Summer freshwater content variability of the upper ocean in the Canada Basin during recent sea ice rapid retreat

Freshwater content （FWC） in the Arctic Ocean has changed rapidly in recent years, in response to significant decreases in sea ice extent. Research on freshwater content variability in the Canada Basin, the main storage area of fresh water is very important to understand the input-output freshwater in the Arctic Ocean. The FWC in the Canada Basin was calculated using data from the Chinese National Arctic Research Expeditions of 2003 and 2008, and from expeditions of the Canadian icebreaker Louis S. St-Laurent （LSSL） from 2004 to 2007. Results show that the upper ocean in the Canada Basin became continuously fresher from 2003 to 2008, except during 2006. The FWC increased at a rate of more than 1 m.a-1, and the maximum increase, 7 m, was in the central basin compared between 2003 and 2008. Variability of the FWC was almost entirely limited to the layer above the winter Bering Sea Water （wBSW）, below which the FWC remained around 3 m during the study period. Contributors to the FWC increase are generally considered to be net precipitation, runoff changes, Pacific water inflow through the Bering Strait, sea ice extent, and the Arctic Oscillation（AO）. However, we determined that the first three contributors did not have apparent impact on the FWC changes. Therefore, this paper focuses on analysis of the latter two factors and the results indicate that they were the major contributors to the FWC variability in the basin.

Characteristics of hydrogen/oxygen isotopes in water masses and implications for spatial distribution of freshwater in the Amundsen Sea,Southern Ocean

Antarctica’s marginal seas are of great importance to atmosphere-ocean-ice interactions and are sensitive to global climate change.Multiple factors account for the freshwater budget in these regions,including glacier melting,seasonal formation/decay of sea ice,and precipitation.Hydrogen(H)and oxygen(O)isotopes represent useful proxies for determining the distribution and migration of water masses.We analyzed the H and O isotopic compositions of 190 seawater samples collected from the Amundsen Sea during the 34th Chinese Antarctic Research Expedition in 2017/2018.The upper-oceanic structure(<400 m)and freshwater(meteoric water and sea ice melt)distribution in the Amundsen Sea were identified based on conductivity-temperature-depth data and the H and O isotopic composition.Antarctic Surface Water,characterized as cold and fresh with low H and O isotopic ratios,was found distributed mainly in the upper~150 m between the Antarctic Slope Front and Polar Front,where it had been affected considerably by upwelled Upper Circumpolar Deep Water(UCDW)between 68°S and 71°S.A three-endmember(meteoric water,sea ice melt,and Circumpolar Deep Water)mixing model indicated that waters with relatively high proportions(>3%)of freshwater generally lie in the upper~50 m and extend from Antarctica to~65°S in the meridional direction(anomalously low freshwater proportion occurred between 68°S and 71°S).Winter Water mainly occupied the layer between 50 and 150 m south of 71°S in the western Amundsen Sea.The water structure and spatial distribution of freshwater in the upper Amundsen Sea were found influenced mainly by the rates of basal and surficial melting of ice shelves,seasonal alternation of sea ice melt/formation,wind forcing,and regional bathymetry.Owing to the distance between heavy sea ice boundary(HSIB)and ice shelves is much shorter in the western HSIB than the east HSIB,the western part of the heavy sea ice boundary includes a higher proportion of freshwater than the eastern region.This study,which highlighted the distribution and extent of freshwater derived from ice(ice shelves and sea ice)melt,provides important evidence that the offshore drift pathway of cold and fresh Antarctic continental shelf water is likely interrupted by upwelled UCDW in the Amundsen Sea.

Modulation of El Nio-Southern Oscillation by Freshwater Flux and Salinity Variability in the Tropical Pacific

The E1 Nifio-Southern Oscillation （ENSO） is emphasized the roles of wind stress and heat flux environmental forcing to the ocean; its effect and modulated by many factors; most previous studies have in the tropical Pacific. Freshwater flux （FWF） is another the related ocean salinity variability in the ENSO region have been of increased interest recently. Currently, accurate quantifications of the FWF roles in the climate remain challenging; the related observations and coupled ocean-atmosphere modeling involve large elements of uncertainty. In this study, we utilized satellite-based data to represent FWF-induced feedback in the tropical Pacific climate system; we then incorporated these data into a hybrid coupled ocean-atmosphere model （HCM） to quantify its effects on ENSO. A new mechanism was revealed by which interannual FWF forcing modulates ENSO in a significant way. As a direct forcing, FWF exerts a significant influence on the ocean through sea surface salinity （SSS） and buoyancy flux （QB） in the western-central tropical Pacific. The SSS perturbations directly induced by ENSO-related interannual FWF variability affect the stability and mixing in the upper ocean. At the same time, the ENSO-induced FWF has a compensating effect on heat flux, acting to reduce interannual Qs variability during ENSO cycles. These FWF-induced processes in the ocean tend to modulate the vertical mixing and entrainment in the upper ocean, enhancing cooling during La Nifia and enhancing warming during E1 Nifio, respectively. The interannual FWF forcing-induced positive feedback acts to enhance ENSO amplitude and lengthen its time scales in the tropical Pacific coupled climate system.

Variation of freshwater components in the Canada Basin during 1967–2010

As a conservative tracer, oxygen isotopes in seawater are widely used for water mass analysis, along with temperature and salinity. In this study, seawater oxygen-18 datasets in the Canada Basin during 1967-2010 were obtained from the four cruises of the Chinese National Arctic Research Expedition （1999, 2003, 2008, and 2010） and the NASA database. Fractions of sea ice meltwater and river runoffwere determined from the salinity-5180 system. Our results showed that the river runoff decreased from the south to the north in the Canada Basin. The enhanced amount of river runoff observed in the southern Canada Basin may originate from the Mackenzie River, transported by the Beaufort Gyre. The river runoff component showed maximum fractions during 1967-1969, 1978-1979, 1984-1985, 1993-1994, and 2008-2010, indicating the refresh time of the river runoffwas 5.0-16.0 a in the Canada Basin. The temporal variation of the river runoffwas related to the change of the Arctic Oscillation （AO） index, suggesting the freshwater stored in the Canada Basin was affected by surface sea ice drift and water mass movement driven by atmospheric circulation.

Accumulation of freshwater in the permanent ice zone of the Canada Basin during summer 2008

A combination of 5180 and salinity data was employed to explore the freshwater balance in the Canada Basin in summer 2008. The Arctic river water and Pacific river water were quantitatively distinguished by using different saline end-members. The fractions of total river water, including the Arctic and Pacific river water, were high in the upper 50 m and decreased with depth as well as increasing latitude. In contrast, the fraction of Pacific river water increased gradually with depth but decreased toward north. The inventory of total river water in the Canada Basin was higher than other arctic seas, indicating that Canada Basin was a main storage region for river water in the Arctic Ocean. The fraction of Arctic river water was higher than Pacific river water in the upper 50 m while the opposite was true below 50 m. As a result, the inventories of Pacific river water were higher than those of Arctic river water, demonstrating that the Pacific inflow through the Bering Strait is the main source of freshwater in the Canada Basin. Both the river water and sea-ice melted water in the permanent ice zone were more abundant than those in the region with sea-ice just melted. The fractions of total river water, Arctic river water, Pacific river water increased northward to the north of 82°N, indicating an additional source of river water in the permanent ice zone of the northern Canada Basin. A possible reason for the extra river water in the permanent ice zone is the lateral advection of shelf waters by the Trans-Polar Drift. The penetration depth of sea-ice melted waters was less than 30 m in the southern Canada Basin, while it extended to 125 m in the northern Canada Basin. The inventory of sea- ice melted water suggested that sea-ice melted waters were also accumulated in the permanent ice zone, attributing to the trap of earlier melted waters in the permanent ice zone via the Beaufort Gyre.

Observed Relationship between Surface Freshwater Flux and Salinity in The North Indian Ocean

Using 10-year (2001 10) monthly evaporation, precipitation, and sea surface salinity (SSS) datasets, the relationship between local freshwater flux and SSS in the north Indian Ocean (NIO) is evaluated quantitatively. The results suggest a highly positive linear correlation between freshwater flux and SSS in the Arabian Sea (correlation coefficient, R=0.74) and the western equatorial Indian Ocean (R=0.73), whereas the linear relationships are relatively weaker in the Bay of Bengal (R=0.50) and the eastern equatorial Indian Ocean (R=0.40). Additionally, the interannual variations of freshwater flux and SSS and their mutual relationship are investigated in four sub- regions for pre-monsoon, monsoon, and post-monsoon seasons separately. The satellite retrievals of SSS from the Soil Moisture and Ocean Salinity (SMOS) and Aquarius missions can provide continuous and consistent SSS fields for a better understanding of its variability and the differences between the freshwater flux and SSS signals, which are commonly thought to be linearly related.

Summertime freshwater fractions in the surface water of the western Arctic Ocean evaluated from total alkalinity

As a quasi-conservative tracer, measures of total alkalinity （TA） can be utilized to trace the relative fractions of freshwater and seawater. In this study, based on the TA and related data collected during the third Chinese National Arctic Research Expedition （JulySeptember 2008, 3rd CHINARE-Arctic） and the fourth Chinese National Arctic Research Expedition （JulySeptember 2010, 4th CH1NARE-Arctic）, fractions of sea-ice meltwater, river runoff, and seawater within the surface water of the western Arctic Ocean were determined using salinil~~ and TA relationships. The largest fraction of seeL-ice meltwater was found around 75~N within the Canada Basin during both surveys, which is located at the ice edge. Generally, it was found that the frac- tion of river runoff was less than that of sea-ice meltwater. The river runoff, composed mainly of contributions from the Yukon River carried by Bering inflow water and the Mackenzie River, was influenced by the currents, leading to two peak areas of its fraction. Our results show that the dilution effect of freshwater carried by Bering inflow water during the 3rd CH1NARE-Arctic in 2008 expedition period may be stronger than that during the 4th CH1NARE-Arctic in 2010 expedition period. The peak area of sea-ice meltwater fraction during the 4th CH1NARE-Arctic was different from that of the 3rd CHINAR-E-Arctic, corresponding to their sea-ice condition.

南太平洋海表面盐度最大值年代际变异机理研究

已有研究表明南太平洋海表面盐度最大值存在明显的年代际变化,表现为盐度位置的变化,而对于调控该年代际变化的机制尚不清楚。利用1999—2022年的盐度数据,再现了盐度最大值位置的东北—西南向摆动,即2005年和2016年盐度位置偏东北,2011年和2022年偏西南。在此基础上,利用盐度收支分析与1.5层约化重力模式两种方法研究了1999—2022年南太平洋海表面盐度最大值的年代际变化机理,评估了淡水强迫、水平平流、垂直夹卷、水平扩散这4种因素的相对贡献。结果表明:水平平流、淡水强迫的平均贡献最大,前者是驱动南太平洋海表面盐度最大值位置的年代际变化的关键因素,而淡水强迫项主要是引起盐度量值大小的年代际变化;垂直夹卷项与水平扩散项在盐度最大值年代际变化中的贡献可能较小。

硫酸盐和氯盐对海水海砂混凝土早期抗压强度的影响

对比研究了淡水河砂混凝土(SC)和海水海砂混凝土(SSC)的抗硫酸盐侵蚀和抗氯离子侵蚀性能。配制了不同水胶比的混凝土,经不同硫酸盐溶液浸泡后,测定了其早期抗压强度和抗压耐蚀系数;经5%NaCl溶液浸泡后,测定了其抗氯离子侵蚀性能。结果表明:硫酸盐溶液或Na Cl溶液浸泡有利于提高SSC的3 d抗压强度,但对7 d抗压强度会产生不利影响;SC的抗硫酸盐和抗氯离子侵蚀能力随着龄期的增长要优于SSC。水胶比对SC和SSC的抗压强度影响明显,水胶比为0.45时混凝土的抗压强度要高于0.50水胶比下的抗压强度;高水胶比时SSC的抗硫酸盐侵蚀和抗氯离子侵蚀能力优于低水胶比的。

Historic changes in flux of matter and nutrient budgets in the Bohai Sea

Over the past four periods （ 1959--1960, 1982--1983, 1992--1993, and 1998--1999）, the ecosystem of the Bohai Sea changed due to both a significant decrease of river water discharge from the Huanghe River and a reduction of precipitation. The shifts in nutrient chemistry could result in changes in the phytoplankton composition with an increased potential for non-diatom algal blooms. Simple box model was used to estimate the water - mass balance and nutrient budgets for the Bohai Sea. Water budgets indicate that the residual flow changed from out of the Bohai Sea before 1993, but became inflow to the Bohai Sea after then. The nutrient budgets developed indicate that the Bohai Sea was a sink for nutrients except for phosphate in 1959--1960 and 1982-- 1983 and for silicate in 1982--1983. Net water flow transports nutrients out of the Bohai Sea in 1959--1960, 1982--1983 and 1992--1993, but into the sea in 1998--1999 due to climate changes, such as precipitation and subsequent freshwater discharge. The residual fluxes of nutrients are minor relative to atmospheric deposition and riverine inputs. Conversions of phosphate values to carbon by stoichiometric ratios were used to predict that the system was net heterotrophic before 1982--1983 and net autotrophic after then. Nutrient budgets can explain the change of nutrient concentrations in the Bohai Sea except nitrates, which should include the surface runoff.

Validation and application of soil moisture active passive sea surface salinity observation over the Changjiang River Estuary

Using sea surface salinity(SSS)observation from the soil moisture active passive(SMAP)mission,we analyzed the spatial distribution and seasonal variation of SSS around Changjiang River(Yangtze River)Estuary for the period of September 2015 to August 2018.First,we found that the SSS from SMAP is more accurate than soil moisture and ocean salinity(SMOS)mission observation when comparing with the in situ observations.Then,the SSS signature of the Changjiang River freshwater was analyzed using SMAP data and the river discharge data from the Datong hydrological station.The results show that the SSS around the Changjiang River Estuary is significantly lower than that of the open ocean,and shows significant seasonal variation.The minimum value of SSS appears in July and maximum SSS in December.The root mean square difference of daily SSS between SMAP observation and in situ observation is around 3 in both summer and winter,which is much lower than the annual range of SSS variation.In summer,the diffusion direction of the Changjiang River freshwater depicted by SSS from SMAP is consistent with the path of freshwater from in situ observation,suggesting that SMAP observation may be used in coastal seas in monitoring the diffusion and advection of freshwater discharge.

Subtropical sea surface salinity maxima in the South Indian Ocean

Subtropical sea surface salinity(SSS)maximum is formed in the subtropical South Indian Ocean(SIO)by excessive evaporation over precipitation and serves as the primary salt source of the SIO.Spaceborne SSS measurements by Aquarius satellite during September 2011-May 2015 detect three disconnected SSS maximum regions(>35.6)in the eastern(105°E-115°E,38°S-28°S),central(60°E-100°E,35°S-25°S),and western(25°E-40°E,38°S-20°S)parts of the subtropical SIO,respectively.Such structure is however not seen in gridded Argo data.Analysis of Argo profile data confirms the existence of the eastern maximum patch and also reveals SSS overestimations of Aquarius near the western and eastern boundaries.Although subjected to large uncertainties,a mixed-layer budget analysis is employed to explain the seasonal cycle of SSS.The eastern and central regions reach the highest salinity in February-March and lowest salinity in August-September,which can be well explained by surface freshwater forcing(SFF)term.SFF is however not controlled by evaporation(E)or precipitation(P).Instead,the large seasonal undulations of mixed layer depth(MLD)is the key factor.The shallow(deep)MLD in austral summer(winter)amplifies(attenuates)the forcing effect of local positive E-P and causes SSS rising(decreasing).Ocean dynamics also play a role.Particularly,activity of mesoscale eddies is a critical factor regulating SSS variability in the eastern and western regions.

Comparisons of Several Evaporation/Precipitation Datasets for the Bohai Sea Based on Salinity Simulation

Evaporation （E） rate and precipitation （P） rate are two significant meteorological elements required in the ocean baro- clinic modeling as external forcings. However, there are some uncertainties in the currently used E/P rates datasets, especially in terms of the data quality. In this study, we collected E/P rates data from ERA-40, NCEP/NCAR Reanalysis, HOAPS for the Bohai Sea and nine routine stations around Laizhou Bay, and made comparisons among them. It was found that the differences in E/P rates between land and sea are remarkable, which was due to the difference in underlying surfaces. Therefore, the traditional way of using E/P rates acquired on land directly at sea is not correct. Since no final conclusion has been reached concerning the net water transport between the Bohai Sea and the Yellow Sea, it is unfeasible to judge the adequacy of the four kinds of data by using the water budget equation. However, the E/P rates at ERA-40 sea points were considered to he the optimal in terms of temporal/spatial coverage and resolution for the hindcast of salinity variation in the Bohai Sea. Besides, using the 3-D hydrodynamic model HAMSOM （HAMburg Shelf Ocean Model）, we performed numerical experiments with different E/P datasets and found that the E/P rates at sea points from ERA-40 dataset are better than those from NCEP/NCAR Reanalysis dataset. If NCEP/NCAR Reanalysis E/P rates are to be used, they need to be adjusted and tested prior to simulation so that more close-to-reality salinity values can be reproduced.

The coupling procedure of air-sea freshwater exchange in climate system models

A coupling procedure of air-sea freshwater exchange in climate system models is reported in this note. The first stage of the procedure is to force OGCM to equilibrium under strong restoring surface condition on salinity, then increase the relaxing coefficient and get another steady state. The second stage is to switch the forcing on salinity from the weak restoring condition to the flux condition, and then finish a long-term spinning-up integration. After finishing these OGCM spinning-up stages, the last stage is to couple the OGCM with an active atmosphere, i.e. AGCM. Verification with the Global-Ocean-Atmosphere-Land-System model developed at the State Key Laboratory of Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) shows that the preferred procedure is successful in including the air-sea freshwater exchange process.

湖区桩基极限挤压冰力计算研究

现行JTS 144-1—2010《港口工程荷载规范》提出了海冰和河冰的极限挤压冰力计算公式,但是规范中没有针对大面积淡水湖区的计算公式。基于实际工程,通过对比分析国内相关行业规范针对极限挤压冰力的计算公式,并结合数值模型实验得出,利用《港口工程荷载规范》的河冰公式计算得出的极限挤压冰力偏小,而海冰公式计算得出的极限挤压冰力偏大,根据现行JTG D60—2015《公路桥涵设计通用规范》得出的极限挤压冰力与数学模型模拟值基本一致。因此对于大面积淡水湖区极限挤压冰力的计算可以参考《公路桥涵设计通用规范》中的计算公式。该研究为计算大面积淡水湖区极限挤压冰力提供一定的依据,为修订规范时提供参考。

热带太平洋海表二氧化碳分压的时空变化特征及其与物理场间的联系

为研究赤道太平洋海表二氧化碳分压(pCO_(2)^(sw))年际变化的机制,基于中科院海洋所宋金明研究团队于2021年发布的中国首套全球海表二氧化碳分压数据产品,使用相关性分析、经验正交函数(empirical orthogonal function, EOF)分析和奇异值分解(singular value decomposition, SVD)等方法,研究了2005~2019年赤道太平洋pCO_(2)^(sw)气候态分布及其去趋势后的年际异常的时空演变特征;结合pCO_(2)^(sw)与多种参数的相关性和厄尔尼诺-南方涛动(El Ni?o-Southern Oscillation, ENSO)过程探讨了赤道中西太平洋pCO_(2)^(sw)年际异常中心形成的原因。研究结果显示,热带太平洋pCO_(2)^(sw)季节变化、年际异常及其EOF第一模态特征向量沿赤道均出现两个中心,其中一个在赤道中西太平洋日界线附近,另一个在赤道中东太平洋120°W附近;且不同季节、不同ENSO相位时期前者的位置会沿赤道有东西向移动。赤道太平洋pCO_(2)^(sw)年际异常的EOF第一模态时间系数与Ni?o 3.4海表温度指数呈极强的负相关性(二者间的相关系数为-0.853);赤道中西太平洋pCO_(2)^(sw)年际异常与海表温度、纬向风速、虚拟盐通量和降水等异常均呈负相关,而与叶绿素浓度、盐度、位势密度和混合层深度等异常呈正相关,同时也与经向流速异常有关。据此,提出一种关于ENSO调制赤道中西太平洋pCO_(2)^(sw)年际变率的物理机制:当ElNi?o发生时,热带太平洋信风减弱,赤道西太平洋出现西风异常,主要降水带和沃克环流的上升支沿赤道东移,使得赤道中西太平洋降水增多(虚拟盐通量、进入海洋表层的淡水通量增加等),导致盐度降低、上层海洋层结增强和垂向混合减弱,使得次表层富含二氧化碳的冷水上涌减少,导致pCO_(2)^(sw)变小。

气相色谱法测定鱼油中的二十碳五烯酸和二十二碳六烯酸及其品质评价

目的建立气相色谱法测定鱼油中的二十碳五烯酸(eicosapentaenoic acid,EPA)和二十二碳六烯酸(docosahexaenoic acid,DHA),并对不同原料来源鱼油的品质进行分析与评价。方法对GB 5009.168—2016《食品安全国家标准食品中脂肪酸的测定》第一法内标法中的水解提取法、色谱条件和结果分析方法等分别进行优化,然后进行方法验证。应用优化后的方法检测实际样品鱼油中EPA与DHA的含量,并进行品质评价。结果EPA和DHA分别在5.57~278.50μg/mL和6.95~347.50μg/mL范围内线性关系良好,精密度、重复性、稳定性均符合实验室质量控制规范、化学分析方法验证确认和内部质量控制要求,其加标回收率均在95%~105%之间,相对标准偏差均小于2%。通过对不同来源鱼油中的EPA和DHA含量进行分析,结果显示市场所售的鱼油存在假冒伪劣现象。结论该方法准确、灵敏,适用于鱼油中EPA和DHA含量的测定。市场所售的鱼油产品优劣掺杂,此方法可以作为鱼油品质评价与质量控制的科学依据。

海气耦合气候模式对大气中水汽输送、辐散辐合与海气间水通量交换的模拟

基于ECMWF再分析结果对LASG第三代全球海洋- 大气- 陆地耦合系统模式 （GOALS）的两个版本和第四代耦合气候模式初始版（FGCM—0） 所模拟的大气水汽输送 与辐散辐合特征、海气间水通量交换，进行了评估分析。结果表明：（1）对垂直积分的水汽 通量场的流函数及其对应的无辐散水汽通量矢量的模拟，三个耦合模式都能够较为合理地再 现副热带大洋的涡旋结构、中纬度西风带的东向水汽输送。赤道东风带的西向水汽输送和东 亚夏季风水汽输送等行星尺度特征及其季节变化，只是GOALS的涡旋位置。FGCM—0的 涡旋中心强度，较之实际略有偏差。（2） 反映在垂直积分的水汽通量场的势函数和对应的无 旋水汽矢量上，对南北半球副热带大洋水汽辐散区、热带辐合带（ITCZ）、东亚夏季风区强 烈的水汽辐合特征等的模拟，FGCM—0的结果相对合理。GOALS的热带辐合中心过于集 中在印度尼西亚群岛附近，东亚夏季风水汽辐合中心偏南。（3）关于海气水通量交换， FGCM—0较为理想地再现了副热带的净蒸发、ITCZ和中高纬度的净降水特征以及夏季 ITCZ的季节性北移，但对南太平洋辐合带（SPCZ）、副热带南大西洋的净蒸发特点，以及 阿拉伯海和孟加拉湾季节变化的差异，模拟结果不理想。FGCM—0在模拟SPCZ上的偏 差。

波浪能海水淡化的应用研究

简要介绍了“十五”期间在广东省汕尾市研建的波浪能海水淡化系统的组成和工作原理。为了验证波浪能海水淡化装置运行的实用性和可靠性,在国内外波浪能海水淡化研究的基础上,对汕尾波浪能海水淡化装置进行了不同操作压力情况下的试验研究。研究结果表明,随着高压海水压力的升高,产出淡水量会明显增加,淡水质量提高,装置产出淡水的能耗较低。

阿拉伯海东南海域盐度收支的季节变化

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