Seasonal climatologies of oxygen and phosphates in the Bering Sea reconstructed by variational data assimilation approach     

Gleb Panteleev  Vladimir Luchin  Nikolay P. Nezlin  Takashi Kikuchi 《Polar Science》2013,7(3-4):214-232

Climatological fields of dissolved oxygen and phosphates in the Bering Sea during the spring, summer, and fall seasons were generated on the basis of an extensive dataset of hydrochemical observations (16,356 stations, beginning in 1928) and a novel 3D variational algorithm for interpolation of a passive ocean tracer. The resulting patterns comply with maps produced earlier using an optimal interpolation method, though they also provide more detail and contain no “missing data” regions. Vertical, spatial, and temporal variability of both parameters follow large-scale patterns of circulation, upper mixed layer depth, and phytoplankton productivity in the Bering Sea.  相似文献   

Last glacial maximum ecology and climate from terrestrial gastropod assemblages in Peoria loess,western Kentucky     

David A. Grimley  Ronald C. Counts  Jessica L. Conroy  Hong Wang  Sarah N. Dendy  Catherine B. Nield 《第四纪科学杂志》2020,35(5):650-663

The Rocks loess section, in unglaciated western Kentucky, provides a high-resolution environmental record during the last glacial maximum onset. The Peoria Silt (9 m thick) contains 26 terrestrial gastropod species, with up to 15 species within a single 5 cm interval. Thirteen radiocarbon ages, using shells or charcoal, range between 30 and 24.5 cal ka; younger loess has been leached or eroded. Stratigraphic shifts in gastropod assemblages imply significant cooling, particularly ~27 cal ka, as solar insolation was decreasing and the southern Laurentide Ice Sheet rapidly advancing. Midwestern to southern species (e.g. Anguispira kochi, Gastrocopta pentodon, Hawaii miniscula, Helicodiscus parallelus, Vallonia perspectiva) occur only in the lowermost Peoria Silt (~30–27 cal ka). In contrast, cold-tolerant species (Columella alticola, Vertigo modesta, Vallonia gracilicosta) occur only in full glacial Peoria Silt (27–24.5 cal ka). Inferred mean July temperatures, from mutual climatic range methods, range from ~23 °C at 30 cal ka, cooling to ~18 °C by 26 cal ka; about 3–8 °C cooler than today (~26 °C). Superimposed on this cooling trend are multi-centennial variations in detrital carbonate, fossil shell concentrations, palaeotemperature estimates, and oxygen isotope values (Vertigo, Discus, Helicodiscus). The finer-scale variations imply relatively synchronous fluctuations in glacial sediment supply, loess sedimentation, and climate.  相似文献   

Spatiotemporal pattern of gypsum blooms in the Salton Sea,California, during 2000-2018     

《International Journal of Applied Earth Observation and Geoinformation》2020

Algal blooms and the resulting deterioration of water quality have threatened the environmental health of inland lakes. This study investigated the spatiotemporal dynamics of gypsum blooms in the Salton Sea, the largest inland water body in California. An innovative gypsum bloom index (GI) was proposed to detect gypsum blooms based on Moderate Resolution Imaging Spectroradiometer (MODIS)/Terra data for three bands (469, 555, and 859 nm) during 2000–2018. Discoloration (from green to reddish brown) was observed in the gypsum bloom-infested waters mapped using the hue, saturation, and value (HSV) color model. We found that: (1) the GI is able to effectively map gypsum blooms in the Salton Sea with a relatively high accuracy (85 %); (2) the largest gypsum bloom area was observed in summer (August and September), with notable gypsum blooms lasting more than 40 days in 2003, 2005, 2006, 2016, and 2018; (3) the gypsum bloom-infested waters shifted from the center to the southeastern shore of the lake during 2003–2018, and the frequency of gypsum blooms significantly increased since 2008. Meanwhile, the temporal and spatial differences between the northwestern and southeastern lake increased over the observation period; and (4) discoloration occurred in the gypsum bloom-infested waters and lasted for 14 days on average, longer periods of discoloration (more than 20 days) occurred d in 2002, 2016, and 2018. The reconstruction of gypsum bloom dynamics in the Salton Sea provides valuable information for the practical management and restoration of the Salton Sea.  相似文献   

黄河流域降水稳定同位素的云下二次蒸发效应          下载免费PDF全文

车存伟  张明军  王圣杰  杜勤勤  邱雪  马荣 《干旱区地理》2019,42(4):790-798

雨滴从云底降落到地面过程的云下二次蒸发现象会影响雨滴中的同位素比率，明确降水过程中稳定同位素的变化对研究流域水循环具有重要意义。基于全球降水同位素网络（GNIP）、相关文献同位素数据以及气象数据，首先建立局地大气水线（LMWL）定性分析了黄河流域云下二次蒸发与各气象要素间的关系，其次运用改进的Stewart模型定量计算了蒸发剩余比（f）和云底降水与地面降水的D-excess之差（Δd）。结果表明：（1） 黄河流域LMWL方程为：δ²H=7.01δ¹⁸O+1.25（n=293，R²=0.92），斜率和截距相比GMWL均较小，说明雨滴在下落过程中受到云下二次蒸发的影响。其中0～10 mm的降雨事件对云下二次蒸发影响显著；气温越高，或者水汽压、相对湿度越小，云下二次蒸发越强烈。（2） 季节变化上，从春季到冬季， f和Δd逐渐增大，云下二次蒸发逐渐减小。空间变化上，蒙甘区、蒙中区、晋陕甘区和渭河区的西安，年际间云下二次蒸发变化较大，而青南区、祁连-青海湖区、渭河区的平凉、长武、华山和鲁淮区年际差异较小。（3） 降水中Δd和f之间的线性关系在不同气象要素范围内有不同的数值，由于不同区域各气象条件存在差异，因此在应用经验公式时需考虑研究区的具体气象条件。  相似文献   

几种环境因子对皱纹盘鲍的胁迫作用及其阈值     

魏姗姗  罗冬莲  许翠娅  杨妙峰  郑盛华  郑惠东  陈月忠  钱小明 《海洋科学》2018,42(12):47-54

针对福建等海域养殖皱纹盘鲍度夏死亡率高的现象,试验研究了不同盐度、温度和溶解氧条件,对皱纹盘鲍幼鲍和1龄鲍死亡率的影响,并根据试验结果设定了皱纹盘鲍海上养殖盐度、温度和溶解氧预警阈值。结果表明:低盐胁迫对皱纹盘鲍的死亡率影响显著,在水温24～27℃时,盐度20是幼鲍和1龄鲍试验组和对照组死亡率有显著差异的临界点,盐度预警阈值为22;高温胁迫对皱纹盘鲍的死亡率影响显著,温度28℃是幼鲍和1龄鲍试验组和对照组死亡率有显著差异的临界点,温度预警阈值为27℃;皱纹盘鲍有较强的耐低氧能力,在水温26℃,盐度为30,溶解氧低于2.0mg/L时,开始大量死亡,溶解氧预警阈值为3.5mg/L;高温胁迫和低盐胁迫对皱纹盘鲍的死亡率有显著的交互作用,温度升高,低盐耐受能力下降。  相似文献   

藻类生长对沉积物上磷迁移转化的影响     

李苓  王彦  郭智俐  曹晓燕 《中国海洋大学学报(自然科学版)》2020,50(3):88-94

通过模拟中肋骨条藻(Skeletonema costatum)和沉积物共存体系,探究了富营养化条件下,藻类与沉积物对无机磷的吸收/吸附作用的相互影响。采用自制的金汞伏安微电极测定了藻与沉积物共存体系中溶解氧(DO)的含量变化,分析了体系中溶解氧含量变化与磷消耗速率以及沉积物中磷形态分布变化之间的关系。结果表明,在本课题研究范围内,共存的藻类与沉积物互相影响彼此对磷的消耗过程,1.0×10^4、5.0×10^4和1.0×10^5 cells/mL三种初始藻密度的中肋骨条藻(Skeletonema costatum)48 h后对磷的吸收百分比分别达54.7%、73.4%、93.8%,添加沉积物后分别降至21.3%、34.1%和51.9%;沉积物对培养基介质中的无机磷的吸附百分比为42.5%,加入三种不同藻密度的藻体后分别降至9.1%、2.8%及0.3%。高密度藻与沉积物共存体系的耗磷速率与体系DO含量呈显著负相关(p<0.05)。体系中DO浓度降低会促进沉积物中Fe-P向水体中释放,从而导致沉积物中铁结合态磷(Fe-P)含量的降低。可交换态磷(Ex-P)、有机磷(OP)和Fe-P是藻类存在时沉积物向水体中较易释放的形态。  相似文献   

大连市负氧离子浓度分布及预测模型的建立   总被引：6，自引：1，他引：5       下载免费PDF全文

丛菁  孙立娟 《气象与环境学报》2010,26(4):44-47

利用2008—2009年大连市逐日负氧离子实况资料,分析了负氧离子季、月和日变化特征及其与相关气象要素的关系。结果表明：负氧离子浓度具有明显的季节变化,冬季最大,夏季最小;而气温和PM10等是影响大连市负氧离子浓度的关键因素。运用逐步回归方法,求得各季节负氧离子的预报方程,实现了预报的定量化。经检验,预报方程效果显著,在预报业务中具有实际参考价值。  相似文献   

On the significance of wind event frequency for particulate resuspension and light attenuation in coastal waters     

F. Verspecht  C. Pattiaratchi 《Continental Shelf Research》2010

Wind-induced resuspension of particulate matter was investigated in a shallow coastal region off southwestern Australia, chosen for its isolation from the complexity of other confounding physical processes. The site had negligible river discharge, low nutrient concentrations and was largely devoid of tidal currents. Moorings were deployed in the micro-tidal waters to measure current speed, wave parameters, backscatter, subsurface irradiance and dissolved oxygen concentration. Two contrasting sites were chosen as representative of high and low wave-energy environments. Turbulent kinetic energy, recorded by the instruments, was dominated by the wind-wave signal. During wind events, at the most exposed site, bed shear stress exceeded the critical stress required to lift and resuspend sediments. At the most enclosed site, bed shear stresses only exceeded the critical stress required to suspend less dense material such as benthic fluff. Wind-waves were found to be the dominant mechanism driving the vertical redistribution of particulate matter. Low frequency storm events and high frequency (daily) sea breezes were found to differ significantly in their retention of particulate matter suspended in the water column. Long periods of calm generally followed the passage of a storm, allowing suspended particulate matter to settle out, while consecutive daily sea breezes were more effective in holding particulate matter in suspension. Linear correlations were found between the backscatter (a proxy for suspended particulate matter), light attenuation and dissolved oxygen concentration. Approximately half the variability in dissolved oxygen concentration could be attributed to the variability in light attenuation, with a decline in concentration during wind resuspension events. Variability in dissolved oxygen concentration was interpreted as a possible indicator of the moderation of pelagic phytoplankton productivity during wind events.  相似文献