Export fluxes of biogenic matter in the presence and absence of seasonal sea ice cover in the Chukchi Sea     

Catherine Lalande  Jacqueline M. Grebmeier  Paul Wassmann  Lee W. Cooper  Mikhail V. Flint  Valentina M. Sergeeva 《Continental Shelf Research》2007

Drifting sediment traps were deployed at 9 stations in May-June (ice-covered conditions) and July-August (ice-free conditions) 2004 in the Chukchi Sea to investigate the variability in export fluxes of biogenic matter in the presence and absence of sea ice cover. Measurements of chlorophyll-a (Chl-a), particulate organic carbon (POC), particulate nitrogen (PN), phytoplankton, zooplankton fecal pellets, and the stable carbon isotope composition (δ¹³C) of the sinking material were performed along Barrow Canyon (BC) and a parallel shelf-to-basin transect from East Hanna Shoal (EHS) to the Canada Basin. POC export fluxes were similarly high in the presence (378±106 mg C m⁻² d⁻¹) and in the absence of ice cover (442±203 mg C m⁻² d⁻¹) at the BC stations, while fluxes were significantly higher in the absence (129±98 mg C m⁻² d⁻¹) than in the presence of ice cover (44±29 mg C m⁻² d⁻¹) at the EHS stations. The C/N ratios and δ¹³C values of sinking organic particles indicated that POC export fluxes on the Chukchi continental shelf were mostly composed of freshly produced labile material, except at the EHS stations under ice cover where the exported matter was mostly composed of refractory material probably advected into the EHS region. Chl-a fluxes were higher under ice cover than in ice-free water, however, relatively low daily loss rates of Chl-a and similar phytoplankton carbon fluxes in ice-covered and ice-free water suggest the retention of phytoplankton in the upper water column. An increase in fecal pellet carbon fluxes in ice-free water reflected higher grazing pressure in the absence of ice cover. Elevated daily loss rates of POC at the BC stations confirmed other indications that Barrow Canyon is an important area of carbon export to the basin and/or benthos. These results support the conclusion that there are large spatial and temporal variations in export fluxes of biogenic matter on the Chukchi continental shelf, although export fluxes may be similar in the presence and in the absence of ice cover in highly productive regions.  相似文献   

Effects of climate change and urban development on the distribution and conservation of vegetation in a Mediterranean type ecosystem     

Bray J. Beltrán  Janet Franklin  Alexandra D. Syphard  Helen M. Regan  Lorraine E. Flint  Alan L. Flint 《International journal of geographical information science》2014,28(8):1561-1589

Climate and land-use changes are projected to threaten biodiversity over this century. However, few studies have considered the spatial and temporal overlap of these threats to evaluate how ongoing land-use change could affect species ranges projected to shift outside conservation areas. We evaluated climate change and urban development effects on vegetation distribution in the Southwest ecoregion, California Floristic Province, USA. We also evaluated how well a conservation network protects suitable habitat for rare plant species under these change projections and identified primary sources of uncertainty. We used consensus-based maps from three species distribution models (SDMs) to project current and future suitable habitat for 19 species representing different functional types (defined by fire-response – obligate seeders, resprouting shrubs – and life forms – herbs, subshrubs), and range sizes (large/common, small/rare). We used one spatially explicit urban growth projection; two climate models, emission scenarios, and probability thresholds applied to SDMs; and high-resolution (90 m) environmental data. We projected that suitable habitat could disappear for 4 species and decrease for 15 by 2080. Averaged centroids of suitable habitat (all species) were projected to shift tens (up to hundreds) of kilometers. Herbs showed a small-projected response to climate change, while obligate seeders could suffer the greatest losses. Several rare species could lose suitable habitat inside conservation areas while increasing area outside. We concluded that (i) climate change is more important than urban development for vegetation habitat loss in this ecoregion through 2080 due to diminishing amounts of undeveloped private land in this region; (ii) the existing conservation plan, while extensive, may be inadequate to protect plant diversity under projected patterns of climate change and urban development, (iii) regional assessments of the dynamics of the drivers of biodiversity change based on high-resolution environmental data and consensus predictive mapping, such as this study, are necessary to identify the species expected to be the most vulnerable and to meaningfully inform regional-scale conservation.  相似文献   

An acoustic emission landslide early warning system for communities in low-income and middle-income countries     

N. Dixon  A. Smith  J. A. Flint  R. Khanna  B. Clark  M. Andjelkovic 《Landslides》2018,15(8):1631-1644

Early warning systems for slope instability are needed to alert users of accelerating slope deformation behaviour, enable evacuation of vulnerable people, and conduct timely repair and maintenance of critical infrastructure. Communities exposed to landslide risk in low- and middle-income countries seldom currently instrument and monitor slopes to provide a warning of instability because existing techniques are complex and prohibitively expensive. Research and field trials have demonstrated conclusively that acoustic emission (AE) monitoring can be an effective approach to detect accelerating slope movements and to subsequently communicate warnings to users. The objective of this study was to develop and assess a simple, robust, low-cost AE monitoring system to warn of incipient landslides, which can be widely deployed and operated by communities globally to help protect vulnerable people. This paper describes a novel AE measurement sensor that has been designed and developed with the cost constrained to a few hundred dollars (US). Results are presented from physical model experiments that demonstrate performance of the AE system in measuring accelerating deformation behaviour, with quantifiable relationships between AE and displacement rates. Exceedance of a pre-determined trigger level of AE can be used to communicate an alarm to users in order to alert them of a slope failure. Use of this EWS approach by communities worldwide would reduce the number of fatalities caused by landslides.  相似文献   

Features of the Behavior of Organic Compounds in Water and Bottom Sediments in the Kara Sea during Seasonal Ice Melting     

Nemirovskaya  I. A.  Flint  M. V. 《Oceanology》2022,62(1):50-58

Oceanology - The article presents the first data on the content of organic compounds (OCs): Corg, lipids, and hydrocarbons (aliphatic—AHCs) and polycyclic aromatic (PAHs)) in suspended...  相似文献   

Seasonal Variability in the Sedimentary Matter Flux on the Shelf of the Northern Kara Sea     

Drits  A. V.  Kravchishina  M. D.  Sukhanova  I. N.  Belyaev  N. A.  Karmanov  V. A.  Flint  M. V. 《Oceanology》2021,61(6):984-993

Oceanology - Sedimentation rates in the northern Kara Sea between September 2019 and July 2020 were calculated from integrated monthly values for sedimentary matter, organic carbon, nitrogen, total...  相似文献   

Standing different ground: the spatial heterogeneity of territorial disputes     

Sang-Hyun Chi  Colin Flint 《GeoJournal》2013,78(3):553-573

Recent developments in spatial analysis and spatial data have allowed researchers to investigate various geographical factors in the quantitative analysis of conflict and war (Ward in Polit Geogr 21(2):155–158, 2002). Despite the importance of territory in interstate conflict, there has been a limited interest in the application of spatial analysis to the study of territorial conflict. Using geographically weighted regression (GWR) we evaluated the existing explanations of territorial conflict provided by a global scale analysis that assumes a spatial consistency in the explanatory variables. Specifically, we revisited Paul Huth’s foundational work by using GWR to examine the spatial pattern in the sign and significance of the variables. The result of GWR shows that the escalation of territorial conflict cannot be fully explained by one universal model. There is a high level of spatial variation in the regression parameters and the explanatory power of the model varies over space. A k-means cluster analysis was implemented for a further investigation of the regional pattern of the underlying causes of territorial disputes. The result of our GWR suggests the necessity and possibility to pursue a local or regional scale approach to the study of territorial conflict, an approach that challenges an epistemology of seeking a single explanation for the causes of conflict that neglects regional context. The spatial heterogeneity in the causes of territorial conflict escalation we find is framed within a narrative of the intertwined processes of colonialism, Cold War legacies, and competition for resources.  相似文献   

Phytoplankton of the surface desalted lens of the Kara Sea     

I. N. Sukhanova  M. V. Flint  V. M. Sergeeva 《Oceanology》2012,52(5):635-645

The phytoplankton of a surface strongly desalinated water lens was investigated on the basis of materials collected during the 57th cruise of the R/V Akademik Mstislav Keldish in September of 2007. The lens with a salinity of <18 psu had area of approximately 19 thousand square kilometers and was located in the northwestern part of the Kara Sea near the eastern coast of Novaya Zemlya. It was a specific biotope that had been isolated from the surrounding waters for more than three months. In the investigated area, 66 algae species were identified. The maximal species diversity was found in the upper layers of the desalinated lens, where the species number was 1.5 to 3 times higher than in other parts of the water column. The phytoplankton numbers in the upper layers of the lens were 1.5 to 4.5 times higher than in its lower part and generally higher than below the picnocline. Diatoms were the most abundant group in the upper layers of the lens, while flagellates dominated in numbers in the subpicnocline part of the water column. The maximal values of the phytoplankton biomass were observed everywhere in the upper layers of the lens, where they were 1.2 to 3.7 times higher than in the lower part of the lens and 1.3 to 7.2 times higher than in the layer below the picnocline. Dinoflagellates generally gave the most contribution to the total phytoplankton biomass. The phytoplankton of the desalinated surface lens in the northwestern part of the Kara Sea by its composition and quantitative parameters had the nearest resemblance to a phytocenosis that we observed two weeks later at a shallow desalinated shelf closely adjacent to the Ob estuary.  相似文献   

Numerical Estimations of Desalinated Seawater Modification Using Waters of the Laptev Sea Shelf as an Example     

Dubinina  E. O.  Miroshnikov  A. Yu.  Kossova  S. A.  Flint  M. V. 《Doklady Earth Sciences》2019,484(1):109-113

Doklady Earth Sciences - Continental runoff, inflowing to Arctic waters, is estimated by the use of isotope and hydrophysical tracers. This is quite a complicated task, because desalinated waters...  相似文献   

A sequence stratigraphic model for the Lower Coal Measures (Upper Carboniferous) of the Ruhr district, north-west Germany   总被引：3，自引：0，他引：3  

Gary Hampson  Harald Stollhofen  & Steve Flint 《Sedimentology》1999,46(6):1199-1231

Upper Carboniferous Coal Measures strata have been interpreted traditionally in terms of cyclothems bounded by marine flooding surfaces (marine bands) and coal seams. Correlation of such cyclothems in an extensive grid of closely spaced coal exploration boreholes provides a robust stratigraphic framework in which to study the Lower Coal Measures (Namurian C–Westphalian A) of the Ruhr district, north-west Germany. Three distinct types of cyclothem are recognized, based on their bounding surfaces and internal facies architecture. (1) Type 1 cyclothems are bounded by marine bands. Each cyclothem comprises a thick (30–80 m), regionally extensive, coarsening-upward delta front succession of interbedded shales, siltstones and sandstones, which may be deeply incised by a major fluvial sandstone complex. The delta front succession is capped by a thin (<1 m), regionally extensive coal seam and an overlying marine band defining the top of the cyclothem. (2) Type 2 cyclothems are bounded by thick (≈1 m), regionally extensive coal seams with few splits. The basal part of a typical cyclothem comprises a thick (15–50 m), widespread, coarsening-upward delta front or lake infill succession consisting of interbedded shales, siltstones and sandstones. Networks of major (>5 km wide, 20–40 m thick), steep-sided, multistorey fluvial sandstone complexes erode deeply into and, in some cases, through these successions and are overlain by the coal seam defining the cyclothem top. (3) Type 3 cyclothems are bounded by regionally extensive coal seam groups, characterized by numerous seam splits on a local (0·1–10 km) scale. Intervening strata vary in thickness (15–60 m) and are characterized by strong local facies variability. Root-penetrated, aggradational floodplain heteroliths pass laterally into single-storey fluvial channel-fill sandstones and coarsening-upward, shallow lake infill successions of interbedded shales, siltstones and sandstones over distances of several hundred metres to a few kilometres. Narrow (<2 km) but thick (20–50 m) multistorey fluvial sandstone complexes are rare, but occur in a few type 3 cyclothems. Several cyclothems are observed to change character from type 1 to type 2 and from type 2 to type 3 up the regional palaeoslope. Consequently, we envisage a model in which each cyclothem type represents a different palaeogeographic belt within the same, idealized delta system, subject to the same allogenic and autogenic controls on facies architecture. Type 1 cyclothems are dominated by deltaic shorelines deposited during a falling stage and lowstand of sea level. Type 2 cyclothems represent the coeval lower delta plain, which was deeply eroded by incised valleys that fed the falling stage and lowstand deltas. Type 3 cyclothems comprise mainly upper delta plain deposits in which the allogenic sea-level control was secondary to autogenic controls on facies architecture. The marine bands, widespread coals and coal seam groups that bound these three cyclothem types record abandonment of the delta system during periods of rapid sea-level rise. The model suggests that the extant cyclothem paradigm does not adequately describe the detailed facies architecture of Lower Coal Measures strata. Instead, these architectures may be better understood within a high-resolution stratigraphic framework incorporating sequence stratigraphic key surfaces, integrated with depositional models derived from analogous Pleistocene–Holocene fluvio-deltaic strata.  相似文献   

Multidisciplinary studies of the ecosystem of the Kara Sea: Cruise 54 of R/V <Emphasis Type="Italic">Akademik Mstislav Keldysh</Emphasis>     

M. V. Flint  A. G. Zatsepin  N. V. Kucheruk  S. G. Poyarkov  N. A. Rimskii-Korsakov 《Oceanology》2008,48(6):883-887

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