Comparison of atmospheric forcing in four sub-arctic seas     

Muyin Wang  Nicholas A. Bond  James E. Overland 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2543

A comparative analysis was conducted on climate variability in four sub-arctic seas: the Sea of Okhotsk, the Bering Sea shelf, the Labrador Sea, and the Barents Sea. Based on data from the NCEP/NCAR reanalysis, the focus was on air–sea interactions, which influence ice cover, ocean currents, mixing, and stratification on sub-seasonal to decadal time scales. The seasonal cycles of the area-weighted averages of sea-level pressure (SLP), surface air temperature (SAT) and heat fluxes show remarkable similarity among the four sub-arctic seas. With respect to variation in climate, all four seas experience changes of comparable magnitude on interannual to interdecadal time scales, but with different timing. Since 2000 warm SAT anomalies were found during most of the year in three of the four sub-arctic seas, with the exception of the Sea of Okhotsk. A seesaw (out of phase) pattern in winter SAT anomalies between the Labrador and the Barents Sea in the Atlantic sector is observed during the past 50 years before 2000; a similar type of co-variability between the Sea of Okhotsk and the Bering Sea shelf in the Pacific is only evident since 1970s. Recent positive anomalies of net heat flux are more prominent in winter and spring in the Pacific sectors, and in summer in the Atlantic sectors. There is a reduced magnitude in wind mixing in the Sea of Okhotsk since 1980, in the Barents Sea since 2000, and in early spring/late winter in the Bering Sea shelf since 1995. Reduced sea-ice areas are seen over three out of four (except the Sea of Okhotsk) sub-arctic seas in recent decades, particularly after 2000 based on combined in situ and satellite observations (HadISST). This analysis provides context for the pan-regional synthesis of the linkages between climate and marine ecosystems.  相似文献   

普里兹湾水体悬浮颗粒物天然15N     

刘广山  黄奕普  陈敏  邱雨生 《台湾海峡》2005,24(3):265-273

本文研究了南极普里兹湾海域悬浮颗粒物中的天然15N丰度,并就δ15N与POC、PON等生化要素之间的相关性进行了讨论,对δ15N含量分布特征的形成机制及其与物理、生物学过程的耦合进行了探讨,给出了南极普里兹湾悬浮颗粒物中的δ15N与POC、PON含量呈负相关关系;表层水中δ15N、POC和PON的分布和δ15N的垂直分布可能与涡流有关.  相似文献   

Remineralization and accumulation of organic carbon and nitrogen in marine sediments of eutrophic bays: the case of the Bay of Concepcion, Chile     

Laura Farías   《Estuarine, Coastal and Shelf Science》2003,57(5-6):829-841

The Bay of Concepcion (36°40′S; 73°02′W) is a semi-enclosed and shallow embayment in which biogeochemical processes are seasonally coupled to coastal upwelling during the austral spring and summer. The nutrient cycle in the bay is complex due to the combined effects of a pronounced O₂ minimum layer and high nutrient concentrations both originating from subsurface equatorial water during coastal upwelling and a rapid rate of sediment nutrient recycling. The sediments are characterized by a high content of organic matter mainly due to the extremely high rates of phytoplankton production and deposition. During the upwelling period, a black flocculent layer frequently covers the sediment–water interface in the inner part of the bay where an extensive mat of Beggiatoa spp. develops. Three approaches are used to analyse the extent to which the benthic system recycles or retains nutrients at two stations, located at the centre (station C, St. C) and mouth (station B, St. B) of the bay for a 1-year period (March 1996–1997): (1) estimation of C and N remineralization rates based on SO₄²⁻ reduction measurements, (2) calculation of C and N turnover rates using a diagenetic model applied to total organic carbon and total nitrogen vertical distributions and, (3) construction of C and N budgets from direct measurements of sedimentation (from a sediment trap) and estimates of the C and N burial rates. Depth-integrated SO₄²⁻ reduction rates varied between 3.4 (winter) and 25.5 (summer) mmol m⁻² d⁻¹. Estimated C and N oxidation rates ranged between 7.9 and 87.8 mol C m⁻² yr⁻¹ and between 0.9 and 6.9 mol N m⁻² yr⁻¹, respectively. Each approach yielded minor differences in the C and N remineralization rates (and also minor differences between both studied stations), except when the kinetic model was applied to C and N distribution without including the presence of the flocculent layer. The rates of carbon oxidation and sulphate reduction were considerably higher than in other coastal sediments with similar depositional regime. The C and N burial rates were 2.23 and 0.21 (St. C) and 1.30 and 0.09 (St. B) mol m⁻² yr⁻¹, respectively. The C/N ratio of the buried fraction was ca. 10.6 at St. C and 14.4 at St. B. Because the observed differences in burial rates could not be ascribed to distinctive depositional (both stations have similar sediment accumulation rates) and oceanographic (similar O₂ concentration and hydrography) conditions, differences may be due to in part spatial heterogeneity in the supply of organic matter. The degree of preservation of organic matter as plankton detritus and nitrogen accumulating bacterial biomass associated with Beggiatoa spp. at St. C may also be involved.  相似文献   

Correction to manuscript “Recharge velocity and geochemical evolution for the Permo-Triassic Sherwood Sandstone, Northern Ireland” [Journal of Hydrology 315 (2005) 308–324]     

J.A.C. Barth  A.A. Cronin 《Journal of Hydrology》2006,330(3-4):763-764

  相似文献   

干旱内陆流域景观格局变化下的景观土壤有机碳与氮源汇变化   总被引：2，自引：2，他引：2  

王根绪  卢玲  程国栋 《第四纪研究》2003,23(3):270-279

以黑河流域中游绿洲区域为例,近10年来,在干旱内陆流域受人类活动强烈影响的区域,景观的破碎度降低,景观异质性减弱,显著的景观变化表现在:耕种景观与荒漠化景观的扩张和沼泽草甸景观与水域景观的萎缩,其中荒漠草原景观面积的10%、山地草原景观的49.8%以及沼泽草甸(包括盐化草甸)景观面积的16.8%演变为耕种景观类型;相反,17.4%的荒漠草原景观面积和20.2%的沼泽草甸退化为沙漠与戈壁景观,另有13.02%的灌耕地面积演变为荒漠草原.景观空间格局演变驱动景观土壤N、C的源汇变化,近10年来,黑河流域中游地区由于景观空间格局变化形成的景观N净排放和有机C净释放分别达到50.65×104T和530.17×104T.山地草原景观的荒漠化与耕种利用、耕种景观的荒漠草原化、沼泽草甸与山地草甸景观以及荒漠草原景观的耕种利用和这些景观的沙漠化发展是造成区域N、C损失的主要途径.  相似文献   

青藏高原南北向地堑系的实验研究   总被引：8，自引：0，他引：8  

潘裕生  钟嘉猷  周勇 《地质科学》2003,38(2):172-178,213

青藏高原南北向正断层及与其伴生的地堑是当前的热门话题。对其成因的认识分歧颇大,它们与高原隆升的关系则还处于推论阶段。本文用模拟实验的方法检验了其中的主要观点,结果表明:南北向正断层及与其伴生的地堑是南北向挤压的结果,是在挤压中期横张裂隙的基础上发展起来的。因此,它不代表高原已抬升到了最大高度后的塌陷,而是伴随高原隆升过程中的产物。  相似文献   

浅层砂岩地震勘探技术   总被引：2，自引：0，他引：2  

巫芙蓉  蒋骥  张晓斌  张翠兰  熊艳 《物探化探计算技术》2003,25(2):135-139

从影响浅层资料质量的主要因素出发，结合浅层砂岩地震勘探在川西地区中的一些实例，对浅层砂岩地震勘探方法作了分析和探讨，从中总结出了一套适合于浅层砂岩地震勘探的采集、处理、解释技术，且实际应用效果较好。  相似文献   

地下水硝酸盐中氮、氧同位素研究现状及展望   总被引：11，自引：0，他引：11  

朱琳  苏小四 《世界地质》2003,22(4):396-403

农业区内浅层地下水中硝酸盐污染普遍存在。为保证供水安全和有效治理污染的地下水体。确定硝酸盐中氮的来源及影响硝酸盐浓度的物理、化学作用尤为重要。由于不同成因的硝酸盐中δ^15N值存在差异，利用N同位素可以确定氮污染源，但有时存在多解性问题；分析硝酸盐的δ^18O值，可提高地下水硝酸盐污染的研究深度。本文综述了用硝酸盐中N、O同位素来区分地下水污染中硝酸盐的不同来源和示踪氮循环过程这两方面的研究进展，并提出一些值得重视的研究方向。  相似文献   

The neutral carbon distribution in a bipolar outflow/molecular disc source configuration: G35.2−0.74N     

Little  Kelly  & Murphy 《Monthly notices of the Royal Astronomical Society》1998,294(1):105-117

Maps are presented of ³ P ₁→³ P ₀[C  i ] and J =2→1 C¹⁸O line emission from the interstellar molecular cloud G35.2−0.74N. The maps are interpreted with reference to a previous model for the structure of the cloud in which opposing jets from a central object, embedded in a rotating interstellar disc, precess and drive a bipolar molecular outflow. The C¹⁸O emission traces the rotating interstellar disc, but the [C  i ] emission shows several features. An unresolved component is observed which probably results from dissociation of CO in the centre of the disc by UV radiation from the central source. Background [C  i ] emission is also observed which shares the rotation of the disc on larger scales. The C  i /CO ratio in these components is typically a few per cent. High-velocity [C  i ] emission, where C  i /CO is high (>0.1–0.4), is observed between the CO molecular outflow and the cavity exacavated by the jet. This material has probably been accelerated by the jet but dissociated by far-UV radiation propagating through the cavity. The C  i /CO ratio falls as the shocked outflow later sweeps up CO.  相似文献   

An elliptic problem with integral constraints with application to large-scale geophysical flows     

A.J. Meir  Irad Yavneh 《Computational Geosciences》1998,2(4):337-346

We present a weak formulation of a non-standard elliptic equation whose boundary values are determined in part by integral relations. Existence and uniqueness of its solution are proved, and a finite element discretization is described, analyzed, and implemented on a test problem. The equation is a generalization of one that is solved during integration of the three-dimensional Quasigeostrophic equations, which model large-scale rotating stratified flows, where the integral constraints represent conservation of physical properties.  相似文献