Evaluation of ocean dimethylsulfide concentration and emission in CMIP6 models Biogeosciences DOI 10.5194/bg-18-3823-2021 4 August 2021 In this study we analyse surface ocean dimethylsulfide (DMS) concentration and flux to the atmosphere from four CMIP6 Earth system models over the historical and ssp585 simulations. Our analysis of contemporary (1980–2009) climatologies shows that models better reproduce observations in mid to high latitudes. The models disagree on the sign of the trend of the global DMS flux from 1980 onwards. The models agree on a positive trend of DMS over polar latitudes following sea-ice retreat dynamics. Read more
Committed and projected future changes in global peatlands – continued transient model simulations since the Last Glacial Maximum Biogeosciences DOI 10.5194/bg-18-3657-2021 2 August 2021 We present long-term projections of global peatland area and carbon with a continuous transient history since the Last Glacial Maximum. Our novel results show that large parts of today’s northern peatlands are at risk from past and future climate change, with larger emissions clearly connected to larger risks. The study includes comparisons between different emission and land-use scenarios, driver attribution through factorial simulations, and assessments of uncertainty from climate forcing. Read more
Rarefied particle motions on hillslopes – Part 1: Theory Earth Surface Dynamics DOI 10.5194/esurf-9-539-2021 30 July 2021 Sediment particles skitter down steep hillslopes on Earth and Mars. Particles gain speed in going downhill but are slowed down and sometimes stop due to collisions with the rough surface. The likelihood of stopping depends on the energetics of speeding up (heating) versus slowing down (cooling). Statistical physics predicts that particle travel distances are described by a generalized Pareto distribution whose form varies with the Kirkby number – the ratio of heating to cooling. Read more
SoilGrids 2.0: producing soil information for the globe with quantified spatial uncertainty SOIL DOI 10.5194/soil-7-217-2021 28 July 2021 This paper focuses on the production of global maps of soil properties with quantified spatial uncertainty, as implemented in the SoilGrids version 2.0 product using DSM practices and adapting them for global digital soil mapping with legacy data. The quantitative evaluation showed metrics in line with previous studies. The qualitative evaluation showed that coarse-scale patterns are well reproduced. The spatial uncertainty at global scale highlighted the need for more soil observations. Read more
Mapping the aerodynamic roughness of the Greenland Ice Sheet surface using ICESat-2: evaluation over the K-transect The Cryosphere DOI 10.5194/tc-15-2601-2021 26 July 2021 We developed a method to estimate the aerodynamic properties of the Greenland Ice Sheet surface using either UAV or ICESat-2 elevation data. We show that this new method is able to reproduce the important spatiotemporal variability in surface aerodynamic roughness, measured by the field observations. The new maps of surface roughness can be used in atmospheric models to improve simulations of surface turbulent heat fluxes and therefore surface energy and mass balance over rough ice worldwide. ICESat-2: evaluation over the K-transect">Read more
A discontinuous Galerkin finite-element model for fast channelized lava flows v1.0 Geoscientific Model Development DOI 10.5194/gmd-14-3553-2021 23 July 2021 Lava flows present a natural hazard to communities around volcanoes and are usually slow-moving (< 1-5 cm/s). Lava flows during the 2018 eruption of Kilauea volcano, Hawai’i, however, reached speeds as high as 11 m/s. To investigate these dynamics we develop a new lava flow computer model that incorporates a nonlinear expression for the fluid viscosity. Model results indicate that the lava flows at Site 8 of the eruption displayed shear thickening behavior due to the flow’s high bubble content. Read more
Fracking bad language – hydraulic fracturing and earthquake risks Geoscience Communication DOI 10.5194/gc-4-303-2021 21 July 2021 The potential for hydraulic fracturing (fracking) to induce seismicity is a topic of widespread interest. We find that terms used to describe induced seismicity are poorly defined and ambiguous and do not translate into everyday language. Such bad language has led to challenges in understanding, perceiving, and communicating risks around seismicity and fracking. Our findings and recommendations are relevant to other geoenergy topics that are potentially associated with induced seismicity. Read more
Microbial and geo-archaeological records reveal the growth rate, origin and composition of desert rock surface communities Biogeosciences DOI 10.5194/bg-18-3331-2021 19 July 2021 Biological rock crusts (BRCs) are common microbial-based assemblages covering rocks in drylands. BRCs play a crucial role in arid environments because of the limited activity of plants and soil. Nevertheless, BRC development rates have never been dated. Here we integrated archaeological, microbiological and geological methods to provide a first estimation of the growth rate of BRCs under natural conditions. This can serve as an affordable dating tool in archaeological sites in arid regions. Read more
Faster decline and higher variability in the sea ice thickness of the marginal Arctic seas when accounting for dynamic snow cover The Cryosphere DOI 10.5194/tc-15-2429-2021 16 July 2021 We re-estimate pan-Arctic sea ice thickness (SIT) values by combining data from the Envisat and CryoSat-2 missions with data from a new, reanalysis-driven snow model. Because a decreasing amount of ice is being hidden below the waterline by the weight of overlying snow, we argue that SIT may be declining faster than previously calculated in some regions. Because the snow product varies from year to year, our new SIT calculations also display much more year-to-year variability. Read more
Oxygen isotope exchange between water and carbon dioxide in soils is controlled by pH, nitrate and microbial biomass through links to carbonic anhydrase activity SOIL DOI 10.5194/soil-7-145-2021 14 July 2021 Understanding how the rate of oxygen isotope exchange between water and CO2 varies in soils is key for using the oxygen isotope composition of atmospheric CO2 as a tracer of biosphere CO2 fluxes at large scales. Across 44 diverse soils the rate of this exchange responded to pH, nitrate and microbial biomass, which are hypothesised to alter activity of the enzyme carbonic anhydrase in soils. Using these three soil traits, it is now possible to predict how this isotopic exchange varies spatially. Read more
