Vulnerability of European ecosystems to two compound dry and hot summers in 2018 and 2019 Earth System Dynamics DOI 10.5194/esd-12-1015-2021 24 December 2021 Temperate biomes in Europe are not prone to recurrent dry and hot conditions in summer. However, these conditions may become more frequent in the coming decades. Because stress conditions can leave legacies for many years, this may result in reduced ecosystem resilience under recurrent stress. We assess vegetation vulnerability to the hot and dry summers in 2018 and 2019 in Europe and find the important role of inter-annual legacy effects from 2018 in modulating the impacts of the 2019 event. Read more
How alkaline compounds control atmospheric aerosol particle acidity Atmospheric Chemistry and Physics DOI 10.5194/acp-21-14983-2021 22 December 2021 Aerosol particle pH is well-buffered by alkaline compounds, notably NH3 and crustal elements. NH3 is found to supply remarkable buffering capacity on a global scale, from the polluted continents to the remote oceans. Potential future changes in agricultural NH3 must be accompanied by strong reductions of SO2 and NOx to avoid particles becoming highly acidic, with implications for human health (aerosol toxicity), ecosystems (acid deposition), clouds, and climate (aerosol hygroscopicity). Read more
Aerosol–cloud interactions: the representation of heterogeneous ice activation in cloud models Atmospheric Chemistry and Physics DOI 10.5194/acp-21-15213-2021 20 December 2021 Aerosol–cloud interactions play an important role in climate change. Simulations of the competition between homogeneous solution droplet freezing and heterogeneous ice nucleation can be compromised by the misapplication of ice-active particle fractions frequently derived from laboratory measurements or parametrizations. Our study frames the problem and establishes a solution that is easy to implement in cloud models. Read more
Deep ice as a geochemical reactor: insights from iron speciation and mineralogy of dust in the Talos Dome ice core (East Antarctica) The Cryosphere DOI 10.5194/tc-15-4807-2021 17 December 2021 As scientists are pushing efforts to recover deep ice cores to extend paleoclimatic reconstructions, it is now essential to explore deep ice. The latter was considered a relatively stable environment, but this view is changing. This study shows that the conditions of deep ice promote the interaction between soluble and insoluble impurities, favoring complex geochemical reactions that lead to the englacial dissolution and precipitation of specific minerals present in atmospheric mineral dust. Read more
Ambient aerosol properties in the remote atmosphere from global-scale in situ measurements Atmospheric Chemistry and Physics DOI 10.5194/acp-21-15023-2021 15 December 2021 The Atmospheric Tomography Mission was an airborne study that mapped the chemical composition of the remote atmosphere. From this, we developed a comprehensive description of aerosol properties that provides a unique, global-scale dataset against which models can be compared. The data show the polluted nature of the remote atmosphere in the Northern Hemisphere and quantify the contributions of sea salt, dust, soot, biomass burning particles, and pollution particles to the haziness of the sky. Read more
Statistical characteristics of extreme daily precipitation during 1501 BCE–1849 CE in the Community Earth System Model Climate of the Past DOI 10.5194/cp-17-2031-2021 13 December 2021 To understand the natural characteristics and future changes of the global extreme daily precipitation, it is necessary to explore the long-term characteristics of extreme daily precipitation. Here, we used climate simulations to analyze the characteristics and long-term changes of extreme precipitation during the past 3351 years. Our findings indicate that extreme precipitation in the past is associated with internal climate variability and regional surface temperatures. Read more
Modeling the marine chromium cycle: new constraints on global-scale processes Biogeosciences DOI 10.5194/bg-18-5447-2021 10 December 2021 Chromium (Cr) is a redox-sensitive element that holds promise as a tracer of ocean oxygenation and biological activity. We here implemented the oxidation states Cr(III) and Cr(VI) in the Bern3D model to investigate the processes that shape the global Cr distribution. We find a Cr ocean residence time of 5–8 kyr and that the benthic source dominates the tracer budget. Further, regional model–data mismatches suggest strong Cr removal in oxygen minimum zones and a spatially variable benthic source. Read more
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
Stalagmite carbon isotopes suggest deglacial increase in soil respiration in western Europe driven by temperature change Climate of the Past DOI 10.5194/cp-17-1903-2021 15 November 2021 Soil respiration is a critical but poorly constrained component of the global carbon cycle. We analyse the effect of changing soil respiration rates on the stable carbon isotope ratio of speleothems from northern Spain covering the last deglaciation. Using geochemical analysis and forward modelling we quantify the processes affecting speleothem stable carbon isotope ratios and extract a signature of increasing soil respiration synchronous with deglacial warming. Read more
Relative humidity gradients as a key constraint on terrestrial water and energy fluxes Hydrology and Earth System Sciences DOI 10.5194/hess-25-5175-2021 12 November 2021 Here, we present a novel physically based evaporation model to demonstrate that vertical relative humidity (RH) gradients from the land surface to the atmosphere tend to evolve towards zero due to land–atmosphere equilibration processes. Collapsing RH gradients on daily to yearly timescales indicate an emergent land–atmosphere equilibrium, making it possible to determine evapotranspiration using only meteorological information, independent of land surface conditions and vegetation controls. Read more
Enhanced moisture delivery into Victoria Land, East Antarctica, during the early Last Interglacial: implications for West Antarctic Ice Sheet stability Climate of the Past DOI 10.5194/cp-17-1841-2021 10 November 2021 Here we reconstruct the rate of snow accumulation during the Last Interglacial period in an East Antarctic ice core located near the present-day northern edge of the Ross Ice Shelf. We find an order-of-magnitude increase in the accumulation rate during the peak warming in the Last Interglacial. This large increase in mass accumulation is compatible with less ice cover in the Ross Sea, perhaps created by a partly collapsed West Antarctic Ice Sheet, whose stability in a warming world is uncertain. Read more