The properties of the solar wind represent a mixture of indicators for solar origin and transport effects. Both are of interest for the understanding of heliophysics and space weather effects. Most available solar wind classifications focus on the solar origin, in part based on transport effected properties. We aim to identify the solar wind properties that are most important for solar wind classification. We select seven solar wind properties: proton density, proton speed, proton temperature, absolute magnetic field strength, proton-proton collisional age, the ratio between the densities of O6+ and O7+ and the mean charge state of Fe. We apply an unsupervised machine learning method, k-means, to each subset of the these parameters and compare the results to a reference case based on all seven solar wind properties. Two scenarios are considered which provide a simple and a detailed solar wind classification, respectively. We identified the proton density as the most important solar wind property for solar wind classification. Furthermore, we found that charge state composition is important to accurately identify the solar source region. This holds for the simple case of three solar wind types but is even more important for a more detailed classification. In comparison to proton density and proton temperature, the solar wind speed turns out to be a less influential property. Our results underscore the importance of highly accurate measurements, in particular for proton density, proton temperature and the charge state composition.

Over the last ten years, satellite and geographically constrained in situ observations largely focused on the northern hemisphere have suggested that annual phytoplankton biomass cycles in bloom-forming ocean regions cannot be fully understood from environmental properties controlling phytoplankton division rates (e.g., nutrients and light). Here, we use multi-year observations from a very large array of robotic drifting buoys in the Southern Ocean to determine key factors governing phytoplankton biomass dynamics over the annual cycle. Our analysis reveals phytoplankton blooming events occurring during periods of declining division rates, an observation that clearly highlights the importance of changing loss processes in dictating the evolution of the bloom. Bloom magnitude is found to be greatest in areas with high dissolved iron concentrations, consistent with iron being a well-established primary limiting nutrient in the Southern Ocean. Projections for expected future seasonal variations in nutrient and light availability indicate a 10% change in phytoplankton division rate may be associated with a 50% reduction in mean bloom magnitude and annual primary productivity in the Southern Ocean. Our results highlight the importance of quantifying and accounting for both changing phytoplankton division and loss processes when modeling future changes in phytoplankton bloom cycles.

For the first time in 2015, four dedicated hydrographic cruises – one in each season – took place around the Canary Islands to determinate the seasonality of the flows at the eastern boundary of the North Atlantic Subtropical Gyre. The Canary Current (CC) is the eastern boundary current of the North Atlantic Subtropical Gyre and links the Azores Current with the North Equatorial Current. The CC shows a seasonal behavior in its path and strength, flowing on its easternmost position in winter (3.4±0.3 Sv), through the Canary Islands in spring (2.1±0.7 Sv) and summer (2.0±0.6 Sv) and on its westernmost position in fall (3.2±0.4 Sv). At the Lanzarote Passage (LP), the dominant flow is southward except in fall, where a northward transport is observed at surface (1.1±0.3 Sv) and intermediate (1.3±0.2 Sv) layers. A historical composite observational seasonal cycle is built from all the available estimations on the area and fits the 2015 seasonal cycle. The LP seasonal cycle and seasonal amplitude match the seasonal cycle of the Atlantic Meridional Overturning Circulation (AMOC) measured by the RAPID-MOCHA data array.

A document by Zhenguang Huang. Click on the document to view its contents.

The primary data sources for reconstructing the geomagnetic field of the past millennia are archaeomagnetic and sedimentary paleomagnetic data. Sediment records, in particular, are crucial in extending the temporal and spatial coverage of global geomagnetic field models, especially when archaeomagnetic data is sparse. However, the post-depositional detrital remanent magnetization (pDRM) process is still poorly understood and can cause smoothing of the magnetic signal and offsets with respect to the sediment age. To make effective use of sedimentary data, it is essential to understand the lock-in process and its impact on the magnetic signal. In this study, we investigate the lock-in process theoretically and derive a parameterized lock-in function that can approximate possible lock-in behaviors. Additionally, we demonstrate that a lock-in function that is independent of absolute parameters can only be applied to the magnetic direction components (declination and inclination), but not to the relative intensity. Integrating this lock-in function into the ArchKalmag14k modeling procedure \cite{schanner2022archkalmag14k} allows including data from sediment records. The parameters of the lock-in function are estimated by the maximum likelihood method using archaeomagnetic data as a reference. The effectiveness of the proposed method is evaluated through synthetic tests. Additionally, we apply our technique to sediment records from two lakes in Sweden (Kälksjön and Gyltigesjön) as first case studies. Our results demonstrate that the proposed method is capable of effectively correcting the distortion caused by the lock-in process, making data from sedimentary records a more reliable and informative source for geomagnetic field reconstructions.

In continuous permafrost regions, pathways for transport of sub-permafrost groundwater to the surface sometimes perforate the frozen ground and result in the formation of a pingo. Explanations offered for the locations of such pathways have so far included hydraulically conductive geological units and faults. On Svalbard, several pingos locate at valley flanks where these controls are apparently lacking. Intrigued by this observation, we elucidated the geological setting around such a pingo with electrical resistivity tomography. The inverted resistivity models showed a considerable contrast between the uphill and valley-sides of the pingo. We conclude that this contrast reflects a geological boundary between low-permeable marine sediments and consolidated strata. Groundwater presumably flows towards the pingo spring through glacially induced fractures in the strata immediately below the marine sediments. Our finding suggests that flanks of uplifted Arctic valleys deserve attention as possible discharge locations for deep groundwater and greenhouse gasses to the surface.

Coastal wetlands provide a livelihood for local communities and simultaneously provide services that include coastal protection, enhanced carbon storage and habitats provision for both terrestrial- and marine life. Yet, the development of climate resilient management strategies that need to account for changes that might occur in the coming decades is challenging due to the variable response of coastal ecosystems. This is because coastal ecosystems, including mangroves, wetlands and tidal flats, are directly linked to coastline dynamics, as coastlines can move seaward, when waves are low and sediment availability is high, or retreat when the opposite is true. Particularly the long-term fate of the mud dominated coastline of Suriname, part of the Guianas coastal system stretching from the Amazon to the Orinoco delta, is determined by migrating subtidal mudbanks that cause a cyclic instability of alternating erosion and progradation phases. We present a semi-automatic remote sensing approach to quantify the influence of mudbank migration on coastline dynamics along the entire coast of Suriname. We validated our approach with high resolution drone imagery collected at contrasting locations, indicating average accuracy of changes in coastline position to be within 50 meters. This suggest we can apply our methodology on all available Landsat images between 1985 and 2020, acquired over the heterogonous and complex coastal landscapes. The results show that regional forcing mechanisms, related to migration of six to eight subtidal mudbanks in front of the Suriname coast, have a strong imprint on local coastline dynamics with an average 25 m/yr-1 expansion during mudbank presence, and 8 m/yr-1 retreat of the coastline during mudbank absence between 1986 and 2020. More importantly, we found that not all spatial and temporal variations in the magnitude and timing of local changes can be explained by migrating mudbanks. This demonstrates the importance of incorporating changes that cannot be explained by regional forcing mechanisms in management frameworks that aim at explaining current variability and predicting future coastline changes.

Researcher Ridge (RR) is a 400km long, WNW-ESE oriented chain of volcanic seamounts, located on ~20 to 40 Ma old oceanic crust on the western flank of the Mid-Atlantic Ridge (MAR) at ~15°N. RR remained nearly unstudied, and thus its age and origin are currently unclear. At roughly the same latitude, the MAR axis is bathymetrically elevated and produces geochemically enriched lavas (the well-known 14°N MAR anomaly). This study presents 40Ar/39Ar age data, major and trace elements, and Sr-Nd-Pb-Hf isotopic compositions of volcanic rocks dredged from several seamounts of the RR and along the MAR between 13-14°N. The results reveal that RR lavas have geochemically enriched ocean island basalt (OIB) compositions ([La/Sm]N=1.7-5.0, [Ce/Yb]N=1.58-11.3) with isotopic signatures (143Nd/144Nd = 0.51294-0.51316, 206Pb/204Pb = 19.14-19.93, 176Hf/177Hf = 0.28307-0.28312) trending to or overlapping the ubiquitous FOZO (Focal Zone, e.g., Hart et al., 1992, Science 256) mantle composition. Major and trace element characteristics denote that RR lavas formed by small degrees of melting from a deep source in the garnet stability field and experienced high pressure fractionation beneath a lithospheric lid. Although the sparseness of samples suitable for 40Ar/39Ar dating prevents establishing a clear age progression for the seamount chain, one well constrained basalt groundmass age of 28.75 ± 0.14 Ma (2σ) for one seamount near the western end of RR indicates that this volcano formed ~11 Ma later than the underlying lithosphere. Taken together, RR is interpreted as a hotspot track, albeit formed by a relatively weak melting anomaly. Compared to RR, the lavas from the 14° N MAR anomaly have slightly less enriched compositions, exhibiting enriched (E)-MORB compositions ([La/Sm]N=1.81-2.29). Their isotopic ratios largely overlap with the RR compositions, thus suggesting a genetic relationship. We therefore propose that the enigmatic 14°N MAR anomaly is caused by deflection of upwelling RR plume material towards the approaching (westward migrating) MAR, causing the production of E-MORBs with nearly similar isotopic compositions to the RR lavas. Once the plume was captured by the spreading ridge, off-axis hotspot track volcanism ceased, resulting in a 300 km wide gap of seamount formation between the eastern end of RR and the MAR.

The upper crust in the forearc of the Cascadia subduction zone hosts a complex network of faults that accommodate trench-parallel and trench-normal shortening due to oblique subduction and northward migration of the Oregon/Washington forearc block. Outside of the Seattle area, the seismic potential of major faults, as well as how they connect in a 3-D network, is poorly known. The trench-normal Doty fault, a major, north-dipping forearc fault crosses the I-5 corridor south of the Centralia-Chehalis urban area. Its length, orientation, and hypothesized total offset are comparable to the active Seattle fault, but it is unclear if the Doty fault poses a similar modern seismic hazard. We present preliminary results from the Chehalis Basin project (fieldwork summer 2018). We seek to define the Doty fault’s length, structure, dip, and linkages with smaller, likely transpressive faults to accommodate 3-D crustal deformation. We investigate possible blind faults south of the mapped Doty fault, near the site of a proposed flood-control water retention facility, and present evidence for recent fault activity. A multi-disciplinary approach is critical for regional investigations given dense foliage and glacial cover. Thus, we apply aeromagnetic and ground magnetic data, a regional gravity grid, high-resolution gravity lines, seismicity from a local broadband network, targeted geologic mapping, provenance characterization of Quaternary to Neogene sediments, dating, Lidar interpretation and field reconnaissance of geomorphic features to our research questions. The aeromagnetic data and prior geologic mapping suggest the Doty fault connects to unnamed NNW-striking faults to the west, and our new data will confirm or refute this hypothesis. Initial mapping and aeromagnetic interpretation suggest transpressive faults exist NNE of the Doty fault, which together bound a discrete region of uplift (Lincoln Creek uplift). There is little seismicity in the region recorded by the PNSN regional seismic network, and our PASSCAL array will help confirm the existence or absence of small, local earthquakes that could indicate neotectonic activity.

The Superior Province Rifting Earthscope Experiment (SPREE) deployed seismic stations in 2011-2013 throughout Wisconsin, Minnesota, and Ontario. To protect equipment from groundwater damage, SPREE stations were buried at unusually shallow depths, increasing the power of long period noise and facilitating an investigation into the regional effects of atmospheric tides and soil properties (Wolin et al., 2015). Here we utilize the SPREE array to study the effects of solid-earth tides and meteorological conditions, on very long-period seismic noise in the U.S. midcontinent. Continuous seismic data was collected from SPREE and Transportable Array (TA) stations located in Wisconsin and Minnesota (WIMN) between July 2011 and September 2013. This data was “cleaned”, filtered, and averaged to produce a monthly representation of the very-long period signals recorded by the SPREE stations. The signals showed diurnal (24 hr) and semidiurnal (12 hr) periodicities, whose magnitudes and dominance vary seasonally. Using cross correlations, we compare our very-long period observations with theoretical solid-earth tides (Milbert, 2018) as well as meteorological components in the WIMN region. Meteorological data, specifically temperature and pressure, was obtained from the National Oceanic and Atmospheric Administration’s (NOAA) National Center for Environmental Information (NCEI). Solid-earth tides result from the gravitational pull of the moon and sun, and have previously been documented in seismic data (e.g. Pillet et al.,1994; Lambotte et al., 2005). We observe a distinct correlation between theoretical solid-earth tides and very-long period signals in seismic data from SPREE and TA stations in the WIMN region, where one frequency component is correlated while the other appears delayed. In addition, we observe a remarkable seasonal change in SPREE recordings of these signals, but not in TA recordings. We will report our findings from testing the hypothesis that the observed very-long period signals in SPREE data are a combination of both tidal and thermal effects and that these cumulative effects are the result of the unusual burial depth of SPREE stations.

Although it has been well recognized that clouds tremendously affect the surface solar irradiance and its direct and diffuse partitions, accurately forecasting solar radiation in cloudy conditions remains a major challenge. This study focuses on two aspects of the challenge: impacts of cloud microphysics and model domain size. First, we will examine the sensitivity of surface solar radiation and its partitions to cloud microphysics by using the state of art Weather Research and Forecasting model specifically designed for simulating and forecasting solar radiation (WRF-Solar). A number of microphysical schemes will be tested, and comparison against the measurements of shallow cumulus clouds and stratiform clouds selected at the DOE ARM SGP Site. Efforts will be made to quantify the resultant uncertainty spread. Second, identifying the physical causes of the underlying model differences is even more challenging. To address this, we will introduce a new model evaluation framework based on different setups of WRF-Solar (single column, LES, and nested WRF). In particular, we will examine the effect of the number of LES grid columns and its lower limit producing reasonable results. Commonly used evaluation metrics will be used in our model evaluation, including the used RMSE, MAE, MAPE, and relative Euclidean distance. The results will provide physical insight into the understanding of cloud-radiation interactions and forecasting of solar radiation in cloudy conditions.

Improved urban greenhouse gas (GHG) flux estimates are crucial for informing policy and mitigation efforts. Atmospheric inversion modelling (AIM) is a widely used technique combining atmospheric measurements of trace gas, meteorological modelling, and a prior emission map to infer fluxes. Traditionally, AIM relies on mid-afternoon observations due to the well-represented atmospheric boundary layer in meteorological models. However, confining flux assessement to daytime observations is problematic for the urban scale, where air masses typically move over a city in a few hours and AIM therefore cannot provide improved constraints on emissions over the full diurnal cycle. We hypothesized that there are atmospheric conditions beyond the mid-afternoon under which meteorological models also perform well. We tested this hypothesis using tower-based measurements of CO2 and CH4, wind speed observations, weather model outputs from INFLUX (Indianapolis Flux Experiment), and a prior emissions map. By categorizing trace gas vertical gradients according to wind speed classes and identifying when the meteorological model satisfactorily simulates boundary layer depth (BLD), we found that non-afternoon observations can be assimilated when wind speed is >5 m/s. This condition resulted in small modeled BLD biases (<40%) when compared to calmer conditions (>100%). For Indianapolis, 37% of the GHG measurements meet this wind speed criterion, almost tripling the observations retained for AIM. Similar results are expected for windy cities like Auckland, Melbourne, and Boston, potentially allowing AIM to assimilate up to 60% the total (24-h) observations. Incorporating these observations in AIMs should yield a more diurnally comprehensive evaluation of urban GHG emissions.

The field of MultiSector Dynamics (MSD) explores the dynamics and co-evolutionary pathways of human and Earth systems with a focus on critical goods, services, and amenities delivered to people through interdependent sectors. This commentary lays out core definitions and concepts, identifies MSD science questions in the context of the current state of knowledge, and describes ongoing activities to expand capacities for open science, leverage revolutions in data and computing, and grow and diversify the MSD workforce. Central to our vision is the ambition of advancing the next generation of complex adaptive human-Earth systems science to better address interconnected risks, increase resilience, and improve sustainability. This will require convergent research and the integration of ideas and methods from multiple disciplines. Understanding the tradeoffs, synergies, and complexities that exist in coupled human-Earth systems is particularly important in the context of energy transitions and increased future shocks.

Uturuncu volcano is situated in the Bolivian Andes, directly above the world’s largest crustal body of silicic partial melt, the Altiplano-Puna Magma Body (APMB). Uturuncu last erupted 250,000 years ago, yet is seismically active and lies at the centre of a 70 km diameter uplifted region. Here, we analyse seismicity from 2009 to 2012. Our earthquake locations, using a newly developed velocity model, delineate the top and bottom of the APMB, reveal individual faults, and reconcile differences in depth distribution between previous studies. Spatial clustering analysis of these earthquakes reveals the orientations of the faults, which match stress orientations from seismic anisotropy. Earthquake b-values derived from moment magnitudes (1.4) differ significantly from those using local magnitude measurements (0.8). We suggest that, if possible, moment magnitudes should always be used for accurate b-value analysis. We interpret b-values > 1 in terms of fluid-enhanced seismicity. Shallow seismicity local to Uturuncu yields b-values > 1.1 with some temporal variation, suggesting fluid migration along pre-existing faults in a shallow hydrothermal system, likely driven by advection from the APMB. Intriguingly, events deeper than the APMB also yield large b-values (1.4), mapping the ascent into the lower crust of fluids originating from a subducting slab. Cumulatively, these results provide a picture of an active magmatic system, where fluids are exchanged across the more ductile APMB, feeding a shallow, fault-controlled hydrothermal system. Such pathways of fluid ascent may influence our understanding of arc volcanism, control future volcanic eruptions and promote the accumulation of shallow hydrothermal ore deposits.

This article is composed of three independent commentaries about the state of ICON principles (Goldman et al., 2021) in the AGU section Paleoclimatology and Paleoceanography (P&P), and a discussion on the opportunities and challenges of adopting them. Each commentary focuses on a different topic: (Section 2) Global collaboration, technology transfer and application, reproducibility, and data sharing and infrastructure; (Section 3) Local knowledge, global gain: improving interactions within the scientific community and with locals, indigenous communities, stakeholders, and the public; (Section 4) Field, experimental, remote sensing, and real-time data research and application.P&P projects can better include ICON principles by directly incorporating them into research proposals. A promising way to overcome the challenges of interdisciplinarity and integration is to foster networking, which will advance our research discipline through the application of ICON.

We study how the vertical distribution of relative humidity (RH) affects climate sensitivity, even if it remains unchanged with warming. Using a radiative-convective equilibrium model, we show that the climate sensitivity depends on the shape of a fixed vertical distribution of humidity, tending to be higher for atmospheres with higher humidity. We interpret these effects in terms of the effective emission height of water vapor. Differences in the vertical distribution of RH are shown to explain a large part of the 0 to 30% differences in clear-sky sensitivity seen in climate and storm-resolving models. The results imply that convective aggregation reduces climate sensitivity, even when the degree of aggregation does not change with warming. Combining our findings with relative humidity trends in reanalysis data shows a tendency toward Earth becoming more sensitive to forcing over time. These trends and their height variation merit further study.

Terrestrial Gamma-Ray flashes exhibit slopes of ionizing radiation associated with Bremsstrahlung. Bremsstrahlung has a continuous spectrum of radiation from radio waves to ionizing radiation. The Poynting vector of the emitted radiation, i.e., the radiation pattern around a single particle under the external lightning electric field during interaction with other particles or atoms, is not quite well known. The overall radiation pattern arises from the combination of radiation of parallel and perpendicular motions of a particle caused by the acceleration from the lightning electric field and the Bremsstrahlung. The calculations and displays of radiation patterns are generally limited to a low-frequency approximation for radio waves and separate parallel and perpendicular motions. Here we report the radiation patterns of combined parallel and perpendicular motions from accelerated relativistic particles at low and high frequencies of the Bremsstrahlung process with an external lightning electric field. The primary outcome is that radiation patterns have four relative maxima with two forward peaking and two backward peaking lobes. The asymmetry of the radiation pattern, i.e., the different intensities of forward and backward peaking lobes, are caused by the Doppler effect. A novel outcome is that Bremsstrahlung has an asymmetry of the four maxima around the velocity vector caused by the curvature of the particle's trajectory as it emits radiation. This mathematical modeling helps to better understand the physical processes of a single particle's radiation pattern, which might assist the interpretation of observations with networks of radio receivers and arrays of gamma-ray detectors.

Radiocarbon (14C) is a powerful tracer of fossil emissions because fossil fuels are entirely depleted in 14C, but observations of 14CO2 and especially 14CH4 in urban regions are sparse. We present the first observations of 14C in both methane (CH4) and carbon dioxide (CO2) in an urban area (London) using a recently developed sampling system. We find that the fossil fraction of CH4 and the atmospheric concentration of fossil CO2 are consistently higher than simulated values using the atmospheric dispersion model NAME coupled with emission inventories. Observed net biospheric uptake in June-July is not well correlated with simulations using the SMURF model with NAME. The results show the partitioning of fossil and biospheric CO2 and CH4 in cities can be evaluated and improved with 14C observations when the nuclear power plants influence is negligible.