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
The Antarctic Bottom Water formation site Vincennes Bay,East Antarctica is experiencing a substantial intrusion of modified Circumpolar Deep Water(mCDW),which may inhibit the formation of Dense Shelf Water(DSW)and dri...The Antarctic Bottom Water formation site Vincennes Bay,East Antarctica is experiencing a substantial intrusion of modified Circumpolar Deep Water(mCDW),which may inhibit the formation of Dense Shelf Water(DSW)and drive basal melting of the ice shelves.Based on hydrographic data obtained from March to November in 2012,we evaluated the spatial spread of mCDW over the continental shelf region of Vincennes Bay and the associated temporal evolution of water properties,as well as the sea ice formation effect on water column in the coastal polynya.Results show that two branches of mCDW occupied the deep layers of the continental shelf,distinguished by the potential density(smaller than 27.8 kg/m^(3) or not)when potential temperatureθ=0.5°C in theθ-salinity space.The warmer and less dense branch observed on the east plateau,accessed the eastern ice shelves in the coastal polynya to drive basal melting of ice shelves.In contrast,the other colder and denser branch in the mid-depression reached the western Underwood Ice Shelf.DSW formation was detectable in the coastal polynya during September-November,proving the occurrence of deep convection.Surface heat loss and brine rejection during the intensive sea ice formation contributed to the destratification of the water column in the coastal polynya.It was estimated that at least 1.11±0.79 TW heat carried by mCDW into the inner part of the polynya.展开更多
An obvious trend shift in the annual mean and winter mixed layer depth(MLD)in the Antarctic Circumpolar Current(ACC)region was detected during the 1960–2021 period.Shallowing trends stopped in mid-1980s,followed by a...An obvious trend shift in the annual mean and winter mixed layer depth(MLD)in the Antarctic Circumpolar Current(ACC)region was detected during the 1960–2021 period.Shallowing trends stopped in mid-1980s,followed by a period of weak trends.The MLD deepening trend difference between the two periods were mainly distributed in the western areas in the Drake Passage,the areas north to Victoria Land and Wilkes Land,and the central parts of the South Indian sector.The newly formed ocean current shear due to the meridional shift of the ACC flow axis between the two periods is the dominant driver for the MLD trends shift distributed in the western areas in the Drake Passage and the central parts of the South Indian sector.The saltier trends in the regions north to Victoria Land and Wilkes Land could be responsible for the strengthening mixing processes in this region.展开更多
The low-frequency variance of the surface wave in the area of the Antarctic Circumpolar Current （ACC） and its correlation with the antarctic circumpolar wave （ACW） are focused on. The analysis of the series of 44 ...The low-frequency variance of the surface wave in the area of the Antarctic Circumpolar Current （ACC） and its correlation with the antarctic circumpolar wave （ACW） are focused on. The analysis of the series of 44 a significant wave height （SWH） interannual anomalies reveals that the SWH anomalies have a strong periodicity of about 4-5 a and this signal propagates eastward obviously from 1985 to 1995, which needs about 8 a to complete a mimacircle around the earth. The method of empirical orthogonal function （EOF） is used to analyze the filtered monthly SWH anomalies to study the spatio-temporal distributions and the propagation characteristics of the low-frequency signals in the wave field. Both the dominant wavenumber- 2 pattern in space and the propagation feature in the south Pacific, the south Atlantic and the south Indian ocean show strong consistency with the ACW. So it is reasonable to conclude that the ACW signal also exists in the wave field. The ACW is important for the climate in the Southern Ocean, so it is worth to pay more attention to the large- scale effect of the surface wave, which may also be important for climate studies.展开更多
Based on the data and method offered by Liu et al. （2009）, the direct wind and Stokes drift-induced energy inputs into the Ekman layer within the Antarctic Circumpolar Current （ACC） area are reestimated since the ...Based on the data and method offered by Liu et al. （2009）, the direct wind and Stokes drift-induced energy inputs into the Ekman layer within the Antarctic Circumpolar Current （ACC） area are reestimated since the results of the former have been proved to be underestimated. And the result shows that the total rate of energy input into the Ekman-Stokes layer within the ACC area is 852.41 GW, including 649.75 GW of direct wind energy input （76%） and 202.66 GW of Stoke drift-induced energy input （24%）. Total increased energy input, due to wave-induced Coriolis-Stokes forcing added to the classical Ekman model, is 52.05 GW, accounting for 6.5% of the wind energy input into the classical Ekman layer. The long-term variability of direct wind and Stokes drift-induced energy inputs into the Ekman layer within the ACC is also investigated, and the result shows that the Stokes drift hinders the decadal increasing trend of direct wind energy input. Meanwhile, there is a period of 4-5 a in the energy spectrums, as same as the Antarctic circumpolar wave.展开更多
Fronts, baroclinic transport, and mesoscale variability of the Antarctic Circumpolar Current （ACC） along 115°E are examined on the basis of CTD data from two hydrographic cruises occupied in 1995 as a part of t...Fronts, baroclinic transport, and mesoscale variability of the Antarctic Circumpolar Current （ACC） along 115°E are examined on the basis of CTD data from two hydrographic cruises occupied in 1995 as a part of the World Ocean Circulation Experiment （WOCE cruise I9S） and in 2004 as a part of CLIVAR/CO2 repeat hydrography program. The integrated baroclinic transport across I9S section is （97.2×106±2.2×106） m3/s relative to the deepest common level （DCL）. The net transport at the north end of I9S, determined by the south Australian circulation system, is about 16.5× 106 m3/s westward. Relying on a consistent set of water mass criteria and transport maxima, the ACC baroclinic transport, （117×106±6.7×106） m3/s to the east, is carried along three fronts： the Subantarctic Front （SAF） at a mean latitude of 44°-49°S carries （50.6×106=t=13.4×106） m3/s; the Polar Front （PF）, with the northern branch （PF-N） at 50.5°S and the southern branch （PF- S） at 58°S, carries （51.3×106±8.7×106） m3/s; finally, the southern ACC front （SACCF） and the southern boundary of the ACC （SB） consist of three cores between 59°S and 65°S that combined carry （15.2× 106±1.8× 106） m3/s. Mesoscale eddy features are identifiable in the CTD sections and tracked in concurrent maps of altimetric sea level anomalies （SLA） between 44°-48°S and 53°-57°S. Because of the remarkable mesoseale eddy features within the SAF observed in both the tracks of the cruises, the eastward transport of the SAF occurs at two latitude bands separating by 1°. Both the CTD and the altimetric data suggest that the mesoscale variability is concentrated around the Antarctic Polar Frontal Zone （APFZ） and causes the ACC fronts to merge, diverge, and to fluctuate in intensity and position along their paths.展开更多
Based on a linear quasi-geostrophic vorticity equation, we have set up an analytical diagnostic mode for the Antarctic Circumpolar Current. The results show that the balance among wind stress,ocean horizontal viscous ...Based on a linear quasi-geostrophic vorticity equation, we have set up an analytical diagnostic mode for the Antarctic Circumpolar Current. The results show that the balance among wind stress,ocean horizontal viscous stress and the β-effect is the basic balance of the Antarctic Circumpolar Current, and the center velocity of the jet, coming from the Drake Passage,will decrease due to the ocean dynamic adjustment, and the width in the north-south direction will decreasegradually. The jet coming from the Drake Passage moves about 4°northward because of the inducement of winddrivencurrents. The clockwise vorticity appearing in the south-west corner corresponds to the Weddell Gyre.The characters of the Antarctic Circumpolar Current described by the model are congruous with observations basically.展开更多
The Antarctic circumpolar wave （ACW） has become a focus of the air-sea coupled Southern Ocean study since 1996, when it was discovered as an air-sea coupled interannual signal propagating eastward in the region of t...The Antarctic circumpolar wave （ACW） has become a focus of the air-sea coupled Southern Ocean study since 1996, when it was discovered as an air-sea coupled interannual signal propagating eastward in the region of the Antarctic Circumpolar Current （ACC）. In order to analyze the mechanism of discontinuity along the latitudinal propagation, a new idea that ACW is a system with a traveling wave in the Southern Pacific and Atlantic Ocean and with a concurrent standing wave in the southern Indian Ocean is proposed in this paper. Based on the ideal wave principle, the average wave parameters of ACW is achieved using a non-linear approximation method, by which we find that the standing part and the traveling part possess similar radius frequency, proving their belonging to an integral system. We also give the latitudinal distribution of wave speed with which we could tell the reason for steady propagation during the same period. The spatial distribution of the propagation reveals complex process with variant spatial and temporal scales--The ENSO scale oscillation greatly impacts on the traveling process, while the result at the south of Australia indicates little connection between the Indian Ocean and the Pacific, which may be blocked by the vibration at the west of the Pacific. The advective effect of ACC on the propagation process should be examined clearly through dynamical method.展开更多
The melting of the West Antarctic Ice Shelf has increased since the 1990s,driven by the relatively warm Circumpolar Deep Water(CDW)that penetrates into the West Antarctic Ice Shelf cavities through submarine glacial t...The melting of the West Antarctic Ice Shelf has increased since the 1990s,driven by the relatively warm Circumpolar Deep Water(CDW)that penetrates into the West Antarctic Ice Shelf cavities through submarine glacial troughs across the continental shelf.In this study,temperature,salinity,and current velocity data obtained by the Chinese National Antarctic Research Expedition in the Dotson-Getz Trough(DGT)shows clear differences in distribution of modified Circumpolar Deep Water(mCDW)in the summers of 2020 and 2022.Combined with contemporaneous wind data and additional temperature and salinity data from instrumented seals,the processes and mechanisms responsible for this variation are discussed.Compared with 2020,there is a significant increase in mCDW thickness in 2022,with a doubling of total heat content as the mCDW inflow path across the DGT shifts towards the eastern bank.We propose that a southward shift in the westerly winds in the summer of 2022 moved the upper oceanic divergence zone southward towards the continental slope,promoting the upwelling of mCDW above 500 m.Concurrently,stronger westerly winds over the continental slope strengthened the eastward undercurrent,increasing the transport of this mCDW and its associated heat content to the DGT through Ekman dynamics.These observations show there is strong interannual variability in the strength,path and extent of mCDW inflows to the DGT and that care must be taken when planning observation programs for long-term monitoring of the oceanic heat input to the ice shelves of this globally significant region.展开更多
The data from the Southern Ocean observations of World Ocean Circulation Experiment （WOCE） are used for analysis and illustration of the features and spatial distributions of Circumpolar Deep Water （CDW） in the so...The data from the Southern Ocean observations of World Ocean Circulation Experiment （WOCE） are used for analysis and illustration of the features and spatial distributions of Circumpolar Deep Water （CDW） in the southern Indian Ocean. It is learnt from the comparison among the vertical distributions of temperature/ salinity/oxygen along the 30°E, 90°E and 145°E sections respectively that some different features of CDW and the fronts can be found at those longitudes, and those differences can be attributed to the zonal transoceanic flow and the merizonal movement in the Circumpolar Deep Water. In fact, the zonal transoceanic flow is the main dynamic factor for the water exchange between the Pacific Ocean and the /ndian Ocean or between the Atlantic Ocean and the Indian Ocean, and for the effects on the spatial distributions of the physical properties in CDW.展开更多
We compare the characteristics of Circumpolar Deep Water(CDW)in the Amundsen Sea based on Conductivity-Temperature-Depth(CTD)records in the World Ocean Database.There are considerable numbers of ship-based CTD casts i...We compare the characteristics of Circumpolar Deep Water(CDW)in the Amundsen Sea based on Conductivity-Temperature-Depth(CTD)records in the World Ocean Database.There are considerable numbers of ship-based CTD casts in the year 1994,2000,2007 and 2009.After confining temporal-and spatial-windows,several stations are emerged as having at-least two casts in different years.The comparisons show that the CDWs turn warmer and salter on shelf and near ice shelf.The results therefore describe the geographic differences of CDW changes,and exhibit rareness of ship-based CTD survey in the Amundsen Sea.展开更多
Stable growth of the elderly age group is observed in the population of circumpolar areas of Russia. In northern conditions chronic pathology facilitates activity restriction development, changing the habitual lifesty...Stable growth of the elderly age group is observed in the population of circumpolar areas of Russia. In northern conditions chronic pathology facilitates activity restriction development, changing the habitual lifestyle. Ageing process involves functional constraints of physical and mental activities, difficulties in doing everyday work. Aging changes of the nervous and respiratory systems are more characteristic of aged men and women living in the nursing home system of Russian urban circumpolar area. These changes are caused by worse psychological state, hypokinesia so there is a need in improving approaches in medical and social care services, in particular, introducing activating technologies and the micro-environment enhancement.展开更多
The Southern Ocean is a critical component in the Earth system by dominating the global heat and anthropogenic carbon uptake and supplying heat to melt the largest ice sheet.Variability and changes in the water masses...The Southern Ocean is a critical component in the Earth system by dominating the global heat and anthropogenic carbon uptake and supplying heat to melt the largest ice sheet.Variability and changes in the water masses of the Southern Ocean are thus important to the global energy and water cycles,carbon cycling,and sea-level change.In this article,we review the recent progress on understanding the variability and changes in the four major water masses in the Southern Ocean,including Subantarctic Mode Water,Antarctic Intermediate Water,Circumpolar Deep Water and Antarctic Bottom Water.Subantarctic Mode Water and Antarctic Intermediate Water show statistically significant strong circumpolar shoaling,warming,and density reductions since 1970s,indicating that signals of global warming have entered the interior ocean.Meanwhile,strong regional variability of Subantarctic Mode Water and Antarctic Intermediate Water responding to surface buoyancy forcing and westerly winds is attracting more attention.Circumpolar Deep Water is an important modulator of heat content and nutrient concentrations on continental shelves around Antarctica and has made significant contributions to the basal melting of Antarctic ice shelves.Since the late 1950s,a long-term freshening trend in Antarctic Bottom Water in the Ross Sea and its downstream region has been observed and is mainly attributed to the accelerated basal melting of ice shelves in West Antarctica.The shrinking of Antarctic Bottom Water in the Weddell Sea during 1992–2020 has also been revealed and is attributed to reduced sea ice production over the southern Weddell continental shelf related to the Interdecadal Pacific Oscillation and the variability in the Amundsen Sea Low.Though significant advances have been achieved,there is an urgent need to enhance and improve both observations and model performances for better understandings and projections of the formation,transformation,and transport of the water masses in the Southern Ocean.展开更多
The Antarctic Circumpolar Current (ACC) and its associated Meridional Overturning Circulation (MOC) is investigated through a nonlinear inertia theory model, which consists of two layers--an upper Ekman layer driven m...The Antarctic Circumpolar Current (ACC) and its associated Meridional Overturning Circulation (MOC) is investigated through a nonlinear inertia theory model, which consists of two layers--an upper Ekman layer driven mainly by sea surface wind stress and a lower thermocline controlled by ideal fluid nonlinear equations which can be solved by identifying the form of the arbitrary functions. The results show that the thermocline has a two-equilibrium solution though given the same Ekman layer condition. Compared to the first equilibrium, the second one has a heavier intensity and deeper circulation, which seems more consistent with the existing data.展开更多
西南极绕极深层水(CircumpolarDeepWater,CDW)是源于南极绕极流的暖水团,也被认为是多特森—盖茨海槽的热源,但对其气候态分布特征了解甚少。本文基于观测分析数据(EN4)、EstimatingtheCirculation&Climate of theOcean(ECCO)和Cope...西南极绕极深层水(CircumpolarDeepWater,CDW)是源于南极绕极流的暖水团,也被认为是多特森—盖茨海槽的热源,但对其气候态分布特征了解甚少。本文基于观测分析数据(EN4)、EstimatingtheCirculation&Climate of theOcean(ECCO)和Copernicus Global (1/12)°Oceanic and Sea Ice(GLORYS12)再分析资料,分析了多特森—盖茨海槽CDW水团夏季(1月)的气候态分布特征。结果表明, CDW上边界深度沿西阿蒙森海海盆纬向断面呈现一定的纬向变化, CDW温度和盐度分别达到1℃和34.7;CDW上边界深度沿多特森—盖茨海槽断面具有一定的变化,相应的CDW温度和盐度分别高于0℃和34.6;对于跨多特森—盖茨海槽断面, CDW温度和盐度存在东西向差异,海槽东侧CDW温度和盐度较高。展开更多
Oxygen stable isotopic and ionic records, cov- ering a period of 1745—1996, are recovered in DT001 ice core drilled in Princess Elizabeth Land, East Antarctica. Using empirical orthogonal function (EOF) analysis of t...Oxygen stable isotopic and ionic records, cov- ering a period of 1745—1996, are recovered in DT001 ice core drilled in Princess Elizabeth Land, East Antarctica. Using empirical orthogonal function (EOF) analysis of the annually resolved glaciochemical time series, we find the first EOF (EOF1) represents sea-salt aerosols and is the proxy of sea level pressure (SLP) over a quasi-stationary low in the Southern Indian Ocean (SIO). δ O represents the sea sur- 18 face temperature (SST) of the same ocean area. In the past two decades, four climatic waves as represented by SLP and SST proxies are found in the DT001 ice core, which in coin- cident with four Antarctic Circum-polar Waves (ACW) as revealed by NCEP/NCAR reanalysis. The phase difference between SST and SLP in the ice core is also coincident with that in ACW. Both ice-core record and reanalysis suggest that there were no signals of ACW during 1958—1980, none during the overall recording period between 1745—1996, as there is no regular phase difference between SST and SLP. The ACW signal after early 1980s is probably attributable to the climate shift occurring over Antarctic Peninsula-Drake Passage region.展开更多
Nitrification,a central process in the marine nitrogen cycle,produces regenerated nitrate in the euphotic zone and emits N_(2)O,a potent greenhouse gas as a by-product.The regulatory mechanisms of nitrification in the...Nitrification,a central process in the marine nitrogen cycle,produces regenerated nitrate in the euphotic zone and emits N_(2)O,a potent greenhouse gas as a by-product.The regulatory mechanisms of nitrification in the Southern Ocean,which is a critical region for CO_(2)sequestration and radiative benefits,remain poorly understood.Here,we investigated the in situ and dark nitrification rates in the upper 500 m and conducted substrate kinetics experiments across the Indian Sector in the Cosmonaut and Cooperation seas in the late austral summer.Our findings indicate that light inhibition of nitrification decreases exponentially with depth,exhibiting a light threshold of 0.53%photosynthetically active radiation.A positive relationship between dark nitrification and apparent oxygen utilization suggests a dependence on substrate availability from primary production.Importantly,an increased NH_(4)^(+) supply can act as a buffer against photo-inhibitory damage.Globally,substrate affinity(α)increases with depth and transitions from light to dark,decreases with increasing ambient NH_(4)^(+)and exhibits a latitudinal distribution,reflecting substrate utilization strategies.We also reveal that upwelling in Circumpolar Deep Water(CDW)stimulates nitrification through the introduction of potentially higher iron and deep diverse nitrifying microorganisms with higherα.We conclude that although light is the primary limiting factor for nitrification in summer,coupling between substrate availability and CDW upwelling can overcome this limitation,thereby alleviating photoinhibition by up to 45%±5.3%.展开更多
By comparing the oxygen isotopic temperatures recorded by many shallow ice cores from the coastal regions of Antarctica, this paper presents the special characteristics of the temperature variations over the Antarctic...By comparing the oxygen isotopic temperatures recorded by many shallow ice cores from the coastal regions of Antarctica, this paper presents the special characteristics of the temperature variations over the Antarctic coastal regions in the past 50 years, 150 years and 250 years. In the past 50 years, the isotopic temperatures recorded in the ice cores over different sites on the Antarctic coastal regions differ greatly. For instance, although increasing isotopic temperatures have been reported for many sites studied, many sites show decreasing trends, the regional regularity in temperature variations is still insignificant. In the past 150 years, the isotopic temperature trends in the coastal regions of Antarctica show an alternate-distributing pattern. In the past 250 years, all the ice cores from the coastal regions of Antarctica have recorded the so-called Little Ice Age (LIA). The above-mentioned spatial characteristics of the temperature variations over the Antarctic coastal regions are likely to reflect the impacts of the unique Southern Hemisphere atmospheric circulation, the Antarctic Circumpolar Wave (ACW) and the special terrain (such as the large drainage basins) on the coastal regions of Antarctica. Furthermore, the impacting intensity of the unique Southern Hemisphere atmospheric circulation, the Antarctic Circumpolar Wave and the special terrain differs in terms of the temporal scale of the temperature change.展开更多
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.42130402)the International Science and Technology Cooperation Key Special Project of the National Key Research and Development Program of China(No.2023YFE0104500)。
文摘The Antarctic Bottom Water formation site Vincennes Bay,East Antarctica is experiencing a substantial intrusion of modified Circumpolar Deep Water(mCDW),which may inhibit the formation of Dense Shelf Water(DSW)and drive basal melting of the ice shelves.Based on hydrographic data obtained from March to November in 2012,we evaluated the spatial spread of mCDW over the continental shelf region of Vincennes Bay and the associated temporal evolution of water properties,as well as the sea ice formation effect on water column in the coastal polynya.Results show that two branches of mCDW occupied the deep layers of the continental shelf,distinguished by the potential density(smaller than 27.8 kg/m^(3) or not)when potential temperatureθ=0.5°C in theθ-salinity space.The warmer and less dense branch observed on the east plateau,accessed the eastern ice shelves in the coastal polynya to drive basal melting of ice shelves.In contrast,the other colder and denser branch in the mid-depression reached the western Underwood Ice Shelf.DSW formation was detectable in the coastal polynya during September-November,proving the occurrence of deep convection.Surface heat loss and brine rejection during the intensive sea ice formation contributed to the destratification of the water column in the coastal polynya.It was estimated that at least 1.11±0.79 TW heat carried by mCDW into the inner part of the polynya.
基金The National Natural Science Foundation of China under contract No.41605052。
文摘An obvious trend shift in the annual mean and winter mixed layer depth(MLD)in the Antarctic Circumpolar Current(ACC)region was detected during the 1960–2021 period.Shallowing trends stopped in mid-1980s,followed by a period of weak trends.The MLD deepening trend difference between the two periods were mainly distributed in the western areas in the Drake Passage,the areas north to Victoria Land and Wilkes Land,and the central parts of the South Indian sector.The newly formed ocean current shear due to the meridional shift of the ACC flow axis between the two periods is the dominant driver for the MLD trends shift distributed in the western areas in the Drake Passage and the central parts of the South Indian sector.The saltier trends in the regions north to Victoria Land and Wilkes Land could be responsible for the strengthening mixing processes in this region.
基金The National Natural Science Foundation of China under contract Nos 40976005 and 40930844
文摘The low-frequency variance of the surface wave in the area of the Antarctic Circumpolar Current （ACC） and its correlation with the antarctic circumpolar wave （ACW） are focused on. The analysis of the series of 44 a significant wave height （SWH） interannual anomalies reveals that the SWH anomalies have a strong periodicity of about 4-5 a and this signal propagates eastward obviously from 1985 to 1995, which needs about 8 a to complete a mimacircle around the earth. The method of empirical orthogonal function （EOF） is used to analyze the filtered monthly SWH anomalies to study the spatio-temporal distributions and the propagation characteristics of the low-frequency signals in the wave field. Both the dominant wavenumber- 2 pattern in space and the propagation feature in the south Pacific, the south Atlantic and the south Indian ocean show strong consistency with the ACW. So it is reasonable to conclude that the ACW signal also exists in the wave field. The ACW is important for the climate in the Southern Ocean, so it is worth to pay more attention to the large- scale effect of the surface wave, which may also be important for climate studies.
基金The National Natural Science Foundation of China under contract Nos 40930844 and 40976005
文摘Based on the data and method offered by Liu et al. （2009）, the direct wind and Stokes drift-induced energy inputs into the Ekman layer within the Antarctic Circumpolar Current （ACC） area are reestimated since the results of the former have been proved to be underestimated. And the result shows that the total rate of energy input into the Ekman-Stokes layer within the ACC area is 852.41 GW, including 649.75 GW of direct wind energy input （76%） and 202.66 GW of Stoke drift-induced energy input （24%）. Total increased energy input, due to wave-induced Coriolis-Stokes forcing added to the classical Ekman model, is 52.05 GW, accounting for 6.5% of the wind energy input into the classical Ekman layer. The long-term variability of direct wind and Stokes drift-induced energy inputs into the Ekman layer within the ACC is also investigated, and the result shows that the Stokes drift hinders the decadal increasing trend of direct wind energy input. Meanwhile, there is a period of 4-5 a in the energy spectrums, as same as the Antarctic circumpolar wave.
基金The National High Technology Research and Development Program ("863" Program) of China under contract Nos 2008AA121701 and 2007AA092201the National Natural Science Foundation of China under contract No.41006013
文摘Fronts, baroclinic transport, and mesoscale variability of the Antarctic Circumpolar Current （ACC） along 115°E are examined on the basis of CTD data from two hydrographic cruises occupied in 1995 as a part of the World Ocean Circulation Experiment （WOCE cruise I9S） and in 2004 as a part of CLIVAR/CO2 repeat hydrography program. The integrated baroclinic transport across I9S section is （97.2×106±2.2×106） m3/s relative to the deepest common level （DCL）. The net transport at the north end of I9S, determined by the south Australian circulation system, is about 16.5× 106 m3/s westward. Relying on a consistent set of water mass criteria and transport maxima, the ACC baroclinic transport, （117×106±6.7×106） m3/s to the east, is carried along three fronts： the Subantarctic Front （SAF） at a mean latitude of 44°-49°S carries （50.6×106=t=13.4×106） m3/s; the Polar Front （PF）, with the northern branch （PF-N） at 50.5°S and the southern branch （PF- S） at 58°S, carries （51.3×106±8.7×106） m3/s; finally, the southern ACC front （SACCF） and the southern boundary of the ACC （SB） consist of three cores between 59°S and 65°S that combined carry （15.2× 106±1.8× 106） m3/s. Mesoscale eddy features are identifiable in the CTD sections and tracked in concurrent maps of altimetric sea level anomalies （SLA） between 44°-48°S and 53°-57°S. Because of the remarkable mesoseale eddy features within the SAF observed in both the tracks of the cruises, the eastward transport of the SAF occurs at two latitude bands separating by 1°. Both the CTD and the altimetric data suggest that the mesoscale variability is concentrated around the Antarctic Polar Frontal Zone （APFZ） and causes the ACC fronts to merge, diverge, and to fluctuate in intensity and position along their paths.
文摘Based on a linear quasi-geostrophic vorticity equation, we have set up an analytical diagnostic mode for the Antarctic Circumpolar Current. The results show that the balance among wind stress,ocean horizontal viscous stress and the β-effect is the basic balance of the Antarctic Circumpolar Current, and the center velocity of the jet, coming from the Drake Passage,will decrease due to the ocean dynamic adjustment, and the width in the north-south direction will decreasegradually. The jet coming from the Drake Passage moves about 4°northward because of the inducement of winddrivencurrents. The clockwise vorticity appearing in the south-west corner corresponds to the Weddell Gyre.The characters of the Antarctic Circumpolar Current described by the model are congruous with observations basically.
文摘The Antarctic circumpolar wave （ACW） has become a focus of the air-sea coupled Southern Ocean study since 1996, when it was discovered as an air-sea coupled interannual signal propagating eastward in the region of the Antarctic Circumpolar Current （ACC）. In order to analyze the mechanism of discontinuity along the latitudinal propagation, a new idea that ACW is a system with a traveling wave in the Southern Pacific and Atlantic Ocean and with a concurrent standing wave in the southern Indian Ocean is proposed in this paper. Based on the ideal wave principle, the average wave parameters of ACW is achieved using a non-linear approximation method, by which we find that the standing part and the traveling part possess similar radius frequency, proving their belonging to an integral system. We also give the latitudinal distribution of wave speed with which we could tell the reason for steady propagation during the same period. The spatial distribution of the propagation reveals complex process with variant spatial and temporal scales--The ENSO scale oscillation greatly impacts on the traveling process, while the result at the south of Australia indicates little connection between the Indian Ocean and the Pacific, which may be blocked by the vibration at the west of the Pacific. The advective effect of ACC on the propagation process should be examined clearly through dynamical method.
基金This work is supported by Chinese Arctic and Antarctic Administration(Grant no.IRASCC2020-2022)National Key R&D Program of China(Grant no.2018YFA0605701).
文摘The melting of the West Antarctic Ice Shelf has increased since the 1990s,driven by the relatively warm Circumpolar Deep Water(CDW)that penetrates into the West Antarctic Ice Shelf cavities through submarine glacial troughs across the continental shelf.In this study,temperature,salinity,and current velocity data obtained by the Chinese National Antarctic Research Expedition in the Dotson-Getz Trough(DGT)shows clear differences in distribution of modified Circumpolar Deep Water(mCDW)in the summers of 2020 and 2022.Combined with contemporaneous wind data and additional temperature and salinity data from instrumented seals,the processes and mechanisms responsible for this variation are discussed.Compared with 2020,there is a significant increase in mCDW thickness in 2022,with a doubling of total heat content as the mCDW inflow path across the DGT shifts towards the eastern bank.We propose that a southward shift in the westerly winds in the summer of 2022 moved the upper oceanic divergence zone southward towards the continental slope,promoting the upwelling of mCDW above 500 m.Concurrently,stronger westerly winds over the continental slope strengthened the eastward undercurrent,increasing the transport of this mCDW and its associated heat content to the DGT through Ekman dynamics.These observations show there is strong interannual variability in the strength,path and extent of mCDW inflows to the DGT and that care must be taken when planning observation programs for long-term monitoring of the oceanic heat input to the ice shelves of this globally significant region.
基金the National Science Foundation of China under Contract Nos.40376009 and 40676011.
文摘The data from the Southern Ocean observations of World Ocean Circulation Experiment （WOCE） are used for analysis and illustration of the features and spatial distributions of Circumpolar Deep Water （CDW） in the southern Indian Ocean. It is learnt from the comparison among the vertical distributions of temperature/ salinity/oxygen along the 30°E, 90°E and 145°E sections respectively that some different features of CDW and the fronts can be found at those longitudes, and those differences can be attributed to the zonal transoceanic flow and the merizonal movement in the Circumpolar Deep Water. In fact, the zonal transoceanic flow is the main dynamic factor for the water exchange between the Pacific Ocean and the /ndian Ocean or between the Atlantic Ocean and the Indian Ocean, and for the effects on the spatial distributions of the physical properties in CDW.
基金financially supported by National Polar Special Program“Impact and Response of Antarctic Seas to Climate Change”(Grant nos.IRASCC 01-01-01B,02-01-02).
文摘We compare the characteristics of Circumpolar Deep Water(CDW)in the Amundsen Sea based on Conductivity-Temperature-Depth(CTD)records in the World Ocean Database.There are considerable numbers of ship-based CTD casts in the year 1994,2000,2007 and 2009.After confining temporal-and spatial-windows,several stations are emerged as having at-least two casts in different years.The comparisons show that the CDWs turn warmer and salter on shelf and near ice shelf.The results therefore describe the geographic differences of CDW changes,and exhibit rareness of ship-based CTD survey in the Amundsen Sea.
文摘Stable growth of the elderly age group is observed in the population of circumpolar areas of Russia. In northern conditions chronic pathology facilitates activity restriction development, changing the habitual lifestyle. Ageing process involves functional constraints of physical and mental activities, difficulties in doing everyday work. Aging changes of the nervous and respiratory systems are more characteristic of aged men and women living in the nursing home system of Russian urban circumpolar area. These changes are caused by worse psychological state, hypokinesia so there is a need in improving approaches in medical and social care services, in particular, introducing activating technologies and the micro-environment enhancement.
基金The Independent Research Foundation of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)under contract Nos SML2023SP201 and SML2021SP306the Natural Science Foundation of Guangdong Province of China under contract No.2024A1515012717+5 种基金the Initial Research Foundation of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)under contract Nos 313021004,313022009,and 313022001the National Natural Science Foundation of China under contract No.41706225the National Key R&D Program of China under contract No.2018YFA0605701the Impact and Response of Antarctic Seas to Climate Change under contract No.IRASCC 1-02-01Bthe Shenlan Program funded by Shanghai Jiao Tong University under contract No.SL2020MS021the fund from Shanghai Frontiers Science Center of Polar Research.
文摘The Southern Ocean is a critical component in the Earth system by dominating the global heat and anthropogenic carbon uptake and supplying heat to melt the largest ice sheet.Variability and changes in the water masses of the Southern Ocean are thus important to the global energy and water cycles,carbon cycling,and sea-level change.In this article,we review the recent progress on understanding the variability and changes in the four major water masses in the Southern Ocean,including Subantarctic Mode Water,Antarctic Intermediate Water,Circumpolar Deep Water and Antarctic Bottom Water.Subantarctic Mode Water and Antarctic Intermediate Water show statistically significant strong circumpolar shoaling,warming,and density reductions since 1970s,indicating that signals of global warming have entered the interior ocean.Meanwhile,strong regional variability of Subantarctic Mode Water and Antarctic Intermediate Water responding to surface buoyancy forcing and westerly winds is attracting more attention.Circumpolar Deep Water is an important modulator of heat content and nutrient concentrations on continental shelves around Antarctica and has made significant contributions to the basal melting of Antarctic ice shelves.Since the late 1950s,a long-term freshening trend in Antarctic Bottom Water in the Ross Sea and its downstream region has been observed and is mainly attributed to the accelerated basal melting of ice shelves in West Antarctica.The shrinking of Antarctic Bottom Water in the Weddell Sea during 1992–2020 has also been revealed and is attributed to reduced sea ice production over the southern Weddell continental shelf related to the Interdecadal Pacific Oscillation and the variability in the Amundsen Sea Low.Though significant advances have been achieved,there is an urgent need to enhance and improve both observations and model performances for better understandings and projections of the formation,transformation,and transport of the water masses in the Southern Ocean.
基金supported by National Basic Research Program of China (Grant No. 2010CB950300)
文摘The Antarctic Circumpolar Current (ACC) and its associated Meridional Overturning Circulation (MOC) is investigated through a nonlinear inertia theory model, which consists of two layers--an upper Ekman layer driven mainly by sea surface wind stress and a lower thermocline controlled by ideal fluid nonlinear equations which can be solved by identifying the form of the arbitrary functions. The results show that the thermocline has a two-equilibrium solution though given the same Ekman layer condition. Compared to the first equilibrium, the second one has a heavier intensity and deeper circulation, which seems more consistent with the existing data.
文摘西南极绕极深层水(CircumpolarDeepWater,CDW)是源于南极绕极流的暖水团,也被认为是多特森—盖茨海槽的热源,但对其气候态分布特征了解甚少。本文基于观测分析数据(EN4)、EstimatingtheCirculation&Climate of theOcean(ECCO)和Copernicus Global (1/12)°Oceanic and Sea Ice(GLORYS12)再分析资料,分析了多特森—盖茨海槽CDW水团夏季(1月)的气候态分布特征。结果表明, CDW上边界深度沿西阿蒙森海海盆纬向断面呈现一定的纬向变化, CDW温度和盐度分别达到1℃和34.7;CDW上边界深度沿多特森—盖茨海槽断面具有一定的变化,相应的CDW温度和盐度分别高于0℃和34.6;对于跨多特森—盖茨海槽断面, CDW温度和盐度存在东西向差异,海槽东侧CDW温度和盐度较高。
基金This study was supported by the National Natural Science Foundation of China(Grant No.40305007)Ministry of Science and Technology of China(Grant No.2001CB711003).
文摘Oxygen stable isotopic and ionic records, cov- ering a period of 1745—1996, are recovered in DT001 ice core drilled in Princess Elizabeth Land, East Antarctica. Using empirical orthogonal function (EOF) analysis of the annually resolved glaciochemical time series, we find the first EOF (EOF1) represents sea-salt aerosols and is the proxy of sea level pressure (SLP) over a quasi-stationary low in the Southern Indian Ocean (SIO). δ O represents the sea sur- 18 face temperature (SST) of the same ocean area. In the past two decades, four climatic waves as represented by SLP and SST proxies are found in the DT001 ice core, which in coin- cident with four Antarctic Circum-polar Waves (ACW) as revealed by NCEP/NCAR reanalysis. The phase difference between SST and SLP in the ice core is also coincident with that in ACW. Both ice-core record and reanalysis suggest that there were no signals of ACW during 1958—1980, none during the overall recording period between 1745—1996, as there is no regular phase difference between SST and SLP. The ACW signal after early 1980s is probably attributable to the climate shift occurring over Antarctic Peninsula-Drake Passage region.
基金The National Natural Science Foundation of China under contract No.41721005the Fund of the Ministry of Natural Resources of the People’s Republic of China under contract Nos IRASCC 02-01-01 and 01-01-02C.
文摘Nitrification,a central process in the marine nitrogen cycle,produces regenerated nitrate in the euphotic zone and emits N_(2)O,a potent greenhouse gas as a by-product.The regulatory mechanisms of nitrification in the Southern Ocean,which is a critical region for CO_(2)sequestration and radiative benefits,remain poorly understood.Here,we investigated the in situ and dark nitrification rates in the upper 500 m and conducted substrate kinetics experiments across the Indian Sector in the Cosmonaut and Cooperation seas in the late austral summer.Our findings indicate that light inhibition of nitrification decreases exponentially with depth,exhibiting a light threshold of 0.53%photosynthetically active radiation.A positive relationship between dark nitrification and apparent oxygen utilization suggests a dependence on substrate availability from primary production.Importantly,an increased NH_(4)^(+) supply can act as a buffer against photo-inhibitory damage.Globally,substrate affinity(α)increases with depth and transitions from light to dark,decreases with increasing ambient NH_(4)^(+)and exhibits a latitudinal distribution,reflecting substrate utilization strategies.We also reveal that upwelling in Circumpolar Deep Water(CDW)stimulates nitrification through the introduction of potentially higher iron and deep diverse nitrifying microorganisms with higherα.We conclude that although light is the primary limiting factor for nitrification in summer,coupling between substrate availability and CDW upwelling can overcome this limitation,thereby alleviating photoinhibition by up to 45%±5.3%.
基金The National Natural Science Foundation of China No.49971021+5 种基金The Chinese Academy of SciencesNo. KZCX2-303The Ministry of Science and Technology of China No.2001DIA50040Northwest Normal University No.NWNU-KJCXGC-02-20
文摘By comparing the oxygen isotopic temperatures recorded by many shallow ice cores from the coastal regions of Antarctica, this paper presents the special characteristics of the temperature variations over the Antarctic coastal regions in the past 50 years, 150 years and 250 years. In the past 50 years, the isotopic temperatures recorded in the ice cores over different sites on the Antarctic coastal regions differ greatly. For instance, although increasing isotopic temperatures have been reported for many sites studied, many sites show decreasing trends, the regional regularity in temperature variations is still insignificant. In the past 150 years, the isotopic temperature trends in the coastal regions of Antarctica show an alternate-distributing pattern. In the past 250 years, all the ice cores from the coastal regions of Antarctica have recorded the so-called Little Ice Age (LIA). The above-mentioned spatial characteristics of the temperature variations over the Antarctic coastal regions are likely to reflect the impacts of the unique Southern Hemisphere atmospheric circulation, the Antarctic Circumpolar Wave (ACW) and the special terrain (such as the large drainage basins) on the coastal regions of Antarctica. Furthermore, the impacting intensity of the unique Southern Hemisphere atmospheric circulation, the Antarctic Circumpolar Wave and the special terrain differs in terms of the temporal scale of the temperature change.
