bluuebunny/crossref_metadata_2025 huggingface dataset:
Submarine Groundwater and Vent Discharge in a Volcanic Area Associated With Coastal Acidification
Authors: Cardenas M. Bayani , Rodolfo Raymond S. , Lapus Mark R. , Cabria Hillel B. , Fullon Jose , Gojunco Gordos R. , Breecker Daniel O. , Cantarero Danica M. , Evaristo Jaivime , Siringan Fernando P. , Zhang Tongwei
Published: January 2020

We investigated submarine groundwater discharge (SGD) in a volcanic coastal area that hosts the world's most biodiverse reefs. Measurements of 222Rn activity in coastal seawater, a tracer for groundwater, indicated prevalent SGD. In areas where seawater 222Rn activity was generally higher, we discovered hydrothermal springs emitting acidic waters (pH ~5.4–6.0) and venting magmatic CO2 that brought local pCO2 levels up to 95,000 ppm. The collection of vents raised CO2 and lowered pH over 1–2 km of coastline. The hydrogen and oxygen isotope compositions of water and chloride concentration revealed that the springs discharge recirculated seawater mixed variably with terrestrial groundwater. Shallower springs and pore water have a higher proportion of terrestrial groundwater than deeper springs, which emit mostly recirculated seawater. This suggests that different SGD mechanisms are present. The SGD could be contributing to the evolution and function of the biodiverse ecosystem, but it also represents myriad pathways for contamination.
Microbial Methane From Methylphosphonate Isotopically Records Source
Authors: Taenzer L. , Carini P. C. , Masterson A. M. , Bourque B. , Gaube J. H. , Leavitt W. D.
Published: January 2020

Methane is a potent greenhouse gas commonly supersaturated in the oxic surfaces waters of oceans and lakes, yet canonical microbial methanogens are obligate anaerobes. One proposed methane production pathway involves microbial degradation of methylphosphonate (MPn), which can proceed in the presence of oxygen. Directly tracing dissolved methane to its source in oxic waters, however, remains a challenge. To address this knowledge gap, we quantified the carbon isotopic fractionation between substrate MPn and product methane (1.3‰) in lab experiments, which was 1 to 2 orders of magnitude smaller than canonical pathways of microbial methanogenesis (20 to 100‰). Together, these results indicated that microbial catabolism of MPn is a source of methane in surface oceans and lake waters, but to differentiate sources of MPn in nature a further accounting of all sources is necessary. Methane from this pathway must be considered in constraining the marine carbon cycle and methane budget.
Imaging Stress and Faulting Complexity Through Earthquake Waveform Similarity
Authors: Trugman Daniel T. , Ross Zachary E. , Johnson Paul A.
Published: January 2020

While the rupture processes of nearby earthquakes are often highly similar, characterizing the differences can provide insight into the complexity of the stress field and fault network in which the earthquakes occur. Here we perform a comprehensive analysis of earthquake waveform similarity to characterize rupture processes in the vicinity of Ridgecrest, California. We quantify how similar each earthquake is to neighboring events through cross correlation of full waveforms. The July 2019 Ridgecrest mainshocks impose a step reduction in earthquake similarity, which suggests variability in the residual stress field and activated fault structures on length scales of hundreds of meters or less. Among these aftershocks, we observe coherent spatial variations of earthquake similarity along the mainshock rupture trace, and document antisimilar aftershock pairs with waveforms that are nearly identical but with reversed polarity. These observations provide new, high‐resolution constraints on stress transfer and faulting complexity throughout the Ridgecrest earthquake sequence.
Burial and Origin of Permafrost‐Derived Carbon in the Nearshore Zone of the Southern Canadian Beaufort Sea
Authors: Grotheer H. , Meyer V. , Riedel T. , Pfalz G. , Mathieu L. , Hefter J. , Gentz T. , Lantuit H. , Mollenhauer G. , Fritz M.
Published: January 2020

Detailed organic geochemical and carbon isotopic (δ13C and Δ14C) analyses are performed on permafrost deposits affected by coastal erosion (Herschel Island, Canadian Beaufort Sea) and adjacent marine sediments (Herschel Basin) to understand the fate of organic carbon in Arctic nearshore environments. We use an end‐member model based on the carbon isotopic composition of bulk organic matter to identify sources of organic carbon. Monte Carlo simulations are applied to quantify the contribution of coastal permafrost erosion to the sedimentary carbon budget. The models suggest that ~40% of all carbon released by local coastal permafrost erosion is efficiently trapped and sequestered in the nearshore zone. This highlights the importance of sedimentary traps in environments such as basins, lagoons, troughs, and canyons for the carbon sequestration in previously poorly investigated, nearshore areas.
Variability in Marine Plankton Ecosystems Are Not Observed in Freshly Emitted Sea Spray Aerosol Over the North Atlantic Ocean
Authors: Bates T. S. , Quinn P. K. , Coffman D. J. , Johnson J. E. , Upchurch L. , Saliba G. , Lewis S. , Graff J. , Russell L. M. , Behrenfeld M. J.
Published: January 2020

Sea spray aerosol (SSA) consists of both sea salt and organic components. These aerosols affect Earth's climate by scattering solar radiation and by altering cloud properties. Here we present observations of SSA particles generated at sea using an over‐the‐side bubbling system (Sea Sweep) and an onboard plunging wave mesocosm (Marine Aerosol Reference Tank—MART) during five cruises in the North Atlantic. The cruises were timed to sample different stages of the North Atlantic plankton bloom and included transects from the oligotrophic Sargasso Sea to the biologically productive western subarctic. The results show that the North Atlantic plankton bloom has little effect on the emission flux, organic fraction, or cloud condensation nuclei (CCN) activity of SSA, and therefore, plankton ecosystems do not need to be included in modeling aerosol indirect effects of primary SSA in global climate models or in chemical transport models.
A Full‐Spectrum Bedrock Thermal Expansion Model and Its Impact on the Global Positioning System Height Time Series
Authors: Lei Jintao , Chen Wu , Li Zhao , Li Fei , Zhang Shengkai
Published: January 2020

Bedrock thermal expansion includes prominent seasonal (annual and semiannual) terms and intricate nonseasonal variations (high‐frequency change and transient signals). However, the nonseasonal variations are usually ignored in geodetic studies due to defects in analytical solutions. In this study, we calculate the full‐spectrum bedrock thermal expansion displacement using the skin temperature from the ERA5 reanalysis data set. The results show that the nonseasonal variations of bedrock thermal expansion, with a range (maximum minus minimum) reaching 3 mm in some regions, can be observed by geodetic instruments and thus cannot be ignored. Moreover, the mean power of the nonseasonal variations accounts for 20% of the entire thermal expansion. Without considering the influence of the nonseasonal variations, this “noise” would remain in the original observations and contaminate related geophysical inversions.
Surface Heat Flux Induced by Mesoscale Eddies Cools the Kuroshio‐Oyashio Extension Region
Authors: Shan Xuan , Jing Zhao , Gan Bolan , Wu Lixin , Chang Ping , Ma Xiaohui , Wang Shengpeng , Chen Zhaohui , Yang Haiyuan
Published: January 2020

Sea surface temperature (SST) is a key player in the air‐sea interaction, influencing storm tracks, atmospheric circulation, and climate modes. Although prevailing theories attribute variations of large‐scale SST to atmosphere forcing and ocean internal dynamics, we find that sea surface heat flux anomalies induced by mesoscale eddies exert significant influences on the upper‐ocean heat budget in the Kuroshio‐Oyashio extension region. Despite making nearly no contribution to the net heat exchange at the air‐sea interface, the eddy‐induced heat flux anomalies weaken the thermal stratification in the upper ocean and result in pronounced sea surface cooling. The underlying dynamics is the efficient dissipation of eddy potential energy by eddy‐induced heat flux anomalies. This makes the conversion of eddy potential energy to eddy kinetic energy significantly reduced, corresponding to a weaker eddy‐induced restratification flux. The finding complements the existing theories on large‐scale SST dynamics and has important implications for understanding extratropical climate variability.
10Be/9Be Ratios Reveal Marine Authigenic Clay Formation
Authors: Bernhardt A. , Oelze M. , Bouchez J. , von Blanckenburg F. , Mohtadi M. , Christl M. , Wittmann H.
Published: January 2020

As reverse weathering has been shown to impact long‐term changes in atmospheric CO2 levels, it is crucial to develop quantitative tools to reconstruct marine authigenic clay formation. We explored the potential of the beryllium (Be) isotope ratio (10Be/9Be) recorded in marine clay‐sized sediment to track neoformation of authigenic clays. The power of such proxy relies on the orders‐of‐magnitude difference in 10Be/9Be ratios between continental Be and Be dissolved in seawater. On marine sediments collected along a Chilean margin transect we chemically extracted reactive phases and separated the clay‐sized fraction to compare the riverine and marine 10Be/9Be ratio of this fraction. 10Be/9Be ratios increase fourfold from riverine to marine sediment. We attribute this increase to the incorporation of Be high in 10Be/9Be from dissolved biogenic opal, which also serves as a Si‐source for the precipitation of marine authigenic clays. 10Be/9Be ratios thus sensitively track reverse‐weathering reactions forming marine authigenic clays.
“Garnet” Lherzolites in the Purang Ophiolite, Tibet: Evidence for Exhumation of Deep Oceanic Lithospheric Mantle
Authors: Gong Xiao‐Han , Shi Ren‐Deng , Xu Ji‐Feng , Huang Qi‐Shuai , Huang Xiao‐Xiao , Su Ben‐Xun
Published: January 2020

Ophiolites commonly sample the uppermost parts (15–20 km) of fossil oceanic lithosphere. However, in recent years, the documentation of diamonds, super‐reducing (e.g., SiC), and other “unusual” minerals from several ophiolitic peridotites and chromitites (e.g., Tibet and the Polar Urals) has caused debate concerning their origin (i.e., deep vs. shallower upper mantle). Here we report on symplectite‐bearing lherzolites from the Purang ophiolite in Tibet, which preserve the first compelling evidence of garnet‐facies protoliths. These lherzolites were previously formed and stabilized at a depth of ~85–100 km, which is much deeper than generally suggested and approaches the depth (~120 km) required for stabilizing the diamonds. Combining with other key observations, we suggest the Purang garnet‐bearing peridotites may represent mixtures of oceanic lithosphere domains with diverse origins; they were rapidly exhumed at a variety of mantle depths within a subduction channel associated with oceanic slab retreat.
Robust Increases in Extreme Pacific North American Events Under Greenhouse Warming
Authors: Liu Zhongfang , He Xiaogang , Ma Wentao , Wang Yue
Published: January 2020

The Pacific North American (PNA) pattern is an internal mode of the Northern Hemisphere atmosphere, which strongly affects the hydroclimate and ecosystems of the Pacific‐North American sector. Recent studies have suggested a more positive PNA pattern in response to greenhouse warming, but how extreme PNA events will change remains unclear. Based on results from the Coupled Model Intercomparison Project Phase 5 multimodel ensemble, we find a 50% increase in the frequency of extreme positive PNA events and a 32% increase in extreme negative PNA events in the 21st century relative to the twentieth century. The increased frequency arises from a shift toward a more positive PNA pattern and is enhanced by more frequent ENSO events under greenhouse warming. Our study suggests that a continued increase in greenhouse‐gas emissions is likely to cause increased occurrence of extreme PNA events, thus increasing the risk of extreme weather and climate in North America.
The Far Ultraviolet Signatures of Conjugate Photoelectrons Seen by the Special Sensor Ultraviolet Spectrographic Imager
Authors: Kil Hyosub , Schaefer Robert K. , Paxton Larry J. , Jee Geonhwa
Published: January 2020

This study investigates the origin of anomalous far ultraviolet emissions observed at night at the subauroral region by the Special Sensor Ultraviolet Spectrographic Imager on board the Defense Meteorological Satellite System‐F16 satellite. The global distribution of the anomalous emission is derived using the measurements of the oxygen atom 130.4‐nm emission in 2017. Our results show the extension of the anomalous emission from high latitudes to middle latitudes in the Northern American‐Atlantic sector during the December solstice and in the Southern Australia‐New Zealand sector during the June solstice. These observations indicate that the anomalous emission occurs in the winter hemisphere and is pronounced at locations close to the magnetic poles. The good agreement between the morphology of the anomalous emission and the predicted distribution of conjugate photoelectrons leads to the conclusion that the anomalous emissions are the signatures of conjugate photoelectrons.
Is Nightside Outflow Required to Induce Magnetospheric Sawtooth Oscillations
Authors: Zhang Binzheng , Brambles Oliver J. , Lotko William , Lyon John G.
Published: January 2020

Ionospheric outflow plays an important role in the mass coupling between the ionosphere and the coupled solar wind‐magnetosphere system. Previous modeling studies have shown that outflowing ionospheric ions may induce magnetospheric sawtooth oscillations through mass loading of the magnetotail, stretching the magnetic field lines, and reducing nightside reconnection. The spatial distribution of polar cap outflow in these simulation studies produces significant outflow in the auroral oval and lacks a distinct cusp source. Thus, the question arises whether cusp outflow can induce sawtooth oscillations. We show controlled numerical experiments with magnetospheric sawtooth oscillations induced by an idealized cusp outflow for driving conditions representative of the interaction of an interplanetary coronal mass ejection with Earth's magnetosphere. The analysis shows that although only a small portion (10%) of the cusp outflow is entrained within the plasma sheet, it is effective in inducing magnetospheric sawtooth oscillations, similar to previous experiments.