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Adaptations of phytoplankton in the Indian ocean sector of the southern ocean during austral summer of 1998-2014

Frontiers of Earth Science 2015年第4期9卷 742-752页

作者： R. K. MISHRA R. K. NAIK N. ANIL KUMAR ESSO-National Centre for Antarctic and ocean Research Ministry of Earth Sciences (MoES) Vasco-da-Gama Goa India

This study investigates the effects of light and temperature on the surface water diatoms and chloro- phytes, phytoplankton in the Indian ocean sector of the southern ocean （SO） during the austral summer of 1998- 2014. Significant longitudinal variations in hydrographic and biological parameters were observed at the Sub tropical front （STF）, Sub Antarctic front （SAF） and Polar front （PF） along 56°E-58°E. The concentrations of total surface chlorophyll a （Chl a）, diatoms, and chlorophytes measured by the National Aeronautics Space Agency （NASA） estimated by the Sea-Viewing Wide Field-of- View Sensors （SeaWiFS）, the Moderate Resolution Imaging Spectro Radiometer （MODIS）, and the NASA ocean Biological Model （NOBM） were used in the study. Variations in the concentration of total Chl a was remarkable amongst the fronts during the study period. The contribution of diatoms to the total concentration of surface Chl a increased towards south from the STF to the PF while it decreased in the case of chlorophytes. The maximum photosynthetically active radiation （PAR） was observed at the STF and it progressively decreased to the PF through the SAF. At the PF region the contribution of diatoms to the total Chl a biomass was ≥80%. On the other hand, the chlorophytes showed a contrary distribution pattern with ≥ 70% of the total Chl a biomass recorded at the STF which gradually decreased towards the PF, mainly attributed to the temperate adaptation. This clearly reveals that the trend of diatoms increased at the STF and decreased at the SAF and the PF. Further, the trend of chlorophytes was increased at the STF, SAF and PF with a shift in the community in the frontal system of the Indian ocean sector of the SO.

关键词： chlorophyll a diatoms chlorophytes SST,PAR southern ocean

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Eddy diffusivity and coherent mesoscale eddy analysis in the southern ocean

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Acta oceanologica Sinica 2021年第10期40卷 1-16页

作者： Wenjin Sun Jingsong Yang Wei Tan Yu Liu Baojun Zhao Yijun He Changming Dong School of Marine Sciences Nanjing University of Information Science and TechnologyNanjing 210044China State Key Laboratory of Satellite ocean Environment Dynamics Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519080China College of ocean Science and Engineering Shandong University of Science and TechnologyQingdao 266590China Marine Science and Technology College Zhejiang Ocean UniversityZhoushan 316022China College of Hydraulic Science and Engineering Yangzhou UniversityYangzhou 225009China

The spatial distribution of eddy diffusivity,basic characteristics of coherent mesoscale eddies and their relationship are analyzed from numerical model outputs in the southern *** fluctuation information is obtained by a temporal-spatial filtering method,and the eddy diffusivity is calculated using a linear regression analysis between isoneutral thickness flux and large-scale isoneutral thickness *** eddy diffusivity is on the order of O(103 m2/s)with a significant spatial variation,and it is larger in the area with strong coherent mesoscale eddy *** mesoscale eddies are mainly located in the upper ocean layer,with the average intensity no larger than *** mean radius of the coherent mesoscale cyclonic(anticyclonic)eddy gradually decays from(121.2±10.4)km((117.8±9.6)km)at 30°S to(43.9±5.3)km((44.7±4.9)km)at 65°*** vertical penetration depths(lifespans)are deeper(longer)between the northern side of the Subpolar Antarctic Front and 48°*** normalized eddy diffusivity and coherent mesoscale eddy activity show a significant positive correlation,indicating that coherent mesoscale eddy plays an important role in eddy diffusivity.

关键词： eddy diffusivity transient mesoscale eddy coherent mesoscale eddy eddy penetration depth southern ocean

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Nitrogen uptake by phytoplankton in surface waters of the Indian sector of southern ocean during austral summer

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Frontiers of Earth Science 2018年第1期12卷 52-62页

作者： S. C. TRIPATHY SIVAJI PATRA K. VISHNU VARDHAN A. SARKAR R. K. MISHRA N. ANILKUMAR ESSO-National Centre for Antarctic and ocean Research Ministry of Earth Sciences Headland Sada Vasco-da-Gama Goa 403804 India ESSO-Integrated Coastal and Marine Area Management-PD Ministry of Earth Sciences NIOT Campus Velachery Pallikaranai Chennai 600100 India

This study reports the nitrogen uptake rate （using 15N tracer） of phytoplankton in surface waters of different frontal zones in the Indian sector of the southern ocean （SO） during austral summer of 2013. The investigated area encompasses four major frontal systems, i.e., the subtropical front （STF）, subantarctic front （SAF）, polar front-1 （PF1） and polar front-2 （PF2）. Southward decrease of surface water temperature was observed, whereas surface salinity did not show any significant trend. Nutrient （NO3- and SiO44-） concentrations increased southward from STF to PF; while ammonium （NH4＋）, nitrite （NO2-） and phosphate （PO433 remained compara- tively stable. Analysis of nutrient ratios indicated potential N-limited conditions at the STF and SAF but no such scenario was observed for PF. In terms of phytoplankton biomass, PF1 was found to be the most productive followed by SAF, whereas PF2 was the least productive region. Nitrate uptake rate increased with increasing latitude, as no systematic spatial variation was discerned for NH4＋ and urea （CO（NH2）2）. Linear relationship between nitrate and total N-uptake reveals that the studied area is capable of exporting up to 60% of the total production to the deep ocean if the environmental settings are favorable. Like N-uptake rates the f-ratio also increased towards PF region indicating comparatively higher new production in the PF than in the subtropics. The moderately high averagefiratio （0.53） indicates potentially near equal contributions by new production and regenerated production to the total productivity in the study area. Elevation in N-uptake rates with declining temperature suggests that the SO with its vast quantity of cool water could play an important role in drawing down the atmospheric CO2 through the ＂solubility pump＂.

关键词： nitrogen uptake f-ratio new productivity,frontal zones southern ocean

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The Effect of Diapycnal Mixing on the Ventilation and CFC-11 Uptake in the southern ocean

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Advances in Atmospheric Sciences 2004年第5期21卷 755-766页

作者： Helge DRANGE Nansen Environmental and Remote Sensing Center Bergen Norway Nansen-Zhu International Research Centre Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029Bjerknes Centre for Climate Research Bergen Norway Geophysical Institute University of Bergen Bergen Norway

The Miami Isopycnic Coordinate ocean Model (MICOM) is used to investigate the effect of diapycnal mixing on the oceanic uptake of CFC-11 and the ventilation of the surface waters in the southern ocean (south of 45°S). Three model experiments are performed: one with a diapycnal mixing coefficientK d (m2 s?1) of 2 × 10?7/N (Expt. 1), one withK d = 0 (Expt. 2), and one withK d = 5 × 10?8/N (Expt. 3),N (s?1) is the Brunt-V?is?l? frequency. The model simulations indicate that the observed vertical distribution of CFC-11 along 88°W (prime meridian at 0°E) in the southern ocean is caused by local ventilation of the surface waters and westward-directed (eastward-directed) isopycnic transport and mixing from deeply ventilated waters in the Weddell Sea region. It is found that at the end of 1997, the simulated net ocean uptake of CFC-11 in Expt. 2 is 25% below that of Expt. 1. The decreased uptake of CFC-11 in the southern ocean accounts for 80% of this difference. Furthermore, Expts. 2 and 3 yield far more realistic vertical distributions of the ventilated CFC-waters than Expt. 1. The experiments clearly highlight the sensitivity of the southern ocean surface water ventilation to the distribution and thickness of the simulated mixed layer. It is argued that inclusion of CFCs in coupled climate models could be used as a test-bed for evaluating the decadal-scale ocean uptake of heat and CO2.

关键词： chlorofluorocarbons CFC-11 diapycnal mixing ocean modelling ocean ventilation southern ocean transient tracers

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Differences in nitrous oxide distribution patterns between the Bering Sea basin and Indian Sector of the southern ocean

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Acta oceanologica Sinica 2014年第6期33卷 9-19页

作者： CHEN Liqi ZHANG Jiexia ZHAN Liyang LI Yuhong SUN Heng College of ocean and Earth Science Xiamen University Key Laboratory of Global Change and Marine-Atmospheric Chemistry of State oceanic Administration Third Institute of OceanographyState Oceanic Administration

Nitrous oxide （N2O） distribution patterns in the Bering Sea basin （BSB） and Indian Sector of the southern ocean （ISSO） were described and compared. In both sites, the waters were divided into four layers： surface layer, subsurface layer, N2O maximum layer, and deep water. Simulations were made to find out the most important factors that regulate the N2O distribution patterns in different layers of both sites. The results showed that in the surface water, N2O was more understaturated in the ISSO than the BSB. This phenom- enon in the surface water of ISSO may result from ice melt water intrusion and northeastward transport of the Antarctic surface water. Results of the rough estimation of air-sea fluxes during the expedition were （-0.34±0.07）-（-0.64±0.13） μmol/（m2·d） and （-1.47±0.42）-（-1.77±0.51） μmol/（m-2·d） for the BSB and the ISSO, respectively. Strongly stratified surface layer and temperature minimum layer restricted exchange across the thermocline. The N2O maximum existed in higher concentration and deeper in the BSB than the ISSO, but their contribution to the upper layer by eddy diffusions was negligible. In deep waters, a concentration difference of 5 nmol/L N2O between these two sites was found, which suggested that N2O production occurred during thermohaline circulation. N2O may be a useful tracer to study important large-scale hydrographic processes.

关键词： nitrous oxide Bering Sea basin southern ocean distribution

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Study on low-temperature lipase of psychrophilic bacterium 2-5-10-1 isolated from deep sea of southern ocean

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Acta oceanologica Sinica 2003年第4期22卷 643-649页

作者： Lin Xuezheng1,Yang Xiuxia2,Bian Ji1,Huang Xiaohang1 1. First Institute of oceanography,State oceanic Administration,Qingdao 266061,China 2. Fishery College, ocean University of China,Qingdao 266003,China First Institute of oceanography State Oceanic Administration Qingdao 266061 China Fishery College Ocean University of China Qingdao 266003 China

A strain of psychrophilic bacterium, 2-5-10-1, which produces low-temperature lipase, is isolated from the deep sea of Prydz Bay in southern ocean. The highest lipase secretion of this strain is observed at 5 degreesC and this temperature is also for optimal growth. Tween 80 and olive oil enhance secretion of lipase. The optimal temperature and pH for lipase activity are 35 degreesC and 7.5 degreesC respectively. At 0degreesC, the lipase still has 37% relative enzyme activity. The lipase shows high thermolability, more than 50% activity lost after incubation at 60 degreesC for 15 min. EDTA has no effect on lipase activity, indicating the lipase activity is independent of divalent cation. In contrast, the lipase activity is inhibited drastically by Cu2+ and Zn2+.

关键词： southern ocean deep sea psychrophilic bacteria low-temperature lipase

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Assessment of the southern ocean Sea Surface Temperature Biases in CMIP5 and CMIP6 Models

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Journal of ocean University of China 2024年第5期23卷 1135-1150页

作者： GAO Zhen ZHAO Shichang LIU Qinyu LONG Shang-Min SUN Shantong Key Laboratory of Marine Hazards Forecasting Ministry of Natural ResourcesHohai UniversityNanjing 210098China College of oceanography Hohai UniversityNanjing 210098China Laoshan Laboratory Qingdao 266237China Physical oceanography Laboratory Ocean University of ChinaQingdao 266100China

This work evaluates the performances of climate models in simulating the southern ocean(SO)sea surface temperature(SST)by a large ensemble from phases 5 and 6 of the Coupled Model Intercomparison Project(CMIP5 and CMIP6).By combining models from the same community sharing highly similar SO SST biases and eliminating the effect of global-mean biases on local SST biases,the results reveal that the ensemble-mean SO SST bias at 70°-30°S decreases from 0.38℃ in CMIP5 to 0.28℃ in CMIP6,together with increased intermodel *** dominant mode of the intermodel variations in the zonal-mean SST biases is characterized as a meridional uniform warm bias pattern,explaining 79.1% of the intermodel variance and exhibiting positive principal values for most *** ocean mixed layer heat budget further demonstrates that the SST biases at 70°-50°S primarily result from the excessive summertime heating effect from surface net heat *** biases in surface net heat flux south of 50°S are largely impacted by surface shortwave radiation from cloud and clear sky components at different *** of 50°S,the underestimated westerlies reduce the northward Ekman transport and hence northward cold advection in models,leading to warm SST biases *** addition,the westerly biases are primarily traced back to the atmosphere-alone model simulations forced by the observed SST and sea *** results disclose the thermal origin at the high latitude and dynamical origin at the low latitude of the SO SST biases and underscore the significance of the deficiencies of atmospheric models in producing the SO SST biases.

关键词： southern ocean CMIP5 CMIP6 SST biases surface heat flux westerlies atmospheric biases cloud simulation

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Influence of mixed layer depth on chlorophyll-a concentration in the southern ocean

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Acta oceanologica Sinica 2024年第10期43卷 16-32页

作者： Yuxin Shi Hailong Liu Quanan Zheng School of oceanography Shanghai Jiao Tong UniversityShanghai 200240China Yunnan Key Laboratory of Meteorological Disasters and Climate Resources in the Greater Mekong Subregion Yunnan UniversityKunming 600650China Department of Atmospheric and oceanic Science University of Maryland at College ParkCollege Park 20742USA

The element iron limitation is one of the crucial factors contributing to high nutrient low chlorophyll in the southern ocean(SO).Mixed layer dynamics regulate the availability of iron to *** this paper,we investigate the influence of surface iron supplementation triggered by the mixed layer depth(MLD)variation on chlorophyll-a(Chl-a)concentration in the SO on seasonal and interannual *** analysis is based on the Biogeochemical southern ocean State Estimate for the period from 2013 to *** provide a comprehensive and systematic mapping of the regions within the SO,where Chl-a is affected by iron input related to MLD *** relationship between the MLD and the Chl-a varies with the latitude on the seasonal time *** the MLD and sea ice melting affect the distribution of *** the interannual scale,iron supply due to MLD deepening occurs primarily north of 60°*** advection-induced entrainment enhances the surface iron input during the austral summer,which favors Chl-a *** addition to the MLD,the melting of sea ice and cooling of the sea surface can also alter iron input and subsequently affect Chl-a distribution in the austral *** the austral winter,entrainment can boost iron stocks,stimulating a subsequent spring increase of Chl-a in the ***,sea surface temperature declines during the austral winter,promoting an increased iron supply and creating favorable conditions for the subsequent spring Chl-a increase in the SO.

关键词： mixed layer depth entrainment chlorophyll-a concentration southern ocean

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Characteristics of cyclone climatology and variability in the southern ocean

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Acta oceanologica Sinica 2016年第7期35卷 59-67页

作者： WEI Lixin QIN Ting Key Laboratory of Research on Marine Hazards Forecasting National Marine Environmental Forecasting CenterState Oceanic Administration

A new climatology of cyclones in the southern ocean is generated by applying an automated cyclone detection and tracking algorithm （developed by Hodges at the Reading University） for an improved and relatively high- resolution European Centre for Medium-Range Weather Forecasts atmospheric reanalysis during 1979-2013. A validation shows that identified cyclone tracks are in good agreement with a available analyzed cyclone product. The climatological characteristics of the southern ocean cyclones are then analyzed, including track, number, density, intensity, deepening rate and explosive events. An analysis shows that the number of cyclones in the southern ocean has increased for 1979-2013, but only statistically significant in summer. Coincident with the circumpolar trough, a single high-density band of cyclones is observed in 55^-67~S, and cyclone density has generally increased in north of this band for 1979-2013, except summer. The intensity of up to 70% cyclones in the southern ocean is less than 980 hPa, and only a few cyclones with pressure less than 920 hPa are detected for 1979-2013. Further analysis shows that a high frequency of explosive cyclones is located in the band of 45^-55~S, and the Atlantic ocean sector has much higher frequent occurrence of the explosive cyclones than that in the Pacific ocean sector. Additionally, the relationship between cyclone activities in the southern ocean and the southern Annular Mode is discussed.

关键词： southern ocean cyclones automated detection and tracking algorithm southern Annular Mode

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Responses of the southern ocean mixed layer depth to the eastern and central Pacific El Niño events during austral winter

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Acta oceanologica Sinica 2024年第7期43卷 1-14页

作者： Yuxin Shi Hailong Liu Xidong Wang Quanan Zheng School of oceanography Shanghai Jiao Tong UniversityShanghai 200240China Yunnan Key Laboratory of Meteorological Disasters and Climate Resources in the Greater Mekong Subregion Yunnan UniversityKunming 600650China College of oceanography Hohai UniversityNanjing 210098China Department of Atmospheric and oceanic Science University of Maryland at College ParkCollege Park 20742USA

Based on the ocean Reanalysis System version 5(ORAS5)and the fifth-generation reanalysis datasets derived from European Centre for Medium-Range Weather Forecasts(ERA5),we investigate the different impacts of the central Pacific(CP)El Niño and the eastern Pacific(EP)El Niño on the southern ocean(SO)mixed layer depth(MLD)during austral *** MLD response to the EP El Niño shows a dipole pattern in the South Pacific,namely the MLD dipole,which is the leading El Niño-induced MLD variability in the *** tropical Pacific warm sea surface temperature anomaly(SSTA)signal associated with the EP El Niño excites a Rossby wave train propagating southeastward and then enhances the Amundsen Sea low(ASL).This results in an anomalous cyclone over the Amundsen *** a result,the anomalous southerly wind to the west of this anomalous cyclone advects colder and drier air into the southeast of New Zealand,leading to surface cooling through less total surface heat flux,especially surface sensible heat(SH)flux and latent heat(LH)flux,and thus contributing to the mix layer(ML)*** east of the anomalous cyclone brings warmer and wetter air to the southwest of Chile,but the total heat flux anomaly shows no significant *** warm air promotes the sea ice melting and maintains fresh water,which strengthens *** results in a shallower *** the CP El Niño,the response of MLD shows a separate negative MLD anomaly center in the central South *** Rossby wave train triggered by the warm SSTA in the central Pacific ocean spreads to the Amundsen Sea,which weakens the ***,the anomalous anticyclone dominates the Amundsen ***,the anomalous northerly wind to the west of anomalous anticyclone advects warmer and wetter air into the central and southern Pacific,causing surface warming through increased SH,LH,and longwave radiation flux,and thus contributing to the ML ***,to the east of the anomalous anticyclone,there is n

关键词： southern ocean mixed layer depth Central Pacific El Niño Eastern Pacific El Niño Rossby wave train

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