Connected subglacial lake drainage beneath Thwaites Glacier, West Antarctica The Cryosphere DOI 10.5194/tc-11-451-2017 8 February 2017 In this paper we investigate elevation changes of Thwaites Glacier, West Antarctica, one of the main sources of excess ice discharge into the ocean. We find that in early 2013, four subglacial lakes separated by 100 km drained suddenly, discharging more than 3 km3of water under the fastest part of the glacier in less than 6 months. Concurrent ice-speed measurements show only minor changes, suggesting that ice dynamics are not strongly sensitive to changes in water flow. Read more
A joint thermal and electromagnetic diagnostics approach for the inspection of thick walls Geoscientific Instrumentation, Methods and Data Systems DOI 10.5194/gi-6-81-2017 8 February 2017 A numerical inversion approach to detect and localize inclusions in thick walls under quasi-periodic natural solicitations is presented. It is based on a preliminary analysis of surface temperature field evolution with time. This analysis is improved by taking advantage of a priori information provided by ground-penetrating radar reconstructions. In this way, it is possible to improve the accuracy of the images achievable with the stand-alone thermal reconstruction method. Read more
A high-altitude balloon experiment to probe stratospheric electric fields from low latitudes Annales Geophysicae DOI 10.5194/angeo-35-189-2017 3 February 2017 Results from a high-altitude balloon experiment conducted from a low-latitude station in India are presented in this work. The objectives of this experiment were to probe and understand the processes driving the various electric field sources at low latitudes. During this experiment, electric fields in the range of 5–6 mV m−1 were observed at the balloon float altitude of 35 km. Atmospheric waves of few 100 km horizontal wavelength are suggested to be a potential source of these electric fields. Read more
Halogen chemistry reduces tropospheric O3 radiative forcing Atmospheric Chemistry and Physics DOI 10.5194/acp-17-1557-2017 31 January 2017 We model pre-industrial to present day changes using the GEOS-Chem global chemical transport model with halogens (Cl, Br, I). The model better captures pre-industrial O3observations with halogens included. Halogens buffer the tropospheric forcing of O3(RFTO[~3~]) from pre-industrial to present day, reducing RFTO[~3~]by 0.087 Wm−2. This reduction is greater than that from halogens on stratospheric O3(−0.05 Wm−2). This suggests that models that do not include halogens will overestimate RFTO[~3~]by ~ 25%. Read more
Decadal changes in global surface NOx emissions from multi-constituent satellite data assimilation Atmospheric Chemistry and Physics DOI 10.5194/acp-17-807-2017 27 January 2017 Global surface emissions of nitrogen oxides (NOx) over a 10-year period (2005–2014) are estimated from assimilation of multiple satellite datasets. We present detailed distributions of the estimated NOxemission distributions for all major regions, the diurnal, seasonal, and decadal variability. The estimated emissions show a positive trend over India, China, and the Middle East, and a negative trend over the United States, southern Africa, and western Europe. Read more
Snow fracture in relation to slab avalanche release: critical state for the onset of crack propagation The Cryosphere DOI 10.5194/tc-11-217-2017 27 January 2017 Based on DEM simulations we developed a new model for the onset of crack propagation in snow slab avalanche release. The model reconciles past approaches by considering the complex interplay between slab elasticity and the mechanical behavior of the weak layer including its structural collapse. The model agrees with extensive field data and can reproduce crack propagation on low-angle terrain and the decrease in critical crack length with increasing slope angle observed in numerical experiments. Read more
Representing nighttime and minimum conductance in CLM4.5: global hydrology and carbon sensitivity analysis using observational constraints Geoscientific Model Development DOI 10.5194/gmd-10-321-2017 23 January 2017 Earth’s terrestrial surface influences climate by exchanging carbon and water with the atmosphere through stomatal pores. However, most land-surface models, used to predict global carbon and water fluxes, estimate that water lost through stomata is less than what observations show. In this study, we integrate plant water loss data from 204 species into a global land surface model, finding that global estimates of plant water loss increase, soil moisture decreases, and carbon gain also decreases. Read more
Determination of the atmospheric lifetime and global warming potential of sulfur hexafluoride using a three-dimensional model Atmospheric Chemistry and Physics DOI 10.5194/acp-17-883-2017 20 January 2017 Sulfur hexafluoride (SF6) is a very potent greenhouse gas, which is present in the atmosphere only through its industrial use, for example as an electrical insulator. To estimate accurately the impact of SF6emissions on climate we need to know how long it persists in the atmosphere before being removed. Previous estimates of the SF6lifetime indicate a large degree of uncertainty. Here we use a detailed atmospheric model to calculate a current best estimate of the SF6lifetime. Read more
Chemical oxidative potential of secondary organic aerosol (SOA) generated from the photooxidation of biogenic and anthropogenic volatile organic compounds Atmospheric Chemistry and Physics DOI 10.5194/acp-17-839-2017 19 January 2017 Secondary organic aerosols (SOA) comprise a significant fraction of particulate matter (PM) and may have health implications. The water-soluble oxidative potentials of various SOA systems were determined using dithiothreitol consumption. Results from this study demonstrate that precursor identity was more influential than reaction condition in determining SOA oxidative potential and highlight a need to consider SOA contributions from anthropogenic hydrocarbons to PM-induced health effects. Read more
Radical chemistry at a rural site (Wangdu) in the North China Plain: observation and model calculations of OH, HO2 and RO2 radicals Atmospheric Chemistry and Physics DOI 10.5194/acp-17-663-2017 13 January 2017 In this study, we performed accurate OH measurements as well as selective HO2 and RO2 measurements at a rural site in North China Plain with state-of-the-art instruments newly developed. We confirmed the previous discovery on the enhancement of the OH in low NOx with which little O3 production was associated, and we found a missing RO2 source in high NOx which promoted higher O3 production. Our results are of vital importance for ozone abatement strategies currently under discussion for China. Read more
