Preprints
There are 4724 Preprints listed.
Higher Long-Term Soil Moisture Increases Organic Carbon Accrual Through Microbial Conversion of Organic Inputs
Published: 2021-09-08
Subjects: Earth Sciences, Environmental Sciences, Physical Sciences and Mathematics
High long-term soil moisture may either stimulate or inhibit soil organic carbon (SOC) losses through changes to mineral and chemical composition, and resultant organo-mineral interactions. Yet, the trade-off between mineralization and accrual of SOC under long-term variation in unsaturated soil moisture remains an uncertainty. In this study, we tested the underexplored relationships between [...]
Changes in poleward atmospheric energy transport over a wide range of climates: Energetic and diffusive perspectives and a priori theories
Published: 2021-09-08
Subjects: Oceanography and Atmospheric Sciences and Meteorology
The midlatitude poleward atmospheric energy transport increases in radiatively forced simulations of warmed climates across a range of models from comprehensive coupled general circulation models (GCMs) to idealized aquaplanet moist GCMs to diffusive moist energy balance models. These increases have been rationalized from two perspectives. The energetic (or radiative) perspective takes the [...]
Interannual variability in methane and nitrous oxide concentrations and sea-air fluxes across the North American Arctic Ocean (2015–2019)
Published: 2021-09-08
Subjects: Physical Sciences and Mathematics
Between 2015–2018, we collected approximately 2000 water column measurements of methane (CH4) and nitrous oxide (N2O) concentrations in the North American Arctic Ocean during summer and early fall. We also obtained 25 measurements of CH4 and N2O concentrations in rivers along the Northwest Passage and Ellesmere Island in mid-summer 2017–2019. Our results show that N2O is generated in the highly [...]
Assessment pebble virtual velocity from combined active RFID fixed stations and geophones
Published: 2021-09-07
Subjects: Geomorphology, Geophysics and Seismology, Hydrology
The monitoring of coarse sediment transport is a domain teeming with technical innovations and methodological developments aimed at improving the characterization of bedload processes at different spatial and temporal scales. Radio frequency identification (RFID) technology has improved sediment tracking experiments, allowing the characterization of processes at the individual particle and [...]
High interstadial sea levels over the past 420ka from the Huon Peninsula, Papua New Guinea
Published: 2021-09-06
Subjects: Climate, Geology, Geomorphology, Oceanography, Tectonics and Structure
The history of sea level across the Quaternary is essential for assessing past and future climate. Global sea-level reconstructions are typically derived from oxygen isotope curves, but require calibration with geological constraints that are scarce prior to the last glacial cycle (>130 thousand years ago). Here we show that the coral reef terrace sequence at the Huon Peninsula (Papua New Guinea) [...]
Drone-mounted GPR surveying: flight-height considerations for diffraction-based velocity analysis
Published: 2021-09-06
Subjects: Earth Sciences, Geophysics and Seismology, Other Earth Sciences
Recent studies highlight the potential of the drone platform for ground-penetrating radar (GPR) surveying. Most guidance for optimizing drone flight heights is based on maximizing the image quality of target responses, but no study yet considers the impact on diffraction traveltimes. Strong GPR velocity contrasts across the air-ground interface introduce significant refraction effects that [...]
Lowermost mantle shear-velocity structure from hierarchical trans-dimensional Bayesian tomography
Published: 2021-09-06
Subjects: Earth Sciences, Physical Sciences and Mathematics
The core-mantle boundary (CMB) is the most extreme boundary within the Earth where the liquid, iron-rich outer core interacts with the rocky, silicate mantle. The nature of the lowermost mantle atop the CMB, and its role in mantle dynamics, is not completely understood. Various regional studies have documented significant heterogeneities at different spatial scales. While there is a consensus on [...]
Recharge observations indicate strengthened groundwater connection to surface fluxes
Published: 2021-09-03
Subjects: Physical Sciences and Mathematics
Groundwater is an invaluable global resource, but its long-term viability as a resource for consumption, agriculture, and ecosystems depends on precipitation recharging aquifers. How much precipitation recharges groundwaters varies enormously across Earth's surface, but recharge rates are uncertain because field observations are sparse and modeled global estimates remain largely unvalidated. Here [...]
CCREM: New reference Earth model from the global coda-correlation wavefield
Published: 2021-09-03
Subjects: Earth Sciences, Physical Sciences and Mathematics
The existing Earth reference models have provided an excellent one-dimensional representation of Earth’s properties as a function of its radius and explained many seismic observations in a broad frequency band. However, some discrepancies still exist among these models near the first-order discontinuities (e.g., the core-mantle and the inner-core boundaries) due to different datasets and [...]
Assessing pyrite-derived sulfate in the Mississippi River with four years of sulfur and triple-oxygen isotope data
Published: 2021-09-03
Subjects: Geochemistry
Riverine dissolved sulfate (SO42−) sulfur and oxygen isotope variations reflect their controls such as SO42− reduction and re-oxidation, and source mixing. However, unconstrained temporal variability of riverine SO42− isotope compositions due to short sampling durations may lead to mischaracterization of SO42− sources, particularly for the pyrite-derived sulfate load. We measured the sulfur and [...]
Worldwide moderate-resolution mapping of lake surface chl-a reveals variable responses to global change (1997-2020)
Published: 2021-09-02
Subjects: Fresh Water Studies
Anthropogenic activity is leading to widespread changes in lake water quality--a key contributor to socio-ecological health. But, the anthropogenic forces affecting lake water quality (climate change, land use change, and invasive species) are unevenly distributed across lakes, across the seasonal cycle, and across space within lakes, potentially leading to highly variable water quality responses [...]
Centennial- and orbital-scale erosion beneath the Greenland Ice Sheet
Published: 2021-09-01
Subjects: Earth Sciences, Geochemistry, Geomorphology, Glaciology
Erosion beneath glaciers and ice sheets is a fundamental Earth-surface process dictating landscape development, which in turn influences ice-flow dynamics and the climate sensitivity of ice masses. The rate at which subglacial erosion takes place, however, is notoriously difficult to observe because it occurs beneath modern glaciers in a largely inaccessible environment. Here, we present 1) [...]
Oxidized Mantle Sources of HIMU and EM-type Ocean Island Basalts
Published: 2021-09-01
Subjects: Earth Sciences, Geochemistry, Geology
Oxygen fugacity (fO2) is a fundamental variable in igneous petrology with utility as a potential tracer of recycled surficial materials in the sources of mantle-derived lavas. It has been postulated that ocean island basalts (OIB) have elevated fO2 relative to mid-ocean ridge basalts (MORB) owing to more oxidized source regions. To clarify this issue, trace-element systematics of olivine grains [...]
An overview of multimethod imaging approaches in environmental geophysics
Published: 2021-08-31
Subjects: Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics
Quantitative characterization of subsurface properties is critical for many environmental applications and serves as the basis to simulate and better understand dynamic subsurface processes. Geophysical imaging methods allow to image subsurface property distributions and monitor their spatio-temporal changes in a minimally invasive manner. While it is widely agreed upon that models integrating [...]
Pedogenic processes and the drying of Mars
Published: 2021-08-31
Subjects: Physical Sciences and Mathematics
What exactly caused Mars to lose its liquid water billions of years ago remains as one of the most enduring questions in planetary science. New insights from Mars suggest that crustal hydration – the formation of hydrated minerals during aqueous alteration of the crust – contributed to the long-term drying of the planet. Here, we advance the hypothesis that hydration of the Martian crust could [...]