Process-level model evaluation: a snow and heat transfer metric The Cryosphere DOI 10.5194/tc-11-989-2017 20 April 2017 This work defines a metric for evaluation of a specific model snow process, namely, heat transfer through snow into soil. Heat transfer through snow regulates the difference in air temperature versus soil temperature. Accurate representation of the snow heat transfer process is critically important for accurate representation of the current and future state of permafrost. Utilizing this metric, we can clearly identify models that can and cannot reasonably represent snow heat transfer. Read more
Divergence of seafloor elevation and sea level rise in coral reef ecosystems Biogeosciences DOI 10.5194/bg-14-1739-2017 20 April 2017 We report regional-scale erosion of coral reef ecosystems in the Atlantic, Caribbean, and Pacific oceans determined by measuring changes in seafloor elevation. The magnitude of seafloor elevation loss has increased local sea level rise, causing water depths not predicted until near 2100, placing coastal communities at elevated and accelerating risk from hazards such as waves, storms, and tsunamis. Our results have broad implications for coastal resource and safety management. Read more
Accounting for the climate–carbon feedback in emission metrics Earth System Dynamics DOI 10.5194/esd-8-235-2017 10 April 2017 Emission metrics such as GWP or GTP are used to put non-CO2species on aCO2-equivalentscale. In the fifth IPCC report the metrics are inconsistent, as the climate–carbon feedback is included only for CO2but not for non-CO2species. Here, we simulate a new impulse response function for the feedback, and we use it to correct the metrics. For instance, 1 g of CH4is equivalent to 31 g of CO2(instead of 28 g) following the corrected GWP100 metric. It is 34 g if other factors are also updated. Read more
Constraining N2O emissions since 1940 using firn air isotope measurements in both hemispheres Atmospheric Chemistry and Physics DOI 10.5194/acp-17-4539-2017 5 April 2017 Nitrous oxide is the third most important anthropogenic greenhouse gas with an increasing mole fraction. To understand its natural and anthropogenic sources we employ isotope measurements. Results show that while the N2O mole fraction increases, its heavy isotope content decreases. The isotopic changes observed underline the dominance of agricultural emissions especially at the early part of the record, whereas in the later decades the contribution from other anthropogenic sources increases. Read more
Characterization of the long-term radiosonde temperature biases in the upper troposphere and lower stratosphere using COSMIC and Metop-A/GRAS data from 2006 to 2014 Atmospheric Chemistry and Physics DOI 10.5194/acp-17-4493-2017 4 April 2017 Radiosonde observations (RAOBs) have provided the only long-term global in situ temperature measurements since 1958. In this study, we use Global Positioning System (GPS) radio occultation (RO) temperature data from 2006 to 2014 to characterize the inter-seasonal and interannual variability of temperature biases in the lower stratosphere. Results from this study also demonstrate the feasibility to use RO data to correct RAOB temperature biases for different sensor types. Read more
Drought and flood in the Anthropocene: feedback mechanisms in reservoir operation Earth System Dynamics DOI 10.5194/esd-8-225-2017 27 March 2017 There is still little understanding about the dynamics emerging from human–water interactions. As a result, policies and measures to reduce the impacts of floods and droughts often lead to unintended consequences. This paper proposes a research agenda to improve our understanding of human–water interactions, and presents an initial attempt to model the reciprocal effects between water management, droughts, and floods. Read more
Surge dynamics and lake outbursts of Kyagar Glacier, Karakoram The Cryosphere DOI 10.5194/tc-11-723-2017 21 March 2017 Recent surging of Kyagar Glacier (Karakoram) caused a hazardous ice-dammed lake to form and burst in 2015 and 2016. We use remotely sensed glacier surface velocities and surface elevation to observe dramatic changes in speed and mass distribution during the surge. The surge was hydrologically controlled with rapid summer onset and dramatic termination following lake outburst. Since the surge, the potential outburst hazard has remained high, and continued remote monitoring is crucial. Read more
Manganese in the west Atlantic Ocean in the context of the first global ocean circulation model of manganese Biogeosciences DOI 10.5194/bg-14-1123-2017 9 March 2017 We ran a global ocean model to understand manganese (Mn), a biologically essential element. Our model shows that (i) in the deep ocean, dissolved [Mn] is mostly homogeneous ca. 0.10–0.15 nM. The model reproduces this with a threshold on MnO2 of 25 pM, suggesting a minimal particle concentration is needed before aggregation and removal become efficient. (ii) The observed distinct hydrothermal signals are produced by assuming both a strong source and a strong removal of Mn near hydrothermal vents. Read more
The European 2015 drought from a climatological perspective Hydrology and Earth System Sciences DOI 10.5194/hess-21-1397-2017 8 March 2017 This paper analyses the European summer drought of 2015 from a climatological perspective, including its origin and spatial and temporal development, and how it compares with the 2003 event. It discusses the main contributing factors controlling the occurrence and persistence of the event: temperature and precipitation anomalies, blocking episodes and sea surface temperatures. The results represent the outcome of a collaborative initiative of members of UNESCO’s FRIEND-Water program. Read more
Structural uncertainty in air mass factor calculation for NO2 and HCHO satellite retrievals Atmospheric Measurement Techniques DOI 10.5194/amt-10-759-2017 7 March 2017 Choices and assumptions made to represent the state of the atmosphere introduce an uncertainty of 42 % in the air mass factor calculation in trace gas satellite retrievals in polluted regions. The AMF strongly depends on the choice of a priori trace gas profile, surface albedo data set and the correction method to account for clouds and aerosols. We call for well-designed validation exercises focusing on situations when AMF structural uncertainty has the highest impact on satellite retrievals. Read more
Characteristics and causes of Deep Western Boundary Current transport variability at 34.5∘ S during 2009–2014 Ocean Science DOI 10.5194/os-13-175-2017 2 March 2017 This study investigates the variability of the Deep Western Boundary Current at 34.5° S. This current carries a large part of the cold deep limb of the Meridional Overturning Circulation, which is a crucial part of the ocean system and has impacts on global weather patterns. Study of this current in the South Atlantic has been limited in the past, and this new study provides insights into the strength and variability of the current as well as the causes for the observed changes. Read more
Soil conservation in the 21st century: why we need smart agricultural intensification SOIL DOI 10.5194/soil-3-45-2017 1 March 2017 We discuss pathways towards better soil protection in the 21st century. The efficacy of soil conservation technology is not a fundamental barrier for a more sustainable soil management. However, soil conservation is generally not directly beneficial to the farmer. We believe that the solution of this conundrum is a rapid, smart intensification of agriculture in the Global South. This will reduce the financial burden and will, at the same time, allow more effective conservation. Read more
A record of Neogene seawater δ11B reconstructed from paired δ11B analyses on benthic and planktic foraminifera Climate of the Past DOI 10.5194/cp-13-149-2017 24 February 2017 Understanding the boron isotopic composition of seawater (δ11Bsw) is key to calculating absolute estimates of CO2 using the boron isotope pH proxy. Here we use the boron isotope gradient, along with an estimate of pH gradient, between the surface and deep ocean to show that the δ11Bsw varies by ~ 2 ‰ over the past 23 million years. This new record has implications for both δ11Bsw and CO2 records and understanding changes in the ocean isotope composition of a number of ions through time. Read more
Multi-model simulations of aerosol and ozone radiative forcing due to anthropogenic emission changes during the period 1990–2015 Atmospheric Chemistry and Physics DOI 10.5194/acp-17-2709-2017 22 February 2017 Over the past decades, the geographical distribution of emissions of substances that alter the atmospheric energy balance has changed due to economic growth and pollution regulations. Here, we show the resulting changes to aerosol and ozone abundances and their radiative forcing using recently updated emission data for the period 1990–2015, as simulated by seven global atmospheric composition models. The global mean radiative forcing is more strongly positive than reported in IPCC AR5. Read more
A new device to mount portable energy-dispersive X-ray fluorescence spectrometers (p-ED-XRF) for semi-continuous analyses of split (sediment) cores and solid samples Geoscientific Instrumentation, Methods and Data Systems DOI 10.5194/gi-6-93-2017 17 February 2017 This paper introduces a hands-on, low-cost device (German industrial property right no. 20 2014 106 048.0) that uses common adapters to mount p-ED-XRF devices so that these can provide bulk-sedimentary chemistry data from non-destructive measurements at the surface of a split sediment core or from other solid samples. The strength of combining p-ED-XRF analyses with this new sample chamber is demonstrated by exemplary sediment cores from an archaeological research project. Read more
How much can we save? Impact of different emission scenarios on future snow cover in the Alps The Cryosphere DOI 10.5194/tc-11-517-2017 16 February 2017 We simulate the future snow cover in the Alps with the help of a snow model, which is fed by projected temperature and precipitation changes from a large set of climate models. The results demonstrate that snow below 1000 m is probably a rare guest at the end of the century. Moreover, even above 3000 m the simulations show a drastic decrease in snow depth. However, the results reveal that the projected snow cover reduction can be mitigated by 50 % if we manage to keep global warming below 2°. Read more
Brief communication: Glaciers in the Hunza catchment (Karakoram) have been nearly in balance since the 1970s The Cryosphere DOI 10.5194/tc-11-531-2017 15 February 2017 Previous geodetic estimates of glacier mass changes in the Karakoram have revealed balanced budgets or a possible slight mass gain since the year ∼ 2000. We used old US reconnaissance imagery and could show that glaciers in the Hunza River basin (Central Karakoram) experienced on average no significant mass changes also since the 1970s. Likewise the glaciers had heterogeneous behaviour with frequent surge activities during the last 40 years. Read more
Trend of atmospheric mercury concentrations at Cape Point for 1995–2004 and since 2007 Atmospheric Chemistry and Physics DOI 10.5194/acp-17-2393-2017 15 February 2017 Currently the Cape Point GAW GEM record is a very sought-after data record for international modelers and scientist alike, as the data set of 20 years represents the longest record in the Southern Hemisphere (SH). CPT was the only monitoring site on the African continent and one of eight GMOS ground-based monitoring sites located in the SH. The increasing Hg trend observed at CPT is of global importance as treaties such as the Minamata Convention on Mercury is there to combat Hg pollution. Read more
Rapid attribution of the August 2016 flood-inducing extreme precipitation in south Louisiana to climate change Hydrology and Earth System Sciences DOI 10.5194/hess-21-897-2017 14 February 2017 During August 2016, heavy precipitation led to devastating floods in south Louisiana, USA. Here, we analyze the climatological statistics of the precipitation event, as defined by its 3-day total over 12–14 August. Using observational data and high-resolution global coupled model experiments, we find for a comparable event on the central US Gulf Coast an average return period of about 30 years and the odds being increased by at least 1.4 since 1900 due to anthropogenic climate change. Read more
Global scale variability of the mineral dust long-wave refractive index: a new dataset of in situ measurements for climate modeling and remote sensing Atmospheric Chemistry and Physics DOI 10.5194/acp-17-1901-2017 9 February 2017 Modeling the interaction of dust with long-wave (LW) radiation is still a challenge due to the scarcity of information on their refractive index. In this paper, we present a unique dataset of dust refractive indices obtained from in situ measurements in a large smog chamber. Our results show that the dust LW refractive index varies strongly from source to source due to particle composition changes. We recommend taking this variability into account in climate and remote sensing applications. Read more
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
A comprehensive one-dimensional numerical model for solute transport in rivers Hydrology and Earth System Sciences DOI 10.5194/hess-21-99-2017 5 January 2017 In this study a comprehensive model was developed that combines numerical schemes with high-order accuracy for solution of the advection–dispersion equation considering transient storage zones term in rivers. In developing the subjected model (TOASTS), for achieving better accuracy and applicability, irregular-cross sections and unsteady flow regime were considered. For this purpose the QUICK scheme due to its high stability and low approximation error has been used for spatial discretization. Read more
A missing source of aerosols in Antarctica – beyond long-range transport, phytoplankton, and photochemistry Atmospheric Chemistry and Physics DOI 10.5194/acp-17-1-2017 2 January 2017 This paper summarizes two field measurements of particles and gases made in coastal Antarctica and represents the first real-time composition measurements of particles in this understudied area of the world. Using the combined data from both field measurements, we find that there is a constant background of particles in coastal Antarctica and that they are mostly sulfate. Seasonal transitions from winter to spring add additional particles, and that from spring to summer adds additional sulfate. Read more
Model sensitivity studies of the decrease in atmospheric carbon tetrachloride Atmospheric Chemistry and Physics DOI 10.5194/acp-16-15741-2016 20 December 2016 Carbon tetrachloride (CCl4) is a compound which, when released into the atmosphere, can cause depletion of the stratospheric ozone layer. Its emissions are controlled under the Montreal Protocol, and its atmospheric abundance is slowly decreasing. However, this decrease is not as fast as expected based on estimates of its emissions and its atmospheric lifetime. We have used an atmospheric model to look at the uncertainties in the CCl4lifetime and to examine the impact on its atmospheric decay. Read more
Slow strain waves in blocky geological media from GPS and seismological observations on the Amurian plate Nonlinear Processes in Geophysics DOI 10.5194/npg-23-467-2016 19 December 2016 We have obtained new evidence of the existence of strain waves in the Earth based on a statistical analysis of the dynamics of seismicity along the northern boundary of the Amurian plate and the data derived from in situ GPS experimental observations. Our results (the periodicity of the seismic components, spatial cycles of the seismicity maxima and migration rate of earthquakes) allow us to identify the dynamics of seismicity along the northern boundary of the Amurian plate as a wave process. Read more
Non-destructive evaluation of moisture content in wood using ground-penetrating radar Geoscientific Instrumentation, Methods and Data Systems DOI 10.5194/gi-5-575-2016 16 December 2016 Ground-penetrating radar (GPR) is a powerful tool that uses electromagnetic waves to obtain 3-dimensional images of natural or man-made structures and subsoil. It is employed in a large variety of applications in which non-destructive investigations are required. This paper deals with the use of GPR for the evaluation of moisture content in wood. The results of our work are of great interest for the preservation of timber structures, as moisture content is highly relevant to wood deterioration. Read more
Last Interglacial climate and sea-level evolution from a coupled ice sheet–climate model Climate of the Past DOI 10.5194/cp-12-2195-2016 15 December 2016 We simulate the climate, ice sheet, and sea-level evolution during the Last Interglacial (~ 130 to 115 kyr BP), the most recent warm period in Earth’s history. Our Earth system model includes components representing the atmosphere, the ocean and sea ice, the terrestrial biosphere, and the Greenland and Antarctic ice sheets. Our simulation is in good agreement with available data reconstructions and gives important insights into the dominant mechanisms that caused ice sheet changes in the past. Read more
Graffiti for science – erosion painting reveals spatially variable erosivity of sediment-laden flows Earth Surface Dynamics DOI 10.5194/esurf-4-885-2016 15 December 2016 Spatial bedrock erosion data from stream channels are important for engineering issues and landscape evolution model assessment. However, acquiring such data is challenging and only few data sets exist. Detecting changes in repeated photographs of painted bedrock surfaces easily allows for semi-quantitative conclusions on the spatial distribution of sediment transport and its effects: abrasion on surfaces facing the streamflow and shielding of surfaces by abundant sediment. Read more
North American regional climate reconstruction from ground surface temperature histories Climate of the Past DOI 10.5194/cp-12-2181-2016 14 December 2016 Within the framework of the PAGES NAm2k project, we estimated regional trends in the ground surface temperature change for the past 500 years in North America. The mean North American ground surface temperature history suggests a warming of 1.8 °C between preindustrial times and 2000. A regional analysis of mean temperature changes over the last 5 centuries shows that all regions experienced warming, but this warming displays large spatial variability and is more marked in high-latitude regions. Read more
The acid-catalyzed hydrolysis of an α-pinene-derived organic nitrate: kinetics, products, reaction mechanisms, and atmospheric impact Atmospheric Chemistry and Physics DOI 10.5194/acp-16-15425-2016 13 December 2016 This study provides new insight into the hydrolysis reaction mechanism, which was elucidated for atmospherically relevant organic nitrates using kinetic measurements, product identification, and theoretical calculations. The results help broaden our knowledge of the organic chemistry that impacts the fate of NOx, ozone production, aerosol phase processing, and aerosol composition. Read more
Use of remote-sensing reflectance to constrain a data assimilating marine biogeochemical model of the Great Barrier Reef Biogeosciences DOI 10.5194/bg-13-6441-2016 7 December 2016 Marine biogeochemical models are often used to understand water quality, nutrient and blue-carbon dynamics at scales that range from estuaries and bays, through to the global ocean. We introduce a new methodology allowing for the assimilation of observed remote sensing reflectances, avoiding the need to use empirically derived chlorophyll-a concentrations. This method opens up the possibility to assimilate of reflectances from a variety of missions and potentially non-satellite platforms. Read more
Significant concentrations of nitryl chloride sustained in the morning: investigations of the causes and impacts on ozone production in a polluted region of northern China Atmospheric Chemistry and Physics DOI 10.5194/acp-16-14959-2016 5 December 2016 This work addresses the unclear global significance of chlorine activation processes in the troposphere. The first high-quality measurement data set of ClNO2in northern China revealed strong ClNO2 production in the residual layers, and demonstrated its significant effects on radical budget and ozone production. Our findings imply the widespread effects of ClNO2 over the polluted regions of northern China, which may increase photochemical and haze pollution. Read more
The 1430s: a cold period of extraordinary internal climate variability during the early Spörer Minimum with social and economic impacts in north-western and central Europe Climate of the Past DOI 10.5194/cp-12-2107-2016 1 December 2016 Throughout the last millennium, several cold periods occurred which affected humanity. Here, we investigate an exceptionally cold decade during the 15th century. The cold conditions challenged the food production and led to increasing food prices and a famine in parts of Europe. In contrast to periods such as the “Year Without Summer” after the eruption of Tambora, these extreme climatic conditions seem to have occurred by chance and in relation to the internal variability of the climate system. Read more
Linking hydraulic traits to tropical forest function in a size-structured and trait-driven model (TFS v.1-Hydro) Geoscientific Model Development DOI 10.5194/gmd-9-4227-2016 24 November 2016 We developed a plant hydraulics model for tropical forests based on established plant physiological theory, and parameterized it by conducting a pantropical hydraulic trait survey. We show that a substantial amount of trait diversity can be represented in the model by a reduced set of trait dimensions. The fully parameterized model is able capture tree-level variation in water status and improves simulations of total ecosystem transpiration, showing how to incorporate hydraulic traits in models. Read more
Multi-annual modes in the 20th century temperature variability in reanalyses and CMIP5 models Geoscientific Model Development DOI 10.5194/gmd-9-4097-2016 17 November 2016 This study compares the 20th century multi-annual climate variability modes in reanalysis data sets (ERA-20C and 20CR) and 12 climate model simulations using the randomised multi-channel singular spectrum analysis. The reanalysis data sets are remarkably similar on all timescales, except that the spectral power in ERA-20C is systematically slightly higher than in 20CR. None of the climate models closely reproduce all aspects of the reanalysis spectra, although many aspects are represented well. Read more
Quantifying the loss of processed natural gas within California’s South Coast Air Basin using long-term measurements of ethane and methane Atmospheric Chemistry and Physics DOI 10.5194/acp-16-14091-2016 15 November 2016 This paper investigates the cause of the known underestimate of bottom-up inventories of methane in California’s South Coast Air Basin (SoCAB). We use total column measurements of methane, ethane, carbon monoxide, and other trace gases beginning in the late 1980s to calculate emissions and attribute sources of excess methane to the atmosphere. We conclude that more than half of the excess methane to the SoCAB atmosphere is attributable to processed natural gas. Read more
Refinement of the ice absorption spectrum in the visible using radiance profile measurements in Antarctic snow The Cryosphere DOI 10.5194/tc-10-2655-2016 14 November 2016 The absorption of visible light in ice is very weak but its precise value is unknown. By measuring the profile of light intensity in snow, Warren and Brand (2006) deduced that light is attenuated by a factor 2 per kilometer in pure ice at a wavelength of 400 nm. We replicated their experiment on a large number of samples and found that ice absorption is at least 10 times stronger. The paper explores various potential physical and statistical biases that could impact the experiment. Read more
Accounting for model error in air quality forecasts: an application of 4DEnVar to the assimilation of atmospheric composition using QG-Chem 1.0 Geoscientific Model Development DOI 10.5194/gmd-9-3933-2016 8 November 2016 This paper analyses methods to assimilate chemical measurements in air quality models. We developed a reduced-order atmospheric chemistry model, which was used to compare results from different assimilation algorithms. Using an ensemble variational method (4DEnVar), we exploited the dynamical information provided by hourly measurements of chemical concentrations to diagnose model biases and improve next-day forecasts for several species of interest for air quality. Read more
Brief communication: Impacts of a developing polynya off Commonwealth Bay, East Antarctica, triggered by grounding of iceberg B09B The Cryosphere DOI 10.5194/tc-10-2603-2016 4 November 2016 Here we report new data from in situ oceanographic surveys and high-resolution ocean modelling experiments in the Commonwealth Bay region of East Antarctica, where in 2010 there was a major reconfiguration of the regional icescape due to the collision of the 97 km long iceberg B09B with the Mertz Glacier tongue. Here we compare post-calving observations with high-resolution ocean modelling which suggest that this reconfiguration has led to the development of a new polynya off Commonwealth Bay. Read more
Effects of ocean acidification on pelagic carbon fluxes in a mesocosm experiment Biogeosciences DOI 10.5194/bg-13-6081-2016 4 November 2016 We performed an experiment in the Baltic Sea in order to investigate the consequences of the increasing CO2levels on biological processes in the free water mass. There was more accumulation of organic carbon at high CO2levels. Surprisingly, this was caused by reduced loss processes (respiration and bacterial production) in a high-CO2environment, and not by increased photosynthetic fixation of CO2. Our carbon budget can be used to better disentangle the effects of ocean acidification. Read more
Seasonal evolution of the effective thermal conductivity of the snow and the soil in high Arctic herb tundra at Bylot Island, Canada The Cryosphere DOI 10.5194/tc-10-2573-2016 2 November 2016 The thermal conductivity (TC) of the snow and top soil greatly impacts the permafrost energy budget. We report the first winter-long monitoring of snow and soil TC in the high Arctic. The data and field observations show the formation of a highly insulating basal depth hoar layer overlaid by a more conductive wind slab. Detailed snow physics models developed for alpine snow cannot reproduce observations because they neglect the strong upward vertical water vapor flux prevailing in Arctic snow. Read more