late miocene environmental change in nepal and the northern indian subcontinent stable isotopic evidence from paleosols neogene sediments belonging to the siwalik group crop out in the himalayan foothills along the length of southern nepal carbon and oxygen isotopic analyses of siwalik paleosols from four long siwalik sections record major ecological changes over the past 11 m y the carbon isotopic composition of both soil carbonate and organic matter shifts dramatically starting ca 7 0 ma marking the displacement of largely c3 vegetation probably semi deciduous forest by c4 grasslands by the beginning of the pliocene all the flood plains of major rivers in this region were dominated by monsoonal grasslands the floral shift away from woody plants is also reflected by the decline and final disappearance of fossil leaves and the decrease in coal logs in the latest miocene a similar carbon isotopic shift has been documented in the paleosol and fossil tooth record of pakistan and in terrigenous organic matter from the bengal fan showing that the floral shift was probably continentwide the latest miocene also witnessed an average change of 4 in the oxygen isotopic composition of soil carbonate as observed previously in pakistan the reasons for this are unclear if not diagenetic a major environmental change is indicated perhaps related to that driving the carbon isotopic shift recently described pollen and leaf fossils from the surai khola section show that evergreen forest was gradually displaced by semi deciduous and dry deciduous forest between 11 and 6 ma the gradual nature of this floral shift which culminated in the rapid expansion of c4 grasses starting 7 0 m y ago is difficult to explain by a decrease in atmospheric pco2 alone cerling et al 1993 but fits well with a gradual onset of monsoonal conditions in the late miocene in the northern indian subcontinent himalayan uplift driving both monsoonal intensification and consumption of co2 through weathering may be the common cause behind major late miocene environmental change globally however the decline of effective moisture associated with monsoon development has probably slowed not increased the rate of consumption of co2 by chemical weathering of himalayan sediments

deposition and modification of a flood layer on the northern california shelf lessons from and about the fate of terrestrial particulate organic carbon the 1995 flood of the eel river in northern california provided an opportunity to follow the short term history of riverine particulate matter on a continental shelf particulate organic carbon including both vascular plant debris and soil carbon was utilized as a tracer of the distribution and modification of the shelf flood deposit these components were sorted during initial emplacement of the deposit both in the river plume and in the benthic boundary layer during the 8 months following the flood lateral transport shallow burial and bioturbation contributed to spatial changes in the amount and character of carbon in the flood deposit study of the deposit suggests that this and previous flood layers may be preserved in the shelf and upper slope stratigraphic record as clay rich beds with relatively high carbon to nitrogen ratios and more negative 13c values than background non flood sediment concentrations of vascular plant debris are locally characteristic of such layers and may serve as distinctive stratigraphic markers investigation of organic carbon in the 1995 flood layer on the eel river shelf provides insight into the fate of terrestrial particulate carbon on continental margins in general flooding of the eel river and of similar river systems draining mountainous terrains introduces large quantities of terrestrial carbon to the marine environment and may favor the preservation of both terrestrial and marine carbon the abundant woody vascular plant debris discharged during floods is especially likely to survive oxidation and sulfate reduction in the shallower zones of the seabed this study reveals the dominant role that physical and biological processes may play in attenuating the terrestrial organic carbon signal on shelves over monthly to yearly time scales

the stable isotopic composition of modern soil carbonate and its relationship to climate the oxygen isotopic composition of modern soil carbonate is well correlated with the isotopic composition of local meteoric water the carbon isotopic cycle for co 2 in soils can be described in terms of the proportion of biomass using the c 4 photosynthetic pathway and the co 2 respiration rate of the soil at low soil respiration rates significant atmospheric co 2 mixing can occur in general the carbon isotopic composition of soil carbonate is related to the proportion of c 4 biomass present in soil but soils that freeze to the depth of carbonate formation often have a significant atmospheric component this suggests that freezing of the soil solution should be considered as another important mechanism for soil carbonate formation because of these relationships the isotopic composition of soil carbonate may be a paleoclimatic and paleoecologic indicator in cases in which diagenetic alteration has not occurred

organic carbon burial in fjords terrestrial versus marine inputs abstract fjords have been identified as sites of enhanced organic carbon oc burial and may play an important role in regulating climate change on glacial interglacial timescales understanding sediment processes and sources of sedimentary oc are necessary to better constrain oc burial in fjords in this study we use fiordland new zealand as a case study and present data on surface sediments sediment down cores and terrestrial end members to examine dynamics of sediments and the sources of oc in fjord sediments sediment cores showed evidence of multiple particle sources frequent bioturbation and mass wasting events a multi proxy approach stable isotopes lignin phenols and fatty acids allowed for separation of marine soil and vascular plant oc in surface sediments the relationship between mass accumulation rate mar and oc contents in fjord surface sediments suggested that mineral dilution is important in controlling oc content on a global scale but is less important for specific regions e g new zealand the inconsistency of oc budgets calculated by using mar weighted oc and oc accumulation rates ar 6 vs 21 31 tg oc yr 1 suggested that sediment flux in fjords was likely underestimated by using end member models we propose that 55 to 62 of total oc buried in fjords is terrestrially derived and accounts for 17 12 of the octerr buried in all marine sediments the strong correlation between mar and oc ar indicated that oc flux will likely decrease in fjords in the future with global warming due to decrease in sediment flux caused by glacier denudation

holocene climatic changes revealed by aeolian deposits from the qinghai lake area northeastern qinghai tibetan plateau and possible forcing mechanisms previous palaeoclimatic studies in the northeastern qinghai tibetan plateau netp during the holocene mainly using lake sediments have deepened our understanding of the climatic system in this remote region the timing and forcing mechanisms of climatic change in this region are still controversial however aeolian sand and silt deposits which are widely distributed in the netp can be readily dated by optically stimulated luminescence osl techniques and reveal the sensitive response of the landscape to climatic change in this study aeolian sand and loess at six sites around qinghai lake were studied to reconstruct millennial scale climatic changes during the holocene multiproxy data along with 24 osl age determinations show that low effective moisture and aeolian activity occurred at c 13 ka 10 9 1 ka and 8 9 7 8 ka periods of greater effective moisture may have occurred at 11 ka and 9 ka and there is evidence for a previously undocumented wet climate at 4 3 ka these results show that mi

proxy of monsoon seasonality in carbon isotopes from paleosols of the southern chinese loess plateau soil organic matter som and soil carbonate sc are common constituents in soils and are directly related to plant growth som accumulates gradually from the decomposition of plant material over time whereas sc formation is biased to dry season soil dissolved co 2 that derives from plant respiration during a drying phase of the growing season in some mixed c 3 c 4 environments the peak of c 3 and c 4 plant metabolism differs seasonally and the carbon source that contributes to the som and sc can be different consequently 13 som values reflect an annual average of the floral biomass but 13 sc values reflect a seasonal aspect of the plant community the relationship between 13 c sc and 13 c som is mainly controlled by how different the seasonal conditions are our results suggest that the relationship is a seasonal proxy that can be used to differentiate the seasonality effects of indian east asian and siberian monsoons on the chinese loess plateau during the last interglacial glacial cycle

geochemical and sedimentological considerations of a permanently anoxic fjord framvaren south norway abstract framvaren a fjord in south norway is an example of extreme anoxia due to the geomorphological features sill depth 2 m basin depth 180 m the postglacial history of framvaren is outlined emphasizing the preservation of environmental changes in the properties of the water and the sediments high levels of hydrogen sulfide in the water 170 180 ml l 1 or 7 8 mm h 2 s dense populations of photosynthetic bacteria at the redox boundary total number 3 10 6 ml 1 metal sulfide formation in the anoxic water e g framboidal pyrite and zinc sulfide and organic rich bottom sediments with high metal content e g 1000 ppm zn are typical examples the rate of sedimentation is estimated in three independent ways suggesting an average annual flux of 100 g m 2 yr 1 in the central basin of framvaren fluxes of organic matter and zinc to the sediments are calculated and compared with potential sources

sedimentary nitrogen isotopic ratio as a recorder for surface ocean nitrate utilization in two contrasting regions of the ocean the equatorial pacific and the southern ocean the 15n of core top sediments were strongly related to no3 in surface waters with distance from the equator in the equatorial pacific 15n increased from 7 to 16 as no3 decreased from 8 m to 0 1 m going from 60 to 30 s in the se indian ocean core top 15n increased from 5 to 11 as surface no3 decreased from 25 m to 0 1 m these results are strong evidence that sedimentary 15n in these regions is recording the increasing isotopic enrichment of near surface no3 with its depletion by phytoplankton in the case of the equatorial pacific 15n values for sinking particles collected at 150 m matched well the core top sediment values demonstrating little diagenetic alteration of the near surface generated isotopic signal these equatorial pacific data sets have variations with near surface no3 consistent with rayleigh fractionation kinetics for a fractionation factor u of 2 5 this value is substantially lower than previously found for temperate or polar regions perhaps as a result of differences in phytoplankton species assemblage or growth condition in the southern ocean south of the polar front comparison of 15n values for opal rich sediments south and sinking particles indicates an apparent 5 diagenetic enrichment relative to the surface generated signal that requires further investigation this exception aside our observations show that the surface water relationship of increasing 15n with increasing no3 depletion is generally transmitted to and preserved in the sediments an important requirement for further development and application of this important paleoceanographic tool

holocene climate changes over the desert loess transition of north central china a 2 m trench section at the desert loess transition of north central china was analyzed at 2 cm intervals for grain size distribution md m and total organic carbon toc ams 14c time series of the md and toc records provides direct information on variations of the east asian monsoon climate during the last 10 000 yr md is considered to represent the wind strength and high md reflects strong winter monsoon winds toc denotes the degree of vegetation cover a function of the intensity of summer monsoon circulations from ca 10 000 to 7000 cal yr bp the climate was dominated by a strong winter monsoon and a very weak summer monsoon as indicated by high md and low toc values subsequently climatic conditions became warmer gradually from ca 7000 to 5500 cal yr bp the period between ca 5500 and 2700 cal yr bp displayed the highest toc and lowest md values over the last 10 000 yr marking a stable state of a warm humid climate i e the holocene climatic optimum of china during the interval of ca 2700 1500 cal yr bp the expansion and intensification of agrarian activities could have led to desertification and acceleration of deposition of coarse grained particles resulting in a decreased organic carbon accumulation rate however the toc during this interval still has values as high as during the episode of ca 7000 5500 cal yr bp reflecting a relatively stronger summer monsoon circulation since ca 1500 cal yr ago high amplitude fluctuations of toc that fluctuate in phase with the clay size fraction imply that the climate experienced three major oscillations with a prominent peak of enhanced summer monsoon circulation at ca 1300 cal yr ago and with two intervals of increased winter monsoon strength occurring around ca 1000 and 300 cal yr ago the md and toc records over the past 5000 yr demonstrate a good correlation with the archaeological phenological and historical records of china climate changes in the east asian monsoon region were not only related to the changing seasonality of solar insolation resulting from progressive changes in the earth s orbital parameters but were also controlled by the pattern and intensity of the atmospheric circulation

sources sinks and subsidies terrestrial carbon storage in mid latitude fjords this work was supported by the natural environment research council grant number ne l501852 1 with additional support from the nerc life science mass spectrometry facility ceh l 098 11 2015 and the nerc geophysical equipment facility nggfsc minor loan 1031

control of dust emissions by geomorphic conditions wind environments and land use in northern china an examination based on dust storm frequency from 1960 to 2003 the degree to which dust emissions are controlled by geomorphic conditions wind environments and land use was investigated using the dust storm frequency dsf and data from more than 300 meteorological stations throughout northern china our analysis showed that most dust emissions originated in gobi deserts that developed in piedmont alluvial fans of the kunlun qilian and helan mountains dust emissions are low from other gobi desert regions such as the northern gurbantunggut and eastern taklimakan where high vegetation coverage restrained dust emissions or where dust size particles are not abundant after a long period of strong wind erosion sandy deserts with relatively high vegetation coverage or an extensive cover by mobile sands are not a major dust source although the highest dust emissions did not appear in regions with the highest wind energy dsf trends in each region from 1960 to 2003 were closely related to local wind activity dsf was low in regions with high levels of human activity where the mean dsf from 1960 to 2003 did not exceed 4 days year even from the 1960s to the early 1970s the period with the greatest dsf frequency did not exceed 8 days year which indicates that extensive land use did not contribute to dsf the low dsf in these areas might result from the fact that although land use could produce abundant fine soil fractions vegetation coverage and soil moisture remained higher than in the gobi deserts of arid china thereby decreasing dust storm occurrence

late quaternary aeolian activity in the mu us and otindag dune fields north china and lagged response to insolation forcing 1 dune fields in parts of northern china contain important stratigraphic records of late quaternary change in the east asian monsoon in this study 33 new optically stimulated luminescence osl ages and other measurements from aeolian sediment sections are used to reconstruct the timing of wet dry climate variation in the mu us and otindag dune fields of north china the results indicate dune activity and dry climate in the last few hundred years 14 ka to about 7 8 ka and 50 ka to 60 ka the dunes were mainly stable implying a wetter climate between about 7 8 ka and 2 4 ka these results imply a lag of several thousand years between peak summer insolation at 10 11 ka and high summer monsoon rainfall after 7 8 ka in the investigated regions the monsoon climate may not respond directly to orbital forcing over millennial time scales land surface feedbacks may account for lagged dune field response

lateglacial and holocene dune evolution in the horqin dunefield of northeastern china based on luminescence dating abstract the horqin dunefield is located in the northern frontier of east asian monsoon eam zone and its activation and stabilization is sensitive to the ebb and flow of the eam however the activity of dunes in the horqin dunefield is still poorly understood due to limited numerical dating the purpose of the present study is to establish the chronology using luminescence dating in order to understand dune evolution of the horqin dunefield and to explore the relative role of climate and human activity eighteen samples were collected from seven sections following a southwest northeast transect through the dunefield and dated using quartz optically stimulated luminescence osl combining evidence from stratigraphy and the luminescence chronology dune evolution within the horqin dunefield since the lateglacial can be summarized as before 9 6 ka aeolian sand dunes were mobilized during the period 9 6 3 ka dunes were stabilized at around 3 ka dunes were mobilized again abruptly since 3 ka there were multiple phases of dune stabilization mobilization dune activity was dominated by climate before 3 ka however since 3 ka both climate variability and human impact have influenced dune evolution in the horqin dunefield

multiple expansions of c4 plant biomass in east asia since 7 ma coupled with strengthened monsoon circulation the expansion of plants using the c4 photosynthetic pathway is one of the most prominent changes in the global ecosystem during the cenozoic era a significant late miocene expansion is well documented however the existence and cause of subsequent expansions are still not clear owing in part to the lack of long continuous climate vegetation records here we present two high resolution carbon isotope time series covering the past 7 m y derived from eolian deposits on the chinese loess plateau the data indicate three intervals of significant c4 plant expansions within the semiarid monsoonal region of east asia ca 2 9 2 7 ma 1 3 0 9 ma and 0 6 ma present these expansions covary with strengthened east asian summer monsoon circulation we conclude that in east asia large scale late miocene c4 c3 vegetation changes in semiarid areas have been primarily driven by warm seasonal precipitation and temperature variations associated with changes in monsoon circulation

stable oxygen and carbon isotope information on the establishment of a new opportunistic foraminiferal fauna in a swedish skagerrak fjord basin in 1979 1980 significant faunal changes reported fromrecent coastal environments which are not directly influenced by urban and industrial impact are rarely seen in gullmar fjord on the swedish west coast a significant foraminiferal fauna change occurred in connectionwith severe low oxygen conditions that evolved in thewinter of 1979 1980 a foraminiferal fauna marked by common skagerrak kattegat species which had previously characterised the deep fjord basin was replaced by the opportunistic low oxygen tolerant species stainforthia fusiformis williamsson to study this phenomenon further we performed stable oxygen and carbon isotope analyses on the indicator species itself s fusiformis both on specimens from sediment cores representing approximately the last 85 years and on living stained individuals taken from a transect across the deep fjord basin our purpose was to detail how and why s fusiformis came to dominate the fauna the oxygen isotope results suggest that salinities and temperatures in the deep basin have been relatively constant over the last c 85 years while the carbon isotopes show a significant change towards more negative values in association with the faunal shift of 1979 1980 the combined results from both the cores and the surface sediments suggest that s fusiformis did not inhabit the deep basin until 1980 before then almost all specimens of s fusiformis were small sized and their carbon isotope values suggest they were re deposited shallow water specimens that had been transported down to the central deep basin as part of a suspension load after a major faunal extinction in 1979 1980 s fusiformis of all sizes suddenly appeared in large numbers and their carbon isotopic values were similar to the signal from registered in the recent living fauna within the deep basin this suggests that the opportunistic s fusiformis established itself in the deep basin as a consequence of the severe low oxygen event and the faunal crash of the previously dominating skagerrak kattegat fauna less

centers of organic carbon burial and oxidation at the land ocean interface abstract continental margin systems collectively receive and store vast amounts of organic carbon oc derived from primary productivity both on land and in the ocean thereby playing a central role in the global carbon cycle the land ocean interface is however extremely heterogeneous in terms of terrigenous input marine primary productivity sediment transport processes and depositional conditions e g such as bottom water oxygen level continental margins are also highly dynamic with processes occurring over a broad range of spatial and temporal scales the rates of oc burial and oxidation are consequently variable over both space and time hindering our ability to derive a global picture of oc cycling at the land ocean interface here we review the processes controlling the fate of organic matter in continental margin sediments with a special emphasis on hot spots and hot moments of oc burial and oxidation we present a compilation of compositional data from a set of illustrative settings including fjords small mountainous river margins large deltaic systems and upwelling areas bulk oc stable isotope and radiocarbon compositions reveal the diversity and complexity characteristic of oc buried in marginal seas this primarily relates to differences in marine and terrestrial inputs the composition of the terrestrial component e g vascular plant oc soil and petrogenic oc inputs and processes modulating the fate of oc within the marine environment e g priming this widely contrasting behavior of oc among these systems illustrates that the reactivity of oc is a product of its chemical composition and regional conditions interpreted in the context of bulk compositional data as well as that obtained on specific molecular markers e g lignin derived phenols the possibility exists to tease apart complex mixtures of terrestrial and marine inputs and to shed light on the role of the myriad of depositional and post depositional processes finally we discuss a set of hot topics that warrant further investigation such as the role of photochemistry fungi halogenation and reactive iron in dictating the fate of oc in the changing coastal ocean

luminescence dating of sand loess sequences and response of mu us and otindag sand fields north china to climatic changes the sand loess transition zone in north china is sensitive to climate change and is an ideal place to investigate past environmental changes however past climate change at millennial centennial timescales in this region has not been well reconstructed because of limited numerical dating alternations of sandy loam soils with aeolian sand layers in the mu us and otindag sand fields which lie along the sand loess transition zone indicate multiple intervals of dune activity and stability this change is probably a response to variations of the east asian monsoon climate during the late quaternary the single aliquot regeneration sar optically stimulated luminescence osl dating protocol which has been successfully applied to aeolian deposits worldwide is applied to these two sand fields in this study the osl ages provide reliable constraints for reconstruction of past climate changes at suborbital timescale sections in both sand fields contain aeolian sand beds recording millennial scale episodes of dry climate and widespread dune activation including episodes at about the same time as heinrich event 5 and the younger dryas in the north atlantic region these results demonstrate the potential of aeolian sediments in semi arid north china to record millennial scale climatic events and also suggest that dry wet climate variation at the desert margin in china may be linked to climatic change elsewhere in the northern hemisphere through atmospheric circulation this article was published online on 27 november 2008 an error was subsequently identified this notice is included in the online and print versions to indicate that both have been corrected 16 december 2008 copyright 2008 john wiley sons ltd

climate induced changes in sedimentary regimes for organic matter supply on the continental shelf off northern norway abstract with this study i suggest that changes in biogeochemical processes in northern norwegian fjords during the last glacial interglacial transition 14 3 to 6 3 ka b p are predominantly climate induced variable strength in atlantic water inflow intrusion of arctic waters and sea ice coverage various nutrient supply as well as several re advances of continental ice sheets are recorded by both bulk organic and selected biomarkers in sediments of the andfjord stable isotope 13corg 15n and rock eval pyrolysis data indicate a strong supply of terrestrial organic matter during stadials e g younger dryas older dryas whereas enhanced input of marine organic matter prevailed during the interstadials bolling allerod profiles of selected biomarkers of marine origin show a characteristic climate induced variation during the whole time interval where relatively low concentrations of dinosterols and c37 alkenones may indicate similar to today a minor contribution of their respective plankton groups coccolithophorids dinoflagellates the prevalence of arctic waters and seasonal sea ice coverage during the younger dryas is indicated by a single maximum of 24 methylenecholesterol probably indicating the dominance of sea ice diatoms and or the prevalence of diatoms of thalassiosiraceae in surface waters the sediments of the allerod in contrast show a pronounced maximum in dinosterols indicating a better adaptation of dinoflagellates to an oceanic regime that is characterized by incipient intrusion of atlantic water highly variable sea surface temperatures and well stratified water masses the concentration of higher molecular weight n alkanes however follows the deglacial early holocene trend of climate amelioration from the last deglaciation to the middle holocene with maxima during ice advances stadials and minima during the middle holocene warm period these new results significantly improve the understanding of climate induced response on organic matter supply in fjords and provide a better knowledge of past variations of biogeochemical processes in high latitude coastal environments

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

sedimentation and diagenesis of chinese loess implications for the preservation of continuous high resolution climate records chinese loess has been extensively utilized to produce continuous and high resolution climate records of the late cenozoic such work assumes uninterrupted loess deposition and limited diagenesis here closely spaced optically stimulated luminescence osl dates are used to characterize the holocene and late pleistocene sedimentation histories of three sites across a nw se transect of the chinese loess plateau the results suggest that sedimentation is episodic at subglacial interglacial time scales with rates rapidly varying within units and between sites unconformities noneolian deposition and mixing of sediments also appear to be common existing understanding of loess deposition therefore requires reexamination while previous reconstructions of rapid climate change not dated using absolute methods should be regarded with caution loess deposits may still yield detailed climate records from specific high sedimentation rate strata and evidence for rapid climate change may yet be obtainable by targeting these units through absolute dating the rapid changes in sedimentation presented here indicate the east asian monsoon has the capacity to vary on millennial scales

sedimentary organic matter geochemistry of clayoquot sound vancouver island british columbia surface sediment samples from three interconnected fjords of clayoquot sound british columbia were density fractionated 1 6 g cm 3 to isolate discrete organic debris od from mineral associated organic matter mom total organic carbon oc values varied greatly ranging from 0 1 to 8 8 by weight with a general decreasing trend from fjord head to the continental shelf within the sediment terrestrial om was present either as vascular plant debris or soil mom down fjord the woody vascular plant material in the od fraction acquires nitrogen which is hypothesized to be due to the bacterial incorporation of nitrogen from the water terrestrial oc in the mom is incompletely replaced by marine oc within the fjords resulting in a 65 net loss of mom sediments deposited under oxic and intermittently anoxic water column conditions have organic carbon to surface area ratios oc sa ranging from 0 4 to 1 2 mg c m 2 similar to that of typical continental margin sediments given that temperate fjords contain an estimated 12 of the continental margin sediment deposited during the last 100 000 yr and that they bury at least a margin equivalent amount of oc either weight or surface area normalized we hypothesize that temperate fjords may contain 12 or more of the sedimentary oc buried during this time

re assessing the nitrogen signal in continental margin sediments new insights from the high northern latitudes organic and inorganic nitrogen and their isotopic signatures were studied in continental margin sediments off spitsbergen we present evidence that land derived inorganic nitrogen strongly dilutes the particulate organic signal in coastal and fjord settings and accounts for up to 70 of the total nitrogen content spatial heterogeneity in inorganic nitrogen along the coast is less likely to be influenced by clay mineral assemblages or various substrates than by the supply of terrestrial organic matter tom within eroded soil material into selected fjords and onto the shelf the 15 n signal of the inorganic nitrogen 15 ninorg in sediments off spitsbergen seems to be appropriate to trace tom supply from various climate and ecosystem zones and elucidates the dominant transport media of terrigenous sediments to the marine realm moreover we postulate that with the study of sedimentary 15 ninorg in the atlantic arctic gateway climatically induced changes in catchment s vegetations in high northern latitudes may be reconstructed the 15 norg signal is primarily controlled by the availability of nitrate in the dominating ocean current systems and the corresponding degree of utilization of the nitrate pool in the euphotic zone not only does this new approach allow for a detailed view into the nitrogen cycle for settings with purely primary produced organic matter supply it also provides new insights into both the deposition of marine and terrestrial nitrogen and its ecosystem response to paleo climate changes

a review of nitrogen isotopic alteration in marine sediments key points use of sedimentary nitrogen isotopes is examined on average sediment 15n 14n increases approx 2 per mil during early burial isotopic alteration scales with water depth abstract nitrogen isotopes are an important tool for evaluating past biogeochemical cycling from the paleoceanographic record however bulk sedimentary nitrogen isotope ratios which can be determined routinely and at minimal cost may be altered during burial and early sedimentary diagenesis particularly outside of continental margin settings the causes and detailed mechanisms of isotopic alteration are still under investigation case studies of the mediterranean and south china seas underscore the complexities of investigating isotopic alteration in an effort to evaluate the evidence for alteration of the sedimentary n isotopic signal and try to quantify the net effect we have compiled and compared data demonstrating alteration from the published literature a 100 point comparison of sediment trap and surface sedimentary nitrogen isotope values demonstrates that at sites located off of the continental margins an increase in sediment 15n 14n occurs during early burial likely at the seafloor the extent of isotopic alteration appears to be a function of water depth depth related differences in oxygen exposure time at the seafloor are likely the dominant control on the extent of n isotopic alteration moreover the compiled data suggest that the degree of alteration is likely to be uniform through time at most sites so that bulk sedimentary isotope records likely provide a good means for evaluating relative changes in the global n cycle

limited change in dune mobility in response to a large decrease in wind power in semi arid northern china since the 1970s abstract the climatic controls on dune mobility especially the relative importance of wind strength remain incompletely understood this is a key research problem in semi arid northern china both for interpreting past dune activity as evidence of paleoclimate and for predicting future environmental change potential eolian sand transport which is approximately proportional to wind power above the threshold for sand entrainment has decreased across much of northern china since the 1970s over the same period effective moisture ratio of precipitation to potential evapotranspiration has not changed significantly this natural experiment provides insight on the relative importance of wind power as a control on dune mobility in three dunefields of northern china mu us otindag and horqin although poorly understood and potentially large effects of human land use complicate interpretation dune forms in these three regions are consistent with sand transport vectors inferred from weather station data suggesting that wind directions have remained stable and the stations adequately represent winds that shaped the dunes the predicted effect of weaker winds since the 1970s would be dune stabilization with lower sand transport rates allowing vegetation cover to expand large portions of all three dunefields remained stabilized by vegetation in the 1970s despite high wind power since the 1970s trends in remotely sensed vegetation greenness and change in mobile dune area inferred from sequential landsat images do indicate widespread dune stabilization in the eastern mu us region on the other hand expansion of active dunes took place farther west in the mu us dunefield and especially in the central otindag dunefield with little overall change in two parts of the horqin dunes better ground truth is needed to validate the remote sensing analyses but results presented here place limits on the relative importance of wind strength as a control on dune mobility in the study areas high wind power alone does not completely destabilize these dunes a large decrease in wind power either has little short term effect on the dunes or more likely its effect is sufficiently small that it is obscured by human impacts on dune stability in many parts of the study areas

dune mobility and aridity at the desert margin of northern china at a time of peak monsoon strength wind blown sands were mobile at many sites along the desert margin in northern china during the early holocene 11 5 8 ka ago based on extensive new numerical dating this mobility implies low effective moisture at the desert margin in contrast to growing evidence for greater than modern monsoon precipitation at the same time in central and southern china dry conditions in the early holocene at the desert margin can be explained through a dynamic link between enhanced diabatic heating in the core region of the strengthened monsoon and increased subsidence in drylands to the north combined with high evapotranspiration rates due to high summer temperatures after 8 ka ago as the monsoon weakened and lower temperatures reduced evapotranspiration eolian sands were stabilized by vegetation aridity and dune mobility at the desert margin and a strengthened monsoon can both be explained as responses to high summer insolation in the early holocene

holocene east asian monsoon variation inferred from species assemblage and shell chemistry of the ostracodes from hulun lake inner mongolia a sediment core from hulun lake inner mongolia was analyzed for species assemblages and shell chemistry of ostracodes to investigate changes in the hydrology and climate of the east asian summer monsoon margin during the holocene darwinula stevensoni was abundant ilyocypris spp scarce littoral ostracodes absent and mg ca sr ca and 18o were low 11 100 to 8300 yr ago indicating high lake levels and cool fresh waters darwinula stevensoni declined largely ilyocypris spp throve littoral ostracodes were rare and chemical indicators remained in low values 8300 to 6200 yr ago suggesting that the lake continued high stands but water became warm the lake then contracted and water became cool brackish 6200 to 4300 yr ago littoral ostracodes flourished 4300 to 3350 yr ago marking the lowest lake levels of the entire holocene the lake level recovered and water salinity decreased 3350 to 1900 yr ago from 1900 to 500 yr ago the lake maintained the preceding status albeit lowered stands and increased salinities 1100 to 800 yr ago during the recent 500 yr the lake expanded and water salinity decreased the data imply that the east asian summer monsoon did not intensify until 8300 yr ago and weakened dramatically 4300 to 3350 yr ago

atmospheric forcing of the eastern tropical pacific a review abstract the increase in marine land surface atmospheric and satellite data during recent decades has led to an improved understanding of the air sea interaction processes in the eastern tropical pacific this is also thanks to extensive diagnoses from conceptual and coupled ocean atmosphere numerical models in this paper mean fields of atmospheric variables such as incoming solar radiation sea level pressure winds wind stress curl precipitation evaporation and surface energy fluxes are derived from global atmospheric data sets in order to examine the dominant features of the low level atmospheric circulations of the region the seasonal march of the atmospheric circulations is presented to depict the role of radiative forcing on atmospheric perturbations especially those dominating the atmosphere at low levels in the tropics the trade winds constitute an important north south energy and moisture exchange mechanism as part of the low level branch of the hadley circulation that determines to a large extent the precipitation distribution in the region i e that associated with the inter tropical convergence zone itcz monsoonal circulations also play an important role in determining the warm season precipitation distribution over the eastern tropical pacific through a large variety of air sea land interaction mechanisms westward traveling waves tropical cyclones low latitude cold air intrusions and other synoptic and mesoscale perturbations associated with the itcz are also important elements that modulate the annual rainfall cycle the low level jets of the gulf of california the intra americas sea gulf of mexico and caribbean sea and choco colombia are prominent features of the eastern tropical pacific low level circulations related to sub regional and regional scale precipitation patterns observations show that the intra americas low level jet intensity varies with el nino southern oscillation enso phases however its origin and role in the westward propagation and development of disturbances that may hit the eastern tropical pacific such as easterly waves and tropical cyclones are still unclear changes in the intensity of the trade winds in the caribbean sea and the gulf of mexico associated with eastern tropical pacific wind jets exert an important control on precipitation by means of wind topography interactions gaps in the mountains of southern mexico and central america allow strong wind jets to pass over the continent imprinting a unique signal in sea surface temperatures and ocean dynamics of the eastern tropical pacific the warm pools of the americas constitute an important source of moisture for the north american monsoon system the northeastern tropical pacific is a region of intense cyclogenetic activity just west of the coast of mesoamerica over the oceanic regions large scale properties of key variables such as precipitation moisture surface energy fluxes and wind stress curl are still uncertain which inhibits a more comprehensive view of the region and stresses the importance of regional field experiments progress has been substantial in the understanding of the ocean and atmospheric dynamics of the eastern tropical pacific however recent observational evidence such as that of a shallow meridional circulation cell in that region in contrast to the classic concept of the hadley type deep meridional circulation suggests that more in situ observations to validate theories are still necessary this paper is part of a comprehensive review of the oceanography of the eastern tropical pacific ocean

rayleigh distillation and the depth profile of 13c 12c ratios of soil organic carbon from soils of disparate texture in iron range national park far north queensland australia a depth and particle size specific analysis of soil organic carbon soc and its isotopic composition was undertaken to investigate the effects of soil texture or particle size on the depth profile of stable carbon isotopic composition of soc 13csoc in two tropical soils depth specific samples from two soil profiles of markedly different texture coarse grained and fine grained were separated into particle size classes and analyzed for the mass mass concentration of soc c and 13csoc within 1 m of the soil surface 13csoc in the coarse textured soil increases by 1 3 to 1 6 while 13csoc from the fine textured soil increase by as much as 3 8 to 5 5 this increasing depth trend in the coarse textured soil is approximately linear with respect to normalized c while the increase in the fine textured soil follows a logarithmic function with respect to normalized c a model of rayleigh distillation describing isotope fractionation during decomposition of soil organic matter som accounts for the depth profile of 13csoc in the fine textured soil but does not account for the depth profile observed in the coarse textured soil despite their similar climate vegetation and topographic position these results suggest that kinetic fractionation during humification of som leads to preferential accumulation of 13c in association with fine mineral particles or aggregates of fine mineral particles in fine textured soils in contrast the coarse textured soil shows very little applicability of the rayleigh distillation model rather the depth profile of 13csoc in the coarse textured soil can be accounted for by mixing of soil carbon with different isotopic ratios

lower temperature as the main cause of c4 plant declines during the glacial periods on the chinese loess plateau abstract the distribution of c3 and c4 plants changed in regionally contrasting ways during the last glacial period c4 plant expansion in low latitude africa and america coincided with c4 plant decreases in mesoamerica and the us great plains this c4 plant expansion has been attributed to lower pco2 and increased aridity and the decline in c4 plants is believed to have been caused by increased winter precipitation and lower temperatures however it is still difficult to generalize whether pco2 temperature or aridity was mainly responsible for c3 vs c4 vegetation changes during glacial periods paleoclimate conditions on the chinese loess plateau clp offer opportunities to further evaluate the role of temperature in the c3 vs c4 competition detailed climate records have shown that the clp region was drier and colder during glacial periods with aridity favoring c4 expansion and lower temperatures favoring c3 expansion here we present two high resolution compound specific carbon isotope records of n alkanes from the clp as vegetation biomarkers to estimate the relative abundance of c4 plants during the last two glacial interglacial transitions more negative 13c values during the glacial periods from two clp sites clearly show that in contrast with low latitude sites c4 plants declined this decrease in c4 abundance was caused by lower temperature despite the lower pco2 and increased aridity on the clp during glacial time

the vestfjorden traenadjupet palaeo ice stream drainage system mid norwegian continental shelf abstract an ice stream in the vestfjorden traenadjupet depressions off northern norway transported glacial debris to the shelf edge and into the deep sea during the last glaciation our interpretation is based mainly on regional and detailed bathymetry and 2d and 3d seismic data this palaeo ice stream was approximately 400 km long and covered an area of 20 000 km 2 including a complex system of tributary fjords and valleys in nordland county the drainage basin had an area of ca 150 000 km 2 within the fennoscandian ice sheet fis during the last glacial maximum lgm the location of the palaeo ice stream prevented large ice masses from reaching the montainous areas of lofoten and vesteralen a local ice dome was established in these areas the palaeo ice stream eroded extensively into both mesozoic and cenozoic sedimentary rocks and quaternary sediments a pattern of well developed subglacial sedimentary bedforms was produced e g mega scale lineations drumlins ice stream shear margin moraines are located on both sides of traenadjupet defining the width of the palaeo ice stream 90 km at the shelf edge these moraines are commonly 10 20 m high a few kilometres wide and reach several tens of kilometres in length a large recessional moraine the tennholmen ridge has been mapped in vestfjorden it is 80 m high 20 km wide and 60 km long we have interpreted this ridge as a grounding line moraine formed during a halt or a readvance of the ice stream during the last deglaciation the large transport of glacial debris towards the grounding line occurred during this stage northeast of the tennholmen ridge several smaller moraine ridges were developed at still stands during deglaciation

response of surface processes to climatic change in the dunefields and loess plateau of north china during the late quaternary this paper draws on recent optically stimulated luminescence osl dating to evaluate the long held assumption that dust accumulation rates in the loess plateau and the extent of active aeolian sand in the dunefields to the north have varied together over time because both are controlled by the strength of the asian monsoons and also possibly because the dunefields are proximal loess sources the results show there is little evidence that high rates of loess accumulation coincided with well dated episodes of extensive dune activity in the mu us otindag and horqin dunefields at 11 8 ka and 1 0 ka explanations for the apparent lack of coupling include local variation in the trapping of dust and post depositional preservation of the loess and dune sediments in response to varying local environmental conditions in addition a substantial portion of the loess may be transported directly from source areas where dust emission has somewhat different climatic and geomorphic controls than aeolian sand activity within the dunefields the results of this study cast doubt on the use of loess accumulation rate as a palaeoclimatic proxy at millennial timescale the dunefield and loess stratigraphic records are interpreted as primarily recording changes in effective moisture at a local scale but the timing of late quaternary dune activity along with a variety of other evidence indicates that moisture changes in many of the drylands of northern china may not be in phase with precipitation in core regions of the asian monsoons copyright 2011 john wiley sons ltd

spatial and temporal organic carbon burial along a fjord to coast transect a case study from western norway we investigated spatial and temporal changes in accumulation rate and source of organic carbon on a gradient along the lysefjord and the more coastal hogsfjord western norway this was achieved th

carbon cycling and burial in new zealand s fjords understanding carbon cycling in continental margin settings is critical for constraining the global carbon cycle here we apply a multiproxy geochemical approach to evaluate regional carbon cycle dynamics in six new zealand fjords using carbon and nitrogen concentrations and isotopes lipid biomarkers and redox sensitive element concentrations we show that the new zealand fjords have carbon rich surface sediments in basins that promote long term storage i e semirestricted basins with sediment accumulation rates of up to 4 mm yr 1 using 13c distributions to develop a mixing model we find that organic carbon in fjord sediments is well mixed from marine and terrestrial sources in down fjord gradients this is driven by high regional precipitation rates of 6 m yr 1 which promote carbon accumulation in fjord basins through terrestrial runoff in addition we have identified at least two euxinic subbasins based on uranium molybdenum iron and cadmium enrichment that contain 7 organic carbon because the strength and position of the southern hemisphere westerly winds control precipitation and fjord circulation carbon delivery and storage in the region are intimately linked to westerly wind variability we estimate that the fjord region 759 km2 may be exporting up to 1 4 107 kgc yr 1 outpacing other types of continental margins in rates of carbon burial by up to 3 orders of magnitude

factors controlling 13c contents of sedimentary organic compounds principles and evidence the carbon isotopic composition of any naturally synthesized organic compound depends on 1 the carbon source utilized 2 isotope effects associated with assimilation of carbon by the producing organism 3 isotope effects associated with metabolism and biosynthesis and 4 cellular carbon budgets these factors are reviewed and quantitative considerations summarized particularly with regard to active and passive modes of carbon assimilation by phytoplankton and the existence of discernible regularities in isotope effects associated with lipid biosynthesis it is concluded that n alkyl lipids are in general depleted in 13c by about 1 5 relative to polyisoprenoid lipids produced by the same organism the effects of biological reworking on isotopic compositions of organic carbon are examined and it is suggested that enrichment of 13c in sedimentary organic carbon may result from loss of ch4 from zooplanktonic gut communities isotopic methods for estimation of ancient co2 levels are considered and a hyperbolic form favored for the relationship between concentrations of dissolved co2 and isotopic fractionation

organic stable carbon isotopic composition reveals late quaternary vegetation changes in the dune fields of northern china abstract vegetation changes during the late quaternary in the dune fields of northern china are not well understood we investigated organic carbon stable isotopic composition of surface soils related mainly to the ratio of c3 and c4 plants across a range of arid to subhumid climates in this region isotopic composition is weakly related to both temperature and moisture multiple r2 0 53 with the highest 13c greatest c4 abundance in the warm subhumid horqin dune field in late quaternary eolian stratigraphic sections of the mu us and horqin dune fields but not in the much colder otindag dune field 13c is higher in organic carbon from paleosols than in eolian sands this contrast most evident for paleosols recording a major early to middle holocene phase of dune stabilization is interpreted as evidence for expansion of c4 plants due to increased effective moisture high temperature because of high insolation and decreased disturbance related to eolian erosion and deposition

phytolith and carbon isotope evidence for late quaternary vegetation and climate change in the southern black hills south dakota abstract analyses of phytoliths and carbon isotopes document change in late quaternary grasslands in the red valley of the southern black hills late pleistocene grassland composition was equivalent to the c3grass parklands of modern central alberta the rise of mixed grassland occurred rapidly between 11 000 and 9000 yr b p early holocene mixed grasslands included both short and tall c4grasses a mid holocene erosional unconformity ca 8000 to 4500 yr b p precludes phytolith or isotope analysis but suggests lack of vegetation and landscape denudation caused by a drier climatic basin wide stability and soil development followed the erosional episode ca 4500 to 3600 yr b p mesic adapted c4panicoid grasses increased during this period of soil development low magnitude fluctuation in the c4 dominated mixed grassland occurred throughout the late holocene 3600 yr b p to present rise in 13c values during the last 1000 yr without corresponding change in phytoliths may indicate a decrease in woodlands caused by increased fire frequency

geochemical expressions of anoxic conditions in nordasvannet a land locked fjord in western norway abstract the nordasvannet fjord in western norway is a modern semi enclosed basin suitable for studying sedimentary cycles as they occur under anoxic bottom conditions it is characterized by strongly anoxic conditions in the water column and bottom sediments diagenetic pyrite formation occurs in the sediments and syngenetic pyrite is formed in the lower water column organic matter burial in the fjord exceeds that of other environments with normal marine or upwelling conditions this is due to the better preservation of organic matter organic matter composition appears to have changed over time with higher fractions of terrigenous organic matter being present in the most recent sediments this may be a result of increased input of terrigenous organic matter possibly due to sewage supply to the fjord over the last decades organic c and caco3 contents of the sediments do not appear to reflect a productivity signal calcium carbonate content is influenced by chemogenic calcite formation biogenic opal content appears to reflect a productivity signal but different degrees of dissolution may obscure its clear recognition

terrigenous input to a fjord in central norway records the environmental response to the north atlantic oscillation over the past 50 years during the last century both earth surface temperature and moisture transport towards high latitudes have increased rapidly the response of the sub arctic region to these changes in terms of weathering transport and delivery of terrigenous material towards the coastal and deep ocean is both complex and poorly understood sediments accumulating in fjords offer an excellent opportunity for studying such land ocean interactions and may provide ultra high resolution records of environmental response to short term climate variability as a basis for holocene climate change studies modern sources supply and distribution of particular sediment components in the trondheimsfjord have been investigated and imply lithogenic elements as a promising proxy for terrigenous input and river discharge to better understand the impact of atmospheric variability on central norwegian environment we examine instrumental time series and show that the dominant mode of the atmospheric circulation in the north atlantic region the north atlantic oscillation nao has a strong impact on river discharge temperature and precipitation in central norway in addition elemental composition analysis of a short sediment core reveals that from 1959 to 2010 winter precipitation and temperature changes are recorded by changes in the inorganic geochemical composition of trondheimsfjord sediments elemental ratios of al zr and k ni in the sediment core mc99 3 show a close relation to small scale high frequency climate variations and large scale changes in the northern hemisphere climate this implies that terrigenous input and related erosional processes in the fjord hinterland are highly sensitive to atmospheric circulation variability in the north atlantic region by comparing our results with nao records derived from ice accumulation rates of norwegian glaciers western greenland ice sheets and river discharge anomalies in the eurasian arctic we show that it is possible to reconstruct the nao from sedimentary archives in central norwegian fjords

the sources and deposition of organic matter in the late quaternary pigmy basin gulf of mexico abstract the concentration and carbon isotopic composition 13c of sedimentary organic carbon corg n c ratios and terrigenous and marine 13corg endmembers form a basis from which to address problems of late quaternary glacial interglacial climatic variability in a 208 7 m hydraulic piston core dsdp 619 from the pigmy basin in the northern gulf of mexico while interpretations of sedimentary 13corg time series records are often not unique paired analyses of 13corg and n c are consistent with the hypothesis that the corg in the pigmy basin is a climatically determined mixture of c3 photosynthetic terrigenous and marine organic matter confirming the earlier 13corg model of sackett 1964 a high resolution 1 4 2 9 ka sample 13corg record shows that sedimentary organic carbon in interglacial oxygen isotope sub stages 1 and 5a b are enriched in 13c average 1 values are 24 2 1 2 o and 22 9 0 7 o relative to pdb respectively while glacial isotope stage values 2 are relatively depleted 25 6 0 5 concentrations of terrigenous and marine sedimentary organic carbon are calculated for the first time using 13corg and corg measurements and empirically determined terrigenous and marine 13corg endmembers the net accumulation rate of terrigenous organic carbon is 4 3 2 6 times higher in isotope stages 2 4 than in sub stages 1 and 5a b recording higher erosion rates of terrigenous organic material in glacial times the concentration and net accumulation rates of marine and terrigenous corg suggest that the nutrient bearing plume of the mississippi river may have advanced and retreated across the pigmy basin as sea level fell and rose in response to glacial interglacial sea level change

summer monsoon intensity controls c4 c3 plant abundance during the last 35 ka in the chinese loess plateau carbon isotope evidence from bulk organic matter and individual leaf waxes the natural abundance of c3 and c4 plants is affected by multiple environmental factors including temperature moisture balance and atmospheric pco2 the relative importance of these factors is a subject of considerable debate and may vary in different natural ecosystems previous studies generally focus on single loess sequences in the chinese loess plateau and conflicting conclusions on c4 c3 have been reached when studying carbon isotope ratios in carbonate and organic matter in this paper we report a comprehensive carbon isotopic characterization of total organic carbon toc and individual higher plant leaf waxes from five loess sequences spanning the last 35 ka from the chinese loess plateau clp the five coring sites encompass large gradients of annual mean temperature 9 2 13 9 c and precipitation 402 673 mm allowing us to assess the controlling mechanisms on c4 c3 plant ratios glacial interglacial sequences provide carbon isotope data for comparison with other climatic and environmental proxies such as lithology and magnetic susceptibility our results demonstrate that increased c4 c3 ratios are positively correlated with higher temperature and increased summer rainfall which characterize stronger summer monsoon in all five sites we conclude c4 abundance increases from the last glacial to the holocene in response to greater monsoon activity and that the c4 expression is suppressed in the cold and drier intervals

development of asian monsoon revealed by marked ecological shift during the latest miocene in northern pakistan carbon isotopes from soil carbonate1 4 and soil organic matter5 6 yield palaeoecological information because the carbon in the soil carbonate forms in isotopic equilibrium with local soil co2 refs 1 7 the isotopic composition of which is in turn determined by local plant cover siwalik group sediments in northern pakistan contain a well exposed palaeosol record spanning the past 18 myr here we report on stable carbon isotope results from associated pedogenic carbonate which indicate a dramatic ecological shift from to dominated floodplain biomass beginning 7 4 7 0 myr ago the earlier c3 floodplain biomasses were probably mainly composed of trees and shrubs whereas c4 grasslands dominated in the plio pleistocene oxygen isotopes also exhibit a shift in the latest miocene probably corresponding to a major climate change which may have induced the forest to grassland transition this dramatic ecological shift in the latest miocene may mark the inception or a marked strengthening of the asian monsoon system

holocene environmental changes in the central inner mongolia based on single aliquot quartz optical dating and multi proxy study of dune sands abstract alternating units of dune sands and paleosols in the central inner mongolia imply multiple episodes of dune building and stabilization in response to the waxing and waning of the east asian monsoon such eolian deposits were dated by using the single aliquot quartz optical dating method combined with the multi proxy study on the deposits the past environmental changes during the holocene have been reconstructed our results indicate that widespread eolian sand mobilization occurred in the studied region during the beginning of the early holocene from 11 5 ka to 9 ka the climate became warm and humid during the period between 9 ka and 5 6 ka holocene optimum after 5 6 ka the region again became arid as inferred from dune building however the environmental changes during the late holocene have been affected by both climate and human impacts and the presence of desert environment in such semiarid region is not only the result of climatic drought of the late holocene but also related to poor land use practices

re examining southern hemisphere westerly wind behavior insights from a late holocene precipitation reconstruction using new zealand fjord sediments abstract the behavior of the southern hemisphere westerly winds sww is inherently linked with climate variability understanding past sww climate feedbacks is key to predicting future climate change however we are limited by a lack of sww reconstructions particularly from the southwest pacific here we examine fjord sediments from fiordland new zealand 44 5 46 5 s to determine how the sww have fluctuated in position and strength in response to regional late holocene climate change and we compare our record to patagonia climate reconstructions in order to evaluate large scale sww behavior sww flow over the southern alps of new zealand drives orographic rainfall that is recorded within fjord sediments as changes in the relative contributions of terrestrial to marine organic matter which can be measured by bulk sediment 13 c and organic c n ratios using these proxies cores from three new zealand fjords show that precipitation decreased between 1400 1100 and 750 150 cal yr bp with short duration shifts toward drier conditions at 1900 and 900 cal yr bp precipitation increased 2100 1400 and 1100 700 cal yr bp with a short interval of wetter conditions around 400 cal yr bp these results indicate that westerly airflow over new zealand was stronger weaker during intervals of relatively warm cool climate our comparison of precipitation reconstructions from fiordland and patagonia shows dissimilarities in sww flow between regions while to date most mechanisms for changing the sww have invoked purely zonal shifts our results suggest that meridional changes in sww flow occurred in addition to zonal shifts in fiordland the meridional airflow associated with sam and or el nino like climate phenomena may be responsible for wet intervals while sam and or la nina like phenomena may promote dry conditions

geochemistry and mineralogy of the nw aegean sea surface sediments implications for river runoff and anthropogenic impact abstract surface sediments of the nw aegean sea were analyzed for clay mineral composition 94 samples organic c and carbonate content and major and minor elements 112 samples illite is the most abundant clay mineral followed by smectite chlorite and kaolinite clay minerals are preferentially deposited within the continental shelf and slope environment due to the prevailing cyclonic circulation and the formation of flocs in the rivers pro delta areas the spatial distribution of major lithogenic elements si al ti fe is substantially biased by the presence of relict sands located in the central eastern part of the thermaikos gulf continental shelf biogenic elements ca sr are noticeably pronounced on the northern flank of the north sporades islands organic c content and minor elements cu zn as and pb are enriched markedly over the thessaloniki bay and gulf suggesting substantial human impact deriving largely from untreated or partly treated domestic and industrial effluents the terrigenous component of the elements is preferentially contributed from the axios river zn and pb the aliakmon river cr co ni cu and as and to a lesser extent from the pinios river v co ni and cu a considerable part of the metals originates in ultra mafic and volcanic formations which are abundant in the rivers catchment basins carbonate content exhibits great variability with the highest values observed in biogenic sediments of the sporades basin in the latter area mn and fe oxides and hydroxides were found as coatings on calcite the coatings were enriched in cr co ni zn as mo and pb due to adsorption or ion exchange during early diagenesis the combined influence of the river systems the thessaloniki metropolis and the diverse sedimentological background generates great patchiness in the distribution of major and minor elements

stratigraphy and environmental reconstruction at the middle wisconsinan gilman canyon formation type locality buzzard s roost southwestern nebraska usa abstract the middle wisconsinan gilman canyon formation at the buzzard s roost type locality in southwestern nebraska was investigated to document the stratigraphy and to reconstruct the environmental and climate record the gilman canyon formation was subdivided into three loess units and three soils with radiocarbon ages constraining it between about 40 ka and 25 ka stable carbon isotope ratios magnetic susceptibility and carbon content were used to define and characterize soils within both the gilman canyon formation and underlying illinoian loveland loess at the height of soil development within the gilman canyon formation climate was supporting c4 dominated grassland with july temperatures equal to or exceeding those of today soil forming intervals within the loveland loess including the sangamon soil also exhibited relative increases in c4 biomass climate as recorded in the gilman canyon formation is corroborated by regional proxy data the formation accumulated during mis 3 and concurrent soil formation coincided with a summer insolation maximum

late holocene sea surface temperature and precipitation variability in northern patagonia chile jacaf fjord 44 s abstract a high resolution multi proxy study including the elemental and isotopic composition of bulk organic matter land plant derived biomarkers and alkenone based sea surface temperature sst from a marine sedimentary record obtained from the jacaf fjord in northern chilean patagonia 44 20 s provided a detailed reconstruction of continental runoff precipitation and summer sst spanning the last 1750 yr we observed two different regimes of climate variability in our record a relatively dry warm period before 900 cal yr bp lower runoff and average sst 1 c warmer than present day and a wet cold period after 750 cal yr bp higher runoff and average sst 1 c colder than present day relatively colder ssts were found during 750 600 and 450 250 cal yr bp where the latter period roughly corresponds to the interval defined for the little ice age lia similar climatic swings have been observed previously in continental and marine archives of the last two millennia from central and southern chile suggesting a strong latitudinal sensitivity to changes in the southern westerly winds the main source of precipitation in southern chile and validating the regional nature of the lia our results reveal the importance of the chilean fjord system for recording climate changes of regional and global significance

recent distribution and accumulation of organic carbon on the continental margin west off spitsbergen the study compiles the controlling factors for organic matter sedimentation patterns from a suite of organogeochemical parameters in surface sediments off spitsbergen and direct seabed observations using a remotely operated vehicle rov in addition we assess its storage rates as well as the potential of carbon sinks on the northwestern margin of the barents sea with short sediment cores from a selected fjord environment storfjord while sedimentation in the fjords is mainly controlled by river meltwater discharge and coastal erosion by sea ice glaciers resulting in high supply of terrigenous organic matter atlantic water inflow and thus enhanced marine organic matter supply characterizes the environment on the outer shelf and slope local deviations from this pattern particularly on the shelf are due to erosion and out washing of fine grained material by bottom currents spots dominated by marine productivity close to the island have been found at the outer isfjord and west off prins karls forland as well as off the kongsfjord krossfjord area and probably reflect local upwelling of nutrient rich atlantic water derived water masses accumulation rates of marine organic carbon as well as reconstructed primary productivities decreased since the middle of the last century negative correlation of the isfjord temperature record with reconstructed productivities in the storfjord could be explained by a reduced annual duration of the marginal ice zone in the area due to global warming extremely high accumulation rates of marine organic carbon between 5 4 and 17 2 g m 2 yr 1 mark the storfjord area and probably high latitude fjord environments in general as a sink for carbon dioxide

twentieth century proxy records of temperature and soil organic matter input in the drammensfjord southern norway abstract the drammensfjord in southern norway is an enclosed anoxic basin with a laminated sedimentary record the fjord is a transition area between the marine and terrestrial environments and thus its sedimentary archive contains information on both environments in order to reconstruct recent environmental changes in southern norway two sediment cores covering the last 90 years were analyzed we used the branched versus isoprenoid tetraether bit index as an indicator of terrestrial organic mater input and compared it to the stable carbon isotopic composition of total organic carbon 13 c toc the 13 c toc and bit index show opposing trends with 13 c toc indicating an increase in terrestrial input while the bit index suggests a decrease towards the present this contradiction is probably due to the different sources reflected by 13 c toc vegetation soil and anthropogenic input and the bit index only soil organic matter input in addition an increase in the recycling of respired co 2 within the fjord s water column could have depleted the 13 c toc of the marine component towards more negative values thus seemingly indicating an increase in terrestrial input whilst the bit index could have been affected by a reduction of riverine input and or an increase in archaeal biomass production the tetraether index of lipids with 86 carbons tex 86 was determined as a proxy for past water surface temperatures while some of the signal could be coming from the chemocline our results suggest that tex 86 indicates surface upper 25 m temperatures moreover tex 86 temperature patterns seem to follow variations in the historical record of averaged spring to fall oslo air temperature relatively closely suggesting the signal is produced during this period therefore tex 86 temperature records of fjord sediment cores can potentially be a useful tool in reconstructing past variations of coastal climates

climatic dependency of soil organic carbon isotopic composition along the s n transect from 34 n to 52 n in central east asia abstract we explored the relationships between surface soil 1 20 cm organic carbon isotopic signatures and associated climatic factors in central east asia in an attempt to develop transfer functions that can be used to retrieve the paleoclimatic information stored in the thick eolian paleosol sequences within the area our analysis shows that the negative correlation between the surface soil organic 13c values and the mean annual precipitation is robust r2 0 453 n 196 p

geochemistry of surface sediments from the fjords of northern chilean patagonia 44 47 s spatial variability and implications for paleoclimate reconstructions abstract the patagonian fjords have a clear potential to provide high resolution sedimentary and geochemical records of past climate and environmental change in the southern andes to improve our ability to interpret these proxy records we investigated the processes that control fjord sediment inorganic geochemistry through a geochemical mineralogical and sedimentological analysis of surface sediment samples from the fjords of northern chilean patagonia a simple terrestrial index based on measurements of salinity and fraction of terrestrial carbon was used to estimate the terrestrial input river discharge at each site our results demonstrate that under the cold climate conditions of patagonia chemical weathering is weak and the inorganic geochemical composition of the fjord sediments is primarily controlled by hydrodynamic mineralogical sorting i e the intensity of river discharge our results suggest that the distribution of fe ti and zr in surface sediments is controlled by their association with heavy and or coarse minerals whereas al is independent of hydrodynamic processes the elemental ratios fe al ti al and zr al are therefore well suited for estimating changes in the energy of terrestrial sediment supply into the fjords through time zr al is particularly sensitive in proximal environments while fe al is most useful in the outer fjords and on the continental margin in the most proximal environments however fe al is inversely related to hydrodynamic conditions caution should therefore be exercised when interpreting fe al ratios in terms of past river discharge the application of these proxies to long sediment cores from quitralco fjord and golfo elefantes validates our interpretations our results also emphasize the need to measure al based elemental ratios at high precision which can be achieved using simultaneous acquisition icp aes technology this study therefore constitutes a strong basis for the interpretation of sedimentary records from the chilean fjords

climatically driven glacial interglacial variations in c3 and c4 plant proportions on the chinese loess plateau high resolution 13c records of bulk organic matter om from three loess paleosol successions from the central chinese loess plateau document systematic fluctuations in c3 and c4 plant abundance for certain intervals during the past 620 k y measured 13c values of om in paleosols are less negative by 0 5 4 and total organic carbon toc contents are higher by up to 0 5 wt relative to corresponding values in loess deposits the 13com and toc decrease from peak values in paleosols progressively into overlying and underlying loess deposits integrated 13com toc and magnetic susceptibility rec ords indicate an increase in c4 vegetation to 50 during peak paleosol formation and a decrease in c4 vegetation to 30 during loess deposition for three of the past glacial interglacial cycles these results indicate that c4 plant abundance declined during glacials in this mid latitude region driven primarily by a shift to enhanced winter precipitation and lower temperatures and further contribute to the rapidly growing body of evidence that low p co2 during pleistocene glacials was insufficient to trigger c4 plant expansion without coincident favorable climatic conditions

high rates of organic carbon burial in fjord sediments globally fjords have been hypothesized to be hotspots of organic carbon burial a global compilation of organic carbon data and sedimentation rates shows that fjords sequester twice as much carbon as other ocean regions