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Export of nutrients and suspended solids from major Arctic rivers and their response to permafrost degradation

Advances in Climate Change Research 2021年第4期12卷 466-474页

作者： ZHANG Shu-Min MU Cui-Cui LI Zhi-Long DONG Wen-Wen WANG Xing-Yu Irina STRELETSKAYA Valery GREBENETS sergey sokratov Alexander KIZYAKOV WU Xiao-Dong Key Laboratory of Western China's Environmental Systems(Ministry of Education) College of Earth and Environmental SciencesLanzhou UniversityLanzhou730000China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai519000China Cryosphere Research Station on the Qinghai-Tibetan Plateau State Key Laboratory of Cryospheric ScienceNorthwest Institute of Eco-Environment and ResourceChinese Academy of SciencesLanzhou730000China University Cooperation of Polar Research Beijing100875China Geographical Faculty Lomonosov Moscow State UniversityMoscow119991Russia

The rapid warming of the Arctic has led to permafrost degradation,accelerating the transport of terrestrial materials by rivers.The quan-titative assessment of riverine nutrients and total suspended solids(TSS)flux is important to clarify the land-ocean connections in the Arctic.However,much is unknown about the estimates of these components from direct measurements in the Arctic rivers and the response of the components to permafrost degradation.Here,we report the results from the Arctic Great Rivers Observatory(Arctic-GRO)for the six major Arctic rivers(Yenisey,Lena,Ob',Mackenzie,Yukon,and Kolyma)to investigate the riverine exports of TSS,total dissolved nitrogen(TDN),nitrate(NO3-),bicarbonate(HCO3-),total dissolved phosphorus(TDP),and phosphate(PO43-).The results showed that from 2004 to 2017,the annual TSS,TDN,and NO3-exports to the Arctic Ocean were approximately 106,026 Gg,692 Gg,and 130 Gg,respectively,and the HCO3-,TDP,and PO43-exports were approximately 79,092 Gg,32 Gg,and 18 Gg,respectively.There were remarkable variations in component concentrations and fluxes between seasons.More than 80%of the TDN,TDP,PO43,and TSS exports mainly occurred in spring and summer,and a high HCO3-flux was recorded in summer,while a high NO3-flux in some rivers occurred in winter.The active layer thickness was significantly positively correlated with the annual TDN,NO3-,and HCO3-exports.In addition,the HCO3-flux of the six Arctic rivers increased by 247 Gg per year during 2004-2017.The positive relationship between the active layer thickness and river discharge indicates that permafrost degradation accelerated rivefine carbonate,nitrogen,and phosphorus exports.This study demonstrates that riverine exports play an important role both in the Arctic terrestrial and marine ecosystems,and permafrost degradation will likely increase the riverine material exports to the ocean.

关键词： Arctic rivers Carbonate Nutrients Total suspended solids Permafrost

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Changes in net ecosystem exchange of CO_(2)in Arctic and their relationships with climate change during 2002-2017

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Advances in Climate Change Research 2021年第4期12卷 475-481页

作者： LI Zhi-Long MU Cui-Cui CHEN Xu WANG Xing-Yu DONG Wen-Wen JIA Lin MU Mei Irina STRELETSKAYA Valery GREBENETS sergey sokratov Alexander KIZYAKOV WU Xiao-Dong Key Laboratory of Western China's Environmental Systems(Ministry of Education) College of Earth and Environmental SciencesLanzhou UniversityLanzhou730000China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai519000China Cryosphere Research Station on the Qinghai-Tibetan Plateau State Key Laboratory of Cryospheric ScienceNorthwest Institute of Eco-Environment and ResourceChinese Academy of SciencesLanzhou730000China University Cooperation of Polar Research Beijing100875China Geographical Faculty Lomonosov Moscow State UniversityMoscow119991Russia

Arctic wanning leads to permafrost degradation,which can increase ecosystem respiration and release more greenhouse gas into the at-mosphere.Meanwhile,climate warming also promotes the plant growth and increases carbon assimilation.Presently,it is largely unknown about the carbon budget and their responses to climate change in the Arctic regions.In this study,to investigate the seasonal and annual net ecosystem carbon exchange(NEE),we collected 71 observation stations for net ecosystem exchange(NEE)of CO_(2)in the high latitude permafrost regions during 2002-2017.The results showed that the annual NEE was-8.2±4.1 g CO_(2)m^(-2)d^(-1)for forest,-3.3±2.6 g CO_(2)m^(-2)d^(-1)for shrub,-4.8±4.1 g CO_(2)m^(-2)d^(-1)for grassland,-3.6±3.0 g CO_(2)m^(-2)d^(-1)for wetland and 0.02±0.62 g CO_(2)m^(-2)d^(-1)for tundra,respectively.From 2002 to 2017,the CO_(2)emissions of grassland(carbon source)showed a decreasing trend,and the CO_(2)assimilation of shrub and forest(carbon sink)has been increased.The wetland and tundra are shifting from carbon sources to sinks.There were great variations in temperature sen-sitivities(Q10)of NEE in different seasons,with larger values in winter and lower values in summer.These findings indicate that the Arctic terrestrial ecosystem presently acts as a carbon sink,while there is a possibility that future warming,especially the warming in winter,may decrease the carbon sink of the Arctic terrestrial ecosystem.

关键词： Arctic Climate change Permafrost Carbon flux Ecosystem Eddy covariance

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Changes in different land cover areas and NDVI values in northern latitudes from 1982 to 2015

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Advances in Climate Change Research 2021年第4期12卷 456-465页

作者： XUE Shou-Ye XU Hai-Yan MU Cui-Cui WU Tong-Hua LI Wang-Ping ZHANG Wen-Xin Irina STRELETSKAYA Valery GREBENETS sergey sokratov Alexander KIZYAKOV WU Xiao-Dong Cryosphere Research Station on the Qinghai-Tibet Plateau State Key Laboratory of Cryospheric ScienceNorthwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou730000China School of Environmental and Municipal Engineering Lanzhou Jiaotong UniversityLanzhou730070China Key Laboratory of Western China's Environmental Systems(Ministry of Education) College of Earth and Environmental SciencesLanzhou UniversityLanzhou730000China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai519000China University Cooperation of Polar Research Beijing100875China Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou511458China University of Chinese Academy of Sciences Beijing10049China School of Civil Engineering Lanzhou University of TechnologyLanzhou730050China Department of Physical Geography and Ecosystem Science Lund UniversityLundSE-22362Sweden Center for Permafrost(CENPERM) Department of Geosciences and Natural Resource ManagementUniversity of CopenhagenCopenhagenDK-1165Denmark Geographical Faculty Lomonosov Moscow State UniversityMoscow119991Russia.

Climate warming leads to vast changes in the land cover types and plant biomass in the northern high-latitude regions.The overall trend is of shrubland and tree lines moving northwards,while changes in different land cover types and vegetation growth in response to climate change are largely unknown.Here,we selected land areas with latitudes higher than 50°N as the study area.We compared the land cover type changes and explored relationships between the normalized difference vegetation index(NDVI)values of different land cover types,air temperature,and precipitation during 1982-2015 based on dynamic grid.The results indicated that forest and shrubland areas increased as a large area of grassland shifted to forest and shrubland.The snow/ice,tundra and grassland largely have decreased from 1982 to 2015.Although approximately 277.3×103 km2 of barren land(6.2%of the total barren land area in 1982)changed to tundra,the tundra area still decreased because some tundra shifted to forest and grassland.The NDVI values of tundra significantly increased,but the shrubland showed a decreasing trend.Temperature in the growing season(June to September)showed the largest positive correlation coefficients with the NDVI values of forest,tundra,grassland,and cropland.However,due to shrubification processes and plant mortality in shrubland areas,the shrubland NDVI showed negative relationship with annual temperature but positively correlated with monthly t.Taken together,although there is large room for improvement of the land cover type data accuracy,our results suggested that the land cover types in high-latitude regions changed significantly,while the NDVI values of the different land cover types showed different responses to climate change.

关键词： Air temperature Arctic Climate change Precipitation NDVI

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