debris fan constrictions and flood hydraulics in river canyons some implications from two dimensional flow modelling rapids in river canyons are frequently found at sites where debris fans constrict flow along the channel whereas some fans may have persisted in the same location with unchanging geometry for centuries to millennia others have changed in response to flow conditions imposed by successive floods such a change in boundary conditions may alter local flow hydraulics this paper utilizes two dimensional flow modelling to compare flood hydraulics along two alternative versions of an idealized reach of a river canyon one with uniform width gradient and cross section and a second perturbed by a prominent debris fan along the valley wall the flow pattern along the reach with the fan is far more complex than the pattern along the uniform reach maximum velocity along the debris fan reach is up to 50 per cent higher than along the uniform reach maximum bed shear stress is up to three or four times higher and an area of supercritical flow is predicted extending from the nose of the fan into the zone of flow expansion immediately downstream comparison of model output along longitudinal profiles of the two reaches indicates that the backwater effect of the fan extends several valley widths upstream predicted flows based on the same stage are as much as 190 to 230 per cent greater along the uniform reach than along the debris fan reach reconstruction of palaeoflood discharge based on remnant flood marks in the vicinity of the fan would be sensitive to assumptions about boundary conditions that existed in the past this effect relaxes over a longitudinal distance of several hundred metres furthermore there are significant cross stream gradients that change slope and direction several times in the vicinity of the fan calling into question the utility of one dimensional step backwater hydraulic models for predicting high water marks in areas of complex valley morphology

global climatic anomalies associated with extremes in the southern oscillation abstract composite temperature and precipitation anomalies during various stages of an event in the southern oscillation so have been computed for several hundred stations across the globe large regions of coherent significant signals are shown to exist for both extremes of the so with warm event signals generally opposite to those during cold events in addition during the year preceding the development of an event in the so year 1 climatic anomalies tend to be opposite to those during the following year year 0 this confirms that the biennial tendency of the so over the pacific indian ocean sectors is also present in more remote regions with climatic signals related to the so many of the signals are consistent enough from event to event to be useful for extended range forecasting purposes

reconstruction of a paleotemperature record from 0 3 3 7ka for subtropical south china using lacustrine branched gdgts from huguangyan maar abstract the concentrations of glycerol dialkyl glycerol tetraethers gdgts in catchment soils suspended particulate matter spm lake bottom sediments and sediment cores from huguangyan maar subtropical south china were investigated the distribution of isoprenoid gdgts has gdgt 0 crenachaol 2 and therefore the widely used tex 86 is precluded from being used for the calculation of lake water temperature in this lake the total concentration of branched gdgts br gdgts in the soils spm and lake bottom sediments ranged from 91 3 223 7 ng g 17 8 41 4 ng l and 864 2 2008 6 ng g respectively the molecular composition of br gdgts mbt values methylation of br gdgts and cbt values the cyclization ratio of br gdgts in the catchment soils differ from those in lake materials this difference indicates that br gdgts in the lake are largely produced in situ based on the global lake specific mbt cbt mat mean air temperature calibration the air temperature was reconstructed for lacustrine material in huguangyan maar the estimates fall in the range 23 2 23 8 c similar to the average value of local mat for the preceding 45 years the paleotemperature history of huguangyan maar was reconstructed using br gdgts extracted from a sediment core spanning the period 0 3 3 7 ka and ranged from 24 6 to 26 3 c the temperature pattern of huguangyan maar based on the global lake specific mbt cbt mat resembles those recorded in east china using numerous indicators the pattern consists of five cool and four warm periods including two distinct phases within the medieval warm period 900 1300 ad the coldest temperature in the little ice age 1550 1850 ad and reveals even finer temperature variations than other indicators this new method based on br gdgts produced in situ in the subtropical lacustrine environment provides a new sensitive and precise paleotemperature proxy for lacustrine sediments for which other gdgt based proxies are not applicable

a lacustrine gdgt temperature calibration from the scandinavian arctic to antarctic renewed potential for the application of gdgt paleothermometry in lakes quantitative climate reconstructions are fundamental to understand long term trends in natural climate variability and to test climate models used to predict future climate change recent advances

storm track dynamics this paper reviews the current state of observational theoretical and modeling knowledge of the midlatitude storm tracks of the northern hemisphere cool season observed storm track structures and variations form the first part of the review the climatological storm track structure is described and the seasonal interannual and interdecadal storm track variations are discussed in particular the observation that the pacific storm track exhibits a marked minimum during midwinter when the background baroclinicity is strongest and a new finding that storm tracks exhibit notable variations in their intensity on decadal timescales are highlighted as challenges that any comprehensive storm track theory or model has to be able to address physical processes important to storm track dynamics make up the second part of the review the roles played by baroclinic processes linear instability downstream development barotropic modulation and diabatic heating are discussed understanding of these processes forms the core of our current theoretical knowledge of storm track dynamics and provides a context within which both observational and modeling results can be interpreted the eddy energy budget is presented to show that all of these processes are important in the maintenance of the storm tracks the final part of the review deals with the ability to model storm tracks the success as well as remaining problems in idealized storm track modeling which is based on a linearized dynamical system are discussed perhaps on a more pragmatic side it is pointed out that while the current generation of atmospheric general circulation models faithfully reproduce the climatological storm track structure and to a certain extent the seasonal and enso related interannual variations of storm tracks in depth comparisons between observed and modeled storm track variations are still lacking

holocene climatic and environmental change on the western tibetan plateau revealed by glycerol dialkyl glycerol tetraethers and leaf wax deuterium to hydrogen ratios at aweng co mean annual air temperature maat and precipitation isotope records for the holocene were obtained from the analysis of the relative distribution of branched glycerol dialkyl glycerol tetraethers and compound specific hydrogen isotope ratios of leaf waxes from a sediment core from aweng co on the western tibetan plateau wtp our results indicate that the indian monsoon mainly influenced aweng co during the holocene during the early holocene when summer insolation was at a maximum the monsoonal influence was strong and the climate was warm and wet both the summer and winter insolation were relatively weak and aweng co was cool and dry during the middle holocene 6 3 ka indicating a weakening of the indian monsoon the southward displacement of the intertropical convergence zone and relatively low atmospheric methane content may have contributed to the middle holocene cooling on the wtp during the late holocene with a further increase in winter insolation and decrease in summer insolation the summer monsoon weakened and the maat on the wtp gradually increased depleted leaf wax hydrogen isotope ratios during the late holocene can be attributed to accelerated glacier melting because of the elevated maat

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 15 ka ph record from an alpine lake in north china derived from the cyclization ratio index of aquatic brgdgts and its paleoclimatic significance abstract a well dated sediment core from an alpine lake in north china gonghai lake was used for analysis of branched glycerol dialkyl glycerol tetraether lipids brgdgts based on the cyclization ratio index cbt of the brgdgts and using different terrestrial and lacustrine cbt ph empirical relationships the reconstructed ph records over the past ca 15 ka exhibited similar trends of variation although the absolute ph values were different in order to better understand the reconstructed ph record samples of surface soils from the dust source area and the catchment of gonghai lake as well as surface sediments from the lake were collected for instrumental ph measurements and modern brgdgt analysis the instrumental ph results demonstrated that the surface soils from the dust source area were alkaline while those from the catchment of gonghai lake were acidic in addition the instrumental ph results for the surface sediments from the lake were slightly alkaline and the corresponding ph values were intermediate between those of the two surface soil source groups this may reflect the effect of the input of material from different sources on the sedimentary ph record however the results from modern brgdgts in some of the surface soils and surface sediment samples demonstrate that brgdgts in the core sediments from gonghai lake are predominantly of aquatic origin therefore the cbt derived ph record over the past ca 15 ka from the lake can be interpreted as a record of the lake water ph history which is consistent with the carbonate content record from a parallel core from the same lake in addition using the modern lacustrine calibration the cbt derived ph values for surface sediments of gonghai lake are consistent with instrumental modern lake water ph values for the lake further comparison indicates that the lake water ph is controlled mainly by the degree of humidity of the local climate which is closely related to the intensity of the east asian summer monsoon easm therefore the ph record can be used as an indicator of easm intensity our results demonstrate that on the basis of careful analysis of its origins the cbt index of aquatic brgdgts can be used for lake water ph reconstruction and subsequent paleoclimate reconstruction and that in north china the lake water ph is controlled mainly by the degree of humidity of the local climate

the efficacy of stream power and flow duration on geomorphic responses to catastrophic flooding abstract geomorphologists have long studied the impacts of extreme floods yet the association between the magnitude of flow parameters discharge velocity shear stress or stream power and resulting geomorphic effectiveness remains vague and non deterministic attempts have been made to include flow duration and total expenditure of stream power in combination with peak unit stream power as important variables but there has been minimal exploration of this hydraulic combination taking advantage of tropical storm irene s rapid track through eastern vermont usa in late summer 2011 this paper presents the array of geomorphic responses to a short duration time to peak of

coarse sediment distribution as evidence of an elevation limit for flash flooding bear creek colorado bear creek is a tributary of the south platte river in central colorado the stream flows east from an elevation of 4348 m at the continental divide to the mountain front at 1670 m it thus encompasses the 2300 m elevation limit for substantial rainfall flooding in the colorado front range proposed by jarrett maximum paleoflood discharges estimated from flood deposits at four sites along bear creek demonstrate a consistent decrease in unit discharge with increasing elevation and support the hypothesis of an upper elevation limit for rainfall floods the unit discharge values were used to explain coarse sediment distribution along bear creek measurements of coarse grained channel sediment at 19 sites along the creek indicate a decrease in particle size in flood deposits with increasing elevation as well as a decrease in the size of clasts introduced to the main channel along tributaries these changes in grain size are hypothesized to reflect changes in the competence of channel transport as a result of snowmelt dominated versus rainfall dominated discharge regimes above and below 2100 m elevation calculations of flow competence versus entrainment thresholds for the deposits may support this interpretation one of the geomorphic implications of the elevation limit on flash flooding is a reversal of the usual downstream fining trend in coarse channel sediments

seasonal variations in the southern hemisphere storm tracks and jet streams as revealed in a reanalysis dataset abstract regional characteristics of the climatological seasonal variations in southern hemisphere sh storm tracks are examined based on a reanalysis dataset when differences in vertical structure between the subpolar and subtropical jet streams spj and stj respectively are considered the regional characteristics can be interpreted reasonably well from a potential vorticity perspective of baroclinic eddy growth and downstream development of a baroclinic wave packet eddy activity in the upper and lower tropospheres is strongest in the core region of the spj over the eastern south atlantic and indian ocean throughout the year even in austral winter when the intense stj forms over the indian ocean and south pacific showing its eddy driven nature the spj accompanies the strong surface westerlies along a well defined baroclinic zone above an intense oceanic frontal zone in this core region of the storm track low level eddy activity is strongly correlated with the local near surface baroclinicity

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

significance of a midlatitude sst frontal zone in the formation of a storm track and an eddy driven westerly jet abstract in a set of idealized aquaplanet experiments with an atmospheric general circulation model to which zonally uniform sea surface temperature sst is prescribed globally as the lower boundary condition an assessment is made of the potential influence of the frontal sst gradient upon the formation of a storm track and an eddy driven midlatitude polar front jet pfj and on its robustness against changes in the intensity of a subtropical jet stj in experiments with the frontal midlatitude sst gradient as that observed in the southwestern indian ocean transient eddy activity in each of the winter and summer hemispheres is organized into a deep storm track along the sst front with an enhanced low level baroclinic growth of eddies in the winter hemisphere another storm track forms just below the intense stj core but it is confined to the upper troposphere with no significant baroclinic eddy growth underneath the near surface westerlies are strongest near the midlatitude sst front as observe

side valley tributary fans in high energy river floodplain environments sediment sources and depositional processes navarro river basin california side valley tributary fans within the main axial valley river floodplain system are integral components of the sediment assemblage characterizing floodplains in the high energy navarro river basin california laboratory analyses of subsurface core and auger samples from four study sites reveal that sediment size distributions within the floodplain are controlled by spatial and temporal variation in sediment sources and depositional processes over 75 of sediment within individual lower fan strata are poorly sorted and include gravel clasts inferred to be contributions from the side valley tributary whereas remaining strata are composed of fine sediment less than 2 mm without gravel high water marks indicate that portions of the side valley tributary fans are episodically inundated by axial valley overbank flow a factor that influences fan relief and profile thus two dominant sources supply sediment to this transitional environment side valley tributaries and the axial valley river the transport and depositional processes that supply sediment to the fans operate under three conditions 1 tributary debris or fluvial flows and selective entrainment of fines by fan surface flows deposit sediment when there is no overbank flow from the axial channel 2 overbank flow deposits sediment derived from the axial valley river when there is no tributary input and 3 tributary flows deposit sediment while the floodplain is inundated by floods from the axial valley river the mixing and interlayering of sediment from these disparate sources within the active floodplain illustrate the significance of both hillslope floodplain and channel flood plain interactions in high energy fluvial systems with floodplains

tetraether lipids from the southern yellow sea of china implications for the variability of east asia winter monsoon in the holocene to better understand the origin and distribution of organic matter om in the yellow sea ys and to delineate potential interactions between the atmosphere and the marine system during the holocene we reconstructed terrestrial input and temperature variation for the last 8 8 ka bp using glycerol dialkyl glycerol tetraethers gdgts obtained from a 4 4 m sediment core ysc 1 from the southern ys the archaea derived isoprenoid gdgts igdgts were dominated by gdgt 0 and crenarchaeol the igdgts and bacteria derived branched gdgts bgdgts correlated well and varied in opposition to the bit branched vs isoprenoid tetraether index this may be due to varying river runoff and influence of the ys coastal current yscc and ys warm current yswc related to the east asia winter monsoon eawm which made the bit proxy less suitable for tracing soil om input to the ys tex86 tetraether index of tetraethers consisting of 86 carbons derived sea surface temperature values sst varied from 9t o 16c close to the sst in the ys cold season the mbt cbt methylation of branched tetraethers and cyclization of branched tetraethers derived continental temperature ranged from 10 to 19 c indicating an annual mean air temperature for the middle and low drainage basin of the ys these two temperature records were decoupled but both correlated with the variation in the eawm suggesting an intimate link between eawm and temperature variation in east asia

holocene mean annual air temperature maat reconstruction based on branched glycerol dialkyl glycerol tetraethers from lake ximenglongtan southwestern china abstract here we investigate the sources of branched glycerol dialkyl glycerol tetraethers brgdgts in lake ximenglongtan from southwestern china and present a brgdgts based holocene 9 4 cal kyr bp temperature reconstruction the similarities in the distributions of brgdgts between surface sediments and catchment soils indicate that soil is the dominant source of brgdgts this contrasts with the recent emphasis on lacustrine gdgts in other regional studies holocene temperature evolution is characterized by an early cool phase with a mean annual air temperature maat of 12 5 c prior to 7 6 cal kyr bp followed by a rapid warming towards the local thermal maximum maat 13 8 c from 7 6 to 5 5 cal kyr bp and a subsequent long term cooling that ended at 1 5 cal kyr bp temperature changes after 1 5 cal kyr bp show high variability and low correspondence to global climate events such as the medieval warm period overall holocene temperature variation has been primarily controlled by boreal summer insolation changes the larger amplitude 1 5 4 0 c in annual cooling during the early holocene in maat contrasts with summer temperature records from this region range of cooling 0 3 1 0 c and indicates the likely influence of lower winter temperature on maat variation we suggest that substantial remnants of the northern hemisphere ice sheets during the early holocene enhanced the winter westerlies and east asian winter monsoon eawm and decreased the winter temperature in southwestern china leading to a cold early holocene climate

distribution of glycerol dialkyl glycerol tetraethers in surface sediments of lake qinghai and surrounding soil abstract glycerol dialkyl glycerol tetraethers gdgts are increasingly used as proxies for paleoclimate studies of marine and lacustrine environments while gdgt based proxies have been applied to a number of lake environments globally little is known about the distribution of gdgts on the qinghai tibet plateau we have investigated the isoprenoid gdgts igdgts and branched gdgts bgdgts in lake qinghai sediments and the surrounding surface soil in order to examine their potential use as paleoclimate proxies on the qinghai tibet plateau the results show that i the values of the igdgt bgdgt ratio for surrounding soil were at the higher end among globally distributed soils and consequently bit values avg 0 71 at the lower end ii the tex86 values decreased while the mbt and cbt values increased along an onshore soil nearshore sediment offshore sediment transect iii the tex86 values for the offshore sediments were almost identical and their inferred temperatures were close to mean summer surface water temperature and iv the bgdgt inferred mean annual air temperature maat and ph for soil were consistent with measured maat and ph however the cbt inferred ph for offshore sediments seemed inconsistent with the ph of lake water or sediment our results suggest that i the higher ph may be an important factor leading to the higher igdgt bgdgt values and lower bit values in surrounding surface soil ii both igdgts and bgdgts may originate from terrestrial input and in situ production for this saline lake especially for nearshore sediments however for offshore sediments terrestrial igdgt input seems minor and tex86 may be useful for paleoclimate studies of lake qinghai

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

coupled thermal and hydrological evolution of tropical africa over the last deglaciation we analyzed the distribution of branched tetraether membrane lipids derived from soil bacteria in a marine sediment record that was recovered close to the congo river outflow and the results enabled us to reconstruct large scale continental temperature changes in tropical africa that span the past 25 000 years tropical african temperatures gradually increased from 21 to 25 c over the last deglaciation which is a larger warming than estimated for the tropical atlantic ocean a direct comparison with sea surface temperature estimates from the same core revealed that the land sea temperature difference was through the thermal pressure gradient an important control on central african precipitation patterns

crenarchaeotal membrane lipids in lake sediments a new paleotemperature proxy for continental paleoclimate reconstruction paleoclimate studies of continental environments have been hampered by the lack of an independent paleotemperature proxy a novel sea surface temperature proxy has been proposed for marine systems based on membrane lipids of marine crenarchaeota this proxy will provide an independent continental paleotemperature tool that will allow paleoclimatologists to address fundamental questions about temperature variability in continental environments and its relationship to climate change

southward displacement of the upper atmosphere zonal jet in the eastern north pacific due to global warming the jet stream over the eastern north pacific enpj as a core of the atmospheric flow is known to strongly fluctuate meridionally and its meridional displacement directly influences adjacent regional climate here we investigate how this jet will be changed due to global warming by analyzing the future scenario experiments of climate model intercomparion project phase iii cmip3 and phase v 5 it was found that both enpj and the eastern tropical pacific intertropical convergence zone itcz tend to move southward which are closely related to the tropical eastern pacific warming trend tropical eastern pacific warming leads to not only the southward migration of itcz by southward shifting the off equatorial eastern pacific warm pool but also the southward shift of enpj by increasing baroclinic instability of the atmosphere in subtropical region through intensifying the meridional sea surface temperature sst gradient not primary but yet secondly the southward shift of itcz contributes to the southward shift of enpj through a kinematic connection bridged by local hadley circulation

spatiotemporal variability of the precipitation dipole transition zone in the western united states 1 el nino southern oscillation related hydroclimatic variability in the western united states is characterized by a north south dipole pattern of precipitation anomalies with opposing signs here i use a high resolution dataset to analyze spatiotemporal patterns in the transition zone between the centers of opposite association results indicate that the transition zone is spatially limited west of the continental divide consisting of a narrow zone within the 40 42 n latitude band and portions of eastern washington eastern oregon and western colorado the transition zone was narrower when the southern oscillation index and the pacific decadal oscillation pdo were in a constructive phase and during the negative atlantic multidecadal oscillation phase although the transition zone has remained remarkably stationary across the great basin shifts likely pdo related have occurred over time in the west coast states implications for water resource planning in river basins underlying the transition zone vary by region

bacterial tetraether membrane lipids in peat and coal testing the mbt cbt temperature proxy for climate reconstruction abstract peatlands are widespread and important natural archives of environmental change here we explore the potential of the recently introduced mbt cbt proxy methylation index and cyclisation ratio of branched tetraethers to estimate past annual mean air temperature mat based on the distribution of bacterially derived branched glycerol dialkyl glycerol tetraether gdgt membrane lipids in peat and coal to this end branched gdgts in an ombrotrophic peat bog from switzerland and three coal deposits of increasing maturity were analysed for the surface of the bog reconstructed annual mat is higher than both measured annual mat and measured in situ pore water temperature changes in the cbt ratio considered a proxy for ph with depth in the bog do not match with present day in situ pore water ph but coincide with a peat stratigraphic boundary this indicates that gdgts down the bog profile are predominantly fossil and not derived from extant biomass the mbt cbt derived annual mat record also shows a large drop at this stratigraphic boundary which likely relates to past change in trophic status of the bog branched gdgts are abundant in an immature lignite vitrinite reflectance r o 0 25 but occur in low amount in a slightly more mature coal r o 0 32 annual mat could be reconstructed for the lignite alone and is higher than other proxy based estimates from approximately the same time and location our results indicate potential for the application of the mbt cbt proxy in peat and immature coals but improved constraints on the effects of different types of peat on branched gdgt distributions as well as improved calibration of mat estimates are needed before the method can be confidently applied

branched glycerol dialkyl glycerol tetraethers in arctic lake sediments sources and implications for paleothermometry at high latitudes branched glycerol dialkyl glycerol tetraethers brgdgts are analyzed in different lakes of the mackenzie canadian arctic and kolyma siberian arctic river basins to evaluate their sources and the implications for brgdgt based paleothermometry in high latitude lakes the comparison of brgdgt distributions and concentrations in the lakes with those in river suspended particulate matter riverbank sediments and permafrost material indicates that brgdgts in arctic lake sediments have mixed sources in contrast to global observations distributional offsets between brgdgts in arctic lakes and elsewhere in the catchment are minor likely due to the extreme seasonality and short window of biological production at high latitudes consequently both soil and lake calibrated brgdgt based temperature proxies return sensible temperature estimates even though the mean air temperature mat in the arctic is below the calibration range the original soil calibrated mbt cbt methylation of branched tetraethers cyclisation of branched tetraethers proxy generates mats similar to those in the studied river basins whereas using the recently revised mbt cbt calibration overestimates mat the application of the two global lake calibrations generating summer air temperatures sat and mat respectively illustrates the influence of seasonality on the production of brgdgts in lakes as the latter overestimates actual mat whereas the sat based lake calibration accounts for this influence and consequently returns more accurate temperatures our results in principle support the application of brgdgt based temperature proxies in high latitude lakes in order to obtain long term paleotemperature records for the arctic although the calibration and associated transfer function have to be selected with care

role of the gulf stream and kuroshio oyashio systems in large scale atmosphere ocean interaction a review abstract ocean atmosphere interaction over the northern hemisphere western boundary current wbc regions i e the gulf stream kuroshio oyashio and their extensions is reviewed with an emphasis on their role in basin scale climate variability sst anomalies exhibit considerable variance on interannual to decadal time scales in these regions low frequency sst variability is primarily driven by basin scale wind stress curl variability via the oceanic rossby wave adjustment of the gyre scale circulation that modulates the latitude and strength of the wbc related oceanic fronts rectification of the variability by mesoscale eddies reemergence of the anomalies from the preceding winter and tropical remote forcing also play important roles in driving and maintaining the low frequency variability in these regions in the gulf stream region interaction with the deep western boundary current also likely influences the low frequency variability surface heat fluxes damp the low frequency sst anomalies ove

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

constraints on the application of the mbt cbt palaeothermometer at high latitude environments svalbard norway abstract branched glycerol dialkyl glycerol tetraethers gdgts are membrane lipids of unknown bacteria that are ubiquitous in soil and peat two indices based on the distribution of these lipids in soils the cyclization of branched tetraethers cbt and the methylation of branched tetraethers mbt indices have been shown to correlate with soil ph and mean annual air temperature mat and soil ph respectively and can be used to reconstruct mat in palaeoenvironments to verify the extent to which branched gdgts in marine sediments reflect the distribution pattern on land and whether these proxies are applicable for palaeoclimate reconstruction in high latitude environments with a mat of

a physical mechanism of the precipitation dipole in the western united states based on pdo storm track relationship it is known that the western united states us precipitation displays a north south contrast i e the so called precipitation dipole during el nino and la nina winters furthermore the pacific decadal oscillation pdo has been known to modulate this precipitation dipole however the underlying physical mechanism regulating this modulation is not well understood this study revisits previous studies and suggests a physical mechanism of precipitation dipole modulation based on the pdo storm track relationship we found that both jet stream and storm track tend to move northward southward over the north pacific during negative positive pdo winters contributing to the increase of precipitation over the northwestern southwestern us respectively this relationship is robust regardless of el nino southern oscillation enso possibly facilitating modulation of the precipitation dipole moreover changes in oceanic baroclinicity associated with the pdo phase are suggested to be responsible for anchorage of storm tracks over the north pacific

variability of the observed midlatitude storm tracks in relation to low frequency changes in the circulation pattern abstract the principal modes of month to month variability of the wintertime storm tracks over the north pacific and north atlantic are identified by empirical orthogonal function analysis of the root mean square statistics of bandpass 2 5 6 day filtered geopotential height data for 19 yr one of the two leading modes depicts fluctuations in the level of synoptic scale activity without any noticeable spatial displacement of the storm track axes whereas the other mode is associated with meridional shifts of the storm tracks from their time averaged positions higher order modes are indicative of diversion or truncation of cyclone tracks in particular geographical regions it is demonstrated that the leading storm track modes are linked to some of the best known monthly averaged teleconnection patterns the dipolar western pacific and western atlantic patterns for the monthly mean flow are seen to be accompanied by marked changes in the intensity of the storm tracks over the western oceans whereas the m

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

half precessional dynamics of monsoon rainfall near the east african equator extensive records exist with which to assess the relationship between external climate forcings such as changes in insolation and climate variability for middle and high latitudes but records from equatorial regions are relatively few especially from regions experiencing the passage of the intertropical convergence zone a continuous and well resolved climate proxy record of hydrological variability during the past 25 000 years from equatorial east africa is now presented and analysed

geomorphic complexity and sensitivity in channels to fire and floods in mountain catchments abstract fires and floods are important drivers of geomorphic change while the hydrologic and geomorphic effects of fires have been studied at the hillslope scale we have much more limited data on post fire runoff channel changes and inferred or measured sediment storage and delivery at larger scales in this study we intensively documented channel changes over four years in two very similar 15 km2 catchments in the northern colorado front range skin gulch and hill gulch that were burned primarily at high and moderate severity in june 2012 ten and 11 cross sections and longitudinal profiles along the lower channel network were repeatedly surveyed in skin gulch and hill gulch respectively summer thunderstorms generally caused deposition in the valley bottoms while incision resulted from the intervening baseflows and spring snowmelt but a very high intensity summer thunderstorm in skin gulch just one week after burning caused much more deposition than in hill gulch fifteen months after burning both watersheds experienced an exceptional long duration flood resulting from a multi day rainstorm with a several hundred year recurrence interval this removed nearly all of the deposited post fire sediment along with some of the older valley bottom deposits the expansion and coarsening of the channel has greatly decreased the geomorphic sensitivity of both watersheds to future floods and eliminated the more typical and persistent post fire depositional signature the channel changes in skin gulch after the fire and long duration flood were much greater than in hill gulch and this can be attributed to the much greater sediment deposition in skin gulch shortly after the fire reduced geomorphic sensitivity in hill gulch resulting from a large erosional flood in 1976 and the spatial distribution of burn severity and storm rainfalls leading to lower peak flows in hill gulch these results suggest that fires in the rocky mountains can trigger significant and dynamic hillslope and channel changes over sub decadal timescales but unusually long or intense rainstorms can cause larger and more persistent changes regardless of whether a catchment has recently burned

seasonal variability of branched glycerol dialkyl glycerol tetraethers brgdgts in a temperate lake system quantitative climate reconstructions are crucial for understanding the magnitude of and mechanisms behind natural and anthropogenic climate change yet there are few proxies that can reliably reconstruct terrestrial temperature branched glycerol dialkyl glycerol tetraethers brgdgts are bacterial membrane lipids that are increasingly used to reconstruct paleotemperature from lake sediments but despite their potential we have a poor understanding of 1 autochthonous vs allochthonous sources of brgdgts in lakes and 2 the seasonality of and environmental controls on brgdgt production within lakes to investigate these factors we examined water column suspended particulate matter spm and settling particles from a sediment trap collected on a biweekly to monthly basis over a period of three years at lower king pond a small kettle lake in northern vermont usa we also compared the concentration and fractional abundances of brgdgts in spm and settling particles with those of catchment soils river sediments and lake surface sediments to constrain the relative importance of brgdgts derived from the landscape versus brgdgts produced within the lake itself we find significant differences in concentrations and fractional abundances of brgdgts between soil and river sediment samples from the catchment and lake sediments indicating a mostly autochthonous source for lacustrine brgdgts brgdgt concentrations fluxes and fractional abundances in spm vary over the annual cycle indicating that brgdgts are produced throughout the year and respond to changes within the water column the total annual flux of brgdgts settling through the water column is comparable to the brgdgt accumulation rates in surface sediments indicating that in this lake brgdgts are mostly produced within the water column not in the sediment itself while brgdgts are produced in all seasons within the water column the flux to the sediments is highest during periods of spring and fall isothermal mixing potentially biasing paleotemperature reconstructions towards mixing season temperature because the seasonal timing and frequency of lake mixing varies as a function of regional climate lacustrine brgdgt calibrations should be regional in nature and comprise lakes with similar mixing regimes

contributions of downstream eddy development to the teleconnection between enso and the atmospheric circulation over the north atlantic abstractthe spatiotemporal evolution of various meteorological phenomena associated with el nino southern oscillation enso in the north pacific north american north atlantic sector is examined using both ncep ncar reanalyses and output from a 2000 yr integration of a global coupled climate model particular attention is devoted to the implications of downstream eddy developments on the relationship between enso and the atmospheric circulation over the north atlantic the el nino related persistent events are characterized by a strengthened pacific subtropical jet stream and an equatorward shifted storm track over the north pacific the wave packets that populate the storm tracks travel eastward through downstream development the barotropic forcing of the embedded synoptic scale eddies is conducive to the formation of a flow that resembles the negative phase of the north atlantic oscillation nao the more frequent and higher persistence of those episodes during el nino winters contribute to the prevale

influence of the meridional shifts of the kuroshio and the oyashio extensions on the atmospheric circulation abstract the meridional shifts of the oyashio extension oe and of the kuroshio extension ke as derived from high resolution monthly sea surface temperature sst anomalies in 1982 2008 and historical temperature profiles in 1979 2007 respectively are shown based on lagged regression analysis to significantly influence the large scale atmospheric circulation the signals are independent from the enso teleconnections which were removed by seasonally varying asymmetric regression onto the first three principal components of the tropical pacific sst anomalies the response to the meridional shifts of the oe front is equivalent barotropic and broadly resembles the north pacific oscillation western pacific pattern in a positive phase for a northward frontal displacement the response may reach 35 m at 250 hpa for a typical oe shift a strong sensitivity since the associated sst anomaly is 0 5 k however the amplitude but not the pattern or statistical significance strongly depends on the lag and an

impact of north atlantic freshwater forcing on the pacific meridional overturning circulation under glacial and interglacial conditions abstractthe pacific meridional overturning circulation pmoc is not well known compared to the atlantic meridional overturning circulation amoc due to its absence today however considering pm

a review of molecular organic proxies for examining modern and ancient lacustrine environments molecular organic geochemical proxies are increasingly being utilized to reconstruct past environmental conditions as new tools continue to be discovered and developed to date organic geochemical proxies have been developed mainly for use in marine systems and are widely used in paleoceanography in contrast organic proxies have been less commonly used on lacustrine sedimentary records one reason for this is that the wide range in the physical and chemical properties of lakes complicates application of some organic geochemical proxies in lacustrine settings furthermore in comparison to marine studies presently only a small number of studies have conducted or are currently conducting fundamental research aimed at developing organic geochemical proxies for use in lacustrine settings despite this an increasing number of paleo limnological studies are currently applying organic geochemical techniques to examine present and past environmental conditions in this manuscript we review the use of a number of commonly utilized organic geochemical and isotopic proxies and discuss their potential for environmental reconstruction in quaternary lacustrine deposits

north south precipitation patterns in western north america on interannual to decadal timescales the overall amount of precipitation deposited along the west coast and western cordillera of north america from 258 to 558n varies from year to year and superimposed on this domain average variability are varying north south contrasts on timescales from at least interannual to interdecadal in order to better understand the north south precipitation contrasts their interannual and decadal variations are studied in terms of how much they affect overall precipitation amounts and how they are related to large scale climatic patterns spatial empirical orthogonal functions eofs and spatial moments domain average central latitude and latitudinal spread of zonally averaged precipitation anomalies along the westernmost parts of north america are analyzed and each is correlated with global sea level pressure slp and sea surface temperature series on interannual defined here as 3 7 yr and decadal 7 yr timescales the interannual band considered here corresponds to timescales that are particularly strong in tropical climate variations and thus is expected to contain much p

applicability and calibration of the tex86 paleothermometer in lakes abstract we have conducted a global survey of archaeal glycerol dialkyl glycerol tetraether gdgt lipids in lake sediments in order to develop the tex86 paleotemperature proxy for application in continental systems surface sediments of 46 globally distributed lakes were analyzed for gdgt but isoprenoid gdgt derived from aquatic crenarchaeota were only unambiguously detected in 20 of the 46 lakes analyzed aquatic crenarchaeotal gdgt were detected mainly in sediments from large lakes 4000 km2 and hydrothermal or volcanic lakes suggesting that in some mostly smaller lakes either aquatic crenarchaeota are present at low abundance resulting in sedimentary lipids below levels of detection or they are absent branched gdgt thought to be derived primarily from soil bacteria were identified in all lake sediments analyzed correlation of the tex86 in those lakes with sufficient amounts of putative crenarchaeotal gdgt with annual mean lake temperature is reasonably good r2 0 68 n 20 in order to reduce the influence of soil derived isoprenoid gdgt on the tex86 lake temperatures we have applied a filter based on relative soil derived inputs as determined by the bit branched and isoprenoid tetraether index which results in a calibration relationship with r2 0 86 n 12 and an estimated temperature error of 3 6 c our results suggest that the tex86 should be applied only in lakes with sufficient production of gdgt by aquatic crenarchaeota relative to isoprenoid gdgt derived from soil in the watershed or other aquatic sources

distributions of branched gdgts in a tropical lake system implications for lacustrine application of the mbt cbt paleoproxy branched glycerol dialkyl glycerol tetraether gdgt lipids are abundant and ubiquitous in lake sediments potentially allowing for a paleolimnological application of the so called mbt cbt proxy methylation index of branched tetraethers cyclization ratio of branched tetraethers to investigate the origin and characteristics of these compounds in lacustrine environments we examined the distributions of gdgts in soils river sediments and lake sediments from lake towuti on the island of sulawesi indonesia we found significant differences in the degree of methylation and cyclization expressed by way of the mbt and cbt indices between the soil samples and the aquatic samples suggesting that there may be in situ production of gdgts in the aquatic environment based on these findings we urge caution in the application of the mbt cbt paleoproxy to lake sediments and encourage more rigorous study of these compounds in freshwater environments

characterization of transport and deposition of terrestrial organic matter in the southern north sea using the bit index we have applied a recently introduced proxy the bit branched and isoprenoid tetraether index to determine terrestrial organic matter tom transport from the rivers rhine and meuse and their tributaries to the southern north sea this index is based on crenarchaeol an isoprenoidal glycerol dialkyl glycerol tetraether gdgt predominantly derived from aquatic crenarchaeota and branched gdgts produced by soil bacteria up to 1 6 ng l 1 of branched gdgts were measured in seawater demonstrating the presence of tom in the southern north sea bit indices were inversely correlated with salinity indicating that this tom was recently supplied by rivers the substantial amount of branched gdgts 35 ng l 1 detected in river water and the high branched gdgt concentration measured in the water of a swiss peat bog 5 900 ng l 1 suggest fluvial transport of branched gdgts from peats and soils to the oceans the high crenarchaeol concentration measured in river water 4 4 ng l 1 was probably derived from crenarchaeota living in rivers and organic material from soil and peat the bit index 13c value and c n ratio of surface sediments deposited in the southern north sea were compared to determine tom deposition bit index 0 07 to 0 26 and d13c 220 6 to 222 9 both showed substantial small scale differences in tom deposition in the southern north sea but this pattern was not obvious from the c n ratios a good correlation was found between 13c and branched gdgt concentrations indicating that the absolute gdgt concentrations give additional information to the bit index

carbon isotopic composition of isoprenoid tetraether in surface sediments of lake qinghai and surrounding soils abstract isoprenoid gdgts i gdgts along with their constituent biphytanyl moieties are biomarkers for archaea in order to obtain more information on identifying the carbon source and potential carbon assimilation pathway of archaea in surface sediments of lake qinghai and the surrounding soils the stable carbon isotopic composition of i gdgt derived biphytanes as well as its relationship with 13 c values of total organic carbon toc and dissolved inorganic carbon dic was investigated the 13 c values of i gdgt derived biphytanes ranged from 42 7 to 20 3 for example the values for acyclic biphytanes bp 0 the most abundant varied from 25 0 to 22 1 in offshore sediments 30 5 to 25 4 in surrounding soils and 42 7 to 32 0 in nearshore sediments the wider variation than that of 13 c toc 26 9 to 25 1 in offshore sediments and that in surrounding soils indicated that 13 c values of bp 0 may be a sensitive indicator for examining the depositional environments between terrestrial and lacustrine systems with average 13 c values of 23 6 crenarchaeol derived biphytanes bp cren in offshore sediments were enriched in 13 c ca 3 6 relative to toc in addition the carbon isotopic fractionation between bp cren and dic was 21 3 consistent with that reported for marine thaumarchaeota the enrichment in 13 c relative to toc and the similar carbon isotopic fractionation indicated that thaumarchaeota in offshore sediments of qinghai lake are autotrophic with average 13 c values of 29 2 bp cren in surrounding soils was depleted by 0 9 to 12 8 in 13 c relative to dic the quite large scatter in carbon isotopic fractionation between bp cren and dic indicated that the biomass of soil thaumarchaeota originated from inorganic and organic carbon sources suggesting a mixotrophic lifestyle

the forcing of the pacific decadal oscillation the pacific decadal oscillation pdo defined as the leading empirical orthogonal function of north pacific sea surface temperature anomalies is a widely used index for decadal variability it is shown that the pdo can be recovered from a reconstruction of north pacific sea surface temperature anomalies based on a first order autoregressive model and forcing by variability of the aleutian low el nino southern oscillation enso and oceanic zonal advection anomalies in the kuroshio oyashio extension the latter results from oceanic rossby waves that are forced by north pacific ekman pumping the sst response patterns to these processes are not orthogonal and they determine the spatial characteristics of the pdo the importance of the different forcing processes is frequency dependent at interannual time scales forcing from enso and the aleutian low determines the response in equal parts at decadal time scales zonal advection in the kuroshio oyashio extension enso and anomalies of the aleutian low each account for similar amounts of the pdo variance these results support the hypothesis that the pdo is not a dynamical mode but arises from the superposition of sea surface temperature fluctuations with different dynamical origins

variations of midlatitude transient dynamics associated with enso abstract the winter response of the atmosphere to el nino events in the pacific is studied both from a 14 year integration of the center for ocean land atmosphere gcm using observed ssts from january 1979 to february 1993 and from the corresponding analyses of ecmwf emphasis is put on the shift in the high frequency transients that define the pacific storm track during warm events warm and normal ensembles are defined on the basis of the gcm s diabatic heating field in the tropical pacific which falls in one of two states during the winters of 1982 83 1986 87 and 1991 92 the heating averaged between 6 s and 6 n lies in the range of 100 200 w m 2 all the way across the basin the remaining 10 normal years all show no large tropical diabatic heating anomalies in the mid or eastern pacific the difference between warm and normal ensembles for the mean fields of zonal wind u and height z indicates an eastward and equatorward extension of the midlatitude pacific jet associated with a similar extensio

identification and carbon isotope composition of a novel branched gdgt isomer in lake sediments evidence for lacustrine branched gdgt production branched glycerol dialkyl glycerol tetraethers brgdgts are bacterial membrane lipids that occur ubiquitously in soils and lacustrine sediments and have great potential as proxy indicators for paleotemperature and ph reconstructions initially brgdgts in lakes were thought to originate from soils of the watershed the composition of the lacustrine brgdgt pool however often differs substantially from that in catchment soils complicating the application of the brgdgt paleothermometer to lake sediments this suggests that terrigenous brgdgt signals in lacustrine sedimentary archives may be affected by aquatic in situ production in sediments of a swiss mountain lake we detected a novel hexamethylated brgdgt which elutes between the known 5 and 6 methyl brgdgt isomers during hplc ms analysis this novel isomer accounted for 8 5 of the total brgdgts most remarkably this brgdgt was not detected in soils collected from the catchment of the lake providing circumstantial evidence for an in situ brgdgt source in the lake s water column or sediments isolation of the compound by preparative hplc and subsequent gc ms analysis of the alkyl chains revealed that the novel brgdgt comprises two structural isomers one possesses a 5 13 16 and a 6 13 16 trimethyloctacosanyl moiety and constitutes 84 of the new brgdgt the second contains a 13 16 dimethyloctacosanyl and a 5 13 16 23 tetramethyloctacosanyl moiety the 13c values of both the alkyl chains derived from the novel brgdgt 46 and all other major brgdgts 43 to 44 were significantly lower than those of brgdgt derived alkanes in catchment soils 27 to 28 further attesting to in situ production of brgdgts in the studied lake

fluvial response to debris associated with mass wasting during extreme floods evolution of channels and bottomlands in mountain valleys of the central appalachians is strongly influenced by debris supplied to stream channels from mass wasting during extreme storms the type of change observed varies with basin scale and storm characteristics along channels receiving coarse sediment from debris avalanches or debris flows during hurricane camille in 1969 pure scour occurred in drainage areas less than 1 km 2 and gradients steeper than 0 1 in hurricane camille and in the june 1949 storm mixed erosion and deposition with continuous reworking of the valley floor was observed along streams with drainage areas up to 65 km 2 in basins larger than 100 km 2 valley floor reworking associated with influx of debris during both storms was localized and discontinuous in the south branch potomac river basin in west virginia intense precipitation within a small contributing area generated scores of debris slides and avalanches in june 1949 debris transported by tributaries to main valleys exceeded the competence of the larger channels and formed new bottomland long duration moderate intensity precipitation in november 1985 generated fewer debris avalanches flood peaks associated with a larger contributing area along the main valleys were 80 to 190 larger than in 1949 and caused extensive channel and flood plain erosion including truncation and removal of 1949 deposits at some locations relict debris deposits may have influenced hydraulic conditions and affected patterns of erosion and deposition during the 1985 storm sequential occurrence of extreme storms with different hydrologic characteristics creates a bottomland mosaic of surfaces with varying elevations and textures

calibrating the glycerol dialkyl glycerol tetraether temperature signal in speleothems palaeotemperature proxies based on glycerol dialkyl glycerol tetraethers gdgts lipids have been established for marine and lacustrine environments but there has been relatively little study of their application in speleothems in this study we analyse the gdgt content of 33 speleothem samples from 16 different sites around the globe and test whether proxies based on isoprenoid tetraethers tex86 or branched tetraethers mbt cbt are correlated with measured surface and cave mean annual air temperature mat the results show that the tex86 has a strong relationship with measured temperature r2 0 78 standard error of the estimate 2 3 c when calibrated with surface mat furthermore the mbt cbt also showed a significant relationship with temperature r2 0 73 standard error of the estimate 2 7 c when calibrated with surface mat some issues remain requiring future work in particular the development of a larger calibration sample set with measured cave temperature data and the investigation of controls other than temperature on gdgt distribution but overall the results indicate that gdgt based proxies derived from speleothems may be highly viable new methods for reconstructing continental palaeotemperatures

a refined paleotemperature calibration for new zealand limnic environments using differentiation of branched glycerol dialkyl glycerol tetraether brgdgt sources branched glycerol dialkyl glycerol tetraethers brgdgts were abundant in surface sediments of freshwater lakes and in catchment soils at altitudes from 10 to 2020m in new zealand significant differences in brgdgt compositions between lake sediments and soils indicate sources from separate microbial habitats an expanded modern calibration dataset comprising 33 lakes has enabled a revised calibration function for determining past mean annual air temperature mat from brgdgts in new zealand lake sediments mat degrees c 31 664 x mbtm 16 252 n 30 the function uses a modified methylation index of branched tetraethers mbtm that incorporates brgdgt iii in the numerator to overcome the lower correlation found between our larger dataset and the unmodified mbt which had been used for previous calibrations calibrations combining the cyclization index of branched tetraethers cbt and the mbtm or using only certain brgdgts are possible but have limitations the revised function shows slightly higher correlation with mat r 2 0 75 than previous calibrations which were based on nine sites the refined calibration function is applied to a similar to 16 000 year lake sediment sequence from northern south island new zealand and yields temperature reconstructions that are consistent with independently derived climate trends from the same sequence copyright c 2016 john wiley sons ltd

interdecadal variations in northern hemisphere winter storm track intensity abstract in this paper the interannual variations in the northern hemisphere winter storm tracks have been examined based on 51 winters december january february of ncep ncar reanalysis data the leading empirical orthogonal function eof corresponds to the simultaneous strengthening weakening of both the pacific and atlantic storm tracks interannual and month to month variations in the pacific and atlantic storm tracks are found to be significantly correlated the principal component associated with the leading hemispheric eof exhibits pronounced interdecadal variability there appears to be a transition during the early 1970s from a weak storm track state prior to 1972 73 to a strong storm track state subsequently decadal mean storm track intensity during the 1990s is about 30 stronger than that during the late 1960s and early 1970s the relationship between variations in storm track intensity and low frequency seasonal mean flow anomalies has also been examined it is shown that storm track va

branched glycerol dialkyl glycerol tetraethers in lake sediments can they be used as temperature and ph proxies a series of surface sediments from 82 lakes of variable water depth and size was analyzed for glycerol dialkyl glycerol tetraethers gdgts in order to investigate the potential of the mbt cbt methylation ratio cyclization ratio of branched tetraethers as a continental palaeothermometer in lacustrine environments branched gdgts dominated in most sediments as indicated by the high branched vs isoprenoid tetraether bit values we observed that cbt and mbt varied substantially mean annual air temperature maat reconstructed and ph values were calculated using the cbt and mbt values and the calibration from the global soil data set the mbt cbt inferred temperatures were considerably lower than measured values nevertheless there was a significant correlation between maat reconstructed and maat observed on site although there was still considerable scatter r2 0 47 lacustrine sediments integrate organic remains of organisms in a lake and its drainage basin thereby offering a unique opportunity for calibrating mbt and cbt as small scale variability is averaged out since the source of the branched gdgts in the lake sediments is ambiguous it is not clear whether only temperature and ph in the catchment area are the driving factors therefore even in lake sediments with high concentrations of branched gdgts the straightforward application of mbt cbt as palaeoproxies may be difficult given the uncertainties regarding their source and origin

molecular stratigraphy a new tool for climatic assessment variations in sea surface temperatures over the past 500 000 years are inferred from the relative abundance behaviour of two organic compounds c37 alkenones over the upper 8 metres of a sediment core from the eastern equatorial atlantic this molecular record ascribed to contributions from prymnesiophyte algae correlates well with the variations in the 18 signal for the calcareous skeletons of certain planktonic foraminifera thus providing the first demonstration of a new stratigraphical technique which may be especially valuable where methods based on carbonate 18 fail

the impact of tropical western pacific convection on the north pacific atmospheric circulation during the boreal winter in this study we investigate the impact of atmospheric convection over the western tropical pacific 100 145 e 0 20 n on the boreal winter north pacific atmosphere flow by analyzing national center for environmental prediction reanalysis 1 extended reconstructed sea surface temperature and global precipitation climatology project data the western tropical pacific convection is not only the main energy source driving the local hadley and walker circulations but it also significantly influences north pacific circulation by modifying a mid latitude jet stream through the connection with the local hadley circulation on the one hand this strong convection leads to a northward expansion of local hadley cells simultaneous with a northward movement of the western north pacific jet because of the close correlation between the jet and hadley circulation boundaries on the other hand this strong convection also intensifies tropical pacific walker circulation which reduces the eastern pacific sea surface temperature resembling a la nina state through the enhanced equatorial upwelling the cooling of the eastern tropical pacific has an inter tropical convergence zone located further north thus the local hadley circulation moves northward as a result the jet axis over the eastern north pacific which also corresponds to the boundary of the local hadley circulation moves to higher latitude consequently this northward movement of the jet axis over the north pacific is reflected as a northwest southeast dipole sea level pressure slp pattern the composite analysis of slp over the north pacific against the omega pa s at 500 hpa over the western tropical pacific actually reveals that this northwest southeast dipole structure is attributed to the intensified tropical western pacific convection which pushes the pacific jet to the north finally we also analyzed south pacific for the austral winter as did previously to north pacific and found that the results were consistent

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

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

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

controls on sedimentation in distal margin palaeovalleys in the early tertiary alpine foreland basin south eastern france the influence of palaeodrainage characteristics palaeogeography and tectonic setting are rarely considered as controls on stratigraphic organization in palaeovalley or incised valley systems this study is an examination of the influence of source region vs downstream base level controls on the sedimentary architecture of a set of bedrock confined palaeovalleys developed along the distal margin of the alpine foreland basin in south eastern france three distinct facies associations are observed within the palaeovalley fills fluvial facies association a is mainly dominated by poorly sorted highly disorganized clast to matrix supported cobble to boulder conglomerates that are interpreted as streamflood deposits facies association b comprises mainly yellow siltstones and is interpreted as recording deposition in an estuarine basin environment estuarine marine facies association c comprises interstratified estuarine siltstones and clean well sorted washover sandstones the sedimentary characteristics of the valley fill successions are related to the proximity of depositional sites to sediment source areas palaeovalleys located proximal to structurally controlled basement palaeohighs are entirely dominated by coarse fluvial streamflood deposits in contrast distal palaeovalley segments which are located several kilometres downstream contain successions showing upward transition from coarse fluvial facies into estuarine central basin fines and finally into estuarine marginal marine facies facies distributions suggest that the fluvial deposits form wedge shaped downstream thinning sediment bodies whereas the estuarine deposits form an upstream thinning wedge the vertical stacking of fluvial to estuarine to marginal marine depositional environments records the fluvial aggradation and subsequent transgression of relatively small bedrock confined river valleys which drained a rugged upland terrain facies geometries suggest that a fluvial sediment wedge initially prograded downvalley in response to high bed load sediment yields subsequently palaeovalleys became drowned during the passage of a marine transgression with the establishment of estuarine conditions initial fluvial aggradation and subsequent marine flooding of the palaeovalleys is a consequence of the interaction of high local rates of sediment supply and relative sea level rise driven by flexural subsidence of the basin

oxygen isotope records of holocene climate variability in the pacific northwest abstract oxygen isotope 18o measurements of authigenic carbonate from cleland lake southeastern british columbia paradise lake central british columbia and lime lake eastern washington provide a 9000 year holocene record of precipitation evaporation balance variations in the pacific northwest both cleland lake and paradise lake are small surficially closed basin systems with no active inflows or outflows lime lake is surficially open with a seasonally active overflow water isotope values from cleland and paradise plot along the local evaporation line indicating that precipitation evaporation balance is a strong influence on lake hydrology in contrast lime lake water isotope values plot on the local meteoric water line signifying minimal influence by evaporation to infer past hydrologic balance variations at a high temporal resolution we sampled the cleland paradise and lime lake sediment cores at 1 60 mm intervals 3 33 years per sample on average and measured the isotopic composition of fine grained

effects of temperature ph and nutrient concentration on branched gdgt distributions in east african lakes implications for paleoenvironmental reconstruction branched glycerol dialkyl glycerol tetraethers brgdgts are membrane lipids found in soils and sediments and their relative abundance correlates with temperature and ph enabling them to be used as proxies in reconstructing past climatic and environmental conditions however the potential for other environmental variables such as nutrient concentration to affect brgdgt distributions remains largely unexplored we have examined the influence of a suite of environmental factors including temperature lake water and sediment chemistry and lake morphometry on brgdgt concentration and distributions in the surface sediments of 111 lakes in east africa we found that temperature was the major control on the distributions while the influence of ph was relatively minor water depth also had a minor but statistically significant influence perhaps due to the relationship between lake depth and deep water anoxia water column nutrient concentration did not have a significant effect on the distributions or concentration we further explored the potential for these variables to affect brgdgt temperature reconstruction by examining the correlation between them and the residuals of our brgdgt temperature calibration we found that while the distribution of some cyclized brgdgts may be influenced by ph and other environmental variables they are necessary in brgdgt calibration equations in order to accurately reconstruct temperature likely due to covariation between temperature and other environmental variables while surface water ph correlated with the relative abundance of certain brgdgts caution should be exhibited when using brgdgts as a ph proxy because of systematic calibration errors

the southern oscillation part i global associations with pressure and temperature in northern winter abstract we describe the global correlations between a measure of the southern oscillation and sea level pressure and surface air temperature in the northern winter the stability of these correlations were tested on the northern hemisphere for an 80 year period and it turned out that most stable correlation coefficients were found over india the north pacific ocean the rocky mountains and the central and western north atlantic ocean on the southern hemisphere most records are too short for a similar test but the following may tentatively be said about the southern oscillation in middle and high southern latitudes when pressure is low in lower latitudes over the south pacific ocean it tends to be high at higher latitudes of that ocean high over east antarctica and low in the belt of westerlies in the indian and south atlantic oceans in the zonal average on both hemispheres the pressure gradients in this extreme of the oscillation tend to be steeper at lower latitudes and flatter at higher latitud

sea surface temperature anomalies planetary waves and air sea feedback in the middle latitudes the mechanisms that contribute to the generation and damping of large scale mid latitude sea surface temperature sst anomalies are discussed the sst anomalies reflect primarily the response of the upper ocean to the changes in air sea fluxes that are associated with daily weather fluctuations heat flux forcing is dominant in the lower middle latitudes while wind driven entrainment may be most effective in the high latitudes advection by anomalous ekman current is generally less important and ekman pumping is negligible the sst anomalies decay in part because of entrainment effects associated with mixed layer deepening and oceanic mixing and in part because of heat exchanges with the atmosphere the three approaches commonly used to model the evolution of sst anomalies are reviewed case studies based on monthly or seasonal anomaly maps of the large scale sst and atmospheric anomalies numerical simulations with one dimensional mixed layer models and stochastic forcing models we stress the similarities in the different approaches and discuss their main advantages and limitations the response of the atmosphere to mid latitude sst anomalies is considered first we discuss the poorly known relationship between sst anomalies and diabatic heating using a crude assumption for the air sea coupling we consider a two layer quasi geostrophic channel model and discuss the stationary wave response to sst anomaly forcing and the resulting air sea feedback it is found that the back interaction of the sst anomalies onto the atmosphere causes a weak sst anomaly damping at large scales and a strong one at small scales the air sea coupling should also act as an eastward propagator for the sst anomalies the response of more realistic linear wave models to prescribed diabatic heating is then reviewed and it is suggested that realistic mid latitude sst anomalies have a weak influence on the atmospheric circulation corresponding to changes in the geopotential height of 10 30 m at most this order of magnitude is consistent with the results of general circulation model experiments and with the limited climate predictability associated with mid latitude sst anomalies

evaluation of glycerol dialkyl glycerol tetraether proxies for reconstruction of the paleo environment on the qinghai tibetan plateau the uplift of the qinghai tibetan plateau has a great effect on local and global climate changes here we report the late holocene climate change in the northern plateau by using a 3490 year sediment core record from kusai lake glycerol dialkyl glycerol tetraethers gdgts collected from the core were examined in combination with other paleo environmental proxies the reconstructed mean annual air temperatures maat using branched gdgt membrane lipids of certain bacteria proxies are higher than the measured maat but much closer to measured summer air temperatures suggesting a possibility of a bias of the reconstructed maat towards summer temperatures the ph values derived from a branched gdgt proxy show a negative correlation with toc a lake productivity indicator in arid regions furthermore both cbt ph and toc show temporal cyclic changes which suggest that the branched gdgt derived ph index may be useful in reconstructing paleo ph values in a lacustrine system lastly the composition of isoprenoid gdgts membrane lipids of archaea shows a major shift around 1400 bp which is in line with a large increase in sediment soluble salts at this time but lags behind the onset of salt mineral precipitation by 600 yr suggesting that change in archaeal community composition and salt mineral precipitation may require different threshold values of salinity the results of this study demonstrate that useful paleo climatic and paleo environmental information can be extracted from the gdgts preserved in lake sediments

effects of forest cover topography and sampling extent on the measured density of shallow translational landslides 1 we use regionally available digital elevation models and land cover data calibrated with ground and photo based landslide inventories to produce spatially distributed estimates of shallow translational landslide density number unit area to discern effects of land use we focus on resolving landslide density relationships with forest cover we account for topographic variability between sites and landslide detection bias in air photo mapping even so for sites in the oregon coast range we find great variability in the ratios of landslide density in forest classes among sites we present strategies for subsampling available data to quantify this variability for these data we find that older forests when sampled over tens of square kilometers commonly exhibited the highest landslide densities but over hundreds of square kilometers always exhibited the lowest densities averaging 30 of that in recently harvested areas and 79 of that in younger managed forests

insights into continental temperatures in the northwestern black sea area during the last glacial period using branched tetraether lipids abstract in the continental realm continuous quantitative temperature reconstructions spanning the last glacial are rare especially in central and eastern europe here we provide a reconstruction from the northwestern black sea catchment spanning 40 to 9 ka bp from a study of the relative distribution of branched glycerol dialkyl glycerol tetraethers brgdgts in black sea lacustrine sediments first the origins of brgdgts are discussed the comparison of geochemical proxies from the same core supports a dominant terrestrial origin for brgdgts during the last glacial and a strong decrease in the soil derived brgdgt proportion toward the holocene since the lowering of soil vs lacustrine derived brgdgts is prone to bias the temperature signal that is reconstructed using a soil calibration a correction for in situ production is applied the corrected signal is compared to independent discrete temperature records from the study area the brgdgt temperature relative evolution reconstructed in this work provides additional insight regarding millennial scale climate variability in central and eastern europe notably the imprints of heinrich event cold spells and lateglacial climatic oscillations are consistent with other regional paleorecords from the northern hemisphere

eocene vegetation patterns reconstructed from plant diversity a global perspective abstract eocene vegetation patterns and continental temperatures are reconstructed from the palaeobotanical record on a global scale a total of 100 macrofloras and 45 microfloras compiled from published sources is analysed studying diversities of plant functional types and phytosociological types the spatial patterns obtained from the diversity of plant functional types reflect the distribution of major eocene ecosystems as shown by the analysis different forest associations were most important with trees reaching over 50 of the total diversity in 92 of the localities using a phytosociological classification scheme employing the ecological requirements of the nearest living relatives of fossil taxa the single floras are analysed by multivariate statistical methods as a result the eocene sites are allocated to 7 different groups which can be interpreted in terms of eocene vegetation units the distribution of these units is shown in palaeogeographical maps it is shown that in the eocene major vegetation units were zonally arranged most of the floras located north and south of 15 latitude are classified as extra tropical there is evidence for seasonally drier climate conditions in some regions but no indication for xerophytic vegetation types the vegetation of the mid latitudes is characterized by a very high diversity of evergreen angiosperm woods especially in the tethyan realm the high northern latitudes were covered by temperate deciduous and mixed deciduous vegetation the reconstructed vegetational patterns are well in accordance with results obtained from the analysis of various proxy data indicating the existence of very warm high latitudes and a shallow latitudinal temperature gradient during the eocene

isoprenoid and branched gdgt based proxies for surface sediments from marine fjord and lake environments in chile abstract proxies based on glycerol dialkyl glycerol tetraether gdgt lipids from archaea isoprenoid gdgts and bacteria branched br gdgts in 33 surface sediments from marine fjord and lake systems between 25 s and 50 s in chile were analyzed the regional texh86 calibration obtained from the marine and fjord sediments and mean annual surface temperature t 59 6 texh86 33 0 r2 0 9 n 23 is statistically identical to the global ocean calibration based on suspended particulate material in terms of slope but not in terms of intercept the regional surface and subsurface texh86 calibrations were statistically different from the existing global ocean core top calibrations the tex86 calibration model based on most of the relatively large lakes studied here t 50 7 tex86 11 8 r2 0 9 n 5 is statistically identical to the global lake calibration the relatively high tex86 values from smaller lakes suggested an additional source for isoprenoid gdgts likely terrestrial or aquatic methanogenic archaea application of the soil calibrated mbt cbt methylation and cyclization of br gdgts respectively temperature proxy to the marine and fjord sediments resulted in an overestimation of continental mean annual air temperature maat suggesting in situ production of certain br gdgts in the water column or surface sediment for the lakes mbt cbt based surface air temperature estimates were 3 6 c below maat however temperature estimates from the lake specific mbt cbt global calibration were in good agreement with mean annual surface temperature for all the lakes the results highlight the need for testing local vs global calibrations of gdgt based proxies before their application for palaeoenvironmental reconstruction