There has been increasing interest in the possibility of abrupt climatic changes in the North Atlantic and their potential impacts on the downstream regions of northwestern Europe. Here, we investigate whether this system undergoes abrupt change in a large ensemble of CMIP6 climate models. We define two metrics based on subpolar sea surface temperatures (SSTs) or mixed layer depths (MLDs) to explore the link between surface temperatures and convection collapse. These metrics yield similar numbers of abrupt events but represent seemingly unrelated phenomena. Abrupt MLD changes appear related to ongoing warming. Abrupt SST changes follow a pattern of decadal timescale cooling and warming related to coupled dynamics involving the NAO. Constraining the models by their representation of NAO variability increases the estimated likelihood of an abrupt SST event from 15% to 29%. Both the cooling and warming phases have important implications for impacts and adaptation, particularly over the British Isles.

VOC compounds-carcinogenic substances for which the EPA has set no safe threshold-are prevalent and persistent aerosol pollutants. Regulation at the source is ideal but not sufficient. Our work starts with a local solution at the conjunction of urban topography and aerosol pollution. Mitigation at the source, as per CARB's banning of MTBE in 2002, and perchloroethylene starting in 2007, is productive. However, what works in suburban California does not work in the dense cities of the global South. In context of the world's more prevalent urban topography, this is not enough. EPA NESHAPs Standards for Hazardous Air Pollutants; 1970 with a major revision in 1989. CARB Gasoline and other TAC Regulations Banning of MTBE additives, toxic hotspot inventories, banning perc. EU Legislation for VOCs Enhanced monitoring of benzene and other VOCs.

A document by Tomohiro Takagawa. Click on the document to view its contents.

A document by Julia G Mason. Click on the document to view its contents.

Marine carbon dioxide removal (mCDR) and geological carbon storage in the marine environment (mCS) promise to contribute to the mitigation of global climate change in combination with drastic emission reductions. However, the implementable potential of mCDR and mCS depends, apart from technology readiness, also on site-specific conditions. In this paper, we explore different options for mCDR and mCS, using the German context as a case study. We challenge each option to remove 10 Mt CO2 yr-1, which accounts for 8-22% of projected hard-to-abate and residual emissions of Germany in 2045. We focus on the environmental, resource, and infrastructure requirements of individual mCDR and mCS options at a specific site, within the German jurisdiction when possible. Furthermore, we discuss main uncertainty factors and research needs, and, where possible, cost estimates, expected environmental effects, and monitoring approaches. In total, we describe ten mCDR and mCS options; four aim at enhancing the chemical carbon uptake of the ocean through alkalinity enhancement, four aim at enhancing blue carbon ecosystems’ sink capacity, and two employ geological off-shore storage. Our results indicate that five out of ten options would potentially be implementable within German jurisdiction, and three of them could potentially rise to the challenge. This exercise provides a basis for further studies to assess the socio-economic, ethical, political, and legal aspects for such implementations.

Oceanic stratification plays a key role in climate by modulating the ocean’s resistance to be mixed vertically. It has been traditionally assumed that, beyond the deepest reach of winter mixing, stratification is relatively invariant on the time scales of contemporary climate evolution. Here, we test this view by performing a global investigation of the spatio-temporal variability of stratification from the surface to the main pycnocline, using 20 years (2003-2022) of data from the Argo float array. Both near-surface and main pycnocline stratifications are found to exhibit spatially-structured, vertically-coherent, global-scale variations on seasonal-to-decadal time scales, suggesting that both stratifications are a rapidly-evolving, readily-interactive component of the climate system. Variability in stratification is organized into well-defined patterns that replicate the spatial footprints and time scales of major climate modes, pointing to these modes of internal variability as important drivers of stratification changes. Our diagnosed patterns and forcings of stratification variability provide an important benchmark for advancing the climate models used to understand and predict the ongoing climate change

In this paper, based on the electric field data (EFD) of the China Seismo-Electromagnetic Satellite (CSES), which is divided into 4 frequency bands (ULF, ELF, VLF, HF) from DC to 3.5 MHz, we study the impact characteristics of the 4 November 2021 magnetic storm activity in different frequency bands. It was found that the electric field anomalies caused by magnetic storms were mainly concentrated below 18 kHz, and above 18 kHz the effects were weak and gradually diminished to negligible. In the ULF band, excluding the influence of Schumann waves, the electric field anomalies caused by magnetic storms are mainly below 5 Hz, with the most influential frequency point being 3.4 Hz. In the ELF band, the more obvious anomalies appear at 300 Hz – 900 Hz and above 1.8 kHz, with the most significant anomalies in the 300 Hz – 900 Hz band around 780 Hz. In the VLF band, electric field anomalies are concentrated in 2.5 - 10 kHz. Magnetic storms had essentially no effect on the HF band. Magnetic storms at low and middle latitudes have a weak effect on the ELF and VLF bands and are more pronounced in the ULF band. During the main phase of the magnetic storm, the absolute magnitude of variance change in the ELF and VLF bands is greater than that in the ULF band as a whole, but the relative magnitude of variance change in the ULF band is 10% greater than that in the ELF and VLF bands.

This study proposes a new global-scale lightning model, predicting lightning rates from large-scale climatic variables. Using satellite lightning records spanning a period of 29 years, we apply machine learning methods to derive a functional relationship between lightning and climate reanalysis data. In particular, we design a model tree, representing different lightning regimes with separate single hidden layer neural networks of low dimensionality. We apply multiple complexity constraints in the model development stages, which makes the lightning model straightforward to implement as a lightning scheme for global climate models (GCMs). We demonstrate that, for years not used for model training, our lightning model captures 70.6% of the daily global spatio-temporal lightning variability, which corresponds to a >42% relative improvement compared to well-established lightning schemes. Similarly, the model correlates well with lightning observations for the monthly climatology (r>0.92), inter-annual variability (r>0.90), and latitudinal and longitudinal distributions (r>0.86). Most notably, the model brings a critical improvement in representing lightning magnitude and variability in the three tropical lightning chimney regions: central Africa, the Amazon, and the Maritime Continent. We implement the lightning model in the Community Earth System Model to verify its stability and performance as a GCM component, and we provide detailed implementation guidelines. As an intermediate approach between high-dimensional machine learning models and first-order lightning parameterizations, our model offers GCMs a straightforward and efficient tool to improve lightning simulation, which is critical for representing atmospheric chemistry and naturally-ignited wildfires.

Fa Li1,*, Qing Zhu2, Kunxiaojia Yuan2, Fujiang Ji1, Arindam Paul3, Peng Lee3, Volker C. Radeloff1, Min Chen1,*1Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI, USA2Climate and Ecosystem Sciences Division, Climate Sciences Department, Lawrence Berkeley National Laboratory, Berkeley, CA, USA3America Family Insurance*Corresponding authors: Fa Li ([email protected]) and Min Chen ([email protected])

Prior to the present study, no dedicated in situ measurement of the thickness distributions of fast ice and the sub-ice platelet layer, formed by supercooled Ice Shelf Water in the near-surface ocean, had been carried out in Terra Nova Bay. Previous studies have recognised the biological importance of the sub-ice platelet layer observed beneath fast ice beside the Campbell Ice Tongue. Furthermore, a recent airborne survey of fast ice in the western Ross Sea implied that smaller ice bodies (ice tongues and outlet glaciers) contribute to the formation of supercooled Ice Shelf Water. With the objective of inferring source regions and circulation of Ice Shelf Water, we measured fast ice and sub-ice platelet layer thickness distributions near the Campbell Ice Tongue in late spring of 2021, using drill hole surveys and high-resolution ground-based electromagnetic induction soundings. We observed thicker fast ice and sub-ice platelet layer near the ice tongue with very thick and narrow sub-ice platelet layer maxima identifying highly channelled outflow of supercooled Ice Shelf Water from beneath the ice tongue through ice mélange, subglacial formations, and grounded regions. We conclude that a significant volume of supercooled Ice Shelf Water is locally sourced from the Campbell Ice Tongue through basal melting and affirm that the icescape in north Terra Nova Bay results from a complex interplay of glacial morphology, bathymetry, polynya dynamics, and ocean circulation.

Thirty years (1993-2022) of concurrent satellite and in-situ observations show a long-term strengthening of the equatorial Pacific upper-ocean circulation. Enhanced southeasterly and cross-equatorial winds have caused an annual mean, basin-wide acceleration of the equatorial westward near-surface currents by ~20% and an acceleration of poleward flow north (south) of the equator by ~60% (~20%). Additional moored velocity data reveal a deepening of the EUC core at 170°W and significant shoaling at 140°W and 110°W, but no significant changes in EUC core velocity. The strongest subsurface zonal velocity trends are observed above the EUC core and occur before and after the seasonal maximum of EUC core velocity, causing enhanced upper-ocean vertical current shear. Consistent with trends of the 20°C isotherm depth along the equatorial Pacific, a significant basin-wide steepening of the equatorial thermocline is observed. Both the accelerating equatorial current system and the enhanced thermocline slope are consistent with an observed steepening of the zonal sea surface height gradient due to increased wind-driven westward mass transport at the surface. During February-March, both surface and subsurface currents show eastward velocity trends, in contrast to westward near-surface current trends during the remainder of the year. The trend reversal is attributed to both a long-term shift in equatorial Kelvin wave activity and to the impact of strong interannual variability due to El Niño Southern Oscillation and other modes of natural variability on decadal to multidecadal time scales.

In this paper, the importance of model horizontal resolution in identifying the nature of mixing and dispersion is investigated by comparing two data-assimilative, high-resolution simulations (4km and 1km), one of which is submesoscale-resolving. By employing both Eulerian and Lagrangian metrics, upper-ocean differences between the mesoscale- and submesoscale-resolving simulations are examined in the northeastern Gulf of Mexico, a region of high mesoscale and submesoscale activity. The nature of mixing in both simulations is identified by conducting Lagrangian experiments to track the generation of Lagrangian Coherent Structures (LCSs) and their associated transport barriers. Finite-time Lyapunov exponents (FTLE) fields show higher separation rates of fluid particles in the submesoscale-resolving case which indicate more vigorous mixing, with differences being more pronounced in the shelf regions (depths<=500m). The extent of the mixing homogeneity is examined by using probability density functions (PDFs) with results suggesting that mixing is heterogeneous in both simulations, but some homogeneity is exhibited in the submesoscale-resolving case. The FTLE fields also indicate that chaotic stirring dominates turbulent mixing in both simulations regardless of the horizontal resolution. In the submesoscale-resolving experiment, however, smaller scale LCSs emerge as noise-like filaments that suggest a larger turbulent mixing component than in the mesoscale-resolving experiment. The impact of resolution is then explored by investigating the spread of oil particles at the location of the Deepwater Horizon oil spill.

Anthropogenic land use and land cover change (LULCC), is projected to continue in the future. However, the influence of forest management on forest productivity change and subsequent LULCC projections remain under-investigated. This study explored the impacts of forest management-induced change in forest productivity on LULCC throughout the 21st century. Specifically, we developed a framework to softly couple the Global Change Analysis Model and Global Timber Model to consider forest management-induced forest productivity change, and projected future LULCC across the five Shared Socioeconomic Pathways (SSPs). We found future increases in forest management intensity overall drive the increase of forest productivity. The forest management-induced forest productivity change shows diverse responses across all SSPs, with a global increase from 2015 to 2100 ranging from 3.9% (SSP3) to 8.8% (SSP1). This further leads to an overall decrease in the total area with change of land use types, with the largest decrease under SSP1 (-7.5%) and smallest decrease under SSP3 (-0.7%) in 2100. Among land use types, considering forest management-induced change significantly reduces the expansion of managed forest, and also reduces the loss in natural land in 2100 across SSPs. This suggests that ignoring forest management-induced forest productivity change underestimates the efficiency of wood production, overestimates the managed forest expansion required to meet the future demand, and consequently, potentially introduces uncertainties into relevant analyses, e.g., carbon cycle and biodiversity. Thus, we advocate to better account for the impacts of forest management in future LULCC projections.

The Irpinia region is one of the most seismically active areas of Italy due to ongoing, late-orogenic extension in the axial zone of the Apennines mountain belt. However, the 3D architecture and the nature of the faults that drive this extension are still uncertain, posing challenges to seismic hazard assessment. Here, we address these uncertainties by integrating a new catalog of high-resolution micro-seismicity (ML<3.5) complemented by earthquake focal mechanisms, with existing 3D seismic velocity models and geological data. We found that micro-seismicity is primarily taking place along a segmented, approximately 60 km long, deep-seated, Mesozoic normal fault that was inverted during the shortening stages of the Apennine orogeny and then extensionally reactivated during the Quaternary. These findings suggest that multiple events of reactivation of long-lived faults can weaken their strength, making them prone to co-seismic remobilization under newly-imposed strain fields in active mountain belts.

Fluvial deltas have worldwide socio-economic importance as human development and infrastructure centers and provide several ecosystem services, including storm protection and nursery habitats. Their subsurface architecture also holds clues to past climate and sea-level change that can be reconstructed from stratigraphy. A significant challenge in inverting stratigraphy is separating the signals of external forcing, such as variations in sea level, and internal processes, such as the dynamics of the fluvial surface and channel network variations. In a previous work, we analyzed laboratory flume data from the Tulane Delta Basin using an experimental run with oscillating sea level conditions and constant sediment supply. We found that the dynamics of the fluvial surface play an important role in delaying the response of the upper portion of the subaerial topset. To further quantify this phenomenon, we couple this flume experiment with a numerical modeling framework that integrates the topset with a subaqueous offshore region or foreset. The numerical model can explain the topset slope, convexity dynamics, and sediment partitioning between the topset and the foreset under sea level variations. For example, it captures how during sea-level rise (SLR), low sedimentation near the topset's center reduces the subaerial slope and increases convexity, while during sea-level fall (SLF), high sedimentation increases the slope and concavity. Moreover, the model can explain the counterintuitive observation of higher sediment topset bypass to the foreset under SLR than SLF due to the reduction in subaerial slope, partially explained by a higher presence of active channels during SLR than SLF. These results underscore the importance of internal processes such as fluvial surface and channel dynamics, which can result in net erosion during SLR and net deposition during SLF, potentially complicating the reconstruction of paleo sea-level from deltaic deposits.

A document by Rachel Atlas. Click on the document to view its contents.

Production and use of halocarbons (halogenated hydrocarbons) saw explosive growth after the Second World War for use as refrigerants (including air conditioning and industrial refrigeration), solvents, and aerosol propellants. Within decades after their mass introduction, they were implicated in the destruction of Earth's protective ozone layer, concerns over which prompted an international effort to phase out largescale use of the most problematic halocarbon classes, namely chlorofluorocarbons (or CFCs) and hydrochlorofluorocarbons (or HCFCs), under the Montréal Protocol. However, the non-chlorinated hydrofluorocarbon (or HFC) alternatives that were developed to replace CFCs and HCFCs have proved to be exceptionally effective greenhouse agents and historically have been underreported in the ongoing discussions around climate change mitigation. Recent concerns gathering around their increasing abundance in the atmosphere have prompted increased government scrutiny and regulation, resulting in the 2016 Kigali Amendment to the Montréal Protocol recently ratified by the United States. Despite the concerted international effort currently underway to curtail the manufacture and consumption of the most environmentally impactful halocarbons, there have been several reports concerning discrepancies between measured atmospheric abundances and reported inventories of select halocarbon species that have defied expectations.

The scientific debate on the existence of possible precursors before large earthquakes has been wide and brought to not univocal conclusions. One observable alone is clearly insufficient to provide indications on the criticality of the seismic fault status. In particular, it’s fundamental to investigate how critical is the accumulation of stress on a seismogenic fault and how we can predict an incoming earthquake. Considering that the Earth is a complex system in which the geo-layers (lithosphere, atmosphere and ionosphere) interact, it seems possible to understand better the Earth’s system if we study it as a whole. This requires an integration of observations and data from several sources and instruments, from ground data to remote sensing satellites. Despite the technical obstacles, several works have been done in this direction in the last years, and they seem to confirm firstly that the geo-layers show alterations (i.e., anomalies) before earthquake occurrence; secondly, it seems that several mechanisms of coupling are possible. This last point is the present research topic, as further clarifications are required.In the presentation, several examples of couplings before the earthquakes will be shown; for example, the recent investigation of the Lushan (China) 2013 earthquake, which shows three possible couplings by different geophysical mechanisms at very different times before the earthquake (130 days, 45 days, and 2 weeks).For the more recent seismic event, it is possible to investigate the ionosphere layer with the precious data from China Seismo Electromagnetic Satellite (CSES-01), by its instruments such as Langmuir probes and magnetometers. The integration of CSES and ESA Swarm data allows us to define better the ionospheric disturbances possibly related to earthquake occurrence. These cases include Mw = 7.5 Indonesia 2018, Mw = 7.6 Papua New Guinea 2019, Mw = 7.7 Jamaica 2020 or Mw = 7.8 Turkey 2023 earthquakes.Finally, we are still far from predicting earthquakes but several steps toward a better understanding of the phenomena eventually associated with seismic events seem to be not far.