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
Dominant process zones in a mixed fluvial–tidal delta are morphologically distinct Earth Surface Dynamics DOI 10.5194/esurf-8-809-2020 29 October 2020 We propose a machine learning approach for the classification and analysis of large delta systems. The approach uses remotely sensed data, channel network extraction, and the analysis of 10 metrics to identify clusters of islands with similar characteristics. The 12 clusters are grouped in six main classes related to morphological processes acting on the system. The approach allows us to identify spatial patterns in large river deltas to inform modeling and the collection of field observations. Read more
Timing of exotic, far-traveled boulder emplacement and paleo-outburstflooding in the central Himalayas Earth Surface Dynamics DOI 10.5194/esurf-8-769-2020 27 October 2020 Large boulders found in two Himalayan valleys show signs of long fluvial transport (>10 km). Paleo-discharges required to mobilize these boulders exceed typical monsoon discharges. Exposure dating shows that a cluster of these boulders was emplaced ca. 5 kyr ago. This period is coeval with a weakening of the Indian monsoon and glacier retreat in the area. We, therefore, suggest that glacier lake outburst floods are likely mechanisms that can explain these exceptional transport processes. Read more