Reconstructed streamflow for Citarum River, Java, Indonesia: linkages to tropical climate dynamics     

Rosanne D��Arrigo  Nerilie Abram  Caroline Ummenhofer  Jonathan Palmer  Manfred Mudelsee 《Climate Dynamics》2011,36(3-4):451-462

The Citarum river basin of western Java, Indonesia, which supplies water to 10 million residents in Jakarta, has become increasingly vulnerable to anthropogenic change. Citarum??s streamflow record, only ~45?years in length (1963-present), is too short for understanding the full range of hydrometeorological variability in this important region. Here we present a tree-ring based reconstruction of September?CNovember Citarum streamflow (AD 1759?C2006), one of the first such records available for monsoon Asia. Close coupling is observed between decreased tree growth and low streamflow levels, which in turn are associated with drought caused by ENSO warm events in the tropical Pacific and Indian Ocean positive dipole-type variability. Over the full length of record, reconstructed variance was at its weakest during the interval from ~1905?C1960, overlapping with a period of unusually-low variability (1920?C1960) in the ENSO-Indian Ocean dipole systems. In subsequent decades, increased variance in both the streamflow anomalies and a coral-based SST reconstruction of the Indian Ocean Dipole Mode signal the potential for intensified drought activity and related consequences for water supply and crop productivity in western Java, where much of the country??s rice is grown.  相似文献   

Susceptibility of fish to Chattonella marina is determined by its tolerance to hypoxia     

Shen M  Xu J  Chan AK  Au DW 《Marine pollution bulletin》2011,63(5-12):189-194

The harmful alga Chattonella marina has caused massive fish kills and economic losses worldwide. However, the fish kill mechanisms by C. marina have not been identified. The present study has confirmed that a significant elevation of blood osmolality is the universal response in moribund fish exposed to C. marina and the possible reasons leading to contradictory reports were identified. Both osmotic distress and respiratory impairment are important mechanisms leading to fish kill by C. marina. The susceptibility of marine fish to C. marina appears to be inversely related to their tolerance to hypoxia, with the hypoxia intolerant goldlined seabream being the most susceptible, and the hypoxia tolerant green grouper being the most tolerant to C. marina. Further studies in the marine medaka (Oryzias melastigma) showed that fish susceptibility to C. marina is directly related to susceptibility of the fish to hypoxia, but not related to its tolerance to hypersalinity stress.  相似文献   

Interannual climate variability in South America: impacts on seasonal precipitation, extreme events, and possible effects of climate change   总被引：8，自引：7，他引：1  

Alice M. Grimm 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(4):537-554

Interannual variability is an important modulator of synoptic and intraseasonal variability in South America. This paper seeks to characterize the main modes of interannual variability of seasonal precipitation and some associated mechanisms. The impact of this variability on the frequency of extreme rainfall events and the possible effect of anthropogenic climate change on this variability are reviewed. The interannual oscillations of the annual total precipitation are mainly due to the variability in austral autumn and summer. While autumn is the dominant rainy season in the northern part of the continent, where the variability is highest (especially in the northeastern part), summer is the rainy season over most of the continent, thanks to a summer monsoon regime. In the monsoon season, the strongest variability occurs near the South Atlantic Convergence Zone (SACZ), which is one of the most important features of the South American monsoon system. In all seasons but summer, the most important source of variability is ENSO (El Ni?o Southern Oscillation), although ENSO shows a great contribution also in summer. The ENSO impact on the frequency of extreme precipitation events is also important in all seasons, being generally even more significant than the influence on seasonal rainfall totals. Climate change associated with increasing emission of greenhouse gases shows potential to impact seasonal amounts of precipitation in South America, but there is still great uncertainty associated with the projected changes, since there is not much agreement among the models’ outputs for most regions in the continent, with the exception of southeastern South America and southern Andes. Climate change can also impact the natural variability modes of seasonal precipitation associated with ENSO.  相似文献   

Some challenges of monitoring a potentially active volcanic field in a large urban area: Auckland volcanic field,New Zealand     

Ashenden  Caroline L.  Lindsay  Jan M.  Sherburn  Steven  Smith  Ian E. M.  Miller  Craig A.  Malin  Peter E. 《Natural Hazards》2011,59(1):507-528

Natural Hazards - The city of Auckland (population 1.3 million) is built on and around a potentially active basaltic intraplate volcanic system, the Auckland volcanic field. This...  相似文献   

Rapid Holocene coastal change revealed by high-resolution micropaleontological analysis, Pamlico Sound, North Carolina, USA     

Candace Grand Pre  Stephen J. Culver  David J. Mallinson  Kathleen M. Farrell  D. Reide Corbett  Benjamin P. Horton  Caroline Hillier  Stanley R. Riggs  Scott W. Snyder  Martin A. Buzas 《Quaternary Research》2011,76(3):319-334

Foraminiferal analyses of 404 contiguous samples, supported by diatom, lithologic, geochronologic and seismic data, reveal both rapid and gradual Holocene paleoenvironmental changes in an 8.21-m vibracore taken from southern Pamlico Sound, North Carolina. Data record initial flooding of a latest Pleistocene river drainage and the formation of an estuary 9000 yr ago. Estuarine conditions were punctuated by two intervals of marine influence from approximately 4100 to 3700 and 1150 to 500 cal yr BP. Foraminiferal assemblages in the muddy sand facies that accumulated during these intervals contain many well-preserved benthic foraminiferal species, which occur today in open marine settings as deep as the mid shelf, and significant numbers of well-preserved planktonic foraminifera, some typical of Gulf Stream waters. We postulate that these marine-influenced units resulted from temporary destruction of the southern Outer Banks barrier islands by hurricanes. The second increase in marine influence is coeval with increased rate of sea-level rise and a peak in Atlantic tropical cyclone activity during the Medieval Climate Anomaly. This high-resolution analysis demonstrates the range of environmental variability and the rapidity of coastal change that can result from the interplay of changing climate, sea level and geomorphology in an estuarine setting.  相似文献   

Worldwide Typology of Nearshore Coastal Systems: Defining the Estuarine Filter of River Inputs to the Oceans   总被引：1，自引：0，他引：1  

Hans H. Dürr  Goulven G. Laruelle  Cheryl M. van Kempen  Caroline P. Slomp  Michel Meybeck  Hans Middelkoop 《Estuaries and Coasts》2011,34(3):441-458

We present a spatially explicit global overview of nearshore coastal types, based on hydrological, lithological and morphological criteria. A total of four main operational types act as active filters of both dissolved and suspended material entering the ocean from land: small deltas (type I), tidal systems (II), lagoons (III) and fjords (IV). Large rivers (V) largely bypass the nearshore filter, while karstic (VI) and arheic coasts (VII) act as inactive filters. This typology provides new insight into the spatial distribution and inherent heterogeneity of estuarine filters worldwide. The relative importance of each type at the global scale is calculated and types I, II, III and IV account for 32%, 22%, 8% and 26% of the global coastline, respectively, while 12% have a very limited nearshore coastal filter. As an application of this typology, the global estuarine surface area is re-estimated to 1.1 × 10⁶ km² instead of 1.4 × 10⁶ km² in earlier work.  相似文献   

Impacts of diverted freshwater on dissolved organic matter and microbial communities in Barataria Bay, Louisiana, U.S.A     

Bianchi TS  Cook RL  Perdue EM  Kolic PE  Green N  Zhang Y  Smith RW  Kolker AS  Ameen A  King G  Ojwang LM  Schneider CL  Normand AE  Hetland R 《Marine environmental research》2011,72(5):248-257

Here we present results of an initial assessment of the impacts of a water diversion event on the concentrations and chemical composition of dissolved organic matter (DOM) and bacterioplankton community composition in Barataria Bay, Louisiana U.S.A, an important estuary within the Mississippi River Delta complex. Concentrations and spectral properties of DOM, as reflected by UV/visible absorbance and fluorescence, were strikingly similar at 26 sites sampled along transects near two western and two eastern areas of Barataria Bay in July and September 2010. In September 2010, dissolved organic carbon (DOC) was significantly higher (568.1-1043 μM C, x=755.6+/-117.7 μM C, n=14) than in July 2010 (249.1-577.1 μM C, x=383.7+/-98.31 μM C, n=14); conversely, Abs254 was consistently higher at every site in July (0.105-0.314) than in September (0.080-0.221), averaging 0.24±0.06 in July and 0.15±0.04 in September. Fluorescence data via the fluorescence index (FI450/500) revealed that only 30% (8 of 26) of the July samples had an FI450/500 above 1.36, compared to 96% (25 of 26) for the September samples. This indicates a more terrestrial origin for the July DOM. Bacterioplankton from eastern sites differed in composition from bacterioplankon in western sites in July. These differences appeared to result from reduced salinities caused by the freshwater diversion. Bacterioplankton communities in September differed from those in July, but no spatial structure was observed. Thus, the trends in bacterioplankton and DOM were likely due to changes in water masses (e.g., input of Mississippi River water in July and a return to estuarine waters in September). Discharge of water from the Davis Pond Freshwater Diversion (DPFD) through Barataria Bay may have partially mitigated some adverse effects of the oil spill, inasmuch as DOM is concerned.  相似文献   

Coupled penetrometer, MBES and ADCP assessments of tidal variations in surface sediment layer characteristics along active subaqueous dunes, Danish Wadden Sea     

Nina Stark  Hendrik Hanff  Christian Svenson  Verner B. Ernstsen  Alice Lefebvre  Christian Winter  Achim Kopf 《Geo-Marine Letters》2011,31(4):249-258

In-situ geotechnical measurements of surface sediments were carried out along large subaqueous dunes in the Knudedyb tidal inlet channel in the Danish Wadden Sea using a small free-falling penetrometer. Vertical profiles showed a typical stratification pattern with a resolution of ∼1 cm depicting a thin surface layer of low sediment strength and a stiffer substratum below (quasi-static bearing capacity equivalent: 1–3 kPa in the top layer, 20–140 kPa in the underlying sediment; thickness of the top layer ca. 5–8 cm). Observed variations in the thickness and strength of the surface layer during a tidal cycle were compared to mean current velocities (measured using an acoustic Doppler current profiler, ADCP), high-resolution bathymetry (based on multibeam echo sounding, MBES) and qualitative estimates of suspended sediment distributions in the water column (estimated from ADCP backscatter intensity). The results revealed an ebb dominance in sediment remobilization, and a general accretion of the bed towards low water. A loose top layer occurred throughout the tidal cycle, likely influenced by bedload transport and small events of suspended sediment resettlement (thickness: 6 ± 2 cm). Furthermore, this layer showed a significant increase in thickness (e.g. from 8 cm to 16 cm) related to periods of overall deposition. These findings imply that dynamic penetrometers can conveniently serve to (1) quantify potentially mobile sediments by determining the thickness of a loose sediment surface layer, (2) unravel sediment strength development in potentially mobile sediments and (3) identify sediment accumulation. Such data are an important complement and add a new geotechnical perspective during investigations of sediment remobilization processes in highly dynamic coastal environments.  相似文献   

A Comparison of Awareness,Attitudes, and Usage of Water Quality Conservation Practices Between Amish and Non-Amish Farmers     

Jessica D. Ulrich-Schad  Caroline Brock  Linda S. Prokopy 《社会与自然资源》2017,30(12):1476-1490

This study provides a unique examination of Amish farmers’ awareness of water quality issues and their attitudes toward and use of agricultural conservation practices compared with small non-Amish farmers in Northeastern Indiana. There is minimal research about the conservation beliefs and behaviors of this growing and highly diverse ethnoreligious minority, who have faith-based technological restrictions and are often hesitant to work with community outsiders, especially the government. We find that, compared with non-Amish farmers, Amish farmers have limited awareness of the linkages between common agricultural practices and broader water quality problems and lower levels of adoption of conservation practices, with the exception of cover crops. This information is essential for conservation practitioners who need to work with a diverse range of agricultural producers to increase the uptake of conservation practices that address critical water quality concerns.  相似文献   

Generation of CO2-rich melts during basalt magma ascent and degassing   总被引：1，自引：0，他引：1  

Michel Pichavant  Ida Di Carlo  Silvio G. Rotolo  Bruno Scaillet  Alain Burgisser  Nolwenn Le Gall  Caroline Martel 《Contributions to Mineralogy and Petrology》2013,166(2):545-561

To test mechanisms of basaltic magma degassing, continuous decompressions of volatile-bearing (2.7–3.8 wt% H₂O, 600–1,300 ppm CO₂) Stromboli melts were performed from 250–200 to 50–25 MPa at 1,180–1,140 °C. Ascent rates were varied from 0.25 to ~1.5 m/s. Glasses after decompression show a wide range of textures, from totally bubble-free to bubble-rich, the latter with bubble number densities from 10⁴ to 10⁶ cm^?3, similar to Stromboli pumices. Vesicularities range from 0 to ~20 vol%. Final melt H₂O concentrations are homogeneous and always close to solubilities. In contrast, the rate of vesiculation controls the final melt CO₂ concentration. High vesicularity charges have glass CO₂ concentrations that follow theoretical equilibrium degassing paths, whereas glasses from low vesicularity charges show marked deviations from equilibrium, with CO₂ concentrations up to one order of magnitude higher than solubilities. FTIR profiles and maps reveal glass CO₂ concentration gradients near the gas–melt interface. Our results stress the importance of bubble nucleation and growth, and of volatile diffusivities, for basaltic melt degassing. Two characteristic distances, the gas interface distance (distance either between bubbles or to gas–melt interfaces) and the volatile diffusion distance, control the degassing process. Melts containing numerous and large bubbles have gas interface distances shorter than volatile diffusion distances, and degassing proceeds by equilibrium partitioning of CO₂ and H₂O between melt and gas bubbles. For melts where either bubble nucleation is inhibited or bubble growth is limited, gas interface distances are longer than volatile diffusion distances. Degassing proceeds by diffusive volatile transfer at the gas–melt interface and is kinetically limited by the diffusivities of volatiles in the melt. Our experiments show that CO₂-oversaturated melts can be generated as a result of magma decompression. They provide a new explanation for the occurrence of CO₂-rich natural basaltic glasses and open new perspectives for understanding explosive basaltic volcanism.  相似文献