Changes in ocean ventilation during the 21st Century in the CCSM3

Changes in the ventilation rate of the global ocean during the 20th and 21st centuries, as indicated by changes in the distribution of ideal age, are examined in a series of integrations of the Community Climate System Model version 3. The global mean age changes little in the 20th Century relative to pre-industrial conditions, but increases in the 21st Century, by an amount that is independent of the range of climate forcings considered. The increase is primarily due to a decrease in the ventilation rate of Antarctic Bottom Water (AABW), and to a lesser degree, North Atlantic Deep Water (NADW). Changes in a regional volumetric census of age indicate that the changes in AABW are predominantly for waters that are already older than 100 years, so will likely have a moderate direct feedback on oceanic uptake of CO₂ and other tracers. On the other hand, the changes in NADW occur most strongly in waters that are a few decades old, so are more likely to have a feedback on the climate system. While the global mean age increases, the age does not increase everywhere in the ocean. Regions newly exposed to strong atmospheric forcing as sea ice retreats experience an increase in convection and decreasing age. Age also decreases over a large volume of the lower thermocline as the rate of upwelling of old deep water decreases with the weakening of the thermohaline circulation.     

Diagnosis of the sediment transport in the Belgian Coastal Zone

Estimating the age of particles in marine environment constitutes an invaluable tool to understand the interactions between complex flows and sediment dynamics, particularly in highly energetic coastal areas such as the Belgian Coastal Zone (Southern Bight in the North Sea). To this end, the Constituent Age and Residence time Theory – CART – introduced by Delhez, E.J.M., Campin, J.-M., Hirst, A.C., Deleersnijder, E. [1999a. Toward a general theory of the age in ocean modelling. Ocean Modelling 1, 17–27] for passive water constituents is extended to describe the sediment dynamics. It is then used in combination with a three-dimensional coupled hydrodynamic-sediment transport model to investigate sediment processes in the Belgian Coastal Zone focusing on two complementary aspects of the sediment dynamics: the internal sediment motion and redistribution within the Belgian coast; and the horizontal transport.     

闽江口拦门沙砂体的演变及其沉积年代

本文介绍了闽江口拦门沙砂体的~(14)C年代、沉积速率、堆积趋势及其变化,从历史的演变规律推测现代闽江口拦门沙砂体堆积的可能发展趋势,指出航道整治的重点地段。     

Age and growth of bluenose,Hyperoglyphe antarctica (Pisces: Stromateoidei) from the lower east coast,North Island,New Zealand

Growth of the bluenose, Hyperoglyphe antarctica (Carmichael, 1818) from the lower east coast, North Island, was determined by counting growth check rings in otoliths. One growth check ring appeared to be laid down each year, so this technique is probably valid for aging bluenose. Female fish had a significantly higher growth rate than males. Comparisons of samples from three sites indicated no significant regional differences in growth. The von Bertalanffy parameters L8,K, and t0 fitted to back‐calculated fish lengths were, respectively, 81.1 cm, 0.308, ‐0.627 for males, and 86.1 cm, 0.308, ‐0.384 for females.     

台湾海峡西岸闽江口和九龙江口沉积物中碎屑锆石铀-铅定年及物源意义

碎屑锆石能较好保存源区岩石组成的信息,其铀-铅年龄是沉积物源区示踪有效的方法。利用激光剥蚀等离子体质谱和多接收器等离子体质谱联机(LA-MC-ICPMS)技术,对台湾海峡西部闽江口和九龙江口沉积物中的碎屑锆石进行原位铀-铅测年,同时获得锆石的微量元素。研究表明大部分碎屑锆石的钍与铀含量之比值大于0.1,稀土元素球粒陨石标准化配分曲线呈左倾型,并具有明显的铈含量正异常和铕含量负异常,结合阴极发光图像表明这些锆石绝大部分为岩浆成因。闽江口和九龙江口的碎屑锆石具有相同的印支期(峰值为236 Ma)、燕山早期(峰值为155 Ma)和燕山晚期(峰值为110 Ma)等3个峰值,这三期碎屑锆石占主要部分,反映闽江口和九龙江口碎屑沉积物主要来自各流域上游印支期和中下游燕山期岩体,而闽江口碎屑锆石具有明显的加里东期峰(峰值为465 Ma)和前寒武纪(553~2 765 Ma)较多的碎屑锆石,这些碎屑物质可能来自上游武夷山地区加里东期和前寒武纪基底的物质。对比闽江口碎屑锆石铀-铅年龄与台湾岛西部海滨沙滩(苗栗-新竹、嘉义-台南)中的独居石年龄具有相似的谱峰特征,表明台湾岛西部海滨沙滩碎屑物质可能有部分来自闽江。闽江口碎屑物质明显区别于福建的九龙江和浙江的瓯江,这为判别台湾海峡沉积物的物质来源提供可靠的依据。     

潮汐驱动下的辽东湾水动力及入海污染物输移特征

通过建立水动力学模型、物质输运模型和年龄模型,对渤海辽东湾潮汐驱动下的水动力状况和污染物输移扩散过程进行了数值模拟研究。结果表明,辽东湾海域入海径流对辽东湾整体流场和水交换过程影响不大,其主要影响集中在河口附近海域。在潮汐的驱动下,辽东湾内形成了复杂的环流结构,辽东湾南北海域分别存在顺时针、逆时针的环流,而辽东湾湾口又存在逆时针环流,使得水交换能力较弱,对辽东湾向外海的物质输运产生不利影响,湾顶附近海域的物质主要通过扩散过程与外海进行交换。年龄模型的计算结果表明,辽东湾河流入海污染物在河口附近停留时间较长,向远区的输运需要较长时间。入海污染物的影响具有局地性,对局部海域水质尤其是辽东湾湾顶的水质会产生不利影响。     

Life in the Slow Lane: Growth and Longevity of Cold-seep Vestimentiferans

Abstract. Yearly, in situ growth of two species of cold-seep vestimentiferan tubeworms was measured using a combination of banding and video analysis. A total of 53 animals from 15 different aggregations were included in the study, which was conducted over a Cyear period. The most common species, Lamellibrachia sp., grows very slowly (averaging 0.77 cm. a^-1) and yet commonly reaches lengths over 2 m. Based on conservative calculations we conclude that individuals in mature aggregations are a minimum of 100 a old and are likely to be much older. Smaller numbers of a second species of vestimentiferan (related to escarpids) were also monitored over this period. We consider it likely that the individuals of the second species banded for this study were already on the plateau of their growth curve, and that the very low average growth rates recorded here would lead to an overestimate of the ages of the individuals used in this study. However, life history considerations combined with the extremely low measured growth rates of this species suggest it is also long-lived.     

长江河口水流输运时间研究

利用水龄理论的新方法,借助环境水动力学模型定量讨论了多年平均径流条件下长江河口径流和潮汐作用对河口水流输运时间的影响。研究给出了长江河口水流输运时间的时空格局:多年平均流量条件下,水流从徐六泾输出至河口(122.5°E)大约需要24d,南、北槽分流口以上河段水流输运时间主要由径流控制,水流输运时间为8d,向下至拦门沙滩顶水域由径流和潮汐共同控制,水龄为16d,说明最大浑浊带区域的水流输运速度较上下游为慢,从一个侧面阐述了最大浑浊带区域水动力的特征;长江河口水流输运时间存在明显的层化现象,表底层相差最大值可达6d。数值模拟试验结果表明长江河口的潮汐作用是影响河口水流输运时间的关键要素,河口巨大的进潮量增强河口水流交换能力并减小水流输运时间,从而显著影响随水体运动的物质输运格局。水流输运时间研究,不仅可以成功应用于河口水动力环境的量化研究,而且可以为泥沙输运及污染物输运等环境变化研究提供动力的基础。     

东海产长木叶鲽的年龄与生长

研究了东海产长木叶鲽的年龄与生长等生物学特性。样品取自１９９６ 年４ 月～１９９８ 年１１月,日本以西底拖网渔业在长崎鱼市场上岸的渔获物共２ ５８４ 尾。采用耳石进行年龄鉴定。体长与耳石径的关系,雌雄间有显著性差异。耳石上轮纹每年１～３ 月份形成一次。周龄的推定体长,５＋ 龄以上,雌性偏大     

The influence of wind on the water age in the tidal Rappahannock River

Wind plays an important role in regulating mixing/stratification, estuarine circulation, and transport timescale in estuaries. A three-dimensional model was used to investigate the effect of wind on transport time by using the concept of water age (WA) in the tidal Rappahannock River, a western tributary of the Chesapeake Bay, USA. The model was calibrated for water level, current, and salinity. A series of experiments regarding the effects of wind on WA was conducted under various dynamic conditions. The effect of wind on transport timescale depends strongly on the competition between the wind and buoyancy forcings, and on the pre-status of the circulation. A down-estuary wind generally decreases WA along the estuary. An up-estuary wind increases WA substantially because it changes the vertical mixing and estuarine circulation more significantly. When the buoyancy forcing increases, the up-estuary wind effect decreases whereas the down-estuary wind effect increases. A 2-day period wind pulse with a maximum speed of 15 m s⁻¹ can alter WA for 3 days; but the wind influence on WA lasts up to 40 days in the simulation. Both local and non-local wind forcings alter WA distribution. The local wind enhances vertical mixing and changes the gravitational circulation in the downstream portion of the estuary whereas it enhances transport in the freshwater portion of the estuary. Consequently, the local wind has a significant impact on WA distribution. In contrast, the non-local wind does not change the gravitational circulation significantly by imposing setup (setdown) of water level at the open boundary, resulting in a lesser impact on WA distribution.