Rapid transport of East Asian pollution to the deep tropics Atmospheric Chemistry and Physics DOI 10.5194/acp-15-3565-2015 31 March 2015 We use observations and model calculations to show that “cold surges” occurring during Northern Hemisphere winter can rapidly transport East Asian pollution to equatorial Southeast Asia. As well as affecting atmospheric composition near the surface, we argue that strong convection can subsequently lift the polluted air masses to the tropical upper troposphere. This suggests a potentially important connection between midlatitude pollution sources and the lower stratosphere. Read more
Intercomparison of vertically resolved merged satellite ozone data sets: interannual variability and long-term trends Atmospheric Chemistry and Physics DOI 10.5194/acp-15-3021-2015 17 March 2015 Understanding ozone trends in the vertical are vital in terms of assessing the success of the Montreal Protocol. This paper compares and analyses the long-term trends in stratospheric ozone from seven new merged satellite data sets. The data sets largely agree well with each other, particularly for the negative trends seen in the early period 1984-1997. For the 1998-2011 period there is less agreement, but a clear shift from negative to mostly positive trends. Read more
Continuous and discontinuous variation in ecosystem carbon stocks with elevation across a treeline ecotone Biogeosciences DOI 10.5194/bg-12-1615-2015 12 March 2015 Here we investigate how ecosystem carbon stocks vary with elevation shifting from the closed forest to open alpine tundra, in the mountains of southern Norway. Above-ground carbon stocks decreased with elevation, with a clear breakpoint at the forest line, while the organic horizon soil carbon stocks increased linearly with elevation. Overall, ecosystem carbon stocks increased with elevation above the treeline and decreased with elevation below, demonstrating the importance of the treeline. Read more
A novel algorithm for detection of precipitation in tropical regions using PMW radiometers Atmospheric Measurement Techniques DOI 10.5194/amt-8-1217-2015 12 March 2015 The CCA algorithm is applicable to any modern passive microwave radiometer on board polar orbiting satellites; it has been developed using a data set of co-located SSMIS and TRMM-PR measurements and AMSU-MHS and TRMM-PR measurements. The algorithm shows a small rate of false alarms and superior detection capability and can efficiently detect (POD between 0.55 and 0.71) minimum rain rate varying from 0.14 mm/h (AMSU over ocean) to 0.41 (SSMIS over coast). Read more
The soil N cycle: new insights and key challenges SOIL DOI 10.5194/soil-1-235-2015 11 March 2015 Here, we review important insights with respect to the soil N cycle that have been made over the last decade, and present a personal view on the key challenges of future research. Read more
Improved routines to model the ocean carbonate system: mocsy 2.0 Geoscientific Model Development DOI 10.5194/gmd-8-485-2015 9 March 2015 We provide improved routines to model the ocean carbonate system, i.e., to compute ocean pH and related variables from dissolved inorganic carbon and total alkalinity. These routines (1) rely on the fastest available algorithm to solve the alkalinity-pH equation, which converges even under extreme conditions; (2) avoid common model approximations that lead to errors of 3% or more in computed variables; and (3) account for large pressure effects on subsurface pCO2, unlike other packages. Read more
Use of Ra isotopes to deduce rapid transfer of sediment-derived inputs off Kerguelen Biogeosciences DOI 10.5194/bg-12-1415-2015 5 March 2015 We investigated the origin and mechanisms of the natural iron fertilization that sustains a phytoplankton bloom downstream of the Kerguelen Islands. We used radium isotopes to trace the fate of shelf waters that may transport iron and other micronutrients towards offshore waters. We show that shelf waters are rapidly transferred offshore and may be transported across the polar front (PF). The PF may thus not be a strong physical barrier for chemical elements released by the shelf sediments. Read more
Using results from the PlioMIP ensemble to investigate the Greenland Ice Sheet during the mid-Pliocene Warm Period Climate of the Past DOI 10.5194/cp-11-403-2015 5 March 2015 Climate and ice sheet models are often used to predict the nature of ice sheets in Earth history. It is important to understand if such predictions are consistent between different models, especially in warm periods of relevance to the future. We use input from 15 different climate models to run one ice sheet model and compare the predictions over Greenland. We find that there are large differences between the predicted ice sheets for the warm Pliocene (c. 3 million years ago). Read more
Evaluation of coral reef carbonate production models at a global scale Biogeosciences DOI 10.5194/bg-12-1339-2015 4 March 2015 Production of calcium carbonate by coral reefs is important in the global carbon cycle. Using a global framework we evaluate four models of reef calcification against observed values. The temperature-only model showed significant skill in reproducing coral calcification rates. The absence of any predictive power for whole reef systems highlights the importance of coral cover and the need for an ecosystem modelling approach accounting for population dynamics in terms of mortality and recruitment. Read more
Does temperature affect the accuracy of vented pressure transducer in fine-scale water level measurement? Geoscientific Instrumentation, Methods and Data Systems DOI 10.5194/gi-4-65-2015 3 March 2015 This paper discussed the effect of temperature on the accuracy of submersible strain gauge pressure transducers. The results show that rapid change of temperature introduces errors in the water level reading while the absolute temperature is also related to the sensor errors. The former is attributed to venting and the latter is attributed to temperature compensation effects in the strain gauges. Performance tests are necessary before field deployment to ensure the data quality. Read more
Persistent after-effects of heavy rain on concentrations of ice nuclei and rainfall suggest a biological cause Atmospheric Chemistry and Physics DOI 10.5194/acp-15-2313-2015 3 March 2015 We show that atmospheric load of ice nuclei is enhanced for up to 20 days after key rainfall events. The rate of enhancement decreases exponentially with time. Rainfall quantity and frequency are increased for a similar duration and with similar exponential decreases thereby supporting the notion of rainfall feedback. We reveal series of significant feedback in rainfall patterns across Australia over the past century and marked changes in feedback patterns, and we indicate their locations. Read more
Quantitative high-resolution observations of soil water dynamics in a complicated architecture using time-lapse ground-penetrating radar Hydrology and Earth System Sciences DOI 10.5194/hess-19-1125-2015 2 March 2015 In this study, we analyze a set of high-resolution, surface-based, 2-D Ground-Penetrating Radar (GPR) observations of artificially induced subsurface water dynamics. In particular, we place close scrutiny on the evolution of the capillary fringe in a highly dynamic regime with surface based time-lapse GPR. We thoroughly explain all observed phenomena based on theoretical soil physical considerations and numerical simulations of both subsurface water flow and the expected GPR response. Read more
Identification and quantification of gaseous organic compounds emitted from biomass burning using two-dimensional gas chromatography–time-of-flight mass spectrometry Atmospheric Chemistry and Physics DOI 10.5194/acp-15-1865-2015 23 February 2015 This work represents the first application of two-dimensional gas chromatography to broadly characterize the gas-phase emissions of biomass burning, including comparisons among the emissions from burns of selected conifer, grass, crop residue, and peat fuel types. In these smoke samples, over 700 compounds were detected, which are discussed in the context of potential secondary organic aerosol formation. Read more
A 3-D shear velocity model of the southern North American and Caribbean plates from ambient noise and earthquake tomography Solid Earth DOI 10.5194/se-6-271-2015 20 February 2015 We compute a velocity model of the crust and uppermost mantle of Southern North America, Mexico and the Caribbean. We use a recent technique based on ‘ambient noise’ – or continuous seismic records – and a traditional one using earthquakes. Both techniques, together with the increased number of seismic stations in the region, allow us to obtain greater resolution than previous works. Some of its applications are to localize regional earthquakes and simulate ground motions. Read more
Drought in forest understory ecosystems – a novel rainfall reduction experiment Biogeosciences DOI 10.5194/bg-12-961-2015 17 February 2015 This paper introduces a novel rainfall reduction experiment to investigate drought effects on soil-forest-understory-ecosystems. An annual drought with a return period of 40 years was imposed, while other ecosystem variables (humidity, air & soil temperature) remained unaffected. The first year of drought showed considerable changes in soil moisture dynamics, which affected leaf stomatal conductance of understory species as well as evapotranspiration rates of the forest understory ecosystem. Read more
Ancient pre-glacial erosion surfaces preserved beneath the West Antarctic Ice Sheet Earth Surface Dynamics DOI 10.5194/esurf-3-139-2015 16 February 2015 We use ice penetrating radar data to identify a laterally continuous, gently sloping topographic block, comprising two surfaces separated by a distinct break in slope, preserved beneath the Institute and Möller Ice Streams, West Antarctica. We interpret these features as extensive erosion surfaces, showing that ancient (pre-glacial) surfaces can be preserved at low elevations beneath ice sheets. Different erosion regimes (e.g. fluvial and marine) may have formed these surfaces. Read more
Global trends in extreme precipitation: climate models versus observations Hydrology and Earth System Sciences DOI 10.5194/hess-19-877-2015 12 February 2015 We present a systematic comparison of changes in historical extreme precipitation in station observations (HadEX2) and 15 climate models from the CMIP5 (as the largest and most recent sets of available observational and modeled datasets), on global and continental scale for 1901-2010, using both parametric (linear regression) and non-parametric (the Mann-Kendall as well as Sen’s slope estimator) methods, taking care to spatially and temporally sample observations and models in comparable ways. Read more
Simulated anthropogenic CO2 storage and acidification of the Mediterranean Sea Biogeosciences DOI 10.5194/bg-12-781-2015 10 February 2015 Different observational-based estimates of CO2 uptake and resulting acidification of the Mediterranean Sea vary widely. A new study finds that even the smallest of those is an upper limit because the approach used assumes air-sea CO2 equilibrium. Then along with a lower limit from new fine-scale numerical model simulations, the authors bracket Mediterranean Sea CO2 uptake and acidification rates. They conclude that its rate of surface acidifcation is much like that for typical ocean waters. Read more
A high-resolution global-scale groundwater model Hydrology and Earth System Sciences DOI 10.5194/hess-19-823-2015 6 February 2015 In this paper we present a high resolution global-scale groundwater model of an upper aquifer. An equilibrium water table at its natural state is contructed. Aquifer parameterization is based on available global-datasets on lithology and conductivity combined with estimated aquifer thickness. The results showed groundwater levels are well simulated for many regions of the world. Simulated flow paths showed the relevance of including lateral groundwater flows in global scale hydrological models. Read more
Technical Note: Maximising accuracy and minimising cost of a potentiometrically regulated ocean acidification simulation system Biogeosciences DOI 10.5194/bg-12-713-2015 5 February 2015 This article describes a low-cost, easy set-up, ocean acidification simulation system that reliably mimics the effects of elevated atmospheric carbon dioxide on seawater chemistry. The accessible design of this system, along with our suggestions for the validation of pH control and characterisation of seawater chemistry, will enable researchers on a limited budget to generate high quality, repeatable data documenting the response of marine organisms to ocean acidification. Read more