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Molecular simulations reveal that heterogeneous ice nucleation occurs at higher temperatures in water under capillary tension

Using computer simulations of water, we find that water under tension freezes more easily than under normal conditions. A linear equation describes how freezing temperature increases with tension. Accordingly, simulations show that naturally occurring tension in water capillary bridges leads to higher freezing temperatures. This work is an early step in determining if atmospheric cloud droplets freeze due to naturally occurring tension, for example, during processes such as droplet collisions.

Modes of Antarctic tidal grounding line migration revealed by Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) laser altimetry

The Cryosphere
DOI 10.5194/tc-17-4079-2023
15 September 2023

We develop a method using ICESat-2 data to measure how Antarctic grounding lines (GLs) migrate across the tide cycle. At an ice plain on the Ronne Ice Shelf we observe 15 km of tidal GL migration, the largest reported distance in Antarctica, dominating any signal of long-term migration. We identify four distinct migration modes, which provide both observational support for models of tidal ice flexure and GL migration and insights into ice shelf–ocean–subglacial interactions in grounding zones.

High-resolution data reveal a surge of biomass loss from temperate and Atlantic pine forests, contextualizing the 2022 fire season distinctiveness in France

Biogeosciences
DOI 10.5194/bg-20-3803-2023
13 September 2023

This study analyses the ecological impact of the 2022 summer fire season in France by using high-resolution satellite data. The total biomass loss was 2.553 Mt, equivalent to a 17 % increase of the average natural mortality of all French forests. While Mediterranean forests had a lower biomass loss, there was a drastic increase in burned area and biomass loss over the Atlantic pine forests and temperate forests. This result revisits the distinctiveness of the 2022 fire season.

Atmospheric drivers of melt-related ice speed-up events on the Russell Glacier in southwest Greenland

The Cryosphere
DOI 10.5194/tc-17-3933-2023
11 September 2023

The Greenland Ice Sheet contributes strongly to sea level rise in the warming climate. One process that can affect the ice sheet’s mass balance is short-term ice speed-up events. These can be caused by high melting or rainfall as the water flows underneath the glacier and allows for faster sliding. In this study we found three main weather patterns that cause such ice speed-up events on the Russell Glacier in southwest Greenland and analysed how they induce local melting and ice accelerations.

Analysis of in situ measurements of electron, ion and neutral temperatures in the lower thermosphere–ionosphere

The relation between electron, ion and neutral temperatures in the lower thermosphere–ionosphere (LTI) is key to understanding the energy balance and transfer between species. However, their simultaneous measurement is rare in the LTI. Based on data from the AE-C, AE-D, AE-E and DE-2 satellites of the 1970s and 1980s, a large number of events where neutrals are hotter than ions are identified and statistically analysed. Potential mechanisms that could trigger these events are proposed.

Calibration of groundwater seepage against the spatial distribution of the stream network to assess catchment-scale hydraulic properties

We propose a model calibration method constraining groundwater seepage in the hydrographic network. The method assesses the hydraulic properties of aquifers in regions where perennial streams are directly fed by groundwater. The estimated hydraulic conductivity appear to be highly sensitive to the spatial extent and density of streams. Such an approach improving subsurface characterization from surface information is particularly interesting for ungauged basins.

Opinion: Atmospheric multiphase chemistry – past, present, and future

With important climate and air quality impacts, atmospheric multiphase chemistry involves gas interactions with aerosol particles and cloud droplets. We summarize the status of the field and discuss potential directions for future growth. We highlight the importance of a molecular-level understanding of the chemistry, along with atmospheric field studies and modelling, and emphasize the necessity for atmospheric multiphase chemists to interact widely with scientists from neighbouring disciplines.

Atmospheric CO2 inversion reveals the Amazon as a minor carbon source caused by fire emissions, with forest uptake offsetting about half of these emissions

The Amazon’s carbon balance may have changed due to forest degradation, deforestation and warmer climate. We used an atmospheric model and atmospheric CO2 observations to quantify Amazonian carbon emissions (2010–2018). The region was a small carbon source to the atmosphere, mostly due to fire emissions. Forest uptake compensated for ~ 50 % of the fire emissions, meaning that the remaining forest is still a small carbon sink. We found no clear evidence of weakening carbon uptake over the period.

Brief communication: The Glacier Loss Day as an indicator of a record-breaking negative glacier mass balance in 2022

The Glacier Loss Day (GLD) is the day on which all mass gained from the accumulation period is lost, and the glacier loses mass irrecoverably for the rest of the mass balance year. In 2022, the GLD was already reached on 23 June at Hintereisferner (Austria), and this led to a record-breaking mass loss. We introduce the GLD as a gross yet expressive indicator of the glacier’s imbalance with a persistently warming climate.

A rise in HFC-23 emissions from eastern Asia since 2015

Based on atmospheric HFC-23 observations, the first estimate of post-CDM HFC-23 emissions in eastern Asia for 2008-2019 shows that these emissions contribute significantly to the global emissions rise. The observation-derived emissions were much larger than the bottom-up estimates expected to approach zero after 2015 due to national abatement activities. These discrepancies could be attributed to unsuccessful factory-level HFC-23 abatement and inaccurate quantification of emission reductions.

Stagnant ice and age modelling in the Dome C region, Antarctica

We combined a numerical model with radar measurements in order to determine the age of ice in the Dome C region of Antarctica. Our results show that at the current ice core drilling sites on Little Dome C, the maximum age of the ice is almost 1.5 Ma. We also highlight a new potential drill site called North Patch with ice up to 2 Ma. Finally, we explore the nature of a stagnant ice layer at the base of the ice sheet which has been independently observed and modelled but is not well understood.

Widespread slowdown in thinning rates of West Antarctic ice shelves

We report on a slowdown in the rate of thinning and melting of West Antarctic ice shelves. We present a comprehensive assessment of the Antarctic ice shelves, where we analyse at a continental scale the changes in thickness, flow, and basal melt over the past 26 years. We also present a novel method to estimate ice shelf change from satellite altimetry and a time-dependent data set of ice shelf thickness and basal melt rates at an unprecedented resolution.

New ring shear deformation apparatus for three-dimensional multiphase experiments: first results

Geoscientific Instrumentation, Methods and Data Systems
DOI 10.5194/gi-12-141-2023
16 August 2023

Multiple geologic hazards, such as landslides and earthquakes, arise when solids and fluids coexist and deform together. We designed an experimental apparatus that allows us to observe such deformation in 3D. The first results show how fluids and solids deform and break at the same time, allowing us to study the impact of both materials on deformation distribution and speed. Making these processes visible has the potential to improve risk assessments associated with geological hazards.

Potential bioavailability of representative pyrogenic organic matter compounds in comparison to natural dissolved organic matter pools

Intensifying wildfires are increasing pyrogenic organic matter (PyOM) production and its impact on water quality. Recent work indicates that PyOM may have a greater impact on aquatic biogeochemistry than previously assumed, driven by higher bioavailability. We provide a full assessment of the potential bioavailability of PyOM across its chemical spectrum. We indicate that PyOM can be actively transformed within the river corridor and, therefore, may be a growing source of riverine C emissions.

Drone-based meteorological observations up to the tropopause – a concept study

The first atmospheric soundings with an electrically powered small uncrewed aircraft system (UAS) up to an altitude of 10 km are presented and assessed for quality, revealing the potential to augment atmospheric observations and fill observation gaps for numerical weather prediction. This is significant because of the need for high-resolution meteorological data, in particular in remote areas with limited in situ measurements, and for reference data for satellite measurement calibration.

The EarthCARE mission – science and system overview

The EarthCARE satellite is due for launch in 2024. It includes four scientific instruments to measure global vertical profiles of aerosols, clouds and precipitation properties together with radiative fluxes and derived heating rates. The mission’s scientific requirements, the satellite and the ground segment are described. In particular, the four scientific instruments and their performance are described at the level of detail required by mission data users.

The three-dimensional structure of fronts in mid-latitude weather systems in numerical weather prediction models

We investigate the benefit of objective 3-D front detection with modern interactive visual analysis techniques for case studies of extra-tropical cyclones and comparisons of frontal structures between different numerical weather prediction models. The 3-D frontal structures show agreement with 2-D fronts from surface analysis charts and augment them in the vertical dimension. We see great potential for more complex studies of atmospheric dynamics and for operational weather forecasting.

DSCIM-Coastal v1.1: an open-source modeling platform for global impacts of sea level rise

This work presents a novel open-source modelling platform for evaluating future sea level rise (SLR) impacts. Using nearly 10 000 discrete coastline segments around the world, we estimate 21st-century costs for 230 SLR and socioeconomic scenarios. We find that annual end-of-century costs range from USD 100 billion under a 2 °C warming scenario with proactive adaptation to 7 trillion under a 4 °C warming scenario with minimal adaptation, illustrating the cost-effectiveness of coastal adaptation.

Detection of large-scale cloud microphysical changes within a major shipping corridor after implementation of the International Maritime Organization 2020 fuel sulfur regulations

Fuel sulfur regulations were implemented for ships in 2020 to improve air quality but may also accelerate global warming. We use spatial statistics and satellite retrievals to detect changes in the size of cloud droplets and find evidence for a resulting decrease in cloud brightness within a major shipping corridor after the sulfur limits went into effect. Our results confirm both that the regulations are being followed and that they are having a warming influence via their effect on clouds.

Design and performance of the Hotrod melt-tip ice-drilling system

Geoscientific Instrumentation, Methods and Data Systems
DOI 10.5194/gi-12-121-2023
31 July 2023

We describe a new drill for glaciers and ice sheets. Instead of drilling down into the ice, via mechanical action, our drill melts into the ice. Our goal is simply to pull a cable of temperature sensors on a one-way trip down to the ice–bed interface. Here, we describe the design and testing of our drill. Under laboratory conditions, our melt-tip drill has an efficiency of ~35 % with a theoretical maximum penetration rate of ~12 m h^-1. Under field conditions, our efficiency is just ~15 %.

Continuous weekly monitoring of methane emissions from the Permian Basin by inversion of TROPOMI satellite observations

We use TROPOMI satellite observations to quantify weekly methane emissions from the US Permian oil and gas basin from May 2018 to October 2020. We find that Permian emissions are highly variable, with diverse economic and activity drivers. The most important drivers during our study period were new well development and natural gas price. Permian methane intensity averaged 4.6% and decreased by 1% per year.

Brief communication: How deep is the snow on Mount Everest?

There is very strong scientific and public interest regarding the snow thickness on Mountain Everest. Previously reported snow depths derived by different methods and instruments ranged from 0.92 to 3.5 m. Our measurements in 2022 provide the first clear radar image of the snowpack at the top of Mount Everest. The snow thickness at Earth’s summit was averaged to be 9.5 ± 1.2 m. This updated snow thickness is considerably deeper than values reported during the past 5 decades.

All about nitrite: exploring nitrite sources and sinks in the eastern tropical North Pacific oxygen minimum zone

Nitrogen (N) is essential for life; thus, its availability plays a key role in determining marine productivity. Using incubations of seawater spiked with a rare form of N measurable on a mass spectrometer, we quantified microbial pathways that determine marine N availability. The results show that pathways that recycle N have higher rates than those that result in its loss from biomass and present new evidence for anaerobic nitrite oxidation, a process long thought to be strictly aerobic.

Review article: Large fluctuations in non-equilibrium physics

Non-equilibrium is dominant in geophysical and climate phenomena. Most of the processes that characterize energy flow occur far from equilibrium. These range from very large systems, such as weather patterns or ocean currents that remain far from equilibrium, owing to an influx of energy, to biological structures. In the last decades, progress in non-equilibrium physics has come from the study of very rare fluctuations, and this paper provides an introduction to these theoretical developments.

Dense water formation in the eastern Mediterranean under a global warming scenario

Global warming may strongly affect dense water formation in the eastern Mediterranean, potentially impacting basin circulation and water properties. We find that at the end of the century dense water formation is reduced by 75 % for the Adriatic, 84 % for the Aegean, and 83 % for the Levantine Sea. This reduction is caused by changes in the temperature and salinity of surface and intermediate waters, which strengthen the vertical stratification, hampering deep convection.

Brief communication: Rapid ∼ 335 × 106 m3 bed erosion after detachment of the Sedongpu Glacier (Tibet)

Following the detachment of the 130 × 10^6 m^3 Sedongpu Glacier (south-eastern Tibet) in 2018, the Sedongpu Valley underwent massive large-volume landscape changes. An enormous volume of in total around 330 × 10^6 m^3 was rapidly eroded, forming a new canyon of up to 300 m depth, 1 km width, and almost 4 km length. Such consequences of glacier change in mountains have so far not been considered at this magnitude and speed.

Impact of deoxygenation and warming on global marine species in the 21st century

Ocean temperature and oxygen shape marine habitats together with species’ characteristics. We calculated the impacts of projected 21st-century warming and oxygen loss on the contemporary habitat volume of 47 marine species and described the drivers of these impacts. Most species lose less than 5 % of their habitat at 2 ◦C of global warming, but some species incur losses 2–3 times greater than that. We also calculate which species may be most vulnerable to climate change and why this is the case.

Impact of a strong volcanic eruption on the summer middle atmosphere in UA-ICON simulations

Strong volcanic eruptions are able to alter the temperature and the circulation of the middle atmosphere. This study simulates the atmospheric response to an idealized strong tropical eruption and focuses on the impact on the mesosphere. The simulations show a warming of the polar summer mesopause in the first November after the eruption. Our study indicates that this is mainly due to dynamical coupling in the summer hemisphere with a potential contribution from interhemispheric coupling.

Quantifying land carbon cycle feedbacks under negative CO2 emissions

We propose a new method to quantify carbon cycle feedbacks under negative CO2 emissions. Our method isolates the lagged carbon cycle response to preceding positive emissions from the response to negative emissions. Our findings suggest that feedback parameters calculated with the novel approach are larger than those calculated with the conventional approach whereby carbon cycle inertia is not corrected for, with implications for the effectiveness of carbon dioxide removal in reducing CO2 levels.

Particle shapes and infrared extinction spectra of nitric acid dihydrate (NAD) crystals: optical constants of the β-NAD modification

Polar stratospheric clouds (PSCs) play an important role in the depletion of stratospheric ozone. They can consist of different chemical species, including crystalline nitric acid hydrates. We found that mineral dust or meteoric ablation material can efficiently catalyse the formation of a specific phase of nitric acid dihydrate crystals. We determined predominant particle shapes and infrared optical properties of these crystals, which are important inputs for remote sensing detection of PSCs.

Diurnal carbon monoxide observed from a geostationary infrared hyperspectral sounder: first result from GIIRS on board FengYun-4B

Observations from geostationary orbit provide contiguous coverage with a high temporal resolution, representing an important advancement over current low-Earth-orbit instruments. Using measurements from GIIRS on board China’s FengYun satellite, the world’s first geostationary hyperspectral infrared sounder, we showed the first results of diurnal CO in eastern Asia from a geostationary orbit, which will have great potential in improving local and global air quality and climate research.

Opinion: How fear of nuclear winter has helped save the world, so far

A nuclear war could produce a nuclear winter, with catastrophic consequences for global food supplies. Nuclear winter theory helped to end the nuclear arms race in the 1980s, but more than 10,000 nuclear weapons still exist. This means they can be used, by unstable leaders, accidentally from technical malfunctions or human error, or by terrorists. Therefore, it is urgent for scientists to study these issues, broadly communicate their results, and work for the elimination of nuclear weapons.

Hyperspectral imaging sediment core scanning tracks high-resolution Holocene variations in (an)oxygenic phototrophic communities at Lake Cadagno, Swiss Alps

This study shows, for the first time, that hyperspectral imaging can detect bacteriochlorophyll pigments produced by green sulfur bacteria in sediment cores. We tested our method on cores from Lake Cadagno, Switzerland, and were able to reconstruct high-resolution variations in the abundance of green and purple sulfur bacteria over the past 12 700 years. Climate conditions, flood events, and land use had major impacts on the lake’s biogeochemical conditions over short and long timescales.

Rate-induced tipping in natural and human systems

Complex systems can undergo abrupt changes or tipping points when external forcing crosses a critical level and are of increasing concern because of their severe impacts. However, tipping points can also occur when the external forcing changes too quickly without crossing any critical levels, which is very relevant for Earth’s systems and contemporary climate. We give an intuitive explanation of such rate-induced tipping and provide illustrative examples from natural and human systems.

Contribution of solitons to enhanced rogue wave occurrence in shallow depths: a case study in the southern North Sea

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-23-2053-2023
26 June 2023

Rogue waves exceed twice the significant wave height. They occur more often than expected in the shallow waters off Norderney. When applying a nonlinear Fourier transform for the Korteweg–de Vries equation to wave data from Norderney, we found differences in the soliton spectra of time series with and without rogue waves. A strongly outstanding soliton in the spectrum indicated an enhanced probability for rogue waves. We could attribute spectral solitons to the measured rogue waves.

Seasonal overturning variability in the eastern North Atlantic subpolar gyre: a Lagrangian perspective

This study uses the trajectories of water parcels traced within an ocean model simulation to identify the pathways responsible for the seasonal cycle of dense water formation (overturning) in the eastern subpolar North Atlantic. We show that overturning seasonality is due to the fastest water parcels circulating within the eastern basins in less than 8.5 months. Slower pathways set the average strength of overturning in this region since water parcels cannot escape intense wintertime cooling.

Applying machine learning to improve the near-real-time products of the Aura Microwave Limb Sounder

The algorithm that produces the near-real-time data products of the Aura Microwave Limb Sounder has been updated. The new algorithm is based on machine learning techniques and yields data products with much improved accuracy. It is shown that the new algorithm outperforms the previous versions, even when it is trained on only a few years of satellite observations. This confirms the potential of applying machine learning to the near-real-time efforts of other current and future mission concepts.

The 2018 west-central European drought projected in a warmer climate: how much drier can it get?

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-23-1921-2023
19 June 2023

To examine the impact of global warming on west-central European droughts, we have constructed future analogues of recent summers. Extreme droughts like 2018 further intensify, and the local temperature rise is much larger than in most summers. Years that went hardly noticed in the present-day climate may emerge as very dry and hot in a warmer world. The changes can be directly linked to real-world events, which makes the results very tangible and hence useful for climate change communication.

The Volyn biota (Ukraine) – indications of 1.5 Gyr old eukaryotes in 3D preservation, a spotlight on the “boring billion”

This research describes the occurrence of Precambrian fossils, with exceptionally well preserved morphology in 3D. These microfossils reach a size of millimeters (possibly up to centimeters) and thus indicate the presence of multicellular eukaryotes. Many of them are filamentous, but other types were also found. These fossils lived in a depth of several hundred meters and thus provide good evidence of a continental the deep biosphere, from a time generally considered as the “boring billion”.

Pace v0.2: a Python-based performance-portable atmospheric model

It is hard for scientists to write code which is efficient on different kinds of supercomputers. Python is popular for its user-friendliness. We converted a Fortran code, simulating Earth’s atmosphere, into Python. This new code auto-converts to a faster language for processors or graphic cards. Our code runs 3.5–4 times faster on graphic cards than the original on processors in a specific supercomputer system.

What distinguishes 100-year precipitation extremes over central European river catchments from more moderate extreme events?

In this study, we analyse the generic atmospheric processes of very extreme, 100-year precipitation events in large central European river catchments and the corresponding differences to less extreme events, based on a large time series (~1200 years) of simulated but realistic daily precipitation events from the ECMWF. Depending on the catchment, either dynamical mechanisms or thermodynamic conditions or a combination of both distinguish 100-year events from less extreme precipitation events.

Response of the sea surface temperature to heatwaves during the France 2022 meteorological summer

In the summer of 2022, France experienced a series of unprecedented heatwaves. This study is the first to examine the response of sea surface temperatures to these events, using spatial operational data and attributing the observed abnormally warm SSTs to atmospheric forcings. The findings of this study underscore the critical need for an efficient and sustainable operational system to monitor alterations that threaten the oceans in the context of climate change.

Paleontology-themed comics and graphic novels, their potential for scientific outreach, and the bilingual graphic novel EUROPASAURUS – Life on Jurassic Islands

We give an overview of influential comics and graphic novels on paleontological themes, especially dinosaurs. We explain their different forms of representation and narration, and how they were influenced by the contemporary state of knowledge. The second part deals with the creation of the bilingual graphic novel EUROPASAURUS – Life on Jurassic Islands, a textless comic book, and how this book was perceived by the public.

Constraints on long-term cliff retreat and intertidal weathering at weak rock coasts using cosmogenic 10Be, nearshore topography and numerical modelling

This study uses a coastal evolution model to interpret cosmogenic beryllium-10 concentrations and topographic data and, in turn, quantify long-term cliff retreat rates for four chalk sites on the south coast of England. By using a process-based model, clear distinctions between intertidal weathering rates have been recognised between chalk and sandstone rock coast sites, advocating the use of process-based models to interpret the long-term behaviour of rock coasts.

The extremely hot and dry 2018 summer in central and northern Europe from a multi-faceted weather and climate perspective

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-23-1699-2023
31 May 2023

The objective of this study was to perform a comprehensive, multi-faceted analysis of the 2018 extreme summer in terms of heat and drought in central and northern Europe, with a particular focus on Germany. A combination of favourable large-scale conditions and locally dry soils were related with the intensity and persistence of the events. We also showed that such extremes have become more likely due to anthropogenic climate change and might occur almost every year under +2 °C of global warming.

Quantifying gender gaps in seismology authorship

We investigate women’s representation in seismology to raise awareness of existing gender disparities.
By analysing the authorship of peer-reviewed articles, we identify lower representation of women among single authors, high-impact authors, and highly productive authors. Seismology continues to be a male-dominated field, and trends suggest that parity is decades away. These gaps are an obstacle to women’s career advancement and, if neglected, may perpetuate the leaky-pipeline problem.

Opinion: The scientific and community-building roles of the Geoengineering Model Intercomparison Project (GeoMIP) – past, present, and future

Geoengineering indicates methods aiming to reduce the temperature of the planet by means of reflecting back a part of the incoming radiation before it reaches the surface or allowing more of the planetary radiation to escape into space. It aims to produce modelling experiments that are easy to reproduce and compare with different climate models, in order to understand the potential impacts of these techniques. Here we assess its past successes and failures and talk about its future.

Evaluation of liquefaction triggering potential in Italy: a seismic-hazard-based approach

Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-23-1685-2023
24 May 2023

In the present study, we analyse ground-motion hazard maps and hazard disaggregation in order to define areas in Italy where liquefaction triggering due to seismic activity can not be excluded. The final result is a screening map for all of Italy that classifies sites in terms of liquefaction triggering potential according to their seismic hazard level. The map and the associated data are freely accessible at the following web address: www.distav.unige.it/rsni/milq.php.

Reversible ice sheet thinning in the Amundsen Sea Embayment during the Late Holocene

Samples of bedrock recovered from below the West Antarctic Ice Sheet show that part of the ice sheet was thinner several thousand years ago than it is now and subsequently thickened. This is important because of concern that present ice thinning in this region may lead to rapid, irreversible sea level rise. The past episode of thinning at this site that took place in a similar, although not identical, climate was not irreversible; however, reversal required at least 3000 years to complete.

Reconstructing ocean carbon storage with CMIP6 Earth system models and synthetic Argo observations

We present a new method for reconstructing ocean carbon using climate models and temperature and salinity observations. To test this method, we reconstruct modelled carbon using synthetic observations consistent with current sampling programmes. Sensitivity tests show skill in reconstructing carbon trends and variability within the upper 2000 m. Our results indicate that this method can be used for a new global estimate for ocean carbon content.