Today, climate change is affecting virtually all terrestrial and nearshore settings. This commentary discusses the challenges of measuring climate-driven physical landscape responses to modern global warming: short and incomplete data records, land use and seismicity masking climatic effects, biases in data availability and resolution, and signal attenuation in sedimentary systems. We identify opportunities to learn from historical and paleo data, select especially sensitive study sites, and report null results to better characterize the extent and nuances of climate-change effects. We then discuss efforts to improve attribution practices, which will lead to better predictive capabilities. We encourage the Earth-science community to prioritize scientific research on climate-driven physical landscape changes so that societies will be better prepared to manage the effects on health and safety, infrastructure, water–food–energy security, economics, and ecosystems that follow from climate-driven physical landscape change.
Abstract Understanding the mechanisms controlling downstream water-level variations after the operation of the Three Gorges Dam is important for riverine flood and drought management. However, our quantitative understanding of the multiple controls of river morphology, vegetation, and floodplain resistance on water levels in the Middle Yangtze River (MYR) remains limited. Here, we analyze changes in river channels and floodplain resistance in the MYR using 450 cross-sectional profiles as well as data on discharge, water levels, sediment, and satellite images from 2003 to 2015. Results show an overall decline in low-flow water-levels (at a given small discharge) due to severe incisions of low-flow channels caused by a sharp reduction of ?90% in sediment loads from 1950?2002 to 2003?2020. In contrast, high-flow water-levels (at a given large discharge) display minor changes. Our analysis shows that the notably increased floodplain resistance due to vegetation growth is likely the dominant factor elevating flood water-levels, followed by riverbed coarsening and greater fluctuations in the river longitudinal profiles. Our findings further the understanding of downstream geomorphic response to dam operation and their impacts on water levels and have important implications for riverine flood management in dammed river systems.
Dams alter downstream river flow and sediment regimes, causing significant changes in river morphologies. The middle Yangtze River downstream of the Three Gorges Dam (TGD) has experienced rapid erosion in recent years, and the associated morphodynamic changes have negatively impacted the bank stability, navigation waterways and ecological functioning. Earlier studies have analyzed recent channel adjustments in the Yangtze River; however, our understanding of changes in the bar morphodynamics remains incomplete. In this study, we collected and analyzed flow and sediment data (1991∼2016) and river bathymetry data (1975∼2017) and investigated the mechanisms of bar adjustments along the Jingjiang Reach in the post-TGD period. The results indicate that most steady bars with a higher elevation and better vegetation coverage have experienced lateral erosion, while their elevations have remained stable overall. The unvegetated migrating bars with a lower elevation have experienced severe surficial erosion and area shrinkage. A new assessment method of the dominant discharge range on downstream bars is provided after dam closure. The new dominant discharge range that determines bar adjustments corresponds to the flow stages between the submersion of migrating bars (∼12,500 m3/s) and the overtopping of vegetated steady bars (∼27,500 m3/s) in the Jingjiang Reach. A quantitative relationship exists between bar erosion in response to changed dominant discharge regimes and sediment decline. The significant bar erosion after the operation of the TGD can be attributed to the increased flow duration and the sharp decline in the suspended sediment concentration (SSC) of the dominant discharge range, and changes in SSCs play a primary role. The bar area will decrease by ∼0.003 km2 when the annual cumulative duration of the dominant discharge increases by one day and by ∼0.234 km2 when the annual average SSC of the dominant discharge decreases by 0.01 kg/m3. Furthermore, vegetation encroachment and colonization play a positive role in stabilizing bar morphologies and limiting surficial erosion, whereas vegetation cannot prevent the lateral erosion of steady bars. These findings suggest that multiple controls, including flow, sediment and vegetation, shape the evolution of fluvial bars and have important implications for river management and ecological evaluation in response to the operation of large dams.
This study examines whether people smoked more under the Coronavirus Disease 2019 (COVID-19) closure policies which trapped them at home with their families. In such circumstances, the pleasure from smoking could be more tempting than usual, but at the same time smokers’ families are more likely to be victims of passive smoking. This study uses temporal and regional variations in policy strengths with data from the Oxford COVID-19 Government Response Tracker project (OxCGRT) to examine the impact of COVID-19 closure policies on smoking behaviors. With longitudinal data from the China Family Panel Studies (CFPS) in 2018 and 2020, we find diminished smoking behaviors among Chinese male adults when the government implemented strict public health policies for the COVID-19 pandemic. People with more conscientiousness personality traits or stronger pro-family attitudes tend to smoke less as policy stringency increases.
The literature on microcredit programs has largely focused on positive socioeconomic outcomes and low accessibility issues in farming areas and has provided less insight into the effects of easily acquired microcredit in pastoral areas. Using a case study approach, and econometric models, this paper addresses this gap by examining why and how easily acquired microcredit loans in Inner Mongolian pastoral areas increase the risk to the financial security of households or livelihood risk. Results show that existing microcredit programs increase livelihood risk because loan and repayment requirements do not align with the husbandry production cycle of contemporary Inner Mongolian pastoralists. This misalignment forces pastoralists to borrow from usurers to repay bank loans. Furthermore, households that need to borrow from usurers typically own smaller numbers of livestock and are less likely to be able to repay the usurers by selling animals. Instead, they tend to increase their bank loans in the coming year to repay the previous year’s debt, trapping them in a vicious and ultimately impoverishing circle of annual loans they cannot fully pay back, and feeding increasing debt. We suggest that microcredit programs in semiarid areas should be in sync with the local production cycle and recognize environmental constraints that cause high variation in production seasonally and year to year. Our results supplement previous findings on microcredit applications and are particularly pertinent for other semiarid areas of the world.
Characterizing the kerogen-hosted pore structures is essential to understand the adsorption, transport and storage potential in organic-rich shale reservoirs. In this paper, we first separated the organic matter (kerogen) from the mineral matrix in four different shale samples of the Bakken Formation with different thermal maturities and then analyzed their chemical compositions using the wide-angle X-ray scattering (WAXS) method. Next, we acquired small-angle X-ray scattering (SAXS) to characterize the structure of the organic matter and see how these two will relate. The WAXS results showed that the isolated kerogens have high purity (free of inorganic minerals) and retain different chemical compositions. Moreover, SAXS analysis revealed that the isolated kerogens have similar radius of gyration (Rg) which is around 90 Å and the molecules are in the compact mode. Based on the pore size distribution analysis from the SAXS data, two main peaks were found in all of these four samples with one peak less than 40 Å and the other one larger than 1000 Å. Also, the TEM images revealed that Sample 1 is abundant in pores with sizes around 20 nm while Sample 2 does not have pores of that size, which agrees with the results from the pore size distribution that was obtained from the SAXS method. Ultimately, this study exhibits how different analytical instruments can provide us with useful information from complex structures of geomaterials. For all the samples, two main peaks can be found with one peak less than 40 Å and the other one larger than 1000 Å。
Quantifying the rhythms and rates of magmatic-hydrothermal systems is critical for a better understanding of their controls on ore formation and the dynamics of magmatic reservoirs that feed them. We reconstructed the evolution of ore-forming fluids using hydrothermal quartz from the 17.4 Ma Zhibula skarn, Tibet. Ion probe analysis reveals sharp and dramatic changes in quartz delta O-18 values between 5 parts per thousand and -9.3 parts per thousand, with fluid delta O-18 values varying between 2.8 parts per thousand and -18.2 parts per thousand, which are best explained by transient meteoric water incursion into a hydrothermal system dominated by magmatic fluids. Two pulses of magmatic fluids and a meteoric water incursion event are inferred, which operated at the millennium scale (760-1510 yr) as constrained by the aluminum diffusion chronometer. Our results indicate that magmatic reservoirs are likely water unsaturated for most of their lifetime (>10(5)-10(6) yr), with transient and episodic fluid exsolutions (similar to 10(3) yr) being driven by magma replenishment or crystallization-induced water saturation. With focused and efficient metal deposition, multiple pulses of metalliferous fluids favor the formation of giant deposits with high grade. Meteoric water delta O-18 values (-25.4 +/- 2.3 parts per thousand) derived from Zhibula quartz further suggest a paleo-elevation of 5.9 +/- 0.3 km; this transient early Miocene surface uplift plausibly was due to break-off of the oceanic slab attached to the Indian Plate. Our research highlights that ubiquitous hydrothermal quartz in orogenic belts can probe the dynamics of magmatic-hydrothermal systems and also quantify paleo-elevations, which has significant tectonic implications.
The novel working principle enables spiking cameras to capture high-speed moving objects. However, the applications of spiking cameras can be affected by many factors, such as brightness intensity, detectable distance, and the maximum speed of moving targets. Improper settings such as weak ambient brightness and too short object-camera distance, will lead to failure in the application of such cameras. To address the issue, this paper proposes a modeling algorithm that studies the detection capability of spiking cameras. The algorithm deduces the maximum detectable speed of spiking cameras corresponding to different scenario settings (e.g., brightness intensity, camera lens, and object-camera distance) based on the basic technical parameters of cameras (e.g., pixel size, spatial and temporal resolution). Thereby, the proper camera settings for various applications can be determined. Extensive experiments verify the effectiveness of the modeling algorithm. To our best knowledge, it is the first work to investigate the detection capability of spiking cameras.