River logjams cause frequent large-scale forest die-off events in southwestern Amazonia Earth System Dynamics DOI 10.5194/esd-8-565-2017 11 July 2017 In lowland Bolivia, satellite images show rivers collapsing and the replacement of forest with savannah. This was first described in 1996 as the result of logjams (river dams created by fallen trees). I have investigated how the logjams form and affect the forest through remote sensing and fieldwork. Logjams occur nearly every year and propagate upriver until the river changes course. This region offers a unique opportunity to study how frequent forest die-off events affect biodiversity. Read more
Detectability of Arctic methane sources at six sites performing continuous atmospheric measurements Atmospheric Chemistry and Physics DOI 10.5194/acp-17-8371-2017 11 July 2017 Atmospheric methane simulations in the Arctic have been made for 2012 and compared to continuous observations at six measurement sites. All methane sources significantly affect the measurements at all stations, at least at the synoptic scale, except for biomass burning. An appropriate modelling framework combined with continuous observations of atmospheric methane enables us to gain knowledge on regional methane sources, including those which are usually poorly represented, such as freshwater. Read more
Geomorphometric delineation of floodplains and terraces from objectively defined topographic thresholds Earth Surface Dynamics DOI 10.5194/esurf-5-369-2017 10 July 2017 Floodplains and fluvial terraces can provide information about current and past river systems, helping to reveal how channels respond to changes in both climate and tectonics. We present a new method of identifying these features objectively from digital elevation models by analysing their slope and elevation compared to the modern river. We test our method in eight field sites, and find that it provides rapid and reliable extraction of floodplains and terraces across a range of landscapes. Read more
A weekly Arctic sea-ice thickness data record from merged CryoSat-2 and SMOS satellite data The Cryosphere DOI 10.5194/tc-11-1607-2017 6 July 2017 We developed the first merging of CryoSat-2 and SMOS sea-ice thickness retrievals. ESA’s Earth Explorer SMOS satellite can detect thin sea ice, whereas its companion CryoSat-2, designed to observe thicker perennial sea ice, lacks sensitivity. Using these satellite missions together completes the picture of the changing Arctic sea ice and provides a more accurate and comprehensive view on the actual state of Arctic sea-ice thickness. SMOS satellite data">Read more
Non-linear intensification of Sahel rainfall as a possible dynamic response to future warming Earth System Dynamics DOI 10.5194/esd-8-495-2017 5 July 2017 Monsoon systems have undergone abrupt changes in past climates, and theoretical considerations show that threshold behavior can follow from the internal dynamics of monsoons. So far, however, the possibility of abrupt changes has not been explored for modern monsoon systems. We analyze state-of-the-art climate model simulations and show that some models project abrupt changes in Sahel rainfall in response to a dynamic shift in the West African monsoon under 21st century climate change. Read more
WCRP’s Coupled Model Intercomparison Project: a remarkable contribution to climate science Geoscientific Model Development DOI 10.5194/gmd-9-1937-2016 4 July 2017 As part of the Coupled Model Intercomparison Project (CMIP) organized under the auspices of the World Climate Research Programme’s (WCRP) Working Group on Coupled Modelling (WGCM) many hundreds of climate researchers, working with modeling centres around the world, will share, compare and analyze the latest outcomes of global climate models. These model products will fuel climate research for the next 5 to 10 years, while its careful analysis will form the basis for future climate assessments and negotiations. Read more
The importance of terrestrial weathering changes in multimillennial recovery of the global carbon cycle: a two-dimensional perspective Earth System Dynamics DOI 10.5194/esd-8-455-2017 30 June 2017 In this paper we describe the development and application of a new spatially explicit weathering scheme within the University of Victoria Earth System Climate Model (UVic ESCM). We integrated a dataset of modern-day lithology with a number of previously devised parameterizations for weathering dependency on temperature, primary productivity, and runoff. We tested the model with simulations of future carbon cycle perturbations and confirmed the importance of silicate weathering in the long term. Read more
Opposite long-term trends in aerosols between low and high altitudes: a testimony to the aerosol–PBL feedback Atmospheric Chemistry and Physics DOI 10.5194/acp-17-7997-2017 30 June 2017 Opposite trends in aerosol loading between the lower and upper planetary boundary layer are found on a wide range of timescales and from different types of data acquired by various platforms in China. The reversal trend is consistent with the strong vertical gradients in the aerosol-induced atmospheric heating rate that unevenly modifies the atmospheric temperature profile and alters the stability differently. The findings have multiple implications in understanding and combating air pollution. Read more
STRAPS v1.0: evaluating a methodology for predicting electron impact ionisation mass spectra for the aerosol mass spectrometer Geoscientific Model Development DOI 10.5194/gmd-10-2365-2017 27 June 2017 Our ability to model the chemical and thermodynamic processes that lead to secondary organic aerosol (SOA) formation is thought to be hampered by the complexity of the system. In this proof of concept study, the ability to train supervised methods to predict electron impact ionisation (EI) mass spectra for the AMS is evaluated to facilitate improved model evaluation. The study demonstrates the use of a methodology that would be improved with more training data and data from simple mixed systems. STRAPS v1.0: evaluating a methodology for predicting electron impact ionisation mass spectra for the aerosol mass spectrometer">Read more
Statistical characteristics of convective wind gusts in Germany Natural Hazards and Earth System Sciences DOI 10.5194/nhess-17-957-2017 23 June 2017 Due to the small-scale and non-stationary nature of the convective wind gusts usually associated with thunderstorms, there is a considerable lack of knowledge regarding their characteristics and statistics. Thus, we investigated the temporal and spatial distribution, intensity, and return values of those wind events in Germany. The study constitutes a fundamental addition to an improved understanding of convective wind gusts and serves as basis for further risk assessments. Read more
