amino acid and amino sugar transformation during sedimentation in lacustrine systems abstract we compared the degradation behaviour of amino sugars ass and amino acids aas during sedimentation in two lakes concentrations of individual ass and aas were measured in plankton sediment trap and sediment samples from lake zug lz eutrophic stratified permanently anoxic below 170 m and lake brienz lb oligotrophic oxic throughout the water column in the plankton samples aas comprised 37 50 of the organic carbon c org and 41 65 of the n with increasing water depth the fraction of c org and n as aas almost halved in both lakes at the sediment surface the contribution of aas to the c org pool was slightly greater but in the sediments the proportion further decreased downwards to values of 1 of the c org pool in lb and 8 in lz and 3 and 17 of the n pool respectively ass contributed to a smaller extent to the planktonic organic matter om within the water column the contribution decreased in both lakes in contrast in the sediments the contribution of ass to the c org and n pools increased slightly with depth indicating as accumulation we applied degradation indices based on ass aas and chlorins which all revealed transformation with om sedimentation however some indices were more sensitive to early degradation e g reactivity index and others to an intermediate level of degradation e g chlorin index and non protein aas despite the different trophic status and redox conditions the general pattern of degradation was similar in both lakes but was more pronounced in the sediments of the eutrophic lz

organic geochemical proxies of paleoceanographic paleolimnologic and paleoclimatic processes abstract organic matter constitutes a minor fraction of marine and freshwater sediments yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments the organic matter content of sediments is the residue of past biota the amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times general sources of the organic matter are inferred from bulk properties such as elemental compositions carbon and nitrogen stable isotope ratios rock eval pyrolysis data and organic petrography details of organic matter origins are refined by analyses of biomarker molecular compositions source changes are proxies for fluctuations in sea level oceanic surface currents and continental climates algal paleoproductivity rates are indicated by organic carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions these parameters record past availability of nutrients and therefore are proxies of surface mixing in the oceans and amount of land runoff to lakes sea surface paleotemperatures are recorded by the number of carbon carbon double bonds in lipid biomarkers produced by marine algae larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling the 13c and d values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture respectively diagenesis which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials can bias organic geochemical paleoenvironmental records the magnitude of this potential source of misinformation must always be considered and evaluated comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change

lack of enhanced preservation of organic matter in sediments under the oxygen minimum on the oman margin the impingement of oxygen minima on continental margins is widely thought to promote the accumulation of sedimentary facies enriched in well preserved organic matter it is shown here however that such a relationship does not clearly apply to the productive oman margin in the arabian sea which hosts one of the most severe oxygen minima in the oceans measurements made on the 0 1 cm depth interval from fourteen box cores collected from the outer shelf upper continental slope area off oman show that 1 1 deposited organic matter is overwhelmingly of marine origin 2 2 there is no significant correlation between the abundance of sedimentary organic carbon corg and the bottom water o2 concentration 3 3 there is no relation between the sedimentary corg n ratio and bottom water o2 4 4 there is no correlation between the hydrogen index hi of the organic matter and bottom water oxygen there are however significant correlations between the corg n ratio and the i corg cr al and zr al ratios as well as between the corg n ratio and the hydrogen index these relationships are interpreted as being the result of winnowing and attendant reworking which produce a progressive increase in the corg n ratio and a decrease in the hi and the i corg ratio as organic matter becomes progressively degraded commensurate rises in the cr al and zr al ratios result from the increased proportion of heavy minerals associated with winnowed lag deposits overall these data suggest that the bottom water oxygen concentration has little effect in governing either the distribution or the degree of preservation of organic matter on this margin thus the generally high but spatially variable corg content of the sediments on the oman margin may not reflect the occurrence of an oxygen minimum but instead be the result of a high settling flux of organic matter supported by monsoon driven upwelling and post depositional redistribution of the organic material by hydrodynamic influences

the mass balance of circum arctic glaciers and recent climate change the sum of winter accumulation and summer losses of mass from glaciers and ice sheets net surface mass balance varies with changing climate in the arctic glaciers and ice caps excluding the greenland ice sheet cover about 275 000 km2of both the widely glacierized archipelagos of the canadian norwegian and russian high arctic and the area north of about 60 n in alaska iceland and scandinavia since the 1940s surface mass balance time series of varying length have been acquired from more than 40 arctic ice caps and glaciers most arctic glaciers have experienced predominantly negative net surface mass balance over the past few decades there is no uniform recent trend in mass balance for the entire arctic although some regional trends occur examples are the increasingly negative mass balances for northern alaska due to higher summer temperatures and increasingly positive mass balances for maritime scandinavia and iceland due to increased winter precipitation the negative mass balance of most arctic glaciers may be a response to a step like warming in the early twentieth century at the termination of the cold little ice age arctic ice masses outside greenland are at present contributing about 0 13 mm yr 1to global sea level rise

processes of buildup and retreat of the greenland ice sheet sensitivity experiments were conducted to study the influence of several physical processes on the evolution of the greenland ice sheet over the last 250 000 years the experiments were carried out by means of a three dimensional thermodynamical model the mass balance is modeled by a surface energy balance model this means that variations in orbital parameters following from the astronomical milankovitch theory can be incorporated in the ablation calculations it is shown that with regard to the greenland ice sheet variations in shortwave radiation are only of minor importance for the changes in volume over time calculations of the various components of the energy balance under glacial and interglacial conditions show that the changes in absorbed shortwave radiation resulting from changes in orbital parameters are considerably smaller than the variations in the sensible heat flux caused by temperature variations thermodynamics are only of importance for the volume changes of the ice sheet if the climate is on average stable over a long period in between 110 kyr b p and 20 kyr b p the ice volume increased slowly due to the cooling of the ice which resulted in a higher effective viscosity and thus a thicker ice sheet the long response time of the thermodynamics means that the thermodynamics cannot play a crucial role during transition from a glacial to a deglacial period which occur typically within several thousands of years the mass balance height feedback has an important function in the buildup of the ice sheet after a warm period like the eemian without isostatic bedrock compensation the ablation will remain very high in some marginal parts yielding a considerably smaller ice sheet volume for the last glacial period

assessing c n and δ13c as indicators of holocene sea level and freshwater discharge changes in the subaqueous yangtze delta china to examine the applicability of c n and organic carbon stable isotope 13c in studies of the holocene sea level and freshwater discharge in the large river mouth of yangtze we observed the distribution of carbon nitrogen and 13c in a late quaternary core zk9 collected from the present subaqueous delta we also collected published data of the two proxies for the suspended particulate matter spm and surficial sediments from the lower yangtze river to the adjacent east china sea the results show that the estuarine front is an important boundary for terrestrial and marine contribution of the organic component in the modern sedimentary environment in the core zk9 sediments deposited during c 13 9 cal ka bp are characterized by high values of toc 0 54 1 16 caco3 0 35 on average and c n 12 which reflect an inner tidal estuarine environment dominated by c3 terrestrial organic carbon input during c 9 0 7 cal ka bp both toc content 0 57 on average and c n ratio 10 decrease remark

flux and fate of yangtze river sediment delivered to the east china sea numerous cores and dating show the yangtze river has accumulated about 1 16 x 10 12 t sediment in its delta plain and proximal subaqueous delta during holocene high resolution seismic profiling and coring in the southern east china sea during 2003 and 2004 cruises has revealed an elongated similar to 800 km distal subaqueous mud wedge extending from the yangtze river mouth southward off the zhejiang and fujian coasts into the taiwan strait overlying what appears to be a transgressive sand layer this distal clinoform thins offshore from similar to 40 in thickness between the 20 and 30 m water depth to 1 2 in between 60 and 90 m water depth corresponding to an across shelf distance of less than 100 km total volume of this distal mud wedge is about 4 5 x 10 11 m 3 equivalent to similar to 5 4 x 10 11 t of sediment most of the sediment in this mud wedge comes from the yangtze river with some input presumably coming from local smaller rivers thus the total yangtze derived sediments accumulated in its deltaic system and east china sea inner shelf have amounted to about 1 7 x 10 12 t preliminary analyses suggest this longshore and across shelf transported clinoform mainly formed in the past 7000 yrs after postglacial sea level reached its mid holocene highstand and after re intensification of the chinese longshore current system sedimentation accumulation apparently increased around 2000 yrs bp reflecting the evolution of the yangtze estuary and increased land erosion due to human activities such as fanning and deforestation the southward flowing china coastal current the northward flowing taiwan warm current and the kuroshio current appear to have played critical roles in transporting and trapping most of yangtze derived materials in the inner shelf and hence preventing the sediment escape into the deep ocean c 2006 elsevier b v all rights reserved

preservation of amino acids from in situ produced bacterial cell wall peptidoglycans in northeastern atlantic continental margin sediments in this study we present the results of total hydrolysable amino acids thaa and amino acid d l enantiomers in northeastern atlantic continental margin sediments there is increasing evidence that intrinsically labile amino acids are present in old marine sediments as part of a refractory network of peptide like material we used amino acid enantiomers to identify the contribution of amino acids from bacterial cell walls to thaa in organic matter ranging from relatively young to 18 000 yr old the ratio of d l amino acids increased with depth in the sediment mixed layer application of a transport racemization degradation model excludes a significant production of d amino acids by racemization and implies in situ bacterial production as the main source amino acids associated with a refractory pool of bacterial cell walls could account for approximately one third of the thaa deeper in the sediments we propose that in situ bacterial production and the primary flux of labile organic matter from the water column result in a small but highly reactive pool of amino acids in the surface mixed sediment only whereas amino acids associated with refractory cell walls persist in marine sediments

relating glacier mass balance to meteorological data using a seasonal sensitivity characteristic we propose to quantify the climate sensitivity of the mean specific balance b of a glacier by a seasonal sensitivity characteristic ssc the ssc gives the dependence of b on monthly anomalies in temperature and precipitation it is calculated from a mass balance model we show and discuss examples for franz josef glacier new zealand nigardsbreen norway hintereisferner austria peyto glacier canadian rockies abramov glacier kirghizstan and white glacier canadian arctic with regard to the climate sensitivity of b the sscs clearly show that summer temperature is the most important factor for glaciers in a dry climate for glaciers in a wetter climate spring and fall temperatures also make a significant contribution to the overall sensitivity the ssc is a 2 12 matrix multiplying it with monthly perturbations of temperature and precipitation for a particular year yields an estimate of the balance for that year we show that with this technique mass balance series can be re constructed from long meteorological records or from output of atmospheric models

sources and distribution of terrigenous organic matter delivered by the atchafalaya river to sediments in the northern gulf of mexico abstract suspended sediments ss from the atchafalaya river ar and the mississippi river and surficial sediment samples from seven shallow cross shelf transects west of the ar in the northern gulf of mexico were examined using elemental oc c n isotopic 13c 14c and terrigenous biomarker analyses the organic matter om delivered by the ar is isotopically enriched 24 5 and relatively degraded suggesting that soil derived om with a c4 signature is the predominant om source for these ss the shelf sediments display oc values that generally decrease seaward within each transect and westward parallel to the coastline a strong terrigenous c n 29 signal is observed in sediments deposited close to the mouth of the river but values along the remainder of the shelf fall within a narrow range 8 13 with no apparent offshore trends depleted stable carbon isotope 13c values typical of c3 plant debris 27 are found near the river mouth and become more enriched 22 to 21 offshore the spatial distribution of lignin in shelf sediments mirrors that of oc with high lignin yields found inshore relative to that found offshore water depth 10 m the isotopic and biomarker data indicate that at least two types of terrigenous om are deposited within the study area relatively undegraded c3 plant debris is deposited close to the mouth of the ar whereas more degraded isotopically enriched soil derived om appears to be deposited along the remainder of the shelf an important input from marine carbon is found at the stations offshore from the 10 m isobath quantification of the terrigenous component of sedimentary om is complicated by the heterogeneous composition of the terrigenous end member a three end member mixing model is therefore required to more accurately evaluate the sources of om deposited in the study area the results of the mixing calculation indicate that terrigenous om soil derived om and vascular plant debris accounts for 79 of the om deposited as inshore sediments and 66 of om deposited as offshore sediments importantly the abundance of terrigenous om is 40 higher in inshore sediments and nearly 85 higher in offshore sediments than indicated by a two end member mixing model such a result highlights the need to reevaluate the inputs and cycling of soil derived om in the coastal ocean

amino acid biogeochemistry and organic matter degradation state across the pakistan margin oxygen minimum zone to assess whether the oxygen minimum zone omz across the pakistan margin causes differences in the lability of sedimentary organic matter sediments were collected in the core of the omz in the upper and lower transition zones and below the omz sediment samples were analysed for total nitrogen tn and organic carbon oc contents mineral surface area sa and total hydrolysable amino acids thaa and enzymatically hydrolysable amino acids ehaa oc contents and organic carbon per unit of mineral surface area oc sa values were clearly elevated in the core and lower omz transition zone these sediments also contained more labile sedimentary organic matter as discerned by higher concentrations of thaa and the contribution of n in thaa to tn a protein amino acid based degradation index revealed that all sedimentary organic matter has undergone significant degradation but sediments in the upper omz transition zone and below the omz are more degraded than inside the omz changes in amino acid composition during diagenesis are attributed to a combination of factors 1 selective preservation in which amino acids in cell walls are better preserved than amino acids in cell plasma 2 formation and accumulation of bacterially derived organic matter there were relatively more living bacteria in the core of the omz and an accumulation of peptidoglycan derived amino acids in degraded sediments in the upper omz transition zone and below the omz and 3 bacterial transformation as the molar percentages of bacterial transformation products alanine bala amino butyric acid gaba and ornithine orn increased with increasing degradation

chlorin index a new parameter for organic matter freshness in sediments 1 total chlorins comprising degradation products of chlorophyll have been used recently to reconstruct paleoproductivity from marine sediment cores here we report on a new index the chlorin index ci that proves to be a helpful tool for rapidly estimating organic matter freshness in marine sediments the ci is a ratio between the fluorescence intensity of a sediment extracted with acetone and treated with hydrochloric acid and the original sediment extract it represents the ratio of chlorophyll and its degradation products deposited in the sediments that could still be chemically transformed and those that are inert to chemical attack the ratio is lower in sediments that include freshly deposited phytoplankton material and higher in older more degraded sediments we measured this new parameter on surface sediments and sediments from several short and a long sediment core from different oceanic settings ci values range from 0 2 for chlorophyll a to 0 36 0 56 for fresh material deposited on the shelf off namibia to values around 0 67 in sediments off chile and peru to values up to 0 97 for sediments in a deep core from the northeastern slope of the arabian sea we have compared the ci to rates of bacterial sulfate reduction as a direct measure of organic matter reactivity and to other degradation indices based on amino acid composition we conclude that the ci is a reliable and simple tool for the characterization of organic material freshness in sediments in respect to its degradation state

contribution of glacier melt to sea level rise since ad 1865 a regionally differentiated calculation the contribution of glacier melt including the greenland ice sheet to sea level change since ad 1865 is estimated on the basis of modelled sensitivity of glacier mass balance to climate change and historical temperature data calculations are done in a regionally differentiated manner to overcome the inhomogeneity of the global distribution of glaciers a distinction is made between changes in summer temperature and in temperature over the rest of the year our best estimate of the ice melt in the period 1865 1990 in terms of sea level change equivalent is 5 7 cm 2 7 cm for glaciers and 3 0 cm for the greenland ice sheet additional calculations show that simpler methods like using annual or even global mean temperature anomaly give estimates that differ by up to 55 consequently a regionally differentiating approach is advised for making projections of glacier melt with gcm output

sensitivity of a greenland ice sheet model to ice flow and ablation parameters consequences for the evolution through the last climatic cycle sensitivity experiments are conducted to test the influence of poorly known model parameters on the simulation of the greenland ice sheet by means of a three dimensional numerical model including the mechanical and thermal processes within the ice two types of experiments are performed steady state climatic conditions and simulations over the last climatic cycle with a climatic forcing derived from the grip record the experiments show that the maximum altitude of the ice sheet depends on the ice flow parameters deformation and sliding law coefficients geothermal flux and that it is low when the ice flow is fast on the other hand the maximum altitude is not sensitive to the ablation strength and consequently during the climatic cycle it is driven by changes in accumulation rate the ice sheet extension shows the opposite sensitivity it is barely affected by ice flow velocity and the ice covered area is smaller for large ablation coefficients for colder climates when there is no ablation the ice sheet extension depends on the sea level an interesting result is that the variations with time of the altitude at the ice divide summit do not depend on the parameters we tested the present modelled ice sheets resulting from the climatic cycle experiments are compared with the present measured ice sheet in order to find the set of parameters that gives the best fit between modelled and measured geometry it seems that compared to the parameter set most commonly used higher ablation rate coefficents must be used

organic matter reactivity indicators in sediments of the st lawrence estuary here we report multiple parameters used to describe the diagenetic state of sediments including total hydrolyzable amino acid thaa amino acid enantiomer chlorin ci and amino acid degradation di ri indices along a transect between the upper st lawrence estuary and the gulf of st lawrence canada the study area is characterized by gradients in water oxygen concentration water depth organic matter om source primary productivity and sedimentation rate both ci and di indicate a decline in om reactivity with the transition from a more terrestrial to a more marine dominated sedimentation regime as one moves from the shallow upper estuary 23 95 m to the hypoxic mid depth lower estuary and to the deep 400 m well oxygenated gulf whereas the ci more accurately reflected om reactivity in surface sediments and sediments down to 5 cm the amino acid based degradation indices di and ri better described degradation in sediments down to 35 cm systematic variations in the amino acid composition along the laurentian channel confirmed the increased diagenesis of om with distance from the upper st lawrence estuary the ratio of d l stereoisomers of alanine increased along the transect and the co variation between di and the d l ala suggest a close coupling between the extent of diagenesis and the accumulation and selective preservation of bacterially derived cell wall material in the sediments the same patterns that we observed along the estuarine transect were present down core in two sediment cores confirming the robustness of our reactivity indices oxygen exposure time of the sediments appears to strongly determine sediment om reactivity in the st lawrence estuary the sediment oxygen regime itself is related to the interplay between water column depth vertical om flux and reactivity of settling om

surface melt induced acceleration of greenland ice sheet flow ice flow at a location in the equilibrium zone of the west central greenland ice sheet accelerates above the midwinter average rate during periods of summer melting the near coincidence of the ice acceleration with the duration of surface melting followed by deceleration after the melting ceases indicates that glacial sliding is enhanced by rapid migration of surface meltwater to the ice bedrock interface interannual variations in the ice acceleration are correlated with variations in the intensity of the surface melting with larger increases accompanying higher amounts of summer melting the indicated coupling between surface melting and ice sheet flow provides a mechanism for rapid large scale dynamic responses of ice sheets to climate warming

elevation changes measured on svalbard glaciers and ice caps from airborne laser data precise airborne laser surveys were conducted during spring in 1996 and 2002 on 17 ice caps and glaciers in the svalbard archipelago covering the islands of spitsbergen and nordaustlandet we present the derived elevation changes lower elevation glaciers in south spitsbergen show the largest thinning rates of 0 5 m a 1 while some of the higher more northerly ice caps appear to be close to balance the pattern of elevation change is complex however due to several factors including glacier aspect microclimatological influences and the high natural annual variability in local accumulation and ablation rates anomalous changes were observed on fridtjovbreen which started surging in 1996 at the start of the measurement period on this glacier thinning of 0 6 m a 1 w as observed in the accumulation area coincident with thickening at lower elevations asymmetric thinning was found on two ice caps on nordaustlandet with the largest values on the eastern side of vestfonna but the western slopes of vegafonna the mean elevation change for all ice masses was 0 19 m a 1 w e which is 1 6 times the net mass balance value determined for the last 30 years using mass balance sensitivity estimates for svalbard suggests that the implied increase in negative balance is linked to warmer air temperatures in the late 1990s multiple linear regression suggests that mass balance is most closely correlated with latitude rather than mean altitude or longitude

recent sediment accumulation and carbon burial in the east china sea 1 sediment and carbon budgets were constructed for the east china sea ecs shelf based on up to date data the total annual sediment flux in the ecs shelf is approximately 96 of the terrestrial input there is high retention of sediment on the ecs shelf owing to the broad nature of the shelf edge i e 500 600 km and because of an along shore sediment dispersal path driven by the east china sea coastal current ecscc and the taiwan warm current twc organic carbon oc burial was also observed based on the results for sediment accumulation and the oc proportion in surface sediment a total of 7 4 106 t of oc is preserved in shelf sediments source discrimination of sedimentary oc revealed that the percentage of oc burial for both terrigenous and marine oc sources was higher than the global mean value at 10 and 5 5 respectively presumably owing to high sediment accumulation high oc flux to sediment in the estuary and shelf break suggests that riverine discharge and upwelling of the kuroshio intrusion are key factors regulating oc burial over the shelf estimated using a mass balance model 15 20 of the carbon inventory is buried in the shelf sediment while 80 of the carbon inventory must be transported out of shelf area in the form of dissolved carbon organic and inorganic the accumulation of carbon in sediments and the outflow of dissolved carbon sustain a high carbon sink in the ecs

on thermal expansion over the last hundred years estimates of sea level rise during the period 1856 1991 due to thermal expansion are presented the estimates are based on an ocean model that consists of three zonally averaged ocean basins representing the atlantic pacific and indian oceans these basins are connected by a circumpolar basin that represents the southern ocean the ocean circulation in the model was prescribed surface ocean forcing was calculated from observed sea surface temperatures global mean forcing and regionally varying forcing were distinguished different parameterizations of ocean heat mixing were incorporated according to the model presented global mean sea level rise caused by thermal expansion over the last hundred years ranged from 2 2 to 5 1 cm a best estimate being 3 5 cm 34 refs 5 figs

climate sensitivity of glaciers in southern norway application of an energy balance model to nigardsbreen hellstugubreen and alfotbreen three glaciers in southern norway with very different massbalance characteristics are studied with an energy balance model of the ice snow surface the model simulates the observed mass balance profiles in a satisfactory way and can thus be used with some confidence in a study of climate sensitivity calculated changes in equilibrium line altitude for a 1 k temperature increase are 110 108 and 135 in for nigardsbreen hellstugubreen and alfotbreen respectively the corresponding changes in mass balance averaged over the entire glacier area are 0 88 0 715 and 1 11 in year water equivalent runs with an ice flow model for nigardsbreen to which calculated mass balance profiles are imposed predict that the front will advance by 3 km for a 1 k cooling and will retreat by as much as 6 5 km for a 1 k warming the response to a 10 increase in precipitation would be a 2 km advance of the snout whereas a 4 km retreat is predicted for a 10 decrease this large sensitivity as compared to many other glaciers is to a large extent due to the geometry of nigardsbreen

combined use of δ14c and δ13c values to trace transportation and deposition processes of terrestrial particulate organic matter in coastal marine environments accelerator mass spectrometry was used to measure radiocarbons of riverine suspended particles and sediments from the estuary continental shelf and slope off the coast of tokachi river in japan the spatial distribution of 14c and 13c values of sedimentary organic matter was divided into those of 1 estuary 2 continental shelf and 3 continental slope for shelf sediments respective maxima can be seen for 14c value c n ratio and organic carbon content at a station near the river mouth the mean grain size of surface sediments also exhibits a similar trend the 13c values show a minimum near the river mouth the shelf composition does not appear to be a simple mixture of terrestrial and marine origin from the above data it is considered that the spatial distribution of 14c and 13c values may reflect variations in dispersion and deposition processes together with the size fractionation of riverine suspended particles the resuspension of sediments and differences in the contribution of marine organic matter

accumulation of prokaryotic remains during organic matter diagenesis in surface sediments off peru bacterial biomarkers d amino acids and muramic acid were investigated in surface sediments 0 1 cm at 22 stations in the peru margin concentrations were used to quantitatively estimate the relative importance of peptidoglycan in the preservation of prokaryotic remains during diagenesis the bacterial imprint in organic matter was also evident from low molar ratios average of 1 6 of glucosamine and galactosamine estimates of the fraction of biomarkers associated with intact peptidoglycan showed that peptidoglycan became a progressively less important component of prokaryotic remains with ongoing diagenesis whereas other prokaryotic biomolecules increased in importance the exact nature of these biomolecules remains unknown but constant ratios between individual d amino acids and amino sugars observed in this study provide novel information on their molecular composition examination of total hydrolyzable amino acids revealed systematic compositional changes with increasing water depth and age of the sediment reflecting increased diagenetic alteration of the organic matter the time scale integrated in the upper 1 cm of the sediment was ca 2 yr at the shallow sites and up to 20 yr at the deeper stations the alteration stages of organic matter ranged from coastal and ocean margin sediments at shallow water depth to organic matter as degraded as hemipelagic surface sediments at greater water depths

autostratigraphy a framework norm for genetic stratigraphy abstract autostratigraphy is the stratigraphy generated by large scale autogenic processes and needs to be heeded because of a current overreliance on allogenic controls in sequence stratigraphy key principles of autostratigraphy emerging from the theory of autoretreat and a new understanding of alluvial grade derive from the non equilibrium stratigraphic response i e the general lack of equilibrium configuration of depositional systems the non equilibrium behavior of fluvial deltas during times t of steady dynamic forcing leads to variable stratigraphic response that is the inevitable result of length d and time scaling particular to the depositional system rather than necessarily reflecting any sudden or unsteady change in the rate of allogenic forcing some abrupt breaks in the stratigraphic record are not necessarily associated with changes in allogenic conditions but can result from purely autogenic processes of the system when t is comparable to or longer than 1 the depositional system takes the non equilibrium large scale autogenic response 2 the superposition of autogenic and allogenic components of the forcing is prominently nonlinear and thus 3 sequence stratigraphic models that have been built on the assumption of equilibrium response are incorrect autostratigraphic analysis makes it possible to detect and identify complex autogenic responses and unsteady allogenic events in the stratigraphic record by quantifying a temporal change in the magnitude of d autostratigraphy thus functions as a norm for genetic stratigraphy

sources and degradation of sedimentary organic matter in the mud belt of the east china sea implications from the enantiomers of amino acids abstract total organic carbon toc total n tn and amino acids aas including the bacterial biomarker d aas were determined in sediment cores from the mud belt of the east china sea ecs the concentration of total hydrolyzable aas thaas ranged from 3 35 to 13 44 mol g dry wt dw of the sedimentary organic matter som exhibiting a decreasing trend downcore major constituents of the thaas were glycine gly l serine l ser l alanine l ala l glutamic acid l glu and l aspartic acid l asp whereas the d aspartic acid d asp d glutamic acid d glu d serine d ser and d alanine d ala along with non protein aas aminobutyric acid and alanine together accounted for ca 7 of the thaa pool given the c n ratio values the om in three cores was predominantly of marine origin based on d ala yield bacterial om represented on average 18 of toc and ca 30 of tn c normalized thaass thaa c was a sensitive indicator of som diagenetic alteration in the upper 40 cm of sediment however the degradation index di and reactivity index ri values for the cores did not exhibit any definite trend which may indicate that these two indicators were not sensitive in the early stage of sediment degradation negative correlation between the d l ratio of ala and thaa c suggested a close coupling between the extent of degradation and the accumulation and or selective preservation of bacterial material in the sediments in addition correlation between clay content and thaa c suggested that fine grained particles played an important role in affecting the quality of som

the dynamic response of the greenland and antarctic ice sheets to multiple century climatic warming new calculations were performed to investigate the combined response of the greenland and antarctic ice sheets to a range of climatic warming scenarios over the next millennium use was made of fully dynamic 3d thermomechanic ice sheet models which were coupled to a two dimensional climate model the experiments were initialized with simulations over the last two glacial cycles to estimate the present evolution and were subsequently forced with temperature scenarios resulting from greenhouse emission scenarios which assume equivalent co2 increases of two four and eight times the present 1990 a d value by the year 2130 a d and a stabilization after that the calculations brought to light that during the next century short term effect the background evolution trend would dominate the response of the antarctic ice sheet but would be negligible for the greenland ice sheet on that timescale the greenland and antarctic ice sheets would roughly balance one another for the middle scenario similar to the ipcc96 is92a scenario with respective contributions to the worldwide sea level stand on the order of about 610 cm on the longer term however both ice sheets would contribute positively to the worldwide sea level stand and the most important effect would come from melting on the greenland ice sheet sensitivity experiments highlighted the role of ice dynamics and the height massbalance feedback on the results it was found that ice dynamics cannot be neglected for the greenland ice sheet not even on a century timescale but becomes only important for antarctica on the longer term the latter is related to an increased outflow of ice into the ice shelves and to the grounding line retreat of the west antarctic ice sheet which are both found to be sensitive to basal melting below ice shelves and the effective viscosity of the ice shelves stretching parameters to their limits yielded a combined maximum rate of sea level rise of 85 cm century21 of which 60 cm would originate from the greenland ice sheet alone

sharply increased mass loss from glaciers and ice caps in the canadian arctic archipelago the canadian arctic archipelago contains one third of the global volume of land ice outside the ice sheets but its contribution to sea level change is largely unknown gardner et al use three independent techniques to reveal that mass loss from the archipelago was 92 12 gigatonnes per year in 2007 09 about three times greater than in 2004 06 and coincident with warmer summer temperatures the record is too short to allow a firm conclusion on longer term trends but it is clear that the canadian arctic archipelago is a significant contributor to sea level rise mountain glaciers and ice caps are contributing significantly to present rates of sea level rise and will continue to do so over the next century and beyond1 2 3 4 5 the canadian arctic archipelago located off the northwestern shore of greenland contains one third of the global volume of land ice outside the ice sheets6 but its contribution to sea level change remains largely unknown here we show that the canadian arctic archipelago has recently lost 61 7 gigatonnes per year gt yr 1 of ice contributing 0 17 0 02 mm yr 1 to sea level rise our estimates are of regional mass changes for the ice caps and glaciers of the canadian arctic archipelago referring to the years 2004 to 2009 and are based on three independent approaches surface mass budget modelling plus an estimate of ice discharge smb d repeat satellite laser altimetry icesat and repeat satellite gravimetry grace all three approaches show consistent and large mass loss estimates between the periods 2004 2006 and 2007 2009 the rate of mass loss sharply increased from 31 8 gt yr 1 to 92 12 gt yr 1 in direct response to warmer summer temperatures to which rates of ice loss are highly sensitive 64 14 gt yr 1 per 1 k increase the duration of the study is too short to establish a long term trend but for 2007 2009 the increase in the rate of mass loss makes the canadian arctic archipelago the single largest contributor to eustatic sea level rise outside greenland and antarctica

form and flow of the academy of sciences ice cap severnaya zemlya russian high arctic 1 the 5 575 km2 academy of sciences ice cap is the largest in the russian arctic a 100 mhz airborne radar digital landsat imagery and satellite synthetic aperture radar sar interferometry are used to investigate its form and flow including the proportion of mass lost through iceberg calving the ice cap was covered by a 10 km spaced grid of radar flight paths and the central portion was covered by a grid at 5 km intervals a total of 1 657 km of radar data digital elevation models dems of ice surface elevation ice thickness and bed elevation data sets were produced cell size 500 m the dems were used in the selection of a deep ice core drill site total ice cap volume is 2 184 km3 5 5 mm sea level equivalent the ice cap has a single dome reaching 749 m maximum ice thickness is 819 m about 200 km or 42 of the ice margin is marine about 50 of the ice cap bed is below sea level the central divide of the ice cap and several major drainage basins in the south and east of the ice cap and of up to 975 km2 are delimited from satellite imagery there is no evidence of past surge activity on the ice cap sar interferometric fringes and phase unwrapped velocities for the whole ice cap indicate slow flow in the interior and much of the margin punctuated by four fast flowing features with lateral shear zones and maximum velocity of 140 m yr 1 these ice streams extend back into the slower moving ice to within 5 10 km of the ice cap crest they have lengths of 17 37 km and widths of 4 8 km mass flux from these ice streams is 0 54 km3 yr 1 tabular icebergs up to 1 7 km long are produced total iceberg flux from the ice cap is 0 65 km3 yr 1 and probably represents 40 of the overall mass loss with the remainder coming from surface melting driving stresses are generally lowest 40 kpa close to the ice cap divides and in several of the ice streams ice stream motion is likely to include a significant basal component and may involve deformable marine sediments

sedimentation dynamics in the east china sea elucidated from and sedimentation dynamics in the east china sea was investigated based on profiles and inventories of 210 pb 137 cs and ex 239 240 pu in sediment cores collected from various settings in this marginal sea the derived sedimentation rates vary by two orders of magnitude from 2 to 0 02 cm yr y1 and generally decrease southward along the inner shelf and eastward offshore this pattern is consistent with the dispersal of yangtze river derived sediments by the current and tidal systems y2 y1 the weighted mean sedimentation rate over the shelf ca 0 3 g cm yr appears to be higher than fluvial inputs from the y2 y1 yangtze river and taiwan 0 14 g cm yr the discrepancy can be reduced by considering the effect of sediment mixing which renders sedimentation rates overestimated and the possibility of additional sediment input from the yellow river s dispersal system spatial variations of the observed nuclide inventories in sediments suggest extensive sediment redistribution boundary scavenging of 210 pb and large inputs of 137 cs and 239 240 pu from yangtze river s drainage basin

rapid wastage of alaska glaciers and their contribution to rising sea level we have used airborne laser altimetry to estimate volume changes of 67 glaciers in alaska from the mid 1950s to the mid 1990s the average rate of thickness change of these glaciers was 0 52 m year extrapolation to all glaciers in alaska yields an estimated total annual volume change of 52 15 km 3 year water equivalent equivalent to a rise in sea level sle of 0 14 0 04 mm year repeat measurements of 28 glaciers from the mid 1990s to 2000 2001 suggest an increased average rate of thinning 1 8 m year this leads to an extrapolated annual volume loss from alaska glaciers equal to 96 35 km 3 year or 0 27 0 10 mm year sle during the past decade these recent losses are nearly double the estimated annual loss from the entire greenland ice sheet during the same time period and are much higher than previously published loss estimates for alaska glaciers they form the largest glaciological contribution to rising sea level yet measured

sources and distribution of organic matter in a river dominated estuary winyah bay sc usa abstract the sources and distribution of organic matter om in surface waters and sediments from winyah bay south carolina usa were investigated using a variety of analytical techniques including elemental stable isotope and organic biomarker analyses several locations along the estuary salinity gradient were sampled during four different periods of contrasting river discharge and tidal range the dissolved organic carbon doc concentrations of surface waters ranged from 7 mg l 1 in the lower bay stations closest to the ocean to 20 mg l 1 in the river and upper bay samples there was a general linear relationship between doc concentrations and salinity in three of the four sampling periods in contrast particulate organic carbon poc concentrations were significantly lower 0 1 3 mg l 1 and showed no relationship with salinity the high molecular weight dissolved om hmw dom isolated from selected water samples collected along the bay displayed atomic carbon nitrogen ratios c n a and stable carbon isotopic compositions of organic carbon 13coc that ranged from 10 to 30 and from 28 to 25 respectively combined such compositions indicate that in most hmw dom samples the majority of the om originates from terrigenous sources with smaller contributions from riverine and estuarine phytoplankton in contrast the c n a ratios of particulate om pom samples varied significantly among the collection periods ranging from low values of 5 to high values of 20 overall the trends in c n a ratios indicated that algal sources of pom were most important during the early and late summer whereas terrigenous sources dominated in the winter and early spring in winyah bay bottom sediments the concentrations of the mineral associated om were positively correlated with sediment surface area the c n a ratios and 13coc compositions of the bulk sedimentary om ranged from 5 to 45 and from 28 to 23 respectively these compositions were consistent with predominant contributions of terrigenous sources and lesser but significant inputs of freshwater estuarine and marine phytoplankton the highest terrigenous contents were found in sediments from the river and upper bay sites with smaller contributions to the lower parts of the estuary the yields of lignin derived cuo oxidation products from winyah bay sediments indicated that the terrigenous om in these samples was composed of variable mixtures of relatively fresh vascular plant detritus and moderately altered soil om based on the lignin phenol compositions most of this material appeared to be derived from angiosperm and gymnosperm vascular plant sources similar to those found in the upland coastal forests in this region a few samples displayed lignin compositions that suggested a more significant contribution from marsh c3 grasses however there was no evidence of inputs of spartina alterniflora a c4 grass remains from the salt marshes that surround the lower sections of winyah bay

radiocarbon dating chronologic framework and changes in accumulation rates of holocene estuarine sediments from chesapeake bay abstract rapidly accumulating holocene sediments in estuaries commonly are difficult to sample and date in chesapeake bay we obtained sediment cores as much as 20 m in length and used numerous radiocarbon ages measured by accelerator mass spectrometry methods to provide the first detailed chronologies of holocene sediment accumulation in the bay carbon in these sediments is a complex mixture of materials from a variety of sources analyses of different components of the sediments show that total organic carbon ages are largely unreliable because much of the carbon including coal has been transported to the bay from upstream sources and is older than sediments in which it was deposited mollusk shells clams oysters and foraminifera appear to give reliable results although reworking and burrowing are potential problems analyses of museum specimens collected alive before atmospheric nuclear testing suggest that the standard reservoir correction for marine samples is appropriate for middle to lower chesapeake bay the biogenic carbonate radiocarbon ages are compatible with 210pb and 137cs data and pollen stratigraphy from the same sites post settlement changes in sediment transport and accumulation is an important environmental issue in many estuaries including the chesapeake our data show that large variations in sediment mass accumulation rates occur among sites at shallow water sites local factors seem to control changes in accumulation rates with time our two relatively deep water sites in the axial channel of the bay have different long term average accumulation rates but the history of sediment accumulation at these sites appears to reflect overall conditions in the bay mass accumulation rates at the two deep water sites rapidly increased by about fourfold coincident with widespread land clearance for agriculture in the chesapeake watershed

estimating the contribution of arctic glaciers to sea level change in the next 100 years in this paper we report on an approach to estimate the contribution of arctic glaciers to sea level change in our calculation we assume that a static approach is feasible we only calculate changes in the surface balance from modelled sensitivities these sensitivities summarized in the seasonal sensitivity characteristic can be used to calculate the change in the surface mass budget for given anomalies of monthly temperature and precipitation we have based our calculations on a subdivision of all arctic ice into 13 regions four sectors of the greenland ice sheet the canadian arctic 74 n the canadian arctic 60 n as forcing for the calculations we have used the output from five climate models for the period 2000 2100 these models were forced by the same greenhouse gas scenario ipcc b2 the calculated contributions to sea level rise in the year 2100 vary from almost zero to about 6 cm the differences among the models stem first of all from differences in the precipitation the largest contribution to sea level change comes from the greenland ice sheet the glaciers in alaska also make a large contribution not because of the area they cover but because they are more sensitive than other glaciers in the arctic the climate models do not agree on regional patterns the runoff from svalbard glaciers for instance increases for two models and decreases for the three other models we conclude that the uncertainty due to a simple representation of the glaciological processes is probably smaller than the uncertainty induced by the differences in the climate change scenarios produced by the models

surface area control of organic carbon accumulation in continental shelf sediments the relationship between organic carbon oc and grain size found in most continental shelf sediments is here reinterpreted in terms of the surface area of the sediments cores from many north american shelf environments show downcore decreases in oc to similar refractory background concentrations if expressed relative to the surface area of the sediments this consistent concentration is 0 86 mg oc m 2 which is equivalent in concentration to a monolayer of organic matter coating all mineral surfaces a more global collection of sediment water interface samples show that this relationship is even more extensive with exceptions occurring in areas of very high riverine sediment input organic pollution or low oxygen water columns density separations indicate that organic matter is largely adsorbed to mineral grains the microtopography of surfaces was examined with n2 sorption and most surface area was found to be inside pores of 10 nm width these data lead to a hypothesis that organic matter is protected by its location inside pores too small to allow functioning of the hydrolytic enzymes necessary for organic matter decay such protection would likely work in concert with other protection mechanisms such as humification this consistent surface area correlation with oc concentration may explain control of spatial and temporal variations in oc burial rates by sedimentation rates the pore protection hypothesis provides a causal mechanism for this observed control

the dispersal of sedimentary terrestrial organic matter in the east china sea ecs as revealed by biomarkers and hydro chemical characteristics terrestrial organic matter tom in surface sediments from the lower yangtze river and adjacent east china sea ecs shelf was characterized using elemental stable carbon isotope and molecular analysis the results show that it is heterogeneous and derives from various sources in the lower river transect rc transect and inner shelf transect zj transect but is more homogeneous and presumably derives from a single source in the cross shelf transect pn transect the trends in sedimentary tom abundance indicated by high molecular weight n alkane abundances and distributions lignin derived products 13c values of total organic carbon 13ctoc and ratio of toc to total nitrogen c n suggest a southward off estuary transport mode of tom along the inner shelf transect while counter intuitively the opposite or no trend in tom off estuary transport occur along the cross shelf transect we therefore suggest that yangtze discharged om is transported southwards along the zhejiang fujian coast zj transect and enters the southern okinawa trough via near bottom currents from where it is ultimately delivered back upslope to the middle shelf by the kuroshio invading water consistent with the hydro chemical characteristics of the ecs