Mountain and polar glaciers cover 10%of the Earth’s surface and are typically extreme environments that challenge life of all forms.Viruses are abundant and active in supraglacial ecosystems and play a crucial role i...Mountain and polar glaciers cover 10%of the Earth’s surface and are typically extreme environments that challenge life of all forms.Viruses are abundant and active in supraglacial ecosystems and play a crucial role in controlling the supraglacial microbial communities.However,our understanding of virus ecology on glacier surfaces and their potential impacts on downstream ecosystems remains limited.Here,we present the supraglacial virus genome(SgVG)catalog,a 15-fold expanded genomic inventory of 10,840 DNAvirus species from 38 mountain and polar glaciers,spanning habitats such as snow,ice,meltwater,and cryoconite.Supraglacial DNA-viruses were highly specific compared to viruses in other ecosystems yet exhibited low public health risks.Supraglacial viral communities were primarily constrained by habitat,with cryoconite displaying the highest viral activity levels.We observed a prevalence of lytic viruses in all habitats,especially in cryoconite,but a high level of lysogenic viruses in snow and ice.Additionally,we found that supraglacial viruses could be linked to~83%of obtained prokaryotic phyla/classes and possessed the genetic potential to promote metabolism and increase cold adaptation,cell mobility,and phenolic carbon use of hosts in hostile environmental conditions using diverse auxiliary metabolic genes.Our results provide the first systematic characterization of the diversity,function,and public health risks evaluation of mountain and polar supraglacial DNA viruses.This understanding of glacial viruses is crucial for function assessments and ecological modeling of glacier ecosystems,especially for the Tibetan Plateau’s Mountain glaciers,which support~20%of the human populations on Earth.展开更多
Glaciological mass balance(MB)is considered the most direct,undelayed and unfiltered response of the glaciers to climatic perturbations.However,it may inherit errors associated with stake underrepresentation,averaging...Glaciological mass balance(MB)is considered the most direct,undelayed and unfiltered response of the glaciers to climatic perturbations.However,it may inherit errors associated with stake underrepresentation,averaging over the entire glacier and human bias.Therefore,proper validation of glaciological MB with geodetic MB is highly recommended by the World Glacier Monitoring Service(WGMS).The present study focuses on the Dokriani Glacier,central Himalaya which is one of the bench-mark glaciers in the region and has glaciological MB records from 1993 to 2013 with intermittent gaps.In the present study,firstly the glaciological MB series is extended to 2014 i.e.,field-based MB for one more year is computed and,to compare with it,the geodetic MB is computed for the 1999–2014 period using high resolution Cartosat-1 digital elevation model(DEM)and SRTM DEM.Finally,the study assesses the regional representation of the Dokriani Glacier in terms of MB and evaluates the influence of the MB regime on its morphological evolution.Results show that the average glaciological MB(-0.34±0.2 m water equivalent(w.e.)y-1)is more negative than the geodetic MB(-0.23±0.1 m w.e.y-1)for the 1999–2014 period.This is likely because of the partial representation of glacier margins in the glaciological MB,where melting is strikingly low owing to thick debris cover(>30 cm).In contrast,geodetic MB considers all marginal pixels leading to a comparatively low MB.A comparative assessment shows that the MB of Dokriani Glacier is less negative(possibly due to its huge accumulation area)than most other glacier-specific and regional MBs,restricting it to be a representative glacier in the region.Moreover,continuous negative MB has brought a peculiar change in the epiglacial morphology in the lower tongue of the glacier as differential debris thickness-induced differential melting has turned the glacier surface into a concave one.This concavity has led to development of a large(10–20 m deep)supraglacial channel which is expanding incessantly.The supraglacial channel is also connected with the snout wall and accelerates terminus disintegration.Given the total thickness of about 30–50 m in the lower glacier tongue,downwasting at its current pace,deepening/widening of supraglacial channel coupled with rapid terminus retreat may lead to the complete vanishing of the lower one km glacier tongue.展开更多
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
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(2021QZKK0100)the National Key Research and Development Plans(2021YFC0863400)+2 种基金the National Key Research and Development Plans(2021YFC2300904)the National Natural Science Foundation of China General Program(42171144)the National Natural Science Foundation of China for Excellent Young Scientists Fund Program(42222105)。
文摘Mountain and polar glaciers cover 10%of the Earth’s surface and are typically extreme environments that challenge life of all forms.Viruses are abundant and active in supraglacial ecosystems and play a crucial role in controlling the supraglacial microbial communities.However,our understanding of virus ecology on glacier surfaces and their potential impacts on downstream ecosystems remains limited.Here,we present the supraglacial virus genome(SgVG)catalog,a 15-fold expanded genomic inventory of 10,840 DNAvirus species from 38 mountain and polar glaciers,spanning habitats such as snow,ice,meltwater,and cryoconite.Supraglacial DNA-viruses were highly specific compared to viruses in other ecosystems yet exhibited low public health risks.Supraglacial viral communities were primarily constrained by habitat,with cryoconite displaying the highest viral activity levels.We observed a prevalence of lytic viruses in all habitats,especially in cryoconite,but a high level of lysogenic viruses in snow and ice.Additionally,we found that supraglacial viruses could be linked to~83%of obtained prokaryotic phyla/classes and possessed the genetic potential to promote metabolism and increase cold adaptation,cell mobility,and phenolic carbon use of hosts in hostile environmental conditions using diverse auxiliary metabolic genes.Our results provide the first systematic characterization of the diversity,function,and public health risks evaluation of mountain and polar supraglacial DNA viruses.This understanding of glacial viruses is crucial for function assessments and ecological modeling of glacier ecosystems,especially for the Tibetan Plateau’s Mountain glaciers,which support~20%of the human populations on Earth.
基金National Post-Doctoral Fellowship(NPDF)award(PDF/2020/000103)from Department of Science and Technology(DST,India)。
文摘Glaciological mass balance(MB)is considered the most direct,undelayed and unfiltered response of the glaciers to climatic perturbations.However,it may inherit errors associated with stake underrepresentation,averaging over the entire glacier and human bias.Therefore,proper validation of glaciological MB with geodetic MB is highly recommended by the World Glacier Monitoring Service(WGMS).The present study focuses on the Dokriani Glacier,central Himalaya which is one of the bench-mark glaciers in the region and has glaciological MB records from 1993 to 2013 with intermittent gaps.In the present study,firstly the glaciological MB series is extended to 2014 i.e.,field-based MB for one more year is computed and,to compare with it,the geodetic MB is computed for the 1999–2014 period using high resolution Cartosat-1 digital elevation model(DEM)and SRTM DEM.Finally,the study assesses the regional representation of the Dokriani Glacier in terms of MB and evaluates the influence of the MB regime on its morphological evolution.Results show that the average glaciological MB(-0.34±0.2 m water equivalent(w.e.)y-1)is more negative than the geodetic MB(-0.23±0.1 m w.e.y-1)for the 1999–2014 period.This is likely because of the partial representation of glacier margins in the glaciological MB,where melting is strikingly low owing to thick debris cover(>30 cm).In contrast,geodetic MB considers all marginal pixels leading to a comparatively low MB.A comparative assessment shows that the MB of Dokriani Glacier is less negative(possibly due to its huge accumulation area)than most other glacier-specific and regional MBs,restricting it to be a representative glacier in the region.Moreover,continuous negative MB has brought a peculiar change in the epiglacial morphology in the lower tongue of the glacier as differential debris thickness-induced differential melting has turned the glacier surface into a concave one.This concavity has led to development of a large(10–20 m deep)supraglacial channel which is expanding incessantly.The supraglacial channel is also connected with the snout wall and accelerates terminus disintegration.Given the total thickness of about 30–50 m in the lower glacier tongue,downwasting at its current pace,deepening/widening of supraglacial channel coupled with rapid terminus retreat may lead to the complete vanishing of the lower one km glacier tongue.
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.
