Cloud radiative effects (CRE) have well documented impacts on mean climate, and have recently been found to play a key role in climate variability in the tropics. Here we probe the role of CRE in surface temperature variability in the Northern Hemisphere (NH). We compare output from two climate simulations: one in which clouds are coupled to the atmospheric circulation and another in which they are decoupled from the flow. Cloud-circulation coupling leads to widespread increases in NH surface temperature variability, particularly over the oceans and on decadal timescales. Notably, it leads to substantial increases in decadal temperature variability averaged over the North Atlantic and North Pacific basins. The increases derive from the ‘reddening’ of surface temperature variability by cloud shortwave radiative effects. The results have implications for the interpretation of observed decadal variability, and the importance of cloud-circulation coupling for simulations of decadal variability in climate models.

Martian meteoritic petrology and regional chemistry of Hesperian-Amazonian volcanism support secularly decreasing degrees of partial melting and thickening crust underlain by simple mantle convection. However, the applicability of this interior evolution model and resurfacing trends to the Noachian remains unknown. Using regional gamma spectroscopy and geophysical analysis, we find that supereruptions characterized Noachian volcanism in NW Arabia with co-enriched K, Th, and Si. Geophysical analysis reveals elastic thickness values below 20 km, indicating a heat flux exceeding many Hesperian volcanoes. Collectively, our results support large ion lithophile loss from low degrees of partial melting of the Noachian mantle, signifying an early stage of interior evolution that contrasts with the Hesperian-Amazonian model. Regional chemistry further suggests climate-altering supereruptive exhalations of ~109 kg S-phases.

Catchment studies provide foundational scientific knowledge that is relevant to policy, resource management, education, outreach, and public awareness of the environment and environmental problems. Through a concerted effort to highlight the catchments and catchment studies behind a rich legacy of scientific findings, we have led several efforts to promote long-term and place-based research at monitoring, observatory, and ecosystem study sites. Our efforts have included sessions at AGU and other professional meetings, a special issue of Hydrological Processes, and a CUAHSI Cyberseminar series on monitoring and observation at research catchments that span the globe. In this poster, we continue to promote the catchments and innovative research at those sites by summarizing our efforts and updating a map of the catchment studies that we have identified. Our primary objective is to stimulate discussion about the vibrant state of the catchment sciences, the sites that make the science possible, and how to move forward in coming decades.

To correctly simulate and retrieve dust distributions and estimate dust impacts, global aerosol models and remote sensing retrieval algorithms need accurate single-scattering properties of dust aerosols. However, inconsistent and inaccurate quantifications of dust shape and shape distributions are used in models and retrieval algorithms, generating biases that propagate into the estimated dust distributions and dust impacts. To improve models and retrieval algorithms, here we for the first time account for the realistic dust shape distributions in obtaining single-scattering properties of dust aerosols. We find that approximating dust as spheres and neglecting dust asphericity, as most global aerosol models do, result in substantial underestimations in the extinction efficiency, the asymmetry factor, and the single-scattering albedo for all dust sizes in both the shortwave and longwave spectra. In addition, we find that the inaccurate quantification of dust shape in retrieval algorithms causes them to generate an incorrect magnitude and wavelength dependence of the linear depolarization ratio relative to observations. Our new ellipsoidal dust optics accounting for realistic shape distributions produce excellent agreement with the measured linear depolarization ratio. Although these new dust optics show potential to improve models and retrieval algorithms, they underestimate the magnitude of the back-scattering intensity relative to laboratory and field observations. This finding indicates that a realistic quantification of dust body shape is not sufficient and that an accurate quantification of dust surface texture is also critical to accurately reproduce dust optical properties at back-scattering angles.

Climate models struggle to accurately represent the highly reflective boundary layer clouds overlying the remote and stormy Southern Ocean. We use in-situ aircraft observations from the Southern Ocean Clouds, Radiation and Aerosol Transport Experimental Study (SOCRATES) to evaluate Southern Ocean clouds in a cloud-resolving large-eddy simulation (LES) and two coarse resolution global atmospheric models, the CESM Community Atmosphere Model (CAM6) and the GFDL global atmosphere model (AM4), run in a nudged hindcast framework. We develop six case studies from SOCRATES data which span the range of observed cloud and boundary layer properties. For each case, the LES is run once forced purely using reanalysis data (‘ERA5-based’) and once strongly nudged to an aircraft profile (‘Obs-based’). The ERA5-based LES can be compared with the global models, which are also nudged to reanalysis data, and is better for simulating cumulus. The Obs-based LES closely matches an observed cloud profile and is useful for microphysical comparisons and sensitivity tests, and simulating multi-layer stratiform clouds. We use two-moment Morrison microphysics in the LES and find that it simulates too few frozen particles in clouds occurring within the Hallett-Mossop temperature range. We modify the Hallett-Mossop parameterization so that it activates within boundary layer clouds and we achieve better agreement between observed and simulated microphysics. The nudged GCMs achieve reasonable supercooled liquid water dominated clouds in most cases but struggle to represent multi-layer stratiform clouds and to maintain liquid water in cumulus clouds. CAM6 has low droplet concentrations in all cases and underestimates stratiform cloud-driven turbulence.

Disasters triggered by extreme precipitation events i.e., landslides, debris flows, and floods cause devastating damages to lives, infrastructure, and the economy. Under a warming climate, precipitation extremes and the occurrence of debris flows are further expected to intensify. Driven by extreme runoff, the triggering of debris flows can be simultaneous. Their concurrent occurrence multiplies complexity in decision-making during emergencies. Despite advancements in geotechnics and network science, a systematic framework to analyze the impact of debris flows on road networks is lacking. While network science-based approaches work on large-scale, geotechnics-based damage assessments are done solely on a site-to-site basis. Here we develop an integrated approach to analyze the impacts of simultaneous debris flows on road networks. The approach includes a novel infinite slope-based one-dimensional numerical model that simulates runoff-induced erosion and a network science-based mathematical model for road failures. This study covers multiple catastrophic events of debris flows that occurred in different geological and climate settings i.e., post-earthquake, post-volcanic, and post-wildfire environments. We perform spatio-temporal simulations of initiation and runout of debris flows and calculate the damage caused on individual road segments. We validate the model results using metadata. Our results show even remote local disturbances caused by successive debris flows upstream may lead to complete cascading disruption of the network downstream. Our unified strategy opens avenues to understand the resilience of critical infrastructure networks against catastrophic debris flows.

The “greenhouse” climates of the Paleocene and Eocene have formed the focus for many proxy and modelling studies in recent decades, as they are the closest geological analogues for our future warmer anthropogenic world. Yet, the long-term evolution of ocean temperature and carbonate chemistry at orbital-resolution, especially at low latitudes, are still poorly constrained. Here we present new orbital-resolution foraminiferal trace metal (Mg/Ca & B/Ca) records spanning the late Paleocene to early Eocene (~58–53 Ma) from a new splice between ODP Site 758 and IODP Site U1443, Ninetyeast Ridge, northern Indian Ocean. We generated coupled Mg/Ca and B/Ca records from well-preserved mixed layer and thermocline-dwelling planktic foraminifera, and benthic foraminifera deposited at a shallow palaeo-water depth (~1500 m), to construct temperature change and carbonate chemistry (related to pH and DIC concentration) across a water column depth transect above Ninetyeast Ridge. Our new trace metal records are the first long-term orbital-resolution records of their kind from the poorly studied Indian Ocean. We estimate both the magnitude of long-term warming and associated carbonate chemistry change from the late Paleocene–early Eocene, as well as the magnitude of change on orbital (405- & 100-kyr) timescales. In addition, a portion of the Paleocene-Eocene Thermal Maximum is resolved in our records, providing a critical minimum constraint for the magnitude of temperature and carbonate chemistry change within the low-latitude Indian Ocean during this hyperthermal event.

Recently, studies are featuring larger datasets and an increasing number of hydrological events. Therefore, automated methods have become an indispensable requirement. In this work, an automated procedure to improve hysteresis analysis is proposed. Two main aspects are targeted for methodological improvement:  The qualitative and quantitative analysis axes of hysteresis loops. The concept of Hysteresis Signature, a sequence of parameters that defines the parts forming a hysteresis loop (linear, clockwise, and anticlockwise parts), is introduced to classify hysteresis shapes. A new numeric analysis format is also introduced following the signature to characterize each part of the loop individually. It uses both normalized and real-scale metrics for a full hysteresis quantification. The procedure was extensively tested and validated using 1400+ events from real datasets. Results showed a significant methodological improvement in both the qualitative and quantitative analysis aspects of a given hydrological hysteresis response. The automated classification identified 51 different shapes, successfully confirming the increase of identifiable hysteresis loops. The new numeric analysis format, compared to hysteresis indices, gives a unique quantitative examination in combined forms (e.g., Figure of eight loops) which improves the accuracy of the acquired information. Real-scale quantification improved normalized metrics by reflecting the physical impact associated with the opening of the loop. Finally, The overall results of the method’s testing showed that the procedure is versatile and compatible with varying data types so that the method can be generalized to various hysteresis relationships.

Quantifying variability in the lowermost stratosphere (LMS) is important because of feedbacks among changing temperature, dynamics and species like ozone. We used reprocessed Southern Hemisphere Additional Ozonesondes data from 1998-2018 in a Multiple Linear Regression (MLR) model to analyze variability and trends in free tropospheric (FT) and LMS ozoneacross five well-distributed tropical regions. The MLR also computed trends in a proxy for convection as determined from laminae in each ozonesonde-radiosonde pair. Only the equatorial Americas exhibits statistically significant annual trends in FT or LMS ozone. At the other sites, ozonetrends occur in isolated layers during months when convection has changed, February-April or July-November. Our results imply that large FT ozone increases reported for populated tropical areas may be caused by growing pollution overlying smaller changes caused by perturbed dynamics. They also provide regional data for evaluating LMS ozonetrends based on zonal averages of often sparse satellite measurements

Evidence of syntectonic magmatism associated with onset extension and unroofing of the Menderes Massif metamorphic core complex, western Turkey, is well documented. The Salihli and Turgutlu plutons, located along the Alasehir detachment in the Central Menderes Massif (CMM) and the Koyunoba and Eğrigöz Plutons located in the Northern Menderes Massif (NMM) are common targets for understanding the dynamics and timing of this Cenozoic activity. To this end, here we report new potassium feldspar 40Ar/39Ar ages from samples collected from each pluton and compare these to available zircon U-Pb and monazite Th-Pb crystallization ages. Argon age spectra were collected by incrementally heating bulk concentrates with a CO2 laser and analyzing the gas released at each step. The peraluminous granite samples from the Koyunoba (AT17) and Eğrigöz (WA12) plutons both have effectively flat spectra with average plateau ages of 20.12±0.05 Ma and 19.86±0.05 Ma, respectively. The U-Pb age of zircon from WA12 is 20.5±1.1 Ma [Catlos et al., 2012; doi: 10.2475/05.2012.03 ]; although a zircon U-Pb age from AT17 has not been reported, zircon from other Koyunoba rocks have U-Pb ages between 21.1 Ma and 23.2 Ma [1]. K-feldspar from sample EB06 (Turgutlu Granite) steadily increases in age from 10.62±0.03 Ma to a plateau age of 14.06±0.03 Ma, with similar inverse isochron (13.66±0.29 Ma) and total gas ages (13.36±0.2 Ma). Sample EB05 (Salihli Granite) increases in age from 3.27±0.10 Ma (step 3, 0.5% 39Ar released) to a maximum of 6.05±0.09 Ma (step 33, 96.6% 39Ar released). A plateau age could not be estimated for this sample, but two inverse isochron ages from different degassing steps are calculated (3.02±0.09 Ma for the initial 19 steps and 3.29±0.22 Ma, for the final steps 19-31). Regarding their crystallization histories, the oldest reported monazite Th-Pb age for EB06 is 15.5±1.2 Ma [2] and reported monazite Th-Pb ages for Salhili granite ranges from 9.6±1.6 Ma to 21.7±4.5 Ma [Catlos et al., 2010; https://doi.org/10.1016/j.tecto.2009.06.001]. These 40Ar/39Ar ages suggest NMM plutons rapidly cooled whereas CMM Salihli and Turgutlu plutons not only remained at depth below the argon retention window for a prolonged period following emplacement, but each experienced unique thermal (exhumation) histories despite their geographic proximity.

Empirical models of the thermospheric neutral density are routinely used by mission planners and systems engineers to perform orbit maintenance, collision avoidance, and estimate time and location of re-entry for spacecraft. These models have characteristic errors in neutral density below 10% during geomagnetic quiet time, but perform worse during intense geomagnetic activity, being unable to reproduce the significant increases in the neutral density that are observed during geomagnetic storms. Underestimation of the density during these conditions translates to errors in orbit propagation that reduce the accuracy of any resulting orbit predictions. These drawbacks directly translate into safety risks for astronauts and orbiting spacecraft, but also limit our understanding of the physics of neutral density enhancements. Numerous CubeSats with publicly available ephemeris in the form of two-line element (TLEs) sets orbit in this region. We present the Multifaceted Optimization Algorithm (MOA), a method to estimate the neutral density by minimizing the error between a modeled trajectory and a set of TLEs. Specifically, the algorithm estimates corrections to the inputs of the NRLMSISE-00 empirical density model, and applies those corrections along-track the SWARM spacecraft orbits. This results in orbit-averaged empirical densities below 10% error in magnitude, compared to errors in excess of 25\% for uncalibrated NLRMSISE-00.

The outbreak of coronavirus disease 2019 (COVID-19) has caused tremendous loss to human life and economic decline in China. A timely assessment of COVID-19’s impact on provincial CO emission reductions is crucial for accurately understanding the degree of reduction and its implications for mitigation measures. Here, we used gross domestic product (GDP) and an inventory (CEADs) to estimate the reductions in the first quarter (Q1) of 2020. We find a reduction of -257.7 Mt CO (-11.0%) over 2019 Q1. Secondary industry contributed 72.5% of the total reduction, due largely to lower coal consumption and cement reduction. At the provincial level, Hubei contributed the most to reductions. Transportation reduction also made a significant contribution. One policy implication is advocating working from home and holding teleconferences to reduce traffic emissions. We provide provincial reductions as spatial constraints for modeling studies and further support for both the carbon cycling scientists and policy makers.

Jupiter’s giant magnetosphere is a complex system seldom in a configuration approximating steady state, and a clear picture of its governing dynamics remains elusive. Crucial to understanding how the magnetosphere behaves on a large scale are disturbances to the system on length-scales comparable to the cavity, which are communicated by magnetohydrodynamic waves in the ultra-low-frequency band (≤ 1 mHz). In this study we used magnetometer data from multiple spacecraft to perform the first global heritage survey of these waves in the magnetosphere. To map the equatorial region, we relied on the large local-time coverage provided by the Galileo spacecraft. Flyby encounters performed by Voyager 1 and 2, Pioneer 10 and 11, and Ulysses provided local-time coverage of the dawn sector. We found several hundred events where significant wave power was present, with periods spanning ~5-60 min. The majority of events consisted of multiple superposed discrete periods. Periods at ~15, ~30 and ~40 min dominated the event-averaged spectrum, consistent with the spectra of quasi-periodic pulsations often reported in the literature. Most events were clustered in the outer magnetosphere close to the magnetopause at noon and dusk, suggesting that an external driving mechanism may dominate. The most energetic events occurred close to the planet, though more sporadically, indicating an accumulation of wave energy in the inner magnetosphere or infrequent impulsive drivers in the region. Our findings suggest that dynamics of the system at large scales is modulated by this diverse population of waves, which permeate the magnetosphere through several cavities and waveguides.

Analytical long-profile models of fluvial incision are fundamental in geomorphology, however, analogous models are missing for glaciers, despite the fact that glaciers are an important and widespread agent of physical erosion. We introduce a new analytical solution for coupled glacial-fluvial networks under steady-state climate and uplift. We then integrate this solution into a critical wedge orogen theory to explore the effect of glaciation on the balance between climate, erosion and orogen geometry. We find that the relief is closely tied to the equilibrium line altitude (ELA) and that the geometry and average uplift rate can respond significantly more sensitively to changes in climate than critical wedge orogens dominated by fluvial erosion. Using this observation, we suggest that the global lower ELA during glacial maximums over the last few millions years could trigger narrowing of critical orogens, with an associated increase in uplift rates within the active orogen core.

The pre-2004 9.0 Aceh earthquake Global Positioning System (GPS) velocity field along the western margin of the Sunda plate was dominated by the long-term secular velocity and elastic strain. Since then a sequence of the great earthquakes includes the 2005 8.6 Nias, 2007 8.5 Bengkulu, and 2012 8.6 and 8.2 Wharton Basin earthquakes, have occurred in different segments of the subduction zone and its vicinity, which resulted in significant coseismic and postseismic deformation on the Sunda plate. This study combined the published and the estimated GPS velocity fields between 1991–2016 from more than 150 GPS sites. These velocity fields are inverted to examine the angular velocities of the elastic crustal blocks and the variability of the coupling on the subduction trench. This analysis reveals the characteristic of the Sunda subduction interface over multiple earthquake cycles along different segments of the trench, whereby the subduction interface coupling coefficient changed both spatially and temporally after each rupture. The strongly coupled subduction interface along the plate convergence before 2004 earthquake is now partially coupled to freely slipping in the segments that ruptured during the 2005 and 2007 earthquakes, according to the present-day GPS velocity field (2012.2–2016.0). Interestingly, the best fitting model shows that the Siberut segment (0.5–2.0°S) remained fully coupled throughout the years. The result implies that the level of coupling along the highly segmented Sunda subduction interface varies over time, and that the great earthquake rupture was likely to be a result of the variation in the coupling.

Thin boundary layer Arctic mixed-phase clouds are generally thought to precipitate pristine and aggregate ice crystals. Here we present automated surface photographic measurements showing that only 35% of precipitation particles exhibit negligible riming and that graupel particles ≥1 mm in diameter commonly fall from clouds with liquid water paths less than 50 g m^-2. A simple analytical formulation predicts that significant riming enhancement can occur in updrafts with speeds typical of Arctic clouds, and observations show that such conditions are favored by weak temperature inversions and strong radiative cooling at cloud top. However, numerical simulations suggest that a mean updraft speed of 0.75 m s^-1 would need to be sustained for over one hour. Graupel can efficiently remove moisture and aerosols from the boundary layer. The causes and impacts of Arctic riming enhancement remain to be determined.

The month-to-year-long deformation of the Earth’s crust where active subduction zones terminate is poorly explored. Here we report on a multidisciplinary dataset that captures the synergy of slow-slip events, earthquake swarms and fault-interactions during the ~5 years leading up to the 2018 M 6.9 Zakynthos Earthquake at the western termination of the Hellenic Subduction System (HSS). It appears that this long-lasting preparatory phase initiated due to a slow-slip event that lasted ~4 months and released strain equivalent to a ~M 6.3 earthquake. We propose that the slow-slip event, which is the first to be reported in the HSS, tectonically destabilised the upper 20-40 km of the crust, producing alternating phases of seismic and aseismic deformation, including intense microseismicity (M<4) on neighbouring faults, earthquake swarms in the epicentral area of the M 6.9 earthquake ~1.5 years before the main event, another episode of slow-slip immediately preceding the mainshock and, eventually, the large (M6.9) Zakynthos Earthquake. Tectonic instability in the area is evidenced by a prolonged (~4 years) period of overall suppressed b-values (<1) and strong earthquake interactions on discrete strike-slip, thrust and normal faults. We propose that composite faulting patterns accompanied by alternating (seismic/aseismic) deformation styles may characterise multi-fault subduction-termination zones and may operate over a range of timescales (from individual earthquakes to millions of years).

The Salton Trough is one of the few regions on Earth where rifting is sub-aerial instead of sub-marine. We use the relative attenuation of teleseismic P phases recorded by the Salton Trough Seismic Imaging Project to investigate lithospheric and asthenospheric structures that form during extension. Map-view analysis reveals stronger attenuation within the Salton Trough than in the adjacent provinces. We then construct tomographic models for variations in seismic attenuation with depth to discriminate between crustal and mantle signals with a damped least-squares approach and a Bayesian approach. Synthetic tests show that models from damped least-squares significantly under-estimate the strength of attenuation and cannot separate crustal and mantle signals even when the tomographic models are allowed to be discontinuous at the lithosphere-asthenosphere boundary. We show that a Bayesian approach overcomes these problems when inverting the same synthetic datasets, and that shallow and deep signals are more clearly separated when imposing a discontinuity. With greater than 95% confidence, the results reveal first, that attenuation occurs primarily beneath the LAB; second, that the width of the attenuative region is narrower than the rift at 120 km depth; and third, that the strength of attenuation requires that the attenuative feature represents a melting-column similar to those beneath mid-ocean ridges. The narrow width of the melting-column below the volatile-free solidus is inconsistent with models for passive upwelling, where flow is driven only by rifting. Instead, we attribute the generation of incipient oceanic crust to mantle upwelling focused by buoyancy into a narrow diapir.