Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 1: Elementary models Annales Geophysicae DOI 10.5194/angeo-34-55-2016 19 January 2016 This paper introduces a new method for mapping electric fields in the magnetosphere along geomagnetic field lines. This is important for conjugate studies of electric fields measured in the ionosphere by SuperDARN radars, and at spacecraft carrying electric field probes. First elementary methods in a dipole field are reviewed and then the theory of of a new method described for general magnetic field models. The method is tested in a dipole model with a Harris magnetotail field. Read more
Overview of the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Forcing on the Mediterranean Climate (ChArMEx/ADRIMED) summer 2013 campaign Atmospheric Chemistry and Physics DOI 10.5194/acp-16-455-2016 19 January 2016 The aim of this article is to present an experimental campaign over the Mediterranean focused on aerosol-radiation measurements and modeling. Results indicate an important atmospheric loading associated with a moderate absorbing ability of mineral dust. Observations suggest a complex vertical structure and size distributions characterized by large aerosols within dust plumes. The radiative effect is highly variable, with negative forcing over the Mediterranean and positive over northern Africa. Read more
Aggregation in environmental systems – Part 1: Seasonal tracer cycles quantify young water fractions, but not mean transit times, in spatially heterogeneous catchments Hydrology and Earth System Sciences DOI 10.5194/hess-20-279-2016 19 January 2016 Catchment mean transit times have been widely inferred from seasonal cycles of environmental tracers in precipitation and streamflow. Here I show that these cycles yield strongly biased estimates of mean transit times in spatially heterogeneous catchments (and, by implication, in real-world catchments). However, I also show that these cycles can be used to reliably estimate the fraction of “young” water in streamflow, meaning water that fell as precipitation less than roughly 2–3 months ago. Read more
Aggregation in environmental systems – Part 2: Catchment mean transit times and young water fractions under hydrologic nonstationarity Hydrology and Earth System Sciences DOI 10.5194/hess-20-299-2016 19 January 2016 Here I show that seasonal tracer cycles yield strongly biased estimates of mean transit times in nonstationary catchments (and, by implication, in real-world catchments). However, they can be used to reliably estimate the fraction of “young” water in streamflow, meaning water that fell as precipitation less than roughly 2–3 months ago. This young water fraction varies systematically between high and low flows and may help in characterizing controls on stream chemistry. Read more
Diagnosing hydrological limitations of a land surface model: application of JULES to a deep-groundwater chalk basin Hydrology and Earth System Sciences DOI 10.5194/hess-20-143-2016 18 January 2016 This paper presents a strategy to diagnose hydrological limitations of a Land Surface Model. It includes the adaptation of the model for hydrological applications and highlights challenges faced while moving towards high resolution modelling. Read more
Topology of sustainable management of dynamical systems with desirable states: from defining planetary boundaries to safe operating spaces in the Earth system Earth System Dynamics DOI 10.5194/esd-7-21-2016 18 January 2016 The debate about a safe and just operating space for humanity and the possible pathways towards and within it requires an analysis of the inherent dynamics of the Earth system and of the options for influencing its evolution. We present and illustrate with examples a conceptual framework for performing such an analysis not in a quantitative, optimizing mode, but in a qualitative way that emphasizes the main decision dilemmas that one may face in the sustainable management of the Earth system. Read more
The Imbert Formation of northern Hispaniola: a tectono-sedimentary record of arc–continent collision and ophiolite emplacement in the northern Caribbean subduction–accretionary prism Solid Earth DOI 10.5194/se-7-11-2016 15 January 2016 New stratigraphical, structural, geochemical, and geochronological data from the northern Caribbean orogenic belt indicate that the Imbert Fm constitutes a coarsening-upward stratigraphic sequence that records the transition of the sedimentation from a pre-collisional forearc to a syn-collisional piggy-back basin in the lower-to-middle Eocene. This piggy-back basin was transported to the top of the Puerto Plata ophiolitic slab as it was emplaced onto the North America continental margin units. Read more
The assessment of a global marine ecosystem model on the basis of emergent properties and ecosystem function: a case study with ERSEM Geoscientific Model Development DOI 10.5194/gmd-9-59-2016 15 January 2016 To use models to inform policy or to forecast the impact of climate change, the model must first be shown to be a valid representation of the ecosystem. Here we show an novel method to validate a marine model using its ability to represent ecosystem function. These relationships are the community structure, the carbon to chlorophyll ratio and the stoichiometric balance of the ecosystem. These methods are powerful, valid over large spatial scales and independent of the circulation model. Read more
Committed retreat of Smith, Pope, and Kohler Glaciers over the next 30 years inferred by transient model calibration The Cryosphere DOI 10.5194/tc-9-2429-2015 21 December 2015 We calibrate a time-dependent ice model through optimal fit to transient observations of surface elevation and velocity, a novel procedure in glaciology and in particular for an ice stream with a dynamic grounding line. We show this procedure gives a level of confidence in model projections that cannot be achieved through more commonly used glaciological data assimilation methods. We show that Smith Glacier is in a state of retreat regardless of climatic forcing for the next several decades. Read more
Hidden biosphere in an oxygen-deficient Atlantic open-ocean eddy: future implications of ocean deoxygenation on primary production in the eastern tropical North Atlantic Biogeosciences DOI 10.5194/bg-12-7467-2015 21 December 2015 The waters of the tropical Atlantic Open Ocean usually contain comparably high concentrations of oxygen. Now, it became clear that there are watermasses related to eddies that are nearly anoxic. We surveyed one of those eddies and found a biosphere that largely differed from the usual biosphere present in this area with a specific community responsible for primary production and for degradation processes. Further, we found the very first indication for active nitrogen loss in the open Atlantic. Read more
