Stream temperature response to variable glacier coverage in coastal watersheds of Southeast Alaska   总被引：1，自引：0，他引：1       下载免费PDF全文

Jason B. Fellman  Sonia Nagorski  Sanjay Pyare  Andrew W. Vermilyea  Durelle Scott  Eran Hood 《水文研究》2014,28(4):2062-2073

We measured stream temperature continuously during the 2011 summer run‐off season (May through October) in nine watersheds of Southeast Alaska that provide spawning habitat for Pacific salmon. The nine watersheds have glacier coverage ranging from 0% to 63%. Our goal was to determine how air temperature and watershed land cover, particularly glacier coverage, influence stream temperature across the seasonal glacial meltwater hydrograph. Multiple linear regression models identified mean watershed elevation (related to glacier extent) and watershed lake coverage (%) as the strongest landscape controls on mean monthly stream temperature, with the weakest (May) and strongest (July) models explaining 86% and 97% of the temperature variability, respectively. Mean weekly stream temperature was significantly correlated with mean weekly air temperature in seven streams; however, the relationships were weak to non‐significant in the streams influenced by glacial run‐off. Streams with >30% glacier coverage showed decreasing stream temperatures with rising summer air temperatures, whereas those with <30% glacier coverage exhibited summertime warming. Glaciers also had a cooling effect on monthly mean stream temperature during the summer (July through September) equivalent to a decrease of 1.1 °C for each 10% increase in glacier coverage. The maximum weekly average temperature (an index of thermal suitability for salmon) in the six glacial streams was substantially below the lower threshold for optimum salmon growth. This finding suggests that although glaciers are important for moderating summer stream temperatures, future reductions in glacier run‐off may actually improve the thermal suitability of some glacially dominated streams in Southeast Alaska for salmon. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Polychlorinated biphenyl (PCB) concentrations and congener composition in masu salmon from Japan: A study of all 209 PCB congeners by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS)     

Reiko Matsumoto  Nguyen Phuc Cam Tu  Shinsuke Haruta  Masahide Kawano  Ichiro Takeuchi 《Marine pollution bulletin》2014

We collected two subspecies of masu salmon: Oncorhynchus masou masou from four localities (southern Sea of Japan northward to Hokkaido) and O. masou ishikawae from upstream from Ise Bay close to a heavy industrial area. All 209 PCB congeners were analyzed using HRGC/HRMS. PCA ordination of congener concentrations divided data into three groups: (i) ssp. masou from Hokkaido, (ii) ssp. masou from the other regions and (iii) ssp. ishikawae. The highest ∑ PCB concentration (40.39 ng/wet wt) was in ssp. ishikawae followed by ssp. masou from southern waters; however the TEQ_{dioxin-like PCBs} was highest in ssp. masou from southern water (1.96 pg-TEQ_{dioxin-like PCBs}/g wet wt.) due to the high proportion of congener #126 in its complement (#126 has the highest toxic equivalency factor among congeners). There is likely a contamination source offshore in the southern Sea of Japan and/or along the migratory route of ssp. masou.  相似文献   

ATLANTIC SEA SURFACE TEMPERATURES AND NEW ENGLAND SNOWFALL     

SUZANNE HARTLEY 《水文研究》1996,10(12):1553-1563

This paper examines the possibility of an association between winter (December–March) snowfall in New England and sea surface temperature anomalies (SSTAs) in the adjacent Atlantic Ocean. Regional snowfall indices for southern and northern New England were obtained by rotated principal components analysis (PCA). Composite maps of winter Atlantic SSTAs and 700-mb geopotential height anomalies were generated for cases of above and below average winter snowfall totals for southern and northern New England, respectively. A monthly index of SSTAs around the coast of New England was obtained from rotated PCA of SSTAs in the western Atlantic Ocean and compared for high snow and low snow cases. In northern New England, no direct association between snowfall and SSTAs is indicated by either the composite maps or the monthly SSTA index — high or low snowfall totals can be attributed primarily to anomalies in the 700-mb circulation. In southern New England, high (low) snowfall totals are associated with negative (positive) SSTAs off the Atlantic coast, and these anomalies are often already evident in December, suggesting Atlantic sea surface temperatures may be of utility in long-range winter forecasts for coastal regions.  相似文献   

Aragonite preservation in late Quaternary sediment cores on the Brazilian Continental Slope: implications for intermediate water circulation     

S. Gerhardt  H. Groth  C. Rühlemann  R. Henrich 《International Journal of Earth Sciences》2000,88(4):607-618

We present late Quaternary records of aragonite preservation determined for sediment cores recovered on the Brazilian Continental Slope (1790–2585 m water depth) where North Atlantic Deep Water (NADW) dominates at present. We have used various indirect dissolution proxies (carbonate content, aragonite/calcite contents, and sand percentages) as well as gastropodal abundances and fragmentation of Limacina inflata to determine the state of aragonite preservation. In addition, microscopic investigations of the dissolution susceptibility of three Limacina species yielded the Limacina Dissolution Index which correlates well with most of the other proxies. Excellent preservation of aragonite was found in the Holocene section, whereas aragonite dissolution gradually increases downcore. This general pattern is attributed to an overall increase in aragonite corrosiveness of pore waters. Overprinted on this early diagenetic trend are high-frequency fluctuations of aragonite preservation, which may be related to climatically induced variations of intermediate water masses. Received: 9 November 1998 / Accepted: 25 August 1999  相似文献   

Offshore Transport of Pesticides in the South Atlantic Bight: Preliminary Estimate of Export Budgets     

Henry A. Alegria  J. Pierre d''Autel  Timothy J. Shaw   《Marine pollution bulletin》2000,40(12):1178-1185

Surface waters of the inner shelf (coast to 20-m isobath) of the South Atlantic Bight (SAB) were sampled in July 1994 and August 1995 for pesticides currently used in the south-eastern United States to estimate offshore transport. Only atrazine was detected at all stations in 1994 and 1995 and simazine was detected at all stations in 1995. Atrazine levels were 5.60–12 ng/l in July 1994 and 3.1–11 ng/l in August 1995 and simazine levels were 0.8–4.6 ng/l in August 1995. We calculated reservoir masses (in inner shelf waters) of 550 kg atrazine in July 1994, and 325 kg atrazine and 180 kg simazine in August 1995. Using these reservoir masses and a previously estimated residence time for waters of the inner shelf of 30 days, annual export budgets were calculated. For 1994, a budget of 6600 kg atrazine was calculated. For 1995, budgets of 3900 kg atrazine and 2150 kg simazine were calculated.

Yearly riverine discharge to estuaries in the study region was estimated to range from 600 to 5600 kg atrazine and 100 to 550 kg simazine. The large budgets for the coastal inner shelf compared with yearly riverine discharge suggest that a significant fraction of atrazine and simazine applied in the region is being transported offshore from coastal waters. This transport pathway needs to be factored in when calculating mass balances and determining the ultimate fate of these pesticides.  相似文献   

Influence of the NAO on Wintertime Surface Air Temperature over East Asia: Multidecadal Variability and Decadal Prediction     

Jianping LI  Tiejun XIE  Xinxin TANG  Hao WANG  Cheng SUN  Juan FENG  Fei ZHENG  Ruiqiang DING 《大气科学进展》2022,39(4):625-642

In this paper,we investigate the influence of the winter NAO on the multidecadal variability of winter East Asian surface air temperature(EASAT)and EASAT decadal prediction.The observational analysis shows that the winter EASAT and East Asian minimum SAT(EAmSAT)display strong in-phase fluctuations and a significant 60-80-year multidecadal variability,apart from a long-term warming trend.The winter EASAT experienced a decreasing trend in the last two decades,which is consistent with the occurrence of extremely cold events in East Asia winters in recent years.The winter NAO leads the detrended winter EASAT by 12-18 years with the greatest significant positive correlation at the lead time of 15 years.Further analysis shows that ENSO may affect winter EASAT interannual variability,but does not affect the robust lead relationship between the winter NAO and EASAT.We present the coupled oceanic-atmospheric bridge(COAB)mechanism of the NAO influences on winter EASAT multidecadal variability through its accumulated delayed effect of~15 years on the Atlantic Multidecadal Oscillation(AMO)and Africa-Asia multidecadal teleconnection(AAMT)pattern.An NAO-based linear model for predicting winter decadal EASAT is constructed on the principle of the COAB mechanism,with good hindcast performance.The winter EASAT for 2020-34 is predicted to keep on fluctuating downward until~2025,implying a high probability of occurrence of extremely cold events in coming winters in East Asia,followed by a sudden turn towards sharp warming.The predicted 2020/21 winter EASAT is almost the same as the 2019/20 winter.  相似文献   

Aeolization on the Atlantic coast of Galicia (NW Spain) from the end of the last glacial period to the present day: Chronology,origin and evolution of coastal dunes linked to sea-level oscillations     

Carlos Arce Chamorro  Juan Ramón Vidal Romaní  Aurora Grandal d'Anglade  Jorge Sanjurjo Sánchez 《地球表面变化过程与地形》2023,48(1):198-214

The Atlantic coast of Galicia (NW Spain) is a high-energy environment where shingle beaches are currently developing. These coarser sediments alternate with sandy deposits which are also considered as beaches typical of a low-energy environment. The physical association of both types of sediment with contrasted sedimentary significance raises problems of interpretation. The study of four outcrops of fossil aeolianites on this coast has allowed us to reconstruct their evolution from the end of the Upper Pleistocene to the present day. Their chronology, estimated by optically stimulated luminescence between 35 and 14 ky at the end of the last glaciation (MIS2), coincides with a local sea level 120 m below the present one. This implies a coastline shifted several kilometres from its current location and the subaerial exposure of a wide strip of the continental shelf covered by sands. The wind blew sand to form dunes towards the continent, covering the coastal areas, which then emerged with no other limitation than the active river channels. Sea-level rise during the Holocene transgression has progressively swamped these aeolian deposits, leaving only flooded dunes, relict coastal dunes and climbing dunes on cliffs up to 180 m high. The aeolian process continued as long as there was a sandy source area to erode, although accretion finished when the sea reached its current level (Late Holocene). Since then, the wind turned from accretion to erosion of the dunes and sand beaches. This erosion exposes the older shingle beaches (probably of Eemian age) buried under the aeolian sands, as well as old, submerged forest remains and megalithic monuments. The destruction of sand beaches and dunes currently observed along the Galician coast is linked, according to most researchers, to anthropogenic global warming. However, their management should consider these evolutive issues.  相似文献   

用TOPEX/POSEIDON高度计数据分析热带大西洋海面高度距平的低频变化     

邱云  胡建宇 《海洋科学》2006,30(6):59-65

利用1992年10月~2002年7月的TOPEX/POSEIDON(T/P)卫星高度计月平均格点数据分析了热带大西洋(15°S~25°N,5°~50°W)海面高度距平的低频变化。由热带大西洋大约10 a海面高度距平变化的标准差分析得到:在赤道附近海区(2°~5°N,25°~45°W)、非洲沿岸海区(11°~16°N,16°~18°W)海面高度波动剧烈。对海面高度距平进行经验正交函数(EOF)分析,得到EOF的3个模态分别占有方差比例为51.5%,13.2%和7.9%。第一模态揭示的是热带辐合带(ITCZ)的季节性迁移导致海面高度距平沿着ITCZ平均位置经向倾斜的1 a周期变化,第一模态还显示了太阳辐射的季节差异引起南北两个海盆海面高度的整体升降。第二模态描述了中心分别位于(3°N,40°W)和(7°N,45°W)附近两个涡漩的变化。第三模态表征的是几内亚海湾上升流和赤道北部下降流在6~7月强度达到最大。对EOF时间系数曲线的经验模态分解(EMD),结果表明热带大西洋低频变化包含的成分主要有:0.5,1,2,4和6 a。其中1 a周期是热带大西洋海面高度变化最主要的周期成分,0.5 a周期和2 a周期也是热带大西洋海面高度变化的重要形式;而4 a和6 a周期所占的比例较小。另外EMD方法还分解出1997~1998年太平洋El Nino事件对热带大西洋海面高度的影响。  相似文献   

南大西洋西非岸盆地群构造、沉积演化对比          下载免费PDF全文

洛怡  李江海  杨梦莲 《中国地质》2021,48(1):120-128

非洲西部海岸盆地群经历了裂谷期、同裂谷期和漂移期构造演化阶段,构造演化和沉积充填有一定的相似性,但是由于后期局部构造和差异沉积的影响,现今盆地发育的构造样式和沉积建造有一定区别,导致勘探效果有较大的差异.本文通过对比南大西洋赤道段转换型、中段含泥型、中段含盐型和南段火山型盆地的综合柱状图,加上对尼日尔三角洲盆地和下刚果...  相似文献   

Modelling storage‐driven connectivity between landscapes and riverscapes: towards a simple framework for long‐term ecohydrological assessment          下载免费PDF全文

C. Soulsby  C. Birkel  D. Tetzlaff 《水文研究》2016,30(14):2482-2497

The importance of conceptualizing the dynamics of storage‐driven saturation area connectivity in runoff generation has been central to the development of TOPMODEL and similar low parameterized rainfall–runoff models. In this contribution, we show how we developed a 40‐year hydrometric data base to simulate storage–discharge relationships in the Girnock catchment in the Scottish Highlands using a simple conceptual model. The catchment is a unique fisheries reference site where Atlantic salmon populations have been monitored since 1966. The modelling allowed us to track storage dynamics in hillslopes, the riparian zone and groundwater, and explicitly link non‐linear changes of streamflows to landscape storage and connectivity dynamics. This provides a fundamental basis for understanding how the landscape and riverscape are hydrologically connected and how this regulates in‐stream hydraulic conditions that directly influence salmonids. We use the model to simulate storage and discharge dynamics over the 40‐year period of fisheries records. The modelled storage‐driven connectivity provides an ecohydological context for understanding the dynamics in stream flow generation which determine habitat hydraulics for different life stages of salmon population. This new, long‐term modelling now sets this variability in the riverscape in a more fundamental context of the inter‐relationships between storage in the landscape and stream flow generation. This provides a simple, robust framework for future ecohydrological modelling at this site, which is an alternative to more increasingly popular but highly parameterized and uncertain commercial ecohydrological models. It also provides a wider, novel context that is a prerequisite for any model‐based scenario assessment of likely impacts resulting from climate or land use change. Copyright © 2016 The Authors Hydrological Processes Published by John Wiley & Sons Ltd. Copyright © 2016 The Authors Hydrological Processes Published by John Wiley & Sons Ltd.  相似文献