the flux of black carbon to surface sediments on the new england continental shelf abstract concentrations and 210 pb derived fluxes of black carbon bc were deduced in recent ocean margin sediments off northeastern usa to investigate the role of this carbon form in the biogeochemical cycle of this element bc concentrations in contemporary open shelf sediments ranged between 0 11 and 1 7 mg gdw temporal trends of bc in cores as well as the pattern of chemical markers of combustion sources were consistent with anthropogenic fossil fuel combustion dominating the bc input to these sediments in recent times bc fluxes of 1 2 g m 2 yr 1 suggest that the northeastern usa shelf sink is of the same magnitude as estimates of the bc production from fossil fuel and biomass burning in the upwind ne usa source region identification of about 10 of total organic carbon as bc has implications for sedimentary carbon preservation as well as several other aspects of the global biogeochemical cycle of carbon

release of black carbon from thawing permafrost estimated by sequestration fluxes in the east siberian arctic shelf recipient black carbon bc plays an important role in carbon burial in marine sediments globally yet the sequestration of bc in the arctic ocean is poorly understood here we assess the concentrations fluxes and sources of soot bc sbc the most refractory component of bc in sediments from the east siberian arctic shelf esas the world s largest shelf sea system sbc concentrations in the contemporary shelf sediments range from 0 1 to 2 1 mg g 1 dw corresponding to 2 12 of total organic carbon the 210pb derived fluxes of sbc 0 42 11 g m 2 yr 1 are higher or in the same range as fluxes reported for marine surface sediments closer to anthropogenic emissions the total burial flux of sbc in the esas 4 000 gg yr 1 illustrates the great importance of this arctic shelf in marine sequestration of sbc the radiocarbon signal of the sbc shows more depleted yet also more uniform signatures 721 to 896 average of 774 62 than of the non sbc pool 304 to 728 average of 491 163 suggesting that sbc is coming from an on average 5 900 300 years older and more specific source than the non sbc pool we estimate that the atmospheric bc input to the esas is negligible 0 6 of the sbc burial flux statistical source apportionment modeling suggests that the esas sedimentary sbc is remobilized by thawing of two permafrost carbon pf c systems surface soil permafrost topsoil pf 25 8 and pleistocene ice complex deposits icd pf 75 8 the sbc contribution to the total mobilized permafrost carbon pf c increases with increasing distance from the coast from 5 to 14 indicating that the sbc is more recalcitrant than other forms of translocated pf c these results elucidate for the first time the key role of permafrost thaw in the transport of sbc to the arctic ocean with ongoing global warming these findings have implications for the biogeochemical carbon cycle increasing the size of this refractory carbon pool in the arctic ocean

peatlands of the western siberian lowlands current knowledge on zonation carbon content and late quaternary history the western siberian lowlands wsl are the world s largest high latitude wetland and possess over 900 000 km 2 of peatlands the peatlands of the wsl are of major importance to high latitude hydrology carbon storage and environmental history analysis of the existing russian data suggests that the mean depth of peat accumulation in the wsl is 256 cm and the total amount of carbon stored there may exceed 53 836 million metric tons a synthesis of published and unpublished radiocarbon dates indicates that the peatlands first developed at the end of the last glacial with a rapid phase of initiation between 11 000 and 10 000 cal yr bp initiation slowed after 8000 cal yr bp and reached a nadir at 4000 cal yr bp there has been renewed initiation particularly south of 621n following 4000 cal yr bp the initial development of peatlands in the wsl corresponds with the warming at the close of the pleistocene cooling after 4000 cal yr bp has likely led to increased permafrost and increased peatland development particularly in central and southern regions cold and dry conditions in the far north may have inhibited peatland formation in the late holocene r 2002 elsevier science ltd all rights reserved

distribution and preservation of black carbon in the east china sea sediments perspectives on carbon cycling at continental margins abstract we determined the concentrations and radiocarbon 14 c compositions of black carbon bc in the sediments of the east china sea ecs the bc concentrations which were in the range of 0 30 1 52 mg g accounted for 12 65 of the total organic carbon toc the distribution of bc in ecs sediments was controlled by factors such as grain size distance from the coast and deposition rate radiocarbon measurements of bc yielded ages of 6350 10 440 years before present bp suggesting that the percentage of bc derived from biomass combustion was in the range of 29 48 the bc burial flux in sediments of the ecs was estimated to be 1 39 10 6 t yr which was similar to burial fluxes reported for shelf sediments in other areas however the magnitude of the total bc sink was far greater than that of any other shelf regions studied to date indicating the global importance of bc accumulation in the ecs and the magnitude of bc input from large rivers e g the changjiang the riverine delivery of bc to the ecs 73 was far greater than that of atmospheric flux 27 further study of the bc cycle and the interactions of bc with other organic compounds in marginal seas was required to better understand the role of bc in the global carbon cycle

contribution of black carbon in recent sediments of the gulf of cadiz applicability of different quantification methodologies abstract in the southwestern iberian peninsula vegetation fires are rather common and produce a considerable amount of charred material that due to erosion is fluvially transported to the continental margins the present study constitutes the first comparative assessment of the contribution of this charred material generally black carbon bc to marine sediments of the inner continental shelf of the gulf of cadiz goc given the ambiguity of bc definition and the heterogeneity of quantification techniques four of the most common and well established methodologies were applied to obtain a representative range of the bc content on four surface sediments chemical thermal oxidation gbc molecular markers benzenopolycarboxylic acids bpca thermogravimetry coupled to mass spectrometry tg dsc qms and chemical oxidation with sodium chlorite the bc results obtained for the goc sediments are compared and the applicability of each technique on marine sediments is discussed the mean bc values of the four methods 4 4 14 4 total organic carbon were within ranges previously reported for marine sediments from diverse origins however a large variability was observed within individual samples when comparing the bc results obtained with the four methods relative standard deviation from 31 to 75 the bpca approach produced the highest bc values whereas the gbc method the lowest this reflects the analytical variability derived from the different windows composing the bc continuum the results derived from the tg dsc qms application generated certain uncertainties despite the correction factor introduced to reduce the bc overestimation previously reported for this method considerable differences in the bc content of spatially close samples evidenced the complexity of coastal currents and sediment fluxes in the area suggesting the existence of other factors affecting the bc distribution the lack of correlation between the bc and toc as well as between the bc and lignin contents in all samples ruled out the occurrence of charring artifacts preferential degradation and or erosion of bc could explain the bc distribution in the area the use of ancillary terrigenous biomarkers lignin and inorganic silica pointed to a preferential fluvial transport of the terrestrial organic matter and indicated that the longer distance from the source the greater degradation of the om in addition the northern dominant winds in the region may have favored the additional introduction of airborne transported bc in the marine system

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

crustal investigation of the hellenic subduction zone using wide aperture seismic data abstract we present the results of a wide aperture seismic onshore offshore study crete seismic experiment in the cretan region as part of the hellenic arc compressional system three seismic lines were carried out on and around the island of crete in order to investigate the crustal structure of the region up to 119 three component recording stations were deployed on each profile that observed seismic energy generated by a 48 l airgun array and eight 20 kg landshots a total of 6208 shots were fired upon completing the fieldwork the vertical components of all stations were evaluated 300 common receiver gather crg sections of the ocean bottom seismographs obs and land stations as well as 100 common source gather csg sections of the land shots and selected airgun shots were compiled and modeled in order to generate a 2d p wave velocity depth model for each profile the accuracy of the model depends on the depth and position along the profiles and does not exceed 5 for both depth and p wave velocity we identified strong lateral variations in crustal and sedimentary thickness mainly in a north south direction but also along strike east west the crust is continental and has a maximum thickness of 32 5 km below northern central crete its subdivision in an upper v p 5 8 6 3 km s locally up to 6 5 km s and a lower v p 6 4 6 9 km s part is justified by a first order discontinuity with v p velocity a contrast of up to 0 6 km s the eastern part of crete shows a significantly thinner crust of 24 to 26 km to the north the crustal thickness decreases to 15 km below the central cretan sea the prominent decrease of the moho depth north of central crete is interpreted to represent the northern end of a microcontinent that was subducted in oligocene times and later surfaced by buoyant escape stockhert et al 1999 thomson et al 1999 the p t t d history of the high pressure rocks of crete greece denudation by buoyant escape in exhumation processes normal faulting ductile flow and erosion ring u lister g willet s brandon m eds spec publ of the geol soc of london p 154 to the south and southwest of the island the continental crust gradually thins to a minimum of 17 km and at approximately 100 km off the southern coast of crete it is in contact with oceanic crust below the mediterranean ridge upper mantle velocities were determined to be 7 7 km s below the cretan sea and 8 0 km s south of crete below the continental cretan crust a 6 to 7 km thick layer with v p velocities between 6 6 and 7 1 km s was identified on each line and could be followed by reflections to a depth of 42 km it is decoupled from the overlying continental crust at central crete and is interpreted as oceanic crust presently under subduction towards the nne below the aegean sea

comparison of quantification methods to measure fire derived black elemental carbon in soils and sediments using reference materials from soil water sediment and the atmosphere black carbon bc the product of incomplete combustion of fossil fuels and biomass called elemental carbon ec in atmospheric sciences was quantified in 12 different materials by 17 laboratories from different disciplines using seven different methods the materials were divided into three classes 1 potentially interfering materials 2 laboratory produced bc rich materials and 3 bc containing environmental matrices from soil water sediment and atmosphere this is the first comprehensive intercomparison of this type multimethod multilab and multisample focusing mainly on methods used for soil and sediment bc studies results for the potentially interfering materials which by definition contained no fire derived organic carbon highlighted situations where individual methods may overestimate bc concentrations results for the bc rich materials one soot and two chars showed that some of the methods identified most of the carbon in all three materials as bc whereas other methods identified only soot carbon as bc the different methods also gave widely different bc contents for the environmental matrices however these variations could be understood in the light of the findings for the other two groups of materials i e that some methods incorrectly identify non bc carbon as bc and that the detection efficiency of each technique varies across the bc continuum we found that atmospheric bc quantification methods are not ideal for soil and sediment studies as in their methodology these incorporate the definition of bc as light absorbing material irrespective of its origin leading to biases when applied to terrestrial and sedimentary materials this study shows that any attempt to merge data generated via different methods must consider the different operationally defined analytical windows of the bc continuum detected by each technique as well as the limitations and potential biases of each technique a major goal of this ring trial was to provide a basis on which to choose between the different bc quantification methods in soil and sediment studies in this paper we summarize the advantages and disadvantages of each method in future studies we strongly recommend the evaluation of all methods analyzing for bc in soils and sediments against the set of bc reference materials analyzed here

modulation of magmatic processes by co2 flushing abstract magmatic systems are the engines driving volcanic eruptions and the source of fluids responsible for the formation of porphyry type ore deposits sudden variations of pressure temperature and volume in magmatic systems can produce unrest which may culminate in a volcanic eruption and or the abrupt release of ore forming fluids such variations of the conditions within magmatic systems are commonly ascribed to the injection of new magma from depth however as magmas fractionating at depth or rising to the upper crust release co2 rich fluids the interaction between carbonic fluids and h2o rich magmas stored in the upper crust co2 flushing must also be a common process affecting the evolution of subvolcanic magma reservoirs here we investigate the effect of gas injection on the stability and chemical evolution of magmatic systems we calculate the chemical and physical evolution of magmas subjected to co2 flushing using rhyolite melts we compare the calculations with a set of melt inclusion data for mt st helens merapi etna and stromboli volcanoes we provide an approach that can be used to distinguish between melt inclusions trapped during co2 flushing magma ascent and decompression or those affected by post entrapment h2o loss our results show that co2 flushing is a widespread process in both felsic and mafic magmatic systems depending upon initial magma crystallinity and duration of co2 input flushing can either lead to volcanic eruption or fluid release we suggest that co2 flushing is a fundamental process modulating the behaviour and chemical evolution of crustal magmatic systems

p and s deep velocity structure of the hellenic area obtained by robust nonlinear inversion of travel times we derived a new model for the p and s velocity structure of the lithosphere in the subduction area of the hellenic arc and the aegean sea from the inversion of travel times of local events the inversion technique applied is nonlinear since three dimensional ray tracing is incorporated at the same time an appropriate preconditioning of the final linearized system is used in order to reduce ray density effects on the results the p s coherency is controlled by an additional damping of the vp vs ratio the study focuses mainly on the structure of the hellenic subduction in the southern aegean region interesting features and details of the subducted slab can be recognized in the final tomographic images on the western part the shallower section of the slab is dipping at a very small angle 10 this changes to approximately 25 for the deeper part of the subduction resulting in a prominent kink at a depth of about 70 km which is in accordance with the general characteristics of the associated benioff zone the smaller eastern part of the slab is not resolved with the same detail but a clearly steeper subduction zone can be recognized moreover detailed information about the crustal thickness variations are inferred from the velocity structure and correlate very well with the existing results from refraction experiments finally the results confirm the recent suggestion concerning the existence of a low velocity crustal layer at shallow depths 10 15 km in the accretionary prism of the alpine belt

burial of terrestrial organic matter in marine sediments a re assessment 1 calculations based on recent observations indicate that approximately one third of the organic matter presently being buried in marine sediments may be of terrestrial origin with the majority of this terrestrial organic matter tom burial occurring in muddy deltaic sediments these calculations further suggest that the remineralization of terrestrial organic matter in the oceans is also much less efficient than that of marine organic matter these two underappreciated observations have important implications in terms of our understanding of the controls on the global carbon cycle from a paleoceanographic perspective the results presented here also suggest that changes in tom burial on glacial interglacial timescales have the potential to impact the global carbon cycle i e atmospheric co2 levels

microseismic activity and seismotectonics of heraklion area central crete island greece abstract a seismological network of 10 portable analogue stations was installed in the area of heraklion central crete from september to december 1995 during this period more than 1000 events were recorded by at least 4 stations with magnitudes ranging from 0 5 to 4 6 and depths up to 70 km analysis of 336 well located events revealed high seismic activity in the onshore area seismicity is shallow

characterization of siberian arctic coastal sediments implications for terrestrial organic carbon export surface sediments were collected during the 2000 transarctic expedition along the siberian arctic coastline including the ob yenisey khatanga lena and indigirka estuaries sediments were chara

application of pmf receptor model merging with pahs signatures for source apportionment of black carbon in the continental shelf surface sediments of the bohai and yellow seas china black carbon bc and polycyclic aromatic hydrocarbons pahs are byproducts generated from the incomplete combustion of organic materials including fossil fuels and biomass the similar production processes shared by bc and pahs provide the possibility to infer the bc sources using the pahs signatures this study successfully utilized data sets of bc and pahs analyzed from the continental shelf surface sediments of the bohai and yellow seas to a standard receptor model of positive matrix factorization pmf to apportion the sources of bc in the sediment matrix results showed that combustion of fossil fuels i e coal and oil petroleum accounted for an average level of 83 5 of the total bc preserved which was significantly higher than that from the biomass burning 17 5 the spatial distributions of the fossil bc concentrations and percentages differed significantly from those of the biomass bc implying their different geochemical behaviors in the continental shelf regimes and further emphasizing the importance to effectively differentiate between fossil bc and biomass bc in addition to the relative proportions of the bc subtypes char bc soot bc the regional specific hydrodynamic conditions including the cold cyclonic eddy resuspension and coastal current also exerted a significant influence on these spatial variations

seismicity of the hellenic subduction zone in the area of western and central crete observed by temporary local seismic networks temporary local seismic networks were installed in western crete in central crete and on the island gavdos south of western crete respectively in order to image shallow seismically active zones of the hellenic subduction zone more than 4000 events in the magnitude range between 0 5 and 4 8 were detected and localized the resulting three dimensional hypocenter distribution allows the localization of seismically active zones in the area of western and central crete from the mediterranean ridge to the cretan sea furthermore a three dimensional structural model of the studied region was compiled based on results of wide angle seismics surface wave analysis and receiver function studies the comparison of the hypocenter distribution and the structure has allowed intraplate and interplate seismicity to be distinguished high interplate seismicity along the interface between the subducting african lithosphere and the aegean lithosphere was found south of western crete where the interface is located at about 20 to 40 km depth an offset between the southern border of the aegean lithosphere and the southern border of active interplate seismicity is observed in the area of crete the offset varies laterally along the hellenic arc between about 50 and 70 km a southwards dipping zone of high seismicity within the aegean lithosphere is found south of central crete in the region of the ptolemy trench it reaches from the interface between the plates at about 30 km depth towards the surface in comparison the aegean lithosphere south of western crete is seismically much less active including the region of the ionian trench intraplate seismicity within the aegean plate beneath crete and north of crete is confined to the upper about 20 km between 20 and 40 km depth beneath crete the aegean lithosphere appears to be seismically inactive in western crete the southern and western borders of this aseismic zone correlate strongly with the coastline of crete

asian dustfall in the st elias mountains yukon canada in april 2001 a major atmospheric dustfall event occurred in the st elias mountains yukon territory canada field samples were collected and analyzed for particle size mineralogy chemical composition and sr nd and pb isotopes dusts found above 3000 m had their source in the gobi desert region of northern china and inner mongolia and were transported to the yukon following a series of major dust storms that took place in early april dusts found below 3000 m had local yukon or mixed source s the asian dusts had a modal volume diameter of 4 m typical of far traveled mineral aerosols however larger 10 m particles were also found at 5000 m suggesting a very rapid trans pacific transport in the mid troposphere we estimate that the april 2001 event deposited from 5500 to 6335 tons of dust over an area of 21 000 km2 in the southwestern yukon most of which probably fell within a week our findings are consistent with instrumental observations and model simulations of the april 2001 event while the dust cloud was reportedly mixed with volatile pollutants from asia we found no evidence of metal pollution associated with the dustfall in the yukon our findings contribute to clarify the dynamics and the geochemical impact of asian dust long range transport events and to better estimate eolian fluxes of dustborne elements e g fe to the ocean associated with such events they may also assist in identifying past asian dust events in ice cores drilled from the st elias mountains icefields to develop a long term record of their frequency magnitude and source s

s p wave traveltime residuals from earthquakes and lateral inhomogeneity in the upper mantle beneath the aegean and the hellenic trench near crete

abundance distribution and isotopic composition of particulate black carbon in the northern gulf of mexico there exists increasing evidence supporting the important role of black carbon in global carbon cycles particulate black carbon pbc is allochthonous and has distinct reactivities compared to the bulk particulate organic carbon tot poc in marine environments however the abundance geochemical behavior of pbc and its importance in oceanic carbon budget remain poorly understood here we report the abundance distribution and stable isotopic signatures of bc derived from the chemo thermal oxidation cto 375 method bccto in the gulf of mexico our results show that bccto abundance decreased from shelf to basin and more than a half of riverine bccto could be removed over the shelf moreover bccto is much more refractory compared to the tot poc and has 13c values lower than those of bc excluded poc these results highlight the significance of pbc in marine carbon cycles and potentially suggest the need for a new end member term in quantifying poc sources in the ocean

intermediate depth seismicity in the aegean defined by teleseismic data the most reliably located intermediate depth earthquakes in the aegean area selected from the international seismological centre catalogue deepen towards the internal part of the hellenic arc and reach a maximum depth of 150 km during the last 20 years most have occurred at the eastern and western ends of the arc and very little activity is found in the middle area north of crete the seismic zone defines a contorted slab of lithosphere in the western part a very shallow dipping seismic zone extends 200 km northeast from the trench and then steepens abruptly at depths of about 50 80 km eventually reaching dips of 45 the 100 km and 150 km isodepth contours are not parallel to the hellenic trench in the western part the geometry of the slab is more consistent with a south southwestward translation of the aegean arc with respect to the african plate than with a rotation around a pole located close to the aegean region

black carbon in soils and sediments analysis distribution implications and current challenges this review highlights the ubiquity of black carbon bc produced by incomplete combustion of plant material and fossil fuels in peats soils and lacustrine and marine sediments we examine various definitions and analytical approaches and seek to provide a common language bc represents a continuum from partly charred material to graphite and soot particles with no general agreement on clear cut boundaries formation of bc can occur in two fundamentally different ways volatiles recondense to highly graphitized soot bc whereas the solid residues form char bc both forms of bc are relatively inert and are distributed globally by water and wind via fluvial and atmospheric transport we summarize chronologically the ubiquity of bc in soils and sediments since devonian times differentiating between bc from vegetation fires and from fossil fuel combustion bc has important implications for various biological geochemical and environmental processes as examples bc may represent a significant sink in the global carbon cycle affect the earth s radiative heat balance be a useful tracer for earth s fire history build up a significant fraction of carbon buried in soils and sediments and carry organic pollutants on land bc seems to be abundant in dark colored soils affected by frequent vegetation burning and fossil fuel combustion thus probably contributing to the highly stable aromatic components of soil organic matter we discuss challenges for future research despite the great importance of bc only limited progress has been made in calibrating analytical techniques progress in the quantification of bc is likely to come from systematic intercomparison using bcs from different sources and in different natural matrices bc identification could benefit from isotopic and spectroscopic techniques applied at the bulk and molecular levels the key to estimating bc stocks in soils and sediments is an understanding of the processes involved in bc degradation on a molecular level a promising approach would be the combination of short term laboratory experiments and long term field trials

major and trace elements δ13c and polycyclic aromatic hydrocarbons in the late pleistocene ice wedges a case study of batagay yedoma central yakutia abstract we studied the ionic composition of ice the content of suspended and dissolved trace and major elements in ice values of 13 and the composition of pahs of inclusions in the late pleistocene syngenetic ice wedges of the batagay yedoma for the first time the complex geochemical study of batagay megaslump was carried out the ice of the upper and lower complex of different ages was studied mineralisation of the late pleistocene ice wedges of batagay yedoma ranges from 66 56 to 424 8 mg l 1 from ultrafresh to desalinated the ionic composition of the ice is bicarbonate calcium and corresponds to snow formed under the influence of continental air masses the proportion of ca contained in dissolved form is not more than 20 30 as for the other elements the proportion of mg k na al fe mn sr ba in suspended form is greater than 90 the content of trace elements in inclusions in ice wedges and soils is equal which confirms the pedogenic origin of the inclusions in ice according to our data values of 13 in lipids of the pedogenic material in ice decrease with depth the lowest values values of 13 less than 30 were observed in the ice wedge of the upper complex at a depth of 7 4 8 6 m the increase of 13c values of lipids from pedogenic material in ice wedges with depth is due to the landscape change from grassland ecosystems to forest ecosystems and may also be influenced by the increased frequency of fires that occurred during the transition to forest ecosystems and the disappearance of large herbivores

bite profiles of some benthic grab samplers abstract the bite profiles of six 0 1 m 2 benthic grab samplers were reconstructed from video recordings of closure the petersen and the chain rigged van veen grabs both took shallow bites of variable profile the day and the smith mcintyre grabs both took fairly deep and consistent bites but were prevented by their frames from using their momentum on landing to increase penetration two designs of warp rigged van veen grab both took deep parallel sided bites the long arm warp rigged van veen was the only grab to collect sediment from a depth of at least 50 mm over the entire 0 1 m 2 sampled a bucket shape designed to optimise penetration and minimise upwards movement on closure is suggested

distribution input pathway and mass inventory of black carbon in sediments of the gulf of thailand se asia the coastal margins around southeast asia se asia may serve as an ideal location to study the source sink process of sedimentary black carbon bc because se asia has been identified as one of the major bc emission source regions in the world this study provides an extensive picture of recent regional scale sedimentary bc sequestration in the gulf of thailand got a tropical marine system in se asia generally the sedimentary bc concentrations 0 07 3 99 mg g were in the low to moderate ranges of those obtained in other coastal sediments around the world regional variability of the bc and its correlation with the sediment grain size and total organic carbon toc content indicated a general hydrodynamic constraint on bc occurrence in the lower gulf in contrast to the upper gulf with a more source dependence due to the direct land based input bc toc values and the varied bc components char and soot as well as their correlations suggested that char was the predominant constituents of sedimentary bc both in the upper and lower gulf which could be mainly derived from biomass burning and entered into the nearshore region through direct fluvial transport and surface run off the estimated bc burial flux similar to 212 mu g cm 2 y and mass inventory similar to 200 gg y in the got on the hundred year timescale were of the same order of magnitude compared with other oceanic margins and thus the tropical shelf sediments from se asia could serve as an important sink of land emitted bc c 2015 elsevier ltd all rights reserved

the sequestration sink of soot black carbon in the northern european shelf sediments 1 to test the hypothesis that ocean margin sediments are a key final repository in the large scale biogeospheric cycling of soot black carbon soot bc an extensive survey was conducted along the 2 000 km stretch of the swedish continental shelf scs the soot bc content in the 120 spatially distributed scs sediments was 0 180 130 26 dw median with interquartile ranges corresponding to 5 of total organic carbon using side scan sonar constraints to estimate the areal fraction of postglacial clay sediments that are accumulation bottoms 15 of scs the soot bc inventory in the scs mixed surface sediment was estimated at 4 000 gg combining this with radiochronological constraints on sediment mass accumulation fluxes the soot bc sink on the scs was 300 gg yr which yielded an area extrapolated estimate for the northern european shelf nes of 1 100 gg yr this sediment soot bc sink is 50 times larger than the river discharge fluxes of soot bc to these coastal waters however of similar magnitude as estimates of atmospheric soot bc emission from the upwind european continent while large uncertainties remain regarding the large scale to global bc cycle this study combines with two previous investigations to suggest that continental shelf sediments are a major final repository of atmospheric soot bc future progress on the soot bc cycle and how it interacts with the full carbon cycle is likely to benefit from14c determinations of the sedimentary soot bc and similar extensive studies of coastal sediment in complementary regimes such as off heavily soot bc producing areas in s and e asia and on the large pan arctic shelf

carbon isotope geochemistry of the santa clara river the santa clara river is a prototypical small mountainous river with a headwater height greater than 1000 m and a basin area smaller than 10 000 m 2 although individual small mountainous rivers export trivial amounts of sediment and carbon to the ocean as a group these rivers may export a major fraction as much as 50 of the total global river sediment flux milliman and syvitski 1992 making their geochemistry relevant the study of the ocean s carbon cycle in addition many small rivers export sediment in a few high flux events causing massive sporadic discharge of carbon onto coastal shelves discharge conditions very different from those of large rivers this class of rivers is an end member of the river ocean carbon exchange system opposite the earth s largest river the amazon the carbon mass and isotopic properties of the santa clara river are significantly different from previously studied large rivers during the 1997 1998 winter all santa clara carbon pools were old with flux weighted average l4c values of 428 76 for particulate organic carbon 73 31 for dissolved organic carbon and 644 58 for black carbon the age of exported carbon is primarily due to the deep erosion of old soils and not to inclusion of fossil fuel carbon additionally the 13c signatures of exported carbon pools were high relative to terrestrial carbon bearing a signature quite similar to marine carbon average particulate organic carbon poc 13c 22 2 0 8 the santa clara s estuary is small and drains onto the narrow eastern pacific coastal margin exporting this old soil organic matter directly into the ocean if the santa clara export patterns are representative of this class of rivers they may be a significant source of refractory terrestrial carbon to the ocean

pan arctic patterns in black carbon sources and fluvial discharges deduced from radiocarbon and pah source apportionment markers in estuarine surface sediments 1 a pan arctic geospatial picture of black carbon bc characteristics was obtained from the seven largest arctic rivers by combining with molecular combustion markers polycyclic aromatic hydrocarbons and radiocarbon 14c analysis the results suggested that the contribution from modern biomass burning to bc ranged from low in the yukon 8 and lena 5 rivers to high in the yenisey river 88 the mackenzie river contributed almost half of the total arctic fluvial bc export of 202 kton a 1 kton 109 g with the five russian arctic rivers contributing 10 36 kton a 1 each the 14c based source estimate of fluvially exported bc to the arctic ocean weighted by the riverine bc fluxes amount to about 20 from vegetation biofuel burning and 80 from 14c extinct sources such as fossil fuel combustion and relict bc in uplifted source rocks combining these pan arctic data with available estimates of bc export from other rivers gave a revised estimate of global riverine bc export flux of 26 103 kton a 1 this is twice higher than a single previous estimate and confirms that river export of bc is a more important pathway of bc to the oceans than direct atmospheric deposition

coastal erosion vs riverine sediment discharge in the arctic shelf seas this article presents a comparison of sediment input by rivers and by coastal erosion into both the laptev sea and the canadian beaufort sea cbs new data on coastal erosion in the laptev sea which are based on field measurements and remote sensing information and existing data on coastal erosion in the cbs as well as riverine sediment discharge into both the laptev sea and the cbs are included strong regional differences in the percentages of coastal erosion and riverine sediment supply are observed the cbs is dominated by the riverine sediment discharge 64 45 106 t a 1 mainly of the mackenzie river which is the largest single source of sediments in the arctic riverine sediment discharge into the laptev sea amounts to 24 10 106 t a 1 more than 70 of which are related to the lena river in comparison with the cbs the laptev sea coast on average delivers approximately twice as much sediment mass per kilometer a result of higher erosion rates due to higher cliffs and seasonal ice melting in the laptev sea sediment input by coastal erosion 58 4 106 t a 1 is therefore more important than in the cbs and the ratio between riverine and coastal sediment input amounts to 0 4 coastal erosion supplying 5 6 106 t a 1 is less significant for the sediment budget of the cbs where riverine sediment discharge exceeds coastal sediment input by a factor of ca 10

the ad 365 crete earthquake and possible seismic clustering during the fourth to sixth centuries ad in the eastern mediterranean a review of historical and archaeological data abstract historical and archaeological data are used to test geological claims that in the fourth to sixth centuries ad the eastern mediterranean experienced an unusual clustering of destructive earthquakes the early byzantine tectonic paroxsym a review of historical accounts of a notable earthquake at this time that of 21 july ad 365 indicates that this event destroyed nearly all the towns in crete and was followed by a tsunami which devastated the nile delta the ad 365 event was also probably responsible for reported or observed destruction in ancient towns of west cyprus and libya this earthquake is most likely to be identified with a hellenic arc subduction zone event of great m 8 magnitude as testified by up to 9 m of uplift in western crete dated by previous geological studies to around this time historical and archaeological data also support the hypothesis that the fourth to sixth centuries ad was a period of abnormally high seismicity in the eastern mediterranean the high seismicity rates of this period may reflect a reactivation of all plate boundaries in the region dead sea transform east anatolian fault north anatolian fault hellenic arc cyprus arc fault

travel time tomography of the european mediterranean mantle down to 1400 km abstract the 3 d p wave velocity structure of the mantle below europe the mediterranean region and a part of asia minor is investigated this study is a considerable extension of an earlier tomographic experiment that was limited to imaging upper mantle structure only here the earth s volume under study encompasses the mantle to a depth of 1400 km and we increase the number of international seismological centre isc data for inversion by a factor of four by taking more years of observation and by including data from teleseismic events the most important departure from the earlier study is that we do not use the jeffreys bullen model as a reference model but an improved radially symmetric velocity model the pm2 model which is appropriate for the european mediterranean mantle our inversion procedure consists of two steps first the radial model pm2 is determined from the isc delay times by a nonlinear trial and error inversion of the data as opposed to the jeffreys bullen model the new reference model has a high velocity lithosphere a low velocity zone and seismic discontinuities at depths of 400 and 670 km next the isc data are corrected for effects related to the change in reference model and inverted for 3 d heterogeneity relative to the pm2 model we follow this two step approach to attain a better linearizable tomographic problem in which ray paths computed in the pm2 model provide a better approximation of the actual ray paths than those computed from the jeffreys bullen model hence the two step scheme leads to a more credible application of fermat s principle in linearizing the tomographic equations inversion results for the 3 d heterogeneity are computed for both the uncorrected isc data and for the pm2 data the data fit obtained in the two step approach is slightly better than in the inversion of isc data using the jeffreys bullen reference model a comparison of the tomographic results demonstrates that the pm2 data inversion is to be preferred to assess the spatial resolution an analysis is given of hit count patterns sampling of the mantle by ray paths and results of sensitivity tests with 3 d synthetic velocity models the spatial resolution obtained varies with position in the mantle and is studied both in map view and in cross section in the well sampled regions of the mantle the spatial resolution for larger scale structure can qualitatively be denoted as reasonable to good and at least sufficient to allow interpretation of larger scale anomalies a comparison is made of the results of this study with independent models of s velocity heterogeneity obtained in a number of investigations and with a prediction of the seismic velocity structure of the mantle computed from tectonic reconstructions of the mediterranean region in the context of this comparison interpretations of large scale positive anomalies found in the mediterranean upper mantle in terms of subducted lithosphere are given specifically addressed are subduction below southern spain below the western mediterranean and italy and below the aegean in the last region a slab anomaly is mapped down to depths of 800 km

flux and budget of bc in the continental shelf seas adjacent to chinese high bc emission source regions this study conducted the first comprehensive investigation of sedimentary black carbon bc concentration flux and budget in the continental shelves of bohai sea bs and yellow sea ys based on measurements of bc in 191 surface sediments 36 riverine water and 2 seawater samples as well as the reported data set of the atmospheric samples from seven coastal cities in the bohai rim bc concentrations in these matrices were measured using the method of thermal optical reflectance the spatial distribution of the bc concentration in surface sediments was largely influenced by the regional hydrodynamic conditions with high values mainly occurring in the central mud areas where fine grained particles median diameters 6 i e 0 0156mm were deposited the bc burial flux in the bs and ys ranged from 4 to 1100 mu g cm 2 yr and averaged 166200 mu g cm 2 yr which was within the range of burial fluxes reported in other continental shelf regimes the area integrated sedimentary bc sink flux in the entire bs and ys was 325gg yr and the bs alone contributed 50 157gg yr the bc budget calculated in the bs showed that atmospheric deposition riverine discharge and import from the northern yellow sea nys each contributed 51 47 and 2 therefore atmospheric deposition and riverine discharge dominated the total bc influx 98 sequestration to bottom sediments was the major bc output pattern accounting for 88 of the input bc water exchange between the bs and the nys was also an important bc transport route with net bc transport from the bs to the nys