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Earth System Dynamics

A quantitative approach to evaluating the GWP timescale through implicit discount rates

The 100-year GWP is the most widely used metric for comparing the climate impact of different gases such as methane and carbon dioxide. However, there have been recent arguments for the use of different timescales. This paper uses straightforward estimates of future damages to quantitatively determine the appropriate timescale as a function of how society discounts the future and finds that the 100-year timescale is consistent with commonly used discount rates.

Biogeosciences

Ideas and perspectives: Strengthening the biogeosciences in environmental research networks

As knowledge in biology and geology explodes, science becomes increasingly specialised. Given the overlap of the environmental sciences, however, the explosion in knowledge inevitably creates opportunities for interconnecting the biogeosciences. Here, 30 scientists emphasise the opportunities for biogeoscience collaborations across the world’s remarkable long-term environmental research networks that can advance science and engage larger scientific and public audiences.

The Cryosphere

Channelized, distributed, and disconnected: subglacial drainage under a valley glacier in the Yukon

We analyse a large glacier borehole pressure dataset and provide a holistic view of the observations, suggesting a consistent picture of the evolution of the subglacial drainage system. Some aspects are consistent with the established understanding and others ones are not. We propose that most of the inconsistencies arise from the capacity of some areas of the bed to become hydraulically isolated. We present an adaptation of an existing drainage model that incorporates this phenomena.

Atmospheric Chemistry and Physics

Formation and evolution of tar balls from northwestern US wildfires

This paper presents the first direct atmospheric observations of the formation and evolution of tar balls (TBs) in forest fires collected during the Department of Energy’s Biomass Burning Observation Project (BBOP). We quantify, for the first time, the TB mass fraction in the BB plumes and show that this mass fraction increases from less than 1 % to 50 % within the first couple of hours of plume aging. Using Mie theory we find that TBs are consistent with being weak light absorbers.

Climate of the Past

Testing the consistency between changes in simulated climate and Alpine glacier length over the past millennium

Glaciers provide iconic illustrations of past climate change, but records of glacier length fluctuations have not been used systematically to test the ability of models to reproduce past changes. One reason is that glacier length depends on several complex factors and so cannot be simply linked to the climate simulated by models. This is done here, and it is shown that the observed glacier length fluctuations are generally well within the range of the simulations.

Annales Geophysicae

The mirror mode: a “superconducting” space plasma analogue

The physics of the magnetic mirror mode in its final state of saturation, the thermodynamic equilibrium, is re-examined to demonstrate that the mirror mode is the classical analogue of a superconducting effect in an anisotropic-pressure space plasma. Three different spatial correlation scales are identified which control the behaviour of its evolution into large-amplitude chains of mirror bubbles.

Earth System Dynamics

Using network theory and machine learning to predict El Niño

The prediction of the El Niño phenomenon, an increased sea surface temperature in the eastern Pacific, fascinates people for a long time. El Niño is associated with natural disasters, such as droughts and floods. Current methods can make a reliable prediction of this phenomenon up to 6 months ahead. However, this article presents a method which combines network theory and machine learning which predicts El Niño up to 1 year ahead.

Atmospheric Chemistry and Physics

HTAP2 multi-model estimates of premature human mortality due to intercontinental transport of air pollution and emission sectors

Emissions from one continent affect air quality and health elsewhere. Here we quantify the effects of intercontinental PM_2.5 and ozone transport on human health using a new multi-model ensemble, evaluating the health effects of emissions from six world regions and three emission source sectors. Emissions from one region have significant health impacts outside of that source region; similarly, foreign emissions contribute significantly to air-pollution-related deaths in several world regions.

The Cryosphere

Dynamic response of Antarctic Peninsula Ice Sheet to potential collapse of Larsen C and George VI ice shelves

Despite the speculation on the state and fate of Larsen C Ice Shelf, a key unknown factor remains: what would be the effects of ice-shelf collapse on upstream drainage basins and thus global sea levels? In our paper three state-of-the-art numerical ice-sheet models were used to simulate the volume evolution of the inland ice sheet to ice-shelf collapse at Larsen C and George VI ice shelves. Our results suggest sea-level rise of up to ~ 4 mm for Larsen C ice shelf and ~ 22 for George VI ice shelf.

Atmospheric Chemistry and Physics

Mineralogy and physicochemical features of Saharan dust wet deposited in the Iberian Peninsula during an extreme red rain event

Saharan dust wet deposited in Granada (Spain) on 21–23 February 2017 during the most extreme red rain event of the last decades led to the deposition of ~ 140 000 T of dust just in the city of Granada, dwarfing any other standard Saharan dust events taking place in the area. The multianalytical study of Saharan dust disclosed potential source areas and the mineralogy and composition of the size fractions of desert dust as well as its potential biogeochemical, radiative, and health effects.

Biogeosciences

In-depth characterization of diazotroph activity across the western tropical South Pacific hotspot of N₂ fixation (OUTPACE cruise)

Here we report N₂ fixation rates from a ∼ 4000 km transect in the western and central tropical South Pacific, a particularly undersampled region in the world ocean.

Annales Geophysicae

Ionospheric and thermospheric response to the 27–28 February 2014 geomagnetic storm over north Africa

The novelty of this paper lies in the fact that it addresses the thermosphere–ionosphere coupling in a midlatitude site in north Africa. We have used Fabry–Perot measurements of thermospheric winds and wide-angle camera detection of ionospheric structures at an altitude of about 250 km. We have also used GPS data to extract the TEC over the studied area. We have focused our study on the 27 February geomagnetic storm.

Ocean Science

On the role of the North Equatorial Counter Current during a strong El Niño

Results from a high-resolution ocean model show that during the strong El Niños of 1983 and 1998, transport of warm water in the equatorial Pacific was dominated by the North Equatorial Counter Current and not by equatorial Kelvin waves. The results show why the NECC fails to do this in most years and how stronger than normal annual Rossby waves near the Equator can both trigger the El Niño in the western Pacific and help to ensure that the warm water arrives off South America around Christmas.

Hydrology and Earth System Sciences

On the dynamic nature of hydrological similarity

In this study we explore the role of spatially distributed information on hydrological modeling. For that, we develop and test an approach which draws upon information theory and thermodynamic reasoning. We show that the proposed set of methods provide a powerful framework for understanding and diagnosing how and when process organization and functional similarity of hydrological systems emerge in time and, hence, when which landscape characteristic is important in a model application.

Nonlinear Processes in Geophysics

Parametric covariance dynamics for the nonlinear diffusive Burgers equation

The forecast of weather prediction uncertainty is a real challenge and is crucial for risk management. However, uncertainty prediction is beyond the capacity of supercomputers, and improvements of the technology may not solve this issue. A new uncertainty prediction method is introduced which takes advantage of fluid equations to predict simple quantities which approximate real uncertainty but at a low numerical cost. A proof of concept is shown by an academic model derived from fluid dynamics.

Atmospheric Chemistry and Physics

The diurnal cycle of cloud profiles over land and ocean between 51°S and 51°N, seen by the CATS spaceborne lidar from the International Space Station

From 3 years of observations from the CATS lidar on the International Space Station we document the daily cycle of the vertical distribution of clouds. This is the first time this is documented over several continents and oceans using finely resolved measurements on a near-global scale from a single instrument. We show that other instruments observing clouds from space, like CALIPSO, document extremes of the daily cycle over ocean and closer to the average over land.

Hydrology and Earth System Sciences

Inter-laboratory comparison of cryogenic water extraction systems for stable isotope analysis of soil water

To extract water from soils for isotopic analysis, cryogenic water extraction is the most widely used removal technique. This work presents results from a worldwide laboratory intercomparison test of cryogenic extraction systems. Our results showed large differences in retrieved isotopic signatures among participating laboratories linked to interactions between soil type and properties, system setup, extraction efficiency, extraction system leaks, and each lab’s internal accuracy.

Atmospheric Chemistry and Physics

Transboundary ozone pollution across East Asia: daily evolution and photochemical production analysed by IASI + GOME2 multispectral satellite observations and models

This paper tackles a major issue for air quality over East Asia: ozone pollution produced over a major source, like the North China Plain, and the contribution of ozone produced while being transported across the continent and the surrounding seas. The main originality of the paper lays in the fact that this photochemical production of ozone is observationally quantified with new multispectral satellite observations offering unique skills to observe the ozone pollution plumes near the surface.

Biogeosciences

A 1500-year multiproxy record of coastal hypoxia from the northern Baltic Sea indicates unprecedented deoxygenation over the 20th century

Oxygen deficiency is a major environmental problem deteriorating seafloor habitats especially in the coastal ocean with large human impact. Here we apply a wide set of chemical and physical analyses to a 1500-year long sediment record and show that, although long-term climate variability has modulated seafloor oxygenation in the coastal northern Baltic Sea, the oxygen loss over the 20th century is unprecedentedly severe, emphasizing the need to reduce anthropogenic nutrient input in the future.

Earth System Dynamics

Moisture transport and Antarctic sea ice: austral spring 2016 event

In austral spring 2016 the Antarctic region experienced anomalous sea ice retreat in all sectors, with sea ice extent in October and November 2016 being the lowest in the Southern Hemisphere over the observational record (1979–present). The extreme sea ice retreat was accompanied by the wettest and warmest spring on record, over large areas covering the Indian ocean, the Ross Sea, and the Weddell Sea.

Hydrology and Earth System Sciences

HESS Opinions: Science in today’s media landscape – challenges and lessons from hydrologists and journalists

Media play a key role in the communication between scientists and the general public. However, the interaction between scientists and journalists is not always straightforward. In this opinion paper, we present insights from hydrologists and journalists into the benefits, aftermath and potential pitfalls of science–media interaction. We aim to encourage scientists to participate in the diverse and evolving media landscape, and we call on the scientific community to support scientists who do so.

Atmospheric Chemistry and Physics

High- and low-temperature pyrolysis profiles describe volatile organic compound emissions from western US wildfire fuels

We found that on average 85 % of the VOC emissions from biomass burning across various fuels representative of the western US (including various coniferous and chaparral fuels) can be explained using only two emission profiles: (i) a high-temperature pyrolysis profile and (ii) a low-temperature pyrolysis profile. The high-temperature profile is quantitatively similar between different fuel types (r² > 0.84), and likewise for the low-temperature profile.

Annales Geophysicae

Transfer entropy and cumulant-based cost as measures of nonlinear causal relationships in space plasmas: applications to Dst

The magnetospheric response to the solar wind is nonlinear. Information theoretical tools are able to characterize the nonlinearities in the system. We show that nonlinear significance ofD_stpeaks at lags of 3–12 hours which can be attributed toVB_s, which also exhibits similar behavior. However, the nonlinear significance that peaks at lags of 25, 50, and 90 hours can be attributed to internal dynamics, which may be related to the relaxation of the ring current.

The Cryosphere

Brief communication: Candidate sites of 1.5 Myr old ice 37 km southwest of the Dome C summit, East Antarctica

Locating a suitable drill site is a key step in the Antarctic oldest-ice challenge. Here we have conducted a 3-D ice flow simulation in the region of Dome C using a refined bedrock description. Five selection criteria are computed that together provide an objective overview on the local ice flow conditions. We delineate kilometer-scale favorable areas that overlap with the ones recently proposed by another group. We propose a few drill sites that should be surveyed during the next field seasons.

Atmospheric Measurement Techniques

Quality assessment of the Ozone_cci Climate Research Data Package (release 2017) – Part 2: Ground-based validation of nadir ozone profile data products

This work, performed at the Royal Belgian Institute for Space Aeronomy and the second in a series of four Ozone_cci papers, reports for the first time on data content studies, information content studies, and comparisons with co-located ground-based reference observations for all 13 nadir ozone profile data products that are part of the Climate Research Data Package (CRDP) on atmospheric ozone of the European Space Agency’s Climate Change Initiative.

Ocean Science

Electromagnetic characteristics of ENSO

The study finds that changes in seawater temperature due to El Niño and La Niña, anomalous warm and cold events, are in principle detectable by means of the oceanic tidally induced magnetic field. Furthermore, subsurface processes in the onset of those anomalous events lead the surface processes by several months. This causes a lead in the oceanic tidally induced magnetic field signals over sea-surface temperature signals.

Ocean Science

Acoustic mapping of mixed layer depth

The ocean surface mixed layer depth (MLD) is an important parameter within several research disciplines, as variations in the MLD influence air–sea CO₂ exchange and ocean primary production. A new method is presented in which acoustic mapping of the MLD is done remotely by means of echo sounders. This method allows for observations of high-frequency variability in the MLD, as horizontal and temporal resolutions can be increased by orders of magnitude compared to traditional in situ measurements.

Annales Geophysicae

New high-frequency (7–12 kHz) quasi-periodic VLF emissions observed on the ground at L ∼ 5.5

We reveal previously unknown quasi-periodic (QP) VLF emissions at the unusually high-frequency band of ~ 7–11 kHz by applying the digital filtering of strong sferics to the ground-based VLF data recorded at Kannuslehto station (KAN). In one event, the spectral–temporal forms of the emissions looked like a series of giantbullets, with very abrupt cessation. In the second event, the modulation period was about 3 min under the absence of the simultaneous geomagnetic pulsations.

Biogeosciences

Transfer of diazotroph-derived nitrogen to the planktonic food web across gradients of N₂ fixation activity and diversity in the western tropical South Pacific Ocean

Biological dinitrogen (N₂) fixation provides the major source of new nitrogen (N) to the open ocean, contributing more than atmospheric deposition and riverine inputs to the N supply. Yet the fate of the diazotroph-derived N (DDN) in the planktonic food web is poorly understood. The main goals of this study were (i) to quantify how much of DDN is released to the dissolved pool during N₂ fixation and how much is transferred to bacteria, phytoplankton and zooplankton, and (ii) to compare the DDN release and transfer efficiencies under contrasting N₂ fixation activity and diversity in the oligotrophic waters of the western tropical South Pacific Ocean.

Earth System Dynamics

Climate sensitivity estimates – sensitivity to radiative forcing time series and observational data

A key question in climate science is how the global mean surface temperature responds to changes in greenhouse gases. This dependency is quantified by the climate sensitivity, which is determined by the complex feedbacks in the climate system. In this study observations of past climate change are used to estimate this sensitivity. Our estimate is consistent with values for the equilibrium climate sensitivity estimated by complex climate models but sensitive to the use of uncertain input data.

Solid Earth

The seismogenic fault system of the 2017 Mw 7.3 Iran–Iraq earthquake: constraints from surface and subsurface data, cross-section balancing, and restoration

A balanced cross section across the hypocentre of the 2017 Iran–Iraq M_w7.3 earthquake is presented. The structural style of the area is characterised by inversion tectonics with partial decoupling between the basement and the 10 km thick sedimentary cover. The main shock is located along a low-dipping lateral ramp of the Mountain Front Fault. The balanced cross section indicates that the Mountain Front Fault is the only fault where an M_w7.3 earthquake may occur.

Biogeosciences

Reviews and syntheses: Carbonyl sulfide as a multi-scale tracer for carbon and water cycles

Measurements of the trace gas carbonyl sulfide (OCS) are helpful in quantifying photosynthesis at previously unknowable temporal and spatial scales. While CO₂ is both consumed and produced within ecosystems, OCS is mostly produced in the oceans or from specific industries, and destroyed in plant leaves in proportion to CO₂. This review summarizes the advancements we have made in the understanding of OCS exchange and applications to vital ecosystem water and carbon cycle questions.

Biogeosciences

Field-warmed soil carbon changes imply high 21st-century modeling uncertainty

The temperature sensitivity of soil carbon loss is a critical parameter for projecting future CO₂. Isolating soil temperature response in the field is challenging due to difficulties isolating root and microbial respiration. We use a database of direct-warming soil carbon changes to generate a new global temperature sensitivity. Incorporating this into Earth system models reduces projected soil carbon. But it also shows that variation due to this parameter is as high as all other causes.

Atmospheric Chemistry and Physics

Estimates of ozone return dates from Chemistry-Climate Model Initiative simulations

We analyse simulations from the Chemistry-Climate Model Initiative (CCMI) to estimate the return dates of the stratospheric ozone layer from depletion by anthropogenic chlorine and bromine. The simulations from 20 models project that global column ozone will return to 1980 values in 2047 (uncertainty range 2042–2052). Return dates in other regions vary depending on factors related to climate change and importance of chlorine and bromine. Column ozone in the tropics may continue to decline.

Earth System Dynamics

On the social dynamics of moisture recycling

Moisture recycling is the atmospheric branch of the water cycle, including evaporation and precipitation. While the physical water cycle is well-understood, the social links among the recipients of precipitation back to the sources of evaporation are not. In this work, we develop a method to determine how these social connections unfold, using a mix of quantitative and qualitative methods, finding that there are distinct types of social connections with corresponding policy and management tools.

Earth System Dynamics

Hazards of decreasing marine oxygen: the near-term and millennial-scale benefits of meeting the Paris climate targets

Human-caused, climate change hazards in the ocean continue to aggravate over a very long time. For business as usual, we project the ocean oxygen content to decrease by 40 % over the next thousand years. This would likely have severe consequences for marine life. Global warming and oxygen loss are linked, and meeting the warming target of the Paris Climate Agreement effectively limits related marine hazards. Developments over many thousands of years should be considered to assess marine risks.

Atmospheric Chemistry and Physics

Surface impacts of the Quasi Biennial Oscillation

A major phenomenon in the stratosphere is the Quasi Biennial Oscillation (QBO). Although a feature of the equatorial stratosphere, its influence extends to surface weather at both equatorial and mid latitudes. Improved knowledge of mechanisms of influence should help to improve weather forecasts. In this paper, QBO impacts at the surface are characterized and dominant mechanisms explored. Three pathways are identified, referred to as the tropical, subtropical and polar routes.

Earth Surface Dynamics

On the Holocene evolution of the Ayeyawady megadelta

Here we provide the first results on the evolution of the Ayeyarwady delta, the last unstudied megadelta of Asia. In addition to its intrinsic value as a founding study on the Holocene development of this region, we advance new ideas on the climate control of monsoonal deltas as well as describe for the first time a feedback mechanism between tectonics and tidal hydrodynamics that can explain the peculiarities of the Ayeyarwady delta.

Atmospheric Measurement Techniques

Airborne wind lidar observations over the North Atlantic in 2016 for the pre-launch validation of the satellite mission Aeolus

This work reports airborne wind lidar observations performed in a recent field campaign. The deployed lidar system serves as a demonstrator for the satellite instrument ALADIN on board Aeolus, which is scheduled for launch in 2018 and will become the first wind lidar in space. After presenting the measurement principle, operation procedures and wind retrieval algorithm, the obtained wind results are validated and discussed, providing valuable information in preparation for the satellite mission.

Geoscience Communication

Editorial: Geoscience Communication – Building bridges, not walls

Welcome to the journal of Geoscience Communication! We decided to write this editorial in order to introduce ourselves (the executive editors of GC), to provide a history of its development, and to serve as a guideline for future authors who wish to submit to this journal. We hope that this article serves as a useful aid for people who are considering publishing in GC, as well as the wider geoscience community, and that it can act in the first instance as a FAQ for authors, editors, and readers alike.

Earth System Dynamics

Two drastically different climate states on an Earth-like terra-planet

Using climate simulations, we investigate the role of water recycling in shaping the climate of low-obliquity Earth-like terra-planets. By such a mechanism feeding water back from the extra-tropics to the tropics, the planet can assume two drastically different climate states differing by more than 35 K in global temperature. We describe the bifurcation between the two states occurring upon changes in surface albedo and argue that the bistability hints at a wider habitable zone for such planets.

Earth System Dynamics

Assessing the impact of a future volcanic eruption on decadal predictions

The likelihood of a large volcanic eruption in the future provides the largest uncertainty concerning the evolution of the climate system on the timescale of a few years, but also an excellent opportunity to learn about the behavior of the climate system, and our models thereof. So the following question emerges: how predictable is the response of the climate system to future eruptions? By this we mean to what extent will the volcanic perturbation affect decadal climate predictions and how does the pre-eruption climate state influence the impact of the volcanic signal on the predictions?

Ocean Science

High-resolution diapycnal mixing map of the Alboran Sea thermocline from seismic reflection images

The Alboran Sea is a dynamically active region. The interaction between Mediterranean and Atlantic water originates a set of sub-mesoscale structures and a complex sequence of processes that entail mixing close to the thermocline. Here we present a high-resolution map of the diapycnal diffusivity around the thermocline depth obtained using acoustic data recorded with a high-resolution multichannel seismic system. The map revels a patchy thermocline, with areas of strong diapycnal mixing.

The Cryosphere

Snow depth on Arctic sea ice from historical in situ data

In this paper we analyze snow data from Soviet airborne expeditions, Sever, which operated in late winter 1959-1986, in the Arctic and made snow measurements on the ice around plane landing sites. The snow measurements were made on the multiyear ice in the central Arctic and on the first-year ice in the Eurasian seas in the areas for which snow characteristics are poorly described in the literature. The main goal of this study is to produce an improved data set of snow depth on the sea ice.

Ocean Science

Consideration of various aspects in a drift study of MH370 debris

To assist in establishing the most likely location of the crash site of MH370, a Boeing 777 aircraft that went missing on March 7, 2014, a drift study was conducted by means of numerical modelling. Three elements were considered: (a) the efficacy of the aerial search; (b) water temperatures along the path of the flaperon; © beached debris distribution. The results obtained indicate the crash site is likely located between 25.5° S and 30.5° S along the so-called seventh arc in the Indian Ocean.

Atmospheric Chemistry and Physics

On ozone trend detection: using coupled chemistry–climate simulations to investigate early signs of total column ozone recovery

2017 marks the 30th anniversary of the Montreal Protocol, which was implemented to protect the stratospheric ozone layer from the harmful effects of synthetic ozone depleting substances. Since the late 1990s atmospheric concentrations of these species have begun to decline, and as a result ozone concentrations are expected to increase. In this study we use an ensemble of chemistry–climate simulations to investigate recent ozone trends and search for early signs of ozone recovery.

Earth Surface Dynamics

Glacial isostatic adjustment modelling: historical perspectives, recent advances, and future directions

This article is a contribution to a special issue onTwo centuries of modelling across scales. It describes the historical observations, evolving hypotheses, and early calculations that led to the development of the field of glacial isostatic sdjustment (GIA) modelling, which seeks to understand feedbacks between ice-sheet change, sea-level change, and solid Earth deformation. Recent and future advances are discussed. Future progress will likely involve an interdisciplinary approach.

Climate of the Past

Aromatic acids in an Arctic ice core from Svalbard: a proxy record of biomass burning

This study presents organic acid levels in an ice core from Svalbard over the past 800 years. These acids are produced from wildfire emissions and transported as aerosol. Organic acid levels are high early in the record and decline until the 20th century. Siberia and Europe are likely the primary source regions of the fire emissions. The data are similar to those from a Siberian ice core prior to 1400 CE. The timing of the divergence after 1400 CE is similar to a shift in North Atlantic climate.

Earth System Dynamics

Estimating sowing and harvest dates based on the Asian summer monsoon

Sowing and harvest dates are a significant source of uncertainty within crop models. South Asia is one region with a large uncertainty. We aim to provide more accurate sowing and harvest dates than currently available and that are relevant for climate impact assessments. This method reproduces the present day sowing and harvest dates for most parts of India and when applied to two future periods provides a useful way of modelling potential growing season adaptations to changes in future climate.

Earth System Dynamics

Analytically tractable climate–carbon cycle feedbacks under 21st century anthropogenic forcing

Around half of the carbon that humans emit into the atmosphere each year is taken up on land (by trees) and in the ocean (by absorption). We construct a simple model of carbon uptake that, unlike the complex models that are usually used, can be analysed mathematically. Our results include that changes in atmospheric carbon may affect future carbon uptake more than changes in climate. Our simple model could also study mechanisms that are currently too uncertain for complex models.