archaea mediate anaerobic oxidation of methane in deep euxinic waters of the black sea we evaluate anaerobic oxidation of methane aom in the black sea water column by determining distributions of archaea specific glyceryl dialkyl glyceryl tetraethers gdgts and 13c isotopic compositions of their constituent biphytanes in suspended particulate matter spm sinking particulate matter collected in sediment traps and surface sediments we also determined isotopic compositions of fatty acids specific to sulfate reducing bacteria to test for biomarker and isotopic evidence of a syntrophic relationship between archaea and sulfate reducing bacteria in carrying out aom bicyclic and tricyclic gdgts and their constituent 13c depleted monocyclic and bicyclic biphytanes down to 67 indicative of archaea involved in aom were present in spm in the anoxic zone below 700 m depth in contrast gdgt 0 and crenarchaeol derived from planktonic crenarchaeota dominated the gdgt distributions in the oxic surface and shallow anoxic waters fatty acids indicative of sulfate reducing bacteria i e iso and anteiso c15 were not strongly isotopically depleted e g 32 to 25 although anteiso c15 was 5 more depleted in 13c than iso c15 our results suggest that either aom is carried out by archaea independent of sulfate reducing bacteria or those sulfate reducing bacteria involved in a syntrophy with methane oxidizing archaea constitute a small enough fraction of the total sulfate reducing bacterial community that an isotope depletion in their fatty acids is not readily detected sinking particulate material collected in sediment traps and the underlying sediments in the anoxic zone contained the biomarker and isotope signature of upper water column archaea aom specific gdgts and 13c depleted biphytanes characteristic of the spm in the deep anoxic zone are not incorporated into sinking particles and are not efficiently transported to the sediments this observation suggests that sediments may not always record aom in overlying euxinic water columns and helps explain the absence of aom derived biomarkers in sediments deposited during past periods of elevated levels of methane in the ocean

the 13c suess effect in scleractinian corals mirror changes in the anthropogenic co2 inventory of the surface oceans 1 new 13 c data are presented from 10 coral skeletons collected from florida and elsewhere in the caribbean dominica dominican republic puerto rico and belize these corals range from 96 to 200 years in age and were collected between 1976 and 2002 the change in the 13 c of the skeletons from these corals between 1900 and 1990 has been compared with 27 other published coral records from the atlantic pacific and indian oceans the new data presented here make possible for the first time a global comparison of rates of change in the 13 c value of coral skeletons of these records 64 show a statistically significant p 0 05 decrease in 13 c towards the modem day 23 out of 37 this decrease is attributable to the addition of anthropogenically derived co 2 13 c suess effect to the atmosphere between 1900 and 1990 the average rate of change of the 13 c in all the coral skeletons living under open oceanic conditions is approximately 0 01 o yr 1 in the atlantic ocean the magnitude of the decrease since 1960 0 019 yr 1 0 015 is essentially the same as the decrease in the 13 c of atmospheric co 2 and the 13 c of the oceanic dissolved inorganic carbon 0 023 to 0 029 yr 1 while in the pacific and indian oceans the rate is more variable and significantly reduced 0 007 yr 1 0 013 these data strongly support the notion that i the 13 c of the atmosphere controls ambient 13 c of the dissolved inorganic carbon which in turn is reflected in the coral skeletons ii the rate of decline in the coral skeletons is higher in oceans with a greater anthropogenic co 2 inventory in the surface oceans iii the rate of 13 c decline is accelerating superimposed on these secular variations are controls on the 13 c in the skeleton governed by growth rate insolation and local water masses

global cooling during the eocene oligocene climate transition about 34 million years ago earth s climate shifted from a relatively ice free world to one with glacial conditions on antarctica characterized by substantial ice sheets how earth s temperature changed during this climate transition remains poorly understood and evidence for northern hemisphere polar ice is controversial here we report proxy records of sea surface temperatures from multiple ocean localities and show that the high latitude temperature decrease was substantial and heterogeneous high latitude 45 degrees to 70 degrees in both hemispheres temperatures before the climate transition were 20 c and cooled an average of 5 c our results combined with ocean and ice sheet model simulations and benthic oxygen isotope records indicate that northern hemisphere glaciation was not required to accommodate the magnitude of continental ice growth during this time

chemical composition of the snowpack during the oasis spring campaign 2009 at barrow alaska 1 the chemical composition of the seasonal snowpack was determined close to barrow an arctic coastal location in northern alaska one hundred and twelve samples of different snow types including fresh snow surface hoar diamond dust blowing snow rounded snow grains and depth hoar were collected and analyzed for major sea salt components bromide and nitrate sodium chloride sulfate and potassium are mainly introduced into the snowpack by the deposition of sea salt while magnesium and calcium result from a combination of sea salt and dust sulfate was strongly depleted in most samples compared to other sea salt components this is attributed to the precipitation of mirabilite in newly formed sea ice and frost flowers that leads to an efficient fractionation of sulfate uptake of volatile but soluble species from the gas phase also contributed to the observed chloride sulfate and nitrate in the snow however for chloride and sulfate the input from the marine sources was overwhelming and the uptake from the gas phase was only visible in the samples with low concentrations like fresh snow diamond dust and surface hoar nitrate concentrations in the snowpack were less variable and for aged snow nitrate was related to the specific surface area of the snow indicating the adsorption of nitric acid can be an important nitrate source in the aged snow bromide was also introduced into the snowpack from marine sources but due to its high reactivity it was partly transferred back to the atmosphere in the form of reactive species the result of these processes was evident in bromide concentrations which were both enriched and depleted at the snowpack surface while deeper layers were mostly depleted blowing snow also exhibited a depleted bromide composition for all compounds except nitrate many depth hoar samples exhibited the greatest concentrations probably as a result of higher input earlier in the season as well as increases due to the sublimation of water during the metamorphism of the snow

regionally metamorphosed calc silicate hosted deposits of the brooks range northern alaska three distinctly different calc silicate ore suites in the brooks range northern alaska show contrasting geologic and metallogenic associations both host rocks and plutonic rocks are of devonian age and all lithologies were subjected to a major late jurassic early cretaceous regional metamorphic event one calc silicate suite is associated with peraluminous high initial 8 sr 86sr presumably s type granites and is characterized by anomalous sn contents stanniferous grandite and subcalcic garnets with crosscutting amphibole clinozoisite and a distinctive boron rich mineral association these skarns resemble the sn bearing skams of the seward peninsula except that they have low cassiterite contents and show only limited greisen alteration the noneconomic nature of the brooks range sn skarns may be related to relatively deep levels of exposure the second calc silicate suite is associated with generally metaluminous presumably type quartz sericite pyrite altered granite and granodiorite stocks and isolated fault slivers this suite contains high cu and ag variable pb and zn and low sn is characterized by andraditic garnet diopsidic pyroxene and bomite chalcopyrite cut by epidote actinolite and pyrite veinlets and generally resembles a continental margin porphyry copper related skarn the third calc silicate suite the so called gnurgle gneiss represents a regionally metamorphosed metalliferous chamical sediment and is not related to igneous metasomatic processes this suite is characterized by welldeveloped mineral foliation generally low metal contents lack of sulfide veining and retrograde alteration and combination of metal ratios and calc silicate mineral compositions not commonly observed in skarn deposits

origin and distribution of terrestrial organic matter in the nw mediterranean gulf of lions exploring the newly developed bit index the branched and isoprenoid tetraether bit index is based on the relative abundance of nonisoprenoidal glycerol dialkyl glycerol tetraethers gdgts derived from organisms living in terrestrial environments versus a structurally related isoprenoid gdgt crenarchaeol produced by marine crenarchaeota the bit index varies between 0 and 1 representing marine and terrestrial organic matter om end members respectively hopmans et al earth planet sci lett 224 107 116 2004 in this study the applicability of the bit index to trace terrestrial om is tested in combination with other organic parameters toc c n ratio 13corg total lipid and n alkane in the gulf of lions a river dominated continental margin of the western mediterranean we analyzed a variety of soils and riverbed sediments from the continent as well as surface sediments from the shelf and canyons the bit index in soils and riverbed sediments shows high values 0 9 while it varies between 0 02 and 0 83 in marine sediments decreasing seaward from the inner shelf to the slope for marine surface sediments high bit values are associated with lower 13corg values as well as higher toc contents and higher n alkane concentrations our results confirm that the bit index can be applied in coastal marine environments in order to characterize terrestrial om as proposed by hopmans et al 2004 therefore the bit index is a useful addition to the proxies presently available for studying the origin and distribution of om in continental margins and especially valuable in multiproxy studies

a novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids we propose a novel tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high performance liquid chromatography mass spectrometry hplc ms analysis of terrestrial soil and peats shows that branched tetraether lipids are predominant in terrestrial environments in contrast to crenarchaeol the characteristic membrane lipid of non thermophilic crenarchaeota which is especially abundant in the marine and lacustrine environment based on these findings an index was developed the so called branched and isoprenoid tetraether bit index based on the relative abundance of terrestrially derived tetraether lipids versus crenarchaeol this bit index was applied to surface sediments from the angola basin where it was shown to trace the outflow of the congo river furthermore analyses of particulate organic matter from the north sea showed relatively higher bit indices in water column particulate organic matter near large river inputs a survey of globally distributed marine and lacustrine surface sediments shows that the bit index in these environments correlates with the relative fluvial input of terrestrial organic material making this index generally applicable the new proxy allows the rapid assessment of the fluvial input of terrestrial organic material in immature sediments up to 100 ma old

organic carbon deposition on the north carolina continental slope off cape hatteras usa abstract the continental slope off cape hatteras nc is a region of high sediment accumulation and organic matter deposition sediment accumulation rates range from 3 to 151 cm kyr 1 organic carbon deposition rates are 5 13 moles c m 2 yr 1 the highest reported for the slope off the eastern us burial efficiencies are 3 40 the organic matter deposited is marine in origin and a mix of old and young particles high organic carbon deposition rates support remineralization throughout the upper 2 3 m of sediment deep bioirrigation to depths of 60 100 cm within the seabed affects the biogeochemistry of the sediments by extending the zone of sulfate reduction and by steepening dic porewater gradients through the non local exchange of porewater stable and radiocarbon isotope mixing curves for porewater dissolved inorganic carbon dic indicate that the dominant source of dic accumulating in the upper 2 3 m of the seabed is of nearly uniform 13c 21 10 and 14c 546

fluxes and distribution of tetraether lipids in an equatorial african lake constraints on the application of the tex86 palaeothermometer and bit index in lacustrine settings abstract the distribution of isoprenoid and branched glycerol dialkyl glycerol tetraether gdgt lipids was studied in material from various sources in and around lake challa a crater lake on the southeastern slope of mt kilimanjaro tanzania to examine the provenance of gdgts in lake sediments and their potential application as palaeoenvironmental and palaeoclimatic proxies the study material included samples collected at monthly intervals in a sediment trap over one complete annual cycle particles suspended in the stratified water column profundal surface sediments and soils surrounding the lake the sediment trap time series revealed that crenarchaeol and related isoprenoid gdgts were predominantly produced in january and february following the locally prominent short rain season november december the tex 86 inferred temperature derived from sedimenting particles corresponded well with lake surface water temperature at this time of largest crenarchaeol flux molecular ecological analysis showed that group 1 1a and 1 1b crenarchaeota are the most likely source organisms of these gdgts gdgt 0 in the lake sediments does not only originate from lake surface dwelling crenarchaeota but seems predominantly derived from archaea residing in the deeper anoxic part of the water column the main flux of branched gdgts to the sediment was during the short rain season and is most probably derived from eroded catchment soils in surface run off however a contribution from in situ production of branched gdgts in the lake sediment or water or in groundwater cannot be fully excluded we conclude that palaeoclimatic reconstruction based on branched gdgt distributions in lake sediments should only be performed when the origin of those branched gdgts is well constrained

variations in gdgt distributions through the water column in the south east atlantic ocean abstract the tetraether index of 86 carbon atoms tex 86 temperature proxy is widely used in reconstructions of past sea surface temperature most current calibrations are based on surface sediment distributions of the glycerol dialkyl glycerol tetraether lipids gdgts that comprise tex 86 and assume that these gdgts are exported from the upper mixed layer however gdgt export from deeper waters could impact sedimentary gdgt distributions and therefore tex 86 paleothermometry here we examine gdgt distributions in suspended particulate matter spm and underlying sediments collected from the southeast atlantic ocean our results reveal different gdgt distributions specifically the ratio between gdgts bearing 2 vs 3 cyclopentyl moieties 2 3 ratios between surface subsurface 50 200 m and deep water 200 m spm which suggests the occurrence of in situ deep production that is not apparent when considering tex 86 the gdgt distributions in sediments match those of subsurface waters rather than surface waters suggesting that they have not been preferentially derived from the upper mixed layer this is consistent with gdgt abundances being highest in shallow subsurface spm 100 to 200 m it remains unclear what governs the different 2 3 ratios throughout the water column but it is likely related to a combination of temperature and thaumarchaeotal community structure

reply to comment on how fast is rupture during an earthquake new insights from the 1999 turkey earthquakes 1 in a previous paper bouchon et al 2001 we presented what we believe are strong indications of supershear rupture over parts of the faults of the 1999 turkey earthquakes these findings are based on near fault recordings and modeling of the ground motion we also showed that the supershear value inferred for the izmit earthquake the only event for which this velocity is well resolved is close to ffiffiffi

sources and transport of terrestrial organic matter in vancouver island fjords and the vancouver washington margin a multiproxy approach using d13corg lignin phenols and the ether lipid bit index the branched and isoprenoid tetraether bit index a ratio of marine and terrestrial glycerol dialkyl glycerol tetraether gdgt membrane lipids was recently introduced as a proxy for the fraction of fluvially derived organic carbon oc buried in marine sediments we investigate the source and distribution of terrestrial oc in marine sediments in a large spatial data set that encompasses the washington vancouver island margin vancouver island fjords and puget sound with the goal of comparing the bit index to other traditional measures of terrestrial oc d13 co f oc d13corg and lignin phenols d13corg values and lignin concentrations indicate that the fjords are a significant trap for undegraded wood derived terrestrial material with surface sediments containing up to 76 terrestrial oc these proxies also show significant terrestrial oc contributions to margin sediments up to 54 with most likely an angiosperm source from the columbia river in contrast to d13corg values and lignin concentrations bit index values indicate extremely low terrestrial carbon throughout the study area bit index values range from 0 to 0 28 and are uncorrelated with the other proxies though the bit index did not correlate with other proxies margin gdgt concentrations varied offshore similarly to other terrestrially derived oc and are well correlated with other proxies we suggest that the bit index is best interpreted as a proxy for soil or peat derived oc the majority of terrestrially derived oc delivered to sediment in this area has a lignin rich nonsoil source the disparity between the bit index and other proxies implies that the bit index significantly underestimates terrestrial relative to marine oc input to sediments in areas in which riverine oc input is not soil or peat derived burial of organic carbon oc on continental margins is estimated to account for the majority of the total carbon burial in the ocean and is a significant sink for terrestrial oc hedges and keil 1995 understanding the sources and fate of this terrestrial oc in marine sediments is thus of importance in understanding global biogeochemical cycles in this study we use two traditional proxies for terrestrial oc input to sediments the d 13 c of bulk sedimentary oc d13corg and the concentration of lignin phenols to examine the sources and quantity of terrestrial oc in sediments throughout the washington vancouver island margin vancouver island fjords and puget sound we compare these results to those obtained using a recently introduced proxy for terrestrial oc in marine sediments the branched and isoprenoid tetraether bit index

stable carbon isotope ratios of intact gdgts indicate heterogeneous sources to marine sediments thaumarchaeota the major sources of marine glycerol dibiphytanyl glycerol tetraether lipids gdgts are believed to fix the majority of their carbon directly from dissolved inorganic carbon dic the 13c values of gdgts 13cgdgt may be powerful tools for reconstructing variations in the ocean carbon cycle including paleoproductivity and water mass circulation if they can be related to values of 13cdic to date isotope measurements primarily are made on the c40 biphytane skeletons of gdgts rather than on complete tetraether structures this approach erases information revealed by the isotopic heterogeneity of gdgts within a sample and may impart an isotopic fractionation associated with the ether cleavage to circumvent these issues we present 13c values for gdgts from twelve recent sediments representing ten continental margin locations samples are purified by orthogonal dimensions of hplc followed by measurement of 13c values by spooling wire microcombustion swim isotope ratio mass spectrometry irms with 1 precision and accuracy of 0 25 using this approach we confirm that gdgts generally around 19 are isotopically heavy compared to other marine lipids however measured 13cgdgt values are inconsistent with predicted values based on the 13c content of dic in the overlying water column and the previously published biosynthetic isotope fractionation for a pure culture of an autotrophic marine thaumarchaeon in some sediments the isotopic composition of individual gdgts differs indicating multiple source inputs the data appear to confirm that crenarchaeol primarily is a biomarker for thaumarchaeota but its 13c values still cannot be explained solely by autotrophic carbon fixation overall the complexity of the results suggests that both organic carbon assimilation ca 25 of total carbon and multiple source s of exogenous gdgts contributing generally 30 of input to sediments are necessary to explain the observed 13cgdgt values the results suggest caution when interpreting the total inputs of gdgts to sedimentary records biogenic or open slope sediments rather than clastic basinal or shallow shelf sediments are preferred locations for generating minimally biased gdgt proxy records

early paleogene temperature history of the southwest pacific ocean reconciling proxies and models we present a new multiproxy tex86 18o and mg ca marine temperature history for canterbury basin eastern new zealand that extends from middle paleocene to middle eocene including the paleocene eocene thermal maximum petm and early eocene climatic optimum eeco in light of concerns that proxy based sea surface temperature sst estimates are untenably warm for the southwest pacific during the eocene we review the assumptions that underlie the proxies and develop a preliminary paleo calibration for tex86 that is based on four multiproxy eocene records that represent an sst range of 15 34 c for the southwest pacific paleogene we show that tex86l exhibits the best fit with the eocene paleo calibration ssts derived from related proxies tex86h 1 tex86 exhibit a systematic warm bias that increases as tex86 values decrease a warm bias of 4 7 c where tex86 0 7 the tex86l proxy indicates that southwest pacific sst increased by 10 c from middle paleocene to early eocene with sst maxima of 26 28 c tropical during the petm and eeco and an sst minimum of 13 16 c cool warm temperate at the middle late paleocene transition 58 7 ma the base of the eeco is poorly defined in these records but the top is well defined in canterbury basin by a 2 5 c decrease in sst and bottom water temperature bwt in the latest early eocene 49 3 ma bwt falls from a maximum of 18 20 c in the eeco to 12 14 c in the middle eocene overall cooler temperatures are recorded in the mid waipara section which may reflect a deeper 500 m water depth and less neritic depositional setting compared with hampden and odp 1172 200 m water depth the high ssts and bwts inferred for the petm and eeco can be reconciled with eocene coupled climate model results if the proxies are biased towards seasonal maxima and the likely effect of a proto east australian current is taken into account

pre and post industrial environmental changes as revealed by the biogeochemical sedimentary record of drammensfjord norway the biogeochemical sedimentary record of the anoxic drammensfjord norway was investigated on a decadal to centennial time scale over the last millennium in order to reconstruct the pre industrial fjord environment and ecosystem and human induced environmental changes the sediments were dated by a combination of 14c and 210pb analysis and varve counting analysis of the bulk sedimentary parameters and of the biomarker distribution revealed that the sedimentary organic matter of the fjord is primarily of terrigenous origin indicating that the fjord was oligotrophic or mesotrophic the fjord s bottom water has been continuously euxinic since at least 1000 ad but photic zone euxinia occurred only irregularly in the fjord the organic matter flux and composition remained virtually invariable until the 18th century after that time the flux of material derived from coniferous trees started to increase indicated by elevated concentrations of dehydroabietic acid and related compounds but also by raising levels of c24 n alcohols and fatty acids this marked the onset of sawmill activities in the hinterland after the beginning of the industrial revolution around 1850 the flux of organic waste from sawmills and paper mills increased substantially it is suggested that slow bacterial degradation of this relatively nutrient poor organic waste caused a gradual eutrophication trend which is reflected in substantial increased bacterial and moderately increased other aquatic biomarker accumulation rates after the industrial revolution this trend accelerated and was possibly enhanced by a growing population of the area with accompanying agricultural and domestic waste this promoted primary productivity and changed the phytoplankton composition in the fjord

diploptene an indicator of terrigenous organic carbon in washington coastal sediments the pentacyclic triterpene 17 beta h 21 beta h hop 22 29 ene diploptene occurs in sediments throughout the columbia river drainage basin and off the southern coast of washington state in concentrations comparable to long chain plantwax n alkanes the same relationship is evident for diploptene and long chain n alkanes in soils from the willamette valley microorganisms indigenous to soils and soil erosion are indicated as the biological source and physical process respectively for diploptene in coastal sediments similarity between the stable carbon isotopic composition delta 13cpdb of diploptene isolated from soil in the willamette valley 31 2 0 3 and from sediments deposited throughout the washington coastal environment 31 2 0 5 supports this argument values of delta for diploptene in river sediments are variable and 8 17 lighter indicating that an additional biological source such as methane oxidizing bacteria makes a significant contribution to the diploptene record in river sediments selective biodegradation resulting from a difference in the physicochemical association within eroded particles can explain the absence of the more 13c depleted form of diploptene in washington coastal sediments but this mechanism remains unproven

high temperatures in the late cretaceous arctic ocean to understand the climate dynamics of the warm equable greenhouse world of the late cretaceous period it is important to determine polar palaeotemperatures the early palaeoceanographic history of the arctic ocean has however remained largely unknown because the sea floor and underlying deposits are usually inaccessible beneath a cover of floating ice a shallow piston core taken from a drifting ice island in 1970 fortuitously retrieved unconsolidated upper cretaceous organic rich sediment from alpha ridge a submarine elevated feature of probable oceanic origin a lack of carbonate in the sediments from this core has prevented the use of traditional oxygen isotope palaeothermometry here we determine arctic palaeotemperatures from these upper cretaceous deposits using tex86 a new palaeothermometer that is based on the composition of membrane lipids derived from a ubiquitous component of marine plankton crenarchaeota from these analyses we infer an average sea surface temperature of approximately 15 degrees c for the arctic ocean about 70 million years ago this calibration point implies an equator to pole gradient in sea surface temperatures of approximately 15 degrees c during this interval and by extrapolation we suggest that polar waters were generally warmer than 20 degrees c during the middle cretaceous approximately 90 million years ago

the origin of n alkanes in santa monica basin surface sediment a model based on compound specific δ14c and δ13c data 14c and 13c values were measured for individual long chain n alkanes c24 33 from santa monica basin sediments the data were then simulated using a three component mixing model designed to represent the contributions of different sources the three selected end members were petroleum modern plant wax and shale derived alkanes the model was optimized to fit the data and to determine the fractional contribution of each component the results indicated that petroleum accounted for 12 of the alkanes in 0 2 5 cm sediment and 5 in 2 5 7 5 cm sediment modern plant waxes contributed 80 0 2 5 cm and 87 2 5 7 5 cm and the remaining 8 of each sample was attributed to the shale source the 14c concentration of the modern terrestrial end member was also determined from the model 14c values of 235 for the 0 2 5 cm post bomb horizon and 0 for the 2 5 7 5 cm pre bomb horizon indicate that plant leaf waxes have a continental residence time of decades in the southern california region

sources and transport pathways of marine aerosol species into west antarctica sixteen high resolution marine aerosol na so4 records from spatially distributed international trans antarctic scientific expedition itase ice cores spanning the last 200 years from the pine island thwaites and ross drainage systems and the south pole are used to examine sources sea spray and frost flowers and transport pathways of marine aerosols into west antarctica factors contributing to the amount of marine aerosols transported inland include sea ice extent the presence of open water features polynyas leads wind strength and direction and the strength and positioning of low pressure systems analysis of so4 na ratios indicates that frost flowers can contribute significantly 40 to the na budget of antarctic ice cores higher na concentrations in the ross drainage system may result from greater production of marine aerosols related to frost flowers in the ross sea region in association with greater sea ice extent and larger open water areas significant positive correlations of sea ice extent and the na time series exist in some regions of west antarctica higher wind speeds in winter and higher na concentrations when slp is

recognition of paleobiochemicals by a combined molecular sulfur and isotope geochemical approach study of organic matter in immature sediments from a messinian evaporitic basin shows that consideration of structures modes of occurrence and carbon isotopic compositions of free and sulfur bound carbon skeletons allow identification of biochemical precursors detailed information concerning biotic communities present during deposition of sediments can be retrieved in this way moreover unprecedented biochemicals were recognized these extend the horizon of biomarker geochemistry

distribution of intact and core tetraether lipids in water column profiles of suspended particulate matter off cape blanc nw africa in the reconstruction of sea surface temperature sst from sedimentary archives secondary sources lateral transport and selective preservation are considered to be mainly negligible in terms of influencing the primary signal this is also true for the archaeal glycerol dialkyl glycerol tetraethers gdgts that form the basis for the tex86 sst proxy our samples represent four years variability on a transect off cape blanc nw africa we studied the subsurface production vertical and lateral transport of intact polar lipids and core gdgts in the water column at high vertical resolution on the basis of suspended particulate matter spm samples from the photic zone the subsurface oxygen minimum zone omz nepheloid layers nl and the water column between these furthermore we compared the water column spm gdgt composition with that in underlying surface sediments this is the first study that reports tex86 values from the precursor intact polar lipids ipls associated with specific head groups ipl specific tex86 we show a clear deviation from the sea surface gdgt composition in the omz between 300 and 600 m since neither lateral transport nor selective degradation provides a satisfactory explanation for the observed tex derived temperature profiles with a bias towards higher temperatures for both core and ipl specific tex86 values we suggest that subsurface in situ production of archaea with a distinct relationship between lipid biosynthesis and temperature is the responsible mechanism however in the nw african upwelling system the gdgt contribution of the omz to the surface sediments does not seem to affect the sedimentary tex86 as it shows no bias and still reflects the signal of the surface waters between 0 and 60 m

massive expansion of marine archaea during a mid cretaceous oceanic anoxic event biogeochemical and stable carbon isotopic analysis of black shale sequences deposited during an albian oceanic anoxic event 112 million years ago indicate that up to 80 weight percent of sedimentary organic carbon is derived from marine nonthermophilic archaea the carbon 13 content of archaeal molecular fossils indicates that these archaea were living chemoautotrophically their massive expansion may have been a response to the strong stratification of the ocean during this anoxic event indeed the sedimentary record of archaeal membrane lipids suggests that this anoxic event marks a time in earth history at which certain hyperthermophilic archaea adapted to low temperature environments

stable isotope proxy records in tropical terrestrial environments abstract the tropics refers to an area that is loosely equatorial characterized by relatively high temperatures at low altitude comparatively low seasonal contrast in temperatures and generally high or highly seasonal rainfall the stable isotopes of carbon oxygen and hydrogen are increasingly important tools of relevance to understanding trajectories and mechanisms of past environmental change in the tropics in the case of carbon this is because at the broadest level the carbon isotope composition of organic and carbon containing inorganic proxy materials formed in the tropics can be read as being derived from the balance between c3 tree and c4 grass photosynthesis hence providing a relative measure of vegetation type and indirectly climate likewise changes in the oxygen and hydrogen isotope composition of many proxy materials again at the broadest level can be read as indicative of changes in hydrological conditions and or altitude in the past this review provides an entry point into the literature relating to the use of stable isotopes as terrestrial environmental proxies for past environmental change with a focus on the measurement and interpretation of stable isotope data from the wide range of proxy materials preserved in tropical environments

origins of archaeal tetraether lipids in sediments insights from radiocarbon analysis abstract understanding the supply and preservation of glycerol dibiphytanyl glycerol tetraethers gdgts in marine sediments helps inform their use in paleoceanography compound specific radiocarbon measurements of sedimentary alkenones from multiple environments have been used to gain insight into processes that affect u 37 k paleotemperature reconstructions similar analyses are warranted to investigate how analogous processes affecting gdgts impact tex 86 paleotemperatures here we present radiocarbon measurements on individual gdgts from bermuda rise and santa monica basin sediments and discuss the results in the context of previous studies of co depositional alkenones and foraminifera the 14 c contents of gdgts and planktonic foraminifera in bermuda rise are very similar suggesting a local source and tex 86 derived temperatures agree more closely with foraminiferal temperatures than do u 37 k temperatures in contrast gdgts in santa monica basin are depleted in 14 c relative to both alkenones and foraminifera and tex 86 temperatures agree poorly with known surface water values we propose three possible factors that could explain these results i gdgts may be labile relative to alkenones during advective transport through oxic waters ii archaeal production deep in the water column may contribute 14 c depleted gdgts to sediments and iii some gdgts also may derive from sedimentary archaeal communities each of these three processes is likely to occur with varying relative importance depending on geographic location the latter two may help to explain why tex 86 temperature reconstructions from santa monica basin do not appear to reflect actual sea surface temperatures terrigenous gdgts are unlikely to be major contributors to bermuda rise or santa monica basin sediments based on values of the bit index the results also indicate that the crenarchaeol regioisomer is governed by processes different from other gdgts individual measurements of the crenarchaeol regioisomer are significantly depleted in 14 c relative to co occurring gdgts indicating an alternative origin for this compound that presently remains unknown re examination of the contribution of crenarchaeol regioisomer to the tex 86 index shows that it is a significant influence on the sensitivity of temperature reconstructions

terrestrial organic carbon contributions to sediments on the washington margin elemental and stable carbon isotopic compositions and biomarker concentrations were determined in sediments from the columbia river basin and the washington margin in order to evaluate geochemical approaches for quantifying terrestrial organic matter in marine sediments the biomarkers include an homologous series of long chain n alkanes derived from the surface waxes of higher plants phenolic and hydroxyalkanoic compounds produced by cuo oxidation of two major vascular plant biopolymers lignin and cutin all marine sediments including samples collected from the most remote sites in cascadia basin showed organic geochemical evidence for the presence of terrestrial organic carbon using endmember values for the various biomarkers determined empirically by two independent means we estimate that the terrestrial contribution to the washington margin is 60 for shelf sediments 30 for slope sediments and decreases further to 15 in basin sediments results from the same geochemical measurements made with depth in gravity core 6705 7 from cascadia seachannel suggest that our approach to assess terrestrial organic carbon contributions to contemporary deposits on the washington margin can be applied to the study of sediments depositing in this region since the last glacial period

sea salt aerosol production and bromine release role of snow on sea ice 1 snow lying on sea ice could be a potentially important source of sea salt aerosol as small snow particles rich in salts can be easily lifted into the air though blowing snow events using a measured distribution of snow salinity on antarctic sea ice and a blowing snow sublimation parameterization we derive a method for estimating sea salt aerosol production and bromine release during blowing snow events compared with sea salt aerosol production rates from the open ocean we find that the aerosol production rate from snow can be more than an order of magnitude larger per unit area under typical weather conditions the large sea ice cover may thus enhance the supply of sea salt to the polar lower atmosphere this is consistent with observations of sea salt aerosol seasonality and with the ice core record this large emission of sea salt from snow also implies an additional tropospheric bromine source in these regions

field observations on spatial variability of surface hoar at the basin scale inclination and wind exposure within an area of about 3 km 2 four automatic weather stations were located within the study area one on level terrain and three across a ridge despite the good instrumentation the correlation between surface hoar growth and calculated sublimation rate was poor distinct spatial patterns of surface hoar growth were found surface hoar crystals were frequently larger at the ridge site than in the surroundings of the automatic weather station on level terrain the variation in surface hoar formation was mainly due to different prevailing wind regimes during the formation periods the surroundings of the automatic weather station on level terrain were under the influence of local katabatic winds that dried up the air so that growth conditions were locally less favorable our observations suggest that predicting surface hoar formation for complex alpine terrain on the basis of data from an automatic weather station the standard procedure in avalanche forecasting seems nearly impossible unless at least the local wind regime is known at high resolution 10 m for both surface hoar formation and surface hoar destruction observations suggest wind conditions to be most crucial for spatial variation

archaeal lipids in neogene dolomites monterey and sisquoc formations california planktic versus benthic archaeal sources abstract the distribution of archaeal lipids including archaeol and glycerol dibiphytanyl glycerol tetraethers gdgts in dolomite concretions and surrounding sediment from the monterey formation miocene and the sisquoc formation miocene pliocene were examined to distinguish planktic from benthic contributions for this purpose dolomites with positive 13 c values 7 to 13 were chosen such highly positive values point to pronounced methanogenesis of benthic archaea in the sedimentary column at first glance distributions and relative abundances of gdgts in both dolomites and background sediment were similar resembling patterns of marine planktic crenarchaea a contribution of benthic euryarchaea to the gdgt pool became evident only from variations in the 13 c values of different biphytanes obtained after ether cleavage of gdgts whereas bi and tricyclic biphytanes had an isotopic signal typical of planktic archaea 13 c 23 6 to 20 5 and 23 4 to 21 2 respectively for both dolomite and background sediment acyclic and monocyclic biphytanes showed lower values for dolomite samples 25 1 to 22 6 and 27 6 to 24 7 respectively indicating a contribution of lipids from benthic archaea the isoprenoid diether archaeol 13 c 23 9 to 22 9 assigned to euryarchaea was only detected in dolomite samples also reflecting additional input from sedimentary archaea probably autotrophic methanogens the occurrence of lipids derived from methanogenic archaea agrees with the strong 13 c enrichment of dolomites and with mineral formation taking place in the zone of archaeal methanogenesis this implies that the lipid biomarker inventory of sedimentary strata needs to be interpreted carefully as it is often not straightforward to discriminate between input from the water column and sedimentary microbial activity

abundance and structural diversity of bacteriohopanepolyols in suspended particulate matter along a river to ocean transect abstract the concentration and structural diversity of a suite of bacteriohopanepolyols bhps was measured in suspended particulate matter spm from six stations along a river ocean transect off the pacific coast of panama riverine spm contained bhps diagnostic of soil input consistent with a terrigenous source the concentration of bhps was 10 times greater in riverine spm than marine spm demonstrating that terrigenous om exported to marine sediments could provide a significant contribution to the marine sedimentary hopanoid inventory given the rich structural diversity of bhps in terrigenous spm interpretations of the sedimentary record of hopanoids in coastal marine settings must resolve inputs from marine pelagic and terrigenous sources

frost flowers as a source of fractionated sea salt aerosol in the polar regions frost flowers collected from the surface of new sea ice near the brunt ice shelf antarctica show depletion in sulphate and sodium relative to other sea water ions this is consistent with loss of mirabilite na2so4 during formation of the brine from which the frost flowers grow aerosol generated from frost flowers would have higher sodium sulphate ratios than aerosol generated from sea water this would explain low values of non sea salt sulphate encountered in winter aerosol and winter layers in ice cores at coastal antarctic sites calculations confirm that the frost flower source should be significant compared to an open water source for coastal regions

vapor transport grain growth and depth hoar development in the subarctic snow measurements from the subarctic snowpack are used to explore the relationship between grain growth and vapor flow the fundamental processes of dry snow metamorphism due to extreme temperature gradients the subarctic pack undergoes extensive depth hoar metamorphism by the end of the winter a five layered structure with a pronounced weak layer near the base of the snow evolves grain size increases by a factor of 2 3 while the number of grains per unit mass decreases by a factor of 10 observed growth rates require significant net inter particle vapor fluxes stable isotope ratios show that there are also significant net layer to layer vapor fluxes soil moisture enters the base of the pack and mixes with the bottom 10 cm of snow while isotopically light water vapor fractionates from the basal layer and is deposited up to 50 cm higher in the pack end of winter density profiles for snow on the ground compared with snow on tables indicate the net layer to layer vapor flux averages 6 x 10 7 kg m 2 s 1 though detailed measurements show the net flux is episodic and varies with time and height in the pack with peak net fluxes ten times higher than average a model driven by observed temperature profiles reproduces the layer to layer flux pattern and predicts the observed weak layer at the base of the snow calculated layer to layer vapor fluxes are ten times higher than inter particle fluxes which implies that depth hoar grain growth is limited by factors other than the vapor supply this finding suggests that gain and loss of water molecules due to sublimation from grains takes place at a rate many times higher than the rate at which grains grow and it explains why grains can metamorphose into different forms so readily

late twentieth century warming in lake tanganyika unprecedented since ad 500 lake tanganyika has become warmer increasingly stratified and less productive over the past 90 years analyses of lake sediments show that this recent warming is unprecedented within the past 1 500 years

structure specific surface area and thermal conductivity of the snowpack around barrow alaska the structure of the snowpack near barrow was studied in march april 2009 verticalprofiles of density specific surface area ssa and thermal conductivity were measuredon tundra lakes and landfast ice the average thickness was 41 cm on tundra and 21 cmon fast ice layers observed were diamond dust or recent wind drifts on top overlayingwind slabs occasional faceted crystals and melt freeze crusts and basal depth hoar layers thetoplayerhadassabetween45and224m

distributional variations in marine crenarchaeotal membrane lipids a new tool for reconstructing ancient sea water temperatures it has recently been shown that membrane lipids of marine crenarchaeota a ubiquitous and abundant component of plankton occur in relatively high concentrations in recent and ancient sediments in this study we investigated the environmental controls on the relative distribution of these lipids in surface sediments we especially focussed on temperature as it is known from the thermophilic genetic relatives of marine crenarchaetoa that the composition of their membrane strongly depends on growth temperature indeed a significant linear correlation r2 0 92 is found between the number of cyclopentane rings in sedimentary membrane lipids derived from marine crenarchaeota and the annual mean sea surface temperatures this suggests that the mechanism of physical adaptation of their membrane compositions to temperature is identical to that of their thermophilic relatives in turn archaeal lipid distributions in sediments may thus allow the reconstruction of sea water temperatures of ancient marine environments

diagenetic and sedimentological controls on the composition of organic matter preserved in california borderland basin sediments compound specific radiocarbon 14c contents stable carbon isotopes and abundances of phytoplankton and vascular plant derived lipid biomarkers alkenones and fatty acids were obtained from santa barbara basin and santa monica basin sediments along with radiocarbon contents of planktic foraminifera and total organic carbon we investigated core top and prebomb sediment intervals at sites from the flanks and depocenters of the basins deposited under contrasting bottom water oxygen concentrations bulk organic matter generally has the lowest radiocarbon levels of all sediment constituents measured whereas planktic foraminifera tend to be the most radiocarbon enriched alkenones are systematically depleted in radiocarbon with respect to foraminifera short chain c14 c 16 c 18 fatty acids decrease rapidly in absolute abundance and relative to longer chain c24 homologues from core top to prebomb samples the loss of short chain fatty acids with depth is associated with 13c depletion of short chain fatty acids indicating preferential preservation of terrestrially derived fatty acids short chain fatty acids tend to be more 14c enriched relative to alkenones in core top sediments whereas longerchain homologues are generally the most radiocarbon depleted of the lipids studied here less refractory compounds e g short chain fatty acids are thus enriched in radiocarbon with respect to more recalcitrant biomarkers alkenones long chain fatty acids the lower 14c content of more refractory compounds reflects a larger proportion of laterally supplied preaged material greater preservation of labile organic compounds observed at the depocenters than in flank sediments results in the presence of younger biomarkers underlining the important influence of selective degradation of labile compounds on their radiocarbon ages

application of lipid biomarkers to detect sources of organic matter in mud volcano deposits and post eruptional methanotrophic processes in the gulf of cadiz ne atlantic abstract the gulf of cadiz is known as an active mud volcano mv and fluid venting region discovered during the training through research ttr expeditions in 1999 ttr 9 here we report a study of lipid biomarkers in the mud breccia matrix from three mvs in this region the lipid biomarker composition revealed strong compositional resemblance as well as similar thermal maturity properties for the studied mvs this indicates that the primary source of the erupted material for these mvs is located in similar litho stratigraphic units in both areas upward migrated fluid went through the sedimentary series of the allochthonous olistrostrome and through the upper cretaceous horizons the relatively immature characteristics of organic matter from both mud breccia rock clasts and matrix together with the more mature properties of hydrocarbon gases from the same sampling locations indicate that source strata for the initial fluid are located deeper in the subsurface than the source strata for the erupted sedimentary material the presence of microbial lipid biomarkers derived from archaea and sulfate reducing bacteria in the mud breccias revealed anaerobic oxidation of methane aom as a dominant microbial process in these habitats our data suggest that the aom derived lipids are at least in part fossil in origin i e they do not reflect active aom communities and thus reflect aom activity in these mvs integrated over time the low concentrations of aom related biomarkers in these mvs suggest relatively low intensities of aom in the studied mv deposits the distribution of biomarkers suggests an abrupt and brief cold seep activity in the past and the absence of a continuous methane influx in the studied locations

comparison of organic uk 37 texh86 ldi and faunal proxies foraminiferal assemblages for reconstruction of late quaternary sea surface temperature variability from offshore southeastern australia several proxies have been developed to reconstruct past sea surface temperature sst but different proxies may reflect temperatures of different seasons and each proxy is characterized by certain uncertainties therefore a multiproxy approach is preferred to precisely reconstruct sst here we reconstruct sst of the ocean offshore southeastern australia murray canyons area for the last 135 ka using three independent organic proxies texh86 based on glycerol dialkyl glycerol tetraethers gdgts uk 37 based on alkenones and ldi based on long chain diols in addition to foraminiferal faunal assemblages the organic proxy records show similar trends with the highest temperature 21 c for uk 37 and texh86 and 25 c for ldi during the last interglacial and lowest temperature 8 c for texh86 10 c for uk 37 and 12 c for ldi during the last glacial maximum however the differences in absolute sst estimates obtained by the organic proxies varied over time with differences of up to 9 c between ldi and texh86 the seasonal sst reconstructions based on the modern analogue of foraminiferal assemblages also show similar trends as the organic proxies with highest temperatures during the last interglacial 23 c for the warmest month sst 20 c for mean annual and 18 c for the coolest month and lowest temperature during the last glacial maximum 14 c for the warmest month 11 c for mean annual and 9 c for the coolest month down core comparison between the reconstructed ssts of the organic and inorganic proxies shows that ldi inferred temperatures compare well with the temperature of the warmest month texh86 with the temperature of the coolest month and uk 37 with mean annual temperature an increase in texh86 sst estimates relative to those of other proxies during deglaciations and interglacials suggests that either winter temperatures rapidly warmed possibly due to an invigoration of the leeuwin current over the core site or there was a change in the growth season of the thaumarchaeota the source organism of gdgts our study shows the benefits of a multiproxy approach in the interpretation of sst proxies leading to a more robust knowledge of past ocean temperature changes

an overview of seasonal snow metamorphism the grains in seasonal snow undergo rapid and radical transformations in size shape and cohesion these grain characteristics affect all of the basic properties of snow snow is characterized as either wet or dry depending on the presence of liquid water wet snow is markedly different at low and high liquid contents dry snow is characterized as either an equilibrium form or a kinetic growth form that is it is either well rounded or faceted of course many snow grains display either transitional features between two of these categories or features which arise from other processes snow is classified depending on the dominant processes of its metamorphism