As a part of the National Report of China for the International Association for Physical Science of Ocean （IAPSO）, the main research results of Chinese scientists in Arctic physical oceanography during 2007-2010 are...As a part of the National Report of China for the International Association for Physical Science of Ocean （IAPSO）, the main research results of Chinese scientists in Arctic physical oceanography during 2007-2010 are reviewed in this paper. This period overlaps with the International Polar Year （IPY）, which is a catalyst for nations to emphasize activities and research in the polar regions. The Arctic also experienced a rapid change in sea ice, ocean, and climate during this time. China launched two Arctic cruises with the R/V XUE LONG icebreaker, in 2008 and 2010, which provided more opportunities for Chinese scientists to investigate the Arctic Ocean and its change. During this period, Chinese scientists participated in more than ten other cruises with international collaborations. The main research covered in this paper includes the upper ocean characteristic, ocean and sea ice optics, kinematics of sea ice and the Arctic impact on global climate change. The progress in sea ice optics, the observation technologies and Arctic Oscillation are especially remarkable.展开更多
Oceanographic surveying has been one of the key missions of the Chinese National Antarctic Research Expedition since 1984. Using the field data obtained in these surveys and the results from remote sensing and numeric...Oceanographic surveying has been one of the key missions of the Chinese National Antarctic Research Expedition since 1984. Using the field data obtained in these surveys and the results from remote sensing and numerical models, Chinese physical oceanographers have investigated the water masses, fronts and circulation patterns in the Southern Ocean. The results of nearly 30 years of research are summarized in this paper. Most oceanographic observations by Chinese researchers have been con- ducted in Prydz Bay and the adjacent seas. CTD （Conductivity Temperature and Depth） data, collected during the past 20 years, have been applied to study several features of the water masses in this region： The spatial variation of warm summer surface water, the northward extension of shelf water, the flow of ice shelf water from the cavity beneath the Amery Ice Shelf, the upweUing of the Circumpolar Deep Water, and the formation of the Antarctic Bottom Water. The circulation and its dynamic factors have been analyzed with dynamic heights calculated from CTD data as well as by numerical models. The structure and strength of the fronts in the southeast Indian Ocean and the Drake Passage were investigated with underway XBT/XCTD （Expendable Bathythermo- graph/Expendable CTD） and ADCP （Acoustic Doppler Current Profiler） data. Their interaunual variations have been determined and the factors of influence, especially the atmospheric forcing and mesoscale oceanic processes, were studied using remote sens- ing data. The dynamic mechanism of the Antarctic Circumpolar Current （ACC） was analyzed by theoretical models. The transport and pattern of the ACC have been well reproduced by coupled sea ice-ocean models. Additional details of ACC variability were identified based on satellite altimeter data. The response of the ACC to climate change was studied using reanalysis data. Prospects for future research are presented at the end of this paper.展开更多
Arctic sea ice concentration(SIC)prediction on a subseasonal scale plays an important role in polar navigation.To reduce the high uncertainty of daily forecasts,three time series prediction models are combined with em...Arctic sea ice concentration(SIC)prediction on a subseasonal scale plays an important role in polar navigation.To reduce the high uncertainty of daily forecasts,three time series prediction models are combined with empirical orthogonal function(EOF)decomposition to forecast Arctic pentad-mean SIC,where each month is divided into six pentad-means–the first five each span five days,and the last encompasses the remaining days,which may vary in length.The models were trained on SIC data from 1989 to2018 and tested from 2019 to 2023,with lead times ranging from 1 to 12 pentad-means.Model skill was evaluated based on SIC spatial patterns,sea ice area(SIA),and the sea ice edge in September from 2019 to 2023.The moving-averaged 2-m temperature helps reduce the long short-term memory model's error in the Beaufort and Chukchi Seas.Based on the models'scores for each EOF time series,weighted ensemble prediction results were obtained.These results outperform two benchmark models across all lead times.In addition,the ensemble prediction better reproduces the seasonal cycle of the SIA,with relative errors ranging from 1.04%to 3.85%.The predicted September ice edge closely matches observations,with binary accuracy consistently above 90%.Forecast models show the lowest errors in the central Arctic,while relatively higher errors appear in the Barents and Kara Seas.展开更多
Explosive cyclones(ECs) are rapidly intensifying subtropical cyclones that can develop within a short time and pose considerable threats to coastal areas in middle and high latitudes.Gaining a comprehensive understand...Explosive cyclones(ECs) are rapidly intensifying subtropical cyclones that can develop within a short time and pose considerable threats to coastal areas in middle and high latitudes.Gaining a comprehensive understanding of their formation,evolution,and mechanisms of explosive development is essential for improving forecasts of extreme weather events and mitigating associated impacts.Potential vorticity(PV),which is closely related to cyclone dynamics,serves as a valuable diagnostic tool in the study of ECs.In this study,two wintertime ECs of differing intensity over the Northwestern Pacific Ocean are analyzed to examine how different atmospheric processes influence PV generation and the rapid development of ECs.The maximum deepening rates of the two ECs are 2.81 Bergeron(called EC1) and 1.52 Bergeron(referred to as EC2).Results indicate that different stages of EC evolution are closely associated with PV tendency changes at different atmospheric levels.Using the PV tendency equation,during the explosive development of EC1,latent heat release may trigger the downward propagation of upper-level PV.For EC2,latent heat release notably enhances low-level PV,directly contributing to its rapid intensification.To validate these findings,sensitivity tests are conducted using the Weather Research and Forecasting model,with latent heat release turned off in the microphysical scheme for both cases.The results confirm the crucial role of latent heat release in generating low-level PV,further revealing that latent heat release contributes more to the explosive development of EC2 than that of EC1.展开更多
United Nations(UN)encourages sovereign states to take prompt and concrete measures to accomplish net-zero emissions by year 2050,requesting carbon dioxide removal(CDR)technologies to be prepared and implemented in suc...United Nations(UN)encourages sovereign states to take prompt and concrete measures to accomplish net-zero emissions by year 2050,requesting carbon dioxide removal(CDR)technologies to be prepared and implemented in such ambitious climate action roadmap.However,whether CDR technologies should be further promoted or discontinued post net-zero emission year remains unclear.In this Earth-system modelling research,we compare UN-suggested 2050 net-zero emission scenario against other common climate mitigation scenarios outlined by shared social-economic pathways(SSPs).We also simulate continued CDR implementations after net-zero emissions,which is hypothetically achieved in year 2050 and 2070 respectively,to investigate how CDR can impact the global climate throughout the whole 21st and 22nd centuries.The modelling results find if the 2050 UN net-zero emission goal is accomplished,the global average surface air temperature(SAT)in the end of 21st century is around 1.5℃higher compared to the pre-industrial level,promising an Earth environment more habitable than other scenarios without CDR.When CDR is applied to remove equal amount of anthropogenic CO_(2)emissions since industrial revolution,it restores the global average SAT close to pre-industrial level of 13.5℃.However,CDR-induced global carbon distribution within ocean,atmosphere,and land pools is different from the pre-industrial condition,causing reduced atmospheric CO_(2)concentration by 9 to 38 ppm compared to the pre-industrial cases,and more alkalinized ocean surface with pH increase of 0.004 to 0.024.This study affirms CDR cannot be viewed as a reversed process to anthropogenic CO_(2)emissions,accordingly climate policies to overcome the uncertainties after for late 21st century still require careful trade-offs for the decarbonation and the cost-benefits of CDR measures.展开更多
The subantarctic mode water(SAMW)represents a large water mass in the Southern Ocean.This body of water forms through deep convection(subduction)in winter and contributes to the uptake and storage of anthropogenic hea...The subantarctic mode water(SAMW)represents a large water mass in the Southern Ocean.This body of water forms through deep convection(subduction)in winter and contributes to the uptake and storage of anthropogenic heat.However,its longterm changes in subduction rate and volume in response to shifting climate conditions are unclear.In this study,we investigated the long-term trend of the subduction rate and volume of the South Pacific–SAMW(SPSAMW)using Simple Ocean Data Assimilation outputs during 1980–2017.The results show the overall increasing trend of the subduction rate of the SPSAMW.The increased subduction of the SPSAMW directly contributes to the volume variation in the SPSAMW.The increased subduction in the South Pacific reached(0.28±0.16)Sv-1 per year,which explains nearly 68%of the volume increase in the SPSAMW.This variability in the SPSAMW reflects alterations in the overlying atmosphere.The positive to negative phase change of the Interdecadal Pacific Oscillation(IPO)in 1980–2017 deepened the Amundsen Sea Low(ASL)via atmospheric teleconnections over the South Pacific.Further analysis reveals that the increased westerly winds during the deepening of ASL resulted in more cold water transport from the south,which deepened the winter mixed layer and thus increased subduction and volume within the SPSAMW subduction region.This finding suggests the association of the long-term trends of SPSAMW subduction and volume with the phase change of the IPO.展开更多
Predicting monsoon climate is one of the major endeavors in climate science and is becoming increasingly challenging due to global warming. The accuracy of monsoon seasonal predictions significantly impacts the lives ...Predicting monsoon climate is one of the major endeavors in climate science and is becoming increasingly challenging due to global warming. The accuracy of monsoon seasonal predictions significantly impacts the lives of billions who depend on or are affected by monsoons, as it is essential for the water cycle, food security, ecology, disaster prevention, and the economy of monsoon regions. Given the extensive literature on Asian monsoon climate prediction, we limit our focus to reviewing the seasonal prediction and predictability of the Asian Summer Monsoon (ASM). However, much of this review is also relevant to monsoon predictions in other seasons and regions. Over the past two decades, considerable progress has been made in the seasonal forecasting of the ASM, driven by an enhanced understanding of the sources of predictability and the dynamics of seasonal variability, along with advanced development in sophisticated models and technologies. This review centers on advances in understanding the physical foundation for monsoon climate prediction (section 2), significant findings and insights into the primary and regional sources of predictability arising from feedback processes among various climate components (sections 3 and 4), the effects of global warming and external forcings on predictability (section 5), developments in seasonal prediction models and techniques (section 6), the challenges and limitations of monsoon climate prediction (section 7), and emerging research trends with suggestions for future directions (section 8). We hope this review will stimulate creative activities to enhance monsoon climate prediction.展开更多
Severe hypoxia was observed in the submarine canyon to the east of the Changjiang estuary in July 14, 2015, two days after typhoon Chan-hom. The oxygen concentration reached as low as 2.0 mg/L and occupied a water col...Severe hypoxia was observed in the submarine canyon to the east of the Changjiang estuary in July 14, 2015, two days after typhoon Chan-hom. The oxygen concentration reached as low as 2.0 mg/L and occupied a water column of about 25 m. A ROMS model was con?gured to explore the underlying physical processes causing the formation of hypoxia. Chan-hom passed through the Changjiang estuary during the neap tide. The strati?cation was completely destroyed in the shallow nearshore region when typhoon passing. However, it was maintained in the deep canyon, though the surface mixed layer was largely deepened. The residual water in the deep canyon is considered to be the possible source of the later hypoxia. After Chan-hom departure, not only the low salinity plume water spread further of fshore, but also the sea surface temperature(SST) rewarmed quickly. Both changes helped strengthen the strati?cation and facilitate the formation of hypoxia. It was found that the surface heat ?ux, especially the solar short wave radiation dominated the surface re-warming, the of fshore advection of the warmer Changjiang Diluted Water(CDW) also played a role. In addition to the residual water in the deep canyon, the Taiwan Warm Current(TWC) was found to ?ow into the deep canyon pre-and soon post-Chan-hom, which was considered to be the original source of the hypoxia water.展开更多
In order to study the temporal variations of correlations between two time series,a running correlation coefficient(RCC)could be used.An RCC is calculated for a given time window,and the window is then moved sequentia...In order to study the temporal variations of correlations between two time series,a running correlation coefficient(RCC)could be used.An RCC is calculated for a given time window,and the window is then moved sequentially through time.The current calculation method for RCCs is based on the general definition of the Pearson product-moment correlation coefficient,calculated with the data within the time window,which we call the local running correlation coefficient(LRCC).The LRCC is calculated via the two anomalies corresponding to the two local means,meanwhile,the local means also vary.It is cleared up that the LRCC reflects only the correlation between the two anomalies within the time window but fails to exhibit the contributions of the two varying means.To address this problem,two unchanged means obtained from all available data are adopted to calculate an RCC,which is called the synthetic running correlation coefficient(SRCC).When the anomaly variations are dominant,the two RCCs are similar.However,when the variations of the means are dominant,the difference between the two RCCs becomes obvious.The SRCC reflects the correlations of both the anomaly variations and the variations of the means.Therefore,the SRCCs from different time points are intercomparable.A criterion for the superiority of the RCC algorithm is that the average value of the RCC should be close to the global correlation coefficient calculated using all data.The SRCC always meets this criterion,while the LRCC sometimes fails.Therefore,the SRCC is better than the LRCC for running correlations.We suggest using the SRCC to calculate the RCCs.展开更多
Massive green tides caused by Ulva prolifera in the Yellow Sea have occurred every summer since 2007 and have caused huge economic losses for local governments. The Subei （North liangsu Province, China） Shoal, with ...Massive green tides caused by Ulva prolifera in the Yellow Sea have occurred every summer since 2007 and have caused huge economic losses for local governments. The Subei （North liangsu Province, China） Shoal, with its large-scale Porphyra aquaculture, has been regarded as the most important source of U. prolifera for green tides. To reveal the physical mechanisms of floating and drifting algae in this area, the characteristics of the current, the temperature, the salinity and suspended particulate matter （SPM） in the southwestern Yellow Sea, especially in the Subei Shoal, were studied. The topography of the radial sand ridges in the Subei Shoal constrains the features of the currents and causes net longitudinal and latitudinal movements. The longitudinal net movement is a dominant dynamic factor that can bring U. prolifera into offshore waters. The amount of gas that is produced by algae during photosynthesis determines whether U. prolifera can float well on the sea surface after it is disposed into the water from Porphyra aquacultural apparatus. The Subei Shoal is characterized by a high turbidity, which can result in significant light attenuation and affect the photosynthesis together with the buoyancy of a U. prolifera in the water. According to satellite remote sensing data from 2012, the three-month-averaged surface SPM （April, May and June） in the Subei Shoal was 140 mg/dm^3, and the north of the Subei Shoal （the north of 34.5°N）, it was 11 mg/dm^3. According to the monthly averaged surface SPM in April, the transparency in the Subei Shoal was only 0.1 m, but it often exceeded 2.0 m outside of the Subei Shoal. The results explain why the floating ability of U. prolifera increases significantly once the green algae drifted outside the Subei Shoal.展开更多
This study investigates the migration and distribution of the warm-temperate fish Nibea albiflora. Their spawning migration and wintering migratory routes within in the Yellow Sea are described in detail. Considering ...This study investigates the migration and distribution of the warm-temperate fish Nibea albiflora. Their spawning migration and wintering migratory routes within in the Yellow Sea are described in detail. Considering the main physical features and environment of the Yellow Sea, it appears to be have one wintering ground and three migratory routes from the wintering ground to the spawning grounds. The fish begin to migrate from the wintering ground to the spawning grounds in the northwest region of the Yellow Sea in late March. The Yellow Sea has three spawning grounds. The first is located near the Yalu River on the Liaodong Peninsula and the second one is located in Rushan Bay of Shandong Peninsula. The third spawning ground is located in Haizhou Bay in the southern region of the Yellow Sea. This study found that the temperature of the Yellow Sea influences the migration of N. albiflora, and that the migratory routes coincide with the thermal fronts in the sea. Nutrients for juvenile fish are taken from the coastal upwelling area. Chlorophyll is a good environmental indicator of phytoplankton biomass and thereby provides the status of biological resources. Different types of sediment in near-shore zones are also of practical significance for the growth of fish. The study of the effects of marine environments on the migration of various fishes is not only significant to the fishing industry, but can also provide a scientific basis for the understanding of the ecological implications of the relevant physical processes.展开更多
In this study, the micro-and macro-physical properties, thermal structure and precipitation characteristics of cyclone eye walls and their surrounding spiral clouds were analysed with Cloud Sat and TRMM data for five ...In this study, the micro-and macro-physical properties, thermal structure and precipitation characteristics of cyclone eye walls and their surrounding spiral clouds were analysed with Cloud Sat and TRMM data for five tropical cyclones(TCs) in 2013. The results show that the ice-phase clouds of a mature TC are mainly above 5 km. With increasing altitude, the cloud droplet effective radius decreases, and the particle number concentration increases. Ice water content first increases and then decreases with increasing height. In the eye area, in addition to the well-known warm-core area, another warm core is also apparent around the eye at a height of 8 to 15 km. The horizontal distribution of precipitation is characterized by large-scale stratiform precipitation mixed with independent convective precipitation. The height of precipitation is mostly below 7.5 km, and the heavy rain is mainly below 5 km. When the peripheral convective clouds are strong enough, ice particles would be generated, thus providing conditions that are favourable for the formation of precipitation below.展开更多
The linkage between physical and biological processes is studied by applying a one-dimensional physical-biological coupled model to the Sargasso Sea. The physical model is the Princeton Ocean Model and the biological ...The linkage between physical and biological processes is studied by applying a one-dimensional physical-biological coupled model to the Sargasso Sea. The physical model is the Princeton Ocean Model and the biological model is a five-component system including phytoplankton, zooplankton, nitrate, ammonium, and detritus. The coupling between the physical and biological model is accomplished through vertical mixing which is parameterized by the level 2.5 Mellor and Yamada turbulence closure scheme. The coupled model investigates the annual cycle of ecosystem production and the response to external forcing, such as heat flux, wind stress, and surface salinity, and the relative importance of physical processes in affecting the ecosystem. Sensitivity experiments are also carried out, which provide information on how the model bio-chemical parameters affect the biological system. The computed seasonal cycles compare reasonably well with the observations of the Bermuda Atlantic Time-series Study(BATS). The spring bloom of phytoplankton occurs in March and April, right after the weakening of the winter mixing and before the establishment of the summer stratification. The bloom of zooplankton occurs about two weeks after the bloom of phytoplankton. The sensitivity experiments show that zooplankton is more sensitive to the variations of biochemical parameters than phytoplankton.展开更多
The linkage between physical and biological processes, particularly the effect of the circulation field on the distribution of phytoplankton, is studied by applying a two-dimensional model and an adjoint data assimila...The linkage between physical and biological processes, particularly the effect of the circulation field on the distribution of phytoplankton, is studied by applying a two-dimensional model and an adjoint data assimilation approach to the Gulf of Maine-Georges Bank region. The model results, comparing well with observation data, reveal seasonal and geographic variations of phytoplankton concentration and verify that the seasonal cycles of phytoplankton are controlled by both biological sources and advection processes which are functions of space and time and counterbalance each other. Although advective flux divergences have greater magnitudes on Georges Bank than in the coastal region of the western Gulf of Maine, advection control over phytoplankton concentration is more significant in the coastal region of the western Gulf of Maine. The model results also suggest that the two separated populations in the coastal regions of the western Gulf of Maine and on Georges Bank are self-sustaining.展开更多
This paper presents a study of physical and biogeochemical variables using numerical model and mixed layer oceanographic data from a 2 - 3 year?in situmeasurements in the Northwestern and Northeastern sites of the Atl...This paper presents a study of physical and biogeochemical variables using numerical model and mixed layer oceanographic data from a 2 - 3 year?in situmeasurements in the Northwestern and Northeastern sites of the Atlantic Ocean. Model outputs are presented and indicated that very good estimates may be obtained. The outputs showed considerable agreement in reproducing seasonal distributions of?pCO2,?pCO2-T,?pCO2-nonT, mixed layer temperature, and chlorophyll-a?in both winter and summer, and therefore provide useful physical and theoretical understanding of their biogeochemistry. The model?pCO2indicated a distinct temporal variability with seasonal changes coinciding with the change in sea surface temperature. It also provides an agreement that there is a strong seasonal cycle of mixed layer parameters filliped by nonthermal and physical factors. As an outgrowth of this work, the?pCO2?model outputs affirm the North Atlantic Ocean capacity as an important oceanographic sink for anthropogenic carbon dioxide.展开更多
Mesoscale eddies play a central role in the poleward oceanic heat flux in the Southern Ocean.Previous studies have documented changes in the location of temperature fronts in the Southern Ocean,but little attention ha...Mesoscale eddies play a central role in the poleward oceanic heat flux in the Southern Ocean.Previous studies have documented changes in the location of temperature fronts in the Southern Ocean,but little attention has been paid to changes in the genesis locations of mesoscale eddies.Here,we provide evidence from three decades of satellite altimetry observations for the heterogeneity of the poleward shift of mesoscale activities,with the largest trend of~0.23°±0.05°(10 yr)^(-1) over the Atlantic sector and a moderate trend of~0.1°±0.03°(10 yr)^(-1) over the Indian sector,but no significant trend in the Pacific sector.The poleward shift of mesoscale eddies is associated with a southward shift of the local westerly winds while being constrained by the major topographies.As the poleward shift of westerly winds is projected to persist,the poleward oceanic heat flux from mesoscale eddies may influence future ice melt.展开更多
Mesoscale air-sea interactions play a critical role in damping eddy activities.However,how mesoscale heat flux influences the distribution of eddy kinetic energy(EKE)in the wavenumber space remains unclear.In this stu...Mesoscale air-sea interactions play a critical role in damping eddy activities.However,how mesoscale heat flux influences the distribution of eddy kinetic energy(EKE)in the wavenumber space remains unclear.In this study,we investigate the EKE and temperature variance(T_(var))budgets in the Kuroshio Extension(KE)region using wavenumber spectral analysis based on 1/10°coupled climate simulations.These simulations include a standard high-resolution simulation and a smoothed simulation that overlooks mesoscale heat flux.By comparing the differences between these models,we confirm that air-sea heat exchange significantly dissipates Tvar.Neglecting mesoscale heat flux results in a 60% underestimation of the Tvar damping rate,which in turn increases energy transfer to EKE through the vertical buoyancy flux by 22%.This enhanced vertical buoyancy flux leads to a 20% higher EKE level and larger energy budget terms,particularly in the diffusion term,which is closely related to wind power.Furthermore,underestimating air-sea heat exchange could lead to an overestimation of the inverse kinetic energy cascade,thereby distorting the overall energy budget in the KE region.展开更多
The Antarctic Slope Current(ASC)links the processes occurring in the coast area with the global ocean by modulating the flow across the continental slope,which influences global overturning circulation and the mass ba...The Antarctic Slope Current(ASC)links the processes occurring in the coast area with the global ocean by modulating the flow across the continental slope,which influences global overturning circulation and the mass balance of the Antarctic ice shelves.This paper aims to explore the effects of wind and buoyancy fluxes on the long-term changes in the ASC using observation and reanalysis datasets.From 1993 to 2022,the ASC accelerated in all seasons,particularly in austral autumn,and was accompanied with the advancement of the strong flow.The positive buoyancy flux anomaly generates a low-density anomaly,which is accumulated by the prevailing surface easterly,maintaining a sharp density front along the continental slope.The heat flux intensifies the positive trend of buoyancy flux in summer and autumn,increasing the input of the lighter density anomaly into the ocean and advancing the strong flow of ASC.Compared with the annual mean,the additional acceleration of the ASC in autumn is mainly due to the contribution of the barotropic component,which could be explained by the local momentum input from the weakly enhanced local surface wind.The acceleration of the ASC is primarily driven by the positive trend of the buoyancy flux,while the influence of the wind on its seasonal variability becomes more significant due to the contribution of the local surface wind in autumn.展开更多
The characteristics of modified Circumpolar Deep Water(mCDW)on the continental shelf in Prydz Bay,East Antarctica,are studied based on hydrographic data obtained by the Chinese National Antarctic Research Expeditions ...The characteristics of modified Circumpolar Deep Water(mCDW)on the continental shelf in Prydz Bay,East Antarctica,are studied based on hydrographic data obtained by the Chinese National Antarctic Research Expeditions across 14 summers from 1999 to 2022.In austral summer,the mCDW upwells along the upper continental slope then intrudes on the continental shelf across the shelf break in a warm tongue that gradually upwells poleward.The mCDW intrusion at the 73°E section is relatively weaker in December and stronger in February while showing significant interannual variability.During strong intrusions(January 2000 and February 2003),the mCDW extends southward to 68°S and upwells to 50 m,whereas the mCDW only reaches the shelf break during weak intrusions(December 2004,January 2006,January 2011,and February 2015).The intensity of the mCDW intrusions correlates strongly with the accumulated wind stress curl(30 days prior)north of the shelf break(73.5°-78.0°E,64.5°-66.0°S).The summertime westerly winds play a key role in regulating the interannual variability of mCDW intrusion onto the continental shelf.A southward shift of the westerly winds promotes the upwelling and southward intrusion of mCDW across the shelf break.In addition,mCDW at 73°E can reach as far as 68°S due to the southward flow of mCDW being hindered by a northward outflowing branch of the coastal current at the Amery Ice Shelf(AIS)front.In austral summer,the mCDW had never been observed at the section along the AIS front;thus,it cannot directly contribute to the basal melting of the ice shelf.展开更多
Ocean mixing is a consequence of essential dynamic processes such as internal tides and lee waves that occur near the seafloor topography.Internal tides and lee waves are generated by barotropic tidal currents and geo...Ocean mixing is a consequence of essential dynamic processes such as internal tides and lee waves that occur near the seafloor topography.Internal tides and lee waves are generated by barotropic tidal currents and geostrophic flows,respectively.Ocean current is composed of multiple flows;thus,internal tides and lee waves occur concurrently in the real ocean.In this paper,the Massachusetts Institute of Technology general circulation model(MITgcm)is used to conduct 2D numerical experiments.By varying background flow intensities,the energy and dissipation relationship between internal tides and lee waves are investigated.The results reveal that the internal tide beams become asymmetric due to the influence of Doppler shift.The lee wave structure gradually leads the wave field when the background flow velocity rises constantly.The presence of a background flow increases the energy portion of the high-mode wave by up to 15%-20%.Moreover,strong shear,owing to the background flow,considerably increases dissipation.When the background flow velocity is higher than the barotropic tidal current velocity,the isopycnal overturn triggered by the lee wave generates a dissipation of the same order of magnitude as the shear.展开更多
基金supported by the National Department Public Benefit Research Foundation (Grant no.201105022)the National Natural Science Foundation of China(Grant nos. 40876006, 40976111)
文摘As a part of the National Report of China for the International Association for Physical Science of Ocean （IAPSO）, the main research results of Chinese scientists in Arctic physical oceanography during 2007-2010 are reviewed in this paper. This period overlaps with the International Polar Year （IPY）, which is a catalyst for nations to emphasize activities and research in the polar regions. The Arctic also experienced a rapid change in sea ice, ocean, and climate during this time. China launched two Arctic cruises with the R/V XUE LONG icebreaker, in 2008 and 2010, which provided more opportunities for Chinese scientists to investigate the Arctic Ocean and its change. During this period, Chinese scientists participated in more than ten other cruises with international collaborations. The main research covered in this paper includes the upper ocean characteristic, ocean and sea ice optics, kinematics of sea ice and the Arctic impact on global climate change. The progress in sea ice optics, the observation technologies and Arctic Oscillation are especially remarkable.
基金supported by the Chinese Polar Environment Comprehensive Investigation and Assessment Programmes (Grant nos.CHINARE2013-04-01,CHINARE2013-04-04)the National High-tech Research & Development Program of China (Grant no.2010CB950301)
文摘Oceanographic surveying has been one of the key missions of the Chinese National Antarctic Research Expedition since 1984. Using the field data obtained in these surveys and the results from remote sensing and numerical models, Chinese physical oceanographers have investigated the water masses, fronts and circulation patterns in the Southern Ocean. The results of nearly 30 years of research are summarized in this paper. Most oceanographic observations by Chinese researchers have been con- ducted in Prydz Bay and the adjacent seas. CTD （Conductivity Temperature and Depth） data, collected during the past 20 years, have been applied to study several features of the water masses in this region： The spatial variation of warm summer surface water, the northward extension of shelf water, the flow of ice shelf water from the cavity beneath the Amery Ice Shelf, the upweUing of the Circumpolar Deep Water, and the formation of the Antarctic Bottom Water. The circulation and its dynamic factors have been analyzed with dynamic heights calculated from CTD data as well as by numerical models. The structure and strength of the fronts in the southeast Indian Ocean and the Drake Passage were investigated with underway XBT/XCTD （Expendable Bathythermo- graph/Expendable CTD） and ADCP （Acoustic Doppler Current Profiler） data. Their interaunual variations have been determined and the factors of influence, especially the atmospheric forcing and mesoscale oceanic processes, were studied using remote sens- ing data. The dynamic mechanism of the Antarctic Circumpolar Current （ACC） was analyzed by theoretical models. The transport and pattern of the ACC have been well reproduced by coupled sea ice-ocean models. Additional details of ACC variability were identified based on satellite altimeter data. The response of the ACC to climate change was studied using reanalysis data. Prospects for future research are presented at the end of this paper.
基金supported by the National Key Research and Development Program(No.2023YFC2809101)the Laoshan Laboratory Technology Innovation Project(No.LSKJ202202301)。
文摘Arctic sea ice concentration(SIC)prediction on a subseasonal scale plays an important role in polar navigation.To reduce the high uncertainty of daily forecasts,three time series prediction models are combined with empirical orthogonal function(EOF)decomposition to forecast Arctic pentad-mean SIC,where each month is divided into six pentad-means–the first five each span five days,and the last encompasses the remaining days,which may vary in length.The models were trained on SIC data from 1989 to2018 and tested from 2019 to 2023,with lead times ranging from 1 to 12 pentad-means.Model skill was evaluated based on SIC spatial patterns,sea ice area(SIA),and the sea ice edge in September from 2019 to 2023.The moving-averaged 2-m temperature helps reduce the long short-term memory model's error in the Beaufort and Chukchi Seas.Based on the models'scores for each EOF time series,weighted ensemble prediction results were obtained.These results outperform two benchmark models across all lead times.In addition,the ensemble prediction better reproduces the seasonal cycle of the SIA,with relative errors ranging from 1.04%to 3.85%.The predicted September ice edge closely matches observations,with binary accuracy consistently above 90%.Forecast models show the lowest errors in the central Arctic,while relatively higher errors appear in the Barents and Kara Seas.
基金financially supported by the National Key R&D Program of China (No. 2022YFC3004204)the National Natural Science Foundation of China (No. 42275001)the Natural Science Foundation of Shandong Province (No. ZR2022MD038)。
文摘Explosive cyclones(ECs) are rapidly intensifying subtropical cyclones that can develop within a short time and pose considerable threats to coastal areas in middle and high latitudes.Gaining a comprehensive understanding of their formation,evolution,and mechanisms of explosive development is essential for improving forecasts of extreme weather events and mitigating associated impacts.Potential vorticity(PV),which is closely related to cyclone dynamics,serves as a valuable diagnostic tool in the study of ECs.In this study,two wintertime ECs of differing intensity over the Northwestern Pacific Ocean are analyzed to examine how different atmospheric processes influence PV generation and the rapid development of ECs.The maximum deepening rates of the two ECs are 2.81 Bergeron(called EC1) and 1.52 Bergeron(referred to as EC2).Results indicate that different stages of EC evolution are closely associated with PV tendency changes at different atmospheric levels.Using the PV tendency equation,during the explosive development of EC1,latent heat release may trigger the downward propagation of upper-level PV.For EC2,latent heat release notably enhances low-level PV,directly contributing to its rapid intensification.To validate these findings,sensitivity tests are conducted using the Weather Research and Forecasting model,with latent heat release turned off in the microphysical scheme for both cases.The results confirm the crucial role of latent heat release in generating low-level PV,further revealing that latent heat release contributes more to the explosive development of EC2 than that of EC1.
基金supported by the Fundamental Research Funds for the Central Universities(No.202242001)the Mount Tai Research Grant。
文摘United Nations(UN)encourages sovereign states to take prompt and concrete measures to accomplish net-zero emissions by year 2050,requesting carbon dioxide removal(CDR)technologies to be prepared and implemented in such ambitious climate action roadmap.However,whether CDR technologies should be further promoted or discontinued post net-zero emission year remains unclear.In this Earth-system modelling research,we compare UN-suggested 2050 net-zero emission scenario against other common climate mitigation scenarios outlined by shared social-economic pathways(SSPs).We also simulate continued CDR implementations after net-zero emissions,which is hypothetically achieved in year 2050 and 2070 respectively,to investigate how CDR can impact the global climate throughout the whole 21st and 22nd centuries.The modelling results find if the 2050 UN net-zero emission goal is accomplished,the global average surface air temperature(SAT)in the end of 21st century is around 1.5℃higher compared to the pre-industrial level,promising an Earth environment more habitable than other scenarios without CDR.When CDR is applied to remove equal amount of anthropogenic CO_(2)emissions since industrial revolution,it restores the global average SAT close to pre-industrial level of 13.5℃.However,CDR-induced global carbon distribution within ocean,atmosphere,and land pools is different from the pre-industrial condition,causing reduced atmospheric CO_(2)concentration by 9 to 38 ppm compared to the pre-industrial cases,and more alkalinized ocean surface with pH increase of 0.004 to 0.024.This study affirms CDR cannot be viewed as a reversed process to anthropogenic CO_(2)emissions,accordingly climate policies to overcome the uncertainties after for late 21st century still require careful trade-offs for the decarbonation and the cost-benefits of CDR measures.
基金supported by the National Natural Science Foundation of China(Nos.42406256,42376034,and 42430402)the Qingdao Postdoctoral Application Research Project(No.QDBSH20220202152)+1 种基金the National Key R&D Program of China(No.2018YFA0605701)the Chinese Arctic and Antarctic Administration(No.IRASCC2020-2022-02-01-03)。
文摘The subantarctic mode water(SAMW)represents a large water mass in the Southern Ocean.This body of water forms through deep convection(subduction)in winter and contributes to the uptake and storage of anthropogenic heat.However,its longterm changes in subduction rate and volume in response to shifting climate conditions are unclear.In this study,we investigated the long-term trend of the subduction rate and volume of the South Pacific–SAMW(SPSAMW)using Simple Ocean Data Assimilation outputs during 1980–2017.The results show the overall increasing trend of the subduction rate of the SPSAMW.The increased subduction of the SPSAMW directly contributes to the volume variation in the SPSAMW.The increased subduction in the South Pacific reached(0.28±0.16)Sv-1 per year,which explains nearly 68%of the volume increase in the SPSAMW.This variability in the SPSAMW reflects alterations in the overlying atmosphere.The positive to negative phase change of the Interdecadal Pacific Oscillation(IPO)in 1980–2017 deepened the Amundsen Sea Low(ASL)via atmospheric teleconnections over the South Pacific.Further analysis reveals that the increased westerly winds during the deepening of ASL resulted in more cold water transport from the south,which deepened the winter mixed layer and thus increased subduction and volume within the SPSAMW subduction region.This finding suggests the association of the long-term trends of SPSAMW subduction and volume with the phase change of the IPO.
基金supported by the National Natural Science Foundation of China(Grant No.U2342208)support from NSF/Climate Dynamics Award#2025057。
文摘Predicting monsoon climate is one of the major endeavors in climate science and is becoming increasingly challenging due to global warming. The accuracy of monsoon seasonal predictions significantly impacts the lives of billions who depend on or are affected by monsoons, as it is essential for the water cycle, food security, ecology, disaster prevention, and the economy of monsoon regions. Given the extensive literature on Asian monsoon climate prediction, we limit our focus to reviewing the seasonal prediction and predictability of the Asian Summer Monsoon (ASM). However, much of this review is also relevant to monsoon predictions in other seasons and regions. Over the past two decades, considerable progress has been made in the seasonal forecasting of the ASM, driven by an enhanced understanding of the sources of predictability and the dynamics of seasonal variability, along with advanced development in sophisticated models and technologies. This review centers on advances in understanding the physical foundation for monsoon climate prediction (section 2), significant findings and insights into the primary and regional sources of predictability arising from feedback processes among various climate components (sections 3 and 4), the effects of global warming and external forcings on predictability (section 5), developments in seasonal prediction models and techniques (section 6), the challenges and limitations of monsoon climate prediction (section 7), and emerging research trends with suggestions for future directions (section 8). We hope this review will stimulate creative activities to enhance monsoon climate prediction.
基金Supported by the National Key Research and Development Program of China(No.2016YFC1402000)the National Natural Science Foundation of China(Nos.41406008,41706022)+2 种基金the Fundamental Research Funds for the Central Universities(No.201762032)the Natural Science Foundation of Shandong Province(No.ZR2014DQ023)the SRF for ROCS,SEM[2014] No.1685
文摘Severe hypoxia was observed in the submarine canyon to the east of the Changjiang estuary in July 14, 2015, two days after typhoon Chan-hom. The oxygen concentration reached as low as 2.0 mg/L and occupied a water column of about 25 m. A ROMS model was con?gured to explore the underlying physical processes causing the formation of hypoxia. Chan-hom passed through the Changjiang estuary during the neap tide. The strati?cation was completely destroyed in the shallow nearshore region when typhoon passing. However, it was maintained in the deep canyon, though the surface mixed layer was largely deepened. The residual water in the deep canyon is considered to be the possible source of the later hypoxia. After Chan-hom departure, not only the low salinity plume water spread further of fshore, but also the sea surface temperature(SST) rewarmed quickly. Both changes helped strengthen the strati?cation and facilitate the formation of hypoxia. It was found that the surface heat ?ux, especially the solar short wave radiation dominated the surface re-warming, the of fshore advection of the warmer Changjiang Diluted Water(CDW) also played a role. In addition to the residual water in the deep canyon, the Taiwan Warm Current(TWC) was found to ?ow into the deep canyon pre-and soon post-Chan-hom, which was considered to be the original source of the hypoxia water.
基金supported by the Key Program of the National Natural Science Foundation of China (No. 41330960)the Global Change Research Program of China (No. 2015CB953900)
文摘In order to study the temporal variations of correlations between two time series,a running correlation coefficient(RCC)could be used.An RCC is calculated for a given time window,and the window is then moved sequentially through time.The current calculation method for RCCs is based on the general definition of the Pearson product-moment correlation coefficient,calculated with the data within the time window,which we call the local running correlation coefficient(LRCC).The LRCC is calculated via the two anomalies corresponding to the two local means,meanwhile,the local means also vary.It is cleared up that the LRCC reflects only the correlation between the two anomalies within the time window but fails to exhibit the contributions of the two varying means.To address this problem,two unchanged means obtained from all available data are adopted to calculate an RCC,which is called the synthetic running correlation coefficient(SRCC).When the anomaly variations are dominant,the two RCCs are similar.However,when the variations of the means are dominant,the difference between the two RCCs becomes obvious.The SRCC reflects the correlations of both the anomaly variations and the variations of the means.Therefore,the SRCCs from different time points are intercomparable.A criterion for the superiority of the RCC algorithm is that the average value of the RCC should be close to the global correlation coefficient calculated using all data.The SRCC always meets this criterion,while the LRCC sometimes fails.Therefore,the SRCC is better than the LRCC for running correlations.We suggest using the SRCC to calculate the RCCs.
基金The National Basic Research Program of China under contract No.2010CB428704the Strategic Priority Research Program of the Chinese Academy of Sciences under contract No.XDA11020304+1 种基金the National Natural Science Foundation of China under contract No.41276083the Scientific Research Fund of the Second Institute of Oceanography of the State Oceanic Administration of China under contract No.JG1415
文摘Massive green tides caused by Ulva prolifera in the Yellow Sea have occurred every summer since 2007 and have caused huge economic losses for local governments. The Subei （North liangsu Province, China） Shoal, with its large-scale Porphyra aquaculture, has been regarded as the most important source of U. prolifera for green tides. To reveal the physical mechanisms of floating and drifting algae in this area, the characteristics of the current, the temperature, the salinity and suspended particulate matter （SPM） in the southwestern Yellow Sea, especially in the Subei Shoal, were studied. The topography of the radial sand ridges in the Subei Shoal constrains the features of the currents and causes net longitudinal and latitudinal movements. The longitudinal net movement is a dominant dynamic factor that can bring U. prolifera into offshore waters. The amount of gas that is produced by algae during photosynthesis determines whether U. prolifera can float well on the sea surface after it is disposed into the water from Porphyra aquacultural apparatus. The Subei Shoal is characterized by a high turbidity, which can result in significant light attenuation and affect the photosynthesis together with the buoyancy of a U. prolifera in the water. According to satellite remote sensing data from 2012, the three-month-averaged surface SPM （April, May and June） in the Subei Shoal was 140 mg/dm^3, and the north of the Subei Shoal （the north of 34.5°N）, it was 11 mg/dm^3. According to the monthly averaged surface SPM in April, the transparency in the Subei Shoal was only 0.1 m, but it often exceeded 2.0 m outside of the Subei Shoal. The results explain why the floating ability of U. prolifera increases significantly once the green algae drifted outside the Subei Shoal.
基金supported by the Ocean Public Welfare Scientific Research Project (No. 201405029-4)
文摘This study investigates the migration and distribution of the warm-temperate fish Nibea albiflora. Their spawning migration and wintering migratory routes within in the Yellow Sea are described in detail. Considering the main physical features and environment of the Yellow Sea, it appears to be have one wintering ground and three migratory routes from the wintering ground to the spawning grounds. The fish begin to migrate from the wintering ground to the spawning grounds in the northwest region of the Yellow Sea in late March. The Yellow Sea has three spawning grounds. The first is located near the Yalu River on the Liaodong Peninsula and the second one is located in Rushan Bay of Shandong Peninsula. The third spawning ground is located in Haizhou Bay in the southern region of the Yellow Sea. This study found that the temperature of the Yellow Sea influences the migration of N. albiflora, and that the migratory routes coincide with the thermal fronts in the sea. Nutrients for juvenile fish are taken from the coastal upwelling area. Chlorophyll is a good environmental indicator of phytoplankton biomass and thereby provides the status of biological resources. Different types of sediment in near-shore zones are also of practical significance for the growth of fish. The study of the effects of marine environments on the migration of various fishes is not only significant to the fishing industry, but can also provide a scientific basis for the understanding of the ecological implications of the relevant physical processes.
基金Young Scientists Fund of National Natural Science Foundation of China Grant(41505013,41575017)Natural Science Foundation of Shandong Province(BS2015HZ019)
文摘In this study, the micro-and macro-physical properties, thermal structure and precipitation characteristics of cyclone eye walls and their surrounding spiral clouds were analysed with Cloud Sat and TRMM data for five tropical cyclones(TCs) in 2013. The results show that the ice-phase clouds of a mature TC are mainly above 5 km. With increasing altitude, the cloud droplet effective radius decreases, and the particle number concentration increases. Ice water content first increases and then decreases with increasing height. In the eye area, in addition to the well-known warm-core area, another warm core is also apparent around the eye at a height of 8 to 15 km. The horizontal distribution of precipitation is characterized by large-scale stratiform precipitation mixed with independent convective precipitation. The height of precipitation is mostly below 7.5 km, and the heavy rain is mainly below 5 km. When the peripheral convective clouds are strong enough, ice particles would be generated, thus providing conditions that are favourable for the formation of precipitation below.
基金supported by the Shandong Young Scientists Research Awards under grant BS2011HZ021
文摘The linkage between physical and biological processes is studied by applying a one-dimensional physical-biological coupled model to the Sargasso Sea. The physical model is the Princeton Ocean Model and the biological model is a five-component system including phytoplankton, zooplankton, nitrate, ammonium, and detritus. The coupling between the physical and biological model is accomplished through vertical mixing which is parameterized by the level 2.5 Mellor and Yamada turbulence closure scheme. The coupled model investigates the annual cycle of ecosystem production and the response to external forcing, such as heat flux, wind stress, and surface salinity, and the relative importance of physical processes in affecting the ecosystem. Sensitivity experiments are also carried out, which provide information on how the model bio-chemical parameters affect the biological system. The computed seasonal cycles compare reasonably well with the observations of the Bermuda Atlantic Time-series Study(BATS). The spring bloom of phytoplankton occurs in March and April, right after the weakening of the winter mixing and before the establishment of the summer stratification. The bloom of zooplankton occurs about two weeks after the bloom of phytoplankton. The sensitivity experiments show that zooplankton is more sensitive to the variations of biochemical parameters than phytoplankton.
基金supported by the Shangdong Province Young and Middle-Aged Scientists Research Awards under Grant BS2011HZ021
文摘The linkage between physical and biological processes, particularly the effect of the circulation field on the distribution of phytoplankton, is studied by applying a two-dimensional model and an adjoint data assimilation approach to the Gulf of Maine-Georges Bank region. The model results, comparing well with observation data, reveal seasonal and geographic variations of phytoplankton concentration and verify that the seasonal cycles of phytoplankton are controlled by both biological sources and advection processes which are functions of space and time and counterbalance each other. Although advective flux divergences have greater magnitudes on Georges Bank than in the coastal region of the western Gulf of Maine, advection control over phytoplankton concentration is more significant in the coastal region of the western Gulf of Maine. The model results also suggest that the two separated populations in the coastal regions of the western Gulf of Maine and on Georges Bank are self-sustaining.
文摘This paper presents a study of physical and biogeochemical variables using numerical model and mixed layer oceanographic data from a 2 - 3 year?in situmeasurements in the Northwestern and Northeastern sites of the Atlantic Ocean. Model outputs are presented and indicated that very good estimates may be obtained. The outputs showed considerable agreement in reproducing seasonal distributions of?pCO2,?pCO2-T,?pCO2-nonT, mixed layer temperature, and chlorophyll-a?in both winter and summer, and therefore provide useful physical and theoretical understanding of their biogeochemistry. The model?pCO2indicated a distinct temporal variability with seasonal changes coinciding with the change in sea surface temperature. It also provides an agreement that there is a strong seasonal cycle of mixed layer parameters filliped by nonthermal and physical factors. As an outgrowth of this work, the?pCO2?model outputs affirm the North Atlantic Ocean capacity as an important oceanographic sink for anthropogenic carbon dioxide.
基金supported by the National Natural Science Foundation of China(Grant Nos.42230405,42006029)Science and Technology Plan of Liaoning Province(2024JH2/102400061)+1 种基金Dalian Science and Technology Innovation Fund(2024JJ11PT007)Dalian Science and Technology Pro-gram for Innovation Talents of Dalian(2022RJ06).
文摘Mesoscale eddies play a central role in the poleward oceanic heat flux in the Southern Ocean.Previous studies have documented changes in the location of temperature fronts in the Southern Ocean,but little attention has been paid to changes in the genesis locations of mesoscale eddies.Here,we provide evidence from three decades of satellite altimetry observations for the heterogeneity of the poleward shift of mesoscale activities,with the largest trend of~0.23°±0.05°(10 yr)^(-1) over the Atlantic sector and a moderate trend of~0.1°±0.03°(10 yr)^(-1) over the Indian sector,but no significant trend in the Pacific sector.The poleward shift of mesoscale eddies is associated with a southward shift of the local westerly winds while being constrained by the major topographies.As the poleward shift of westerly winds is projected to persist,the poleward oceanic heat flux from mesoscale eddies may influence future ice melt.
基金supported by the Natu-ral Science Foundation of China and Fundamental Research Funds for the Central Universities(Grant Nos.42176006,42422601,202241006 to H.Y.)the Natural Science Foundation of China(Grant No.42225601 to Z.C.).
文摘Mesoscale air-sea interactions play a critical role in damping eddy activities.However,how mesoscale heat flux influences the distribution of eddy kinetic energy(EKE)in the wavenumber space remains unclear.In this study,we investigate the EKE and temperature variance(T_(var))budgets in the Kuroshio Extension(KE)region using wavenumber spectral analysis based on 1/10°coupled climate simulations.These simulations include a standard high-resolution simulation and a smoothed simulation that overlooks mesoscale heat flux.By comparing the differences between these models,we confirm that air-sea heat exchange significantly dissipates Tvar.Neglecting mesoscale heat flux results in a 60% underestimation of the Tvar damping rate,which in turn increases energy transfer to EKE through the vertical buoyancy flux by 22%.This enhanced vertical buoyancy flux leads to a 20% higher EKE level and larger energy budget terms,particularly in the diffusion term,which is closely related to wind power.Furthermore,underestimating air-sea heat exchange could lead to an overestimation of the inverse kinetic energy cascade,thereby distorting the overall energy budget in the KE region.
基金The National Natural Science Foundation of China under contract Nos 42376256,42230405,and 41576020.
文摘The Antarctic Slope Current(ASC)links the processes occurring in the coast area with the global ocean by modulating the flow across the continental slope,which influences global overturning circulation and the mass balance of the Antarctic ice shelves.This paper aims to explore the effects of wind and buoyancy fluxes on the long-term changes in the ASC using observation and reanalysis datasets.From 1993 to 2022,the ASC accelerated in all seasons,particularly in austral autumn,and was accompanied with the advancement of the strong flow.The positive buoyancy flux anomaly generates a low-density anomaly,which is accumulated by the prevailing surface easterly,maintaining a sharp density front along the continental slope.The heat flux intensifies the positive trend of buoyancy flux in summer and autumn,increasing the input of the lighter density anomaly into the ocean and advancing the strong flow of ASC.Compared with the annual mean,the additional acceleration of the ASC in autumn is mainly due to the contribution of the barotropic component,which could be explained by the local momentum input from the weakly enhanced local surface wind.The acceleration of the ASC is primarily driven by the positive trend of the buoyancy flux,while the influence of the wind on its seasonal variability becomes more significant due to the contribution of the local surface wind in autumn.
基金supported by the National Natural Science Foundation of China(No.41976217)the National Key R&D Program of China(No.2018YFA0605701).
文摘The characteristics of modified Circumpolar Deep Water(mCDW)on the continental shelf in Prydz Bay,East Antarctica,are studied based on hydrographic data obtained by the Chinese National Antarctic Research Expeditions across 14 summers from 1999 to 2022.In austral summer,the mCDW upwells along the upper continental slope then intrudes on the continental shelf across the shelf break in a warm tongue that gradually upwells poleward.The mCDW intrusion at the 73°E section is relatively weaker in December and stronger in February while showing significant interannual variability.During strong intrusions(January 2000 and February 2003),the mCDW extends southward to 68°S and upwells to 50 m,whereas the mCDW only reaches the shelf break during weak intrusions(December 2004,January 2006,January 2011,and February 2015).The intensity of the mCDW intrusions correlates strongly with the accumulated wind stress curl(30 days prior)north of the shelf break(73.5°-78.0°E,64.5°-66.0°S).The summertime westerly winds play a key role in regulating the interannual variability of mCDW intrusion onto the continental shelf.A southward shift of the westerly winds promotes the upwelling and southward intrusion of mCDW across the shelf break.In addition,mCDW at 73°E can reach as far as 68°S due to the southward flow of mCDW being hindered by a northward outflowing branch of the coastal current at the Amery Ice Shelf(AIS)front.In austral summer,the mCDW had never been observed at the section along the AIS front;thus,it cannot directly contribute to the basal melting of the ice shelf.
基金supported by the National Natural Science Foundation of China(No.41876015)。
文摘Ocean mixing is a consequence of essential dynamic processes such as internal tides and lee waves that occur near the seafloor topography.Internal tides and lee waves are generated by barotropic tidal currents and geostrophic flows,respectively.Ocean current is composed of multiple flows;thus,internal tides and lee waves occur concurrently in the real ocean.In this paper,the Massachusetts Institute of Technology general circulation model(MITgcm)is used to conduct 2D numerical experiments.By varying background flow intensities,the energy and dissipation relationship between internal tides and lee waves are investigated.The results reveal that the internal tide beams become asymmetric due to the influence of Doppler shift.The lee wave structure gradually leads the wave field when the background flow velocity rises constantly.The presence of a background flow increases the energy portion of the high-mode wave by up to 15%-20%.Moreover,strong shear,owing to the background flow,considerably increases dissipation.When the background flow velocity is higher than the barotropic tidal current velocity,the isopycnal overturn triggered by the lee wave generates a dissipation of the same order of magnitude as the shear.
