Lower-thermosphere response to solar activity: an empirical-mode-decomposition analysis of GOCE 2009–2012 data Annales Geophysicae DOI 10.5194/angeo-38-789-2020 9 July 2020 Forecasting the thermosphere (atmosphere’s uppermost layer from 90 to 800 km altitude) is crucial to space mission design, spacecraft operations and space surveillance. The thermosphere is controlled by the Sun through variable solar extreme-ultraviolet radiation and the solar wind. We show how the solar indices Mg II and Ap may be used in forecasting thermospheric density at 260 km, a very low altitude, where the GOCE satellite operated from 2009 to 2013, during the full rise of solar cycle 24. Read more
Identifying a regional aerosol baseline in the eastern North Atlantic using collocated measurements and a mathematical algorithm to mask high-submicron-number-concentration aerosol events Atmospheric Chemistry and Physics DOI 10.5194/acp-20-7553-2020 9 July 2020 Continuous high-time-resolution ambient data can include periods when aerosol properties do not represent regional aerosol processes due to high-concentration local events. We develop a novel aerosol mask at the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) facility in the eastern North Atlantic (ENA). We use two ground sites to validate the mask, include a comparison with aircraft overflights, and provide guidance to increase data quality at ENA and other locations. Read more
The contribution of microbial communities in polymetallic nodules to thediversity of the deep-sea microbiome of the Peru Basin (4130–4198 mdepth) Biogeosciences DOI 10.5194/bg-17-3203-2020 7 July 2020 Industrial-scale mining of deep-sea polymetallic nodules will remove nodules in large areas of the sea floor. We describe community composition of microbes associated with nodules of the Peru Basin. Our results show that nodules provide a unique ecological niche, playing an important role in shaping the diversity of the benthic deep-sea microbiome and potentially in element fluxes. We believe that our findings are highly relevant to expanding our knowledge of the impact associated with mining. Read more
Enhanced growth rate of atmospheric particles from sulfuric acid Atmospheric Chemistry and Physics DOI 10.5194/acp-20-7359-2020 7 July 2020 Sulfuric acid is a major atmospheric vapour for aerosol formation. If new particles grow fast enough, they can act as cloud droplet seeds or affect air quality. In a controlled laboratory set-up, we demonstrate that van der Waals forces enhance growth from sulfuric acid. We disentangle the effects of ammonia, ions and particle hydration, presenting a complete picture of sulfuric acid growth from molecular clusters onwards. In a climate model, we show its influence on the global aerosol budget. Read more
The role of prior assumptions in carbon budget calculations Earth System Dynamics DOI 10.5194/esd-11-563-2020 2 July 2020 Levels of future temperature change are often used interchangeably with carbon budget allowances in climate policy, a relatively robust relationship on the timescale of this century. However, recent advances in understanding underline that continued warming after net-zero emissions have been achieved cannot be ruled out by observations of warming to date. We consider here how such behavior could be constrained and how policy can be framed in the context of these uncertainties. Read more
Snow avalanche detection and mapping in multitemporal and multiorbital radar images from TerraSAR-X and Sentinel-1 Natural Hazards and Earth System Sciences DOI 10.5194/nhess-20-1783-2020 2 July 2020 To assess snow avalanche mapping with radar satellites in Switzerland, we compare 2 m resolution TerraSAR-X images, 10 m resolution Sentinel-1 images, and optical 1.5 m resolution SPOT-6 images. We found that radar satellites provide a valuable option to map at least larger avalanches, though avalanches are mapped only partially. By combining multiple orbits and polarizations from S1, we achieved mapping results of quality almost comparable to single high-resolution TerraSAR-X images. Read more
Towards an objective assessment of climate multi-model ensembles – a casestudy: the Senegalo-Mauritanian upwelling region Geoscientific Model Development DOI 10.5194/gmd-13-2723-2020 30 June 2020 The most robust representation of climate is usually obtained by averaging a large number of simulations, thereby cancelling individual model errors. Here, we work towards an objective way of selecting the least biased models over a certain region, based on physical parameters. This statistical method based on a neural classifier and multi-correspondence analysis is illustrated here for the Senegalo-Mauritanian region, but it could potentially be developed for any other region or process. Read more
Modelling the potential impacts of the recent, unexpected increase in CFC-11 emissions on total column ozone recovery Atmospheric Chemistry and Physics DOI 10.5194/acp-20-7153-2020 30 June 2020 The Montreal Protocol was agreed in 1987 to limit and then stop the production of man-made CFCs, which destroy stratospheric ozone. As a result, the atmospheric abundances of CFCs are now declining in the atmosphere. However, the atmospheric abundance of CFC-11 is not declining as expected under complete compliance with the Montreal Protocol. Using the UM-UKCA chemistry–climate model, we explore the impact of future unregulated production of CFC-11 on ozone recovery. Read more
Changes of the Arctic marginal ice zone during the satellite era The Cryosphere DOI 10.5194/tc-14-1971-2020 25 June 2020 It is well known that the Arctic sea ice extent is declining, and it is often assumed that the marginal ice zone (MIZ), the area of partial sea ice cover, is consequently increasing. However, we find no trend in the MIZ extent during the last 40 years from observations that is consistent with a widening of the MIZ as it moves northward. Differences of MIZ extent between different satellite retrievals are too large to provide a robust basis to verify model simulations of MIZ extent. Read more
Is there warming in the pipeline? A multi-model analysis of the Zero Emissions Commitment from CO2 Biogeosciences DOI 10.5194/bg-17-2987-2020 25 June 2020 The Zero Emissions Commitment (ZEC) is the change in global temperature expected to occur following the complete cessation of CO 2 emissions. Here we use 18 climate models to assess the value of ZEC. For our experiment we find that ZEC 50 years after emissions cease is between −0.36 to +0.29 °C. The most likely value of ZEC is assessed to be close to zero. However, substantial continued warming for decades or centuries following cessation of CO 2 emission cannot be ruled out. Read more
