Modified ion-Weibel instability as a possible source of wave activity at Comet 67P/Churyumov-Gerasimenko Annales Geophysicae DOI 10.5194/angeo-34-691-2016 31 August 2016 A new type of wave has been detected by the magnetometer of the Rosetta spacecraft close to comet P67/Churyumov-Gerasimenko. We provide the analytical model of this wave excitation from linear perturbation theory. A modified ion-Weibel instability is identified as source of this wave excited by a cometary current. The waves predominantly grow perpendicular to this current. A fan-like phase structure results from superposing the strongest growing waves in a cometary rest frame. Read more
New data on geology of the Southern Urals: a concise summary of research after the period of EUROPROBE activity Solid Earth DOI 10.5194/se-7-1269-2016 31 August 2016 The period between 1991 and 2005 was a time when many western geologists came to the Urals to get a closer look at this famous and extraordinarily rich region. The main reason was an openness policy of the USSR government, when foreigners were admitted to this area that was formerly almost closed. The co-operation of the western geologists with local specialists was very fruitful. The author aimed to describe the most interesting findings in Uralian geology after the learned guests left. Read more
Coherence among the Northern Hemisphere land, cryosphere, and ocean responses to natural variability and anthropogenic forcing during the satellite era Earth System Dynamics DOI 10.5194/esd-7-717-2016 30 August 2016 Using 3 decades of observational satellite and field data, we find that long-term changes in sea ice and sea level, plant phenology, and surface temperature are coherent with increases in atmospheric CO2 concentration and other global greenhouse gases. During the same period, natural causes of climate change should only have a net cooling long-term effect, suggesting the observed coherent pattern of changes across Earth’s biological and physical systems could only be due to human activities. Read more
Gravel threshold of motion: a state function of sediment transport disequilibrium? Earth Surface Dynamics DOI 10.5194/esurf-4-685-2016 29 August 2016 Accurately predicting gravel transport rates in mountain rivers is difficult because of feedbacks with channel morphology. River bed surfaces evolve during floods, influencing transport rates. I propose that the threshold of gravel motion is a state variable for channel reach evolution. I develop a new model to predict how transport thresholds evolve as a function of transport rate, and then use laboratory flume experiments to calibrate and validate the model. Read more
Why CO2 cools the middle atmosphere – a consolidating model perspective Earth System Dynamics DOI 10.5194/esd-7-697-2016 29 August 2016 Carbon dioxide, while warming the Earth’s surface, cools the atmosphere beyond about 15 km (the middle atmosphere). This cooling is considered a fingerprint of anthropogenic global warming, yet the physical reason behind it remains prone to misconceptions. Here we use a simple radiation model to illustrate the physical essence of stratospheric cooling, and a complex climate model to quantify how strongly different mechanisms contribute. Read more
A thermodynamic formulation of root water uptake Hydrology and Earth System Sciences DOI 10.5194/hess-20-3441-2016 29 August 2016 This theoretical paper describes the energy fluxes and dissipation along the flow paths involved in root water uptake, an approach that is rarely taken. We show that this provides useful additional insights for understanding the biotic and abiotic impediments to root water uptake. This approach shall be applied to explore efficient water uptake strategies and help locate the limiting processes in the complex soil–plant–atmosphere system. Read more
Impacts of aviation fuel sulfur content on climate and human health Atmospheric Chemistry and Physics DOI 10.5194/acp-16-10521-2016 24 August 2016 Using a coupled tropospheric chemistry-aerosol microphysics model this research paper investigates the effect of variations in aviation fuel sulfur content (FSC) on surface PM2.5 concentrations, increases in aviation-induced premature mortalities, low-level cloud condensation nuclei and radiative effect. When investigating the climatic impact of variations in FSC the ozone direct radiative effect, aerosol direct radiative effect and aerosol cloud albedo effect are quantified. Read more
Hemispherically asymmetric volcanic forcing of tropical hydroclimate during the last millennium Earth System Dynamics DOI 10.5194/esd-7-681-2016 23 August 2016 A band of intense rainfall exists near the equator known as the intertropical convergence zone, which can migrate in response to climate forcings. Here, we assess such migration in response to volcanic eruptions of varying spatial structure (Northern Hemisphere, Southern Hemisphere, or an eruption fairly symmetric about the equator). We do this using model simulations of the last millennium and link results to energetic constraints and the imprint eruptions may leave behind in past records. Read more
Satellite observations of stratospheric hydrogen fluoride and comparisons with SLIMCAT calculations Atmospheric Chemistry and Physics DOI 10.5194/acp-16-10501-2016 22 August 2016 HF, the dominant stratospheric fluorine reservoir, results from the atmospheric degradation of anthropogenic species such as CFCs, HCFCs, and HFCs. All are strong greenhouse gases, and CFCs and HCFCs deplete stratospheric ozone. We report the comparison of HF global distributions and trends measured by the ACE-FTS and HALOE satellite instruments with the output of SLIMCAT, a chemical transport model. The global HF trends reveal a slowing down in the rate of increase of HF since the 1990s. Read more
Annual Greenland accumulation rates (2009–2012) from airborne snow radar The Cryosphere DOI 10.5194/tc-10-1739-2016 11 August 2016 Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet through increasing surface melt, emphasizing the need to closely monitor surface mass balance in order to improve sea-level rise predictions. Here, we quantify the net annual accumulation over the Greenland Ice Sheet, which comprises the largest component of surface mass balance, at a higher spatial resolution than currently available using high-resolution, airborne-radar data. Read more
A review of marine geomorphometry, the quantitative study of the seafloor Hydrology and Earth System Sciences DOI 10.5194/hess-20-3207-2016 9 August 2016 Geomorphometry, the science of quantitative terrain characterization, has traditionally focused on the investigation of terrestrial landscapes. More recently, a suite of geomorphometric techniques have been applied to characterize the seafloor. The dynamic, four-dimensional nature of the marine environment and differences in data collection methods cause issues for geomorphometry that are specific to marine applications. This article offers the first review of marine geomorphometry to date. Read more
Large gain in air quality compared to an alternative anthropogenic emissions scenario Atmospheric Chemistry and Physics DOI 10.5194/acp-16-9771-2016 4 August 2016 Three 30-year simulations of past atmospheric composition changes were performed using different anthropogenic emissions of pollutants accounting or not for the applied air quality legislation and accounting for the year–to–year observed climate and natural emissions variability. The actual benefit of applied legislation along with technological advances is higher than what is usually calculated by a simple comparison of today’s atmosphere against a constant anthropogenic emissions simulation. Read more
Drift simulation of MH370 debris using superensemble techniques Natural Hazards and Earth System Sciences DOI 10.5194/nhess-16-1623-2016 27 July 2016 In March 2014, a commercial airliner vanished without a trace. The main wreckage of the plane was never recovered, except for some small parts that washed up more than 17 months after the disappearance. In this paper we show a method to model the most likely trajectories of floating debris from the aircraft. The results show that the assumed area of the crash site is compatible with the recovered debris and predict that further debris may be found along the African east coast. Read more
Wave climate in the Arctic 1992–2014: seasonality and trends The Cryosphere DOI 10.5194/tc-10-1605-2016 26 July 2016 Satellite observations show the Arctic sea ice has decreased the last 30 years. From our wave model hindcast and satellite altimeter datasets we observe profound increasing wave heights, which are caused by the loss of sea ice and not the driving winds. If ice-free conditions persist later into fall, then regions like the Beaufort–Chukchi Sea will be prone to developing larger waves since the driving winds are strong this time of year. Read more
Observed and simulated full-depth ocean heat-content changes for 1970–2005 Ocean Science DOI 10.5194/os-12-925-2016 26 July 2016 A new method of observing ocean heat content throughout the entire ocean depth is provided. The new method is compared with simulated ocean heat content changes from climate models. The comparisons are carried out in various depth layers of the ocean waters. It is found that there is excellent agreement between the models and the observations. Furthermore, we propose that changes to ocean heat content be used as a fundamental metric to evaluate climate models. Read more
Using video games for volcanic hazard education and communication: an assessment of the method and preliminary results Natural Hazards and Earth System Sciences DOI 10.5194/nhess-16-1673-2016 22 July 2016 Here, we aim to better understand the potential for using video games in volcanic hazard education with at-risk communities. A study using a bespoke-designed video game – St. Vincent’s Volcano – was trialled on the Caribbean island of St. Vincent in 2015. Preliminary data analysis demonstrates 94 % of study participants had an improved knowledge of volcanic hazards after playing the game, leading us to conclude that video games could be a logical progression for education and outreach activities. Read more
A post-wildfire response in cave dripwater chemistry Hydrology and Earth System Sciences DOI 10.5194/hess-20-2745-2016 21 July 2016 Our current understanding of wildfires on Earth is filled with knowledge gaps. One reason for this is our poor record of fire in natural archives. We open the possibility for speleothems to be “a missing piece to the fire-puzzle”. We find by effecting surface evaporation and transpiration rates, wildfires can have a multi-year impact on speleothem, forming dripwater hydrology and chemistry. We open a new avenue for speleothems as potential palaeo-fire archives. Read more
The PRISM4 (mid-Piacenzian) paleoenvironmental reconstruction Climate of the Past DOI 10.5194/cp-12-1519-2016 13 July 2016 Past intervals in Earth history provide unique windows into conditions much different than those observed today. We investigated the paleoenvironments of a past warm interval (~ 3 million years ago). Our reconstruction includes data sets for surface temperature, vegetation, soils, lakes, ice sheets, topography, and bathymetry. These data are being used along with global climate models to expand our understanding of the climate system and to help us prepare for future changes. Read more
Can mussels be used as sentinel organisms for characterization of pollution in urban water systems? Hydrology and Earth System Sciences DOI 10.5194/hess-20-2679-2016 8 July 2016 We assessed if nitrogen stable isotopes in mussels are a suitable indicator, capable of resolving spatial and temporal variability of nutrient pollution in an urban estuary. Our results highlight the value of using stable isotope analysis as an integrative tool to establish an understanding of local processes and pollution levels in theses urban aquatic systems. We suggest that mussels can become a robust tool for the detection of emerging anthropogenic pollutants of concern in urban water systems. Read more
Multi-scale statistical analysis of coronal solar activity Nonlinear Processes in Geophysics DOI 10.5194/npg-23-175-2016 8 July 2016 We use temperature maps of the solar corona for three regions and use a technique that separates multiple timescales and space scales to show that the small-scale temperature fluctuations appear more frequently prior to the occurrence of a solar flare, in comparison with the same region after the flare and with a quiet region. We find that, during the flare, energy flows from large to small scales and heat transport associated with a heat front is convective along and diffusive across the front. Read more