Surface melt has great impacts on the Greenland Ice Sheet （GrlS） mass balance and thereby has become the focus of significant GrlS research in recent years. The production, transport, and release processes of surfac...Surface melt has great impacts on the Greenland Ice Sheet （GrlS） mass balance and thereby has become the focus of significant GrlS research in recent years. The production, transport, and release processes of surface meltwater are the keys to understanding the poten- tial impacts of the GrlS surface melt. These hydrological processes can elucidate the following scientific questions： How much melt- water is produced atop the GrlS？ What are the characteristics of the meltwater-formed supraglacial hydrological system？ How does the meltwater influence the GrlS motion？ The GrlS supraglacial hydrology has a number of key roles and yet continues to be poorly understood or documented. This paper summarizes the current understanding of the GrlS surface melt, emphasizing the three essential supraglacial hydrological processes： （1） meltwater production： surface melt modeling is an important approach to acquire surface melt information, and areas, depths, and volumes of supraglacial lakes extracted from remotely sensed imagery can also provide surface melt information; （2） meltwater transport： the spatial distributions of supraglacial lakes, supraglacial sarams, moulins, and crevasses demonstrate the characteristics of the supraglacial hydrological system, revealing the meltwater transport process; and （3） meltwater release： the release of meltwater into the englacial and the subglacial ice sheet has important but undetermined impacts on the GrlS motion. The correlation between surface runoff and the GrlS motion speed is employed to understand these influences.展开更多
Icebergs are big chunks of ice floating on the ocean surface,and melting of icebergs contributes for the major part of freshwater flux into ocean.Dynamic monitoring of the icebergs in Antarctica and accurate estimatio...Icebergs are big chunks of ice floating on the ocean surface,and melting of icebergs contributes for the major part of freshwater flux into ocean.Dynamic monitoring of the icebergs in Antarctica and accurate estimation of their volume are important for predicting the trend of freshwater budget of the Southern Ocean.The iceberg freeboard is a key parameter for measuring the thickness and volume of an iceberg and is defined as the difference between the elevation of iceberg surface and sea level.So far,freeboards of icebergs have been successfully extracted using InSAR DEM,and the laser and radar altimeter.However,uncertainties exist in these results mainly caused by missed detection of small icebergs due to the spatially sparse and temporally incomplete data coverage.In addition to the above techniques,optical images can also be used to extract the iceberg freeboard based on its geometric relationship with shadow length,which can effectively compensate for the above shortcomings.Although the feasibility has been preliminarily presented,the precision and extensive application of shadow-height method deserves further research,such as estimating the basal melting of icebergs.In this work,we tested an optical image-based freeboard extraction method over icebergs in Prydz Bay,Antarctica.A normalized shadow pixel index(NSPI)is designed to identify iceberg shadows with different shapes in HY-1C/D CZI and Sentinel-2 MSI optical images.The iceberg freeboard can be determined with an acceptable precision(2 m)in optical images compared with laser altimeter(i.e.ICESat-2)measurements.Moreover,basal melting of icebergs has been assessed according to the variation of freeboard using repeated optical observations.The results indicate that icebergs in the study area were with a mean freeboard of about 56 m in early December 2022,and experienced a decrease in freeboard of 1.9 m within two months,in correspondence with the Antarctic seasonal trend.The methodological framework,therefore,turns out to be a reliable complementary approach to studying the iceberg freeboard in polar regions.展开更多
Land systems and climate,which are the key elements of agricultural production and key drivers of crop yields,affect the quality of arable land.However,a quantitative model to reveal the mechanism of how potential gra...Land systems and climate,which are the key elements of agricultural production and key drivers of crop yields,affect the quality of arable land.However,a quantitative model to reveal the mechanism of how potential grain yields are affected by macro-scale arable land evolution and climate change has not yet been developed.In this study,we constructed a Grey Prediction Model-Future Land Use Simulation(GM-FLUS),which combined land system evolution with climate change data,to simulate changes in China’s land system over the next 40 years.We improved the Global Agro-Ecological Zone(GAEZ)model,estimated China’s potential rice yields and their spatial distribution in the next 40 years under four scenarios(shared socioeconomic pathway SSP1-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5)of the Sixth International Coupling Model Intercomparison Project,analysed the spatiotemporal variations in the potential rice yields and their drivers,and provided appropriate suggestions for increasing rice yields.The simulation results indicated an increase in China’s potential rice yields during 2020–2060 under the SSP1-2.6 and SSP3-7.0 scenarios and a decrease under the SSP2-4.5 and SSP5-8.5 scenarios.Moreover,China’s development strategy of“achieving carbon peaking by 2030 and carbon neutrality by 2060”was similar to the SSP1-2.6 scenario,under which rice yields were relatively stable.Furthermore,under China’s arable land protection policy,China’s paddy field area will change slightly during 2020–2060,and potential rice yields will be influenced by climate.Under the four climate change scenarios,air temperature increased and was negatively correlated with potential rice yields in main rice-producing regions.Additionally,potential rice yields were positively correlated with precipitation,which increased stably under the SSP1-2.6 and SSP3-7.0scenarios and decreased under the SSP2-4.5 and SSP5-8.5 scenarios.These results suggest that the development of heat-resistant rice varieties and the implementation of measures that will mitigate the impacts of future temperature increases on rice yields are important for the conservation of paddy fields.Additionally,improving irrigation and drainage facilities is necessary to irrigate drought-prone paddy fields and drain flooded water.展开更多
Forest biomass carbon storage(BC)plays a critical role in mitigating climate change.However,the spatiotemporal patterns and stability of BC growth in China remain unclear.Using the latest BC maps(2002–2021)and multi-...Forest biomass carbon storage(BC)plays a critical role in mitigating climate change.However,the spatiotemporal patterns and stability of BC growth in China remain unclear.Using the latest BC maps(2002–2021)and multi-source remote sensing data,we analyzed the spatiotemporal dynamics of BC and applied resilience indicators to reliably assess its stability.Our results show that while China’s long-term BC has continued to increase,the risk of BC losses has also intensified,particularly in old forests(>70 years),where approximately half exhibit a declining trend.Moreover,BC dynamics do not consistently align with resilience changes.About 53.4%of forests display weakening resilience,directly reducing BC accumulation rates by 23.1%and amplifying interannual variability.Alarmingly,10.4%of forests(BC-,resilience-),predominantly high-BC-density forests(mean:28.3 tC/ha),face an extremely high risk of carbon loss(carbon emissions:-118 Tg C).We further found that the accelerating effect of resilience weakening on BC losses significantly outweighs the promoting effect of resilience enhancement on BC accumulation(-17.79±4.72 Mg/ha vs.11.47±3.42 Mg/ha).Our study highlights that China’s BC growth is characterized by unstable components and faces substantial loss risks.In future efforts to enhance forest carbon sinks,greater attention should be paid to changes in forest resilience to improve the stability of biomass carbon sinks and achieve sustainable,long-term carbon sequestration.展开更多
The discovery of cause–effect relationships helps to understand the natural or physical mechanism[1].Causation inference is a key issue in many disciplines and has a long study history,especially in statistics,social...The discovery of cause–effect relationships helps to understand the natural or physical mechanism[1].Causation inference is a key issue in many disciplines and has a long study history,especially in statistics,social,and biomedical sciences[2].In Earth System Sciences,the cause–effect relationship also plays a fundamental role and has drawn increasing interests.However,for spatially large-scale research,it is not feasible to design and conduct con-trolled experiments to reveal the cause–effect relationships.There-fore,causation inference from time series data has been frequently employed,under the assumption that the cause precedes the effect[3].While the temporal inference works effectively to identify most causation between variables,limitations remain.If the time series is not long enough to catch significant changes of causes and effects,some important cause–effect relationships may be neglected.This limitation is highlighted in Earth System Sciences,as the evolution of global changes may take an extreme long period to present discernible variations.For instance.展开更多
Crop residue burning(CRB)is a major contributor to air pollution in China.Current fire detection methods,however,are limited by either temporal resolution or accuracy,hindering the analysis of CRB's diurnal charac...Crop residue burning(CRB)is a major contributor to air pollution in China.Current fire detection methods,however,are limited by either temporal resolution or accuracy,hindering the analysis of CRB's diurnal characteristics.Here we explore the diurnal spatiotemporal patterns and environmental impacts of CRB in China from 2019 to 2021 using the recently released NSMC-Himawari-8 hourly fire product.Our analysis identifies a decreasing directionality in CRB distribution in the Northeast and a notable southward shift of the CRB center,especially in winter,averaging an annual southward movement of 7.5.Additionally,we observe a pronounced skewed distribution in daily CRB,predominantly between 17:00 and 20:00.Notably,nighttime CRB in China for the years 2019,2020,and 2021 accounted for 51.9%,48.5%,and 38.0%respectively,underscoring its significant environmental impact.The study further quantifies the hourly emissions from CRB in China over this period,with total emissions of CO,PM10,and PM_(2.5) amounting to 12,236,2,530,and 2,258 Gg,respectively.Our findings also reveal variable lag effects of CRB on regional air quality and pollutants across different seasons,with the strongest impacts in spring and more immediate effects in late autumn.This research provides valuable insights for the regulation and control of diurnal CRB before and after large-scale agricultural activities in China,as well as the associated haze and other pollution weather conditions it causes.展开更多
基金supported by the Scholarship Award for Excellent Doctoral Student granted by Ministry of Education and the Graduate Education Innovation Project of Jiangsu Province(CXLX12-0039)
文摘Surface melt has great impacts on the Greenland Ice Sheet （GrlS） mass balance and thereby has become the focus of significant GrlS research in recent years. The production, transport, and release processes of surface meltwater are the keys to understanding the poten- tial impacts of the GrlS surface melt. These hydrological processes can elucidate the following scientific questions： How much melt- water is produced atop the GrlS？ What are the characteristics of the meltwater-formed supraglacial hydrological system？ How does the meltwater influence the GrlS motion？ The GrlS supraglacial hydrology has a number of key roles and yet continues to be poorly understood or documented. This paper summarizes the current understanding of the GrlS surface melt, emphasizing the three essential supraglacial hydrological processes： （1） meltwater production： surface melt modeling is an important approach to acquire surface melt information, and areas, depths, and volumes of supraglacial lakes extracted from remotely sensed imagery can also provide surface melt information; （2） meltwater transport： the spatial distributions of supraglacial lakes, supraglacial sarams, moulins, and crevasses demonstrate the characteristics of the supraglacial hydrological system, revealing the meltwater transport process; and （3） meltwater release： the release of meltwater into the englacial and the subglacial ice sheet has important but undetermined impacts on the GrlS motion. The correlation between surface runoff and the GrlS motion speed is employed to understand these influences.
基金supported by National Key Research and Development Program of China[Grant number 2021YFC2803301]China Europe Dragon 5 Cooperation Program[Grant number 59310]National Natural Science Foundation of China[Grant number 42071387].
文摘Icebergs are big chunks of ice floating on the ocean surface,and melting of icebergs contributes for the major part of freshwater flux into ocean.Dynamic monitoring of the icebergs in Antarctica and accurate estimation of their volume are important for predicting the trend of freshwater budget of the Southern Ocean.The iceberg freeboard is a key parameter for measuring the thickness and volume of an iceberg and is defined as the difference between the elevation of iceberg surface and sea level.So far,freeboards of icebergs have been successfully extracted using InSAR DEM,and the laser and radar altimeter.However,uncertainties exist in these results mainly caused by missed detection of small icebergs due to the spatially sparse and temporally incomplete data coverage.In addition to the above techniques,optical images can also be used to extract the iceberg freeboard based on its geometric relationship with shadow length,which can effectively compensate for the above shortcomings.Although the feasibility has been preliminarily presented,the precision and extensive application of shadow-height method deserves further research,such as estimating the basal melting of icebergs.In this work,we tested an optical image-based freeboard extraction method over icebergs in Prydz Bay,Antarctica.A normalized shadow pixel index(NSPI)is designed to identify iceberg shadows with different shapes in HY-1C/D CZI and Sentinel-2 MSI optical images.The iceberg freeboard can be determined with an acceptable precision(2 m)in optical images compared with laser altimeter(i.e.ICESat-2)measurements.Moreover,basal melting of icebergs has been assessed according to the variation of freeboard using repeated optical observations.The results indicate that icebergs in the study area were with a mean freeboard of about 56 m in early December 2022,and experienced a decrease in freeboard of 1.9 m within two months,in correspondence with the Antarctic seasonal trend.The methodological framework,therefore,turns out to be a reliable complementary approach to studying the iceberg freeboard in polar regions.
基金supported by the Key Project of the National Natural Science Foundation of China(Grant No.42230113)the National Key R&D Program of China(Grant No.2017YFB0504200)+2 种基金the“333 Project of High-level Talent Training”in Jiangsu Province(Grant No.BRA2020003)the National Natural Science Foundation of China(Grant No.42171395)the Jiangsu Provincial Excellent Youth Science Foundation(Grant No.BK20220126)。
文摘Land systems and climate,which are the key elements of agricultural production and key drivers of crop yields,affect the quality of arable land.However,a quantitative model to reveal the mechanism of how potential grain yields are affected by macro-scale arable land evolution and climate change has not yet been developed.In this study,we constructed a Grey Prediction Model-Future Land Use Simulation(GM-FLUS),which combined land system evolution with climate change data,to simulate changes in China’s land system over the next 40 years.We improved the Global Agro-Ecological Zone(GAEZ)model,estimated China’s potential rice yields and their spatial distribution in the next 40 years under four scenarios(shared socioeconomic pathway SSP1-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5)of the Sixth International Coupling Model Intercomparison Project,analysed the spatiotemporal variations in the potential rice yields and their drivers,and provided appropriate suggestions for increasing rice yields.The simulation results indicated an increase in China’s potential rice yields during 2020–2060 under the SSP1-2.6 and SSP3-7.0 scenarios and a decrease under the SSP2-4.5 and SSP5-8.5 scenarios.Moreover,China’s development strategy of“achieving carbon peaking by 2030 and carbon neutrality by 2060”was similar to the SSP1-2.6 scenario,under which rice yields were relatively stable.Furthermore,under China’s arable land protection policy,China’s paddy field area will change slightly during 2020–2060,and potential rice yields will be influenced by climate.Under the four climate change scenarios,air temperature increased and was negatively correlated with potential rice yields in main rice-producing regions.Additionally,potential rice yields were positively correlated with precipitation,which increased stably under the SSP1-2.6 and SSP3-7.0scenarios and decreased under the SSP2-4.5 and SSP5-8.5 scenarios.These results suggest that the development of heat-resistant rice varieties and the implementation of measures that will mitigate the impacts of future temperature increases on rice yields are important for the conservation of paddy fields.Additionally,improving irrigation and drainage facilities is necessary to irrigate drought-prone paddy fields and drain flooded water.
基金supported by the National Natural Science Foundation of China(Grant No.41901414)the Fundamental Research Funds for the Central Universities(Grant No.2243200008).
文摘Forest biomass carbon storage(BC)plays a critical role in mitigating climate change.However,the spatiotemporal patterns and stability of BC growth in China remain unclear.Using the latest BC maps(2002–2021)and multi-source remote sensing data,we analyzed the spatiotemporal dynamics of BC and applied resilience indicators to reliably assess its stability.Our results show that while China’s long-term BC has continued to increase,the risk of BC losses has also intensified,particularly in old forests(>70 years),where approximately half exhibit a declining trend.Moreover,BC dynamics do not consistently align with resilience changes.About 53.4%of forests display weakening resilience,directly reducing BC accumulation rates by 23.1%and amplifying interannual variability.Alarmingly,10.4%of forests(BC-,resilience-),predominantly high-BC-density forests(mean:28.3 tC/ha),face an extremely high risk of carbon loss(carbon emissions:-118 Tg C).We further found that the accelerating effect of resilience weakening on BC losses significantly outweighs the promoting effect of resilience enhancement on BC accumulation(-17.79±4.72 Mg/ha vs.11.47±3.42 Mg/ha).Our study highlights that China’s BC growth is characterized by unstable components and faces substantial loss risks.In future efforts to enhance forest carbon sinks,greater attention should be paid to changes in forest resilience to improve the stability of biomass carbon sinks and achieve sustainable,long-term carbon sequestration.
基金the National Key Research and Development Program of China(2021YFE0102300)the Natural Science Foundation of Beijing(8282031)the Fundamental Research Funds for the Central Universities。
文摘The discovery of cause–effect relationships helps to understand the natural or physical mechanism[1].Causation inference is a key issue in many disciplines and has a long study history,especially in statistics,social,and biomedical sciences[2].In Earth System Sciences,the cause–effect relationship also plays a fundamental role and has drawn increasing interests.However,for spatially large-scale research,it is not feasible to design and conduct con-trolled experiments to reveal the cause–effect relationships.There-fore,causation inference from time series data has been frequently employed,under the assumption that the cause precedes the effect[3].While the temporal inference works effectively to identify most causation between variables,limitations remain.If the time series is not long enough to catch significant changes of causes and effects,some important cause–effect relationships may be neglected.This limitation is highlighted in Earth System Sciences,as the evolution of global changes may take an extreme long period to present discernible variations.For instance.
基金supported by the Open Research Program of the International Research Center of Big Data for Sustainable Development Goals(Grant No.CBAS2022ORP02)the National Natural Science Foundation of China(Grant No.42171399).
文摘Crop residue burning(CRB)is a major contributor to air pollution in China.Current fire detection methods,however,are limited by either temporal resolution or accuracy,hindering the analysis of CRB's diurnal characteristics.Here we explore the diurnal spatiotemporal patterns and environmental impacts of CRB in China from 2019 to 2021 using the recently released NSMC-Himawari-8 hourly fire product.Our analysis identifies a decreasing directionality in CRB distribution in the Northeast and a notable southward shift of the CRB center,especially in winter,averaging an annual southward movement of 7.5.Additionally,we observe a pronounced skewed distribution in daily CRB,predominantly between 17:00 and 20:00.Notably,nighttime CRB in China for the years 2019,2020,and 2021 accounted for 51.9%,48.5%,and 38.0%respectively,underscoring its significant environmental impact.The study further quantifies the hourly emissions from CRB in China over this period,with total emissions of CO,PM10,and PM_(2.5) amounting to 12,236,2,530,and 2,258 Gg,respectively.Our findings also reveal variable lag effects of CRB on regional air quality and pollutants across different seasons,with the strongest impacts in spring and more immediate effects in late autumn.This research provides valuable insights for the regulation and control of diurnal CRB before and after large-scale agricultural activities in China,as well as the associated haze and other pollution weather conditions it causes.
