Empirical coefficients to calculate denitrification from surface fluxes were derived by modelling multiple scenarios with varying soil water content.〈/p〉 〈p〉Field experiments with arable silt loam soil for measuring denitrification with the 〈sup〉15〈/sup〉N gas flux method were conducted to obtain direct evidence for the incomplete surface emission of gaseous denitrification products. We compared surface fluxes of 〈sup〉15〈/sup〉N〈sub〉2〈/sub〉 and 〈sup〉15〈/sup〉N〈sub〉2〈/sub〉O from 〈sup〉15〈/sup〉N–labelled micro-plots confined by cylinders using the closed chamber method with cylinders open or closed at the bottom, finding 37 % higher surface fluxes with bottom closed. Modeling fluxes of this experiment confirmed this effect, however with a higher increase in surface flux of 89 %.〈/p〉 〈p〉From our model and experimental results we conclude that field surface fluxes of 〈sup〉15〈/sup〉N-labelled N〈sub〉2〈/sub〉 and N〈sub〉2〈/sub〉O severely underestimate denitrification rates if calculated from chamber accumulation only. The extent of this underestimation increases with closure time. Underestimation also occurs during laboratory incubations in closed systems due to pore space accumulation of 〈sup〉15〈/sup〉N-labelled N〈sub〉2〈/sub〉 and N〈sub〉2〈/sub〉O. Due to this bias in past denitrification measurements, denitrification in soils might be more relevant than assumed to date. Corrected denitrification rates can be obtained by estimating subsurface flux and storage with our model. The observed deviation between experimental and modeled subsurface flux revealed the need for refined model evaluation which must include assessment of the spatial variability in diffusivity and production and the spatial dimension of the chamber.〈/p〉

Description: 〈b〉Ideas and perspectives: Synergies from co-deployment of negative emission technologies〈/b〉〈br〉 Thorben Amann and Jens Hartmann〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-500,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 1 comment)〈br〉 With the recent publication of the IPCC special report on the 1.5° target and increased attention on carbon dioxide removal (CDR) technologies, we think it is time to advance from the current way to look at specific strategies forward to a more holistic CDR perspective, since multiple 〈q〉side effects〈/q〉 may lead to additional CO〈sub〉2〈/sub〉 uptake into different carbon pools. This paper explores potential co-benefits between terrestrial CDR strategies to facilitate a maximum CO〈sub〉2〈/sub〉 sequestration effect.

Description: 〈b〉Coupled Ca and inorganic carbon uptake suggested by magnesium and sulfur incorporation in foraminiferal calcite〈/b〉〈br〉 Inge van Dijk, Christine Barras, Lennart Jan de Nooijer, Aurélia Mouret, Esmee Geerken, Shai Oron, and Gert-Jan Reichart〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-481,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 Systematics in the incorporation of different elements in shells of marine organisms can be used to test calcification models and hence processes involved in precipitation of calcium carbonates. The observed link between sulfur and magnesium incorporation in shells of foraminifera, unicellar protists, provides insights into the mechanics behind shell formation. The observed patterns imply all species of foraminifera actively take up calcium and carbon in a coupled process.

Description: 〈b〉Geographic distribution of free-living marine nematodes in the Clarion–Clipperton Zone: implications for future deep-sea mining scenarios〈/b〉〈br〉 Freija Hauquier, Lara Macheriotou, Tania N. Bezerra, Great Egho, Pedro Martínez Arbizu, and Ann Vanreusel〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-492,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 Future mining operations in the deep sea provide a source of scientific uncertainty and call for detailed study of the ecosystem. We investigated one of the most diverse and abundant taxa present in deep-sea sediments, nematodes, and demonstrate the importance of sediment attributes for their communities. Especially species that are less common and have a limited spatial distribution will be vulnerable to mining-induced changes. Our findings can serve as a reference for future impact studies.

Description: 〈b〉An inter-comparison of total column-averaged nitrous oxide between ground-based FTIR TCCON and NDACC measurements at seven sites and comparisons with the GEOS-Chem model〈/b〉〈br〉 Minqiang Zhou, Bavo Langerock, Kelley C. Wells, Dylan B. Millet, Corinne Vigouroux, Mahesh Kumar Sha, Christian Hermans, Jean-Marc Metzger, Rigel Kivi, Pauli Heikkinen, Dan Smale, David F. Pollard, Nicholas Jones, Nicholas M. Deutscher, Thomas Blumenstock, Matthias Schneider, Mathias Palm, Justus Notholt, James W. Hannigan, and Martine De Mazière〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-340,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 N〈sub〉2〈/sub〉O is an important atmospheric gas, which is observed by two ground-based FTIR networks (TCCON and NDACC).The difference between NDACC and TCCON X〈sub〉N〈sub〉2〈/sub〉O〈/sub〉 measurements are discussed. It is found that the bias between two networks are within their combined uncertainties. However, TCCON measurements are affected by a priori profiles. In addition, the TCCON and NDACC N〈sub〉2〈/sub〉O measurements are compared with the GEOS-Chem model simulations.

Description: 〈b〉Joint retrieval of surface reflectance and aerosol properties with continuous variation of the state variables in the solution space – Part 1: theoretical concept〈/b〉〈br〉 Yves Govaerts and Marta Luffarelli〈br〉 Atmos. Meas. Tech., 11, 6589-6603, https://doi.org/10.5194/amt-11-6589-2018, 2018〈br〉 This paper presents a new algorithm for the joint retrieval of surface reflectance and aerosol properties with continuous variations of the state variables in the solution space. This algorithm, named CISAR (Combined Inversion of Surface and AeRosol), relies on a simple atmospheric vertical structure composed of two layers and an underlying surface. Surface anisotropic reflectance effects are taken into account and radiatively coupled with atmospheric scattering.

Description: 〈b〉Evaluating the performance of five different chemical ionization techniques for detecting gaseous oxygenated organic species〈/b〉〈br〉 Matthieu Riva, Pekka Rantala, Jordan E. Krechmer, Otso Peräkylä, Yanjun Zhang, Liine Heikkinen, Olga Garmash, Chao Yan, Markku Kulmala, Douglas Worsnop, and Mikael Ehn〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-407,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 The impact of aerosol particles on climate and air quality remains poorly understood due to multiple factors. One of the current limitations is the incomplete understanding of the contribution of oxygenated species, formed from the oxidation of volatile organic compounds (VOC), to aerosol formation. Taking advantage of recent mass spectrometric developments, we have evaluated and compared the capability of multiple state-of-the-art mass spectrometers to detect a wide variety of oxygenated VOC.

Description: 〈b〉Atomic oxygen number densities in the MLT region measured by solid electrolyte sensors on WADIS-2〈/b〉〈br〉 Martin Eberhart, Stefan Löhle, Boris Strelnikov, Jonas Hedin, Mikhail Khaplanov, Stefanos Fasoulas, Jörg Gumbel, Franz-Josef Lübken, and Markus Rapp〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-341,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 This paper describes the measurement of atomic oxygen in the upper atmosphere onboard sounding rockets using solid electrolyte sensors. Calibration of the sensors in the laboratory is explained in detail. Results from the WADIS-2 rocket campaign show profiles of atomic oxygen density with a high spatial resolution.

Description: 〈b〉From substrate to soil in a pristine environment – pedochemical, micromorphological and microbiological properties from soils on James Ross Island, Antarctica〈/b〉〈br〉 Lars A. Meier, Patryk Krauze, Isabel Prater, Fabian Horn, Carlos E. G. R. Schaefer, Thomas Scholten, Dirk Wagner, Carsten W. Mueller, and Peter Kühn〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-488,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 James Ross Island offers the opportunity to study the undisturbed interplay of microbial activity and pedogenesis. Soils from two sites representing coastal and inland conditions were chosen and analysed with a wide range of techniques to describe soil properties. We are able to show that coastal conditions go along with more intense weathering and therefore favor soil formation and that microbial communities are initially more affected by weathering and structure than by chemical parameters.

Description: 〈b〉The role of hydrodynamic and biogeochemistry on CO〈sub〉2〈/sub〉 flux and 〈i〉p〈/i〉CO〈sub〉2〈/sub〉 at the Amazon River mouth〈/b〉〈br〉 Diani F. S. Less, Alan C. Cunha, Henrique O. Sawakuchi, Vania Neu, Aline M. Valério, Nicholas D. Ward, Daimio C. Brito, Joel E. M. Diniz, William Gagne-Maynard, Carlos M. Abreu, Milton Kampel, Alex V. Krusche, and Jeffrey E. Richey〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-465,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 Biogeochemistry studies focused in carbon cycle in the Amazon River mouth are scarce. Our study provided a long-term quantification of CO〈sub〉2〈/sub〉 fluxes and 〈i〉p〈/i〉CO〈sub〉2〈/sub〉 and evaluation of the most important hydrodynamic, biogeochemical and meteorological parameters related to them. The highest FCO〈sub〉2〈/sub〉 and 〈i〉p〈/i〉CO〈sub〉2〈/sub〉 was obtained at high discharge season, water and air temperatures, dissolved oxygen, dissolved organic carbon, nitrate, dissolved inorganic nitrogen and pH could be considered predictors for 〈i〉p〈/i〉CO〈sub〉2〈/sub〉 and FCO〈sub〉2〈/sub〉.

Description: 〈b〉Meso-zooplankton structure and functioning in the western tropical South Pacific along the 20th parallel south during the OUTPACE survey (February–April 2015)〈/b〉〈br〉 François Carlotti, Marc Pagano, Loïc Guilloux, Katty Donoso, Valentina Valdés, Olivier Grosso, and Brian P. V. Hunt〈br〉 Biogeosciences, 15, 7273-7297, https://doi.org/10.5194/bg-15-7273-2018, 2018〈br〉 The paper characterizes the zooplankton community and plankton food web processes between New Caledonia and Tahiti (tropical South Pacific) during the austral summer 2015. In this region, the pelagic production depends on N〈sub〉2〈/sub〉 fixation by diazotroph microorganisms on which the zooplankton community feeds, supporting a pelagic food chain ending with valuable tuna fisheries. We estimated a contribution of up to 75 % of diazotroph‐derived nitrogen to zooplankton biomass in the Melanesian archipelago.

Description: 〈b〉Responses of an abyssal meiobenthic community to short-term burial with crushed nodule particles in the South-East Pacific〈/b〉〈br〉 Lisa Mevenkamp, Katja Guilini, Antje Boetius, Johan De Grave, Brecht Laforce, Dimitri Vandenberghe, Laszlo Vincze, and Ann Vanreusel〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-489,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 To elucidate potential effects of crushed nodule particle deposition on abyssal meiobenthos, we covered soft sediment in the Peru Basin (4200 m depth) with approx. 2 cm of this substrate for 11 days. About half of the meiobenthos migrated into the added crushed nodule layer and nematode feeding type proportions in the added layer were altered. The results indicate that substrate burial has a strong impact abyssal meiobenthos community structure and vertical distribution on the short term.

Description: 〈b〉Analysis of a warehouse fire smoke plume over Paris with an N〈sub〉2〈/sub〉 Raman lidar and an optical thickness matching algorithm〈/b〉〈br〉 Xiaoxia Shang, Patrick Chazette, and Julien Totems〈br〉 Atmos. Meas. Tech., 11, 6525-6538, https://doi.org/10.5194/amt-11-6525-2018, 2018〈br〉 For the first time, a ground-based N〈sub〉2〈/sub〉 Raman lidar sampled smoke plumes originating from a large accidental warehouse fire in the Paris area. We developed a new algorithm, dubbed top-down aerosol optical thickness matching, to characterize the optical properties of the smoke aerosols, without a pre-determined reference zone and in the presence of clouds. The industrial pollution episode was concomitant with the long-range transport of dust aerosols and the presence of an extended stratus cloud.

Description: 〈b〉Pre-launch calibration results of the TROPOMI payload on-board the Sentinel-5 Precursor satellite〈/b〉〈br〉 Quintus Kleipool, Antje Ludewig, Ljubiša Babić, Rolf Bartstra, Remco Braak, Werner Dierssen, Pieter-Jan Dewitte, Pepijn Kenter, Robin Landzaat, Jonatan Leloux, Erwin Loots, Peter Meijering, Emiel van der Plas, Nico Rozemeijer, Dinand Schepers, Daniel Schiavini, Joost Smeets, Giuseppe Vacanti, Frank Vonk, and Pepijn Veefkind〈br〉 Atmos. Meas. Tech., 11, 6439-6479, https://doi.org/10.5194/amt-11-6439-2018, 2018〈br〉 This paper reports on the pre-launch calibration of the TROPOMI instrument on board ESA's Sentinel 5P satellite. This calibration is needed to convert the raw instrument digital data to physical quantities like Earth radiance and Sun irradiance. From these quantities atmospheric properties can be derived. The paper shows that the chosen approach to calibration and analysis was successful and that the achieved accuracy makes high-quality observations of the Earth's atmosphere feasible.

Description: 〈b〉Better turbulence spectra from VAD scanning wind lidar〈/b〉〈br〉 Felix Kelberlau and Jakob Mann〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-410,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Lidars are devices that can measure wind velocities remotely from the ground. Their estimates are very accurate in the mean but wind speed fluctuations lead to measurement errors. The presented data processing methods mitigate several of the error causes. First, by making use of knowledge about the mean wind direction. And second, by determining the location of air packages and sensing them in the best moment. Both methods can be applied to existing wind lidars and results are very promising.

Description: 〈b〉Filtration artefacts in bacterial community composition can affect the outcome of dissolved organic matter biolability assays〈/b〉〈br〉 Joshua F. Dean, Jurgen R. van Hal, A. Johannes Dolman, Rien Aerts, and James T. Weedon〈br〉 Biogeosciences, 15, 7141-7154, https://doi.org/10.5194/bg-15-7141-2018, 2018〈br〉 Lakes, rivers, ponds and streams are significant contributors of the greenhouse gas carbon dioxide to the atmosphere. This is partly due to the decomposition of plant and soil organic matter transported through these aquatic systems by microbial communities. In determining how vulnerable this organic material is to decomposition during aquatic transport, we show that standardized treatments in experiments can affect the way microbial communities behave and potentially the experimental outcome.

Description: 〈b〉Bipolar carbon and hydrogen isotope constraints on the Holocene methane budget〈/b〉〈br〉 Jonas Beck, Michael Bock, Jochen Schmitt, Barbara Seth, Thomas Blunier, and Hubertus Fischer〈br〉 Biogeosciences, 15, 7155-7175, https://doi.org/10.5194/bg-15-7155-2018, 2018〈br〉 Ice core concentration and stable isotope measurements of atmospheric CH〈sub〉4〈/sub〉 give valuable insights into the CH〈sub〉4〈/sub〉 cycle of the past. New carbon and hydrogen stable isotope CH〈sub〉4〈/sub〉 data measured on ice from both Greenland and Antarctica over the Holocene allow us to draw conclusions on the methane emission processes. In particular, our results cast doubt on a hypothesis proposing early human land use to be responsible for the atmospheric methane concentration increase in the second half of the Holocene.

Description: 〈b〉Ecosystem fluxes of carbonyl sulfide in an old-growth forest: temporal dynamics and responses to diffuse radiation and heat waves〈/b〉〈br〉 Bharat Rastogi, Max Berkelhammer, Sonia Wharton, Mary E. Whelan, Frederick C. Meinzer, David Noone, and Christopher J. Still〈br〉 Biogeosciences, 15, 7127-7139, https://doi.org/10.5194/bg-15-7127-2018, 2018〈br〉 Carbonyl sulfide (OCS) has gained prominence as an independent tracer for gross primary productivity, which is usually modelled by partitioning net CO〈sub〉2〈/sub〉 fluxes. Here, we present a simple empirical model for estimating ecosystem-scale OCS fluxes for a temperate old-growth forest and find that OCS sink strength scales with independently estimated CO〈sub〉2〈/sub〉 uptake and is sensitive to the the fraction of downwelling diffuse light. We also examine the response of OCS and CO〈sub〉2〈/sub〉 fluxes to sequential heat waves.

Description: 〈b〉Reactive mercury flux measurements using cation exchange membranes〈/b〉〈br〉 Matthieu B. Miller, Mae S. Gustin, and Grant C. Edwards〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-360,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 In the atmosphere there are 2 gaseous forms of mercury (Hg), elemental (Hgo) and oxidized compounds (GOM). Hgo is oxidized by gases such as ozone and chlorine compounds. GOM is readily deposited to ecosystems and converted to methylmercury (a subtle neurotoxin). Here we explain development of a method for measurement of GOM deposition and emission associated with surfaces, and demonstrate that both occur. This has significant implications, because no one has been able to do this successfully.

Description: 〈b〉Comparative analysis of low-Earth orbit (TROPOMI) and geostationary (GeoCARB, GEO-CAPE) satellite instruments for constraining methane emissions on fine regional scales: application to the Southeast US〈/b〉〈br〉 Jian-Xiong Sheng, Daniel J. Jacob, Joannes D. Maasakkers, Yuzhong Zhang, and Melissa P. Sulprizio〈br〉 Atmos. Meas. Tech., 11, 6379-6388, https://doi.org/10.5194/amt-11-6379-2018, 2018〈br〉 We conduct Observing System Simulation Experiments to compare the ability of future satellite measurements of atmospheric methane columns for constraining methane emissions at the 25 km scale. We find that the geostationary instruments can do much better than TROPOMI and are less sensitive to cloud cover. GeoCARB observing twice a day would provide 70 % of the information from the nominal GEO-CAPE mission considered by NASA in response to the Decadal Survey of the US National Research Council.

Description: 〈b〉Pacific Decadal Oscillation and recent oxygen decline in the eastern tropical Pacific Ocean〈/b〉〈br〉 Olaf Duteil, Andreas Oschlies, and Claus W. Böning〈br〉 Biogeosciences, 15, 7111-7126, https://doi.org/10.5194/bg-15-7111-2018, 2018〈br〉 Oxygen-depleted regions of the Pacific Ocean are currently expanding, which is threatening marine habitats. Based on numerical simulations, we show that the decrease in the intensity of the trade winds and the subsequent slowdown of the oceanic currents lead to a reduction in oxygen supply. Our study suggests that the prevailing positive conditions of the Pacific Decadal Oscillation since 1975, a major source of natural variability, may explain a significant part of the current deoxygenation.

Description: 〈b〉Integrating multimedia models to assess nitrogen losses from the Mississippi River basin to the Gulf of Mexico〈/b〉〈br〉 Yongping Yuan, Ruoyu Wang, Ellen Cooter, Limei Ran, Prasad Daggupati, Dongmei Yang, Raghavan Srinivasan, and Anna Jalowska〈br〉 Biogeosciences, 15, 7059-7076, https://doi.org/10.5194/bg-15-7059-2018, 2018〈br〉 Elevated levels of nutrients in surface water, which originate from deposition of atmospheric N, drainage from agricultural fields, and discharges from sewage treatment plants, cause explosive algal blooms that impair water quality. The complex cycling of nutrients through the land, air, and water requires an integrated multimedia modeling system linking air, land surface, and stream processes to assess their sources, transport, and transformation in large river basins for decision making.

Description: 〈b〉Mg ∕ Ca and 〈strong〉〈i xmlns=""〉δ〈/i〉〈/strong〉〈sup〉18〈/sup〉O in living planktic foraminifers from the Caribbean, Gulf of Mexico and Florida Straits〈/b〉〈br〉 Anna Jentzen, Dirk Nürnberg, Ed C. Hathorne, and Joachim Schönfeld〈br〉 Biogeosciences, 15, 7077-7095, https://doi.org/10.5194/bg-15-7077-2018, 2018〈br〉 〈p〉Past ocean temperatures and salinities can be approximated from combined stable oxygen isotopes (〈span〉〈i〉δ〈/i〉〈sup〉18〈/sup〉O〈/span〉) and 〈span〉Mg〈/span〉 〈span〉∕〈/span〉 〈span〉Ca〈/span〉 measurements in fossil foraminiferal tests with varying success. To further refine this approach, we collected living planktic foraminifers by net sampling and pumping of sea surface water from the Caribbean Sea, the eastern Gulf of Mexico and the Florida Straits. Analyses of 〈span〉〈i〉δ〈/i〉〈sup〉18〈/sup〉O〈/span〉 and 〈span〉Mg〈/span〉 〈span〉∕〈/span〉 〈span〉Ca〈/span〉 in eight living planktic species (〈i〉Globigerinoides sacculifer〈/i〉, 〈i〉Orbulina universa〈/i〉, 〈i〉Neogloboquadrina dutertrei〈/i〉, 〈i〉Pulleniatina obliquiloculata〈/i〉, 〈i〉Globorotalia menardii〈/i〉, 〈i〉Globorotalia ungulata〈/i〉, 〈i〉Globorotalia truncatulinoides〈/i〉 and 〈i〉Globorotalia tumida〈/i〉) were compared to measured in situ properties of the ambient seawater (temperature, salinity and 〈span〉〈i〉δ〈/i〉〈sup〉18〈/sup〉O〈/span〉〈span〉〈sub〉seawater〈/sub〉〈/span〉) and fossil tests of underlying surface sediments. “Vital effects” such as symbiont activity and test growth cause 〈span〉〈i〉δ〈/i〉〈sup〉18〈/sup〉O〈/span〉 disequilibria with respect to the ambient seawater and a large scatter in foraminiferal 〈span〉Mg〈/span〉 〈span〉∕〈/span〉 〈span〉Ca〈/span〉. Overall, ocean temperature is the most prominent environmental influence on 〈span〉〈i〉δ〈/i〉〈sup〉18〈/sup〉O〈/span〉〈span〉〈sub〉calcite〈/sub〉〈/span〉 and 〈span〉Mg〈/span〉 〈span〉∕〈/span〉 〈span〉Ca〈/span〉. Enrichment of the heavier 〈span〉〈sup〉18〈/sup〉O〈/span〉 isotope in living specimens below the mixed layer and in fossil tests is clearly related to lowered in situ temperatures and gametogenic calcification. 〈span〉Mg〈/span〉 〈span〉∕〈/span〉 〈span〉Ca〈/span〉-based temperature estimates of 〈i〉G. sacculifer〈/i〉 indicate seasonal maximum accumulation rates on the seafloor in early spring (March) at Caribbean stations and later in the year (May) in the Florida Straits, related to the respective mixed layer temperatures of 〈span〉∼26〈/span〉 〈span〉〈sup〉∘〈/sup〉〈/span〉C. Notably, 〈i〉G. sacculifer〈/i〉 reveals a weak positive linear relationship between foraminiferal derived 〈span〉〈i〉δ〈/i〉〈sup〉18〈/sup〉O〈/span〉〈span〉〈sub〉seawater〈/sub〉〈/span〉 estimates and both measured in situ 〈span〉〈i〉δ〈/i〉〈sup〉18〈/sup〉O〈/span〉〈span〉〈sub〉seawater〈/sub〉〈/span〉 and salinity. Our results affirm the applicability of existing 〈span〉〈i〉δ〈/i〉〈sup〉18〈/sup〉O〈/span〉 and 〈span〉Mg〈/span〉 〈span〉∕〈/span〉 〈span〉Ca〈/span〉 calibrations for the reconstruction of past ocean temperatures and 〈span〉〈i〉δ〈/i〉〈sup〉18〈/sup〉O〈/span〉〈span〉〈sub〉seawater〈/sub〉〈/span〉 reflecting salinity due to the convincing accordance of proxy data in both living and fossil foraminifers, and in situ environmental parameters. Large vital effects and seasonally varying proxy signals, however, need to be taken into account.〈/p〉

Description: 〈b〉Introduction to the French GEOTRACES North Atlantic Transect (GA01): GEOVIDE cruise〈/b〉〈br〉 Géraldine Sarthou, Pascale Lherminier, Eric P. Achterberg, Fernando Alonso-Pérez, Eva Bucciarelli, Julia Boutorh, Vincent Bouvier, Edward A. Boyle, Pierre Branellec, Lidia I. Carracedo, Nuria Casacuberta, Maxi Castrillejo, Marie Cheize, Leonardo Contreira Pereira, Daniel Cossa, Nathalie Daniault, Emmanuel De Saint-Léger, Frank Dehairs, Feifei Deng, Floriane Desprez de Gésincourt, Jérémy Devesa, Lorna Foliot, Debany Fonseca-Batista, Morgane Gallinari, Maribel I. García-Ibáñez, Arthur Gourain, Emilie Grossteffan, Michel Hamon, Lars Eric Heimbürger, Gideon M. Henderson, Catherine Jeandel, Catherine Kermabon, François Lacan, Philippe Le Bot, Manon Le Goff, Emilie Le Roy, Alison Lefèbvre, Stéphane Leizour, Nolwenn Lemaitre, Pere Masqué, Olivier Ménage, Jan-Lukas Menzel Barraqueta, Herlé Mercier, Fabien Perault, Fiz F. Pérez, Hélène F. Planquette, Frédéric Planchon, Arnout Roukaerts, Virginie Sanial, Raphaëlle Sauzède, Catherine Schmechtig, Rachel U. Shelley, Gillian Stewart, Jill N. Sutton, Yi Tang, Nadine Tisnérat-Laborde, Manon Tonnard, Paul Tréguer, Pieter van Beek, Cheryl M. Zurbrick, and Patricia Zunino〈br〉 Biogeosciences, 15, 7097-7109, https://doi.org/10.5194/bg-15-7097-2018, 2018〈br〉 The GEOVIDE cruise (GEOTRACES Section GA01) was conducted in the North Atlantic Ocean and Labrador Sea in May–June 2014. In this special issue, results from GEOVIDE, including physical oceanography and trace element and isotope cyclings, are presented among 17 articles. Here, the scientific context, project objectives, and scientific strategy of GEOVIDE are provided, along with an overview of the main results from the articles published in the special issue.

Description: 〈b〉LISA: a lightweight stratospheric air sampler〈/b〉〈br〉 Joram J. D. Hooghiem, Marcel de Vries, Henk A. Been, Pauli Heikkinen, Rigel Kivi, and Huilin Chen〈br〉 Atmos. Meas. Tech., 11, 6785-6801, https://doi.org/10.5194/amt-11-6785-2018, 2018〈br〉 We have developed a lightweight stratospheric air sampler, named LISA, for measurements of CO〈sub〉2〈/sub〉, CH〈sub〉4〈/sub〉 and CO mole fractions. The LISA sampler is capable of grabbing stratospheric air samples at an altitude of up to 30 km and provides a useful tool for routine stratospheric measurements of both mole fractions and isotopic composition of trace gases.

Description: 〈b〉How representative are FLUXNET measurements of surface fluxes during temperature extremes?〈/b〉〈br〉 Sophie V. J. van der Horst, Andrew J. Pitman, Martin G. De Kauwe, Anna Ukkola, Gab Abramowitz, and Peter Isaac〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-502,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 Measurements of surface fluxes are taken around the world and are extremely valuable for understanding how the land and atmopshere interact, and how the land can amplify temerature extremes. However, do these measurements sample extreme temperatures, or are they biased to the average? We examine this question and highlight data that do measure surface fluxes under extreme conditions. This provides a way forward to help model developers improve their models.

Description: 〈b〉Biogeochemical evidence of anaerobic methane oxidation on active submarine mud volcanoes on the continental slope of the Canadian Beaufort Sea〈/b〉〈br〉 Dong-Hun Lee, Jung-Hyun Kim, Yung Mi Lee, Alina Stadnitskaia, Young Keun Jin, Helge Niemann, Young-Gyun Kim, and Kyung-Hoon Shin〈br〉 Biogeosciences, 15, 7419-7433, https://doi.org/10.5194/bg-15-7419-2018, 2018〈br〉 In this study, we provide first evidence of lipid biomarker patterns and phylogenetic identities of key microbes mediating anaerobic oxidation of methane (AOM) communities in active mud volcanoes (MVs) on the continental slope of the Canadian Beaufort Sea. Our lipid and 16S rRNA results indicate that archaea of the ANME-2c and ANME-3 clades are involved in AOM in the MVs investigated.

Description: 〈b〉Radiometric correction of observations from microwave humidity sounders〈/b〉〈br〉 Isaac Moradi, James Beauchamp, and Ralph Ferraro〈br〉 Atmos. Meas. Tech., 11, 6617-6626, https://doi.org/10.5194/amt-11-6617-2018, 2018〈br〉 Microwave (MW) satellite instruments are used for a variety of applications such as retrieving geophysical variables such as temperature and humidity. They are also assimilated into NWP models to improve the weather forecast. However, MW instruments are subject to radiometric and geometric errors. This study evaluates the observations from several MW instruments for radiometric errors and provides correction coefficients for the data that are biased.

Description: 〈b〉Composition and cycling of dissolved organic matter from tropical peatlands of coastal Sarawak, Borneo, revealed by fluorescence spectroscopy and PARAFAC analysis〈/b〉〈br〉 Yongli Zhou, Patrick Martin, and Moritz Müller〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-508,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 1 comment)〈br〉 We found that peatlands in coastal Sarawak, Borneo are exporting extremely humified organic matter, which dominates the riverine organic matter pool and conservatively mixes with seawater while the freshly produced fraction is low and stable in concentration at all salinities. We estimated that terrigenous fractions, which showed high photo-lability, still account for 20 % of the coastal dissolved organic carbon pool, implying the importance of peat-derived organic matter in coastal carbon cycle.

Description: 〈b〉Sensitivity of atmospheric CO〈sub〉2〈/sub〉 to regional variability in particulate organic matter remineralization depths〈/b〉〈br〉 Jamie D. Wilson, Stephen Barker, Neil R. Edwards, Philip B. Holden, and Andy Ridgwell〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-509,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 The remains of plankton rain down from the surface ocean to the deep ocean acting to store CO〈sub〉2〈/sub〉 in the deep ocean. We used a model of biology and ocean circulation to explore the importance of this process in different regions of the ocean. We found that the amount of CO〈sub〉2〈/sub〉 stored in the deep ocean is most sensitive to changes in the Southern Ocean. As plankton in the Southern Ocean may be most impacted by climate change, the amount of CO〈sub〉2〈/sub〉 they store in the deep ocean could also be affected.

Description: 〈b〉A novel approach to calibrating a photo-acoustic absorption spectrometer using polydisperse absorbing aerosol〈/b〉〈br〉 Katie Foster, Rudra Pokhrel, Matthew Burkhart, and Shane Murphy〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-413,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Optical properties of absorbing aerosol significantly impact global climate. Photoacoustic absorption spectrometers (PAS) have emerged as a popular technique for measuring aerosol absorption. There are no particle-based calibration methods for PAS instruments. We present a calibration approach utilizing polydisperse particles and a cavity attenuation phase shift instrument. This technique does not rely on specific substances with known refractive indices and is easily deployable in the field.

Description: 〈b〉Using computational fluid dynamics and field experiments to improve vehicle-based wind measurements for environmental monitoring〈/b〉〈br〉 Tara Hanlon and David Risk〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-354,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 In this study, we aimed to improve accuracy of wind speed and direction measurements from an anemometer mounted atop a research vehicle. Controlled field tests and computer simulations showed that the vehicle shape biases airflow above the vehicle. The results indicate that placing an anemometer at a significant height (〉 1 m) above the vehicle, and calibrating anemometer measurements for vehicle shape and wind angle, can be effective in reducing bias in measurements of wind speed and direction.

Description: 〈b〉BOREAS – a new MAX-DOAS profile retrieval algorithm for aerosols and trace gases〈/b〉〈br〉 Tim Bösch, Vladimir Rozanov, Andreas Richter, Enno Peters, Alexei Rozanov, Folkard Wittrock, Alexis Merlaud, Johannes Lampel, Stefan Schmitt, Marijn de Haij, Stijn Berkhout, Bas Henzing, Arnoud Apituley, Mirjam den Hoed, Jan Vonk, Martin Tiefengraber, Moritz Müller, and John Philip Burrows〈br〉 Atmos. Meas. Tech., 11, 6833-6859, https://doi.org/10.5194/amt-11-6833-2018, 2018〈br〉 A new MAX-DOAS profiling algorithm for aerosols and trace gases was developed. The performance of this novel algorithm was tested with the help of synthetic data and measurements from the CINDI-2 campaign in Cabauw, the Netherlands, in 2016.

Description: 〈b〉Apparatus for dry deposition of aerosols on snow〈/b〉〈br〉 Nicholas D. Beres and Hans Moosmüller〈br〉 Atmos. Meas. Tech., 11, 6803-6813, https://doi.org/10.5194/amt-11-6803-2018, 2018〈br〉 Particulate matter found in the atmosphere, or aerosols, can deposit on snow and ice and significantly change its reflectivity. Consequently, the timing of snow melt and snow water runoff is also changed. To study these processes, it is important to be able to deposit aerosols in a controlled manner on snow surfaces. Here, we present the design and demonstrate the use of an apparatus for deposition of common mineral dust and combustion aerosols.

Description: 〈b〉Low-pressure gas chromatography with chemical ionization mass spectrometry for quantification of multifunctional organic compounds in the atmosphere〈/b〉〈br〉 Krystal T. Vasquez, Hannah M. Allen, John D. Crounse, Eric Praske, Lu Xu, Anke C. Noelscher, and Paul O. Wennberg〈br〉 Atmos. Meas. Tech., 11, 6815-6832, https://doi.org/10.5194/amt-11-6815-2018, 2018〈br〉 Oxygenated volatile organic compounds (OVOCs) are difficult to measure in the atmosphere due to their high reactivity and low concentrations. This hinders our understanding of their impact on air quality and climate. Therefore, we have developed a field-deployable instrument capable of providing isomer-resolved measurements of OVOCs in the ambient air. Its performance is assessed through data collected both in the laboratory and during two field studies.

Description: 〈b〉Hydrothermal alteration of aragonitic biocarbonates: assessment of micro- and nanostructural dissolution–reprecipitation and constraints of diagenetic overprint from quantitative statistical grain-area analysis〈/b〉〈br〉 Laura A. Casella, Sixin He, Erika Griesshaber, Lourdes Fernández-Díaz, Martina Greiner, Elizabeth M. Harper, Daniel J. Jackson, Andreas Ziegler, Vasileios Mavromatis, Martin Dietzel, Anton Eisenhauer, Sabino Veintemillas-Verdaguer, Uwe Brand, and Wolfgang W. Schmahl〈br〉 Biogeosciences, 15, 7451-7484, https://doi.org/10.5194/bg-15-7451-2018, 2018〈br〉 Biogenic carbonates record past environmental conditions. Fossil shell chemistry and microstructure change as metastable biogenic carbonates are replaced by inorganic calcite. Simulated diagenetic alteration at 175 °C of different shell microstructures showed that (nacreous) shell aragonite and calcite were partially replaced by coarse inorganic calcite crystals due to dissolution–reprecipitation reactions. EBSD maps allowed for qualitative assessment of the degree of diagenetic overprint.

Description: 〈b〉Longitudinal contrast in turbulence along a  ∼ 19° S section in the Pacific and its consequences for biogeochemical fluxes〈/b〉〈br〉 Pascale Bouruet-Aubertot, Yannis Cuypers, Andrea Doglioli, Mathieu Caffin, Christophe Yohia, Alain de Verneil, Anne Petrenko, Dominique Lefèvre, Hervé Le Goff, Gilles Rougier, Marc Picheral, and Thierry Moutin〈br〉 Biogeosciences, 15, 7485-7504, https://doi.org/10.5194/bg-15-7485-2018, 2018〈br〉 The OUTPACE cruise took place between New Caledonia and French Polynesia. The main purpose was to understand how micro-organisms can survive in a very poor environment. One main source of nutrients is at depth, below the euphotic layer where micro-organisms live. The purpose of the turbulence measurements was to determine to which extent turbulence may 〈q〉uplift〈/q〉 nutrients into the euphotic layer. The origin of the turbulence that was found contrasted along the transect was also determined.

Description: 〈b〉Detecting layer height of smoke aerosols over vegetated land and water surfaces via oxygen absorption bands: Hourly results from EPIC/DSCOVR satellite in deep space〈/b〉〈br〉 Xiaoguang Xu, Jun Wang, Yi Wang, Jing Zeng, Omar Torres, Jeffrey S. Reid, Steven D. Miller, J. Vanderlei Martins, and Lorraine A. Remer〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-414,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Detecting aerosol layer height from space has been challenging. Tradition method relies on active sensors such as lidar that provides detailed vertical structure of aerosol profile, but is costly and has limited spatial coverage (it needs more than one year to have a global coverage). Here we developed a PASSIVE remote sensing technique that uses backscattered sunlight to retrieve smoke aerosol layer height over both water and vegetated surfaces from a sensor that is 1.5 M kms from the Earth.

Description: 〈b〉Aerosol optical properties derived from POLDER-3/PARASOL (2005–2013) over the western Mediterranean Sea – Part 1: Quality assessment with AERONET and in situ airborne observations〈/b〉〈br〉 Paola Formenti, Lydie Mbemba Kabuiku, Isabelle Chiapello, Fabrice Ducos, François Dulac, and Didier Tanré〈br〉 Atmos. Meas. Tech., 11, 6761-6784, https://doi.org/10.5194/amt-11-6761-2018, 2018〈br〉 Aerosol particles from natural and anthropogenic sources are climate regulators as they can counteract or amplify the warming effect of greenhouse gases, but are difficult to observe due to their temporal and spatial variability. Satellite sensors can provide the needed global coverage but need validation. In this paper we explore the capability of the POLDER-3 advanced space-borne sensor to observe aerosols over the western Mediterranean region.

Description: 〈b〉Investigation of observational error sources in multi Doppler radar vertical air motion retrievals: Impacts and possible solutions〈/b〉〈br〉 Mariko Oue, Pavlos Kollias, Alan Shapiro, Aleksandra Tatarevic, and Toshihisa Matsui〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-442,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 This study investigated impacts of the selected radar volume coverage pattern, the sampling time period, the number of radars used, and the added value of advection correction on the retrieval of vertical air motion from a multi-Doppler radar technique. The results suggest that the use of rapid-scan radars can substantially improve the quality of wind retrievals and that the retrieved wind field needs to be carefully used considering the limitations of the radar observing system.

Description: 〈b〉Decadal impacts of nitrogen additions on temperate forest carbon sinks: A data-model comparison〈/b〉〈br〉 Susan J. Cheng, Peter G. Hess, William R. Wieder, R. Quinn Thomas, Knute J. Nadelhoffer, Julius Vira, Danica L. Lombardozzi, Per Gundersen, Ivan J. Fernandez, Patrick Schleppi, Marie-Cécile Gruselle, Filip Moldan, and Christine L. Goodale〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-505,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 1 comment)〈br〉 Nitrogen pollution and fertilizer can change how much carbon is stored in plant and soil stocks. Understanding how much added nitrogen is recovered in plants or soils is critical to estimating the size of the future land carbon sink. We compared how nitrogen additions are recovered in modeled soil and plant stocks against data from long-term nitrogen addition experiments. We found that the model simulates recovery of added nitrogen into soils through a different process than found in the field.

Description: 〈b〉Intercomparison of MAX-DOAS Vertical Profile Retrieval Algorithms: Studies using Synthetic Data〈/b〉〈br〉 Udo Frieß, Steffen Beirle, Leonardo Alvarado Bonilla, Tim Bösch, Martina M. Friedrich, Francois Hendrick, Ankie Piters, Andreas Richter, Michel van Roozendael, Vladimir V. Rozanov, Elena Spinei, Jan-Lukas Tirpitz, Tim Vlemmix, Thomas Wagner, and Yang Wang〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-423,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a widely used measurement technique for the detection of a variety of atmospheric trace gases. It enables the retrieval of aerosol and trace gas vertical profiles in the atmospheric boundary layer using appropriate retrieval algorithms. In this study, the ability of eight profile retrieval algorithms to reconstruct vertical profiles is assessed on the basis of synthetic measurements.

Description: 〈b〉Improving algorithms and uncertainty estimates for satellite NO〈sub〉2〈/sub〉 retrievals: results from the quality assurance for the essential climate variables (QA4ECV) project〈/b〉〈br〉 K. Folkert Boersma, Henk J. Eskes, Andreas Richter, Isabelle De Smedt, Alba Lorente, Steffen Beirle, Jos H. G. M. van Geffen, Marina Zara, Enno Peters, Michel Van Roozendael, Thomas Wagner, Joannes D. Maasakkers, Ronald J. van der A, Joanne Nightingale, Anne De Rudder, Hitoshi Irie, Gaia Pinardi, Jean-Christopher Lambert, and Steven C. Compernolle〈br〉 Atmos. Meas. Tech., 11, 6651-6678, https://doi.org/10.5194/amt-11-6651-2018, 2018〈br〉 This paper describes a new, improved data record of 22+ years of coherent nitrogen dioxide (NO〈sub〉2〈/sub〉) pollution measurements from different satellite instruments. Our work helps to ensure that climate data are of sufficient quality to draw reliable conclusions and shape decisions. It shows how dedicated intercomparisons of retrieval sub-steps have led to improved NO〈sub〉2〈/sub〉 measurements from the GOME, SCIAMACHY, GOME-2(A), and OMI sensors, and how quality assurance of the new data product is achieved.

Description: 〈b〉Retrieval of aerosol microphysical and optical properties over land using a multimode approach〈/b〉〈br〉 Guangliang Fu and Otto Hasekamp〈br〉 Atmos. Meas. Tech., 11, 6627-6650, https://doi.org/10.5194/amt-11-6627-2018, 2018〈br〉 We implement a multimode approach in which each mode has fixed effective radius and effective variance. In this way the algorithm obtains more flexibility in describing the aerosol size distribution and avoids the high nonlinear dependence of the forward model on the aerosol size parameters. The synthetic and real data experiments show that multimode retrievals are good alternatives to the parametric two-mode approach.

Description: 〈b〉Characterization and application of artificial light sources for nighttime aerosol optical depth retrievals using the VIIRS Day/Night Band〈/b〉〈br〉 Jianglong Zhang, Shawn L. Jaker, Jeffrey S. Reid, Steven D. Miller, Jeremy Solbrig, and Travis D. Toth〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-424,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Using nighttime observations from Visible/Infrared Imager/Radiometer Suite (VIIRS) Day/Night band (DNB), the characteristics of artificial light sources are evaluated as functions of observation conditions, and incremental improvements are documented on nighttime aerosol retrievals using VIIRS DNB data on a regional scale. Results from the study indicate the potential of this method to begin filling critical gaps in diurnal AOT information at both regional and global scales.

Description: 〈b〉Shifts in organic sulfur cycling and microbiome composition in the red-tide causing dinoflagellate 〈i〉Alexandrium minutum〈/i〉 during a simulated marine heat wave〈/b〉〈br〉 Elisabeth Deschaseaux, James O'Brien, Nachshon Siboni, Katherina Petrou, and Justin R. Seymour〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-497,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 1 comment)〈br〉 Here we report that abrupt increases in temperature simulating marine heatwaves might have the potential to shape the physiological state and biogenic sulfur production in microalgae involved in harmful algal blooms. Changing physiology and biochemistry seem to trigger a shift in the bacteria community associated with these microalgae. Since microalgae and associated bacteria play an important role in climate regulation, this could have serious consequences for our future ocean and climate.

Description: 〈b〉Fluvial organic carbon fluxes from oil palm plantations on tropical peatland〈/b〉〈br〉 Sarah Cook, Mick J. Whelan, Chris D. Evans, Vincent Gauci, Mike Peacock, Mark H. Garnett, Lip Khoon Kho, Yit Arn Teh, and Susan E. Page〈br〉 Biogeosciences, 15, 7435-7450, https://doi.org/10.5194/bg-15-7435-2018, 2018〈br〉 This paper presents the first comprehensive assessment of fluvial organic carbon loss from oil palm plantations on tropical peat: a carbon loss pathway previously unaccounted for from carbon budgets. Carbon in the water draining four plantations in Sarawak was monitored across a 1-year period. Greater fluvial carbon losses were linked to sites with lower water tables. These data will be used to complete the carbon budget from these ecosystems and assess the full impact of this land conversion.

Description: 〈b〉An open platform for Aerosol InfraRed Spectroscopy analysis – AIRSpec〈/b〉〈br〉 Matteo Reggente, Rudolf Höhn, and Satoshi Takahama〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-332,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 1 comment)〈br〉 The infrared spectra of atmospheric particles are rich in chemical information, but require sophisticated statistical methods to extract information on account of their complex absorption profiles. We present an open software suite which makes current algorithms used for analysis of such spectra available to the community, with a browser-based interface for general users and modular architecture that facilitates addition of new methods by developers.

Description: 〈b〉Study of the diffraction pattern of cloud particles and respective response of Optical Array Probes〈/b〉〈br〉 Thibault Vaillant de Guélis, Alfons Schwarzenböck, Valery Shcherbakov, Christophe Gourbeyre, Bastien Laurent, Régis Dupuy, Pierre Coutris, and Christophe Duroure〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-437,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉Optical array probes (OAPs) are classical instrumental means to derive shape, size, and number concentration of cloud and precipitation particles from 2D images. However, recorded 2D images are subject to distortion based on the diffraction of light when particles are imaged out of the object plane of the optical device. This phenomenon highly affects retrievals of microphysical properties of cloud particles. Previous studies of this effect mainly focused on spherical droplets. In this study we propose a theoretical method to compute diffraction pattern of all kind of cloud particle shapes in order to simulate the response recorded by an OAP. To check the validity of this method, a series of experimental measurements have been performed with a 2D-S probe mounted on a test bench. Measurements are performed using spinning glass discs with imprinted non-circular opaque particle shapes.〈/p〉

Description: 〈b〉Development of an incoherent broadband cavity-enhanced absorption spectrometer for measurements of ambient glyoxal and NO〈sub〉2〈/sub〉 in a polluted urban environment〈/b〉〈br〉 Shuaixi Liang, Min Qin, Pinhua Xie, Jun Duan, Wu Fang, Yabai He, Jin Xu, Ke Tang, Fanhao Meng, Kaidi Ye, Jianguo Liu, and Wenqing Liu〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-430,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 A home-built instrument of an incoherent broadband cavity-enhanced absorption spectrometer for sensitive detection of CHOCHO and NO〈sub〉2〈/sub〉 in China's highly polluted environment is reported. NO〈sub〉2〈/sub〉 spectral profile measured using the same spectrometer is applied as a reference spectral profile in subsequent atmospheric spectral analysis and retrieval of NO〈sub〉2〈/sub〉 and CHOCHO. This will provide an idea for solving the problem of cross-interference of strongly absorbing gases in weakly absorbing gases.

Description: 〈b〉Analysis of spatial and temporal patterns of on-road NO〈sub〉2〈/sub〉 concentrations in Hong Kong〈/b〉〈br〉 Ying Zhu, Ka Lok Chan, Yun Fat Lam, Martin Horbanski, Denis Pöhler, Johannes Boll, Ivo Lipkowitsch, Sheng Ye, and Mark Wenig〈br〉 Atmos. Meas. Tech., 11, 6719-6734, https://doi.org/10.5194/amt-11-6719-2018, 2018〈br〉 The paper presents an investigation of spatio-temporal variability of street-level NO〈sub〉2〈/sub〉 in Hong Kong using mobile cavity-enhanced differential optical absorption spectroscopy (DOAS) and long-path DOAS. Measurements were conducted in December 2010 and March 2017. A significant decreasing trend in on-road NO〈sub〉2〈/sub〉 was found by comparing measurements taken in 2010 and 2017. Influences of changes in bus companies' operation strategies can also be observed from the measured NO〈sub〉2〈/sub〉 concentration maps.

Description: 〈b〉Chemical ionisation quadrupole mass spectrometer with an electrical discharge ion source for atmospheric trace gas measurement〈/b〉〈br〉 Philipp G. Eger, Frank Helleis, Gerhard Schuster, Gavin J. Phillips, Jos Lelieveld, and John N. Crowley〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-428,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 We present a Chemical Ionisation Quadrupole Mass Spectrometer (CI-QMS) with a novel discharge ion source. In addition to the expected detection of PAN, peracetic acid and ClNO〈sub〉2〈/sub〉, the instrument is also sensitive to SO〈sub〉2〈/sub〉, HCl and acetic acid through ion chemistry unique for our ion source. We present ionisation schemes along with illustrative data sets from field campaigns underlining the potential of the CI-QMS as an alternative to polonium, especially for application in the marine boundary layer.

Description: 〈b〉A fully autonomous ozone, aerosol and nighttime water vapor lidar: a synergistic approach to profiling the atmosphere in the Canadian oil sands region〈/b〉〈br〉 Kevin B. Strawbridge, Michael S. Travis, Bernard J. Firanski, Jeffrey R. Brook, Ralf Staebler, and Thierry Leblanc〈br〉 Atmos. Meas. Tech., 11, 6735-6759, https://doi.org/10.5194/amt-11-6735-2018, 2018〈br〉 Environment and Climate Change Canada has recently developed a fully autonomous, mobile lidar system to simultaneously measure the vertical profile of tropospheric ozone, aerosol and water vapor from near the ground to altitudes reaching 10–15 km. These atmospheric constituents play an important role in climate, air quality, and human and ecosystem health. Using an autonomous multi-lidar approach provides a continuous dataset rich in information for atmospheric process studies.

Description: 〈b〉First high resolution BrO column retrievals from TROPOMI〈/b〉〈br〉 Sora Seo, Andreas Richter, Anne-Marlene Blechschmidt, Ilias Bougoudis, and John Philip Burrows〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-365,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 The TROPOMI onboard the Copernicus Sentinel-5 Precursor platform can measure various atmospheric compositions at high spatial resolution and improved spectral resolution compared to its predecessors. Bromine monoxide (BrO) is one of the gases that can be derived from the measured radiances of TROPOMI using Differential Optical Absorption Spectroscopy (DOAS) method. In this paper, we present first retrieval results of BrO column amounts from TROPOMI observations on global and regional scales.

Description: 〈b〉Lidar temperature series in the middle atmosphere as a reference data set – Part 2: Assessment of temperature observations from MLS/Aura and SABER/TIMED satellites〈/b〉〈br〉 Robin Wing, Alain Hauchecorne, Philippe Keckhut, Sophie Godin-Beekmann, Sergey Khaykin, and Emily M. McCullough〈br〉 Atmos. Meas. Tech., 11, 6703-6717, https://doi.org/10.5194/amt-11-6703-2018, 2018〈br〉 We have compared 2433 nights of OHP lidar temperatures (2002–2018) to temperatures derived from the satellites SABER and MLS. We have found a winter stratopause cold bias in the satellite measurements with respect to the lidar (−6 K for SABER and −17 K for MLS), a summer mesospheric warm bias for SABER (6 K near 60 km), and a vertically structured bias for MLS (−4 to 4 K). We have corrected the satellite data based on the lidar-determined stratopause height and found a significant improvement.

Description: 〈b〉Footprint-scale cloud type mixtures and their impacts on Atmospheric Infrared Sounder cloud property retrievals〈/b〉〈br〉 Alexandre Guillaume, Brian H. Kahn, Eric J. Fetzer, Qing Yue, Gerald J. Manipon, Brian D. Wilson, and Hook Hua〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-415,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉A method is described to classify cloud mixtures of cloud top types, termed cloud scenes, using cloud type classification derived from the CloudSat radar (2B-CLDCLASS). The scale dependence of those cloud scenes is studied. For spatial scales near 45 km, only 16 out of 256 possible cloud scenes account for 90 % of all observations and contain either one, two, or three cloud types. The number of possible cloud scenes is shown to depend on spatial scale with a maximum number of 194 out of 256 possible scenes at a scale of 105 km and fewer cloud scenes at smaller and larger scales. The cloud scenes are used to assess the characteristics of spatially collocated Atmospheric Infrared Sounder (AIRS) thermodynamic phase and ice cloud property retrievals within scenes of varying cloud type complexity. The likelihood of ice and liquid phase detection strongly depends on the CloudSat-identified cloud scene type collocated with the AIRS footprint. Cloud scenes primarily consisting of cirrus, nimbostratus, altostratus and deep convection are dominated by ice phase detection, while stratocumulus, cumulus, and altocumulus are dominated by liquid and undetermined phase detection. Ice cloud particle size and optical thickness are largest for cloud scenes containing deep convection and cumulus, and are smallest for cirrus. Cloud scenes with multiple cloud types have small reductions in information content and slightly higher residuals of observed and modelled radiance compared to cloud scenes with single cloud types. These results will help advance the development of temperature, specific humidity, and cloud property retrievals from hyperspectral infrared sounders that include cloud microphysics in forward radiative transfer models.〈/p〉

Description: 〈b〉A physics-based approach to oversample multi-satellite, multispecies observations to a common grid〈/b〉〈br〉 Kang Sun, Lei Zhu, Karen Cady-Pereira, Christopher Chan Miller, Kelly Chance, Lieven Clarisse, Pierre-François Coheur, Gonzalo González Abad, Guanyu Huang, Xiong Liu, Martin Van Damme, Kai Yang, and Mark Zondlo〈br〉 Atmos. Meas. Tech., 11, 6679-6701, https://doi.org/10.5194/amt-11-6679-2018, 2018〈br〉 An agile, physics-based approach is developed to oversample irregular satellite observations to a high-resolution common grid. Instead of assuming each sounding as a point or a polygon as in previous methods, the proposed physical oversampling represents soundings as distributions of sensitivity on the ground. This sensitivity distribution can be determined by the spatial response function of each satellite sensor, parameterized as generalized 2-D super Gaussian functions.

Description: 〈b〉Aerosol Optical Depth comparison between GAW-PFR and AERONET-Cimel radiometers from long term (2005–2015) 1-minute synchronous measurements〈/b〉〈br〉 Emilio Cuevas, Pedro Miguel Romero-Campos, Natalia Kouremeti, Stelios Kazadzis, Rosa Delia García, Africa Barreto, Carmen Guirado-Fuentes, Ramón Ramos, Carlos Toledano, Fernando Almansa, and Julian Gröbner〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-438,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 A comprehensive comparison of more than 70000 synchronous 1-minute aerosol optical depth (AOD) data from three Global Atmosphere Watch-Precision Filter Radiometer (GAW-PFR) and 15 Aerosol Robotic Network-Cimel (AERONET-Cimel) radiometers was performed for the four nearby wavelengths (380, 440, 500 and 870 nm) in the period 2005–2015. The goal of this study is to assess whether their long term AOD data are comparable and consistent.

Description: 〈b〉Reciprocal bias compensation and ensuing uncertainties in model-based climate projections: pelagic biogeochemistry versus ocean mixing〈/b〉〈br〉 Ulrike Löptien and Heiner Dietze〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-491,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 1 comment)〈br〉 Anthropogenic greenhouse gas emissions trigger complex climate feedbacks. Output form Earth System Models provide a base for related political decision making. One challenge is to arrive at reliable model parameter estimates for the ocean biogeochemistry module. We illustrate pitfalls where flaws in the ocean module are masked by wrongly tuning the biogeochemistry and discuss ensuing uncertainties in climate projections.

Description: 〈b〉Particle wall-loss correction methods in smog chamber experiments〈/b〉〈br〉 Ningxin Wang, Spiro D. Jorga, Jeffery R. Pierce, Neil M. Donahue, and Spyros N. Pandis〈br〉 Atmos. Meas. Tech., 11, 6577-6588, https://doi.org/10.5194/amt-11-6577-2018, 2018〈br〉 The interaction of particles with the chamber walls has been a significant source of uncertainty when analyzing results of secondary organic aerosol formation experiments performed in Teflon chambers. We evaluated the performance of several particle wall-loss correction methods for aging experiments of 〈i〉α〈/i〉-pinene ozonolysis products. Experimental procedures are proposed for the characterization of particle losses during different stages of these experiments.

Description: 〈b〉Using collision-induced dissociation to constrain sensitivity of ammonia chemical ionization mass spectrometry (NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉-CIMS) to oxygenated volatile organic compounds〈/b〉〈br〉 Alexander Zaytsev, Martin Breitenlechner, Abigail R. Koss, Christopher Y. Lim, James C. Rowe, Jesse H. Kroll, and Frank N. Keutsch〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-425,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 We present the development of a chemical ionization mass spectrometer which can be operated with either hydronium (H〈sub〉3〈/sub〉O〈sup〉+〈/sup〉) or ammonium (NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉) as the reagent ion. We describe a mass spectrometric voltage scanning procedure based on collision-induced dissociation that allows us to determine the stability of detected ammonium-organic ions and hence constrain the sensitivity of the instrument to a wide range of organic compounds that cannot be calibrated directly.

Description: 〈b〉Improved retrievals of carbon dioxide from Orbiting Carbon Observatory-2 with the version 8 ACOS algorithm〈/b〉〈br〉 Christopher W. O'Dell, Annmarie Eldering, Paul O. Wennberg, David Crisp, Michael R. Gunson, Brendan Fisher, Christian Frankenberg, Matthäus Kiel, Hannakaisa Lindqvist, Lukas Mandrake, Aronne Merrelli, Vijay Natraj, Robert R. Nelson, Gregory B. Osterman, Vivienne H. Payne, Thomas E. Taylor, Debra Wunch, Brian J. Drouin, Fabiano Oyafuso, Albert Chang, James McDuffie, Michael Smyth, David F. Baker, Sourish Basu, Frédéric Chevallier, Sean M. R. Crowell, Liang Feng, Paul I. Palmer, Mavendra Dubey, Omaira E. García, David W. T. Griffith, Frank Hase, Laura T. Iraci, Rigel Kivi, Isamu Morino, Justus Notholt, Hirofumi Ohyama, Christof Petri, Coleen M. Roehl, Mahesh K. Sha, Kimberly Strong, Ralf Sussmann, Yao Te, Osamu Uchino, and Voltaire A. Velazco〈br〉 Atmos. Meas. Tech., 11, 6539-6576, https://doi.org/10.5194/amt-11-6539-2018, 2018〈br〉 〈p〉Since September 2014, NASA's Orbiting Carbon Observatory-2 (〈span〉OCO-2〈/span〉) satellite has been taking measurements of reflected solar spectra and using them to infer atmospheric carbon dioxide levels. This work provides details of the 〈span〉OCO-2〈/span〉 retrieval algorithm, versions 7 and 8, used to derive the column-averaged dry air mole fraction of atmospheric CO〈sub〉2〈/sub〉 (X〈sub〉CO〈sub〉2〈/sub〉〈/sub〉) for the roughly 100 000 cloud-free measurements recorded by 〈span〉OCO-2〈/span〉 each day. The algorithm is based on the Atmospheric Carbon Observations from Space (ACOS) algorithm which has been applied to observations from the Greenhouse Gases Observing SATellite (GOSAT) since 2009, with modifications necessary for 〈span〉OCO-2〈/span〉. Because high accuracy, better than 0.25 %, is required in order to accurately infer carbon sources and sinks from X〈sub〉CO〈sub〉2〈/sub〉〈/sub〉, significant errors and regional-scale biases in the measurements must be minimized. We discuss efforts to filter out poor-quality measurements, and correct the remaining good-quality measurements to minimize regional-scale biases. Updates to the radiance calibration and retrieval forward model in version 8 have improved many aspects of the retrieved data products. The version 8 data appear to have reduced regional-scale biases overall, and demonstrate a clear improvement over the version 7 data. In particular, error variance with respect to TCCON was reduced by 20 % over land and 40 % over ocean between versions 7 and 8, and nadir and glint observations over land are now more consistent. While this paper documents the significant improvements in the ACOS algorithm, it will continue to evolve and improve as the CO〈sub〉2〈/sub〉 data record continues to expand.〈/p〉

Description: 〈b〉Studies of the horizontal inhomogeneities in NO〈sub〉2〈/sub〉 concentrations above a shipping lane using ground-based MAX-DOAS and airborne imaging DOAS measurements〈/b〉〈br〉 André Seyler, Andreas C. Meier, Folkard Wittrock, Lisa Kattner, Barbara Mathieu-Üffing, Enno Peters, Andreas Richter, Thomas Ruhtz, Anja Schönhardt, Stefan Schmolke, and John P. Burrows〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-348,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 1 comment)〈br〉 This study describes a novel application of an 〈q〉onion peeling〈/q〉 like approach to MAX-DOAS measurements of shipping emissions aiming at investigating the inhomogenous NO〈sub〉2〈/sub〉 field over a shipping lane. Case studies for different wind conditions demonstrate the ability to derive the approximate plume positions in the observed area, which are in good agreement with simultaneous air-borne imaging DOAS measurements. NO〈sub〉2〈/sub〉 concentrations in a plume retrieved from both measurement techniques agree very well.

Description: 〈b〉NO〈sub〉2〈/sub〉 vertical profiles and column densities from MAX-DOAS measurements in Mexico City〈/b〉〈br〉 Martina Michaela Friedrich, Claudia Rivera, Wolfgang Stremme, Zuleica Ojeda, Josué Arellano, Alejandro Bezanilla, José Agustín García-Reynoso, and Michel Grutter〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-358,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 We present a new numerical code to retrieve NO〈sub〉2〈/sub〉 vertical column densities (vcd) and concentrations from previously retrieved slanted columns from spectroscopic measurements in visible and ultraviolet spectral range in different vertical viewing directions. We use this code on roughly 1.5 years of data from a measurement station located in the south of Mexico city and compare daily and monthly averages to averages of in-situ measurements. We show daily NO〈sub〉2〈/sub〉 vcd time series for a few example days.

Description: 〈b〉Turbulence measurements suggest high rates of new production over the shelf edge in the northeastern North Sea during summer〈/b〉〈br〉 Jørgen Bendtsen and Katherine Richardson〈br〉 Biogeosciences, 15, 7315-7332, https://doi.org/10.5194/bg-15-7315-2018, 2018〈br〉 New production based on nutrients entering the well-lit surface layer is important for understanding marine ecosystems. Measurements of primary production and turbulence across the shelf edge in the northeastern portion of the North Sea show that new production is concentrated around the shelf-edge zone. The shelf-edge zone is, therefore, a major nutrient supplier to the productive surface layer and makes this area important for higher trophic levels such as zooplankton and fish.

Description: 〈b〉Commercial traceability of 〈i〉Arapaima spp.〈/i〉 fisheries in the Amazon Basin: can biogeochemical tags be useful?〈/b〉〈br〉 Luciana A. Pereira, Roberto V. Santos, Marília Hauser, Fabrice Duponchelle, Fernando Carvajal, Christophe Pecheyran, Sylvain Bérail, and Marc Pouilly〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-471,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 1 comment)〈br〉 This study developed the first step for a chemical origin certification of Pirarucu fishery in the Amazon using isotopic tracers and resulted in a preliminary forensic tool. The geographic origin certification of farmed and wild endangered fishes contributes to secure the food and income to communities, the permanent management of fisheries stocks, the continuous advance of aquaculture, the consumer support to legal fisheries and the national and international regulation of natural resources.

Description: 〈b〉The impact of bath gas composition on the calibration of photoacoustic spectrometers with ozone at discrete visible wavelengths spanning the Chappuis band〈/b〉〈br〉 Michael I. Cotterell, Andrew J. Orr-Ewing, Kate Szpek, Jim M. Haywood, and Justin M. Langridge〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-409,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Photoacoustic spectroscopy provides measurements of absorption coefficient for aerosol and gas samples, but requires careful calibration and researchers often use concentrations of ozone. Recent work has shown that the bath gas composition impacts on the accuracy of this calibration at visible wavelengths. We explore further the role of bath gas, demonstrating that the calibration accuracy is optimal for a bath gas composed of 20 % oxygen and 80 % nitrogen at wavelengths of 405, 514 and 658 nm.

Description: 〈b〉Improvement of stratospheric aerosol extinction retrieval from OMPS/LP using a new aerosol model〈/b〉〈br〉 Zhong Chen, Pawan K. Bhartia, Robert Loughman, Peter Colarco, and Matthew DeLand〈br〉 Atmos. Meas. Tech., 11, 6495-6509, https://doi.org/10.5194/amt-11-6495-2018, 2018〈br〉 We describe the derivation of an improved aerosol size distribution (ASD) for the OMPS/LP retrieval algorithm. The new ASD uses a gamma function distribution that is derived from CARMA-calculated results. The new ASD also explains the spectral dependence of LP-measured radiances well. Initial comparisons with collocated extinction profiles retrieved at 676 nm from the SAGE III/ISS instrument show a significant improvement in agreement for the LP retrievals.

Description: 〈b〉Boundary-layer water vapor profiling using differential absorption radar〈/b〉〈br〉 Richard J. Roy, Matthew Lebsock, Luis Millán, Robert Dengler, Raquel Rodriguez Monje, Jose V. Siles, and Ken B. Cooper〈br〉 Atmos. Meas. Tech., 11, 6511-6523, https://doi.org/10.5194/amt-11-6511-2018, 2018〈br〉 The measurement of water vapor profiles inside clouds with high spatial resolution represents an outstanding problem in atmospheric remote sensing. Here we present measurements from a proof-of-concept millimeter-wave (170 GHz) cloud radar aimed at filling this observational gap, and demonstrate the ability to retrieve in-cloud water vapor profiles with high precision and resolution. This technology could meaningfully impact future satellite-based measurements of water vapor.

Description: 〈b〉Evolution of DARDAR-CLOUD ice cloud cloud retrieval: new parameters and impacts on the retrieved microphysical properties〈/b〉〈br〉 Quitterie Cazenave, Marie Ceccaldi, Julien Delanoë, Jacques Pelon, Silke Groß, and Andrew Heymsfield〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-397,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 The impact of ice clouds on the water cycle and radiative budget is still uncertain due to the complexity of cloud processes that makes it difficult to acquire adequate observations of ice cloud properties and parameterize them into climate and weather prediction models. In this paper we present the latest refinements brought to the DARDAR-CLOUD product, which contains ice cloud microphysical properties retrieved from the cloud radar and lidar measurements from the A-Train space mission.

Description: 〈b〉Effects of dry and wet Saharan dust deposition in the tropical North Atlantic Ocean〈/b〉〈br〉 Laura F. Korte, Franziska Pausch, Scarlett Trimborn, Corina P. D. Brussaard, Geert-Jan A. Brummer, Michèlle van der Does, Catarina V. Guerreiro, Laura T. Schreuder, Chris I. Munday, and Jan-Berend W. Stuut〈br〉 Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-484,2018〈br〉 〈b〉Manuscript under review for BG〈/b〉 (discussion: open, 0 comments)〈br〉 This paper shows the differences of nutrient release after dry and wet Saharan dust deposition in the tropical North Atlantic Ocean at 12° N. Incubation experiments were conducted along an east-west transect. Large differences were observed between both deposition types with wet deposition being the dominant source of phosphate, silicate, and iron. Both deposition types suggest that Saharan dust particles might be incorporated into marine snow aggregates and act as ballast mineral.

Description: Use of argon to measure gas exchange in turbulent mountain streams Robert O. Hall Jr. and Hilary L. Madinger Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-108,2018 Manuscript under review for BG (discussion: open, 0 comments) Streams exchange oxygen with the atmosphere, but this rate is difficult to measure. We added argon to small mountain streams to estimate gas exchange. We compared these rates with sulfur hexafluoride, an intense greenhouse gas. Argon worked well to measure gas exchange, but had higher than predicted rates than sulfur hexafluoride. Argon exchange is more likely to represent that for oxygen because they share similar physical properties. We suggest argon to measure gas exchange in small streams.

Description: Leaf phenology as one important driver of seasonal changes in isoprene emission in central Amazonia Eliane G. Alves, Julio Tóta, Andrew Turnipseed, Alex B. Guenther, José Oscar W. Vega Bustillos, Raoni A. Santana, Glauber G. Cirino, Julia V. Tavares, Aline Lopes, Bruce W. Nelson, Rodrigo A. de Souza, Dasa Gu, Trissevgeni Stavrakou, David K. Adams, Jin Wu, Scott Saleska, and Antonio O. Manzi Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-26,2018 Manuscript under review for BG (discussion: open, 0 comments) Isoprene fluxes vary seasonally with changes in environmental factors (e.g., solar radiation and temperature) and biological factors (e.g., leaf phenology). However, our understanding of seasonal patterns of isoprene fluxes and associated mechanistic controls are still limited, especially in Amazonian evergreen forests. In this paper, we aim to connect intensive, field-based measurements of canopy isoprene flux over a central Amazonian evergreen forest with meteorological observations and with tower-camera leaf phenology to improve understanding of patterns and causes of isoprene flux seasonality. Our results demonstrate that the highest isoprene emissions are observed during the dry and dry-to-wet transition seasons, whereas the lowest emissions were found during the wet-to-dry transition season. Our results also indicate that light and temperature can not totally explain the isoprene flux seasonality. Instead, the camera-derived leaf area index (LAI) of recently mature leaf-age class (e.g. leaf ages of 3–5 months) exhibits the highest correlation with observed isoprene flux seasonality ( R 2  = 0.59, p  

Description: The influence of the ocean circulation state on ocean carbon storage and CO 2 drawdown potential in an Earth system model Malin Ödalen, Jonas Nycander, Kevin I. C. Oliver, Laurent Brodeau, and Andy Ridgwell Biogeosciences, 15, 1367-1393, https://doi.org/10.5194/bg-15-1367-2018, 2018 We conclude that different initial states for an ocean model result in different capacities for ocean carbon storage due to differences in the ocean circulation state and the origin of the carbon in the initial ocean carbon reservoir. This could explain why it is difficult to achieve comparable responses of the ocean carbon system in model inter-comparison studies in which the initial states vary between models. We show that this effect of the initial state is quantifiable.

Description: Climate effects on vegetation vitality at the treeline of boreal forests of Mongolia Michael Klinge, Choimaa Dulamsuren, Stefan Erasmi, Dirk Nikolaus Karger, and Markus Hauck Biogeosciences, 15, 1319-1333, https://doi.org/10.5194/bg-15-1319-2018, 2018 Treelines are one of the most obvious borders between vegetation units and can easily be detected by remote sensing. They provide information on climate conditions and human impact on forest distribution. Performing a GIS analysis by combining different datasets leads to detection of the major determining factors for current forest distribution and helps to evaluate past and future conditions for tree growth. This is especially feasible for regions without extensive forest management.

Description: The pyrogeography of eastern boreal Canada from 1901 to 2012 simulated with the LPJ-LMfire model Emeline Chaste, Martin P. Girardin, Jed O. Kaplan, Jeanne Portier, Yves Bergeron, and Christelle Hély Biogeosciences, 15, 1273-1292, https://doi.org/10.5194/bg-15-1273-2018, 2018 A vegetation model was used to reconstruct fire activity from 1901 to 2012 in relation to changes in lightning ignition, climate, and vegetation in eastern Canada's boreal forest. The model correctly simulated the history of fire activity. The results showed that fire activity is ignition limited but is also greatly affected by both climate and vegetation. This research aims to develop a vegetation model that could be used to predict the future impacts of climate changes on fire activity.

Description: Towards an assessment of riverine dissolved organic carbon in surface waters of the western Arctic Ocean based on remote sensing and biogeochemical modeling Vincent Le Fouest, Atsushi Matsuoka, Manfredi Manizza, Mona Shernetsky, Bruno Tremblay, and Marcel Babin Biogeosciences, 15, 1335-1346, https://doi.org/10.5194/bg-15-1335-2018, 2018 Climate warming could enhance the load of terrigenous dissolved organic carbon (tDOC) of Arctic rivers. We show that tDOC concentrations simulated by an ocean–biogeochemical model in the Canadian Beaufort Sea compare favorably with their satellite counterparts. Over spring–summer, riverine tDOC contributes to 35 % of primary production and an equivalent of ~ 10 % of tDOC is exported westwards with the potential for fueling the biological production of the eastern Alaskan nearshore waters.

Description: Patterns and controls of soil respiration and its temperature sensitivity in grassland ecosystems across China Jiguang Feng, Jingsheng Wang, Yanjun Song, and Biao Zhu Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-83,2018 Manuscript under review for BG (discussion: open, 0 comments) Soil respiration (Rs), a key process in the terrestrial carbon cycle, is very sensitive to climate change. In this study, we synthesized 54 measurements of annual Rs and 171 estimates of Q 10 value (the temperature sensitivity of soil respiration) in grasslands across China. We quantitatively analyzed their spatial patterns and controlling factors in five grassland types, including temperate typical steppe, temperate meadow steppe, temperate desert steppe, alpine grassland, and warm-tropical grassland. Results showed that the mean (± SE) annual Rs was 582.0 ± 57.9 g C m −2  yr −1 across Chinese grasslands. Annual Rs significantly differed among grassland types, and positively correlated with mean annual temperature, mean annual precipitation, soil organic carbon content and aboveground biomass, but negatively correlated with latitude and soil pH ( P 〈 0.05). Among these factors, mean annual precipitation was the primary factor controlling the spatial variation of annual Rs in Chinese grasslands. The mean contributions of growing season Rs and heterotrophic respiration to annual Rs were 78.7 % and 72.8 %, respectively. Moreover, the mean (± SE) of Q 10 across Chinese grasslands was 2.60 ± 0.08, ranging from 1.03 to 8.13, and varied largely within and among grassland types, and among soil temperature measurement depths. Generally, the seasonal variation of soil respiration in Chinese grasslands cannot be well explained by soil temperature using the van't Hoff equation. Longitude and altitude were the dominant driving factors and accounted for 26.0 % of the variation in Q 10 derived by soil temperature at the depth of 5 cm. Overall, our findings advance our understanding of the spatial variation and environmental control of soil respiration and Q 10 across Chinese grasslands, and also improve our ability to predict soil carbon efflux under climate change on the regional scale.

Description: Manganese incorporation in living (stained) benthic foraminiferal shells: A bathymetric and in-sediment study in the Gulf of Lions (NW Mediterranean) Shauna Ní Fhlaithearta, Christophe Fontanier, Frans Jorissen, Aurélia Mouret, Adriana Dueñas-Bohórquez, Pierre Anschutz, Mattias B. Fricker, Detlef Günther, Gert J. de Lange, and Gert-Jan Reichart Biogeosciences Discuss., https//doi.org/10.5194/bg-2018-42,2018 Manuscript under review for BG (discussion: open, 0 comments) This study looks to how foraminifera interact with their geochemical environment in the seabed. We focus on the incorporation of the trace metal manganese (Mn), with the aim of developing a tool to reconstruct past pore water profiles. Manganese concentrations in foraminifera are investigated relative to their ecological preferences and geochemical environment. This study demonstrates that Mn in foraminiferal tests is a promising tool to reconstruct oxygen conditions in the seabed.