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41.
Niels Hovius Albert Galy Robert G. Hilton Robert Sparkes Joanne Smith Kao Shuh-Ji Chen Hongey Lin In-Tian A. Joshua West 《Applied Geochemistry》2011
Rapidly eroding, coastal mountain belts, where steep rivers and submarine channels connect upland sources to nearby marine sinks are hotspots of organic carbon transfer from life biomass, soil and exhumed bedrock into geological storage. Using observations from the Southern Alps of New Zealand, and Taiwan, we have mapped this organic pathway to geological carbon sequestration, and can evaluate the magnitude and efficiency of transfers between sources and sinks. We demonstrate that POC is harvested by landsliding, but importantly also by common and widespread surface runoff on steep hillslopes. Although terrestrially sourced POC is found in many sedimentary environments associated with mountain belts and frontier basins, it appears to be most abundantly trapped and preserved in marine turbidites. The loss of all forms of POC in onward transport through short, steep routing systems to this repository is limited. This is in marked contrast to larger routing systems, in which only the most resilient forms of POC survive into long-term deposition. 相似文献
42.
Scales and structure of frontal adjustment and freshwater export in a region of freshwater influence
Sea surface temperature satellite imagery and a regional hydrodynamic model are used to investigate the variability and structure
of the Liverpool Bay thermohaline front. A statistically based water mass classification technique is used to locate the front
in both data sets. The front moves between 5 and 35 km in response to spring–neap changes in tidal mixing, an adjustment that
is much greater than at other shelf-sea fronts. Superimposed on top of this fortnightly cycle are semi-diurnal movements of
5–10 km driven by flood and ebb tidal currents. Seasonal variability in the freshwater discharge and the density difference
between buoyant inflow and more saline Irish Sea water give rise to two different dynamical regimes. During winter, when cold
inflow reduces the buoyancy of the plume, a bottom-advected front develops. Over the summer, when warm river water provides
additional buoyancy, a surface-advected plume detaches from the bottom and propagates much larger distances across the bay.
Decoupled from near-bed processes, the position of the surface front is more variable. Fortnightly stratification and re-mixing
over large areas of Liverpool Bay is a potentially important mechanism by which freshwater, and its nutrient and pollutant
loads, are exported from the coastal plume system. Based on length scales estimated from model and satellite data, the erosion
of post-neap stratification is estimated to be responsible for exporting approximately 19% of the fresh estuarine discharge
annually entering the system. Although the baroclinic residual circulation makes a more significant contribution to freshwater
fluxes, the episodic nature of the spring–neap cycle may have important implications for biogeochemical cycles within the
bay. 相似文献
43.
Jonathan P. A. Gardner Martin J. Curwen Joanne Long Robert J. Williamson Ann R. Wood 《新西兰海洋与淡水研究杂志》2013,47(1):179-194
The Kermadec Islands Marine Reserve (KIMR), which is located at 30°S, is New Zealand's largest marine reserve at 748 000 ha, and its biota is composed of a mix of warm temperate, subtropical, and tropical species. A depth‐stratified ecological survey was conducted of the abundance and percentage cover of macrobenthic species and of the water column at two sites (Meyer Island and West Chanter Island), 2km apart. Significant differences in benthic community structure and in water column turbidity and chlorophyll concentrations were observed between the two sites despite their proximity and physical similarity. Compared with other “snapshot” surveys of benthic community structure at sites within the KIMR there was a high degree of similarity among the species observed, but often a low degree of similarity in species abundance or percentage cover as a function of depth. We suggest that despite its isolation and the degree of difficulty of working at this location, a full‐scale ecological survey of the coastal marine biota of the KIMR is warranted to better understand New Zealand's subtropical marine biota and its affinities with other marine biotas of the South Pacific. 相似文献
44.
Joanne M. Deely J. Clair Tunnicliff C. Jane Orange Wayne H. L. Edgerley 《新西兰海洋与淡水研究杂志》2013,47(3-4):417-427
Abstract Surface sediment samples (60 μm‐2 mm, and < 60 μm fractions) from the Waiwhetu Stream, Lower Hutt City, New Zealand, were leached with dilute HCl to remove the mobile heavy‐metal fraction. Cd, Cr, Cu, Pb, Zn, Al, Fe, and Mn analyses of the leachates show that sediments of the upper reaches area of the stream are generally uncontaminated. In contrast, sediments in the lower reaches area are highly contaminated, despite clean‐up measures in the late 1970s. Lead and Zn are the most significantly enriched metals with concentrations over 1000 mg kg?1 adjacent to some drains. In the polluted zone, metals originate from either upward remobilisation from underlying sediment (contaminated in the early 1960s and 70s) or more recent industrial spillages. Similar trends exhibited by Cd, Cu, Cr, Zn, Pb, and Al indicate that a proportion of the metal enrichment downstream probably results from a naturally higher clay content of sediments near the mouth of the stream. Fe and Mn show reverse trends to the other metals, indicating that a high proportion of these two metals occurs in substrate different to that of the other metals. The orange brick‐coloured sediments of the upper reaches of the stream indicate oxides upstream; the black sediments in the lower reaches indicate sulphides downstream. 相似文献
45.
The pedogenic histories of four adjacent profiles of a polygenetic palaeosol developed on a Middle Pleistocene terrace of the proto-Thames from Wivenhoe in southeast England are reconstructed on the basis of superposition of key micromorphological features. Despite a considerable variation in macromorphology, partly resulting from large-scale periglacial features, three of the profiles have similar micromorphological records in that they retain evidence for two phases of clay illuviation separated by a period of periglacial disruption. This reconstruction, however, seems to be incomplete because the fourth profile contains micromorphological evidence for a further illuviation–disruption cycle. The extent of this variation suggests that soil micromorphology should be used only with care to reconstruct pedogenic or pedosedimentary histories of complex polygenetic palaeosols, or to compare such palaeosols on different surfaces of chronosequences spanning periods of major climatic change. The variable and possibly limited resolution of micromorphology, together with the current uncertainty over the exact environmental signifiance of illuvial clay features, means that inferred pedogenic phases should be correlated with specific climatic stages only with considerable caution. © 1998 John Wiley & Sons, Ltd. 相似文献
46.
Ancient Peruvian irrigation systems have been studied extensively, but much remains unknown about technical and hydrological aspects of these irrigation systems. The Pampa de Chaparrí irrigation system in Peru is used as an example to show how modeling approaches for hydrological and hydraulic features of irrigation can yield results to improve our understanding of irrigation in the area. Analysis focuses on water availability compared demand, the way available water may have been applied to crops and whether the water needed could be delivered through the canal system. Results suggest that on the Pampa some 2500 hectares may have been cultivated within certain security limits for acceptable yields. The rhythm with which the irrigation requirement was applied to crops most likely influenced yields and thus food security. Furthermore, the influence of groundwater on crop growth may have been considerable. The hydraulic behavior of the irrigation system suggests that it should not be taken for granted that theoretically required water flows could actually be diverted and/or distributed to water users. The many questions coming out of the results define important items for a joint research agenda of archeologists and irrigation scientists. 相似文献
47.
48.
Joanne P. Sharp 《Area》2000,32(3):327-334
Summary The recent 'culture turn' in geography has generated a good deal of interest in the structure of scientific knowledge and modes of writing, but there has less attention to the construction of other forms of knowledge and writing. While humanistic and regional geographers have referred to literature on the whole without comment on genre, mode of production or range of consumption, more recent critical geographers have regarded literature as a material artefact which fulfils a role designated by its position in various social and economic processes. This paper critiques both positions as offering a limited vision of the relationship between geography and literature and attempts to offer an engagement with literary fiction which analyses the content and form of the text, but also leaves room for its distinctive voice. 相似文献
49.
Noriyuki Narukage Masahito Kubo Ryohko Ishikawa Shin-nosuke Ishikawa Yukio Katsukawa Toshihiko Kobiki Gabriel Giono Ryouhei Kano Takamasa Bando Saku Tsuneta Frédéric Auchère Ken Kobayashi Amy Winebarger Jim McCandless Jianrong Chen Joanne Choi 《Solar physics》2017,292(3):40
Precise polarization measurements in the vacuum ultraviolet (VUV) region are expected to be a new tool for inferring the magnetic fields in the upper atmosphere of the Sun. High-reflectivity coatings are key elements to achieving high-throughput optics for precise polarization measurements. We fabricated three types of high-reflectivity coatings for a solar spectropolarimeter in the hydrogen Lyman-\(\upalpha \) (Ly\(\upalpha \); 121.567 nm) region and evaluated their performance. The first high-reflectivity mirror coating offers a reflectivity of more than 80 % in Ly\(\upalpha \) optics. The second is a reflective narrow-band filter coating that has a peak reflectivity of 57 % in Ly\(\upalpha \), whereas its reflectivity in the visible light range is lower than 1/10 of the peak reflectivity (\(\sim 5~\%\) on average). This coating can be used to easily realize a visible light rejection system, which is indispensable for a solar telescope, while maintaining high throughput in the Ly\(\upalpha \) line. The third is a high-efficiency reflective polarizing coating that almost exclusively reflects an s-polarized beam at its Brewster angle of 68° with a reflectivity of 55 %. This coating achieves both high polarizing power and high throughput. These coatings contributed to the high-throughput solar VUV spectropolarimeter called the Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP), which was launched on 3 September, 2015. 相似文献
50.
This paper considers the overall outcome of a “public environmental audit” of the government management of the oil and gas offshore industry in eastern Canada. Five requests for data sets were placed using the Access to Information Act; all five requests were denied by the Canada-Newfoundland Labrador Offshore Petroleum Board. This lack of access to environmental monitoring data significantly hinders the ability of independent scientific inquiry and/or public involvement in the environmental assessment process. 相似文献