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
Simulating the Greenland ice sheet under present-day and palaeo constraints including a new discharge parameterization The Cryosphere DOI 10.5194/tc-9-179-2015 5 February 2015 Ice discharge into the ocean from outlet glaciers is an important component of mass loss of the Greenland ice sheet. Here, we present a simple parameterization of ice discharge for coarse resolution ice sheet models, suitable for large ensembles or long-term palaeo simulations. This parameterization reproduces in a good approximation the present-day ice discharge compared with estimates, and the simulation of the present-day ice sheet elevation is considerably improved. Read more
Permafrost soils and carbon cycling SOIL DOI 10.5194/soil-1-147-2015 5 February 2015 The huge carbon stocks found in soils of the permafrost region are important to the global climate system because of their potential to decompose and release greenhouse gases into the atmosphere upon thawing. This review highlights permafrost characteristics, the influence of cryogenic processes on soil formation, organic carbon accumulation and distribution in permafrost soils, the vulnerability of this carbon upon permafrost thaw, and the role of permafrost soils in a changing climate. Read more
Glacier-surge mechanisms promoted by a hydro-thermodynamic feedback to summer melt The Cryosphere DOI 10.5194/tc-9-197-2015 5 February 2015 Here we present continuous GPS measurements and satellite synthetic-aperture-radar-based velocity maps from Basin-3, the largest drainage basin of the Austfonna ice cap, Svalbard. Our observations demonstrate strong links between surface-melt and multiannual ice-flow acceleration. Read more
