Extracellular enzymatic activities of cold-adapted bacteria from polar oceans and effect of temperature and salinity on cell growth

The potential of 324 bacteria isolated from different habitats in polar oceans to produce a variety of extracellular enzymatic activities at low temperature was investigated. By plate assay, lipase, protease, amylase, gelatinase, agarase, chitinase or cellulase were detected. Lipases were generally present by bacteria living in polar oceans. Protease-producing bacteria held the second highest proportion in culturable isolates. Strains producing amylase kept a relative stable proportion of around 30% in different polar marine habitats. All 50 Arctic sea-ice bacteria producing proteases were cold-adapted strains, however, only 20% were psychrophilic. 98% of them could grow at 3% NaCl, and 56% could grow without NaCl. On the other hand, 98% of these sea-ice bacteria produced extracellular proteases with optimum temperature at or higher than 35℃, well above the upper temperature limit of cell growth. Extracellular enzymes including amylase, agarase, cellulase and lipase released by bacteria from seawater or sediment in polar oceans, most expressed maximum activities between 25 and 35℃. Among extracellular enzymes released by bacterial strain BSw20308, protease expressed maximum activity at 40℃, higher than 35℃ of polysaccharide hydrolases and 25℃ of lipase.

Observation and simulation of the diffuse attenuation coefficient of downwelling irradiance in the Polar Ocean

The three-stream radiation transfer model is used to investigate the fluctuation in the underwater diffuse attenuation coefficient of downwelling irradiance in the polar ocean with a high solar zenith angle and different direct radiation proportions.First,the applicability of the three-stream radiation model in the polar region is validated by using 18 in situ observation data from September to October 2009 in the Beaufort Sea.Statistics show that in the absence of sea ice,the average relative errors between the simulation and observation values for 490 nm downwelling irradiance (E_(d)(490)) and its diffuse attenuation coefficient (K_(d)(490)) are 7.04%and 9.88%,respectively.At the stations surrounded by sea ice,the radiation is relatively small due to ice blocking,and the average relative errors simulated by the model reach 15.89%and 15.55%,respectively.Second,simulations with different chlorophyll concentrations and different proportions of direct radiation reveal that a high solar zenith angle has a greater impact on K_(d)(490) in the surface water.K_(d)(490) is less affected by the light field (affected by the solar zenith angle and the proportion of direct radiation) at depths greater than 30 m,and meets the linear relationship with the inherent optical parameters(the sum of the absorption coefficient and backscattering coefficient).The surface K_(d)(490) is still consistent with that at a depth of more than 50 meters under a high solar zenith angle,implying that the surface K_(d)(490) can also be considered as an inherent optical parameter at a high solar zenith angle (greater than 60 degrees).The relative error of obtaining surface K_(d)(490) by using the linear relationship at the 50 m layer is found to be less than 8%in the seawater with chlorophyll concentration greater than0.05 mg m^(-3).The effect of the solar zenith angle and proportion of direct radiation can be ignored when measuring the diffuse attenuation coefficient in the polar region.Finally,the model can correct the ice-induced fluctuation in downward irradiance,allowing for optical research of seawater beneath the ice in the polar ocean.

Effects of Ocean Particles on the Upwelling Radiance and Polarized Radiance in the Atmosphere–Ocean System

Based on a vector radiative transfer model of the atmosphere–ocean system,the influence of oceanic components on radiation processes,including polarization effects,was investigated in the wavelength region ranging from 0.380 to 0.865 μm.The components considered were phytoplankton,inorganic suspended material（sediment）,and colored,dissolved organic matter.Due to their important roles in oceanic radiation processes,the sensitivity of the bidirectional reflectance to the rough ocean surface,represented by the wind velocity 10 m above the ocean surface,and aerosol,were taken into account.The results demonstrated that both radiance and polarized radiance just below the ocean surface were sensitive to the change of the concentrations of the considered components,while the dependence of polarized radiance on the observation geometry was more sensitive than radiance.Significant differences in the specular plane existed between the impacts of the phytoplankton and sediment on the degree of polarization just above the ocean surface at 670 nm.At the top of the atmosphere（TOA）,polarization was relatively insensitive to changing concentrations of ocean particles at longer wavelengths.Furthermore,the radiance at the TOA in the solar plane was more sensitive to the aerosol optical thickness than wind velocity.In contrast,wind velocity strongly influenced the radiance at the TOA in the sun glint region,while the polarization degree showed less dependence in that region.Finally,a nonlinear optimal inversion method was proposed to simultaneously retrieve the aerosol and wind velocity using radiance measurement.

Separation of ocean features from multifrequency full-polarization SAR imagery

Different ocean features usually appear in synthetic aperture radar (SAR) images simultaneously. This makes the image complicated and hard to understand. Because of lower signal-to-noise rate , it is much more difficult to separate different ocean features than to separate different land features. A completely novel method is presented to separate ocean features from multifrequency polarimetric SAR imagery. AIRSAR data from Jet Propulsion Laboratory (JPL), National Aeronautics and Space Administration (NASA) are used in the case studies and good results are achieved.

Excitation of Annual Polar Motion by the Pacific,Atlantic and Indian Oceans

The global oceans play important roles in exciting the annual polar motion besides the atmosphere. However, it is still unclear about how large the regional oceans contribute to the annual polar motion. We investigate systemically the contributions of the Pacific, Atlantic and Indian Oceans to the excitation of the annual polar motion, based on the output data of ocean current velocity field and ocean bottom pressure field from ＂Estimating the Circulation and Climate of the Ocean （ECCO）＂ ocean circulation model over the period 1993-2005. The result shows that due to its particular location and shape, the Atlantic Ocean makes a less significant contribution to the x-component of the annual polar motion excitation than the Pacific and Indian Oceans, while all these three oceans contribute to the y-component of the annual polar motion excitation to some extent.

A Comparison of Polar Vortex Response to Pacific and Indian Ocean Warming

During recent decades, the tropical Indo-Pacific Ocean has become increasingly warmer. Meanwhile, both the northern and southern hemispheric polar vortices （NPV and SPV） have exhibited a deepening trend in boreal winter. Although previous studies have revealed that the tropical Indian Ocean warming （IOW） favors an intensifying NPV and a weakening SPV, how the tropical Pacific Ocean warming （POW） influences the NPV and SPV remains unclear. In this study, a comparative analysis has been conducted through ensemble atmospheric general circulation model （AGCM） experiments. The results show that, for the Northern Hemisphere, the two warmings exerted opposite impacts in boreal winter, in that the IOW intensified the NPV while the POW weakened the NPV. For the Southern Hemisphere, both the IOW and POW warmed the southern polar atmosphere and weakened the SPV. A diagnostic analysis based on the vorticity budget revealed that such an interhemispheric difference in influences from the IOW and POW in boreal winter was associated with different roles of transient eddy momentum flux convergence between the hemispheres. Furthermore, this difference may have been linked to different strengths of stationary wave activity between the hemispheres in boreal winter.

Polar Vortex Response to Pacific Ocean Warming and Its Additive Nonlinearity with the Indian Ocean

A previous modeling study about Pacific Ocean warming derived polar vortex response signals, by subtracting those in the Indian Ocean warming experiments from those in the Indo-Pacific. This approach questions the resemblance of such an indirectly derived response to one directly forced by Pacific Ocean warming. This is relevant to the additive nonlinearity of atmospheric responses to separated Indian and Pacific Ocean forcing. In the present study, an additional set of ensemble experiments are performed by prescribing isolated SST forcing in the tropical Pacific Ocean to address this issue. The results suggest a qualitative resemblance between responses in the derived and additional experiments. Thus, previous findings about the impact of Indian and Pacific Ocean warming are robust. This study has important implications for future climate change projections, considering the non-unanimous warming rates in tropical oceans in the 21st century. Nevertheless, a comparison of present direct-forced experiments with previous indirect-forced experiments suggests a significant additive nonlinearity between the Indian and Pacific Ocean warmings. Further diagnosis suggests that the nonlinearity may originate from the thermodynamic processes over the tropics.

利用水波初至偏振方位反演海底地震仪位置及方位

OBS(Ocean Bottom Seismometer,海底地震仪)在布放到海底之后,其方位指向通常是随机的;由于海流等因素的影响,其实际位置通常也会偏离投放位置,因此需要对其位置及方位进行重定位定向。针对目前的定位和定向方法大多基于走时计算,本文首先讨论了利用海底地震仪的水波初至偏振方位进行海底地震仪水平位置及方位重定位定向的线性反演方法和非线性反演方法,给出了线性反演的近似公式,并分析了近似公式的误差;然后,通过大量理论模型试验对比了两种方法的误差及稳定性;最后,对我国南海某地的5台OBS实测数据进行了反演处理。理论模型试验结果表明,在一些特殊情况下,线性反演存在不收敛的情况,而非线性方法则具有较好的稳定性和较高的精度。非线性反演方法采用差分演化算法,对比了直接优化方位角残差目标函数和双差法,结果表明,对于理论模型和实际数据两种方法得到的结果几乎完全相同,但迭代收敛情况双差法明显好于前者,双差法经600余次迭代达到最优稳定状态,而前者在迭代1000多次之后才达到稳定最优状态。

卫星遥感北大西洋风暴“尤尼斯”生成和发展特征

2022年2月中旬,北大西洋冬季风暴“尤尼斯”(Eunice)给欧洲中、西部带来严重自然灾害。以卫星观测数据为主,研究了“尤尼斯”发生的环境场、卫星水汽图像干侵入特征、对流层中高层位涡强迫对爆发性发展的影响等。结果表明:“尤尼斯”活动期间,北半球高纬度西半球偏冷、东半球偏暖,极涡偏向北美大陆,北美极区附近平均气温偏低。“尤尼斯”的生成和北美极区附近极涡分裂南下的冷空气沿着西风带东传有关。爆发性发展期间,海平面气压下降率约40 hPa/(24 h),远超爆发性发展指标(24 hPa/(24 h)),且出现在海温正距平区。格陵兰岛南部气旋提供的极区冷空气对爆发性发展尤为重要,该冷空气在北大西洋洋面形成强西北风转偏西风,表现为排列整齐的大范围细胞状积云一直延伸至风暴中心附近,卫星水汽图像上表现为快速增强的干侵入特征,并伴有高位涡异常。发展至最强阶段,高位涡向下伸展,400 hPa最强高位涡区位于风暴中心的正上方,500 hPa以下高位涡向东南方向倾斜,并伴随着对流层中、下层强下沉运动,下沉运动为低空风速增强提供了一定的高空能量来源,高位涡侵入的下方也有利于低层气旋式环流发展。

Progress in application of MODIS for remote sensing in Polar Regions

The remote sensing technique is widely used in Polar Regions,and Moderate Resolution Imaging Spectroradiomete（MODIS） is one of the most important satellite sensors in the domain of remote sensing.In this article,MODIS sensor,including the information of its satellites,its system constitutes,its hardware characteristic,its large spectra and usual applications are briefly introduced first.Then,there is a particular introduction of MODIS＇s use in Polar Regions,which refers to the polar physiognomy,polar atmosphere and polar ocean,with citing many examples.At last,views about the development of MODIS and its series sensors in the future,including the improved applications in Polar Regions are given.

The study of ice shelf-ocean interaction techniques and recent results

Although the importance to global oceanography of ice shelf-oceaaa interactions has been recognized for many years, only more recently has its role in the control of ice flow- from the interior, grounded ice sheet into the ocean been more clearly understood. The consequences for global sea level of increasing ice loss from the Antarctic and Greenland ice sheets has prompted rapidly growing research efforts in this area. Here we describe the different techniques commonly employed in the field study of ice shelf-ocean interactions. We focus on techniques used by the British Antarctic Survey, primarily on Filchner-Ronne Ice Shelf, and describe some recent results from instruments deployed both beneath the ice shelf and on its upper surface, which demonstrate variability at a broad range of time scales.

Decadal Variability Shown by the Arctic Ocean Hydrochemical Data and Reproduced by an Ice-Ocean Model

The Arctic is experiencing a significant warming trend as well as a decadal oscillation. The atmospheric circulation represented by the Polar Vortex and the sea ice cover show decadal variabilities, while it has been difficult to reveal the decadal oscillation from the ocean interior. The recent distribution of Russian hydrochemical data collected from the Arctic Basin provides useful information on ocean interior variabilities. Silicate is used to provide the most valuable data for showing the boundary between the silicate-rich Pacific Water and the opposite Atlantic Water. Here, it is assumed that the silicate distribution receives minor influence from seasonal biological productivity and Siberian Rivers outflow. It shows a clear maximum around 100m depth in the Canada Basin, along with a vertical gradient below 100 m, which provides information on the vertical motion of the upper boundary of the Atlantic Water at a decadal time scale. The boundary shifts upward (downward), as realized by the silicate reduction (increase) at a fixed depth, responding to a more intense (weaker) Polar Vortex or a positive (negative) phase of the Arctic Oscillation. A coupled ice-ocean model is employed to reconstruct this decadal oscillation.

Phytoplankton abundance and community structure in the Antarctic polar frontal region during austral summer of 2009

The Antarctic polar front region in the Southern Ocean is known to be most productive. We studied the phytoplankton community structure in the Indian sector at this frontal location during late austral summer (February, 2009) onboard R/V Akademic Boris Petrov. We used the phytoplankton and microheterotrophs abundance, as also the associated physico-chemical parameters to explain the low phytoplankton abundance in the study region. This study emphasizes the shift of phytoplankton, from large (>10 μm) to small (<10 μm) size. The phytoplankton abundance appears to be controlled by physical parameters and by nutrient concentrations and also by the microheterotrophs (ciliates and dinoflagellates) which exert a strong grazing pressure. This probably reduces small (<10 μm) and large (>10 μm) phytoplankton abundance during the late austral summer. This study highlights the highly productive polar front nevertheless becomes a region of low phytoplankton abundance, due to community shifts towards pico-phytoplankton (<10 μm) during late austral summer.

Impacts of Polar Vortex,NPO,and SST Configurations on Unusually Cool Summers in Northeast China.Part I:Analysis and Diagnosis

This study unveils the evolution of two major early signals in the North Pacific atmosphere-ocean system that heralded abnormal high-pressure blockings and cold-vortex activities across Northeast China, based on an analysis of the configurations of major modes including the polar vortex, the North Pacific Oscillation （NPO）, and SST in the preceding winter and spring and atmospheric low-frequency disturbances in Northeast China. We analyzed these aspects to understand the atmosphere ocean physical coupling processes characterized by the two early signals, and here we explain the possible mechanisms through which dipole circulation anomalies affect the summer low-temperature processes in Northeast China. We further analyzed the interdecadal variation background and associated physical processes of the two early signals.

Improved geophysical excitations constrained by polar motion observations and GRACE/SLR time-dependent gravity

At seasonal and intraseasonal time scales, polar motions are mainly excited by angular momentum fluctuations due to mass redistributions and relative motions in the atmosphere, oceans, and continental water, snow, and ice, which are usually provided by various global atmospheric, oceanic, and hydrological models（some with meteorological observations assimilated; e.g., NCEP, ECCO, ECMWF, OMCT and LSDM etc.）. Unfortunately, these model outputs are far from perfect and have notable discrepancies with respect to polar motion observations, due to non-uniform distributions of meteorological observatories,as well as theoretical approximations and non-global mass conservation in these models. In this study,the LDC（Least Difference Combination） method is adopted to obtain some improved atmospheric,oceanic, and hydrological/crospheric angular momentum（AAM, OAM and HAM/CAM, respectively）functions and excitation functions（termed as the LDCgsm solutions）. Various GRACE（Gravity Recovery and Climate Experiment） and SLR（Satellite Laser Ranging） geopotential data are adopted to correct the non-global mass conservation problem, while polar motion data are used as general constraints. The LDCgsm solutions can reveal not only periodic fluctuations but also secular trends in AAM, OAM and HAM/CAM, and are in better agreement with polar motion observations, reducing the unexplained excitation to the level of about 5.5 mas（standard derivation value; about 1/5-1/4 of those corresponding to the original model outputs）.

极地海洋多波束测量测线布设系统设计及实现

针对目前多波束测量缺少专门的测线布设软件问题,考虑极地海域海冰对多波束测量的影响,本文设计并实现了极地海洋多波束测量测线布设系统。首先针对航前与现场作业等场景,设计了系统技术路线、架构和主要功能,特色功能包括建议测线方向计算、测线自动与手动生成、多波束现场处理数据导入和结果可视化评价等。阐述了系统功能实现的关键技术,包括测线自动生成、条幅制作与信息统计等。系统采用Py⁃thon语言以及第三方开源工具包开发,最后开展不同场景下的应用试验并对结果进行了讨论。试验结果表明,系统可以快速、方便地进行多波束测量测线布设并对布设结果进行评价,能够有效提高多波束测量方案的设计效率,有利于极地海底地形地貌调查工作的开展。

东天山卡拉塔格复式岩体的时代、成因及构造意义

东天山位于中亚造山带最南部,记录了中亚造山带晚期的俯冲增生过程,然而早古生代一些关键地质演化过程仍存在争议,特别是大南湖-头苏泉带的构造属性、俯冲起始时间及俯冲极性。本文选取大南湖-头苏泉带北缘的卡拉塔格复式岩体开展了系统的年代学和地球化学工作,以揭示该带早古生代构造演化过程。锆石U-Pb定年结果显示,花岗岩、花岗闪长岩和辉长闪长岩分别形成于434±4 Ma、442±2 Ma和445±4 Ma,表明该复式岩体主要形成于早志留世。花岗岩和花岗闪长岩均显示低磷(P_(2)O_5<0.1%)、富钠(K_(2)O/Na_(2)O≤0.5)、准铝质-弱过铝质(A/CNK=0.57~1.24,0.91~1.03)的钙碱性I型花岗岩特征。样品具有较低的Sr/Y(1.9~4.5,8.1~11.4)和(La/Yb)N值(1.6~2.4,2.4~3.0),较高的ε_(Hf)(t)(+12.7~+15.5,+11.0~+14.7)和ε_(Nd)(t)值(+7.0~+7.5,+7.1~+7.7),以及年轻的二阶段Hf模式年龄(426~589Ma,485~722Ma)和Nd模式年龄(559~603Ma,555~598Ma),表明花岗岩和花岗闪长岩是年轻下地壳部分熔融的产物。辉长闪长岩相对富集大离子亲石元素(LILE)、高度不相容元素,亏损高场强元素(HFSE),显示典型的与俯冲相关的岩浆的地球化学特征;其较高的MgO含量(5.26%~5.54%),亏损的ε_(Hf)(t)(+12.1~+15.7)和ε_(Nd)(t)值(+7.1~+7.3),说明母岩浆来源于亏损地幔。辉长闪长岩高的Ce/Nb(11.5~16.1)和低的Th/La值(0.11~0.13)指示地幔源区经历了板片流体的交代作用。综合前人对该地区早古生代岩浆活动的研究成果,我们认为大南湖-头苏泉带岩浆弧早志留世处于康古尔洋向北俯冲的洋内弧环境,且俯冲开始时间不晚于早志留世。

利用折射波的海底节点地震三分量检波器重定向方法

在海底节点(Ocean Bottom Nodes,OBN)地震中,因为水下检波器实际姿态的任意性,三分量检波器的重定向成为OBN勘探需解决的首要问题。为此,提出一种根据折射波偏振特性进行OBN三分量检波器重定向的方法。首先,引入三个欧拉角描述坐标系的旋转,给出检波点两侧炮点产生折射波偏振矢量的三种特性,并根据该三种特性建立误差函数以描述检波器姿态与设计姿态的偏差;然后,利用不同欧拉角对原始地震记录进行旋转,每次旋转后求取检波点两侧炮点产生折射波的偏振矢量,并计算相应的误差函数,误差函数最小的欧拉角即为姿态校正角;最后,利用求取的校正角对原始地震记录进行校正,即可实现检波器重新定向,从而将实际采集信号校正到检波器沿设计方位放置时应有的地震记录。模型试验和实际数据处理结果表明,该方法易于实现且计算精度高,可用于未安装罗经姿态传感器的OBN地震数据校正。

高强不锈钢在海水环境中的阴极保护行为研究

目的研究不同阴极极化电位下高强不锈钢的极化行为,确定某高强不锈钢合理的阴极保护电位区间。方法通过动电位极化测试以及电化学阻抗测试等电化学测试手段,研究此种高强不锈钢在海水中的阴极反应过程,通过不同极化电位下的恒电位极化测试,结合扫描电子显微镜和能谱仪,观察分析试样表面的腐蚀产物,研究阴极极化电位对高强不锈钢表面阴极产物膜的影响规律,以及对高强不锈钢在海水中的阴极保护效果。结果动电位极化测试表明,在-0.50~-0.90 V,只需要施加很小的阴极电流,就可使极化电位发生显著变化。电化学阻抗谱测试及拟合结果表明,极化电位在-0.70 V时,电极反应的电荷转移电阻最大,此时腐蚀被完全抑制。恒电位极化测试发现,随着电位负移,极化电流密度整体上呈现先减小、后增大的趋势。用能谱仪分析其表面产物发现,钙镁沉积层的致密度呈现先增加、后降低的趋势。结论此种高强不锈钢在海水环境中施加阴极电位为-0.50~-1.00 V时,可以得到有效保护。

极地海洋石油烃污染物的生物降解研究进展

随着南极考察活动的发展和北极地区的开发利用,极地海洋中的石油烃污染逐渐增多。由于这些地区常年处于低温状态,石油烃的自然降解非常缓慢。生物降解是修复污染的一个主要机制,具有经济、高效的特点。极地海洋环境中存在着大量烃降解菌,它们在清除当地石油烃污染中发挥了很大作用,并显现出了低温修复的潜力。本文从极地海洋环境中的石油烃降解菌、影响低温降解的因素、降解基因和低温生物修复四个方面介绍了国外对该领域的研究成果。