bluuebunny/crossref_metadata_2025_split huggingface dataset:
Patterns and potential drivers of declining oxygen content along the southern California coast
Authors: Booth J. A. T. , Woodson C. B. , Sutula M. , Micheli F. , Weisberg S. B. , Bograd S. J. , Steele A. , Schoen J. , Crowder L. B. 
Published: June 2014

Here we examine a 50+ yr data set from a regionally coordinated southern California water quality monitoring program to assess temporal trends and determine whether nearshore waters are exhibiting changes in dissolved oxygen (DO) content similar to those reported offshore. DO in sub—mixed layer nearshore waters (< 10 km from shore) have declined up to four times faster than reported for offshore waters over the last 15 yr. These trends were evident over depth, and along isopycnals. They have no precedent over the past 50 yr and do not appear to be attributable primarily to large‐scale climate variability in ocean DO. Coastal biophysical processes, including increased phytoplankton biomass in surface waters, are likely contributing to the recent elevated rate of DO decline in nearshore waters, as evidenced by higher rates of increase in apparent oxygen utilization. It is unclear whether these processes result from upwelling‐derived or anthropogenic nutrient inputs.
Thermal structure and response to long‐term climatic changes in Lake Qiandaohu, a deep subtropical reservoir in China
Authors: Zhang Yunlin , Wu Zhixu , Liu Mingliang , He Jianbo , Shi Kun , Wang Mingzhu , Yu Zuoming 
Published: June 2014

Using the vertical temperature profiles of Lake Qiandaohu from January 2010 to April 2013, we evaluated the monthly and seasonal variations of water temperature and thermocline parameters, and developed empirical models among thermocline depth (TD), thickness (TT), and strength (TS). We also developed empirical models between TD, TT, TS, and surface‐water temperature (0–2 m) (T0–2 m), and transparency (Secchi disk depth, SDD). Additionally, we assessed the changes in TD, TT, and TS over the past 62 yr, based on our empirical models, air temperature data from 1951 to 2012, and SDD data from 1987 to 2012. Lake Qiandaohu is warm monomictic, with a long period of thermal stratification from April until January, and only a short period of mixing in the winter or spring (February or March). There were significant correlations between SDD and TD (positive), and between SDD and TT (negative). There was a significant negative correlation between T0–2 m and TD during the stratification weakness period (July—February), and a significant positive correlation between T0–2 m and TT for all data, including the stratification formation and weakness periods. Air temperature near the lake rose 1.2°C between 1951 and 2012, corresponding to a 0.8°C increase in T0–2 m, and a 0.78 m decrease in SDD between 1987 and 2012. The increase in air temperature and the decrease in SDD caused a decrease in TD and an increase in TT, facilitating the thermal stratification and stability of the lake; therefore, climate warming has had a significant effect on the thermal regime of Lake Qiandaohu.
Salt marsh tidal exchange increases residence time of silica in estuaries
Authors: Carey J. C. , Fulweiler R. W. 
Published: June 2014

We present flux measurements of dissolved silicon (DSi), biogenic Si (BSi), and dissolved inorganic nitrogen (DIN) and phosphorus (DIP) on a temperate salt marsh in Narragansett Bay, Rhode Island, over neap, mid, and spring tide cycles during the spring and the summer seasons to determine the stoichiometry of marsh tidal export and the potential effect on Si availability in the receiving estuary. During the spring, when incoming waters were depleted in DSi (average 1.7 µmol L−1), the marsh was a net sink of BSi (132 mol h−1) and a source of DSi (31 mol h−1) to the estuary. During this period, the DIN : DSi ratio of ebbing water was more than five times lower than that of flood water. Together, these data indicate that marsh nutrient fluxes “outwell” nutrients in ratios that support spring diatom growth in Narragansett Bay. However, during the entire sampling period the marsh served as a net sink for both DSi and BSi, importing, on average, 14 mol DSi h−1 and 86 mol BSi h−1. We hypothesize that the net import and retention of Si by salt marshes provides a previously overlooked ecosystem service of increasing the residence time of Si in estuarine systems. In the absence of salt marshes, we calculate that 5.1 × 104 kmol of Si would be exported from the estuary during the growing season, decreasing the availability of Si in the system and having direct repercussions for phytoplankton species composition in nearby estuarine waters.
Wave‐induced transport and vertical mixing of pelagic eggs and larvae
Authors: Röhrs Johannes , Christensen Kai Håkon , Vikebø Frode , Sundby Svein , Saetra Øyvind , Broström Göran 
Published: June 2014

The transport of pelagic plankton by wind‐driven ocean currents and surface gravity waves is investigated for the example of Northeast Arctic cod eggs and larvae on the coast of northern Norway. Previous studies indicate that the wave‐induced drift (i.e., Stokes drift) is relevant for the transport of particles in the upper ocean. We use an ocean general circulation model together with a numerical wave prediction model and a Lagrangian particle tracking model to calculate trajectories of fish eggs and larvae. Waves are considered not only for particle drift but also for the air—sea momentum flux, its contribution to the Coriolis force, and vertical mixing. The sample species provides the advantage that many of its physical and behavioral properties are well known (e.g., egg buoyancy), allowing investigation of vertical particle displacement by turbulent mixing in response to wind forcing and wave breaking. The approach accounting for particle mixing by breaking waves enhances agreement between observed and modeled egg profiles. Results also show a general shoreward transport of particles by the Stokes drift. This wave drift exhibits a more constant direction than the Eulerian current and hence stabilizes particle diffusion to favor a dominant direction. For the case of Northeast Arctic cod, waves concentrated model eggs and larvae on average 1.5 km closer to shore, which is 20% of their total distance to the coast. This increases the residence time of first‐feeding larvae close to the spawning areas compared to earlier models.
Assessing the drivers of spatial variation in thermal forcing across a nearshore reef system and implications for coral bleaching
Authors: Falter James L. , Zhang Zhenlin , Lowe Ryan J. , McGregor Frazer , Keesing John , McCulloch Malcolm T. 
Published: June 2014

We examined the seasonal and spatial variability in the temperatures of nearshore reef waters over 19 months across Coral Bay at Ningaloo Reef, Western Australia. Local deviations in the mean daily temperature of nearshore reef waters from offshore values (ΔT) were a linear function of the combined effect of net atmospheric heating (Qnet) and offshore wave height and period. Whereas intra‐annual variation in local heat exchange was driven mainly by seasonal changes in shortwave radiation, intra‐annual variation in local cooling was driven mostly by changes in relative humidity (r2 = 0.60) and wind speed (r2 = 0.31) that exhibited no apparent seasonality. We demonstrate good agreement between nearshore reef temperatures modeled from offshore sea surface temperatures, offshore wave forcing, and local atmospheric heat fluxes with observed temperatures using a simple linear model (r2 = 0.31–0.69, root‐mean‐square error = 0.4–0.9°C). Using these modeled nearshore reef temperature records, we show that thermal stresses across the reef reached between 16°C weeks and 22°C weeks in the summer of 2011 when a mass coral bleaching event was reported, and between 12°C weeks and 13°C weeks in the following summer of 2012 when no mass bleaching was reported. After compensating for differences between observed and modeled thermal stresses, we found that maximum thermal stresses across the reef likely reached as high as 18–34°C weeks in the summer of 2011. The approach used here could thus improve our ability to predict spatial variation in thermal stress and bleaching across other wave‐driven nearshore reef systems.
The effect of organic carbon on fixed nitrogen loss in the eastern tropical South Pacific and Arabian Sea oxygen deficient zones
Authors: Chang Bonnie X. , Rich Jeremy R. , Jayakumar Amal , Naik Hema , Pratihary Anil K. , Keil Richard G. , Ward Bess B. , Devol Allan H. 
Published: June 2014

The three major oxygen deficient zones (ODZs) of the world oceans (eastern tropical North and South Pacific (ETNP and ETSP, respectively), and Arabian Sea (AS) host the vast majority of pelagic fixed nitrogen (N) loss and up to half of total marine N loss. The input of organic matter is an important control on the absolute and relative importance of the two main pathways of N removal (denitrification and anammox). We investigated the response of N loss in the ETSP and AS ODZs to additions of organic matter in the form of glucose and naturally derived dissolved and particulate organic matter (DOM and POM, respectively). In the ETSP ODZ, the addition of glucose stimulated denitrification (1.6‐fold increase after 5 d) but not anammox (14‐fold decrease after 5 d). In the AS ODZ, only POM, not DOM, significantly increased rates of denitrification at the base of the oxycline (5.4–6.4‐fold increase after 2 d), but not at the secondary nitrite maximum. These results suggest that denitrification was generally limited by organic matter supply at the time of this study in both the ETSP and AS ODZs, although the lability of the organic matter supplied was important. Interestingly, 15N2 produced in ETSP and AS incubations was not binomially distributed relative to the reactants after the influence of anammox was taken into account, suggesting an unknown production mechanism or pathway of N removal.
The frequency of connection of coastal water bodies to the ocean predicts Carcinus maenas invasion
Authors: Garside C. J. , Glasby T. M. , Coleman M. A. , Kelaher B. P. , Bishop M. J. 
Published: June 2014

Semi‐enclosed coastal water bodies range from permanently open estuaries to lagoons that are periodically isolated from the ocean. The proportion of time these are connected to the ocean may influence biological invasions by determining recruitment opportunities, environmental conditions, and available biogenic habitats. Along the south coast of New South Wales, Australia, we tested whether the abundance and persistence of the nonnative crab, Carcinus maenas, varies among coastal water bodies according to the proportion of time their entrance is open to the ocean. In quarterly sampling over 2 yr in 14 estuaries and lagoons varying in the percentage of time they were closed to the ocean from 0–100% crab presence and abundance was correlated with the proportion of time the entrances were open. Crabs were absent from lagoons with entrances closed to the ocean > 60% of the time and consistently detected in open estuaries. Crab abundance increased with the connectivity of coastal water bodies to the ocean and was influenced by habitat availability. In water bodies where conditions supported mangroves, this habitat contained higher abundances of crabs than seagrass, saltmarsh, oyster habitat, or bare substrate. Entrance morphology initially predicts the likelihood of the crabs' arrival by influencing their population connectivity between estuaries or lagoons and the open coast, and the probability of establishment by influencing abiotic conditions. Entrance morphology may also affect crab abundance by influencing the available habitats. Hence, the geomorphology of semi‐enclosed coastal water bodies should be considered when managing marine bioinvasions.
Formation and erosion of biogeomorphological structures: A model study on the tube‐building polychaete Lanice conchilega
Authors: Borsje Bas W. , Bouma Tjeerd J. , Rabaut Marijn , Herman Peter M. J. , Hulscher Suzanne J. M. H. 
Published: June 2014

We study how organism traits and population densities of ecosystem engineering species, in combination with environmental factors, affect the formation and erosion rates of biogeomorphological structures, and focus on the widely distributed marine tube‐building polychaete Lanice conchilega, which lives in patches that form mounds up to 80 cm high in soft‐bottom sediments. We modeled the tube‐building worms as thin solid piles that affect drag and turbulence, and thereby the local sediment dynamics and thus mound dynamics. Hydrodynamic model predictions showed good agreement with flume experiments for flow‐velocity adaptations both within and in front of a patch of tube‐building worms. The modeled equilibrium mound height increased with the organism trait “tube length,” and with population density, but was only little affected by the strength of the tidal current, water depth, and grain size. In all cases, the modeled mound heights were within the range of the mound heights observed in the field. The effect of the tube‐building worm L. conchilega reached beyond the spatial scale of their biogenic structures, and persisted longer than the lifetime of the engineering organism itself.
The evolution of tides and tidal dissipation over the past 21,000 years
Authors: Wilmes S.‐B. , Green J. A. M. 
Published: June 2014

AbstractThe 120 m sea‐level drop during the Last Glacial Maximum (LGM; 18–22 kyr BP) had a profound impact on the global tides and lead to an increased tidal dissipation rate, especially in the North Atlantic. Here, we present new simulations of the evolution of the global tides from the LGM to present for the dominating diurnal and semidiurnal constituents. The simulations are undertaken in time slices spanning 500–1000 years. Due to uncertainties in the location of the grounding line of the Antarctic ice sheets during the last glacial, simulations are carried out for two different grounding line scenarios. Our results replicate previously reported enhancements in dissipation and amplitudes of the semidiurnal tide during LGM and subsequent deglaciation, and they provide a detailed picture of the large global changes in M2 tidal dynamics occurring over the deglaciation period. We show that Antarctic ice dynamics and the associated grounding line location have a large influence on global semidiurnal tides, whereas the diurnal tides mainly experience regional changes and are not impacted by grounding line shifts in Antarctica.
How much does heat content of the western tropical Pacific Ocean modulate the South China Sea summer monsoon onset in the last four decades?
Authors: Feng Junqiao , Hu Dunxin 
Published: June 2014

AbstractThe role of the western tropical Pacific Ocean heat content in the South China Sea summer monsoon (SCSSM) onset is investigated in the present paper, by using atmospheric data from NCEP and ocean subsurface temperature data from Japan Meteorology Agency. It is showed from the result that the heat content (HC) of the upper 400 m layer in the western tropical Pacific (WTP), especially in the region of (130°E–150°E, 0°N–14°N) in the last four decades, is a good predictive indicator for the SCSSM onset. Positive (negative) HC anomalies can induce a strong (weak) convection over the WTP, leading to stronger (weaker) Walker circulation and weaker (stronger) western North Pacific subtropical high (WNPSH) in the boreal spring. Consequently, the anomalous westerly (easterly) in the tropical Indian Ocean is favorable (unfavorable) for the airflow into the SCS and for an early (late) WNPSH retreat from the SCS and hence for an early (late) SCSSM onset. It is elucidated that the long‐term trend of SCSSM onset changes its sign around 1993/94 from decline to rise, which is responding and attributed to the WTP HC trend. During the period of 1971–1993, the WTP HC shows a significant decrease trend. In particular, a significant decline trend is observed in the HC difference between the WTP and western tropical Indian Ocean, which causes an easterly trend in the SCS and strengthened WNPSH trend, leading to a late onset trend of SCSSM. The situation is reverse after 1993/94.
Seasonal soil moisture patterns: Controlling transit time distributions in a forested headwater catchment
Authors: Stockinger Michael Paul , Bogena Heye Reemt , Lücke Andreas , Diekkrüger Bernd , Weiler Markus , Vereecken Harry 
Published: June 2014

AbstractThe Transit Time Distribution (TTD) of a catchment is frequently used for understanding flow paths, storage characteristics, and runoff sources. Despite previous studies, the connections between catchment characteristics and TTDs are still not fully understood. We present results from a 2 year stable isotope tracer investigation in the forested Wüstebach headwater catchment (38.5 ha), including precipitation, stream, and tributary locations. We used the gauged outlet to determine effective precipitation (peff), subdivided for wet and dry catchment state, and assumed it to be spatially uniform. We then calculated TTDs of 14 ungauged stream and tributary locations where stable isotope tracer information was available and compared them to respective subcatchment areas and the proportion of riparian zone within the subcatchments. Our approach gave insight into the spatial heterogeneity of TTDs along the Wüstebach River. We found that hydrological hillslope‐riparian zone disconnection was an important factor, as the catchment shifted between two distinct, time‐variant hydrological responses that were governed by seasonal changes of overall catchment wetness. The difference in hydrological behavior of the riparian zone and hillslopes could explain the often encountered “old water phenomenon,” where considerable amounts of old water quickly appear as runoff. TTD results showed a negative correlation between riparian zone proportion and Mean Transit Time (MTT), corroborated by the dense network of soil water content measurements. No correlation between subcatchment size and MTT was found.
Modeling biofilm dynamics and hydraulic properties in variably saturated soils using a channel network model
Authors: Rosenzweig Ravid , Furman Alex , Dosoretz Carlos , Shavit Uri 
Published: June 2014

AbstractBiofilm effects on water flow in unsaturated environments have largely been ignored in the past. However, intensive engineered systems that involve elevated organic loads such as wastewater irrigation, effluent recharge, and bioremediation processes make understanding how biofilms affect flow highly important. In the current work, we present a channel‐network model that incorporates water flow, substrate transport, and biofilm dynamics to simulate the alteration of soil hydraulic properties, namely water retention and conductivity. The change in hydraulic properties due to biofilm growth is not trivial and depends highly on the spatial distribution of the biofilm development. Our results indicate that the substrate mass transfer coefficient across the water‐biofilm interface dominates the spatiotemporal distribution of biofilm. High mass transfer coefficients lead to uncontrolled biofilm growth close to the substrate source, resulting in preferential clogging of the soil. Low mass transfer coefficients, on the other hand, lead to a more uniform biofilm distribution. The first scenario leads to a dramatic reduction of the hydraulic conductivity with almost no change in water retention, whereas the second scenario has a smaller effect on conductivity but a larger influence on retention. The current modeling approach identifies key factors that still need to be studied and opens the way for simulation and optimization of processes involving significant biological activity in unsaturated soils.
Why are the δ13Corg values in Phanerozoic black shales more negative than in modern marine organic matter?
Authors: Meyers Philip A. 
Published: June 2014

AbstractThe δ13Corg values of Phanerozoic black shales average −27‰, whereas those of modern marine organic matter average −20‰. The black shale isotopic values mimic those of continental organic matter, yet their organic geochemical properties mandate that they contain predominantly marine organic matter. Hypotheses that proposed to explain the low δ13C values of black shales include diagenetic losses of isotopically heavier organic matter components, releases of isotopically light carbon from methane clathrates or extensive magmatic events, greater photosynthetic discrimination against 13C during times of higher atmospheric pCO2, and greenhouse climate stratification of the surface ocean that magnified photic zone recycling of isotopically light organic matter. Although the last possibility seems contrary to the vertical mixing that leads to the high productivity of modern oceanic upwelling systems, it is consistent with the strongly stratified conditions that accompanied deposition of the organic carbon‐rich Pliocene‐Pleistocene sapropels of the Mediterranean Sea. Because most Phanerozoic black shales contain evidence of photic zone anoxia similar to the sapropels, well‐developed surface stratification of the oceans was likely involved in their formation. Existence of isotopically light land plant organic matter during several episodes of extensive magmatism that accompanied black shale deposition implies massive release of mantle CO2 that added to the greenhouse conditions that favored oceanic stratification. The 13C depletion common to most Phanerozoic black shales apparently resulted from a greenhouse climate associated with elevated atmospheric pCO2 that led to a strongly stratified ocean and photic zone recycling of organic matter in, augmented by magmatic CO2 releases.
Full‐halo coronal mass ejections: Arrival at the Earth
Authors: Shen Chenglong , Wang Yuming , Pan Zonghao , Miao Bin , Ye Pinzhong , Wang S. 
Published: June 2014

AbstractA geomagnetic storm is mainly caused by a frontside coronal mass ejection (CME) hitting the Earth and then interacting with the magnetosphere. However, not all frontside CMEs can hit the Earth. Thus, which CMEs hit the Earth and when they do so are important issues in the study and forecasting of space weather. In our previous work, the deprojected parameters of the full‐halo coronal mass ejections (FHCMEs) that occurred from 1 March 2007 to 31 May 2012 were estimated, and there are 39 frontside events that could be fitted by the Graduated Cylindrical Shell model. In this work, we continue to study whether and when these frontside FHCMEs (FFHCMEs) hit the Earth. It is found that 59% of these FFHCMEs hit the Earth, and for central events, whose deviation angles ϵ, which are the angles between the propagation direction and the Sun‐Earth line, are smaller than 45°, the fraction increases to 75%. After checking the deprojected angular widths of the CMEs, we found that all of the Earth‐encountered CMEs satisfy a simple criterion that the angular width (ω) is larger than twice the deviation angle (ϵ). This result suggests that some simple criteria can be used to forecast whether a CME could hit the Earth. Furthermore, for Earth‐encountered CMEs, the transit time is found to be roughly anticorrelated with the deprojected velocity, but some events significantly deviate from the linearity. For CMEs with similar velocities, the differences of their transit times can be up to several days. Such deviation is further demonstrated to be mainly caused by the CME geometry and propagation direction, which are essential in the forecasting of CME arrival.