Water scarcity is a critical global issue impacting human life. Supply-side solutions alone do not meet the ever-increasing water demands. Economic assessment of water resources can reduce water scarcity risk by managing and prioritizing demand. This study aims to estimate domestic water withdrawal (DWW) and its economic value globally from 1980–2010. To represent the economic value, consumer surplus is calculated by building a demand function for each country, based on the water price at different levels of DWW per capita (DWWC). Global domestic water withdrawal increased by a factor of 2.1 in 2010 compared to 1980, with an average annual growth rate of 2.5%, while the population increased 1.5 times during the same period. In 2010, 93-645 million people, in particular, 93-500 million of the African population, did not have access to the basic water demand. The global average of DWWC’s economic value is estimated as 2,015-4,076 USD in 2010 with a 5-6% increase from 1980 (1,909-3,884 USD). Also, it was found that, because of the low water prices, the economic values of domestic water are relatively low in some regions where water scarcity is one of the major societal problems (e.g., Middle Eastern and North African) compared to developed countries with a similar DWWC level. In such regions, toward sustainable water management, it is suggested to reconsider their policies adjusting water price and access to a fair water demand level. Therefore, the proposed framework would be beneficial for policymakers and international agencies to design sustainable water management systems.

Projections of the winter North Atlantic circulation exhibit large spread. Coupled Model Intercomparison Project archives typically provide only a few ensemble members per model, rendering it difficult to quantify reducible model structural uncertainty and irreducible internal variability (IV) in projections. We estimate using the Multi-Model Large Ensemble Archive that model structural differences explain two-thirds of the spread in late 21st century (2080-2099) projections of the winter North Atlantic Oscillation (NAO). This estimate is biased by systematic model errors in the forced NAO response and IV. Across the North Atlantic, the NAO explains a substantial fraction of the spread in mean sea level pressure (MSLP) projections due to IV, except in the central North Atlantic. Conversely, the spread in North Atlantic MSLP projections associated with model differences is largely unexplained by the NAO. Therefore, improving understanding of the NAO alone may not constrain the reducible uncertainty in North Atlantic MSLP projections.

Interplanetary shocks have been long known sources of suprathermal and energetic ions, and their origin will contribute in unveiling the origin of cosmic rays. Sudden ion intensity enhancements in the form of spikes that last anywhere between minutes to tens of seconds are observed during the passage of such shocks. Identification of spikes with peak intensities lasting ~1 min surveyed in over 304 shocks from January 2007 – December 2014 observed by the SEPT (Solar Electron and Proton Telescope) onboard STEREO (Solar Terrestrial Relations Observatory) A/B Spacecraft was performed using a new Python Code, followed by visual inspection. We also inspected the database of EPAM (Electron, Proton, and Alpha Monitor) onboard ACE (Advanced Composition Explorer) from 2003 to 2014. We present and discuss the statistical analysis of the shock spikes as a function of parameters such as shock normal angle and Mach number. The Python code can be used to analyse other databases such as WIND and this further paves the way for the employment of ML techniques to replace visual inspection. Such studies are vital in performing exhaustive and in-depth assessment of shock associated particle events.

The hydrologic dynamics and geomorphic evolution of watersheds are intimately coupled – runoff generation and water storage are controlled by topography and properties of the surface and subsurface, while also affecting the evolution of those properties over geologic time. However, the large disparity between their timescales has made it difficult to examine interdependent controls on emergent hydro-geomorphic properties, such as hillslope length, drainage density, extent of surface saturation. In this study, we develop a new model coupling hydrology and landscape evolution to explore how runoff generation affects long-term catchment evolution, and analyze numerical results using a nondimensional scaling framework. We focus on hydrologic processes dominating in humid climates where storm runoff primarily arises from shallow subsurface flow and from precipitation on saturated areas. The model solves hydraulic groundwater equations to predict the water table location given prescribed, constant groundwater recharge. Water in excess of the subsurface capacity for transport becomes overland flow, which generates shear stress on the surface and may detach and transport sediment. This affects the landscape form that in turn affects runoff generation. We show that (1) three dimensionless parameters describe the possible steady state landscapes that coevolve under steady recharge; (2) hillslope length increases with increasing transmissivity relative to the recharge rate; (3) three topographic metrics—steepness index, Laplacian curvature, and topographic index—provide a basis to recover key model parameters from topography (including subsurface transmissivity). These results open possibilities for topographic analysis of humid upland landscapes that could inform quantitative understanding of hydrological processes at the landscape scale.

Oceanic lithosphere created at mid-ocean ridges (MOR) is shaped by a complex interplay of magmatic, tectonic and hydrothermal processes. Where melt budget decreases at (ultra)slow spreading rates, the tectonic mode changes from normal to detachment faulting. We investigate an endmember type of detachment faulting, the so-called “flip-flop” detachment mode, observed exclusively at almost amagmatic sections of ultraslow-spreading MORs (e.g. Southwest Indian Ridge 62°E to 65°E): Active detachments migrate across the ridge axis towards the hanging wall side until they are superseded by a new on-axis fault of opposite polarity. Using a steady-state temperature field, numerical experiments by Bickert et al. (EPSL, 2020, 10.1016/j.epsl.2019.116048) show that an axial temperature maximum is essential to trigger flip-flop faults by focusing flexural strain in the footwall of the active fault. However, ridge segments without a significant melt budget are more likely to be in a transient thermal state controlled, at least in part, by the faulting dynamics themselves. In our study we investigate (1) which processes have first order control on the thermal structure of the lithosphere, (2) their respective feedbacks on the mechanical evolution of the lithosphere, and (3) how they facilitate flip-flop detachment faulting. We present results of 2-D thermo-mechanical numerical modelling including serpentinization reactions and dynamic grain size evolution. The model features a novel form of parametrized hydrothermal cooling along fault zones as well as the thermal and rheological effects of periodic sill intrusions. We find that both hydrothermal cooling of the active fault zone and periodic sill intrusions in the footwall are essential for entering the flip-flop detachment mode. Hydrothermal cooling of the fault zone pushes the temperature maximum into the footwall, while intrusions near the temperature maximum further weaken the rock and facilitate the opening of new faults with opposite polarity. We conclude that this interplay of hydrothermal cooling and magmatic intrusions is required to produce the observed flip-flop faulting. Our model allows us to put constraints on the magnitude of both processes, and we obtain reasonable melt budgets and hydrothermal heat fluxes only if both are considered.

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.

This study seeks to create a reconstruction of Holocene hydrologic variability of the Northern Coast Range of California using sediment cores collected from North Yolla Bolly Lake (Tehama County California). North Yolla Bolly (NYBL)Lake is a glacially formed-lake in the Northern Coast Range of California. At 40.2° N latitude, the lake is located at the average latitude of the California (CA) precipitation dipole, which is the leading mode of winter precipitation spatial variability in California (Wise 2010). As a result NYBL is well-situated for examining changes in the average position and strength of the CA precipitation dipole over the Holocene. In order to develop a record of Holocene Hydrologic variability, a multi indicator methodology was followed. The methods include: cm-scale magnetic susceptibility, organic and carbonate content via loss-on-ignition, grain size determination, C(org):N(total) ratios, and sub-cm scale XRF. Age control is based on AMS dates (n=15) taken from macroscopic organic material such as conifer needles, seeds, or charcoal. For this part of the project we focus on the interval between 10-2 kcal BP. Based on these data the Holocene is characterized by a wet (i.e. deep lake) early-to-mid Holocene (11.7-4.2 kcal BP) with a shift to drier (i.e. shallow eutrophic lake) during the late-Holocene (4.2-2 kcal BP). Superimposed on this millennial scale changes are variations in precipitation-related runoff as inferred from sand content, with intervals of major precipitation events (i.e., above average sand content) recorded at between 10-9.1, 8.3-8.28, 6.9-6.7, 5.3-5.2, 4.8-4.78, 4.3-4.0, 3.49-3.46, and 2.46-2.23 kcal BP. Conversely, there are several intervals of notable below-average runoff between 10.08-10.04, 9-8.5, 8.26-6.97, 6.5-5.5, 5.03-4.9, 4.73-4.33, 3.99-3.6, 3.42-2.49, and 2.2-2.03 kcal BP. Our interpretations will be compared to other hydrologic reconstructions from CA both to the north and south, such as Lake Elsinore (33.6° N), Lower Bear Lake (34.2° N), Silver Lake (35.3° N), Tulare Lake (36.0° N), Barley Lake (39.5° N), and Sanger Lake (41.9° N). Potential climatic forcings driving the inferred hydrologic changes are also examined, such as Milankovitch forcings, Pacific Ocean SSTs, and North Atlantic Meridional Overturning Circulation.

As global temperatures increase, Antarctica is likely to experience increased frequency, duration, and intensity of extreme temperature events. Here we investigate how the characteristics of summer extreme temperature events - heatwaves and incidence of melt days - may change over Antarctica using daily historical and SSP5-8.5 Coupled Model Intercomparison Project phase 6 (CMIP6) output from 1950-2099. CMIP6 models robustly project that Antarctica’s lowest elevation regions and the West Antarctic ice sheet will reach 0C for an average of 6-12 days during summer by 2099. Modelled summer heatwaves become more intense across the entire continent, but less frequent and shorter everywhere except the East Antarctic Plateau due to declining temperature variability as surface temperatures approach the melting point of ice. Our results imply that the increasing frequency of 0C days and greater heatwave intensity will contribute to increasing ice sheet surface melt and accelerating global sea level rise over the coming century.

The third phase of the Cloud Feedback Model Intercomparison Project requested that modeling centers perform a pair of simulations where the climate system is subjected to an abrupt change of the solar constant by +/- 4%. The forcing is designed to loosely match the amount of radiative forcing incurred by quadrupling atmospheric CO2 concentrations. Using these simulations, we examine how clouds respond to changes in solar forcing and act as a feedback on global surface temperature. Specifically, in this paper, we study the temperature mediated cloud changes that occur following an abrupt increase and decrease of the solar constant and compare with temperature mediated cloud changes that occur following quadrupling and halving of CO2. We seek to answer two primary questions: 1) How do cloud feedbacks differ in response to abrupt changes in CO2 and solar forcing? And 2) Are there symmetrical (equal and opposite) cloud feedbacks to an increase and a decrease in solar forcing? We find that temperature mediated cloud changes are similar from increasing solar and CO2 forcing, with the only robust difference being that there is a larger reduction of low cloud amount following solar forcing; and we find that cloud responses to warming and cooling are not symmetric, due primarily to non-linearity introduced by phase changes in mid-to-high latitude low clouds, and sea ice loss/formation.

Scientists generally agree that, by 2100, the annual extraction of an average of 3.3 Gt of carbon equivalent from the atmosphere will be necessary to limit the increase in global average temperature to 2°C relative to pre-industrial levels. A greenhouse gas (GHG) removal technology (GGRT) is one that can remove a GHG from the atmosphere. Enhanced silicate rock weathering for long-term CO2 sequestration has considerable potential as a GGRT, but depends on the availability of suitable rocks coupled with proximity to locations where it can be applied. Extracting, processing, transporting and applying ground rock to land consume energy and thus generate GHG emissions, which must be balanced against the sequestration potential. In this study, we i) assess the environmental impacts of the practice, using existing basalt rock quarrying in Sao Paulo (SP) state by considering the emissions associated with the rock extraction, comminution, transport and application through a Life Cycle Assessment (LCA) approach; ii) estimate the contribution of the different processes involved with soil carbonation and enhanced weathering and iii) assess the potential net CO2 removal of Sao Paulo agricultural land through soil carbonation and weathering of basalt rock. Our results show that enhanced weathering and carbonation respectively emit around 75 and 135 kg CO2eq per tonne of CO2eq removed (considering an average quarry to field distance of 65 km.) We underline transportation as the principal process negatively affecting the practice and establish a limiting road travel distance from quarry to field of 540 ± 65 km for carbonation and 990 ± 116 km for enhanced weathering. Above these distances, the GHG emissions exceed the potential sequestration. The application of crushed basalt at 1 t/ha to all of Sao Paulo State’s 12 million hectares of agricultural land could capture around 1.3 to 2.4 Mt CO2eq through carbonation and enhanced weathering, respectively. If 50 t/ha is applied, the sequestration potential could reach up to 40 to 76 % of the total Sao Paulo State emissions in 2016 through carbonation and enhanced weathering respectively, assuming no loss in the effectiveness of basalt at high application rates. This study lowers previous net sequestration estimates from Kantola et al. (2017) by around 50% and, as various techniques are increasingly promoted as efficient solutions to remove or sequester CO2, it emphasizes the need to consider the practice in its entirety to show the limitations and potential caveats. The holistic approach of LCA helps identify processes with the most impact and their significance. However, its accuracy and reliability is inevitably limited by the amount, quality and representativeness of the input data. Therefore, detailed studies on each process stage should be conducted to increase accuracy, focusing on local practices especially transport.

Mean monthly climatological mixed layer depth (MLD) combined with temperature, dissolved oxygen, and apparent oxygen utilization (AOU) are used to produce global estimates of the seasonal variability of ocean heat content anomaly (OHCA), O2 content anomaly (O2CA), and AOU content anomaly (ACA) in the surface mixed layer. Linear regression analyses show that the highest correlation occurs when O2CA lags OHCA by one month, whereas the highest correlation occurs when ACA lags OHCA by 2-3 months. The O2CA is negatively correlated, while the ACA is positively correlated with the OHCA in the mixed layer. The O2-heat ratio in the surface mixed layer is about -1.85 nmol/J in the subtropical and subpolar regions, which is on the same order of magnitude due to the O2 solubility effect alone. The solubility effect is the primary driver for the seasonal cycle of the O2 inventory in the mixed layer, and thus subject to changes in ocean warming. The 1-month lag between O2CA and OHCA suggests the O2 inventory quickly responds to heat content changes on seasonal time scales due to strong mixing in the mixed layer. The 2-3 month lag between ACA and OHCA suggests oxygen changes through biological activities take a longer time following OHC changes in relation to physical changes through O2 solubility. Our analysis indicates that the deoxygenation rate in the mixed layer, estimated from the regression analysis, is approximately -2.2 Tmol/year based on the O2-heat ratio in the mid-latitudes, accounting for 6±2% of the global deoxygenation for the time period 1955-2019.

Employing kinetic interface sensitive (KIS) tracers, we investigate three different types of glass-bead materials and two natural porous media systems to quantitatively characterize the influence of the porous-medium grain-, pore-size, and texture on the “mobile” interfacial area between an organic liquid and water. By interpreting the breakthrough curves (BTCs) of the reaction product of the KIS tracer hydrolysis we obtain a relationship for the specific interfacial area (IFA) and wetting saturation. The immiscible displacement process coupled with the reactive tracer transport across the fluid-fluid interface is simulated with a Darcy-scale numerical model. The results show that the current reactive transport model is not always capable to reproduce the breakthrough curves of tracer experiments and that a new theoretical framework is required. Total solid surface area of the grains, i.e., grain surface roughness, is shown to have an important influence on the capillary-associated IFA by comparing results obtained from experiments with spherical glass beads having very small or even no surface roughness and those obtained from experiments with the natural sand. Furthermore, a linear relationship between the mobile capillary associated IFA and the inverse mean grain diameter can be established. The results are compared with the data collected from literature measured with high-resolution microtomography and partitioning tracer methods. The capillary associated IFA values are consistently smaller because KIS tracers measure the mobile part of the interface. Through this study, the applicability range of the KIS tracers is considerably expanded and the confidence in the robustness of the method is improved.

A document by Wei Zhang. Click on the document to view its contents.

Spectral model turbulence analysis technique is widely used to derive kinetic energy dissipation rates of turbulent structures (ε) from different in situ measurements in the Earth’s atmosphere. Essence of this method is to fit a model spectrum to measured spectra of velocity or scalar quantity fluctuations and thereby to derive ε only from wavenumber dependence of turbulence spectra. Owing to simplicity of spectral model of Heisenberg (1948) its application dominates in the literature. Making use of direct numerical simulations (DNS) which are able to resolve turbulence spectra down to smallest scales in dissipation range, we advance the spectral model technique by quantifying uncertainties for two spectral models, the Heisenberg (1948) and the Tatarskii (1971) model, depending on 1) resolution of measurements, 2) stage of turbulence evolution, 3) model used. We show that model of Tatarskii 1971 can yield more accurate results and reveals higher sensitivity to lowest ε-values. This study shows that the spectral model technique can reliably derive ε if measured spectra only resolve half decade of power change within viscous (viscous-convective) subrange. In summary we give some practical recommendations how to derive most precise and detailed turbulence dissipation field from in situ measurements depending on their quality. We also supply program code of the spectral models used in this study in Python, IDL, and Matlab.

The development of semi-distributed hydrological models that reflect the dominant processes controlling streamflow spatial variability is a challenging task. In small, well-instrumented headwater catchments the model can be built taking advantage of knowledge derived from extensive fieldwork activities; that is, however, not possible in much larger catchments where, usually, these models are actually needed. To address this problem, we propose a new methodology where we analyze the correlations between hydrological signatures, catchments characteristics, and climatic indices to get insights about the hydrological functioning of the catchment and to guide the decisions involved in the development of a semi-distributed model. The methodology is tested in the Thur catchment (Switzerland, 1702 km2); in a first stage we show how to identify catchment characteristics and climatic indices that control streamflow variability; in a second stage, we use these findings to develop a set of model experiments aimed at determining an appropriate model representation for the catchment. Results show that only models that account for the influencing factors indicated by the correlation analysis are able to represent correctly the observed streamflow signatures, confirming our understanding of the processes happening in the catchment.

The Tonga-Kermadec subduction zone exhibits the fastest observed trench retreat (up to 16 cm/yr) and convergence rate (up to 23 cm/yr) near its northern end. However, it exhibits a paradox: despite this rapid trench retreat, the Tonga slab maintains a relatively steep dip angle (53°) above 400 km. The slab turns flat around 400 km, then steepening again until encountering a stagnant segment near the 670 km discontinuity. Despite its significance for understanding slab dynamics, no existing numerical model has successfully demonstrated how such a distinct slab morphology can be generated under the fast convergence. Our mantle convection models successfully reproduced the observed slab geometries while incorporating the observed subduction rate. A key element of achieving a qualitative match lies in the implementation of a hybrid velocity boundary condition, which proves crucial for handling the fast trench retreat. Our investigation explains how the detailed slab structure is highly sensitive to physical parameters including the seafloor age and the mantle viscosity. Notably, a nonlinear rheology, where dislocation creep reduces upper mantle viscosity under strong mantle flow, is essential. The weakened upper mantle allows for a faster slab sinking rate, which explains the large dip angle. Our findings highlight the utilizing rheological parameters that lead to extreme viscosity variations within numerical models to achieve an accurate representation of complex subduction systems like the Tonga-Kermadec zone. Our study opens new avenues for further study of ocean-ocean subduction systems, advancing our understanding of their role in shaping regional and global tectonics.

A document by Lonneke Roelofs. Click on the document to view its contents.

The fast-slipping (~ 14 cm/yr) Gofar transform fault (GTF) East Pacific Rise has three active segments G1 to G3 from east to west. These fault segments produce large earthquakes (MW ~ 6.0) quasi-periodically every five to six years (Figure 1). Interestingly, large earthquakes rupture the same 20-km long fault patches separated by a ~ 10-km rupture barrier zone, implying along-strike variations in fault zone material properties (McGuire et al. 2012). This further suggests that rupture patches and barrier zones remain stable over multiple seismic cycles. Here, we jointly invert P- and S-wave travel times, recorded at an ocean-bottom-seismometer (OBS) experiment along G1 between January 2019 and February 2020, to determine the 3-D seismic velocity structure of the area and relocate the local earthquakes. Our velocity models reveal a large low-velocity anomaly extending through the entire oceanic crust along G1 with some along-strike variations. We identify a 10 km-long rupture barrier zone, which is interpreted to be highly fractured with enhanced fluid circulation. We further suggest that the observed deep seismicity underlying the rupture barrier zone may indicate sea-water infiltration.  Lastly, we apply the same approach to the westernmost segment of the GTF and observe some similarities and differences between the two fault zone seismic velocity structures.