Interannual variability in contributions of the Equatorial Undercurrent (EUC) to Peruvian upwelling source water Ocean Science DOI 10.5194/os-17-1385-2021 8 December 2021 The Equatorial Undercurrent (EUC) is a key influence on upwelling of nutrient-rich waters associated ecosystems off Peru. To quantify this influence, we backtrack upwelling waters in a computer model of ocean currents, annually, over 1989–2007. The EUC influence varies from year to year, dominating in warm El Niño years, when the EUC extends much closer to the Peruvian coast. In other years, more “local” upwelling is associated with coastal winds, coincident with major key population shifts. Read more
An ensemble of state-of-the-art ash dispersion models: towards probabilistic forecasts to increase the resilience of air traffic against volcanic eruptions Natural Hazards and Earth System Sciences DOI 10.5194/nhess-21-2973-2021 6 December 2021 Past volcanic eruptions that spread out ash over large areas, like Eyjafjallajökull in 2010, forced the cancellation of thousands of flights and had huge economic consequences. In this article, an international team in the H2020 EU-funded EUNADICS-AV project has designed a probabilistic model approach to quantify ash concentrations. This approach is evaluated against measurements, and its potential use to mitigate the impact of future large-scale eruptions is discussed. Read more
Drifting dynamics of the bluebottle (Physalia physalis) Ocean Science DOI 10.5194/os-17-1341-2021 3 December 2021 The bluebottle (Physalia physalis), or Portuguese man o’ war, is well known for the painful stings caused by its tentacles. Its drifting dynamics have not been widely explored, with previous studies using simple assumptions to calculate its drift. Considering similarities with a sailboat, we present a new theoretical model for the drifting speed and course of the bluebottle in different wind and ocean conditions, providing new insights into the parameterization of its complex drifting dynamics. Read more
Sand mining far outpaces natural supply in a large alluvial river Earth Surface Dynamics DOI 10.5194/esurf-9-1323-2021 1 December 2021 Unsustainable sand mining poses a threat to the stability of river channels. We use satellite imagery to estimate volumes of material removed from the Mekong River, Cambodia, over the period 2016–2020. We demonstrate that current rates of extraction now exceed previous estimates for the entire Mekong Basin and significantly exceed the volume of sand naturally transported by the river. Our work highlights the importance of satellite imagery in monitoring sand mining activity over large areas. Read more
Dating folding beyond folding, from layer-parallel shortening to fold tightening, using mesostructures: lessons from the Apennines, Pyrenees, and Rocky Mountains Solid Earth DOI 10.5194/se-12-2145-2021 29 November 2021 This paper aims to illustrate how the timing and duration of contractional deformation associated with folding in orogenic forelands can be constrained by the dating of brittle mesostructures observed in folded strata. The study combines new and already published absolute ages of fractures to provide, for the first time, an educated discussion about the factors controlling the duration of the sequence of deformation encompassing layer-parallel shortening, fold growth, and late fold tightening. Read more
Escarpment retreat rates derived from detrital cosmogenic nuclide concentrations Earth Surface Dynamics DOI 10.5194/esurf-9-1301-2021 26 November 2021 Although great escarpment mountain ranges are characterized by high relief, modern erosion rates suggest slow rates of landscape change. We question this interpretation by presenting a new method for interpreting concentrations of cosmogenic isotopes. Our analysis shows that erosion has localized onto an escarpment face, driving retreat of the escarpment at high rates. Our quantification of this retreat rate rationalizes the high-relief, dramatic landscape with the rates of geomorphic change. Read more
A dynamically based method for estimating the Atlantic meridional overturning circulation at 26° N from satellite altimetry Ocean Science DOI 10.5194/os-17-1321-2021 24 November 2021 In the North Atlantic, ocean currents carry warm surface waters northward and return cooler deep waters southward. This type of ocean circulation, known as overturning, is important for the Earth’s climate. This overturning has been measured using a mooring array at 26° N in the North Atlantic since 2004. Here we use these mooring data and global satellite data to produce a new method for monitoring the overturning over longer timescales, which could potentially be applied to different latitudes. Read more
Persistent impacts of the 2018 drought on forest disturbance regimes in Europe Biogeosciences DOI 10.5194/bg-18-5223-2021 22 November 2021 Europe was affected by an extreme drought in 2018. We show that this drought has increased forest disturbances across Europe, especially central and eastern Europe. Disturbance levels observed 2018–2020 were the highest on record for 30 years. Increased forest disturbances were correlated with low moisture and high atmospheric water demand. The unprecedented impacts of the 2018 drought on forest disturbances demonstrate an urgent need to adapt Europe’s forests to a hotter and drier future. Read more
The driving factors of new particle formation and growth in the polluted boundary layer Atmospheric Chemistry and Physics DOI 10.5194/acp-21-14275-2021 19 November 2021 Experiments at CLOUD show that in polluted environments new particle formation (NPF) is largely driven by the formation of sulfuric acid–base clusters, stabilized by amines, high ammonia concentrations or lower temperatures. While oxidation products of aromatics can nucleate, they play a minor role in urban NPF. Our experiments span 4 orders of magnitude variation of observed NPF rates in ambient conditions. We provide a framework based on NPF and growth rates to interpret ambient observations. Read more
Giant ice rings in southern Baikal: multi-satellite data help to study ice cover dynamics and eddies under ice The Cryosphere DOI 10.5194/tc-15-4501-2021 17 November 2021 Giant ice rings are a beautiful and puzzling natural phenomenon. Our data show that ice rings are generated by lens-like warm eddies below the ice. We use multi-satellite data to analyse lake ice cover in the presence of eddies in April 2020 in southern Baikal. Unusual changes in ice colour may be explained by the competing influences of atmosphere above and the warm eddy below the ice. Tracking ice floes also helps to estimate eddy currents and their influence on the upper water layer. Read more
