南海夏季风爆发与南大洋海温变化之间的联系

利用1979-2009年NCEP第二套大气再分析资料和ERSST海温资料,分析南海夏季风爆发时间的年际和年代际变化特征,考察南海夏季风爆发早晚与南大洋海温之间的联系.主要结果为:(1)南海夏季风爆发时间年际和年代际变化明显,1979-1993年与1994-2009年前后两个阶段爆发时间存在阶段性突变;(2)南海夏季风爆发时间与前期冬季(12-1月)印度洋-南大洋(0-80°E,75°S-50°S)海温、春季(2-3月)太平洋-南大洋(170°E -80°W,75°S-50°S)海温都存在正相关关系,当前期冬、春季南大洋海温偏低(高)时,南海夏季风爆发偏早(晚).南大洋海温信号,无论是年际还是年代际变化,都对南海夏季风爆发具有一定的预测指示作用;(3)南大洋海温异常通过海气相互作用和大气遥相关影响南海夏季风爆发的迟早.当南大洋海温异常偏低(偏高)时,冬季南极涛动偏强(偏弱),同时通过遥相关作用使热带印度洋-西太平洋地区位势高度偏低(偏高)、纬向风加强(减弱),热带大气这种环流异常一直维持到春季4、5月份,位势高度和纬向风异常范围逐步向北扩展并伴随索马里越赤道气流的加强(减弱),从而为南海夏季风爆发偏早(偏晚)提供有利的环流条件.初步分析认为,热带大气环流对南大洋海气相互作用的遥响应与半球际大气质量重新分布引起的南北涛动有关.     

Surface circulation patterns in the Sicily Channel and Ionian Sea as revealed by MODIS chlorophyll images from 2003 to 2007

The surface circulation in the Sicily Channel and in the Ionian Sea is investigated using MODerate-resolution Infrared Spectro-radiometer (MODIS) chlorophyll-a images collected from 2003 to 2007. The use of chlorophyll as surface tracer in the area is verified by comparison with satellite altimeter measurements available during the same period.     

Seasonal dynamics of microbial sulfate reduction in temperate intertidal surface sediments: controls by temperature and organic matter

The role of microbial sulfate reduction on organic matter oxidation was studied quantitatively in temperate intertidal surface sediments of the German Wadden Sea (southern North Sea) on a seasonal base in the years 1998–2007. The sampling sites represent the range of sediments found in the back-barrier tidal area of Spiekeroog Island: sands, mixed and muddy flats. The correspondingly different contents in organic matter, metals, and porosities lead to significant differences in the activity of sulfate-reducing bacteria with volumetric sulfate reduction rates (SRR) in the top 15 cm of up to 1.4 μmol cm^?3 day^?1. Depth-integrated areal SRR ranged between 0.9 and 106 mmol m^?2 day^?1, with the highest values found in the mudflat sediments and lower rates measured in sands at the same time, demonstrating the impact of both temperature and organic matter load. According to a modeling approach for a 154-km² large tidal area, about 39, 122, and 285 tons of sulfate are reduced per day, during winter, spring/autumn, and summer, respectively. Hence, the importance of areal benthic organic matter mineralization by microbial sulfate reduction increases during spring/autumn and summer by factors of about 2 and 7, respectively, when compared to winter time. The combined results correspond to an estimated benthic organic carbon mineralization rate via sulfate reduction of 78 g C m^?2 year^?1.     

Seasonal variability and dynamics of coastal sea surface temperature fronts in the East China Sea

Ocean Dynamics - Fronts in coastal oceans are important mesoscale processes that relate to regional dynamics and can impact ecosystems. The daily distribution of a sea surface temperature (SST)...     

青藏高原热状况和海温异常对亚洲季风季节转换年际变化的影响

本文根据季节转换前后副高脊面附近经向温度梯度变号的本质,利用相关分析和合成分析等方法研究了季节转换年际变化与外部影响因子的联系. 结果表明,冬春季青藏高原热状况和ENSO（El Nio/Southern Oscillation,厄尔尼诺/南方涛动）是决定亚洲季风区季节转换年际变化的主要因素. 当冬、春季海温呈现El Nio异常时,Walker环流减弱,于是西太平洋暖池区对流活动受到抑制,而赤道东太平洋对流活动加强则强迫赤道印度洋地区产生绝热下沉运动,使得印度洋地区大气偏暖,结果增大了南北向温度梯度,季节转换往往偏晚. 反之,季节转换偏早. 初春高原上空对流层中高层的气温异常对于判断季节转换迟早有很好的指示意义.     

南海蒸发和净淡水通量的季节和年际变化

以19年（1988～2006年）的SSM/I（Special Sensor Microwave/ Imager）卫星观测为基础,计算了南海的逐月海面蒸发量,并结合SSM/I的降雨观测,得到了南海的逐月净淡水通量,并分析其季节和年际变化.研究结果表明：南海的蒸发量年变化基本呈双峰型结构,降雨和净淡水通量呈单峰型结构.1988～2001年,南海的蒸发量呈上升趋势,增长速率为1 mm/yr;2001～2006年,以1.9 mm/yr的速率减少.南海的降雨量和净淡水通量与Nino3指数成负相关,相关系数为-0.62和-0.58.在1997～1998厄尔尼诺暖事件期间,降雨量和净淡水通量均显著下降,且以其为界,降雨量在此之前以1.3 mm/yr的速率增长,净淡水通量升降趋势不明显;而在此之后,降雨以8.5 mm/yr的速率下降,净淡水通量的下降速率为7.5 mm/yr.     

Modelling the uptake and release of carbon dioxide in the Baltic Sea surface water

We present and analyse a fully coupled physical–biogeochemical model of the uptake and release of carbon dioxide in the Baltic Sea. The modelling includes the interaction between physical (stratification, temperature, salinity, penetration of solar radiation, and ice), chemical (total alkalinity, pH, dissolved inorganic carbon, oxygen, and nutrients), and biological processes (plankton and dissolved organic carbon (DOC)). These processes have been built into an advanced process-oriented coupled basin ocean model that has been extensively explored and validated for the Baltic Sea.     

1901-2016年印太海域海表温度的偏差订正及数据集研制

海表温度系统性观测偏差的订正是开展长历史序列网格化海表温度气候数据产品研制的关键.本文在引入美国SR02海表温度偏差订正方法的基础上,结合国家气象信息中心自主研发的全球海表观测定时值数据集,进行了相关参数的优化改进,从而研制了1901—2016年印度洋—太平洋核心海域月平均2°×2°分辨率的海表温度偏差订正数据集.对海温偏差订正量的时空分布特征分析表明,基于自主研制的基础数据和优化改进的方法求解的偏差订正量能有效反映海表温度观测手段的历史变迁,以及海表温度系统性偏差随季节变化的规律.同时,与ERSST订正量的对比表明,由于优化改进后的方法其阈值计算随空间样本而变,因而其局地变化特征的表现能力更强,且其订正量在观测手段转型期的变化更为明显.相较订正前的海表温度距平（SSTA）场,订正后的SSTA资料与ERSSTv5 SSTA间的偏差误差和均方根误差均有明显降低.其中,偏差误差的缩减比例在37.7%~87.9%之间,均方根误差可降低0.06℃.此外,与国际同类产品的对比表明,本文发展的SSTA订正数据集与国际同类SSTA产品序列的相关系数不低于0.97,且变化趋势类似.从差异对比上看,除中高纬东亚大陆近海区域外,本文的偏差订正数据集与国际上同类产品的SSTA差异基本在-0.2~0.2℃之间.

     

卫星测高揭示的海面变化经纬向耦合特征及其对ENSO事件响应

本文引入3阶主张量分析方法对1993~2008年赤道太平洋地区卫星测高数据进行解析,前两个主张量可有效表征海面变化的经、纬向耦合特征,重构与对比了该时段内6次ENSO事件海面变化的经、纬向演化的空间构型与耦合作用过程.结果表明:海面的经向变化可表征ENSO强度变化,纬向变化表现为受ENSO影响的年周期波动;经、纬向张量的时间系数与MEI以及EMI指数间多尺度分析表明,两者均受El Niño Modoki影响,但在耦合尺度、能量共振关系以及相位关系上存在差异;海面变化对不同类型ENSO事件响应差异主要表现在高、低海面位置、振幅以及高、低值区分布形态与空间范围等方面.其中常规的El Niño多表现为东太平洋型ENSO,El Niño Modoki则表现为中太平洋型.不同类型的ENSO在经纬向耦合演化轨迹的周期性、规则性和方向性特征可在一定程度上作为ENSO类型区分依据.     

Seasonal and spatial heterogeneity of recent sea surface temperature trends in the Caribbean Sea and southeast Gulf of Mexico

Recent changes in ocean temperature have impacted marine ecosystem function globally. Nevertheless, the responses have depended upon the rate of change of temperature and the season when the changes occur, which are spatially variable. A rigorous statistical analysis of sea surface temperature observations over 25 years was used to examine spatial variability in overall and seasonal temperature trends within the wider Caribbean. The basin has experienced high spatial variability in rates of change of temperature. Most of the warming has been due to increases in summer rather than winter temperatures. However, warming was faster in winter in the Loop Current area and the south-eastern Caribbean, where the annual temperature ranges have contracted. Waters off Florida, Cuba and the Bahamas had a tendency towards cooling in winter, increasing the amplitude of annual temperature ranges. These detailed patterns can be used to elucidate ecological responses to climatic change in the region.     

Planktonic foraminifera and sea surface temperature (SST) of the Xisha Trough, South China Sea since Last Glaciation

South China Sea is the largest marginal sea of the Western Pacific between the Pacific Ocean and Asia Continent. It has been influenced by both the Pacific Ocean and continental climate. Its continental margins are broad in north and south, narrow in west. There are many islands in east. A large amount of siliciclastic sediments derived from peri-continents and islands were trans-ported into the sea[1], in which significant information of paleoceanography and paleoclimate and paleoenvironm…     

东北夏季气温变异的区域差异及其与大气环流和海表温度的关系

利用1951～2000年中国东北地区23个台站资料，对东北夏季气温的时空分布进行了研究，发现其变化除具有整体的一致性外，东北南部和北部的夏季气温在年际和年代际时间尺度都表现出很大不同，其中北部区域的夏季气温在1987～1988年间发生了一次显著的气候突变. 另外，剔除夏季气温全区一致变化的年份后，南北两区夏季气温与大气环流和海表温度的关系表明：突变前，影响北部和南部冷/热夏季的大气环流形势存在显著的不同，关键海域亦有很大差异：影响南部的为中纬度西太平洋和印度洋部分海域，影响北部的主要为ENSO事件；突变后，两区的夏季气温及相应大气环流和关键海区都趋于一致. 在整个分析时段内，北部夏季气温与东亚夏季风存在显著负相关，而南部的关系则不明显.     

Export fluxes of biogenic matter in the presence and absence of seasonal sea ice cover in the Chukchi Sea

Drifting sediment traps were deployed at 9 stations in May-June (ice-covered conditions) and July-August (ice-free conditions) 2004 in the Chukchi Sea to investigate the variability in export fluxes of biogenic matter in the presence and absence of sea ice cover. Measurements of chlorophyll-a (Chl-a), particulate organic carbon (POC), particulate nitrogen (PN), phytoplankton, zooplankton fecal pellets, and the stable carbon isotope composition (δ¹³C) of the sinking material were performed along Barrow Canyon (BC) and a parallel shelf-to-basin transect from East Hanna Shoal (EHS) to the Canada Basin. POC export fluxes were similarly high in the presence (378±106 mg C m⁻² d⁻¹) and in the absence of ice cover (442±203 mg C m⁻² d⁻¹) at the BC stations, while fluxes were significantly higher in the absence (129±98 mg C m⁻² d⁻¹) than in the presence of ice cover (44±29 mg C m⁻² d⁻¹) at the EHS stations. The C/N ratios and δ¹³C values of sinking organic particles indicated that POC export fluxes on the Chukchi continental shelf were mostly composed of freshly produced labile material, except at the EHS stations under ice cover where the exported matter was mostly composed of refractory material probably advected into the EHS region. Chl-a fluxes were higher under ice cover than in ice-free water, however, relatively low daily loss rates of Chl-a and similar phytoplankton carbon fluxes in ice-covered and ice-free water suggest the retention of phytoplankton in the upper water column. An increase in fecal pellet carbon fluxes in ice-free water reflected higher grazing pressure in the absence of ice cover. Elevated daily loss rates of POC at the BC stations confirmed other indications that Barrow Canyon is an important area of carbon export to the basin and/or benthos. These results support the conclusion that there are large spatial and temporal variations in export fluxes of biogenic matter on the Chukchi continental shelf, although export fluxes may be similar in the presence and in the absence of ice cover in highly productive regions.     

Validation of AVHRR and TMI-derived sea surface temperature in the northern South China Sea

Satellite-derived SSTs are validated in the northern South China Sea (NSCS) using in situ SSTs from the drifting buoys and well-calibrated sensors installed on Research/Vessel(R/V) Shiyan 3. The satellite SSTs are Advanced Very High Resolution Radiometer (AVHRR) daytime SST, AVHRR nighttime SST, Tropical rainfall Measuring Mission Microwave Imager (TMI) daytime SST and TMI nighttime SST. Availability of satellite SST, which is the ratio that the number of available satellite SST to the total ocean pixels in NSCS is calculated; annual average SST availabilities of AVHRR daytime SST, AVHRR nighttime SST, TMI daytime SST and TMI nighttime SST are 68.42%, 69.99%, 56.57% and 52.80%, respectively. Though the TMI SST availability is nearly constant throughout the year, the variations of the AVHRR SST availability are much larger because of seasonal variations of cloud cover in NSCS. Validation of the satellite-derived SSTs shows that bias±standard deviation (STD) of AVHRR SST is −0.43±0.76 and −0.33±0.79 °C for daytime and nighttime, respectively, and bias±STD of TMI SSTs is 0.07±1.11 and 0.00±0.97 °C for daytime and nighttime, respectively. It is clear that AVHRR SSTs have significant regional biases of about −0.4 °C against the drifting buoy SSTs. Differences between satellite-derived−in situ SSTs are investigated in terms of the diurnal SST cycle. When satellite-derived wind speeds decrease down below 6 m/s, the satellite SSTs become higher than the corresponding in situ SSTs, which means that the SST difference (satellite SST−Buoy SST) is positive. This wind-speed dependence of the SST difference is consistent with the previous results, which have mentioned that low wind speed coupled with clear sky conditions (high surface solar radiation) enhance the diurnal SST amplitude and the bulk-skin temperature difference.     

Annual variation of sea surface height,dynamic topography and circulation in the South China Sea

TOPEX/Poseidon satellite altimetry data from 1993 to 1999 were used to study mean annual variation of sea surface height anomaly (SSHA) in the South China Sea (SCS) and to reproduce its climatological monthly surface dynamic topography in conjunction with historical hydrographic data. The characters and rules of seasonal evolution of the SCS dynamic topography and its upper circulation were then discussed. Analyses indicate that annual variation of the SCS large-scale circulation could be divided into four major phases. In winter (from November to February), the SCS circulation is mainly controlled by double cyclonic gyres with domination of the northern gyre. Other corresponding features include the Kuroshio intrusion from the Luzon Strait and the northeastward off-shelf current in the area northwest off Kalimantan Island. The double gyre structure disassembled in spring (from March to April) when the northern gyre remains cyclonic, the southern gyre becomes anticyclonic, and the general circulation pattern shows a dipole. There is no obvious large-scale closed gyre inside the SCS basin in both summer (from May to July) and autumn (from August to October) when the SCS Monsoon Jet dominates the circulation, which flows northeastward across the SCS. Even so, circulation patterns of these two phases diverse significantly. From May to July, the SCS monsoon jet flows northward near the Vietnam coast and bends eastward along the topography southeast off Hainan Island at about 18°N forming an anticyclonic turn. It then turns northeastward after crossing the SCS. From August to October, however, the monsoon Jet leaves the coast of Vietnam and enters interior of the basin at about 13°N, and the general circulation pattern becomes cyclonic. The Kuroshio intrusion was not obvious in spring, summer and autumn. It is suggested from these observations that dynamic adjustment of the SCS circulation starts right after the peak period of the prevailing monsoon.     

Terrestrial and marine biomarker estimates of organic matter sources and distributions in surface sediments from the East China Sea shelf

Revealing of the sources and distributions of sedimentary organic matter in the East China Sea (ECS) is important for understanding its carbon cycle, which has significant temporal and spatial variability due to the influences of recent climate changes and anthropogenic activities. In this study, we report the contents of both terrestrial and marine biomarkers including ∑C₂₇+C₂₉+C₃₁n-alkanes (38.6-580 ng/g), C₃₇ alkenones (5.6-124.6 ng/g), brassicasterol (98-913 ng/g) and dinosterol (125-1521 ng/g) from the surface sediments in the Changjiang River Estuary (CRE) and shelf areas of the ECS. Several indices based on biomarker contents and ratios are calculated to assess the spatial distributions of both terrestrial and marine organic matter in the ECS surface sediments, and these results are compared with organic matter distribution patterns revealed by the δ¹³C (−20.1‰ to −22.7‰) and C/N ratio (5-7.5) of total organic matter. The contents of terrestrial biomarkers in the ECS surface sediments decrease seaward, controlled mostly by Changjiang River (CR) inputs and surface currents; while higher contents of the two marine biomarkers (brassicasterol and dinosterol) occur in upwelling areas outside the CRE and in the Zhejiang-Fujian coastal zone, controlled mostly by marine productivity. Four proxies, f_Terr(δ¹³C) (the fraction of terrestrial organic matter in TOC estimated by TOC δ¹³C), odd-alkanes (∑C₂₇+C₂₉+C₃₁n-alkanes), 1/P_mar-aq ((C₂₃+C₂₅+C₂₉+C₃₁)/(C₂₃+C₂₅) n-alkanes) and TMBR (terrestrial and marine biomarker ratio) (C₂₇+C₂₉₊C₃₁n-alkanes)/((C₂₇+C₂₉+C₃₁) n-alkanes+(brassicasterol+dinosterol+alkenones)), reveal a consistent pattern showing the relative contribution of terrestrial organic matter (TOM) is higher in the CRE and along the Zhejiang-Fujian coastline, controlled mostly by CR inputs and currents, but the TOM contribution decreases seaward, as the influences of the CR discharge decrease.     

Modelled variability of the sea surface circulation in the North-western Mediterranean Sea and in the Gulf of Lions

A chain of three nested models, based on the MARS 3D code, is used to simulate the North-western Mediterranean Sea circulation with a finest grid of 1.2 km resolution and 30 vertical sigma levels. This modelling system allows to resolve the coastal dynamics taking into account the influence of the general basin circulation. The aim of this study is to assess the ability of the nested MARS-3D models to reproduce most of the circulation features observed in the North-western Mediterranean Basin and in the Gulf of Lions. Comparisons of modelled sea surface temperature and salinity with MEDAR/MEDATLAS climatology and NOAA/AVHRR satellite measurements show that the model accurately reproduces the large and coastal scale variability. Over the Northern Basin, the seasonal changes of the cyclonic gyre extension are correctly simulated, even though in summer, the modelled temperature of the surface layer remains in basin-average 1°C cooler than the satellite measured temperature. As soon as the stratification erodes, modelled and observed temperatures become closer. Over the Gulf of Lions, realistic coastal responses are obtained under different wind conditions. Upwellings are correctly located and their intensity and spatial extension were here improved by the use of Aladin wind fields (10 km spatial resolution) and the introduction of a drag coefficient fitted according to the stability of the planetary boundary layer. The dispersion of fresh Rhone water discharge and the mesoscale circulation simulated by MARS-3D also agree with satellite measurements.     

Long-term trends and regime shifts in sea surface temperature on the continental shelf of the northeast United States

We investigated sea surface temperature (SST) variability over large spatial and temporal scales for the continental shelf region located off the northeast coast of the United States between Cape Hatteras, North Carolina, and the Gulf of Maine using the extended reconstruction sea surface temperature (ERSST) dataset. The ERSST dataset consists of 2°×2° (latitude and longitude) monthly mean values computed from in situ data derived from the International Comprehensive Ocean Atmosphere Data Set (ICOADS). Nineteen 2°×2° bins were chosen that cover the shelf region of interest between the years of 1854 and 2005. Mean annual and range of SST were examined using dynamic factor analysis to estimate trends in both parameters, while chronological clustering was used to determine temporal SST patterns and breakpoints in the time series that are believed to signal regime shifts in SST. Both SST and SST trend analysis show that interannual variability of SST fluctuations shows strong coherence between bins, with declining SST at the beginning of the last century, followed by increasing SST through 1950, and then rapidly decreasing between 1950 and mid-1960s, with somewhat warmer SST thereafter to present. Annual SST range decreases in a seaward direction for all bins, with strong coherence for interannual variability of range fluctuations between bins. The trend in SST range shows a decreasing range at the beginning of the last century followed by an increase in range from 1920 to the late-1980s, remaining high through present with some spatial variability. A more detailed spatial analysis was conducted by grouping the data into 7 regions using principal component analysis. We analyzed regional trends in mean annual SST, seasonal SST range (summer SST−winter SST), and normalized SST minima and maxima. Both the summer and winter seasons were also analyzed using the length of each season and amplitude of the warming and cooling season, respectively, along with the spring warming and fall cooling rates. Trends in all of the parameters were examined after low-pass filtering using a 10-point convolution filter (n=10 years) and regime shifts were identified using the sequential t-test analysis of regime shifts (STARS) method. The analysis shows some difference between regions in the timing of minimum SST with minima being reached 1 month earlier in the south (February) relative to more northern regions (March). Regional annual SST range decreased in a seaward direction. Amplitude of summer warming and the length of summer have shown fluctuations with recent years showing stronger warming and longer summers but generally not exceeding past levels. Overall, the difference in SST range, with recent larger values may be the most significant finding of this work. SST range changes have the potential to disrupt species important to local fisheries due to combinations of differing temperature tolerances, changes in reproduction potential, and changes in the distributional range of species.