Organic carbon isotope （δ-13 Corg） data from two well-preserved sections across a shallow-to-deep water transect of the late Edi- acaran-Early Cambrian Yangtze Platform in South China show significant temporal and ...Organic carbon isotope （δ-13 Corg） data from two well-preserved sections across a shallow-to-deep water transect of the late Edi- acaran-Early Cambrian Yangtze Platform in South China show significant temporal and spatial variations. In the shallow-water Jiulongwan-Jijiapo section, δ-13Corg values of the late Ediacaran Dengying Formation range from -29‰ to -24%0. In the deep-water Longbizui section, δ-13Corg values from time-equivalent strata of the Dengying Formation are mostly between -35‰ and -32‰）. These new data, in combination with δ-13Corg data reported from other sections in South China, reveal a 6‰-8‰ shallow-to-deep water δ-13Corg gradient. High δ-13Corg values （〉-30‰） occur mostly in shallow-water carbonate rocks, whereas low δ-13Corg values （〈-32‰） dominate the deep-water black shale and chert. The large temporal and spatial δ-13Corg variations imply limited buffering effect from a large dissolved organic carbon （DOC） reservoir that was inferred to have existed in Edi- acaran-Early Cambrian oceans. Instead, δ-13C-org variations between platform and basin sections are more likely caused by dif- ferential microbial biomass contribution to total organic matter. High δ-13Corg values （〉-30‰） documented from shallow-water carbonates are within the range of typical Phanerozoic δ-13Corg data and may record the isotope signature of organic matter from primary （photosynthetic） production. In contrast, low δ-13Corg values （〈-32‰） from deep-water sections may have resulted from higher chemoautotrophic or methanotrophic biomass contribution to bulk organic matter in anoxic environments. The δ-13Corg data provide indirect evidence for ocean stratification and episodic chemocline fluctuations in the Ediacaran-Early Cambrian Yangtze Platform.展开更多
Ocean salinity is an important variable that affects the ocean stratification.We compared the salinity and ocean stratification in the tropical Pacific derived from the Argo(Array for Real-time Geostrophic Oceanograph...Ocean salinity is an important variable that affects the ocean stratification.We compared the salinity and ocean stratification in the tropical Pacific derived from the Argo(Array for Real-time Geostrophic Oceanography data),EN4(Ensemble 4 analysis),SODA(the Simple Ocean Data Assimilation reanalysis),IAP(Institute of Atmospheric Physics data),and ORAS4(Ocean Reanalysis System 4)over 2005–2017.Results show that the spatial distribution of climatological mean of sea surface salinity(SSS)in all the products is consistent,and the low salinity region showed large deviation and strong dispersion.The Argo has the smallest RMSE and the highest correlation with the ensemble mean,while the IAP shows a high-salinity deviations relative to other datasets.All the products show high positive correlations between the sea surface density(SSD)and SSS with respect to the deviations of climatological mean from ensemble mean,suggesting that the SSD deviation may be mainly influenced by the SSS deviation.In the aspect of the ocean stratification,the mixed layer depth(MLD)climatological mean in the Argo shows the highest correlation with the ensemble mean,followed by EN4,IAP,ORAS4,and SODA.The Argo and EN4 show thicker barrier layer(BL)relative to the ensemble mean while the SODA displays the largest negative deviation in the tropical western Pacific.Furthermore,the EN4,ORAS4,and IAP underestimate the stability in the upper ocean at the depths of 20–140 m,while Argo overestimates ocean stability.The salinity fronts in the western-central equatorial Pacific from Argo,EN4,and ORAS4 are consistent,while those from SODA and IAP show large deviations with a westward position in amplitude of 0°–6°and 0°–10°,respectively.The SSS trend patterns from all the products are consistent in having ensemble mean with high spatial correlations of 0.95–0.97.展开更多
Marine heatwaves(MHWs)are extreme ocean events characterized by anomalously warm upper-ocean temperatures,posing significant threats to marine ecosystems.While various factors driving MHWs have been extensively studie...Marine heatwaves(MHWs)are extreme ocean events characterized by anomalously warm upper-ocean temperatures,posing significant threats to marine ecosystems.While various factors driving MHWs have been extensively studied,the role of ocean salinity remains poorly understood.This study investigates the influence of salinity on the major 2013-2014 MHW event in the Northeast Pacific using reanalysis data and climate model outputs.Our results show that salinity variabilities are crucial for the development of the MHW event.Notably,a significant negative correlation exists between sea surface temperature anomalies(SSTAs)and sea surface salinity anomalies(SSSAs)during the MHW,with the SSSAs emerging simultaneously with SSTAs in the same area.Negative salinity anomalies(SAs)result in a shallower mixed layer,which suppresses vertical mixing and thus sustains the upper-ocean warming.Moreover,salinity has a greater impact on mixed layer depth anomalies than temperature.Model sensitivity experiments further demonstrate that negative SAs during MHWs amplify positive SSTAs by enhancing upper-ocean stratification,intensifying the MHW.Additionally,our analysis indicates that the SAs are predominantly driven by local freshwater flux anomalies,which are mainly induced by positive precipitation anomalies during the MHW event.展开更多
A halocline in the Arctic Ocean significantly slows the upward heat flux from deep warm water,thereby inhibiting the melting of surface sea ice.The western Arctic Ocean exhibits a double-halocline(DH)structure due to ...A halocline in the Arctic Ocean significantly slows the upward heat flux from deep warm water,thereby inhibiting the melting of surface sea ice.The western Arctic Ocean exhibits a double-halocline(DH)structure due to the complexity of the water mass.Using in situ measurements,we analyzed the vertical structural characteristics of DH and its interannual variation.The results indicated that the DH primarily occurs at the Northwind Ridge and the southern Canada Basin,extending westward to the Chukchi Abyssal Plain and northward to the northern boundary of the Canada Basin.From 2002 to 2022,there were changes in water masses that determined the structure of the DH.The significant increase in Pacific Water has resulted in 42%and 65%increases in freshwater and the heat content of the DH,respectively,along with a 14%reduction in stratification.Pacific Winter Water characterized by salinity of 33 has exhibited a gradually decreasing trend,suggesting that the lower halocline may be difficult to ventilate.The combined effects of Ekman pumping,mesoscale eddies,and positive buoyancy forcing(heat and freshwater input)from Pacific Water have altered the thickness and stratification of the DH.This study has enhanced our understanding of the evolution of vertical heat flux in the upper western Arctic Ocean.展开更多
As a crucial component of the Earth’s climate system,Antarctic sea ice has demonstrated significant variability over the satellite era.Here,we identify a remarkable decadal transition in the total Antarctic Sea Ice E...As a crucial component of the Earth’s climate system,Antarctic sea ice has demonstrated significant variability over the satellite era.Here,we identify a remarkable decadal transition in the total Antarctic Sea Ice Extent(SIE).The stage from 1979 to 2006 is characterized by high-frequency(i.e.,seasonal to interannual)temporal variability in SIE and zonal asymmetry in Sea Ice Concentration(SIC),which is primarily under the control of the Amundsen Sea Low(ASL).After 2007,however,sea ice changes exhibit a more spatially homogeneous pattern in SIC and a more temporally long-lasting mode in SIE.Further analysis reveals that sea ice-ocean interaction plays a major role in the low-frequency(i.e.,multiannual)variability of Antarctic sea ice from 2007−22.The related physical process is inferred to manifest as a strong coupling between the surface and the subsurface ocean layers,involving enhanced vertical convection and the downward delivery of the surface anomalies related to ice melting and freezing processes,thus maintaining the SIE anomalies for a longer time.Furthermore,this process mainly occurs in the Amundsen-Bellingshausen Sea(ABS)sector,and the weakened subsurface ocean stratification is the key factor triggering the coupling process in this region.We find that the Circumpolar Deep Water(CDW)over the ABS sector continued to shoal before 2007 and remained stable thereafter.It is speculated that the shoaling of the CDW may be a possible driver leading to the weakening of the subsurface stratification.展开更多
The state-of-the-art OpenFOAM technology is used to develop a numerical model that can be devoted to numerically investigating wake-collapse internal waves generated by a submerged moving body.The model incorporates b...The state-of-the-art OpenFOAM technology is used to develop a numerical model that can be devoted to numerically investigating wake-collapse internal waves generated by a submerged moving body.The model incorporates body geometry,propeller forcing,and stratification magnitude of seawater.The generation mechanism and wave properties are discussed based on model results.It was found that the generation of the wave and its properties depend greatly on the body speed.Only when that speed exceeds some critical value,between 1.5 and 4.5 m/s,can the moving body generate wake-collapse internal waves,and with increases of this speed,the time of generation advances and wave amplitude increases.The generated wake-collapse internal waves are confirmed to have characteristics of the second baroclinic mode.As the body speed increases,wave amplitude and length increase and its waveform tends to take on a regular sinusoidal shape.For three linearly temperature-stratified profiles examined,the weaker the stratification,the stronger the wake-collapse internal wave.展开更多
Carbonate carbon isotope （δ^13Ccarb） has received considerable attention in the Permian-Triassic transition for its rapid negative shift coinciding with the great end-Permian mass extinction event. The mechanism ha...Carbonate carbon isotope （δ^13Ccarb） has received considerable attention in the Permian-Triassic transition for its rapid negative shift coinciding with the great end-Permian mass extinction event. The mechanism has long been debated for such a c~ δ^13Ccarb negative excursion through the end-Permian crisis and subsequent large perturbations in the entire Early Triassic. A δ^13Ccarb depth gradient is observed at the Permian-Triassic boundary sections of different water-depths, i.e., the Yangou, Meishan, and Shangsi sections, and such a large δ^13Ccarb-depth gradient near the end-Permian mass extinction horizon is believed to result from a stratified Paleotethys Ocean with widespread anoxic/euxinic deep water. The evolution of δ^13Ccarb-depth gradient com- bined with paleontological and geochemical data suggests that abundant cyanobacteria and vigorous biological pump in the immediate aftermath of the end-Permian extinction would be the main cause of the large δ^13Ccarb-depth gradient, and the enhanced continental weathering with the mass extinction on land provides a mass amount of nutriment for the flourishing cyanobacteria. Photic zone anoxia/euxinia from the onset of chemocline upward excursion might be the direct cause for the mass extinction whereas the instability of chemocline in the stratified Early Triassic ocean would be the reason for the delayed and involuted biotic recovery.展开更多
基金supported by Ministry of Science and Technology of China(Grant No.2011CB808806)US National Science Foundation(Grant No.EAR-0745825)Doctoral Fund of Ministry of Education of China(Grant No.2012002212008)
文摘Organic carbon isotope （δ-13 Corg） data from two well-preserved sections across a shallow-to-deep water transect of the late Edi- acaran-Early Cambrian Yangtze Platform in South China show significant temporal and spatial variations. In the shallow-water Jiulongwan-Jijiapo section, δ-13Corg values of the late Ediacaran Dengying Formation range from -29‰ to -24%0. In the deep-water Longbizui section, δ-13Corg values from time-equivalent strata of the Dengying Formation are mostly between -35‰ and -32‰）. These new data, in combination with δ-13Corg data reported from other sections in South China, reveal a 6‰-8‰ shallow-to-deep water δ-13Corg gradient. High δ-13Corg values （〉-30‰） occur mostly in shallow-water carbonate rocks, whereas low δ-13Corg values （〈-32‰） dominate the deep-water black shale and chert. The large temporal and spatial δ-13Corg variations imply limited buffering effect from a large dissolved organic carbon （DOC） reservoir that was inferred to have existed in Edi- acaran-Early Cambrian oceans. Instead, δ-13C-org variations between platform and basin sections are more likely caused by dif- ferential microbial biomass contribution to total organic matter. High δ-13Corg values （〉-30‰） documented from shallow-water carbonates are within the range of typical Phanerozoic δ-13Corg data and may record the isotope signature of organic matter from primary （photosynthetic） production. In contrast, low δ-13Corg values （〈-32‰） from deep-water sections may have resulted from higher chemoautotrophic or methanotrophic biomass contribution to bulk organic matter in anoxic environments. The δ-13Corg data provide indirect evidence for ocean stratification and episodic chemocline fluctuations in the Ediacaran-Early Cambrian Yangtze Platform.
基金Supported by the National Key Research and Development Program on MonitoringEarly Warning and Prevention of Major Natural Disaster (No.2019YFC1510004)the Laoshan Laboratory (No.LSKJ202202403)。
文摘Ocean salinity is an important variable that affects the ocean stratification.We compared the salinity and ocean stratification in the tropical Pacific derived from the Argo(Array for Real-time Geostrophic Oceanography data),EN4(Ensemble 4 analysis),SODA(the Simple Ocean Data Assimilation reanalysis),IAP(Institute of Atmospheric Physics data),and ORAS4(Ocean Reanalysis System 4)over 2005–2017.Results show that the spatial distribution of climatological mean of sea surface salinity(SSS)in all the products is consistent,and the low salinity region showed large deviation and strong dispersion.The Argo has the smallest RMSE and the highest correlation with the ensemble mean,while the IAP shows a high-salinity deviations relative to other datasets.All the products show high positive correlations between the sea surface density(SSD)and SSS with respect to the deviations of climatological mean from ensemble mean,suggesting that the SSD deviation may be mainly influenced by the SSS deviation.In the aspect of the ocean stratification,the mixed layer depth(MLD)climatological mean in the Argo shows the highest correlation with the ensemble mean,followed by EN4,IAP,ORAS4,and SODA.The Argo and EN4 show thicker barrier layer(BL)relative to the ensemble mean while the SODA displays the largest negative deviation in the tropical western Pacific.Furthermore,the EN4,ORAS4,and IAP underestimate the stability in the upper ocean at the depths of 20–140 m,while Argo overestimates ocean stability.The salinity fronts in the western-central equatorial Pacific from Argo,EN4,and ORAS4 are consistent,while those from SODA and IAP show large deviations with a westward position in amplitude of 0°–6°and 0°–10°,respectively.The SSS trend patterns from all the products are consistent in having ensemble mean with high spatial correlations of 0.95–0.97.
基金The Laoshan Laboratory under contract Nos LSKJ202202403 and LSKJ202202402the National Natural Science Foundation of China under contract Nos 42030410 and 42406202+3 种基金the Natural Science Foundation of Jiangsu Province under contract No.BK20240718the Startup Foundation for Introducing Talent of Nanjing University of Information Science and Technologythe Jiangsu Innovation Research Group under contract No.JSSCTD202346the Jiangsu Funding Program for Excellent Postdoctoral Talent under contract No.2023ZB690.
文摘Marine heatwaves(MHWs)are extreme ocean events characterized by anomalously warm upper-ocean temperatures,posing significant threats to marine ecosystems.While various factors driving MHWs have been extensively studied,the role of ocean salinity remains poorly understood.This study investigates the influence of salinity on the major 2013-2014 MHW event in the Northeast Pacific using reanalysis data and climate model outputs.Our results show that salinity variabilities are crucial for the development of the MHW event.Notably,a significant negative correlation exists between sea surface temperature anomalies(SSTAs)and sea surface salinity anomalies(SSSAs)during the MHW,with the SSSAs emerging simultaneously with SSTAs in the same area.Negative salinity anomalies(SAs)result in a shallower mixed layer,which suppresses vertical mixing and thus sustains the upper-ocean warming.Moreover,salinity has a greater impact on mixed layer depth anomalies than temperature.Model sensitivity experiments further demonstrate that negative SAs during MHWs amplify positive SSTAs by enhancing upper-ocean stratification,intensifying the MHW.Additionally,our analysis indicates that the SAs are predominantly driven by local freshwater flux anomalies,which are mainly induced by positive precipitation anomalies during the MHW event.
基金The National Key Research and Development Program of China under contract No.2023YFC2809101the National Natural Science Foundation of China under contract No.42276239.
文摘A halocline in the Arctic Ocean significantly slows the upward heat flux from deep warm water,thereby inhibiting the melting of surface sea ice.The western Arctic Ocean exhibits a double-halocline(DH)structure due to the complexity of the water mass.Using in situ measurements,we analyzed the vertical structural characteristics of DH and its interannual variation.The results indicated that the DH primarily occurs at the Northwind Ridge and the southern Canada Basin,extending westward to the Chukchi Abyssal Plain and northward to the northern boundary of the Canada Basin.From 2002 to 2022,there were changes in water masses that determined the structure of the DH.The significant increase in Pacific Water has resulted in 42%and 65%increases in freshwater and the heat content of the DH,respectively,along with a 14%reduction in stratification.Pacific Winter Water characterized by salinity of 33 has exhibited a gradually decreasing trend,suggesting that the lower halocline may be difficult to ventilate.The combined effects of Ekman pumping,mesoscale eddies,and positive buoyancy forcing(heat and freshwater input)from Pacific Water have altered the thickness and stratification of the DH.This study has enhanced our understanding of the evolution of vertical heat flux in the upper western Arctic Ocean.
基金supported by the National Natural Science Foundation China(Grant No.42176222).
文摘As a crucial component of the Earth’s climate system,Antarctic sea ice has demonstrated significant variability over the satellite era.Here,we identify a remarkable decadal transition in the total Antarctic Sea Ice Extent(SIE).The stage from 1979 to 2006 is characterized by high-frequency(i.e.,seasonal to interannual)temporal variability in SIE and zonal asymmetry in Sea Ice Concentration(SIC),which is primarily under the control of the Amundsen Sea Low(ASL).After 2007,however,sea ice changes exhibit a more spatially homogeneous pattern in SIC and a more temporally long-lasting mode in SIE.Further analysis reveals that sea ice-ocean interaction plays a major role in the low-frequency(i.e.,multiannual)variability of Antarctic sea ice from 2007−22.The related physical process is inferred to manifest as a strong coupling between the surface and the subsurface ocean layers,involving enhanced vertical convection and the downward delivery of the surface anomalies related to ice melting and freezing processes,thus maintaining the SIE anomalies for a longer time.Furthermore,this process mainly occurs in the Amundsen-Bellingshausen Sea(ABS)sector,and the weakened subsurface ocean stratification is the key factor triggering the coupling process in this region.We find that the Circumpolar Deep Water(CDW)over the ABS sector continued to shoal before 2007 and remained stable thereafter.It is speculated that the shoaling of the CDW may be a possible driver leading to the weakening of the subsurface stratification.
基金Supported by the State Key Program of National Natural Science of China(No.60638020)
文摘The state-of-the-art OpenFOAM technology is used to develop a numerical model that can be devoted to numerically investigating wake-collapse internal waves generated by a submerged moving body.The model incorporates body geometry,propeller forcing,and stratification magnitude of seawater.The generation mechanism and wave properties are discussed based on model results.It was found that the generation of the wave and its properties depend greatly on the body speed.Only when that speed exceeds some critical value,between 1.5 and 4.5 m/s,can the moving body generate wake-collapse internal waves,and with increases of this speed,the time of generation advances and wave amplitude increases.The generated wake-collapse internal waves are confirmed to have characteristics of the second baroclinic mode.As the body speed increases,wave amplitude and length increase and its waveform tends to take on a regular sinusoidal shape.For three linearly temperature-stratified profiles examined,the weaker the stratification,the stronger the wake-collapse internal wave.
基金supported by "973 Program" (Grant No. 2011CB808800)National Natural Science Foundation of China (Grant Nos. 40830212,40921062,41172312)+2 种基金Doctoral Fund of Ministry of Education of China (Grant No. 200804910503)Fund of State Key Laboratory of Biogeology and Environmental Geology(Grant No. BGEG0802)Scientific and Technological Project of Jiangxi (Grant No. GJJ10623)
文摘Carbonate carbon isotope （δ^13Ccarb） has received considerable attention in the Permian-Triassic transition for its rapid negative shift coinciding with the great end-Permian mass extinction event. The mechanism has long been debated for such a c~ δ^13Ccarb negative excursion through the end-Permian crisis and subsequent large perturbations in the entire Early Triassic. A δ^13Ccarb depth gradient is observed at the Permian-Triassic boundary sections of different water-depths, i.e., the Yangou, Meishan, and Shangsi sections, and such a large δ^13Ccarb-depth gradient near the end-Permian mass extinction horizon is believed to result from a stratified Paleotethys Ocean with widespread anoxic/euxinic deep water. The evolution of δ^13Ccarb-depth gradient com- bined with paleontological and geochemical data suggests that abundant cyanobacteria and vigorous biological pump in the immediate aftermath of the end-Permian extinction would be the main cause of the large δ^13Ccarb-depth gradient, and the enhanced continental weathering with the mass extinction on land provides a mass amount of nutriment for the flourishing cyanobacteria. Photic zone anoxia/euxinia from the onset of chemocline upward excursion might be the direct cause for the mass extinction whereas the instability of chemocline in the stratified Early Triassic ocean would be the reason for the delayed and involuted biotic recovery.
