Resolving multiple geological events using in situ Rb–Sr geochronology:implications for metallogenesis at Tropicana, Western Australia Geochronology DOI 10.5194/gchron-2-283-2020 17 November 2020 Using a relatively new dating technique, in situ Rb–Sr geochronology, we constrain the ages of two generations of mineral assemblages from the Tropicana Zone, Western Australia. The first, dated at ca. 2535 Ma, is associated with exhumation of an Archean craton margin and gold mineralization. The second, dated at ca. 1210 Ma, has not been previously documented in the Tropicana Zone. It is probably associated with Stage II of the Albany–Fraser Orogeny and additional gold mineralization. Read more
A feasibility study to use machine learning as an inversion algorithm for aerosol profile and property retrieval from multi-axis differentialabsorption spectroscopy measurements Atmospheric Measurement Techniques DOI 10.5194/amt-13-5537-2020 12 November 2020 This paper is about a feasibility study of applying a machine learning technique to derive aerosol properties from a single MAX-DOAS sky scan, which detects sky-scattered UV–visible photons at multiple elevation angles. Evaluation of retrieved aerosol properties shows good performance of the ML algorithm, suggesting several advantages of a ML-based inversion algorithm such as fast data inversion, simple implementation and the ability to extract information not available using other algorithms. Read more
Connecting flow–topography interactions, vorticity balance, baroclinicinstability and transport in the Southern Ocean: the case of an idealizedstorm track Ocean Science DOI 10.5194/os-16-1207-2020 12 November 2020 The dynamical balance of the Antarctic Circumpolar Current and its implications on the functioning of the world ocean are not fully understood and poorly represented in global circulation models. In this study, the sensitivities of an idealized Southern Ocean (SO) storm track are explored with a set of eddy-rich numerical simulations. We show that the classical partition between barotropic and baroclinic modes is sensitive to current–topography interactions in the mesoscale range of 10–100 km. Read more
Ionic aluminium concentrations exceed thresholds for aquatic health in Nova Scotian rivers, even during conditions of high dissolved organic carbon and low flow Hydrology and Earth System Sciences DOI 10.5194/hess-24-4763-2020 10 November 2020 Wild salmon numbers in Nova Scotia, Canada, have been plummeting in recent decades. In 2014, we launched an ionic aluminium monitoring program in Nova Scotia to see if this toxic element was a threat to salmon populations. We found that all 10 monitored rivers had ionic aluminium concentrations that exceeded the threshold for aquatic health. Our results demonstrate that elevated aluminium still threatens aquatic ecosystems and that delays in recovery from acid rain remains a critical issue. Read more
Factors controlling plankton community production, export flux, and particulate matter stoichiometry in the coastal upwelling system off Peru Biogeosciences DOI 10.5194/bg-17-4831-2020 10 November 2020 The eastern boundary upwelling system off Peru is among Earth’s most productive ocean ecosystems, but the factors that control its functioning are poorly constrained. Here we used mesocosms, moored ~ 6 km offshore Peru, to investigate how processes in plankton communities drive key biogeochemical processes. We show that nutrient and light co-limitation keep productivity and export at a remarkably constant level while stoichiometry changes strongly with shifts in plankton community structure. Read more
Hydrology and water resources management in ancient India Hydrology and Earth System Sciences DOI 10.5194/hess-24-4691-2020 5 November 2020 Like in all ancient civilisations, the need to manage water propelled the growth of hydrological science in ancient India also. In this paper, we provide some fascinating glimpses into the hydrological, hydraulic, and related engineering knowledge that existed in ancient India, as discussed in contemporary literature and recent explorations and findings. Many interesting dimensions of early scientific endeavours emerge as we investigate deeper into ancient texts, including Indian mythology. Read more
Impacts of future land use and land cover change on mid-21st-century surface ozone air quality: distinguishing between the biogeophysical and biogeochemical effects Atmospheric Chemistry and Physics DOI 10.5194/acp-20-11349-2020 5 November 2020 We investigate the effects of future land use and land cover change (LULCC) on surface ozone air quality worldwide and find that LULCC can significantly influence ozone in North America and Europe via modifying surface energy balance, boundary-layer meteorology, and regional circulation. The strength of such “biogeophysical effects” of LULCC is strongly dependent on forest type and generally greater than the “biogeochemical effects” via changing deposition and emission fluxes alone. Read more
Impact of horizontal resolution on global ocean–sea ice model simulationsbased on the experimental protocols of the Ocean Model IntercomparisonProject phase 2 (OMIP-2) Geoscientific Model Development DOI 10.5194/gmd-13-4595-2020 3 November 2020 This paper presents global comparisons of fundamental global climate variables from a suite of four pairs of matched low- and high-resolution ocean and sea ice simulations to assess the robustness of climate-relevant improvements in ocean simulations associated with moving from coarse (∼1°) to eddy-resolving (∼0.1°) horizontal resolutions. Despite significant improvements, greatly enhanced horizontal resolution does not deliver unambiguous bias reduction in all regions for all models. Read more
Absorption closure in highly aged biomass burning smoke Atmospheric Chemistry and Physics DOI 10.5194/acp-20-11201-2020 3 November 2020 Every year, huge plumes of smoke hundreds of miles wide travel over the south Atlantic Ocean from fires in central and southern Africa. These plumes absorb the sun’s energy and warm the climate. We used airborne optical instrumentation to determine how absorbing the smoke was as well as the relative importance of black and brown carbon. We also tested different ways of simulating these properties that could be used in a climate model. Read more
Increase in ocean acidity variability and extremes under increasing atmospheric CO2 Biogeosciences DOI 10.5194/bg-17-4633-2020 29 October 2020 Ensemble simulations of an Earth system model reveal that ocean acidity extremes have increased in the past few decades and are projected to increase further in terms of frequency, intensity, duration, and volume extent. The increase is not only caused by the long-term ocean acidification due to the uptake of anthropogenic CO 2 , but also due to changes in short-term variability. The increase in ocean acidity extremes may enhance the risk of detrimental impacts on marine organisms. Read more