Barotropic Response of the Sea of Okhotsk to Wind Forcing

We have examined wind-induced circulation in the Sea of Okhotsk using a barotropic model that contains realistic topography with a resolution of 9.25 km. The monthly wind stress field calculated from daily European Centre for Medium-Range Weather Forecasting (ECMWF) Re-Analysis data is used as the forcing, and the integration is carried out for 20 days until the circulation attains an almost steady state. In the case of November (a representative for the winter season from October to March), southward currents of velocity 0.1–0.3 m s⁻¹ occur along the bottom contours off the east of Sakhalin Island. The currents are mostly confined to the shelf (shallower than 200 m) and extend as far south as the Hokkaido coast. In the July case (a representative for the summer season from April to September), significant currents do not occur, even in the shallow shelves. The simulated southward current over the east Sakhalin shelf appears to correspond to the near-shore branch of the East Sakhalin Current (ESC), which was observed with the surface drifters. These seasonal variations simulated in our experiments are consistent with the observations of the ESC. Dynamically, the simulated ESC is interpreted as the arrested topographic wave (ATW), which is the coastally trapped flow driven by steady alongshore wind stress. The volume transport of the simulated ESC over the shelf reaches about 1.0 Sv (1 Sv = 10⁶ m³s⁻¹) in the winter season, which is determined by the integrated onshore Ekman transport in the direction from which shelf waves propagate. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cycladophora davisiana (Radiolaria) in the Okhotsk Sea: A key for reconstructing glacial ocean conditions

Cycladophora davisiana, a radiolarian species dwelling at mesopelagic depths, is known as a representative glacial fauna due to its unique distribution during glacial periods. In the present ocean, abundant production of C. davisiana is only observed in the Okhotsk Sea, indicating an adaptation of C. davisiana for seasonal sea-ice covered conditions. We found pronounced abundant production of C. davisiana during the early to middle Holocene in the Okhotsk Sea, suggesting more favorable conditions for C. davisiana than the present Okhotsk Sea. In order to clarify the reason, oceanographic conditions during the Holocene were reconstructed based on biomarkers, lithogenic grains including ice-rafted debris (IRD), biogenic opal, and total organic carbon (TOC) in two sediment cores from the Okhotsk Sea. These indicators suggest that the pronounced C. davisiana production may be attributed to: 1) a supply to mesopelagic depths under intensified stratification of fine organic particles derived from coccolithophorids, bacteria, and detrital materials; and 2) cold, well-ventilated intermediate water formation.     

Roles of Continental Shelves and Marginal Seas in the Biogeochemical Cycles of the North Pacific Ocean

Most marginal seas in the North Pacific are fed by nutrients supported mainly by upwelling and many are undersaturated with respect to atmospheric CO₂ in the surface water mainly as a result of the biological pump and winter cooling. These seas absorb CO₂ at an average rate of 1.1 ± 0.3 mol C m⁻²yr⁻¹ but release N₂/N₂O at an average rate of 0.07 ± 0.03 mol N m⁻²yr⁻¹. Most of primary production, however, is regenerated on the shelves, and only less than 15% is transported to the open oceans as dissolved and particulate organic carbon (POC) with a small amount of POC deposited in the sediments. It is estimated that seawater in the marginal seas in the North Pacific alone may have taken up 1.6 ± 0.3 Gt (10¹⁵ g) of excess carbon, including 0.21 ± 0.05 Gt for the Bering Sea, 0.18 ± 0.08 Gt for the Okhotsk Sea; 0.31 ± 0.05 Gt for the Japan/East Sea; 0.07 ± 0.02 Gt for the East China and Yellow Seas; 0.80 ± 0.15 Gt for the South China Sea; and 0.015 ± 0.005 Gt for the Gulf of California. More importantly, high latitude marginal seas such as the Bering and Okhotsk Seas may act as conveyer belts in exporting 0.1 ± 0.08 Gt C anthropogenic, excess CO₂ into the North Pacific Intermediate Water per year. The upward migration of calcite and aragonite saturation horizons due to the penetration of excess CO₂ may also make the shelf deposits on the Bering and Okhotsk Seas more susceptible to dissolution, which would then neutralize excess CO₂ in the near future. Further, because most nutrients come from upwelling, increased water consumption on land and damming of major rivers may reduce freshwater output and the buoyancy effect on the shelves. As a result, upwelling, nutrient input and biological productivity may all be reduced in the future. As a final note, the Japan/East Sea has started to show responses to global warming. Warmer surface layer has reduced upwelling of nutrient-rich subsurface water, resulting in a decline of spring phytoplankton biomass. Less bottom water formation because of less winter cooling may lead to the disappearance of the bottom water as early as 2040. Or else, an anoxic condition may form as early as 2200 AD. This revised version was published online in July 2006 with corrections to the Cover Date.     

Seasonal and interannual variations in the East Sakhalin current revealed by TOPEX/POSEIDON altimeter data

Seasonal and interannual variations in the East Sakhalin Current (ESC) are investigated using ten-year records of the sea level anomaly (SLA) observed by the TOPEX/POSEIDON (T/P) altimeter. The T/P SLA clearly documents seasonal and interannual variations in the ESC along the east coast of Sakhalin Island, although sea ice masks the region from January to April. Estimates of surface current velocity anomaly derived from T/P SLA are in good agreement with drifting buoy observations. The ESC is strong in winter, with a typical current velocity of 30–40 cm s⁻¹ in December, and almost disappears in summer. Southward flow of the ESC is confined to the shelf and slope region and consists of two velocity cores. These features of the ESC are consistent with short-term observations reported in previous studies. Analysis of the ten-year records of T/P SLA confirms that the structure of the ESC is maintained each winter and the seasonal cycle is repeated every year, although the strength of the ESC shows large interannual variations. Seasonal and interannual variations in the ESC are discussed in relation to wind-driven circulation in the Sea of Okhotsk, using wind stress and wind stress curl fields derived from European Centre for Medium Range Weather Forecasts (ECMWF) reanalysis data and a scatterometer-derived wind product. Seasonal and interannual variations of the anticyclonic eddy in the Kuril Basin are also revealed using T/P SLA.     

广州科学城保利林语山庄高边坡支护工程的实践

主要介绍了广州科学城保利林语山庄高边坡支护设计方案与施工方法。支护方案综合采用了锚索、锚杆、抗滑桩、钢管桩、格构梁及挡土墙等多种支护方法，有效地提高了边坡的稳定性。应用有限元方法来验证设计方案的合理性，模拟结果与工程实践基本吻合。     

北太平洋阻塞的年际年代际变化及其与SST、遥相关及风暴路径的关系

利用NCEP／NCAR再分析资料，对1948／1949－1999／2000共52个冬季的北太平洋上空中纬度阻塞异常的气修特征进行了统计分析，小波分析和功率谱分析结果表明该区域阻塞发生的频数具有很明显的3－7年的年际振荡和年代际变化特征。同时2－7年带通平均的小波方差谱分析结果表明阻塞的这种年际变化的振幅存在着缓慢下降的趋势，且气候突变在20世纪70年代，这进一步证明了北太平洋上空的阻塞活动具有年代际变化特征。对强阻塞异常的冬季和弱阻塞异常的冬季分别进行合成分析，结果表明，对于阻塞异常强的冬季，北太平洋西向东北方向加强并分裂成两个中心，而SST异常在中纬度太平洋则对应着典型的PDO型，在赤道地区则为类La Nina型的海温分布。而对于阻塞异常弱的冬季则对应截然不同甚至相反的分布特征，即500hPa高度异常场表现为符号相反的PNA型，风暴路径中心在日界线附近呈纬向型分布。同时SST异常在赤道地区则为典型的El Nino型的海温分布。以上结果揭示出北太平洋阻塞活动的年际变化可能主要与热带海温的遥响应相联系，而年代际变化则主要与中纬度局地的PDO型海温及其通过斜压瞬变波的海－气相互作用有关。     

Petrology and Geochemistry of the Volcanic Rocks Dredged from the Geophysicist Seamount in the Kurile Basin: Evidence for the Existence of Thinned Continental Crust

Dredged samples from the Geophysicist seamount volcano in the northeastern part of the Kurile Basin include volcanic and volcanoclastic rocks ranging from basalt to andesite. The rocks have geochemical features typical of high-K island-arc calc-alkaline volcanism. They are enriched in LILE and depleted in Zr, Ti, Nb, Ta and Y. The chondrite-normalized REE patterns are characterized by enrichment of LREE similar to those of island-arc lava from the submarine volcanoes of rear-arc zone of the Kurile Island Arc. The volcanic rocks have a wide range of ⁸⁷Sr/⁸⁶Sr ratios (0.70287-0.70652), varying ¹⁴³Nd/¹⁴⁴Nd and Pb isotopic ratios. Their trace-element compositions and Sr-Nd-Pb isotope signatures may be explained by a small addition of crustal continental component to mantle-derived magmas that suggest the existence of thinned continental basement under the eastern part of the Kurile Basin.     

1996年北半球主要环流特征及其影响

１９９６年北半球主要环流特征是：５００ｈＰａ西太平洋副高偏弱，脊线位置初夏偏北，盛夏西端持续偏南；亚洲西风带后冬至初春经向环流明显发展，７月亚洲中纬度地区常有阻塞形势维持，５００ｈＰａ青藏高原位势高度偏高，夏季南支印缅槽较弱。     

近30年夏季亚欧大陆中高纬度阻塞高压的统计特征

文中利用1970～2001年NCEP再分析500 hPa逐日高度场资料,根据阻塞高压的天气学定义,采用客观统计方法检索出近32 a亚欧中高纬度392个阻塞高压个例,对其进行了气候学分析.结果表明,亚欧中高纬地区夏季阻塞高压活动频繁,10 d以下的过程占绝对多数,地理分布主要集中在45～70°N之间,纬向上可划分5个高发区,其中乌拉尔山和贝加尔湖东部阻高活动频次最高,同时,每个区域中又存在着相应的阻高活跃区.亚欧中高纬地区夏季阻高活动具有明显的季节内变化特征.6月份,阻塞活动多发生在乌拉尔山地区和鄂霍次克海地区,以双阻为主要形势;7月份,欧洲区和贝加尔湖地区的阻塞活动有所增多,尤其贝加尔湖东部地区增多明显,而乌拉尔山地区的阻塞形势明显减少,鄂霍次克海地区的阻塞活动位置向北移动,多发生在60°N以北,双阻形势逐渐减弱,贝加尔湖地区的中阻形势有所增强.8月份,阻塞形势主要存在于贝加尔湖东西两区,中阻形势占据主导地位.亚欧中高纬地区夏季阻塞高压活动年际变化特征也很突出,且这种年际振荡有明显的地理差异.另外,研究表明亚洲北部的阻高活动多以稳定型为主,移动型阻高个例仅占6.6%.移动型阻高以起源于乌拉尔山地区最多,移距最长,生命期最长.偶极子类阻高多集中在贝加尔湖东部与乌拉尔山地区,约占该地区总阻高频次的62.0%和49.7%,平均生命期分别达到7 d/次和9 d/次以上.     

强厄尔尼诺事件下2016年1月中国南方超级寒潮的动力学机制:瞬变波对大气长波异常的调制

本文采用Plumb三维波活动通量和局地Eliassen-Palm通量诊断方法,利用欧洲中期天气预报中心的逐日再分析资料ERA-Interim,分析了超强厄尔尼诺背景下2016年1月下旬中国南方超级寒潮的动力学机制：瞬变波对大气长波异常的调制。前期2015年12月的北大西洋海表热通量正异常,有助于后期大西洋阻塞形势的维持。大气长波能量沿大圆路径从大西洋阻高经乌拉尔地区向东亚中低纬度传播并在此辐合,导致了乌拉尔阻高和华北横槽的经向结构,更多强冷空气聚集在异常偏南的纬向槽线附近。寒潮爆发前夕,2支瞬变波列活跃在亚欧大陆。北支瞬变波列调制了北方的大气长波,使横槽转竖;南支瞬变波列协同调控了南方的大气长波,使南支印缅槽减弱;两者共同作用,促使冷平流大举南下,直达华南沿海,南方寒潮发生。