Speleothem CaCO3 δ18O is a commonly employed paleomonsoon proxy. However, inferring local rainfall amount from speleothem δ18O can be complicated due to changing source water δ18O, temperature effects, and rainout over the moisture transport path. These complications are addressed using δ18O of planktonic foraminiferal CaCO3, offshore from the Yangtze River Valley (YRV). The advantage is that the effects of global seawater δ18O and local temperature changes can be quantitatively removed, yielding a record of local seawater δ18O, a proxy that responds primarily to dilution by local precipitation and runoff. Whereas YRV speleothem δ18O is dominated by precession-band (23 ky) cyclicity, local seawater δ18O is dominated by eccentricity (100 ky) and obliquity (41 ky) cycles, with almost no precession-scale variance. These results, consistent with records outside the YRV, suggest that East Asian monsoon rainfall is more sensitive to greenhouse gas and high-latitude ice sheet forcing than to direct insolation forcing.

Precession-band variance missing from East Asian monsoon runoff

Seasonal imprint of Holocene temperature reconstruction on the Tibetan Plateau

Migration of the Northern Boundary of the East Asian Summer Monsoon Over the Last 21,000 years

Spatial distribution of n-alkanes in the catchment and sediments of Lake Lugu, Southwest China: Implications for palaeoenvironment reconstruction

Predicting and preventing disasters in difficult‐to‐access environments, such as oceans, requires self‐powered monitoring devices. Since the need to periodically charge and replace batteries is an economic and environmental concern, energy harvesting from external stimuli to supply electricity to batteries is increasingly being considered. Especially, in aqueous environments including electrolytes, coiled carbon nanotube (CNT) yarn harvesters have been reported as an emerging approach for converting mechanical energy into electrical energy driven by large and reversible capacitance changes under stretching and releasing. To realize enhanced harvesting performance, experimental and computational approaches to optimize structural homogeneity and electrochemical accessible area in CNT yarns to maximize intrinsic electrochemical capacitance (IEC) and stretch‐induced changes are presented here. Enhanced IEC further enables to decrease matching impedance for more energy efficient circuits with harvesters. In an ocean‐like environment with a frequency from 0.1 to 1 Hz, the proposed harvester demonstrates the highest volumetric power (1.6–10.45 mW cm−3) of all mechanical harvesters reported in the literature to the knowledge of the authors. Additionally, a high electrical peak power of 540 W kg−1 and energy conversion efficiency of 2.15% are obtained from torsional and tensile mechanical energy.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/advs.202203767

Chemo‐Mechanical Energy Harvesters with Enhanced Intrinsic Electrochemical Capacitance in Carbon Nanotube Yarns

One long-standing issue in the paleoclimate records is whether East Asian Summer Monsoon peaked in the early Holocene or mid-Holocene. Here, combining a set of transient earth system model simulations with proxy records, we propose that, over northern China, monsoon rainfall peaked in the early Holocene, while soil moisture and tree cover peaked in the mid-Holocene. The delayed ecosystem (soil moisture and tree cover) response to rainfall is caused by the vegetation response to winter warming and the subsequent feedback with soil moisture. Our study provides a mechanism for reconciling different evolution behaviors of monsoon proxy records; it sheds light on the driving mechanism of the monsoon evolution and monsoon-ecosystem feedback over northern China, with implications to climate changes in other high climate sensitivity regions over the globe. How the East Asian Summer Monsoon has changed over the Holocene has been debated, as some proxy records disagree with each other. Here, the authors suggest that monsoonal rainfall peaked in the early Holocene, while ecosystem responses peaked in the mid-Holocene, explaining the differences between records.

/pdf/vegetation-feedback-causes-delayed-ecosystem-response-to-183tk4vj80.pdf

Vegetation feedback causes delayed ecosystem response to East Asian Summer Monsoon Rainfall during the Holocene.

Paleoclimate Significance of Reconstructed Rainfall Isotope Changes in Asian Monsoon Region

Deserts and their margins have long presented a challenge for human habitation, as an unstable and easily degraded environment. Deserts are the most important source of global dust emission, and the dust flux can be used as an index of land degradation and climate change, as well as a way to assess the dust’s own effects on global climate. In this study, we used the Moderate Resolution Imaging Spectroradiometer (MODIS) data, combing with Support Vector Machine (SVM) analysis, trial-and-error method and visual interpretation analyses, to extract the global and regional desert area, and analyze the accuracy of classification of the extracted desert area. We use data on topography, precipitation, evapotranspiration, and surface wind speed to characterize the environment of the world’s deserts, in order to explore the natural conditions that produce and accompany desert and produce a clear objective definition for desert environment. Our results show that global desert area is <sc>~17.5×106 km2,</sc> and the overall classificatory accuracy is 92%, according to the cross-checked by the multi sources data calibrations. Globally, desert is mainly distributed in eastern hemisphere and northern hemisphere; North Africa and East Asia have the largest desert area. The classificatory accuracy of all individual regions is greater than 75%. Global desert, as characterized by our multi-faceted definition, is mainly distributed in low regions below<sc>2000 m</sc> elevation, mean annual precipitation less than <sc>200 mm,</sc> and annual wind speed is about <sc>4–6 m/s.</sc> Based on our defined distribution of global deserts, we estimated dust emissions from those areas. Because dust emission is a small-scale, random process, it is necessary to collect field data of dust emission from typical landscape types, in order to describe dust emission and quantitatively assess their impact. We used data from the Portable <italic>In-Situ</italic> Wind Erosion Laboratory (PI-SWERL), which is a newly developed portable wind erosion instrument. Its observation data are in good agreement with the wind tunnel experiment results. Because of its small size and portability, it has great advantages in measuring dust emission at specific sites. We integrated measured data about 1400 PI-SWERL observation points of dust emission (PM10), combing with land cover type, soil moisture and friction wind speed data, and obtained about 14000 points quantifying dust emission through interpolation. These 14000 dust emission amounts points are distributed across different areas of the desert. Using these 14000 points to make Tyson polygons, we estimated the annual dust emission amount of each polygon area, and then added each annual dust emission amounts polygon area to obtain the annual dust emission amount of global desert. Dust emission amount shows considerable geographical differences between different desert areas. The region around the Caspian Sea and Aral Sea in central Asia, Mesopotamia in western Asia, sandy areas in northern West Asia and eastern Australia have the highest annual dust emission rates. This result is in good agreement with previous published results on global dust source regions. The annual dust emission amounts in desert area are ~1792.65 Tg/a, and North Africa has the largest annual dust emission amounts, ~786.03 Tg/a, accounting for 43.85% of the total dust emission amounts of global desert. According to the relationship between dust deposition in land and sea, we estimate that ~1344.49 Tg/a dust is deposited in land and ~448.16 Tg/a in ocean. The global desert area interpreted from remote sensing images using our new standardized protocol, and our dust emission estimates, will facilitate further understanding of the environmental changes within deserts and their impacts.

A new estimate of global desert area and quantity ofdust emission

Deserts are important landscapes on the earth and their variations have impacts on global climate through feedback processes. However, there is a limited understanding of the climatic controls on the spatial and temporal variations of global deserts. Here, we use climate reanalysis datasets, global land use/land cover (LULC) products and the CMIP6 (Coupled Model Intercomparison Project) model outputs to calculate the changing of global deserts during 1982–2020, and estimate future spatial trends of global deserts. Our results show that mean annual global desert area over this period is 17.64×106 km2, accounting for 12% of the terrestrial land. Desert areas decreased rapidly from the end of the 1980s to the 1990s in North Africa and Australia, followed by a slow expansion in the early 21st century globally. Spatio-temporal variations of areas of arid climate are characterized by interdecadal fluctuations, and there are clear regional differences in dynamics of the aridity index (AI, used here as a proxy for the area of drylands) and desert areas. Statistical analyses reveal that increased vegetation cover is directly related to the reduction of desert area, while potential evaporation, surface temperature and humidity are also significantly correlated with the desert area. The relationship between wind speed and desert dynamics varies regionally. The results of the CMIP6 simulations suggest that global deserts will expand in the 21st century, albeit at different rates under the ssp245 and ssp585 scenarios. Desert expansions are modelled to be greatest in Asia, Africa and Australia, while those of southern North Africa may reduce as their southern borders migrate northwards. 

https://link.springer.com/content/pdf/10.1007/s11430-022-1052-1.pdf

Global desert variation under climatic impact during 1982–2020

沙漠是重要的地表景观，其变化深刻影响着人类的生产生活，但是，目前对全球沙漠的长期变化规律及其气候影响了解有限。本文使用气候再分析数据和遥感产品分别计算了全球沙漠的分布与面积变化，分析了不同气候因子对沙漠变化的影响，并利用CMIP6模式结果估算了未来全球沙漠变化趋势。结果表明，全球沙漠面积约17.64×106 km2，占陆地面积的12%，在1980s末到1990s快速减小，其中沙漠缩小主要发生在北非和澳大利亚，21世纪初沙漠开始缓慢扩张。气候干旱区面积主要表现为年代际波动，各地区干旱指数(AI)与沙漠面积的变化有明显差异。相关性分析表明，降水增加对沙漠缩小有直接影响，潜在蒸发、温度和湿度和沙漠面积呈负相关关系，而风速与沙漠面积变化的关系有区域性差异。CMIP6模式结果表明，在ssp245和ssp585情景下，21世纪全球沙漠都将有不同程度的扩张，其中亚洲、非洲和澳大利亚沙漠扩张最多，而北非南部沙漠将会缩小，北非沙漠北移。

Jingjing Wang

Papers

Vegetation feedback causes delayed ecosystem response to East Asian Summer Monsoon Rainfall during the Holocene.

Paleoclimate Significance of Reconstructed Rainfall Isotope Changes in Asian Monsoon Region

A new estimate of global desert area and quantity ofdust emission

Global desert variation under climatic impact during 1982–2020

全球沙漠变化的气候影响