The heat content(HC)of water masses on the Ross Sea continental shelf plays an important role in regulating the circulations and the basal melting of the Ross Ice Shelf(RIS).Yet,the evolution of the HC on the Ross Sea...The heat content(HC)of water masses on the Ross Sea continental shelf plays an important role in regulating the circulations and the basal melting of the Ross Ice Shelf(RIS).Yet,the evolution of the HC on the Ross Sea continental shelf is still not clear due to the sparsity of observations.By employing a coupled regional ocean-sea ice-ice shelf model for the Ross Sea,this study analyzes the heat budget of water masses over the continental shelf and in the RIS cavity.According to the topographic features and the HC density,the continental shelf region is divided into 17 subdomains.The heat budget of the middle layer for every subdomain is analyzed.In addition,the heat budget for the RIS cavity is assessed for the first time.Owing to Modified Circumpolar Deep Water intrusion,water masses over the eastern shelf are warmer than over the western shelf,with the coldest water identified in the southwestern inner shelf.The horizontal heat flux mainly provides heat to the continental shelf,while the atmospheric forcing tends to warm up the ocean during the ice-melting period and cool down the ocean during the ice-freezing period.The vertical heat flux is generally upward and transports heat from the deep layer to the upper layer.In the RIS cavity,the seasonal cycle of the HC is dominated by the horizontal flux across the RIS front rather than the basal thermal forcing of the RIS.展开更多
Seasonal variation in phytoplankton composition influences the pathways and efficiency of energy flow,reshaping the structure of the trophic pyramid in the Ross Sea.However,field investigation of grazing processes pre...Seasonal variation in phytoplankton composition influences the pathways and efficiency of energy flow,reshaping the structure of the trophic pyramid in the Ross Sea.However,field investigation of grazing processes presents challenges that hinder our understanding of energy pathways.This study aims to provide insights into energy flow using a three-dimensional ecosystem model applied to the Ross Sea.By analyzing the simulation results,the role of the seasonal phytoplankton succession,specifically the shift from dominance by Phaeocystis antarctica to diatoms,in energy allocation is explored.The short-lived spring bloom of P.antarctica mainly fuels microzooplankton,creating a brief food chain where energy transfers primarily among smaller plankton.In contrast,the subsequent summer bloom of diatoms,which persists longer,provides nearly half of the total phytoplankton energy loss(via ingestion and mortality)to larger mesozooplankton.Our findings indicate that phytoplankton succession in the Ross Sea extends the bloom duration,particularly for diatoms,thereby facilitating energy transfer to higher trophic levels and improving overall energy utilization.This suggests that phytoplankton succession,an ecological strategy adapted to iron-deficient environments in the Ross Sea,explains why the colder region in front of the Ross Ice Shelf is significantly more productive than the northern areas,ultimately favored by top predators.展开更多
The oceanic general circulations in the Ross Sea,where the southernmost ocean is located,play an important role in the climate system.Yet,the energy cycle of oceanic circulations in the Ross Sea is still unclear.By em...The oceanic general circulations in the Ross Sea,where the southernmost ocean is located,play an important role in the climate system.Yet,the energy cycle of oceanic circulations in the Ross Sea is still unclear.By employing an eddypermitting coupled regional ocean-sea ice-ice shelf model,this study investigates the oceanic energy cycle in the Ross Sea.Based on the Lorenz Energy Cycle framework,the spatiotemporal distributions of kinetic energy and available potential energy within the Ross Sea are quantitatively analyzed.The power pathways and magnitudes of energy conversion are also quantified.The simulated results show that the Mean Available Potential Energy(MAPE)is the largest energy reservoir of about 527.62 PJ(1 PJ=10^(15) J),followed by the Eddy Available Potential Energy(EAPE),the Mean Kinetic Energy(MKE),and the Eddy Kinetic Energy(EKE)of about 19.20 PJ,1.04 PJ,and 0.82 PJ,respectively.In the sub-ice-shelf cavity,the maximal MAPE is up to about 177.81 PJ,and the EAPE,MKE,and EKE are about 2.58 PJ,39.87 TJ(1 TJ=10^(12) J),and 23.05 TJ,respectively.The inputs to the regional energy reservoirs are mainly from the sea surface momentum and buoyancy fluxes.The baroclinic pathway plays a dominant role in the conversion of energy to EKE,both in the open ocean and in the sub-ice-shelf cavity.The energy conversion from EAPE to EKE in the open ocean and the sub-ice-shelf cavity is about 2.86 GW(1 GW=10^(9) J)and 162.18 MW(1 MW=10^(6) J),respectively.In addition,the kinetic energy is directed from EKE to MKE in the Ross Sea,and such an energy flow in the barotropic pathway is opposite from that in the Southern Ocean.展开更多
Research on changes in the redox conditions of bottom waters is essential for understanding deep water circulation,global ocean currents,climate change,and ecosystem health.Through sedimentary geological methods,a dee...Research on changes in the redox conditions of bottom waters is essential for understanding deep water circulation,global ocean currents,climate change,and ecosystem health.Through sedimentary geological methods,a deeper understanding of the complex relationships between various environmental changes can be achieved,providing detailed evidence and theoretical support for global climate change research.The Ross Sea in Antarctica plays a key role in the formation of Antarctic bottom water(AABW),and the complex climate changes since the last glacial maximum(LGM)make it particularly significant for study.This research analyzes core ANT32-RB16C from the Ross Sea using geochemical proxies such as major and trace elements,grain size,and redox-sensitive indicators like Mn/Ti,Co/Ti,Mo/Ti,Cd/Ti,U/Th,and Ni/Co molar concentration ratios.Combining this data with a previously established chronological framework,the study explores the evolution of redox conditions in the Ross Sea’s deep waters since the LGM.The results show that the deep waters have remained oxygen-rich since the LGM,with significant changes in four stages.Stage 1(24.7–15.7 cal ka BP):Strong oxidizing conditions,likely due to enhanced formation of Ross Sea bottom water(RSBW),increasing oxygen levels.Stage 2(15.7–4.5 cal ka BP):Weakened oxidizing conditions as temperatures rose and ice shelves retreated,increasing primary productivity and depleting oxygen.Stage 3(4.5–1.5 cal ka BP):Continued decline in oxidizing conditions,possibly linked to high primary productivity and oxygen consumption.Stage 4(1.5 cal ka BP to present):A rapid recovery of oxidizing conditions,likely driven by temperature drops,increased RSBW formation,and decreased productivity.展开更多
Antarctic coastal polynyas play a vital role in atmosphere-ocean interactions and local ecosystems.This study investigates the interannual variability of springtime coastal polynyas over the Ross Sea based on satellit...Antarctic coastal polynyas play a vital role in atmosphere-ocean interactions and local ecosystems.This study investigates the interannual variability of springtime coastal polynyas over the Ross Sea based on satellite-retrieved sea-ice concentration(SIC)data from 1992 to 2021.Firstly,the springtime coastal polynya areas display large interannual variability as well as a positive trend of about 2000 km^(2)(10 yr)^(-1) over the 30 years.Secondly,based on composite analysis,in spring,we find that a deepened Amundsen Sea Low(ASL)induces stronger meridional winds over the eastern Ross Sea,leading to stronger sea-ice advection and expansion of coastal polynya areas.This is accompanied by more solar radiation absorption in early summer(about 16 W m^(2)),resulting in upper-ocean warming(~0.4℃)and significant sea-ice loss in late summer(~50%SIC).Additionally,the physical processes are validated by 500-year piControl simulations of a state-of-the-art Earth system model.Based on the same composite analysis,the results show that the sea-ice decline is consistent with the deepening of the ASL and the increase of the meridional sea-ice advection of the preceding spring,which is highly consistent with that of observations.This further confirms the circulations-polynyas-sea-ice physical linkages.Since the springtime ASL is strongly modulated by the tropical Pacific variability and the stratospheric polar vortex,changes in the polynya areas of the Ross Sea can be traced back to remote regions.展开更多
Changes in the marine productivity and sedimentary environment since the last deglaciation in the Ross Sea are presented in this paper.Opal has replaced calcium carbonate as the major biogenic component and has a sign...Changes in the marine productivity and sedimentary environment since the last deglaciation in the Ross Sea are presented in this paper.Opal has replaced calcium carbonate as the major biogenic component and has a significantly positive correlation with total organic carbon(TOC),which indicates that siliceous phytoplankton controlled the absorption and release of carbon by the biological pump and was the main producer of marine organic matter.Using the AMS 14C age framework,foraminiferal fossils and redox sensitive elements(RSEs),we found that both the sedimentary environment and marine productivity changed clearly in^11 cal ka BP,which is more likely related with the melting and retreat of the Ross Ice Shelf.In addition,the increase of marine productivity promoted the sinking of more organic-matter to the seabed.A large proportion of oxygen in the bottom water body was consumed and more carbon dioxide was produced during the decomposition of organic matter,making the bottom water body more soluble to calcium carbonate.展开更多
The carbon isotopic composition of organic matter （δ^13Corg） was determined in two sediment cores （IIL1 and IIL9） recovered from Inexpressible Island, Ross Sea, Antarctica, and analyzed to identify the sources of...The carbon isotopic composition of organic matter （δ^13Corg） was determined in two sediment cores （IIL1 and IIL9） recovered from Inexpressible Island, Ross Sea, Antarctica, and analyzed to identify the sources of that organic matter. The δ^13Corg values of sediments of IIL9 were found to vary between -14.6‰ and -11.6‰, with a mean of-13.4‰ （n=48）. These values were significantly higher than those of IIL1 sediments which varied between -23.2‰ and -20.4‰, with a mean of-21.8%o （n=55）. The variation in δ^13Corg values in these two sediment cores indicate different sources of organic matter, The relatively high 6~3Corg values in IIL9 are in accordance with a source from algae, while the low δ^13Corg values in IIL1 evince significant influence from penguin guano with algae as the secondary source. Compared with the reference data from other high-latitude lake sediments and plants, the δ^13Corg values in IIL9 were extremely high, a result likely related to intense competition for CO2 assimilation among algal species during the growing season in this relatively shallow pond. These results indicate that sedimentary δ^13Corg is a reliable proxy for paleo-primary productivity in ponds at Inexpressible Island.展开更多
Investigating the multiple proxies involving productivity,organic geochemistry,and trace element(TE)enrichment in surface sediments could be used as paleoenvironment archives to gain insights into past and future envi...Investigating the multiple proxies involving productivity,organic geochemistry,and trace element(TE)enrichment in surface sediments could be used as paleoenvironment archives to gain insights into past and future environmental conditions changes.We present redox-sensitive TEs(Mn,Ni,Cu,U,P,Mo,Co,V,Zn,and Cd),productivity-related proxies(total organic carbon and opal),and total nitrogen and CaCO_(3) contents of bulk surface sediments of this area.The productivity proxies from the shelf and coastal regions of the Ross and the Amundsen seas showed that higher productivity was affiliated with an area of nutrient-rich deep water upwelling.The upwelling of weakly corrosive deep water may be beneficial for preserving CaCO_(3),while highly corrosive dense water,if it forms on the shelf near the coastal region(coastal polynya),could limit the preservation of CaCO_(3) in modern conditions.There were no oxic or anoxic conditions in the study area,as indicated by the enrichment factors of redox-sensitive TEs(Mn,Co,and U).The enrichment factor of Cd,which is redox-sensitive,indicated suboxic redox conditions in sediment environments because of high primary productivity and organic matter preservation/decomposition.The enrichment factors of other redox-sensitive TEs(P,Ni,Cu,V,and Zn)and the correlations between the element/Ti ratio with productivity and nutrient proxies indicated that the organic matter decomposed,and there was massive burial of phytoplankton biomass.There was variation in the enrichment,such that sediments were enriched in P,Mo,and Zn,but depleted in Ni,Cu,and V.展开更多
The Ross Sea region is a biologically rich and dynamic environment and,although protected under various instruments of the Antarctic Treaty System,is threatened by a changing climate and increasing human activities lo...The Ross Sea region is a biologically rich and dynamic environment and,although protected under various instruments of the Antarctic Treaty System,is threatened by a changing climate and increasing human activities locally and globally.This opinion editorial describes the importance of research and monitoring in the Ross Sea and identifies opportunities and barriers to enhance them.展开更多
Information on tintinnid horizontal distribution in the Antarctic Continental Zone is scarce.During the summer of 2019/2020,tintinnid diversity and horizontal distribution in surface waters were investigated in the Ro...Information on tintinnid horizontal distribution in the Antarctic Continental Zone is scarce.During the summer of 2019/2020,tintinnid diversity and horizontal distribution in surface waters were investigated in the Ross Sea and Amundsen Sea polynya.Eight tintinnid species were found and the dominant species showed obvious horizontal distribution characteristics.In the Ross Sea,three tintinnid community groups were identified.Cymatocylis cristallina and Laackmanniella prolongata(group I)were dominant species and were mainly distributed in stations closer to the coast than were species in the other two groups.Codonellopsis gaussi(group II)and Cy.convallaria(group III)were mainly distributed in nearshore and offshore stations,respectively.In the Amundsen Sea polynya,the dominant species Cy.cristallina,L.prolongata and Salpingella faurei(group I)were mainly distributed in stations closer to the coast than were species in the other two groups.Cy.convallaria(group III)was mainly distributed in offshore stations.The distribution area where C.gaussi and C.cristallina were found in high abundance and abundance proportion of loricae with protoplasts was divided by the approximate boundary of the Antarctic Slope Front Current and Coastal Current in the Ross Sea.The highest abundance proportion in the Ross Sea was the 32-36μm lorica oral diameter(LOD)size class(75.7%),and the 36-40μm LOD size class(56.0%)was found in the Amundsen Sea polynya.Temperature-salinity-plankton diagrams of the two seas revealed that temperature may be the main reason for species distribution.Our results contribute to a better understanding of horizontal distribution of the microbial food web,and serve as a baseline for future studies of pelagic community change in the Antarctic Continental Zone.展开更多
The highly reactive iron(FeHR)in marine sediments is a key driver of the iron-carbon coupled biogeochemical cycle.However,rare is known on its speciation and environmental regulation mechanisms in the climate-sensitiv...The highly reactive iron(FeHR)in marine sediments is a key driver of the iron-carbon coupled biogeochemical cycle.However,rare is known on its speciation and environmental regulation mechanisms in the climate-sensitive West Antarctic region.This study investigated the spatial distribution of FeHRcontent and composition in surface sediments of the Ross Sea,examined the synergistic regulatory mechanisms of chemical weathering intensity(quantified by the chemical index of alteration,CIA),bedrock properties and glacial meltwater input on FeHRcharacteristics,and elucidated the interaction between FeHRand total organic carbon(TOC),and its implications for the sedimentary environment.Basically,the CIA(52.7±1.46)and FeHR/FeT ratio(0.20±0.02)are higher in the eastern Ross Sea than the western(45.4±2.73 and 0.17±0.01),probably resulting from the selective enrichment of fine-grained materials subjected to intense chemical weathering under low sedimentation rates.Interestingly,the CIA(37.6±5.45)is lowest,but FeHR/FeT ratio(0.25±0.01)is highest in the southwestern Ross Sea,mainly due to igneous bedrock,katabatic winds and glacial meltwater input in a weakly weathered environment.Relative high TOC/FeHRratios(1.29±0.30 and 1.04±0.70)in the southwestern and western Ross Sea indicate a sedimentary environment with high primary production and exogenous FeHRinputs.While,relative low TOC/FeHRratio(0.63±0.13)in the eastern Ross Sea indicates the dual control of strong TOC remineralization and intense chemical weathering-derived FeHRproduction.The chemical weathering intensity is the primary controlling factor for FeHRcontent and composition in marine sediments globally,according to the significant positive correlations between FeHR/FeT ratios and CIA values(r=0.80)as well as FeT content(r=0.57).The unique glacial meltwater and lithological characteristics of the Antarctic region can significantly influence local FeHR/FeT ratio,thereby regulating bioavailable Fe supply and TOC preservation.This finding provides new regional constraints for understanding iron-carbon coupling processes in polar regions.展开更多
Seafloor and buried reliefs occur along continental margin of the Ross Sea(Antarctica).These features are several kilometres wide and tens of metres high,exhibiting cone or flat-top dome shapes.Previous studies have p...Seafloor and buried reliefs occur along continental margin of the Ross Sea(Antarctica).These features are several kilometres wide and tens of metres high,exhibiting cone or flat-top dome shapes.Previous studies have proposed a volcanic or glacial origin for these formations,but these hypotheses do not account for all the available evidence.In this study,we use morpho-bathymetric data,intermediate resolution multichannel seismic and high resolution chirp profiles,as well as magnetic lines to investigate these clusters of mounds.By employing targeted processing techniques to enhance the geophysical characterization of the seafloor and buried reliefs,and to understand the underlying geological features,we propose that the reliefs are mud volcanoes.Some of these formations appear to be associated with a plumbing system,as indicated by acoustic anomalies linked to sediment containing gas.These formations are likely fed by clayey source rocks of Miocene age.Additionally,other reliefs might be the result of mud mobilisation caused by gravity instability and fluid overpressure.展开更多
Marine geophysical survey by the Chinese National Antarctic Research Expedition （CHINARE） began with the first science expedition in 1984/1985, although only four cruises were performed in the vicinity of the Antar...Marine geophysical survey by the Chinese National Antarctic Research Expedition （CHINARE） began with the first science expedition in 1984/1985, although only four cruises were performed in the vicinity of the Antarctic Peninsula between then and 1991/1992. After a 20 year hiatus, Antarctic marine geophysical research was relaunched by the Chinese Polar Environmental Comprehensive Investigation and Assessment Programs （known simply as the Chinese Polar Program） in 2011/2012. Integrated geophysical surveys have been carried out annually since, in Prydz Bay and the Ross Sea. During the last 5 years, we have acquired about 5500 km of bathymetric, gravimetric, and magnetic lines; more than 1800 km of seismic reflection lines; and data from several heat flow and Ocean Bottom Seismometer （OBS） stations. This work has deepened understandings of geophysical features and their implications for geological tectonics and glacial history in Antarctica and its surrounding seas. Compiled Antarctic Bouguer and Airy isostatic gravity anomalies show different features of tectonics between the East Antarctic stability and West Antarctic activity. Calculated magnetic anomalies, heat flow anomalies and lithospheric anisotropy offshore of Prydz Bay may imply high heat capacity of mantle shielded by the continental shelf lithosphere, but high heat dissipation of mantle due to the Cretaceous breakup of Gondwana along the continent and ocean transition （COT）, where large sediment ridges would be brought about by the Oligocene ice sheet retreat and would enlarge free-air gravity anomalies. In the western Ross Sea, CHINARE seismic profiles indicate northern termination of the Terror Rift and deposition time of the grounding zone wedge in the northern JOIDES Basin.展开更多
During the 36th Chinese National Antarctic Research Expedition,aerosol samples were gathered from the Ross Sea in Antarctic to assess the climatic impact of the Australian fires that occurred in 2019-2020.The chemical...During the 36th Chinese National Antarctic Research Expedition,aerosol samples were gathered from the Ross Sea in Antarctic to assess the climatic impact of the Australian fires that occurred in 2019-2020.The chemical compositions,including levoglucosan(Lev)and its isomers,galactosan(Gan)and mannosan(Man),were analyzed.Principal component analysis helped identify the potential sources of these chemical components.By combining backward trajectories with the ratios of CLev/CMan and CMan/CGan,it was further inferred that Australia might be the potential source region for biomass burning.The radiative forcing resulting from biomass burning was evaluated using the Santa Barbara DISORT Atmospheric Radiative Transfer(SBDART)model,which revealed that black carbon emitted from biomass burning could slightly warm the atmosphere(+0.52 W·m^(-2))while causing slightly cooling at the surface(-0.73 W·m^(-2))and the top of the atmosphere(-0.22 W·m^(-2))over the Ross Sea.展开更多
基金supported by the National Key R&D Program of China (Grant No. 2024YFF0506603)the Independent Research Foundation of the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (Grant Nos. SML2023SP201 and SML2021SP306)+2 种基金the Natural Science Foundation of Guangdong Province, China (Grant No. 2024A1515012717)the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (Grant Nos. 313021004, 313022009 and 313022001)the Program of Innovation 2030 on Smart Ocean, Zhejiang University
文摘The heat content(HC)of water masses on the Ross Sea continental shelf plays an important role in regulating the circulations and the basal melting of the Ross Ice Shelf(RIS).Yet,the evolution of the HC on the Ross Sea continental shelf is still not clear due to the sparsity of observations.By employing a coupled regional ocean-sea ice-ice shelf model for the Ross Sea,this study analyzes the heat budget of water masses over the continental shelf and in the RIS cavity.According to the topographic features and the HC density,the continental shelf region is divided into 17 subdomains.The heat budget of the middle layer for every subdomain is analyzed.In addition,the heat budget for the RIS cavity is assessed for the first time.Owing to Modified Circumpolar Deep Water intrusion,water masses over the eastern shelf are warmer than over the western shelf,with the coldest water identified in the southwestern inner shelf.The horizontal heat flux mainly provides heat to the continental shelf,while the atmospheric forcing tends to warm up the ocean during the ice-melting period and cool down the ocean during the ice-freezing period.The vertical heat flux is generally upward and transports heat from the deep layer to the upper layer.In the RIS cavity,the seasonal cycle of the HC is dominated by the horizontal flux across the RIS front rather than the basal thermal forcing of the RIS.
基金The National Natural Science Foundation of China under contract No.41941008the National Key Research and Development Program of China under contract No.2023YFC3107702.
文摘Seasonal variation in phytoplankton composition influences the pathways and efficiency of energy flow,reshaping the structure of the trophic pyramid in the Ross Sea.However,field investigation of grazing processes presents challenges that hinder our understanding of energy pathways.This study aims to provide insights into energy flow using a three-dimensional ecosystem model applied to the Ross Sea.By analyzing the simulation results,the role of the seasonal phytoplankton succession,specifically the shift from dominance by Phaeocystis antarctica to diatoms,in energy allocation is explored.The short-lived spring bloom of P.antarctica mainly fuels microzooplankton,creating a brief food chain where energy transfers primarily among smaller plankton.In contrast,the subsequent summer bloom of diatoms,which persists longer,provides nearly half of the total phytoplankton energy loss(via ingestion and mortality)to larger mesozooplankton.Our findings indicate that phytoplankton succession in the Ross Sea extends the bloom duration,particularly for diatoms,thereby facilitating energy transfer to higher trophic levels and improving overall energy utilization.This suggests that phytoplankton succession,an ecological strategy adapted to iron-deficient environments in the Ross Sea,explains why the colder region in front of the Ross Ice Shelf is significantly more productive than the northern areas,ultimately favored by top predators.
基金The Independent Research Foundation of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)under contract No.SML2023SP201the Natural Science Foundation of Guangdong Province,China under contract No.2024A1515012717+3 种基金the Funds of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)under contract Nos 313021004 and 313022009the National Natural Science Foundation of China under contract No.41806216the Natural Science Foundation of Jiangsu Province under contract No.BK20211015the Program of Innovation 2030 on Smart Ocean,Zhejiang University.
文摘The oceanic general circulations in the Ross Sea,where the southernmost ocean is located,play an important role in the climate system.Yet,the energy cycle of oceanic circulations in the Ross Sea is still unclear.By employing an eddypermitting coupled regional ocean-sea ice-ice shelf model,this study investigates the oceanic energy cycle in the Ross Sea.Based on the Lorenz Energy Cycle framework,the spatiotemporal distributions of kinetic energy and available potential energy within the Ross Sea are quantitatively analyzed.The power pathways and magnitudes of energy conversion are also quantified.The simulated results show that the Mean Available Potential Energy(MAPE)is the largest energy reservoir of about 527.62 PJ(1 PJ=10^(15) J),followed by the Eddy Available Potential Energy(EAPE),the Mean Kinetic Energy(MKE),and the Eddy Kinetic Energy(EKE)of about 19.20 PJ,1.04 PJ,and 0.82 PJ,respectively.In the sub-ice-shelf cavity,the maximal MAPE is up to about 177.81 PJ,and the EAPE,MKE,and EKE are about 2.58 PJ,39.87 TJ(1 TJ=10^(12) J),and 23.05 TJ,respectively.The inputs to the regional energy reservoirs are mainly from the sea surface momentum and buoyancy fluxes.The baroclinic pathway plays a dominant role in the conversion of energy to EKE,both in the open ocean and in the sub-ice-shelf cavity.The energy conversion from EAPE to EKE in the open ocean and the sub-ice-shelf cavity is about 2.86 GW(1 GW=10^(9) J)and 162.18 MW(1 MW=10^(6) J),respectively.In addition,the kinetic energy is directed from EKE to MKE in the Ross Sea,and such an energy flow in the barotropic pathway is opposite from that in the Southern Ocean.
基金The National Key R&D Program of China under contract No. 2023YFC28 11305the Scientific Research Fund of the Second Institute of Oceanography,MNR under contract No. SZ2405the Impact and Response of Antarctic Seas to Climate Change under contract No. IRASCC
文摘Research on changes in the redox conditions of bottom waters is essential for understanding deep water circulation,global ocean currents,climate change,and ecosystem health.Through sedimentary geological methods,a deeper understanding of the complex relationships between various environmental changes can be achieved,providing detailed evidence and theoretical support for global climate change research.The Ross Sea in Antarctica plays a key role in the formation of Antarctic bottom water(AABW),and the complex climate changes since the last glacial maximum(LGM)make it particularly significant for study.This research analyzes core ANT32-RB16C from the Ross Sea using geochemical proxies such as major and trace elements,grain size,and redox-sensitive indicators like Mn/Ti,Co/Ti,Mo/Ti,Cd/Ti,U/Th,and Ni/Co molar concentration ratios.Combining this data with a previously established chronological framework,the study explores the evolution of redox conditions in the Ross Sea’s deep waters since the LGM.The results show that the deep waters have remained oxygen-rich since the LGM,with significant changes in four stages.Stage 1(24.7–15.7 cal ka BP):Strong oxidizing conditions,likely due to enhanced formation of Ross Sea bottom water(RSBW),increasing oxygen levels.Stage 2(15.7–4.5 cal ka BP):Weakened oxidizing conditions as temperatures rose and ice shelves retreated,increasing primary productivity and depleting oxygen.Stage 3(4.5–1.5 cal ka BP):Continued decline in oxidizing conditions,possibly linked to high primary productivity and oxygen consumption.Stage 4(1.5 cal ka BP to present):A rapid recovery of oxidizing conditions,likely driven by temperature drops,increased RSBW formation,and decreased productivity.
基金supported by the National Key R&D Program of China(Grant No.2021YFC2802504)the National Outstanding Youth Grant(Grant No.41925027)+1 种基金the National Natural Science Foundation of China(Grant No.42206251)the Innovation Group Project of the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(Grant No.311021008).
文摘Antarctic coastal polynyas play a vital role in atmosphere-ocean interactions and local ecosystems.This study investigates the interannual variability of springtime coastal polynyas over the Ross Sea based on satellite-retrieved sea-ice concentration(SIC)data from 1992 to 2021.Firstly,the springtime coastal polynya areas display large interannual variability as well as a positive trend of about 2000 km^(2)(10 yr)^(-1) over the 30 years.Secondly,based on composite analysis,in spring,we find that a deepened Amundsen Sea Low(ASL)induces stronger meridional winds over the eastern Ross Sea,leading to stronger sea-ice advection and expansion of coastal polynya areas.This is accompanied by more solar radiation absorption in early summer(about 16 W m^(2)),resulting in upper-ocean warming(~0.4℃)and significant sea-ice loss in late summer(~50%SIC).Additionally,the physical processes are validated by 500-year piControl simulations of a state-of-the-art Earth system model.Based on the same composite analysis,the results show that the sea-ice decline is consistent with the deepening of the ASL and the increase of the meridional sea-ice advection of the preceding spring,which is highly consistent with that of observations.This further confirms the circulations-polynyas-sea-ice physical linkages.Since the springtime ASL is strongly modulated by the tropical Pacific variability and the stratospheric polar vortex,changes in the polynya areas of the Ross Sea can be traced back to remote regions.
基金Supported by the Public Science and Technology Research Funds Projects of Ocean(No.201105003-2)the Chinese Polar Environment Comprehensive Investigation&Assessment Programs(No.CHINARE2016-01-02)。
文摘Changes in the marine productivity and sedimentary environment since the last deglaciation in the Ross Sea are presented in this paper.Opal has replaced calcium carbonate as the major biogenic component and has a significantly positive correlation with total organic carbon(TOC),which indicates that siliceous phytoplankton controlled the absorption and release of carbon by the biological pump and was the main producer of marine organic matter.Using the AMS 14C age framework,foraminiferal fossils and redox sensitive elements(RSEs),we found that both the sedimentary environment and marine productivity changed clearly in^11 cal ka BP,which is more likely related with the melting and retreat of the Ross Ice Shelf.In addition,the increase of marine productivity promoted the sinking of more organic-matter to the seabed.A large proportion of oxygen in the bottom water body was consumed and more carbon dioxide was produced during the decomposition of organic matter,making the bottom water body more soluble to calcium carbonate.
基金the Chinese Arctic and Antarctic Administration of the State Oceanic Administration for project supportthe United States Antarctic Program (USAP)+2 种基金Antarctic Support Contract and Italian Mario Zucchelli Station for logistical support. R. Murray and A. Mc Kenzie provided valuable assistance in the fieldsupported by the National Natural Science Foundation of China (Grant nos. 41576183 and 41376124)National Science Foundation (Grant no. ANT 0739575)
文摘The carbon isotopic composition of organic matter （δ^13Corg） was determined in two sediment cores （IIL1 and IIL9） recovered from Inexpressible Island, Ross Sea, Antarctica, and analyzed to identify the sources of that organic matter. The δ^13Corg values of sediments of IIL9 were found to vary between -14.6‰ and -11.6‰, with a mean of-13.4‰ （n=48）. These values were significantly higher than those of IIL1 sediments which varied between -23.2‰ and -20.4‰, with a mean of-21.8%o （n=55）. The variation in δ^13Corg values in these two sediment cores indicate different sources of organic matter, The relatively high 6~3Corg values in IIL9 are in accordance with a source from algae, while the low δ^13Corg values in IIL1 evince significant influence from penguin guano with algae as the secondary source. Compared with the reference data from other high-latitude lake sediments and plants, the δ^13Corg values in IIL9 were extremely high, a result likely related to intense competition for CO2 assimilation among algal species during the growing season in this relatively shallow pond. These results indicate that sedimentary δ^13Corg is a reliable proxy for paleo-primary productivity in ponds at Inexpressible Island.
基金financially supported by National Polar Special Program “Impact and Response of Antarctic Seas to Climate Change” (Grant nos. IRASCC 01-03-02 and 02-03)supported by the Basic Scientific Fund for National Public Research Institutes of China (Grant no. 2019Q09)the National Natural Science Foundation of China (Grant nos. 41976080 and 41406220)。
文摘Investigating the multiple proxies involving productivity,organic geochemistry,and trace element(TE)enrichment in surface sediments could be used as paleoenvironment archives to gain insights into past and future environmental conditions changes.We present redox-sensitive TEs(Mn,Ni,Cu,U,P,Mo,Co,V,Zn,and Cd),productivity-related proxies(total organic carbon and opal),and total nitrogen and CaCO_(3) contents of bulk surface sediments of this area.The productivity proxies from the shelf and coastal regions of the Ross and the Amundsen seas showed that higher productivity was affiliated with an area of nutrient-rich deep water upwelling.The upwelling of weakly corrosive deep water may be beneficial for preserving CaCO_(3),while highly corrosive dense water,if it forms on the shelf near the coastal region(coastal polynya),could limit the preservation of CaCO_(3) in modern conditions.There were no oxic or anoxic conditions in the study area,as indicated by the enrichment factors of redox-sensitive TEs(Mn,Co,and U).The enrichment factor of Cd,which is redox-sensitive,indicated suboxic redox conditions in sediment environments because of high primary productivity and organic matter preservation/decomposition.The enrichment factors of other redox-sensitive TEs(P,Ni,Cu,V,and Zn)and the correlations between the element/Ti ratio with productivity and nutrient proxies indicated that the organic matter decomposed,and there was massive burial of phytoplankton biomass.There was variation in the enrichment,such that sediments were enriched in P,Mo,and Zn,but depleted in Ni,Cu,and V.
基金funded by the Antarctic and Southern Ocean Coalition (www.asoc.org)
文摘The Ross Sea region is a biologically rich and dynamic environment and,although protected under various instruments of the Antarctic Treaty System,is threatened by a changing climate and increasing human activities locally and globally.This opinion editorial describes the importance of research and monitoring in the Ross Sea and identifies opportunities and barriers to enhance them.
基金financially supported by National Polar Special Program “Impact and Response of Antarctic Seas to Climate Change” (Grant no. IRASCC 01-02-01D)funded by the China Postdoctoral Science Foundation (Grant no., 2020M672149)the Applied Research Project for Postdoctoral in Qingdao。
文摘Information on tintinnid horizontal distribution in the Antarctic Continental Zone is scarce.During the summer of 2019/2020,tintinnid diversity and horizontal distribution in surface waters were investigated in the Ross Sea and Amundsen Sea polynya.Eight tintinnid species were found and the dominant species showed obvious horizontal distribution characteristics.In the Ross Sea,three tintinnid community groups were identified.Cymatocylis cristallina and Laackmanniella prolongata(group I)were dominant species and were mainly distributed in stations closer to the coast than were species in the other two groups.Codonellopsis gaussi(group II)and Cy.convallaria(group III)were mainly distributed in nearshore and offshore stations,respectively.In the Amundsen Sea polynya,the dominant species Cy.cristallina,L.prolongata and Salpingella faurei(group I)were mainly distributed in stations closer to the coast than were species in the other two groups.Cy.convallaria(group III)was mainly distributed in offshore stations.The distribution area where C.gaussi and C.cristallina were found in high abundance and abundance proportion of loricae with protoplasts was divided by the approximate boundary of the Antarctic Slope Front Current and Coastal Current in the Ross Sea.The highest abundance proportion in the Ross Sea was the 32-36μm lorica oral diameter(LOD)size class(75.7%),and the 36-40μm LOD size class(56.0%)was found in the Amundsen Sea polynya.Temperature-salinity-plankton diagrams of the two seas revealed that temperature may be the main reason for species distribution.Our results contribute to a better understanding of horizontal distribution of the microbial food web,and serve as a baseline for future studies of pelagic community change in the Antarctic Continental Zone.
基金jointly supported by the National Key Research and Development Program of China(Grant No.2022YFE0136500)the National Natural Science Foundation of China(NSFC)(Grant No.41976228)+2 种基金the scientific research fund of Second Institute of Oceanography,MNR(Grant No.JG1805)the National Polar Special Program“Impact and Response of Antarctic Seas to Climate Change”(Grant Nos.IRASCC 01-01-02A and 02-02)the China Scholarship Council(Grant No.201704180017)。
文摘The highly reactive iron(FeHR)in marine sediments is a key driver of the iron-carbon coupled biogeochemical cycle.However,rare is known on its speciation and environmental regulation mechanisms in the climate-sensitive West Antarctic region.This study investigated the spatial distribution of FeHRcontent and composition in surface sediments of the Ross Sea,examined the synergistic regulatory mechanisms of chemical weathering intensity(quantified by the chemical index of alteration,CIA),bedrock properties and glacial meltwater input on FeHRcharacteristics,and elucidated the interaction between FeHRand total organic carbon(TOC),and its implications for the sedimentary environment.Basically,the CIA(52.7±1.46)and FeHR/FeT ratio(0.20±0.02)are higher in the eastern Ross Sea than the western(45.4±2.73 and 0.17±0.01),probably resulting from the selective enrichment of fine-grained materials subjected to intense chemical weathering under low sedimentation rates.Interestingly,the CIA(37.6±5.45)is lowest,but FeHR/FeT ratio(0.25±0.01)is highest in the southwestern Ross Sea,mainly due to igneous bedrock,katabatic winds and glacial meltwater input in a weakly weathered environment.Relative high TOC/FeHRratios(1.29±0.30 and 1.04±0.70)in the southwestern and western Ross Sea indicate a sedimentary environment with high primary production and exogenous FeHRinputs.While,relative low TOC/FeHRratio(0.63±0.13)in the eastern Ross Sea indicates the dual control of strong TOC remineralization and intense chemical weathering-derived FeHRproduction.The chemical weathering intensity is the primary controlling factor for FeHRcontent and composition in marine sediments globally,according to the significant positive correlations between FeHR/FeT ratios and CIA values(r=0.80)as well as FeT content(r=0.57).The unique glacial meltwater and lithological characteristics of the Antarctic region can significantly influence local FeHR/FeT ratio,thereby regulating bioavailable Fe supply and TOC preservation.This finding provides new regional constraints for understanding iron-carbon coupling processes in polar regions.
文摘Seafloor and buried reliefs occur along continental margin of the Ross Sea(Antarctica).These features are several kilometres wide and tens of metres high,exhibiting cone or flat-top dome shapes.Previous studies have proposed a volcanic or glacial origin for these formations,but these hypotheses do not account for all the available evidence.In this study,we use morpho-bathymetric data,intermediate resolution multichannel seismic and high resolution chirp profiles,as well as magnetic lines to investigate these clusters of mounds.By employing targeted processing techniques to enhance the geophysical characterization of the seafloor and buried reliefs,and to understand the underlying geological features,we propose that the reliefs are mud volcanoes.Some of these formations appear to be associated with a plumbing system,as indicated by acoustic anomalies linked to sediment containing gas.These formations are likely fed by clayey source rocks of Miocene age.Additionally,other reliefs might be the result of mud mobilisation caused by gravity instability and fluid overpressure.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 41576069, 41306201, 41776189, 41706212 and 41706215)the Chinese Polar Environment Comprehensive Investigation & Assessment Programs (Grant Nos. CHINARE2017-01-03 and CHINARE2017-04-01)the Special Foundation of the Second Institute of Oceanography, SOA (Grant No. 14260-10)
文摘Marine geophysical survey by the Chinese National Antarctic Research Expedition （CHINARE） began with the first science expedition in 1984/1985, although only four cruises were performed in the vicinity of the Antarctic Peninsula between then and 1991/1992. After a 20 year hiatus, Antarctic marine geophysical research was relaunched by the Chinese Polar Environmental Comprehensive Investigation and Assessment Programs （known simply as the Chinese Polar Program） in 2011/2012. Integrated geophysical surveys have been carried out annually since, in Prydz Bay and the Ross Sea. During the last 5 years, we have acquired about 5500 km of bathymetric, gravimetric, and magnetic lines; more than 1800 km of seismic reflection lines; and data from several heat flow and Ocean Bottom Seismometer （OBS） stations. This work has deepened understandings of geophysical features and their implications for geological tectonics and glacial history in Antarctica and its surrounding seas. Compiled Antarctic Bouguer and Airy isostatic gravity anomalies show different features of tectonics between the East Antarctic stability and West Antarctic activity. Calculated magnetic anomalies, heat flow anomalies and lithospheric anisotropy offshore of Prydz Bay may imply high heat capacity of mantle shielded by the continental shelf lithosphere, but high heat dissipation of mantle due to the Cretaceous breakup of Gondwana along the continent and ocean transition （COT）, where large sediment ridges would be brought about by the Oligocene ice sheet retreat and would enlarge free-air gravity anomalies. In the western Ross Sea, CHINARE seismic profiles indicate northern termination of the Terror Rift and deposition time of the grounding zone wedge in the northern JOIDES Basin.
基金supported by the National Natural Science Foundation of China (Grant nos. 41941014 and 41930532)financially supported by National Polar Special Program “Impact and Response of Antarctic Seas to Climate Change”(Grant no. IRASCC 01-01-02E)。
文摘During the 36th Chinese National Antarctic Research Expedition,aerosol samples were gathered from the Ross Sea in Antarctic to assess the climatic impact of the Australian fires that occurred in 2019-2020.The chemical compositions,including levoglucosan(Lev)and its isomers,galactosan(Gan)and mannosan(Man),were analyzed.Principal component analysis helped identify the potential sources of these chemical components.By combining backward trajectories with the ratios of CLev/CMan and CMan/CGan,it was further inferred that Australia might be the potential source region for biomass burning.The radiative forcing resulting from biomass burning was evaluated using the Santa Barbara DISORT Atmospheric Radiative Transfer(SBDART)model,which revealed that black carbon emitted from biomass burning could slightly warm the atmosphere(+0.52 W·m^(-2))while causing slightly cooling at the surface(-0.73 W·m^(-2))and the top of the atmosphere(-0.22 W·m^(-2))over the Ross Sea.
