<p>Simulating the Earth's climate is an important and complex problem, thus climate models are similarly complex, comprised of millions of lines of code. In order to appropriately utilize the latest computational and software infrastructure advancements in Earth system models running on modern hybrid computing architectures to improve their performance, precision, accuracy, or all three; it is important to ensure that model simulations are repeatable and robust. This introduces the need for establishing statistical or non-bit-for-bit reproducibility, since bit-for-bit reproducibility may not always be achievable. Here, we propose a short-simulation ensemble-based test for an atmosphere model to evaluate the null hypothesis that modified model results are statistically equivalent to that of the original model. We implement this test in version 2 of the US Department of Energy's Energy Exascale Earth System Model (E3SM). The test evaluates a standard set of output variables across the two simulation ensembles and uses a false discovery rate correction to account for multiple testing. The false positive rates of the test are examined using re-sampling techniques on large simulation ensembles and are found to be lower than the currently implemented bootstrapping-based testing approach in E3SM. We also evaluate the statistical power of the test using perturbed simulation ensemble suites, each with a progressively larger magnitude of change to a tuning parameter. The new test is generally found to exhibit more statistical power than the current approach, being able to detect smaller changes in parameter values with higher confidence.</p>
Alexandra Villa, Brittany N. Hupp, Nicolas M. Roberts
et al.
The attraction and retention of systemically marginalized students continues to be a major challenge in the geosciences. Despite a plethora of recruitment strategies by organizations including the National Science Foundation and systemically marginalized scientists themselves, there has not been significant progress in this arena. Furthermore, slow changes in the racial and ethnic diversity of the geoscience population have been accompanied by the less well-documented hostile experiences of systemically marginalized geoscientists. We argue that geoscience departments at academic institutions should ground their diversity, equity and inclusion (DEI) programming in a sustainable framework to build a community that is accountable for DEI. We showcase the effectiveness of this framework through a student-led group called GeoPath at a predominantly white, research-intensive institution in the USA. GeoPath is structured around (1) non-hierarchal leadership, (2) affirmation of individuals’ multiple identities, (3) recognition of and accounting for in-group v. out-group dynamics and (4) supporting a community mindset that was grounded in DEI education (scholarly literature, published statistics, evidence-based practices and lived experience of systemically marginalized people). Through the GeoPath approach, we have identified barriers that the geoscience community faces and which can be grouped into four themes. Additionally, we present a set of tailored DEI initiatives to educate the community on how to address these barriers. We assessed the effectiveness of these initiatives through a survey of the geosciences department community and found that over 85% of survey respondents felt a greater sense of community within the department and 95% agreed that they were better informed in the various challenges and barriers community members faced. With this newfound knowledge, the departmental community began creating and implementing their own DEI initiatives, which we define as ‘community buy-in'. This contribution seeks to illustrate the efficacy of our GeoPath framework, with the hope that DEI working groups in geoscience departments will implement the GeoPath approach to build sustainable cultural changes that hold the community accountable for DEI, and ultimately result in the increased attraction and retention of valuable talent and perspectives from systemically marginalized students.
<p>This research aims, on the one hand, to carefully examine the teaching and learning activities of Earth Sciences in secondary schools, analyzing the adopted approach and the reorganization of program units, which serve as both the structural foundation and a guiding framework for this educational cycle. On the other hand, it is conducted within the scope of improving educational resources and incorporating Information and Communication Technologies (ICT). The objective is to propose solutions and recommendations for restructuring curricula, selecting relevant topics in existing programs, enhancing learning methods, increasing learner motivation, developing didactic materials, and fostering connections with the socio-professional environment.</p>
<p>We identified, at the end of this study, this teaching raises the question of its current place into curriculum and schoolbooks in terms of educational resources. A question concerning the relevance of this teaching's attractiveness, focusing on the objectives of each step in the teaching-learning process, the assets to be capitalized on, and the dysfunctions to overcome, while proposing alternatives and possible measures to enhance the effectiveness of learning. As a result, it may affect the motivation and interest of students in this discipline as recommended by the 2015–2030-Strategic Vision (CSEFRS, 2015).</p>
<p>Transit times and tortuosity for advective particles following water flow in a three-dimensional discrete fracture network with high-resolution representation of internal fracture heterogeneity in aperture is investigated using a numerical model with a stochastic Lagrangian transport framework. The fracture network properties are obtained from field measurements and data of a deep fractured rock formation in the Forsmark site in Sweden. Different assumptions for describing the variance and correlation length used for internal heterogeneity of fracture aperture fields are considered. It is shown that cases with strong variance and correlation length cause earlier first arrivals and delayed late arrivals, thereby extending the range of the transit time breakthrough distribution, compared to the assumption of constant fracture aperture. Also, the timing of peak mass arrival is delayed and its density is reduced. Furthermore, a strong correlation between transit time and tortuosity which occurs for early and bulk mass arrival is revealed, which breaks down for late mass arrival. Thereby two transport regimes are identified, where a first regime is mainly controlled by the network structure and exhibits strong correlation with tortuosity, and a second regime is mainly controlled by the fracture aperture heterogeneity and exhibits weak correlation with tortuosity.</p>
Understanding the full wave field is imperative for seismic data analysis, as the different components induce errors in the sensors. Recent development of rotational seismometers allows for detailed measurements of the wave field gradients. Providing additional information that was previously unattained. However, it is well-known from navigation solutions that rotational data requires proper processing to be physically meaningful. In this study, we focus on investigating and quantifying two errors affecting recording of rotations: 1) misorientation of sensor to local system called misorientation of rotations and 2) changing projection of the Earth's spin in the recordings - Earth spin leakage. Using 6-component datasets, including 3C translation and 3C rotation, from near-field events at the Kilauea Caldera in Hawai' i and the Mw 7.4 Hualien event on 2024-04-02, we find that the Earth spin leakage is negligible, while the misorientation of the rotations increases with ground motion amplitude, potentially becoming significant for large earthquakes in the near-field. While these errors do not significantly affect acceleration corrections in our dataset, they may be relevant for high-amplitudes or in highly sensitive applications. This work offers the first quantification of these errors in seismology and provides guidance for assessing the need for corrections in future studies.
<p>The Earth's ice sheets, including the Antarctic Ice Sheet (AIS), are critical tipping points in the climate system. In recent years, the potential future collapse has garnered increased attention due to its cascading effects, which could significantly alter global climate patterns and cause large-scale, long-lasting, and potentially irreversible changes within human timescales. This study investigates the large-scale response of the polar Southern Hemisphere (pSH; comprising the Southern Ocean and Antarctica (60–90° S)) to the geometric reduction in ice sheets to a reconstructed Late Pliocene (LP) extent and imposing increased greenhouse gas (GHG) forcing in the Earth System. Using the PRISM4D reconstruction, where ice sheets such as the West Antarctic Ice Sheet (WAIS) were significantly diminished, we conducted multi-centennial simulations with the EC-Earth3 model at atmospheric <span class="inline-formula">CO<sub>2</sub></span> concentrations of 280 and 400 <span class="inline-formula">ppmv</span>. The simulation performed with LP ice sheet extent leads to a 9.5 <span class="inline-formula">°C</span> rise in surface air temperature, approximately a 16 <span class="inline-formula">%</span> reduction in sea ice concentration (SIC) over Antarctica and the Southern Ocean. These changes far exceed those driven by <span class="inline-formula">CO<sub>2</sub></span> increase alone, which result in a 2.5 <span class="inline-formula">°C</span> warming and a 9.3 <span class="inline-formula">%</span> sea ice decline. Additionally, both experiments deduce there is a reversal in sea level pressure (SLP) polarity with respect to pre-industrial (PI) patterns. Higher-than-normal SLP is present over Antarctica, and lower-than-normal SLP is present in the mid-latitudes, indicative of a negative phase of the Southern Annular Mode (SAM). This is supported by a weakening of the westerly jet, which in turn contributes to the formation of a fresh cap in the upper ocean, induced by the imposed climatic impacts of our sensitivity experiments. This overall freshening of the upper ocean increases stratification in the water column and prevents deep convection in the Southern Ocean, thus leading to the formation of the Antarctic Bottom Water (AABW), which is paramount for the ventilation of the global ocean. Overall, our findings suggest that, by increasing the atmospheric concentration of <span class="inline-formula">CO<sub>2</sub></span>, the AABW is suppressed at a multi-centennial timescale; however, by reducing the ice sheet extent, compensatory mechanisms, involving an extensive salinisation of the ocean interior, trigger partial recovery of this water mass. This emphasises the non-linearity of the climate system, since consequences of reducing the ice sheets induce an amplified warming and freshening in the near-surface, whereas they induce opposing mechanisms in the deep ocean that significantly alter the dynamics of water masses that feed the AABW. By isolating the climatic response to ice sheet extent reduction, whilst holding other parameters fixed, this study offers critical insights into the mechanisms driving atmospheric and oceanic variability around Antarctica and their broader implications for global climate dynamics. Here we provide a unique, targeted approach, specifically focusing on the direct impact of ice sheet retreat on regional climate.</p>
Laura Parisi, Nico Augustin, Daniele Trippanera
et al.
In the last decades, the slow-spreading Red Sea rift has been the objective of several geophysical investigations to study the extension of the oceanic crust, the thickness of the sedimentary cover, and the formation of transform faults. However, local seismology datasets are still lacking despite their potential to contribute to the understanding of the tectonic evolution of the Red Sea. The Zabargad Fracture Zone is located in the Northern Red Sea and significantly offsets the rift axis to the East. Thus, it is considered a key tectonic element to understand better the formation of the Red Sea rift. To fill the gap in the dataset availability, we deployed the first passive seismic network in the Red Sea, within the Zabargad Fracture Zone. This network included 12 Lobster OBSs from the DEPAS pool, 2 OBS developed and deployed by Fugro, and 4 portable seismic land stations deployed on islands and onshore on the Saudi Arabian coast. Our data-quality analysis confirms that the head-buoy cable free to strum, as well as other additional elements of the DEPAS OBSs, generate seismic noise at frequencies $>$ 10 Hz. However, the Fugro OBSs show high-frequency disturbances even if they lack vibrating elements. Comparison between land and OBS stations reveals that noise between 1 and 10 Hz is due to ocean-generated seismic noise, and not due to resonance of the OBS elements. We also found that waveforms of teleseismic earthquakes recorded by the Fugro OBSs, islands, and onshore stations have comparable signal-to-noise ratios. Instead, differences in signal-to-noise ratio for local earthquakes are affected more by site and path effects than instrument settings.
Nadezhda G. Razjigaeva, Larisa A. Ganzey, Tatiana A. Grebennikova
et al.
The distribution of tsunami deposits in the lacustrine-swamp sections on the Kasatka Bay coast is
analyzed. The main objects were a swamp formed on the place of overgrown lagoon-type lake located behind
dune ridge, and a low swampy isthmus between Oktyabrskoe and Srednee lakes. Five major events have been
identified, run-up parameters and age have been determined on the base of radiocarbon dating and
tephrostratigraphy. Diatom analysis data were used to confirm the marine origin of the sand. Established events
are correlated with data on adjacent islands and the Eastern Hokkaido coast. A trace of only one strong historical
tsunami was found, its deposits lie above marking volcanic ash Ta-a (1739) of the Tarumai Volcano, Hokkaido.
The tsunami took place in the second half of the 18th century. Perhaps this is a trace of 1780 AD tsunami, the
source was located near Urup Island. Four paleotsunamis are well compared in age with the megatsunamis of
the region (17th, 13th centuries, 1.5; 2.3–2.4 ka), which most clearly manifested on the Eastern Hokkaido coasts
and left sea sands and silts sheets in marshes of the Lesser Kuril Ridge and Kunashir Island. On Iturup, the
thickness of tsunami deposits and wide of sand cover is much less. It has been suggested that the peat section
of Iturup recorded the run-up values in the distal zone of the Late Holocene megatsunami, which had sources in
the southernmost of the Kuril-Kamchatka Trench. Regional strong tsunamis occurred in the period of instrumental
observations did not leave geological evidence in the studied sections.
The use of cross-correlation between seismic stations has had widespread applications particularly in the exploitation of ambient seismic noise. We here show how the effects of a non-ideal noise distribution can be understood by looking directly at correlation properties and show how the behaviour can be readily visualised for both seismometer and DAS configurations, taking into account directivity effects. For sources lying in a relatively narrow cone around the extension of the inter-station path, the dispersion properties of the correlation relate directly to the zone between the stations. We illustrate the successful use of correlation analysis for both a large-N array perpendicular to a major highway and DAS cable along a busy road. For correlation work, the co-array consisting of the ensemble of inter-station vectors provides an effective means of assessing the behaviour of array layouts, supplementing the standard plane-wave array response. When combined with knowledge of the suitable correlation zones for noise sources, the co-array concept provides a useful way to design array configurations for both seismometer arrays and DAS.
<p>Stratospheric aerosol injection (SAI), as a possible supplement to emission reduction, has the potential to reduce some of the risks associated with climate change. Adding aerosols to the lower stratosphere would result in temporary global cooling. However, different choices for the aerosol injection latitude(s) and season(s) have been shown to lead to significant differences in regional surface climate, introducing a design aspect to SAI. Past research has shown that there are at least three independent degrees of freedom (DOFs) that can be used to simultaneously manage three different climate goals. Knowing how many more DOFs there are, and thus how many independent climate goals can be simultaneously managed, is essential to understanding fundamental limits of how well SAI might compensate for anthropogenic climate change, and evaluating any underlying trade-offs between different climate goals. Here, we quantify the number of meaningfully independent DOFs of the SAI design space. This number of meaningfully independent DOFs depends on both the amount of cooling and the climate variables used for quantifying the changes in surface climate. At low levels of global cooling, only a small set of injection choices yield detectably different surface climate responses. For a cooling level of 1–1.5 <span class="inline-formula"><sup>∘</sup></span>C, we find that there are likely between six and eight meaningfully independent DOFs. This narrows down the range of available DOFs and also reveals new opportunities for exploring alternate SAI designs with different distributions of climate impacts.</p>
<p>Step-pool systems are common bedforms in mountain streams and have been utilized in river restoration projects around the world. Step-pool units
exhibit highly nonuniform hydraulic characteristics which have been reported to closely interact with the morphological evolution and stability of
step-pool features. However, detailed information on the three-dimensional hydraulics for step-pool morphology has been scarce due to the difficulty
of measurement. To fill in this knowledge gap, we established a combined approach based on the technologies of structure from motion (SfM) and
computational fluid dynamics (CFD). 3D reconstructions of bed surfaces with an artificial step-pool unit built from natural stones at six flow rates
were imported to CFD simulations. The combined approach succeeded in visualizing the high-resolution 3D flow structures for the step-pool unit. The
results illustrate the segmentation of flow velocity downstream of the step, i.e., the integral recirculation cell at the water surface, streamwise
vortices formed at the step toe, and high-speed flow in between. The highly nonuniform distribution of turbulence energy in the pool has been
revealed, and two energy dissipaters of comparable magnitude are found to co-exist in the pool. Pool scour development during flow increase leads to
the expansion of recirculation cells in the pool, but this expansion stops for the cell near the water surface when flow approaches the critical
value for step-pool failure. The micro-bedforms (grain clusters) developed on the negative slope affect the local hydraulics significantly, but this
influence is suppressed at the pool bottom. The drag forces on the step stones increase with discharge (before the highest flow value is
reached). In comparison, the lift force consistently has a larger magnitude and a more widely varying range. Our results highlight the feasibility and great
potential of the approach combining physical and numerical modeling in investigating the complex flow characteristics of step-pool morphology.</p>
N. Wunderling, N. Wunderling, N. Wunderling
et al.
<p>With progressing global warming, there is an increased risk that one or several tipping elements in the climate system might cross a critical threshold, resulting in severe consequences for the global climate, ecosystems and human societies. While the underlying processes are fairly well-understood, it is unclear how their interactions might impact the overall stability of the Earth's climate system. As of yet, this cannot be fully analysed with state-of-the-art Earth system models due to computational constraints as well as some missing and uncertain process representations of certain tipping elements. Here, we explicitly study the effects of known physical interactions among the Greenland and West Antarctic ice sheets, the Atlantic Meridional Overturning Circulation (AMOC) and the Amazon rainforest using a conceptual network approach. We analyse the risk of domino effects being triggered by each of the individual tipping elements under global warming in equilibrium experiments. In these experiments, we propagate the uncertainties in critical temperature thresholds, interaction strengths and interaction structure via large ensembles of simulations in a Monte Carlo approach. Overall, we find that the interactions tend to destabilise the network of tipping elements. Furthermore, our analysis reveals the qualitative role of each of the four tipping elements within the network, showing that the polar ice sheets on Greenland and West Antarctica are oftentimes the initiators of tipping cascades, while the AMOC acts as a mediator transmitting cascades. This indicates that the ice sheets, which are already at risk of transgressing their temperature thresholds within the Paris range of 1.5 to 2 <span class="inline-formula"><sup>∘</sup></span>C, are of particular importance for the stability of the climate system as a whole.</p>
<p>As part of the GEMex Project, an on-going European-Mexican effort to develop
geothermal energy from non-conventional sources, preliminary geological
models have been constructed for two sites located in the easternmost region
of the Trans-Mexican Volcanic Belt. The first site, Los Humeros, which has
produced geothermal electricity for decades, is investigated for its probable
superhot geothermal resources. The second site, Acoculco, is a less known but
promising area where application of an Enhanced Geothermal System is being
studied. In order to have a coherent geological interpretation of both sites,
preliminary 3-D models were constructed in a collaborative manner by European
and Mexican partners. These models are based on data available at the start
of the project, including geological maps, cross-sections and well logs. The
data were mainly provided by the Comisión Federal de Electricidad (CFE),
and the Mexican Centre for Innovation in Geothermal Energy (CeMIE-Geo
consortium). A regional model was developed for each site and an additional
local model was constructed for Los Humeros. The preliminary geological
models serve as a framework for GEMex work on heat-transport and fluid-flow
simulations; they will be updated and refined during the project, using new
data and interpretations from ongoing and future field work on geology,
geophysics, and geochemistry.</p>
River discharges from Siberia are a large source of freshwater into the
Arctic Ocean, whereas the cause of the long-term variation in Siberian
discharges is still unclear. The observed river discharges of the Lena in the
east and the Ob in the west indicated different relationships in each of the
epochs during the past 7 decades. The correlations between the two river
discharges were negative during the 1980s to mid-1990s, positive during the
mid-1950s to 1960s, and became weak after the mid-1990s. More long-term
records of tree-ring-reconstructed discharges have also shown differences in
the correlations in each of the epochs. It is noteworthy that the
correlations obtained from the reconstructions tend to be negative during the
past 2 centuries. Such tendency has also been obtained from precipitations
in observations, and in simulations with an atmospheric general circulation
model (AGCM) and fully coupled atmosphere–ocean GCMs conducted for the
Fourth Assessment Report of the IPCC. The AGCM control simulation further
demonstrated that an east–west seesaw pattern of summertime large-scale
atmospheric circulation frequently emerges over Siberia as an atmospheric
internal variability. This results in an opposite anomaly of precipitation
over the Lena and Ob and the negative correlation. Consequently, the
summertime atmospheric internal variability in the east–west seesaw pattern over
Siberia is a key factor influencing the long-term variation in precipitation
and river discharge, i.e., the water cycle in this region.
A clear understanding of erosion processes is fundamental in order to comprehend the
evolution of actively deforming mountain ranges. However, the relative contributions
of tectonic and climatic factors and their feedbacks remain highly debated. In order to contribute to the debate, we quantify basin-wide
denudation rates from cosmogenic <sup>10</sup>Be concentrations in modern river
sediments in the Pamir. This mountain range is a unique natural laboratory
because the ongoing India–Eurasia collision sustains high deformation rates
and, on account of its position at the transition between Westerlies and
monsoon, a strong regional climatic variability arises. Sample acquisition
and preparation for accelerator mass spectrometry measurements were
challenging due to difficult field accessibility, low quartz and high feldspar
concentrations and crystal coating. Six samples along the main
draining river, the Panj, and five samples within the major, east–west
elongated tributary basins allow us to quantify basin-wide denudation rates
for the first time in this orogen. An average denudation rate of
~ 0.64 mm yr<sup>−1</sup> reveals a rapid evolution of the entire Pamir. Denudation
rates of tributary sub-basins highlight the strong contrast between the Pamir
Plateau (0.05 to 0.16 mm yr<sup>−1</sup>) and its margins (0.54 to
1.45 mm yr<sup>−1</sup>). The intensity of denudation is primarily correlated
with geometric properties of the surface, such as slope steepness (0.75 quartiles;
<i>R</i><sup>2</sup> of 0.81), and to a lesser extent to climatic factors such as
precipitation. We thus argue that either tectonic uplift or base-level
lowering are the main contributors to denudation processes. Multiple linear
regression analysis (best <i>R</i><sup>2</sup> of 0.93) suggests that precipitation may
act as a limiting factor to denudation. The highest denudation rates coincide
with areas of the northwestern Pamir margin that receive precipitation
predominantly from the Westerlies during winter. There, the concentrated
discharge during spring and early summer may sustain the pronounced
denudation and allow the rapid sediment transport out of the basins. Low
slope angles and dry conditions hamper the sediment flux on the
plateau and, consequently, denudation. The magnitude of denudation in the
Pamir is similar to rates determined in the southern Himalaya despite very
different climatic and tectonic conditions. The discrepancy between rates of
basin-wide denudation and the fluvial incision that is up to 10 times higher evidences a transient landscape in the Pamir. This underpins the hypothesis
that river captures may have caused the strong base-level lowering that drives the enhanced incision of the Panj and its main tributaries.
Emission metrics are used to compare the climate effect of the emission of
different species, such as carbon dioxide (CO<sub>2</sub>) and methane (CH<sub>4</sub>).
The most common metrics use linear impulse response functions (IRFs)
derived from a single more complex model. There is currently little
understanding on how IRFs vary across models, and how the model variation
propagates into the metric values.
<br><br>
In this study, we first derive CO<sub>2</sub> and temperature IRFs for a large
number of complex models participating in different intercomparison
exercises, synthesizing the results in distributions representing the variety
in behaviour. The derived IRF distributions differ considerably, which is
partially related to differences among the underlying models, and partially
to the specificity of the scenarios used (experimental setup).
<br><br>
In a second part of the study, we investigate how differences among the IRFs
impact the estimates of global warming potential (GWP), global temperature
change potential (GTP) and integrated global temperature change potential
(iGTP) for time horizons between 20 and 500 yr.
<br><br>
Within each derived CO<sub>2</sub> IRF distribution, underlying model
differences give similar spreads on the metrics in the range of −20 to
+40% (5–95% spread), and these spreads are similar among the three
metrics.
<br><br>
GTP and iGTP metrics are also impacted by variation in the temperature IRF.
For GTP, this impact depends strongly on the lifetime of the species and the
time horizon. The GTP of black carbon shows spreads of up to −60 to +80% for
time horizons to 100 yr, and even larger spreads for longer time horizons.
For CH<sub>4</sub> the impact from variation in the temperature IRF is still
large, but it becomes smaller for longer-lived species. The impact from
variation in the temperature IRF on iGTP is small and falls within a range of
±10% for all species and time horizons considered here.
<br><br>
We have used the available data to estimate the IRFs, but we suggest the use
of tailored intercomparison projects specific for IRFs in emission metrics.
Intercomparison projects are an effective means to derive an IRF and its
model spread for use in metrics, but more detailed analysis is required to
explore a wider range of uncertainties. Further work can reveal which
parameters in each IRF lead to the largest uncertainties, and this
information may be used to reduce the uncertainty in metric values.
Early warning signals (EWS) have become a popular statistical tool to infer stability properties of the climate system. In Part 1 of this two-part paper we have presented a diagnostic method to find the hotspot of a sudden transition as opposed to regions that experience an externally induced tipping as a mere response. Here, we apply our method to the atmosphere–vegetation model PlanetSimulator (PlaSim) – VECODE using a regression model. For each of two vegetation collapses in PlaSim-VECODE, we identify a hotspot of one particular grid cell. We demonstrate with additional experiments that the detected hotspots are indeed a particularly sensitive region in the model and give a physical explanation for these results. The method can thus provide information on the causality of sudden transitions and may help to improve the knowledge on the vulnerability of certain subsystems in climate models.