connection between weak stratospheric vortex events and the pacific decadal oscillation we investigate the possible impacts of the pacific decadal oscillation pdo on the occurrence of weak stratospheric polar vortex wsv events in the northern hemisphere winter wsv events which are defined when polar cap geopotential height anomalies at 50 hpa fall below the 10th percentile in winter are observed more frequently during positive pdo phases than during negative pdo phases additionally tropospheric wave forcings that drive wsv events are remarkably different between the two phases of the pdo during the positive pdo phase the vertical propagation of wavenumber one waves plays a predominant role with a rather minor contribution of wavenumber two waves this contrasts with the negative pdo phase when the wsv events are primarily caused by wavenumber two waves this difference is partly related to the pdo induced tropospheric circulation anomalies over the north pacific whose zonal wavenumber one component constructively destructively interferes with climatological planetary scale waves during positive negative pdo winters the predominant wavenumber two wave forcings during the negative pdo phase are likely related to the enhanced tropospheric eddy activity over alaska that results from the poleward shift of the pacific jet in response to the negative pdo

behavior of planetary waves before and after stratospheric sudden warming events in several phases of the equatorial qbo almost a thousand stratospheric sudden warming ssw events are obtained through long time integrations with a simple global circulation model and a statistical analysis based on such a large number of samples is made to investigate behavior of planetary waves before and after ssw events depending on the phase of the equatorial quasi biennial oscillation qbo an idealized zonal momentum forcing to mimic a phase of the qbo is imposed under a perpetual winter condition and eight phases of the qbo wind forcing are examined for 8 10 800 day datasets some systematic dependence on the phase of the qbo wind forcing is seen in the anomaly of the eliassen palm ep flux in the winter hemisphere both in the 10 800 day average and in the composites for ssw events the composite analysis shows that before ssw events the upward ep flux in the troposphere and midlatitude lower stratosphere as well as the equatorward flux above the tropopause is larger in the westerly forcing runs than in the easterly forcing runs after ssw events the upward ep flux in the troposphere is still larger in the westerly forcing runs correlation associated with the differences among ssw events that occurred in each run is significantly positive between the magnitude of the warming and the planetary wave activity flux before all the events in qbo wind forcing in the stratosphere but only in the easterly forcing runs in the troposphere

n alkane and pollen reconstruction of terrestrial climate and vegetation for n w africa over the last 160 kyr abstract proxy environmental records have been obtained for the last 160 kyr from the well studied odp site 658 ca 200 km west of cap blanc n w africa 20 5 n 18 35 w 2263 m water depth this collective assessment of several terrigenous proxies lithogenic fraction n alkane content and 13 c values and pollen counts provides a better understanding of the climate and vegetation history of the n w african hinterland the results indicate that for this site beneath the main dust pathway of the saharan air layer sal the dust flux increased during dry glacial periods but the amounts of pollen and n alkanes delivered were lower in accord with the decreased density of vegetation cover of their source areas the c 4 pollen was also very low but the heavy 13 c values of the n alkanes accorded with a mainly c 4 plant origin evidently the load of sal pollen was much reduced but not the sal wind strength

understanding the contrasting north atlantic oscillation anomalies of the winters of 2010 and 2014 the present study investigates the two contrasting winters of 2010 and 2014 during which the north atlantic oscillation nao was mainly negative and positive respectively in the north pacific contrasting anomalies were also present with a straight zonal pacific jet in 2010 and a strong poleward deviation of the pacific jet in its exit region in 2014 using reanalysis data sets and adopting a nonlinear initial value approach with a quasi geostrophic model we show that the pacific north american anomalies are responsible for shaping synoptic wave trains propagating across north america this in turn largely determines the nature of wave breaking and the synoptic eddy feedback onto the mean flow in the north atlantic and finally the nao phase in such a proposed mechanism synoptic wave activity forms the cornerstone of the dynamical relationship between the north pacific and north atlantic large scale anomalies during the contrasting winters of 2010 and 2014

early paleogene evolution of terrestrial climate in the sw pacific southern new zealand 1 we present a long term record of terrestrial climate change for the early paleogene of the southern hemisphere that complements previously reported marine temperature records using the mbt cbt proxy based on the distribution of soil bacterial glycerol dialkyl glycerol tetraether lipids we reconstructed mean annual air temperature mat from the middle paleocene to middle eocene 62 42 ma for southern new zealand this record is consistent with temperature estimates derived from leaf fossils and palynology as well as previously published mbt cbt records which provides confidence in absolute temperature estimates our record indicates that through this interval temperatures were typically 5 c warmer than those of today at such latitudes with more pronounced warming during the early eocene climate optimum eeco 50 ma when mat was 20 c moreover the eeco mats are similar to those determined for antarctica with a weak high latitude terrestrial temperature gradient 5 c developing by the middle eocene we also document a short lived cooling episode in the early late paleocene when mat was comparable to present this record corroborates the trends documented by sea surface temperature sst proxies although absolute ssts are up to 6 c warmer than mats although the high calibration error of the mbt cbt proxy dictates caution the good match between our mat results and modeled temperatures supports the suggestion that sst records suffer from a warm summer bias particularly during times of peak warming

mapping of c4 plant input from north west africa into north east atlantic sediments abstract mapping the abundance of 13c in leaf wax components in surface sediments recovered from the seafloor off northwest africa 0 35 n reveals a clear pattern of 13c distribution indicating systematic changes in the proportions of terrestrial c3 and c4 plant input at 20 n latitude we find that isotopically enriched products characteristic of c4 plants account for more than 50 of the terrigenous inputs this signal extends westward beneath the path of the dust laden sahara air layer sal high c4 contributions apparently carried by january trade winds also extend far into the gulf of guinea similar distributions are obtained if summed pollen counts for the chenopodiaceae amaranthaceae and the poaceae are used as an independent c4 proxy we conclude that the specificity of the latitudinal distribution of vegetation in north west africa and the pathways of the wind systems trade winds and sal are responsible for the observed isotopic patterns observed in the surface sediments molecular isotopic maps on the marine sedimentary time horizons e g during the last glacial maximum are thus a robust tool for assessing the phytogeographic changes on the tropical and sub tropical continents which have important implications for the changes in climatic and atmospheric conditions

a case of post depositional aerobic degradation of terrestrial organic matter in turbidite deposits from the madeira abyssal plain abstract a set of oxidized and unoxidized sediment intervals from the f turbidite identified in two piston cores from the madeira abyssal plain map was analyzed for calcium carbonate total organic carbon toc total nitrogen tn stable carbon composition of toc 13c toc total hydrolyzable amino acids thaa total neutral sugars tsug lignin phenols lig two different lipid biomarkers of marine phytoplankton origin and vascular plantwax n alkanes and n acids comparison shows changes for all properties depicting the effect of post depositional aerobic oxidation the oxidation process re mineralized approximately 80 of the toc and approximately 60 of the tn in the original deposit and left the residual organic matter depleted in 13c by 1 7 2 9 thaa and tsug account for 10 or less of the toc in all samples leaving approximately 90 of the toc chemically unidentified thaa tsug lig marine phytoplankton biomarkers and plantwax n acids were lost from the oxidized deposit to an extent as great as that for toc two non protein amino acids alanine and aminobutyric acid and plant wax n alkanes displayed much less degradation 9 37 and concentrated 3 3 4 8 times relative to toc by the oxidation process these observations show that both marine and terrestrial components contribute to the re mineralized toc fraction a binary mixing approach was used to model quantitatively the change in 13c toc and plantwax n alkane concentration results suggest that terrestrial organic carbon contributes approximately 15 to the toc content of the original turbidite its abundance increases approximately 2 4 times as a consequence of the oxidation process and approximately 40 and 90 of the terrestrial and marine component of toc in the original turbidite respectively was destroyed by the oxidation process although selective preservation of terrestrial relative to marine organic carbon is a well documented phenomenon in sedimentary processes this study represents the first attempt to assess the sensitivity of terrestrial organic matter to oxidative degradation in a sedimentary environment

eolian transport of glycerol dialkyl glycerol tetraethers gdgts off northwest africa branched glycerol dialkyl glycerol tetraethers brgdgts of purportedly terrestrial origin are frequently detected in marine sediments even in remote ocean sites where no direct impact from land erosion via rivers takes place at these places the most likely explanation for the presence of brgdgts is in situ production or eolian transport but neither possibility has been demonstrated for the open ocean here we report the presence of isoprenoid iso and brgdgts in eight dust samples collected off northwest africa based on previous studies prevailing wind patterns bulk chemistry n alkane composition and isotopic signatures we show that northwest africa is the likely principal origin of the gdgts in the dust the concentrations of plant wax n alkanes in the dust are several orders of magnitude higher than those of gdgts and based on the distributions of these two compound classes we infer that they tag different carbon pools and sources of organic matter our finding demonstrates that brgdgts and isogdgts in marine sediments and wind derived deposits can have an eolian source consequently climate reconstruction may be attempted from wind derived deposits of brgdgts even in remote oceanic areas

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

upward and downward injection of rossby wave activity across the tropopause a new aspect of the troposphere stratosphere dynamical linkage propagation of zonally confined rossby wave activity between the troposphere and lower stratosphere of the southern hemisphere during austral winter and spring of 1997 is studied by using a wave activity flux and refractive index both defined for stationary rossby waves on a zonally asymmetric time mean flow a particular event of large scale quasi stationary cyclogenesis in the troposphere is discussed to which downward wave activity injection from anticyclonic anomalies upstream that had developed in the exit region of the lower stratospheric polar night jet pnj contributed substantially consistent with that downward injection phase lines of observed stream function anomalies exhibited a distinct eastward tilt with height the development of the anticyclonic anomalies occurred at the leading edge of a quasi stationary rossby wave train propagating along the pnj that had originated from a tropospheric blocking ridge farther upstream though less common than upward wave activity injection across the tropopause similar events of downward wave activity injection occurred several times during that season primarily in the regions south of australia and over the central south pacific over each of which the pnj exit overlapped with a tropospheric subpolar jet to form a vertical waveguide locally it is argued that the downward wave activity propagation is essentially due to refraction in the vertically sheared westerlies and the zonal asymmetries in the time mean flow are a likely factor for the observed geographical preference of the downward wave activity injection copyright 2005 royal meteorological society

two paradigms of baroclinic wave life cycle behaviour two idealized baroclinic wave 6 life cycles examined here suggest a framework of opposite extremes a in which to view the behaviour of real synoptic scale disturbances in middle latitudes and b in which to interrelate the synoptic and wave theoretic viewpoints using the saturation propagation saturation sps picture of wave 6 life cycle behaviour the two life cycles dented by lc1 and lc2 are higher resolution versions of the simmons hoskins basic and anomalous cases showing strong and weak late decay of eddy kinetic energy eke they illustrate in varying degrees two extreme types of behaviour here disignated anticyclonic and cyclonic and epitomized by strongly contrasting upper air trough behaviour anticyclonic behaviour dominates the late stages of lc1 and is characterized by backward tilted thinning troughs being advected anticyclonically and equatorward as in the commoner cases of planetary scale mid stratospheric rossby wave breaking cyclonic behaviour dominates lc2 and is characterized by forward tilted broadening troughs wrapping themselves up cyclonically and poleward producing major cut off cyclones in high latitudes these morphologies are visualized by upper air maps of potential temperature on the nominal tropopause defined as a constant potential vorticity surface some atmospheric mid latitude disturbances examined here using the same visualization applied to operational analyses show the same two extreme types of trough behaviour together with intermediate cases the sps picture is re examined using eliassen palm and refractive index cross sections it is shown in particular by reference to a wave activity theorem of haynes that the late stages of lc2 can be looked upon as a remarkably clear and morphologically novel large amplitude counterpart of the nonlinear reflection scenario of rossby wave critical layer theory the late stages of lc1 by constrast look more akin to an nonlinear critical layer absorption scenario lc2 exhibits region of largely undular pv contours adjacent to a nonlinear of irreversiby deformen pv contous in the latter region pv rearrangement and hence absorption of rossby wave activity has largely ceased this accounts for the more persistent ekee in the lc2 case

northern hemisphere winter circulation associated with the north atlantic oscillation and stratospheric polar night jet the interannual variability of the atmospheric winter circulation as characterized by the geopotential height at 500 hpa and temperature at 850 hpa associated with the north atlantic oscillation nao and stratospheric polar night jet pnj is examined it is suggested that the wintertime atmospheric circulation related to the nao index can be separated into two different modes of variability one is a regional mode characterized by a meridional dipole type pattern in the 500 hpa geopotential height anomaly field over the atlantic region the other having more zonal structure extends over wider region of the northern hemisphere this is also related to the lower stratospheric polar night jet air temperature near the surface over the eastern part of the eurasian continent is more closely correlated with the above mentioned hemispheric mode of variability than the regional nao

selective organic matter preservation in burn down turbidites on the madeira abyssal plain 1 oxidized intervals of five organic rich madeira abyssal plain map turbidites deposited during the miocene pliocene and pleistocene all displayed comparable major loss of total organic carbon toc 84 3 1 accompanied by a negative isotopic 13c shift ranging from 0 3 to 2 9 major but significantly lower loss of total nitrogen ntot 61 7 1 also occurred leading to a decrease in toc relative to ntot c ntot and a 1 3 to 2 7 ntot isotopic 15n shift compound specific isotopic measurements on plant wax n alkanes indicate the terrestrial organic component in the unoxidized deposits is 13c enriched owing to significant c4 contribution selective preservation of terrestrial relative to marine organic carbon could account for the 13c behavior of toc upon oxidation but only if a 13c depleted component of the bulk terrestrial signal is selectively preserved in the process although the c ntot decrease and positive 15n shift seems inconsistent with selective terrestrial organic preservation results from analysis of a modern eolian dust sample collected in the vicinity indicate these observations are compatible regardless of the specific explanation for these isotopic observations however our findings provide evidence that paleoreconstruction of properties such as pco2 using the 13c of toc is a goal fraught with uncertainty whether or not the marine sedimentary record considered is contaminated with significant terrestrial input nonetheless despite major and selective loss of both marine and terrestrial components as a consequence of postdepositional oxidation intensive organic geochemical proxies such as the alkenone unsaturation index u37k appear resistant to change and thereby retain their paleoceanographic promise

distributions of branched gdgts in soils and lake sediments from western uganda implications for a lacustrine paleothermometer bacterially produced branched glycerol dialkyl glycerol tetraethers gdgts are ubiquitous in soils and lake sediments and can potentially be used to reconstruct past temperatures in lakes however it is still unclear if these compounds are derived from eroded soils or if they are produced in situ to better understand environmental controls on the distributions of these compounds and the sources of branched gdgts to lake sediments we compare branched gdgt distributions and concentrations in lake sediments and catchment soils within a 3600 m altitudinal transect in western uganda reconstructed mean annual air temperature maat determined from the degree of methylation mbt and cyclisation cbt of branched gdgts in soils decreases with increasing altitude as is expected from the air temperature gradient in our transect however we observe significant offsets between observed and reconstructed temperatures in soils from wet high elevation soils but not in most dry low elevation soils branched gdgt distributions differ significantly between lake sediments and soils at all elevations with greater differences at low elevations than at high elevations these data support previous hypotheses that branched gdgts are produced in situ in lakes and suggest that the abundance of water in soil environments may play a role in controlling the distribution of branched gdgts while branched gdgts in lacustrine sediments can be used to reconstruct temporal temperature variations in lakes we urge caution in utilizing this proxy in lacustrine systems with high soil loadings especially if there is evidence of changing clastic fluxes through time

glacial interglacial contrast in mbt cbt proxies in the south china sea implications for marine production of branched gdgts and continental teleconnection abstract two proxies derived from branched glycerol dialkyl glycerol tetraethers br gdgts the methylation index of branched tetraethers mbt and the cyclization ratio of branched tetraethers cbt are often used to reconstruct paleo mean annual air temperature maat and soil ph based on the premise that br gdgts in the marine environment are mainly of terrigenous origin however mounting evidence indicates that br gdgts can be produced in situ in oceanic settings which may affect maat reconstruction and the use of other related paleoenvironmental proxies we have determined br gdgt distributions in a sedimentary core md05 2896 7 from the southern south china sea which provided high resolution profiles of mbt and cbt indices as well as the branched and isoprenoid tetraether bit index bit varied systematically with glacial interglacial cycles reaching much lower

decoupled warming and monsoon precipitation in east asia over the last deglaciation our understanding of the continental climate development in east asia is mainly based on loess paleosol sequences and summer monsoon precipitation reconstructions based on oxygen isotopes delta o 18 of stalagmites from several chinese caves based on these records it is thought that east asian summer monsoon easm precipitation generally follows northern hemisphere nh summer insolation however not much is known about the magnitude and timing of deglacial warming on the east asian continent in this study we reconstruct continental air temperatures for central china covering the last 34 000 yr based on the distribution of fossil branched tetraether membrane lipids of soil bacteria in a loess paleosol sequence from the mangshan loess plateau the results indicate that air temperature varied in phase with nh summer insolation and that the onset of deglacial warming at similar to 19 kyr bp is parallel in timing with other continental records from e g antarctica southern africa and south america the air temperature increased from is c at the onset of the warming to a maximum of 27 degrees c in the early holocene similar to 12 kyr bp in agreement with the temperature increase inferred from e g pollen and phytolith data and permafrost limits in central china comparison of the tetraether membrane lipid derived temperature record with loess paleosol proxy records and stalagmite 5180 records shows that the strengthening of easm precipitation lagged that of deglacial warming by ca 3 kyr moreover intense soil formation in the loess deposits caused by substantial increases in summer monsoon precipitation only started around 12 kyr bp ca 7 kyr lag our results thus show that the intensification of easm precipitation unambiguously lagged deglacial warming and nh summer insolation and may contribute to a better understanding of the mechanisms controlling ice age terminations

a strong phase reversal of the arctic oscillation in midwinter 2015 2016 role of the stratospheric polar vortex and tropospheric blocking in january 2016 asia and north america experienced unusual cold temperatures although the global average of surface air temperature broke the warmest record during a strong el nino event this was closely related to the remarkable phase transition of the arctic oscillation ao which can be explained by stratosphere troposphere interactions first the quasi biennial oscillation changed to its westerly phase in summer 2015 and the stratospheric polar vortex was stronger in early to midwinter 2015 2016 as blocking did not occur in december the associated downward propagation signal resulted in a strongly positive ao in late december 2015 second after late december the positive phase of pacific north america pattern became apparent in el nino event which strengthened the aleutian anticyclone in the stratosphere in addition an equivalent barotropic blocking anticyclone was established in the troposphere over asia the coexistence of blocking over asia and north america characterized the negative ao and a strong zonal wave number 2 pattern due to stronger zonal wave number 2 signals from the troposphere the stronger stratospheric polar vortex was elongated with two cyclonic centers over asia and the north atlantic in january the resultant southward displacement of polar vortices was followed by rare snowfall in the subtropical region of east asia and a heavy snowstorm on the east coast of the united states

a mechanistic model study of slowly propagating coupled stratosphere troposphere variability observational studies reveal the oscillatory nature of coupled stratosphere troposphere variability which is characterized by a slowly downward propagating anomalous zonal mean zonal wind during the winter the term slowly is employed compared to the rapid variation associated with stratospheric sudden warmings in fact strong stratospheric warming events are embedded in this slowly propagating variability as is shown in a companion paper kodera et al this issue in the present study the mechanism producing such variability at all levels of the atmosphere is investigated by developing a simple model that extends from the earth s surface to 80 km altitude the model is a quasi geostrophic channel model similar to that used by holton and mass 1976 but it includes two meridional fourier components and latitudinal variation in the gradient of the coriolis parameter by this extension the present model can incorporate both the subtropical and polar night jet and also treat the horizontal propagation of planetary waves as well as vertical propagation the results of the simulation reproduce qualitatively well the main observed features interaction between the planetary waves and zonal mean flow produces oscillations in the winter stratosphere and zonal wind anomalies created in the subtropics of the stratopause propagate downward into the polar region of the troposphere which provoke changes in the meridional propagation of tropospheric planetary waves

propagation of the arctic oscillation from the stratosphere to the troposphere geopotential anomalies ranging from the earth s surface to the middle stratosphere in the northern hemisphere are dominated by a mode of variability known as the arctic oscillation ao the ao is represented herein by the leading mode the first empirical orthogonal function of low frequency variability of wintertime geopotential between 1000 and 10 hpa in the middle stratosphere the signature of the ao is a nearly zonally symmetric pattern representing a strong or weak polar vortex at 1000 hpa the ao is similar to the north atlantic oscillation but with more zonal symmetry especially at high latitudes in zonal mean zonal wind the ao is seen as a north south dipole centered on 40 45 n in zonal mean temperature it is seen as a deep warm or cold polar anomaly from the upper troposphere to 10 hpa the association of the ao pattern in the troposphere with modulation of the strength of the stratospheric polar vortex provides perhaps the best measure of coupling between the stratosphere and the troposphere by examining separately time series of ao signatures at tropospheric and stratospheric levels it is shown that ao anomalies typically appear first in the stratosphere and propagate downward the midwinter correlation between the 90 day low pass filtered 10 hpa anomaly and the 1000 hpa anomaly exceeds 0 65 when the surface anomaly time series is lagged by about three weeks the tropospheric signature of the ao anomaly is characterized by substantial changes to the storm tracks and strength of the midtropospheric flow especially over the north atlantic and europe the implications of large stratospheric anomalies as precursors to changes in tropospheric weather patterns are discussed

spatial heterogeneity of sources of branched tetraethers in shelf systems the geochemistry of tetraethers in the berau river delta kalimantan indonesia abstract the bulk organic matter composition total organic carbon toc content and 13ctoc and composition of isoprenoid and branched glycerol dialkyl glycerol tetraethers gdgt in surface sediments from 43 stations in the berau river delta east kalimantan indonesia including two coast shelf transects and stations within the river mouth were examined to reveal the spatial heterogeneity in these parameters in order to assess the impact of a tropical river loaded with suspended matter on the sedimentary organic matter in the shelf system the high resolution study showed that despite the extensive transport of eroded soil material by the river to the sea terrestrial organic matter and brgdgts are only deposited on a relatively small part of the shelf the concentrations of brgdgts are highest up to 120 g g 1 toc in sediments deposited in and close to the mouth of the berau river and their distribution indicates that they represent a mixture of soil derived and river in situ produced brgdgts crenarchaeol concentrations reach 700 g g 1 toc in sediments deposited on the outer shelf due to thaumarchaeotal production in shelf waters this results in a strong gradient 0 93 0 03 in the bit index with high values in the river mouth and low values on the shelf the decline in the bit index is caused by both decreasing concentrations of the brgdgts and increasing concentrations of crenarchaeol the bit index shows a highly significant but non linear relationship with 13ctoc on the shelf in the area not under the direct influence of the berau river cyclic brgdgts become relatively dominant most probably due to in situ production in the alkaline pore waters of the surface sediments the spatial heterogeneity of sources of brgdgts on the berau shelf complicates the use of brgdgts as temperature proxies application of the global soil calibration to sedimentary mixtures of brgdgts in the river influenced area of the shelf results in a severe underestimation of mean annual air temperature mat by 6 c this is due to the mixed origin of the brgdgts which are not only derived from soil erosion but likely also from riverine production as has been observed for other river systems comparison of the berau shelf other shelf systems indicates that in situ production of brgdgts in shelf sediments is a widespread phenomenon that is especially pronounced at water depths of ca 50 300 m it is hypothesized that this is so because benthic in situ production of heterotrophic brgdgt producing bacteria is fueled by the higher delivery of fresh organic matter to these sediments as the consequence of higher primary productivity in shelf waters and a decreased mineralization due to the relatively short settling times of particles on the shelf for palaeoclimatic studies of marine shelf sediments the application of brgdgts as proxies is severely complicated by the heterogeneity of sources of brgdgts comparison of the brgdgt composition of soils with those of shelf sediments may assist in deciding if sedimentary brgdgts are predominantly derived from soil erosion several methods to do so are discussed

constraints on the sources of branched tetraether membrane lipids in distal marine sediments abstract branched glycerol dialkyl glycerol tetraethers brgdgts are membrane lipids produced by soil bacteria and occur in near coastal marine sediments as a result of soil organic matter input their abundance relative to marine derived crenarchaeol quantified in the bit index generally decreases offshore however in distal marine sediments low relative amounts of brgdgts can often still be observed sedimentary in situ production as well as dust input have been suggested as potential though as yet not well constrained sources in this study brgdgt distributions in dust were examined and compared with those in distal marine sediments dust was sampled along the equatorial west african coast and brgdgts were detected in most of the samples albeit in low abundance their degree of methylation and cyclisation expressed in the mbt methylation index of branched tetraethers and dc degree of cyclisation indices respectively were comparable with those for african soils their presumed source comparison of dc index values for brgdgts in global soils congo deep sea river fan sediments and dust with those of distal marine sediments clearly showed however that distal marine sediments had significantly higher values this distinctive distribution is suggestive of sedimentary in situ production as a source of brgdgts in marine sediments rather than dust input the presence of in situ produced brgdgts in marine sediments means that caution should be exercised when applying the mbt cbt palaeothermometer to sediments with low bit index values i e

seasonal effects of water temperature and dissolved oxygen on the isogdgt proxy tex86 in a mediterranean oligotrophic lake abstract to appraise the application of isoprenoid glycerol dialkyl glycerol tetraethers isogdgts as paleoclimate proxies in small lakes we investigated the effect of seasonal variability in temperature and dissolved oxygen concentration do on the gdgt contents and its proxy in the water column of an oligotrophic karst lake in the catalan pre pyrenees lake montcortes from october 2013 to november 2014 we collected suspended particulate matter spm monthly at three depths and retrieved the sediment from a trap located at 20 m below the lake surface the gdgt contents in the spm and sediment trap presented a marked seasonal variation showing the highest values in summer and autumn in addition the isogdgt proxy tex86 in spm and sediment trap showed a marked seasonal variability which matched the temperatures of the upper water column and fit the published global trend between tex86 and mean annual lake surface temperature lst however in the hypolimnion where oxygen was depleted for most of the study period we found that tex86 co varied with do this further confirms previous claims with seasonal field data that the sedimentary tex86 lst signal may be confounded by do conditions consequently the application of tex86 to estimate lst should be carefully appraised in environments with depleted do conditions

a synoptic and dynamical characterization of wave train and blocking cold surge over east asia through an agglomerative hierarchical clustering method cold surges over east asia are classified into two distinct types based on the spatial pattern of the geopotential height anomalies at 300 hpa one is the wave train type that is associated with developing large scale waves across the eurasian continent the other is the blocking type whose occurrence accompanies subarctic blocking during the wave train cold surge growing baroclinic waves induce a southeastward expansion of the siberian high and strong northerly winds over east asia blocking cold surge on the other hand is associated with a southward expansion of the siberian high and northeasterly winds inherent to a height dipole consisting of the subarctic blocking and the east asian coastal trough the blocking cold surge tends to be more intense and last longer compared to the wave train type the wave train cold surge is associated with the formation of a negative upper tropospheric height anomaly southeast of greenland approximately 12 days before the surge occurrence further analysis of isentropic potential vorticity reveals that this height anomaly could originate from the lower stratosphere over the north atlantic cold surge of the blocking type occurs with an amplifying positive geopotential and a negative potential vorticity anomaly over the arctic and the northern eurasia in stratosphere these anomalies resemble the stratospheric signature of a negative phase of the arctic oscillation this stratospheric feature is further demonstrated by the observation that the blocking type cold surge occurs more often when the arctic oscillation is in its negative phase

a biomarker perspective on dust productivity and sea surface temperature in the pacific sector of the southern ocean abstract in this study we present a new multiproxy data set of terrigenous input marine productivity and sea surface temperature sst from 52 surface sediment samples collected along e w transects in the pacific sector of the southern ocean allochthonous terrigenous input was characterized by the distribution of plant wax n alkanes and soil derived branched glycerol dialkyl glycerol tetraethers brgdgts 230th normalized burial of both compound groups were highest close to the potential sources in australia and new zealand and are strongly related to lithogenic contents 232th indicating common sources and transport detection of both long chain n alkanes and brgdgts at the most remote sites in the open ocean strongly suggests a primarily eolian transport mechanism to at least 110 w i e by prevailing westerly winds two independent organic sst proxies were used the u 37 k based on alkenones and the tex86 based on isoprenoid gdgts both u 37 k and tex86 indices show robust relationships with temperature over a temperature range between 0 5 and 20 c likely implying different seasonal and regional imprints on the temperature signal alkenone based temperature estimates best reflect modern summer sst in the study area when using the polar calibration of sikes et al 1997 in contrast tex86 derived temperatures may reflect a subsurface signal rather than surface 230th normalized burial of alkenones is highest close to the subtropical front and is positively related to the deposition of lithogenic material throughout the study area in contrast highest isogdgt burial south of the antarctic polar front may be largely controlled by diatom blooms and thus high opal fluxes during austral summer

centennial scale cycles in middle holocene sea level along the southeastern swedish baltic coast submerged sea grasses and stoneworts growing in the immediate nearshore of the baltic sea are sensitive indicators of sea level the alternating changes in concentrations of sea grass and stonewort macrofossils obtained from an ancient lagoon of the baltic sea are ascribed to middle holocene sea level fluctuations along the southeastern swedish coast abundances of stonewort and sea grass macrofossils between 7500 and 6000 cal calibrated yr b p were lower and less variable indicating high and relatively stable sea level low frequency fluctuations of sea level with a 1470 yr period during this time may have been forced by tidal action in the millennial band after 6000 cal yr b p sea level was lower and exhibited strong fluctuations at centennial time scales as evident in the stonewort and sea grass macrofossil records such a high frequency oscillatory mode of sea level may have been regulated by centennial scale solar activities or tidal actions or both the modest variation in solar irradiance is unlikely to have resulted in large scale oscillations of sea level by directly changing the steric component instead it governed sea level fluctuations by changing the regional storminess through a north atlantic oscillation nao like system storms embedded in the nao induced southwesterly winds played a major role in the centennial scale fluctuations of the baltic sea level by pushing saltwater from the north sea into the baltic basin less

sources and distributions of branched and isoprenoid tetraether lipids on the amazon shelf and fan implications for the use of gdgt based proxies in marine sediments branched glycerol dialkyl glycerol tetraethers brgdgts in river fan sediments have been used successfully to reconstruct mean annual air temperature maat and soil ph of the congo river drainage basin however in a previous study of amazon deep sea fan sediments the reconstructed maats were ca 10 c colder than the actual maat of the amazon basin in this study we investigated this apparent offset by comparing the concentrations and distributions of brgdgts in amazon river suspended particulate matter spm and sediments to those in marine spm and surface sediments the riverine brgdgt input was evident from the elevated brgdgt concentrations in marine spm and surface sediments close to the river mouth the distributions of brgdgts in marine spm and sediments varied widely but generally showed a higher relative abundance of methylated and cyclic brgdgts than those in the river since this difference in brgdgt distribution was also found in intact polar lipid ipl derived brgdgts which were more recently produced the change in the marine brgdgt distribution was most likely due to marine in situ production consequently the maats calculated based on the methylation of branched tetraethers mbt and the cyclisation of branched tetraethers cbt were lower and the cbt derived ph values were higher than those of the amazon basin however spm and sediments from stations close to the river mouth still showed mbt cbt values that were similar to those of the river therefore we recommend caution when applying the mbt cbt proxy it should only be used in sediment cores that were under high river influence the influence of riverine derived isoprenoid gdgt isogdgt on the isogdgt based tex86 temperature proxy was also examined in marine spm and sediments an input of riverine isogdgts from the amazon river was apparent but its influence on the marine tex86 was minor since the tex86 of spm in the amazon river was similar to that in the marine spm and sediments

tropical upper tropospheric potential vorticity intrusions during sudden stratospheric warmings abstractthe intrusion of lower stratospheric extratropical potential vorticity into the tropical upper troposphere in the weeks surrounding the occurrence of sudden stratospheric warmings ssws is examined the analysis reveals that ssw related pv intrusions are significantly stronger penetrate more deeply into the tropics and exhibit distinct geographic distributions compared to their climatological counterparts while climatological upper tropospheric and lower stratospheric utls pv intrusions are generally attributed to synoptic scale rossby wave breaking it is found that ssw related pv intrusions are governed by planetary scale wave disturbances that deform the extratropical meridional pv gradient maximum equatorward as these deformations unfold planetary scale wave breaking along the edge of the polar vortex extends deeply into the subtropical and tropical utls in addition the material pv deformations also reorganize the geographic structure of the utls waveguide which alters where synopti

nonlinear relation of the arctic oscillation with the quasi biennial oscillation a nonlinear principal component analysis nlpca is applied to a set of monthly mean time series from january 1956 to december 2007 consisting of the arctic oscillation ao index derived from 1 000 hpa geopotential height anomalies poleward of 20 n latitude and the zonal winds observed at seven pressure levels between 10 and 70 hpa in the equatorial stratosphere to investigate the relation of the ao with the quasi biennial oscillation qbo the nlpca is conducted using a new compact neural network model the nlpca modeling of the dataset of the ao index and qbo winds offers a clear picture of the relation between the two oscillations in particular the phase of covariation of the oscillations defined by the two nonlinear principal components of the dataset progresses with a predominant 28 4 month periodicity this predominant cycle is modulated by an 11 year cycle the variation of the ao index with the qbo phase also shows that the average ao index is positive when the westerly qbo phase descends past 30 hpa and conversely the average ao index is negative when the easterly qbo phase descends past 30 hpa this relationship is evident during the boreal cold season from november to april but non existent during the boreal warm season from may to october

stratospheric impact on tropospheric winds deduced from potential vorticity inversion in relation to the arctic oscillation the zonal mean state of the atmosphere in the northern hemisphere in winter is determined by the temperature at the earth s surface and by two potential vorticity pv anomalies defined as that part of the pv field that induces a wind field centred over the north pole one in the upper troposphere lower stratosphere utls extending to the subtropics and the other over the polar cap in the lower to middle stratosphere isentropic pv inversion demonstrates that the utls pv anomaly induces the main part of the zonal mean wind in the troposphere including the subtropical jet stream while the stratospheric pv anomaly induces the polar night stratospheric jet the stratospheric pv anomaly has a greater amplitude and extends further downwards if the arctic oscillation ao index is positive also the utls pv anomaly has a slightly larger amplitude if the ao index is positive but the meridional pv gradient in the subtropics that is associated with this anomaly is greatest when the ao index is negative resulting in a stronger subtropical jet when the ao index is negative pv inversion translates the utls pv anomaly into a wind anomaly and a static stability anomaly the resulting differences in the vertical wind shear and in the brunt vaisala frequency between the two ao phases show a larger baroclinicity in the extratropics when the ao index is positive this explains why more extratropical cyclones are observed when the ao index is positive copyright 2010 royal meteorological society

increased dust deposition in the pacific southern ocean during glacial periods dust deposition in the southern ocean constitutes a critical modulator of past global climate variability but how it has varied temporally and geographically is underdetermined here we present data sets of glacial interglacial dust supply cycles from the largest southern ocean sector the polar south pacific indicating three times higher dust deposition during glacial periods than during interglacials for the past million years although the most likely dust source for the south pacific is australia and new zealand the glacial interglacial pattern and timing of lithogenic sediment deposition is similar to dust records from antarctica and the south atlantic dominated by patagonian sources these similarities imply large scale common climate forcings such as latitudinal shifts of the southern westerlies and regionally enhanced glaciogenic dust mobilization in new zealand and patagonia

latitudinal distribution of terrestrial lipid biomarkers and n alkane compound specific stable carbon isotope ratios in the atmosphere over the western pacific and southern ocean abstract we investigated the latitudinal changes in atmospheric transport of organic matter to the western pacific and southern ocean 27 58 n 64 70 s molecular distributions of lipid compound classes homologous series of c15 to c35 n alkanes c8 to c34 n alkanoic acids c12 to c30 n alkanols and compound specific stable isotopes 13c of c29 and c31 n alkanes were measured in marine aerosol filter samples collected during a cruise by the r v hakuho maru the geographical source areas for each sample were estimated from air mass back trajectory computations concentrations of tc and lipid compound classes were several orders of magnitude lower than observations from urban sites in asia a stronger signature of terrestrial higher plant inputs was apparent in three samples collected under conditions of strong terrestrial winds unresolved complex mixtures ucm showed increasing values in the north pacific highlighting the influence of the plume of polluted air exported from east asia n alkane average chain length acl distribution had two clusters with samples showing a relation to latitude between 28 n and 47 s highest acl values in the tropics whilst a subset of southern samples had anomalously high acl values compound specific carbon isotopic analysis of the c29 25 6 to 34 5 and c31 n alkanes 28 3 to 37 revealed heavier 13c values in the northern latitudes with a transition to lighter values in the southern ocean by comparing the isotopic measurements with back trajectory analysis it was generally possible to discriminate between different source areas the terrestrial vegetation source for a subset of the southernmost southern ocean is enigmatic the back trajectories indicate eastern antarctica as the only intercepted terrestrial source area these samples may represent a southern hemisphere background of well mixed and very long range transported higher plant organic material

quasi biennial modulation of the southern hemisphere stratospheric polar vortex observations reveal that the wintertime southern hemisphere stratospheric polar vortex is modulated by the phase of the equatorial quasi biennial oscillation qbo the high latitude southern stratosphere is shown to be slightly colder throughout the winter and the final warming occurs later when the qbo is in its west phase during may october the modulation of winds by the qbo is confined to midlatitudes at the edge of the polar vortex the difference between west and east phase composites of zonal mean wind during november at the time of the final warming in the southern hemisphere exceeded 14 ms 1 this difference is very similar to that in january in the northern hemisphere while northern hemisphere qbo effects are optimized using equatorial winds near 40 hpa southern hemisphere effects are best seen using 25 hpa winds

branched glycerol dialkyl glycerol tetraethers in pleistocene loess paleosol sequences three case studies abstract branched glycerol dialkyl glycerol tetraethers branched gdgts are membrane lipids presumably derived from anaerobic heterotrophic soil bacteria empirical studies have shown that the composition of branched gdgts in topsoils varies in degree of cyclization and methylation expressed as cbt and mbt i e cyclization and methylation index of branched tetraethers depending on soil ph and mean annual air temperature mat here we present results from three case studies namely three well studied loess paleosol sequences lpss in which we measured the branched gdgts in order to test the applicability of these biomarkers for paleoclimate reconstruction the results show that major disagreements exist between expectations based on available stratigraphic pedological and geochemical data on the one hand and gdgt derived reconstructions on the other hand caution is therefore advised when interpreting the respective indices in lps studies we discuss several potential directions for future research i some of the target peaks in the hplc chromatograms consist of multiple unidentified compounds this needs to be addressed by way of improved component separation identification and new calibration studies ii factors other than mat and soil ph that could affect membrane composition should be further investigated e g nutrient availability and redox conditions as well as seasonality and changes in bacterial communities iii gdgts may be produced in non negligible amounts at depth and thus overprint the original in situ signal a concern that could be termed growth depth effect iv gdgts should also be analyzed in dust source regions and contemporaneous eolian sediments in order to address a potential redeposition effect

using peak ground velocity to characterize the response of soil pile system in liquefying ground abstract performance of a soil pile system can be significantly influenced by many characteristics of an earthquake ground motion and it is vitally important to identify the ground motion parameters that have the most significant effects on the response when predicting the level of movement or damage in the pile in this paper three dimensional finite element fe analysis was conducted to simulate a centrifuge experiment on the nonlinear behavior of a pile founded in liquefiable soil subjected to strong earthquake motions the result of the fe analysis was found to be in reasonable agreement with the experimental data as such the calibrated fe model was used to investigate the influence of ground motion parameters on the pile soil response in both liquefied and non liquefied soils it was found that peak ground velocity pgv is an appropriate ground motion parameter to characterize the response of the soil pile system in liquefying ground the maximum pile bending moment pile lateral displacement and soil lateral displacement increased with increasing pgv moreover near fault ground motions could result in more severe damage to the pile compared to far fault grounds motions this study provided a new insight on the influence of ground motion parameters in particular pgv on the dynamic performance of a pile foundation

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

composition age and provenance of organic matter in nw african dust over the atlantic ocean 1 eolian dust deposited on a meteorology buoy over the boreal winter and spring of 1992 1993 in the northeast atlantic off northwest africa 18 n 22 w afforded sufficient material for detailed assessment of its biogeochemical characteristics and provenance the sample was subjected to microscopic examination and bulk elemental isotopic black carbon and molecular lignin lipid analyses the bulk elemental composition and organic carbon oc content 1 02 dry weight establishes the dust s origin as continental upper crust and is typical of dusts that emanate from west africa these data are in accord with the extensive satellite imagery documenting the transit of dust clouds from the sahara and sahel regions e g nasa toms aerosol index microscopic examination reveals that charcoal like particles from vegetation fires black carbon bc are the most abundant morphologically distinct organic components accelerator mass spectrometry ams 14c analysis yields conventional 14c ages for bulk oc of 1260 40 years and bc of 2070 35 years taken together with corresponding stable carbon isotopic compositions 13c 18 9 and 15 1 respectively these results suggest the presence of biomass and burning residues derived from predominantly c4 vegetation that accumulated in soils over the late holocene molecular level measurements are also consistent with this scenario for example lignin derived phenols in the dustfall sample indicate a significant contribution of angiosperm grass type tissue the altered nature of the lignin suggests storage as residues in soils solvent extractable lipid constituents include a marked leaf wax type component with a molecular and stable carbon isotopic composition similar to those observed in surface marine sediments in this region the hydrocarbon fraction contained some diesel type contamination but the n alkanes c23 c33 retained a prominent odd even distribution with 13c ranging from 26 7 to 28 5 the suite of even carbon numbered n alkanols c22 c32 is 14c dated at 647 150 years with 13c values ranging from 23 9 to 30 4 the long chain n alkanoic acids c22 c32 exhibited 13c values ranging from 22 6 to 27 4 these waxes are evidently a mixed signal derived from contemporary c3 and c4 vegetation and from ablated soils and desiccated lake sediments of middle to late holocene age this molecular approach shows promise as a tool for continental paleoenvironmental assessment particularly with respect to past vegetation cover regional aridity and wind systems

comparison of instrumental and gdgt based estimates of sea surface and air temperatures from the skagerrak sea surface temperatures ssts and annual mean air temperatures mats are estimated for the last 200 years from glycerol dialkyl glycerol tetraethers gdgts proxies in a marine sediment core from the skagerrak off southern norway the reconstructed values compare well with annual ssts and summer air temperatures obtained from composite regional instrumental records the results provide further confidence in the application of proxies based on gdgts to estimate past temperatures

the middle eocene climatic optimum meco a multiproxy record of paleoceanographic changes in the southeast atlantic odp site 1263 walvis ridge the middle eocene climatic optimum meco 40 ma was a transient period of global warming that interrupted the secular cenozoic cooling trend we investigated the paleoceanographic paleoenvironmental and paleoecological repercussions of the meco in the southeast atlantic subtropical gyre ocean drilling program site 1263 tex86 and 18o records support an 4 c increase in surface and deepwater temperatures during the meco there is no long term negative carbon isotope excursion cie associated with the early warming consistent with other sites and there is no short term negative cie 50 kyr during the peak of the meco in contrast to what has been observed at some sites this lack of a cie during the peak of the meco at site 1263 could be due to poor sediment recovery or geographic heterogeneity of the 13c signal benthic and planktic foraminiferal mass accumulation rates markedly declined during meco indicating a reduction of planktic foraminiferal production and export productivity vertical 13c gradients do not indicate major changes in water column stratification and there is no biomarker or micropaleontological evidence that hypoxia developed we suggest that temperature dependency of metabolic rates could explain the observed decrease in foraminiferal productivity during warming the kinetics of biochemical reactions increase with temperature more so for heterotrophs than for autotrophs steady warming during meco may have enhanced heterotroph i e foraminiferal metabolic rates so that they required more nutrients these additional nutrients were not available because of the oligotrophic conditions in the region and the lesser response of primary producers to warming the combination of warming and heterotroph starvation altered pelagic food webs increased water column recycling of organic carbon and decreased the amount of organic carbon available to the benthos

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

provenance of present day eolian dust collected off nw africa 1 atmospheric dust samples collected along a transect off the west african coast have been investigated for their physical grain size distribution mineralogical and chemical major elements composition on the basis of these data the samples were grouped into sets of samples that most likely originated from the same source area in addition shipboard collected atmospheric meteorological data modeled 4 day back trajectories for each sampling day and location and total ozone mapping spectrometer aerosol index data for the time period of dust collection february march 1998 were combined and used to reconstruct the sources of the groups of dust samples on the basis of these data we were able to determine the provenance of the various dust samples it appears that the bulk of the wind blown sediments that are deposited in the proximal equatorial atlantic ocean are transported in the lower level 900 hpa ne trade wind layer which is a very dominant feature north of the intertropical convergence zone itcz however south of the surface expression of the itcz down to 5 s where surface winds are southwesterly we still collected sediments that originated from the north and east carried there by the ne trade wind layer as well as by easterly winds from higher altitudes the fact that the size of the wind blown dust depends not only on the wind strength of the transporting agent but also on the distance to the source hampers a direct comparison of the dust s size distributions and measured wind strengths however a comparison between eolian dust and terrigenous sediments collected in three submarine sediment traps off the west coast of nw africa shows that knowledge of the composition of eolian dust is a prerequisite for the interpretation of paleorecords obtained from sediment cores in the equatorial atlantic

source settling and degradation of branched glycerol dialkyl glycerol tetraethers in the marine water column abstract branched glycerol dialkyl glycerol tetraethers branched gdgts are commonly found in distal marine sediments however their presence in the water column source and delivery process are not fully understood in this study we examined seasonal and depth variation in the flux of branched gdgts in sinking particles and underlying sediment at 39 n 147 e in the mid latitude nw pacific from november 1997 to august 1999 branched gdgts showed synchronous variation in their sinking flux at different depths and the variation was similar to that of lithogenic material of eolian dust origin their degrees of cyclization and methylation were nearly constant and bear some resemblance to those of alkaline soils this suggests that westerly winds transport branched gdgts to the study site via the atmosphere from continental asia the sinking flux of branched gdgts was higher in 1999 than in 1998 presumably reflecting changes in the migration path of asian dust in response to the el nino southern oscillation synchronous variation in branched gdgt concentrations at different depths implies rapid vertical transport of branched gdgts to deep water with a sinking velocity exceeding 260 m d 1 the sinking flux of the branched gdgts decreased with increasing depth but the rate of decrease was much smaller than those of other compounds the preservation efficiency of branched gdgts was 3 5 6 4 of surface inputs at the water sediment interface which is much higher than those of isoprenoid gdgts 1 0 1 3 and other compounds the branched and isoprenoid tetraether bit index values were extremely low i e