The East African Rift System provides a rare location in which to observe a wide scope of rifting states. Well-defined active narrow rifting in the Main Ethiopian Rift (MER) transitions to incipient extension and eventually pre-rifted lithosphere through the northwestern flank of the Ethiopian Plateau (EP). Although the MER is well studied, the off-axis region has received less attention. We develop Rayleigh wave phase velocity maps, Ps receiver functions, and H-κ; stack surfaces, and jointly invert these data using a trans-dimensional, hierarchical Bayesian inversion algorithm to create shear velocity profiles across the MER and EP. All shear velocities observed are slower than the PREM global average, a reflection of the elevated temperatures that persist from plume impingement. In the EP, we find a shallow mantle slow shear velocity lineament parallel to the MER axis, amidst otherwise faster shear velocities. The crust is shallow in the MER, but also in the northwestern EP flank, with thicker crust found throughout the plateau caused by crustal underplating and flood basalt emplacement. Shear velocities more reduced than the already low regional average, in concert with surficial volcanic features, geodetic observations, and slow P- and S-wave anomalies, support off-axis extension in the Ethiopian plateau, requiring reevaluation of the localization of continental breakup in the narrow MER.

Relative sea-level rise is a major coastal hazard affecting about half the population of the United States. The Chesapeake Bay is characterized by the fastest rate of sea-level rise along the Atlantic coast of North America, in part because of land subsidence. Previous studies have quantified a range of land subsidence rates in the Chesapeake Bay (~1-4 mm/yr) from various measurement techniques that contribute to high rates of relative sea-level rise. In this study, we present progress towards developing a new vertical land motion map for the Chesapeake Bay region to provide more robust constraints on estimates of relative sea-level rise. We are using a combination of GNSS observations and InSAR interferograms. Available continuous GNSS data in the region that span November 2014 - September 2020 are processed with GAMIT-GLOBK to align temporally with available Sentinel-1 InSAR satellite data. We are using an approach that combines the two geodetic observations to provide a new solution of vertical land motions for the Chesapeake Bay. Additionally, this project is collecting new campaign GNSS observations across the Chesapeake Bay each fall for 5 years, beginning in 2019. We will also present about the 2020 and planned 2021 campaign GNSS observations, which will ultimately be incorporated into our new map of vertical land motions for the region. The impacts of this work will be improved flooding and inundation hazard maps, as well as updated projections for municipal flood mitigation planning that will be created using the new dataset.

Predicting the partitioning between aqueous and gaseous C across landscapes is difficult because many factors interact to control CO2 concentrations and removal as DIC. For example, carbonate minerals may buffer soil pH so that CO2 dissolves in porewaters, but nitrification of fertilizers may decrease pH so that carbonate weathering results in a gaseous CO2 efflux. Here, we investigate CO2 production and dissolution in an agricultural, first-order, mixed-lithology humid, temperate watershed. We quantified soil mineralogy and measured porewater chemistry, soil moisture, and pCO2 and pO2 as a function of depth at three hillslope positions for a year. The variation of soil moisture along the hillslope was the dominant control on the concentration of soil CO2, but mineralogy acted as a secondary control on the partitioning of CO2 between the gaseous and aqueous phases. The regression slopes of pCO2 vs. pO2 in the carbonate-bearing soils indicate a deficit of CO2 relative to O2 (p < 0.05). Additionally, we found no abiotic gaseous CO2 efflux from carbonate weathering. We concluded that in the calcareous soils, about a third of respired C dissolves and drains from the soil rather than diffusing out to the atmosphere. To represent the global scope of the reactions we evaluated at our local watershed, we used databases of carbonate minerals and land uses to map types of soil degassing behaviors. Based on our maps, the partitioning of respired soil CO2 to the aqueous phase may be globally common and should be accounted for in ecosystem C budgets and models.

Monitoring slow earthquake activity in subduction zones can give important insight into the stress build-up and subsequent rupture extent of megathrust earthquakes. Extensive slow earthquake activity occurs up-dip of the seismogenic zone of the Nankai Trough subduction zone, an area that might be awaiting a large (Mw {greater than or equal to}8) earthquake in the near future. Mechanisms used to explain the occurrence of slow earthquakes are often linked to temporal changes in fluid transport along faults. This study utilises this theory in evaluating the usage of 4D gravity measurements on the seafloor for monitoring changes in fluid flow, hence monitoring the slow earthquake activity and the mechanisms behind them. We model the gravity response from fluid-related density changes in an area of the Nankai Trough accretionary prism that experiences several slow earthquake episodes in the interseismic period. The forward modelled 4D gravity response is used to estimate volumes of fluid at specific locations of the accretionary prism and plate interface corresponding to a minimum gravity signal of 5 µGal. This accuracy in the gravity signal is obtainable through technology monitoring micro-gravity effects at the seafloor. Based on the results we have formulated a hypothesis on how small fluid volume changes can be detected through a gravimetry survey at the seafloor of the Nankai Trough. The results can also be used to design a survey layout for obtaining valuable 4D gravity data at the Nankai Trough.

Preservation of organic carbon (OC) in marine sediments exerts a major control on the cycling of carbon in the Earth system. In marine sediment, OC preservation may be enhanced by diagenetic reactions in locations where deposition of tephra occurs. While the mechanisms by which this process occurs are well understood, site-specific studies are limited. Here, we report on a study of sediments from the Bering Sea (IODP Site U1339D) to investigate the effects of marine tephra deposition on carbon cycling during the Pleistocene and Holocene. Our results strongly suggest that tephra layers are loci of OC burial with distinct d13C values, and that this process is primarily linked to complexation of OC with reactive metals (accounting for ~80% of all OC within tephra layers). In addition, distribution of reactive metals into non-volcanic sediments above and below the tephra layers enhances OC preservation in these sediments, with ~33% of OC bound to reactive phases. Importantly, OC-Fe coupling is evident in sediments >700,000 years old. Thus, these interactions may help explain the preservation of labile OC in older marine sediments.

 About 60 percent of the hydrographic stations show negative bias for collected river 12 discharge. 13  Nearly 80 percent of the hydrographic stations show good skill with significant mean 14 absolute error at few stations. 15  The assessment shows a good skill for Ganges-Brahmaputra and the lowest for Pennar and 16 Cauvery river basins. Abstract 18 A significant task in river hydrology is to envisage the river’s present, past, and future 19 environments. India has some of the world’s major river basins, including Ganges-Brahmaputra, 20 Mahanadi, Krishna, and the Godavari produce an enormous amount of water as river discharge 21 alongside turbidity into the Bay of Bengal. The revised Kling-Gupta efficiency skill score 22 (KGESS) has been used to determine the performance of reanalysis river discharge. The skill of 23 reanalysis discharge was found admirable for the Ganges-Brahmaputra river basin (KGESS = 0.86 24 > 0), with notable mean absolute error and high correlation coefficient (0.94). Furthermore, 25 Subarnarekha, Brahmani-Baitarani, Mahanadi, Godavari, Krishna river basins, and the rivers 26 flowing between Mahanadi and Pennar Rivers exhibit moderate to good skill. However, Pennar, 27 Cauvery, and the rivers flowing between Pennar and Kanyakumari show the lowest skill. 28 Approximately 60% hydrographic stations of river catchments demonstrate that reanalysis 29 discharge is negatively biased (i.e., bias < 1). Nearly 58% hydrographic stations show lower 30 variability (i.e., variability ratio < 1) with the median value of 0.91 and the interquartile range 31 (0.82, 1.13). Moreover, the overall median of the Pearson correlation coefficient was 0.73 with 32 interquartile ranges between 0.51-0.83. The reanalysis and observed datasets show a significant 33 change in river discharge throughout the southwest monsoon and less in the post-monsoon period. 34 Concurrently, some hydrographic stations show a significant increase in river discharge during 35 post-monsoon in Pennar and Cauvery River basins. 36 37

We quantify the volume transport and watermass transformation rates of the global ocean circulation using data from the Estimating the Circulation and Climate of the Ocean version 4 release 3 (ECCOv4r3) reanalysis product. Our results support large rates of intercell exchange between the mid-depth and abyssal cells, in agreement with modern theory and observations. However, the present-day circulation in ECCO cannot be interpreted as a near-equilibrium solution. Instead, a dominant portion of the apparent diapycnal transport of watermasses within the deep ocean is associated with isopycnal volume change, rather than diabatic processes, reflecting trends in the deep ocean density structure. Our results imply two possibilities: either such trends in ECCOv4r3 are unrealistic, implying that ECCO’s representation of the overturning circulation and watermass transformations are inconsistent, or the trends in ECCOv4r3 are realistic and equilibrium theories of the overturning circulation cannot be applied to the present-day ocean.

Understanding the exposure of business characteristics like its location, sector, size, age, and owner demographics and structure to building damages from an earthquake can inform business continuity planning and broader community and regional programs and policies for business recovery. A baseline analysis was performed for the HayWired scenario (Wein, Haveman and others, 2019) using business characteristic data from the National Establishment Time Series (NETS) which showed that location and sector are strong differentiators of disruptive building damage risk, while minority ownership, branch ownership structure, and low revenue are other above average differentiators. The HayWired analysis was limited by damage information at the census tract scale for occupancy classes (per the Federal Emergency Management Agency Hazus software). In this study, we expand the analysis to multiple earthquake scenarios and apply machine learning techniques to generate building level assessments instead of census tract level. Association of business characteristics with building damages by location increases the analysis resolution providing more nuanced understanding and analyzing across multiple scenarios shows the variability of business characteristic exposure to different earthquakes for the region and across communities. Anne Wein, Jon Haveman, Cynthia Kroll, Jeff Peters. 2019. Characteristics of Businesses disrupted by Building Damages from the HayWired Scenario Mainshock, in press.

As tides propagate inland, they become distorted by channel geometry and river discharge. Tidal dynamics in fluvial-marine transitions are commonly observed in high-energy tidal environments with relatively steady river conditions, leaving the effects of variable river discharge on tides and longitudinal changes poorly understood. To study the effects of variable river discharge on tide-river interactions, we studied a low-energy tidal environment where river discharge ranges several orders of magnitude, the diurnal microtidal Tombigbee River-Mobile Bay fluvial-marine transition, using water level and velocity observations from 21 stations. Results showed that tidal attenuation was reduced by the width convergence in seaward reaches and height convergence of the landward backwater reaches, with the channel convergence change location ~40-50km inland of the bayhead and seaward of the largest bifurcation (~rkm 90-100). River events amplified tides in seaward regions and attenuated tides in landward regions. This created a region of river-induced peak amplitude seaward of the flood limit (i.e., bidirectional-unidirectional current transition) and passed more tidal energy inland. Tidal currents were attenuated and lagged more with river discharge than water levels, making the phase lag dynamic. The river impacts on the tides were delineated longitudinally and shifted seaward as river discharge increased, ranging up to ~180 km. Results indicated the location and longitudinal shifts of river impacts on tides in alluvial systems can be estimated analytically using the ratio of river discharge to tidal discharge and the geometry convergence. Our simple analytical theory provides a pathway for understanding the tide-river-geomorphic equilibrium along increasingly dynamic coasts.

The radiative cooling rate in the tropical upper troposphere is expected to increase as climate warms. Since the tropics are approximately in radiative-convective equilibrium (RCE), this implies an increase in the convective heating rate, which is the sum of the latent heating rate and the eddy heat flux convergence. We examine the impact of these changes on the vertical profile of cloud ice amount in cloud-resolving simulations of RCE. Three simulations are conducted: a control run, a warming run, and an experimental run in which there is no warming but a temperature forcing is imposed to mimic the warming-induced increase in radiative cooling. Surface warming causes a reduction in cloud fraction at all upper tropospheric temperature levels but an increase in the ice mixing ratio within deep convective cores. The experimental run has more cloud ice than the warming run at fixed temperature despite the fact that their latent heating rates are equal, which suggests that the efficiency of latent heating by cloud ice increases with warming. An analytic expression relating the ice-related latent heating rate to a number of other factors is derived and used to understand the model results. This reveals that the increase in latent heating efficiency is driven mostly by 1) the migration of isotherms to lower pressure and 2) a slight warming of the top of the convective layer. These physically robust changes act to reduce the residence time of ice along at any particular temperature level, which tempers the response of the mean cloud ice profile to warming.

The prediction of the weather at subseasonal-to-seasonal (S2S) timescales is dependent on both initial and boundary conditions. An open question is how to best initialize a relatively small-sized ensemble of numerical model integrations to produce reliable forecasts at these timescales. Reliability in this case means that the statistical properties of the ensemble forecast are consistent with the actual uncertainties about the future state of the geophysical system under investigation. In the present work, a method is introduced to construct initial conditions that produce reliable ensemble forecasts by projecting onto the eigenfunctions of the Koopman or the Perron-Frobenius operators, which describe the time-evolution of observables and probability distributions of the system dynamics, respectively. These eigenfunctions can be approximated from data by using the Dynamic Mode Decomposition (DMD) algorithm. The effectiveness of this approach is illustrated in the framework of a low-order ocean-atmosphere model exhibiting multiple characteristic timescales, and is compared to other ensemble initialization methods based on the Empirical Orthogonal Functions (EOFs) of the model trajectory and on the backward and covariant Lyapunov vectors of the model dynamics. Projecting initial conditions onto a subset of the Koopman or Perron-Frobenius eigenfunctions that are characterized by time scales with fast-decaying oscillations is found to produce highly reliable forecasts at all lead times investigated, ranging from one week to two months. Reliable forecasts are also obtained with the adjoint covariant Lyapunov vectors, which are the eigenfunctions of the Koopman operator in the tangent space. The advantages of these different methods are discussed.

Through rover missions and martian meteorites received on Earth, the surface of Mars has showed unexpectedly elevated concentrations of transition metals usually measured in minor and trace concentrations in silicate rocks compared to the average crust. Gale crater presents one of the most diverse geological records in terms of its complex fluid and magmatic history described through the sedimentary and igneous records, respectively. Transition metals, such as Mn, Co, Ni, Cu, and Zn, are highly concentrated within various sedimentary rocks and diagenetic features, suggesting their mobilization through fluid circulation. This paper presents the first compilation of elevated concentrations of transition metals measured by the Curiosity rover and reviews the origin of such metals in Gale crater, highlighting the existence of a hydrothermal or magmatic-hydrothermal deposit in its vicinity. The discovery of felsic magmatism on Mars opens up to novel perspectives in terms of the type of metal deposits that current and future exploration could evidence at the surface of Mars and raise questions about the global abundance of such metals. Constraining the abundance of transition metals is also a central question for exobiology purposes. Because on Earth living organisms use transition metals for their survival and functioning, should live have arisen on Mars, the availability of such chemical elements at the surface could have been essential for its development. An accurate assessment of in situ metal resources and potential risks for health will be key for the preparation of human exploration of Mars as recently announced by NASA.

The overall level of solar activity, and space weather response at earth, varies within and between successive solar cycles and can be characterized by the statistics of bursts, that is, time-series excursions above a threshold. We consider non-overlapping 1 year samples of the auroral electrojet index (AE) and the SuperMAG-based ring current index (SMR), across the last four solar cycles. These indices respectively characterize high latitude and equatorial geomagnetic disturbances. We suggest that average burst duration τ̅ and burst return period R̅ form an activity parameter, τ̅/R̅ which characterizes the fraction of time the magnetosphere spends, on average, in an active state for a given burst threshold. If the burst threshold takes a fixed value, τ̅/R̅ for SMR tracks sunspot number, while τ̅/R̅ for AE peaks in the solar cycle declining phase. Crossing theory directly relates τ̅/R̅ to the observed index value cumulative distribution function (cdf). For burst thresholds at fixed quantiles, we find that the probability density functions of τ̅ and R each collapse onto single empirical curves for AE at solar cycle minimum, maximum, and declining phase and for (-)SMR at solar maximum. Moreover, underlying empirical cdf tails of observed index values collapse onto common functional forms specific to each index and cycle phase when normalized to their first two moments. Together, these results offer operational support to quantifying space weather risk which requires understanding how return periods of events of a given size vary with solar cycle strength.

The Matthew and Hunter (M&H) area, in the South-West Pacific, was formerly interpreted as a transform boundary at the southern termination of the New Hebrides Subduction Zone. But new data collected during three voyages of RV Southern Surveyor (2004-2009), combined with detailed analysis of seismicity and GPS kinematics, shows it is a distinct subduction zone initiated only 2 Ma ago. In fact, M&H is the youngest known volcanically-active intra-oceanic subduction system. We demonstrate that the M&H subduction zone is a modern example of an immature subduction system at the particular stage of pre-arc, near-trench magmatism. It is not yet forming an arc but the proto-forearc. Indeed volcanism occurs much closer to the trench than volcanism at mature subduction zones. Also M&H hosts an exceptionally diverse range of magma compositions, which erupted contemporaneously and are spatially juxtaposed. Pb isotopic compositions and contents of LILE and REE indicate melting of upwelling asthenospheric mantle (Indian MORB) and subducted oceanic crust (Pacific MORB of the South Fiji Basin) and the mixing of these two components. It is worth noting that the present day proto-forearc of the M&H subduction zone corresponds to an area where highly contrasting terranes are juxtaposed: remnants of the old Vitiaz Arc crust, domains of classical backarc basin type oceanic accretion, and what we call Subduction Initiation Terranes (SITER). Such live observations of a growing forearc are rare. They should give insights into the study of fossil forearcs such as SSZ ophiolites but also the IBM forearc.

Earth kilns are still used for charcoal production in the Eastern Mediterranean and worldwide. Until 2016, around 1,600 tons of charcoal were produced in Israel and the Palestinian territories in about 400 traditional earth kilns that were operated in about the same manner for the last 400 years. The intense air pollution caused by this indigenous practice resulted in higher mortality rates among the workers and the population living close to the charcoal production sites. The air pollution was found to migrate beyond 50 km, causing cross-boundary pollution in Jordan. Since the charcoal production industry processes surplus wood into solid fuel, which is used for heating and cooking, it was imperative to shift this industry to a new type of non-polluting charcoal production system. To upgrade this industry to 21st century standards development and implementation of a new ecological retort system (ERS), became possible through a combined effort by Israeli researchers and Palestinian manufacturers. Comparing the ERS to the old earth kilns suggests that the wood-to-charcoal transformation efficiency is about 10% higher in the ERS and the process duration is half a day vs. about three weeks in a traditional kiln. Generally, ERS is about two orders of magnitude more productive than the traditional earth kilns. The ERS combines a simple operational scheme and higher charcoal yield than a traditional kiln, leading to an increase in the revenue to the charcoal makers, also through byproducts bearing economic value such as electric energy and wood vinegar.

We conducted X-ray diffraction (XRD) measurements of a pyrolitic mantle material up to 4480 K at 122-166 GPa in a laser-heated diamond-anvil cell (DAC). Results demonstrate that the phase transition between bridgmanite and post-perovskite occurs in pyrolite within the lowermost mantle pressure range even at >4000 K. It suggests the ubiquitous occurrence of post-perovskite above the core-mantle boundary (CMB), which may be consistent with recent high-quality seismology data that non-observations of D” reflections are exceptions. Combining with earlier experiments performed at and below the normal lower-mantle geotherm, our data show that the bridgmanite + post-perovskite two-phase region is ~5 GPa thick and the Clapeyron slope of the boundary is +7(+2/-3) MPa/K in agreement with previous theoretical calculations. The global presence of rheologically weak post-perovskite at the bottom of the mantle has profound implications in seismology, geodynamics, and heat transfer from the core.

Partitioning evapotranspiration (ET) into its primary components, i.e., evaporation (E) and plant transpiration (T), is needed in a range of hydrometeorological applications. Using vegetation index (VI) to obtain spatially resolved T:ET ratio over large areas has emerged as a promising approach in this regard. Here, we assess the effectiveness of this approach in differently managed wheat systems. Results show a weak relation between T:ET and VI in disturbed (i.e., grazed) systems. Flux partitions based on a canonical T:ET vs. VI relation or one derived in a neighboring undisturbed wheat system introduce large errors in disturbed systems, thus underscoring the limits on the transferability of the VI-based ET partitioning approach. The effectiveness of the VI-based approach is found to be related to the strength of correlation between VI and vapor pressure deficit and/or radiation. This correlation metric can help identify settings where the approach is likely to be effective.

The Antarctic Slope Front (ASF) is a strong gradient in water mass properties close to the Antarctic margins. Heat transport across the ASF is important to Earth’s climate, as it influences melting of ice shelves, the formation of bottom water, and thus the global meridional overturning circulation. Previous studies based on relatively low-resolution models have reported contradictory findings regarding the impact of additional meltwater on onshore heat transport onto the Antarctic continental shelf: it remains unclear whether meltwater enhances shoreward heat transport, leading to a positive feedback, or further isolates the continental shelf from the open ocean. In this study, heat transport across the ASF is investigated using high-resolution, process-oriented simulations. It is found that shoreward heat transport is primarily controlled by the salinity gradient of the shelf waters: both freshening and salinification of the shelf waters relative to the offshore waters lead to increased heat flux onto the continental shelf. For salty shelves, the overturning consists of a dense water outflow that drives a shoreward heat flux near the seafloor; for fresh shelves, there is a shallow, eddy-driven overturning circulation that is associated with an export of fresh surface waters and a near-surface shoreward heat flux. The eddy-driven overturning associated with coastal freshening may lead to a positive feedback in a warming climate: large volumes of meltwater increase shoreward heat transport, causing further melt of ice shelves.