transfer of basal sliding variations to the surface of a linearly viscous glacier on etudie pour une plaque a faces paralleles d epaisseur h et de viscosite lineaire l effet en surface des fluctuations de la vitesse de derapage

seawater ph pco2 and co2 3 variations in the caribbean sea over the last 130 kyr a boron isotope and b ca study of planktic foraminifera abstract here a new analytical methodology is described for measuring the isotopic composition of boron in foraminifera using multicollector inductively coupled plasma mass spectrometry mc icpms this new approach is fast 10 samples analysed in duplicate per analytical session and accurate to better than 0 25 at 95 confidence with acceptable sample size requirements 1 3 mg of carbonate a core top calibration of several common planktic and two benthic species from geographically widespread localities shows a very close agreement between the isotopic composition measured by mc icpms and the isotopic composition of b oh 4 in seawater as predicted using the recently measured isotopic equilibrium factor of 1 0272 at the depth of habitat a down core and core top investigation of boron concentration b ca ratio shows that the partition coefficient is influenced by co2 3 complicating the application of this proxy nevertheless it is demonstrated that these two proxies can be used to fully constrain the carbonate system of surface water in the caribbean sea odp site 999a over the last 130 kyr this reconstruction shows that during much of the holocene and the last interglacial period surface water at site 999a was in equilibrium with the atmosphere with respect to co2 during the intervening colder periods although the surface water pco2 was lower than the holocene it was a minor to significant source of co2 to the atmosphere possibly due to either an expansion of the eastern equatorial atlantic upwelling zone or a more local expansion of coastal upwelling in the southern caribbean such reorganisation of the oceanic carbonate system in favour of a larger source of co2 to the atmosphere from the equatorial ocean may require mechanisms responsible for lowering atmospheric co2 during glacial periods to be more efficient than previously supposed

modern distribution patterns of planktonic foraminifera in the south china sea and western pacific a new transfer technique to estimate regional sea surface temperatures abstract we present 30 new planktonic foraminiferal census data of surface sediment samples from the south china sea recovered between 630 and 2883 m water depth these new data together with the 131 earlier published data sets from the western pacific are used for calibrating the simmax 28 transfer function to estimate past sea surface temperatures this regional simmax method offers a slightly better understanding of the marginal sea conditions of the south china sea than the linear transfer function fp 12e which is based only on open ocean data however both methods are biased toward the tropical temperature regime because of the very limited data from temperate to subpolar regions the simmax formula was applied to sediment core 17940 from the northeastern south china sea with sedimentation rates of 20 80 cm ka results revealed nearly unchanged summer temperatures around 28 c for the last 30 ky while winter temperatures varied between 19 5 c in the last glacial maximum and 26 c during the holocene during termination 1a the winter estimates show a younger dryas cooling by 3 c subsequent to a temperature optimum of 24 c during the bolling allerod estimates of winter temperature differences between 0 and 100 m water depth document the seasonal variations in the thickness of the mixed layer and provide a new proxy for estimating past changes in the strength of the winter monsoon

concentrated pulsed axial glacier flow structural glaciological evidence from kviarjokull in se iceland a detailed structural glaciological study carried out on kviarjokull in se iceland reveals that recent flow within this maritime glacier is concentrated within a narrow corridor located along its central axis this active corridor is responsible for feeding ice from the accumulation zone on the south eastern side of oraefajokull to the lower reaches of the glacier and resulted in a c 200 m advance during the winter of 2013 2014 and the formation of a push moraine the corridor comprises a series of lobes linked by a laterally continuous zone of highly fractured ice characterised by prominent flow parallel crevasses separated by shear zones the lobes form highly crevassed topographic highs on the glacier surface and occur immediately down ice of marked constrictions caused by prominent bedrock outcrops located on the northern side of the glacier close to the frontal margin of kviarjokull the southern side of the glacier is relatively smooth and pock marked by a number of large moulins the boundary between this slow moving ice and the active corridor is marked by a number of ice flow parallel strike slip faults and a prominent dextral shear zone which resulted in the clockwise rotation and dissection of an ice cored esker exposed on the glacier surface it is suggested that this concentrated style of glacier flow identified within kviarjokull has affinities with the individual flow units which operate within pulsing or surging glaciers

response of planktonic foraminifera to glacial cycles mid pleistocene change in the southern south china sea a high resolution study 2 ka of planktonic foraminifers in 997 samples from odp site 1143 9821 72vn 113817 11ve water depth 2772 m in the southern south china sea scs reveals faunal response to glacial cycles in the last 2 1 ma most distinctive is the contrasting variations in the abundance of two tropical subtropical species that exhibit similar resistance to dissolution in modern oceans the relative and absolute abundances of globorotalia menardii are high in interglacials and low in glacials and covary with d 18 o fluctuations over the studied interval pulleniatina obliquiloculata however follow oxygen isotopes only before the mid pleistocene revolution mpr showing high abundances during glacials and low during interglacials after 850 ka three abundance maxima of p obliquiloculata are observed corresponding to three major glacial episodes marine isotope stages mis 2 12 and 16 respectively this change in abundance patterns of p obliquiloculata appears to be unique to the southern scs as in late pleistocene records from other western pacific regions including the okinawa trough and the northern scs all show co varying patterns with d 18 oa sg menardii does cross spectral analyses performed between percentages of globorotalia menardii and d 18 o records show high coherency at 41 ka obliquity and then at 100 ka eccentricity bands we suggest that the high abundances of g menardii during interglacials in the past 2 1 ma reflect warmer temperatures percentages of pulleniatina obliquiloculata vs oxygen isotope records show quite large phase difference at 41 ka obliquity band before the mpr as a contrast there are negligible phase differences in the vicinity of 100 and 41 ka after the mpr which means reverse trend between percentages of p obliquiloculata and d 18 o fluctuations the differences of p obliquiloculata from g menardii in abundance and orbital forcings are interpreted as resulting from a profound change in the regional upper ocean structure during the mpr time probably relating to a final glacial cut off of the southern scs from the indian water at 850 ka and to higher salinity during glacial times after 850 ka we speculate that this change is related to the decreased connection between the pacific and indian ocean d 2004 elsevier b v all rights reserved

using rare earth elements to monitor sediment sources from a miniature model of a small watershed in the three gorges area of china abstract understanding soil erosion processes at different landscape positions is important in order to predict and control watershed soil losses rare earth elements rees can be used to trace eroded soil sources but their efficacy may be soil dependent we constructed a miniature watershed model of a small watershed located in the three gorges area of china and used oxides of eight rees to trace the erosion of a purple soil the miniature watershed was divided into eight regions containing a different landform type as a potential sediment source a different ree was applied in each region redistributions of the rees under three successive simulated rainfall events with intensities of 1 0 1 5 or 2 0 mm min 1 were examined the percentage contribution from each region to the total soil loss from the watershed fluctuated relative to landform type during the three rainstorms contributions from the lower main gully decreased before stabilizing while those from the upper main gully increased before decreasing and those from other sources all increased before stabilizing overall the contribution of the gully system comprising main and branch gullies was greater than that of the slopes contributions from the gully system tended to decrease with increases in rainfall intensity and rainstorm duration while those from the slopes increased a comparison of the calculated and actual soil loss masses indicated that the accuracy of the ree tracing method was less for the coarse textured purple soil than those previously found for fine textured soils the increased errors likely due to the assumption used in the calculation that there is no particle size selectivity during erosion needs to be addressed this pilot study provided a technical reference for the use of rees in monitoring sediment sources from a natural watershed and a theoretical basis for soil conservation in the three gorges area

living planktic foraminifera in the central tropical pacific ocean articulating the equatorial cold tongue during la nina 1992 abstract in cold tongue conditions of august september 1992 living planktic foraminifera in the equatorial pacific tracked circulation featuresand phytoplankton abundance an equatorial assemblage associated with the cool and productive equatorial region contained g bulloides a species often associated with tropical coastal upwelling as well as the nonspinose herbivores g menardii g glutinata p obliquiloculata and n dutertrei previously associated with equatorial environments within surface subtropical waters poleward of 5 n and 5 s g sacculifer g ruber and g conglobatus dominated foraminiferal populations these species have successfully adapted to oligotrophic conditions by exploiting dinoflagellate endosymbionts high standing stocks of these species in equatorial regions suggest that they can also thrive within equatorial light levels and temperatures a deep southern assemblage dominated by nonspinose g conglomerata and g tumida and spinose g aequilateralis had a subsurface maximum at 80 200 m outside of active upwelling and outcropped to the surface at 1 s from el nino to cold tongue conditions equatorial fauna reflected higher primary productivity and an increase in the role of advection by the south equatorial current

applicability of rare earth element oxides as a sediment tracer for coarse textured soils a leaching experiment using a mixture of five ree oxides and gravelly sandy loam soils was conducted to examine the applicability of the ree oxides as a sediment tracer for coarse textured soils the experiment showed little leaching of the oxides and an enrichment of various size classes of soil particles with the oxides which reflected the strong binding capability of the ree oxides with the gravelly sandy loam soils it also showed that the ree oxides preferentially bound with small size classes of soil particles the preferential binding of the ree oxides with fine materials will cause the overestimation of the soil loss from a given area i e tagged with a given ree if aggregates are broken down during sediment transport and clay materials are preferentially delivered and if the soil loss is computed by analyzing the ree concentrations in the whole sediment to address the non uniform binding issue the method based on measuring the ree concentrations for four particle size groups was tested the potential error of the method was evaluated by comparing the soil loss that would be computed in the case that the particle size distribution was shifted to the smallest particle size class within a particle size group and in the case that no sediment sorting occurred the result showed that the method would produce a potential error of approximately 4 in the estimation of the total soil loss when sediment sorting occurred the non uniform binding of the oxides does not preclude the use of the ree oxides on the coarse textured soils in the presence of non uniform binding of the oxides but adjustments in the technique are required for an accurate estimation of soil loss using the ree technique

western equatorial pacific planktic foraminiferal fluxes and assemblages during a la nina year 1999 abstract a correlation between foraminiferal community dynamics and environmental conditions may provide a basis for establishing paleoclimatic proxies we studied planktic foraminiferal shell fluxes and assemblages in samples collected in three time series sediment trap deployments in the western equatorial pacific under la nina conditions from january to november 1999 eleven species contributed about 90 of the total flux in all traps two sites mt1 mt3 in the western pacific warm pool region wpwp were characterized by common occurrences of the species globigerinoides ruber globigerinoides sacculifer globigerinoides tenellus and neogloboquadrina dutertrei site mt5 farther to the east in the equatorial upwelling region had common occurrences of globigerina bulloides globigerinita glutinata and pulleniatina obliquiloculata very high abundances of g bulloides and g glutinata at mt5 indicate that equatorial upwelling eu occurred during the 1999 la nina the two western sites have similar assemblage compositions but mt1 135 e has the highest fluxes up to 3800 tests m 2 day 1 whereas mt3 145 e has fluxes below 2200 tests m 2 day 1 relatively high fluxes up to 3000 tests m 2 day 1 occur at site mt5 176 e where upwelling occurred the differences in faunal composition in the wpwp and eu might be attributable to differences in the way in which nutrients are supplied to the phytoplankton large amounts of suspended material are supplied to the wpwp by advection of waters passing through the coastal region of an archipelago whereas upwelling of nutrient rich waters enhances primary production in the eu at the westernmost site in the wpwp a peak in the g bulloides flux coincided with southward flow of the new guinea coastal current ngcc in late february but the highest g ruber flux coincided with northward flow of this current in late may thus the differences in species dominance at this location may be caused by monsoon driven variability in the flow direction of the nggc

planktic foraminiferal sedimentation and the marine calcite budget 1 the vertical flux and sedimentation rate of planktic foraminiferal tests are quantified and a global planktic foraminiferal cac0 3 budget is presented test and calcite flux rates are calculated according to the distribution of species obtained from multinet and sediment trap samples modern planktic foraminiferal population dynamics are discussed as a prerequisite for the quantification of the calcite budget highlighting the importance of ecological autecological e g reproduction and biogeochemical conditions that determine the presence or absence of species to complete the open marine particulate caco 3 inventory the contribution of coccolithophores pteropods and calcareous dinophytes is discussed based on the studied regions the global planktic foraminiferal calcite flux rate at 100 m depth amounts to 1 3 3 2 gt yr 1 equivalent to 23 56 of the total open marine caco 3 flux the preservation of tests varies on a regional and temporal scale and is affected by local hydrography and dissolution during most of the year off peak periods many tests dissolve above 700 m water depth while settling through the water column with on average only 1 3 of the initially exported caco 3 reaching the deep seafloor pulsed flux events mass dumps of fast settling particles yield a major contribution of tests to the formation of deep sea sediments on average 25 of the initially produced planktic foraminiferal test cac0 3 settles on the seafloor the total planktic foraminiferal contribution of caco 3 to global surface sediments amounts to 0 36 0 88 gt yr 1 32 80 of the total deep marine calcite budget

astronomically tuned plio pleistocene benthic δ 18 o record from south china sea and atlantic pacific comparison based on benthic foraminiferal n 18 o from odp site 1143 a 5 myr astronomical timescale for the west pacific plio pleistocene was established using an automatic orbital tuning method the tuned brunhes matuyama paleomagnetic polarity reversal age agrees well with the previously published age of 0 78 ma the tuned ages for several planktonic foraminifer bio events also agree well with published dates and new ages for some other bio events in the south china sea were also estimated the benthic n 18 o from site 1143 is highly coherent with the earth s orbit etp both at the obliquity and precession bands for the last 5 myr and at the eccentricity band for the last 2 myr in general the 41 kyr cycle was dominant through the plio pleistocene although the 23 kyr cycle was also very strong the 100 kyr cycle became dominant only during the last 1 myr a comparison of the benthic n 18 o between the atlantic odp 659 and the east and west pacific 846 and 1143 reveals that the atlantic pacific benthic oxygen isotope difference ratio vn 18 oatlpac displays an increasing trend in three time intervals 3 6 2 7 ma 2 7 2 1 ma and 1 5 0 25 ma each of the intervals begins with a rapid negative shift in vn 18 oatlpac followed by a long period with an increasing trend corresponding to the growth of the northern hemisphere ice sheet this means that all three intervals of ice sheet growth in the northern hemisphere were accompanied at the beginning by a rapid relative warming of deep water in the atlantic as compared to that of the pacific followed by its gradual relative cooling this general trend superimposed on the frequent fluctuations with glacial cycles should yield insights into the processes leading to the boreal glaciation cross spectral analyses of the vn 18 oatlpac with the earth s orbit suggests that after the initiation of northern hemisphere glaciation at about 2 5 ma obliquity rather than precession had become the dominant force controlling the vertical structure or thermohaline circulation in the paleo ocean a 2002 elsevier science b v all rights reserved

the effect of the subglacial water pressure on the sliding velocity of a glacier in an idealized numerical model in order to interpret observed short term variations of the sliding velocity of a glacier the effect of a variable subglacial water pressure on the sliding velocity has been studied using an idealized numerical model in particular the transient stages of growing or shrinking water filled cavities at the ice bedrock interface were analysed it was found that the sliding velocity was larger when cavities were growing than when they had reached the steady state size for a given water pressure the smallest sliding velocities occurred while cavities were shrinking when cavitation is substantial a small drop of water pressure below the steady state value e g by 0 5 bar can temporarily cause backward sliding a limiting water pressure at which sliding becomes unstable is derived the consequences of more realistic assumptions than those of the model are discussed

discharges of turbid water during mini surges of variegated glacier alaska u s a discharges of water sediment and dissolved impurities from variegated glacier ala ska were monitored in the early summers of 1980 and 1981 during the occurrence of mini surg es sea sonal trends weat her related eve nts and diurnal variat ions similar to behavior of other temperat e gl acier streams were found the prin cipal effect in the stream associated with mini surge occurrence was a brief discharge of extremely turbi d water the turbidity is assumed to be introduced into the basal hydraulic system by initiation of the fast motion of a mini surge at a time and locat ion on the upper glacier known from oth er meas ure ments the mean water velocity in the hydraulic system over the int erven ing distance is thereby determined 0 3 m s i the mean water velocity together with the water discharge 16 m3 s 1 at the terminus places con straints on the distribution of water velocity u and total cros s sectional area at of the flow paths along the gl acier base this leads to the con clusion that within the zone of mini surge occurrence in its unpe rturbed state u is about 0 1 m s 1 or possibly less at is about 10 2 m2 or possibly more and it must be divided into a very large number of small passag eways be blocked by constrict ions or both the total water cro ss se ction corresponds to a layer 0 1 2 m thick when spr ead unifo rmly over the glacier width the water velocity is clos e to or less than the propa gation velo city of the mini s urges bet ween the zone affected by mini surges and the stream a dyna mically less active lower section of the glacier is proba bly underlain by a small number of conduits in which the water velocity may be very high 2 m s i water di scharge follo wing the mini surges puts an upper limit on water storage changes ass ociated with the anomalous ice motion

ba ca in neogloboquadrina pachyderma as an indicator of deglacial meltwater discharge into the western arctic ocean 1 down core samples of the planktonic foraminifer neogloboquadrina pachyderma sinistral from the mendeleyev ridge in the western arctic ocean have been analyzed for ba ca and 18o the apparent distribution coefficient for n pachyderma sin is estimated at dba 0 22 0 02 a meltwater event is identified at around 11 8 14c kyr bp and is coincident with elevated ba ca ratios the barium enrichment is believed to be the result of enhanced weathering and erosion following glaciation additionally barium may have desorbed from shelf sediments as sea level rose changes in ba ca correlate with the retreat of the laurentide ice sheet and the evolution of the mackenzie river drainage basin therefore maximum ba ca in arctic surface waters at 11 8 ka may be indicative of an increase in the export of freshwater from the arctic to the north atlantic potentially contributing to the onset of the younger dryas this work suggests that ba ca in planktonic foraminifera may be a useful indicator of the timing and processes associated with deglaciation

stress gradient coupling in glacier flow i longitudinal averaging of the influence of ice thickness and surface slope for a glacier flowing over a bed of longitudinally varying slope the influence of longitudinal stress gradients on the flow is analyzed by means of a longitudinal flow coupling equation derived from the vertically cross sectionally integrated longitudinal stress equilibrium equation by an extension of an approach originally developed by budd 1968 linearization of the flow coupling equation by treating the flow velocity u vertically averaged ice thickness h and surface slope in terms of small deviations u h and a from overall average datum values u 0 h 0 and 0 results in a differential equation that can be solved by green s function methods giving u x as a function of h x and x x being the longitudinal coordinate the result has the form of a longitudinal averaging integral of the influence of local h x and x on the flow u x u x u0 2l l 0 ln n nh n l exp x x l dx where the integration is over the length l of the glacier the operator specified deviations from the datum state and the term on which it operates which is a function of the integration variable x represents the influence of local h x x and channel shape factor x at longitudinal coordinate x on the flow u at coordinate x the influence being weighted by the influence transfer function exp x x l in the integral the quantity l that appears as the scale length in the exponential weighting function is called the longitudinal coupling length it is determined by rheological parameters via the relationship l 2h n n 3n where n is the flowlaw exponent n the effective longitudinal viscosity and n the effective shear viscosity of the ice profile n is an average of the local effective viscosity n over the ice cross section and n 1 is an average of n 1 that gives strongly increased weight to values near the base theoretically the coupling length l is generally in the range one to three times the ice thickness for valley glaciers and four to ten times for ice sheets for a glacier in surge it is even longer l 12h it is distinctly longer for non linear n 3 than for linear rheology so that the flow coupling effects of longitudinal stress gradients are markedly greater for non linear flow the averaging integral indicates that the longitudinal variations in flow that occur under the influence of sinusoidal longitudinal variations in h or with wavelength are attenuated by the factor 1 1 2 l 2 relative to what they would be without longitudinal coupling the short intermediate and long scales of glacier motion raymond 1980 over which the longitudinal flow variations are strongly partially and little attenuated are for 2l 2l 20l and 20l for practical glacier flow calculations the exponential weighting function can be approximated by a symmetrical triangular averaging window of length 4l called the longitudinal averaging length the traditional rectangular window is a poor approximation because of the exponential weighting the local surface slope has an appreciable though muted effect on the local flow which is clearly seen in field examples contrary to what would result from a rectangular averaging window tested with field data for variegated glacier alaska and blue glacier washington the longitudinal averaging theory is able to account semi quantitatively for the observed longitudinal variations in flow of these glaciers and for the representation of flow in terms of effective surface slope values exceptions occur where the flow is augmented by large contributions from basal sliding in the ice fall and terminal zone of blue glacier and in the reach of surge initiation in variegated glacier the averaging length 4l that gives the best agreement between calculated and observed flow pattern is 2 5 km for variegated glacier and 1 8 km for blue glacier corresponding to l h 2 in both cases if l varies with x but not too rapidly the exponential weighting function remains a fairly good approximation to the exact green s function of the differential equation for longitudinal flow coupling in this approximation l in the averaging integral is l x but is not a function of x effects of longitudinal variation of l are probably important near the glacier terminus and head and near ice falls the longitudinal averaging formulation can also be used to express the local basal shear stress in terms of longitudinal variations in the local stope stress with the mediation of longitudinal stress gradients

effects of seawater carbonate ion concentration and temperature on shell u mg and sr in cultured planktonic foraminifera we investigate the sensitivity of u ca mg ca and sr ca to changes in seawater co3 and temperature in calcite produced by the two planktonic foraminifera species orbulina universa and globige rina bulloides in laboratory culture experiments our results demonstrate that at constant temperature u ca in o universa decreases by 25 7 per 100 mol co3 k g 1 as seawater co3 increases from 110 to 470 mol kg 1 results from g bulloides suggest a similar relationship but u ca is consistently offset by 40 at the same environmental co3 in o universa u ca is insensitive to temperature between 15 c and 25 c applying the o universa relationship to three u ca records from a related species globigerinoides sacculifer we estimate that caribbean and tropical atlantic co3 was 110 70 mol kg 1 and 80 40 mol kg 1 higher respectively during the last glacial period relative to the holocene this result is consistent with estimates of the glacial interglacial change in surface water co3 based on both modeling and on boron isotope ph estimates in settings where the addition of u by diagenetic processes is not a factor down core records of foraminiferal u ca have potential to provide information about changes in the ocean s carbonate concentration below ambient ph ph 8 2 mg ca decreased by 7 5 o universa t o 16 6 g bulloides per 0 1 unit increase in ph above ambient ph the change in mg ca was not significant for either species this result suggests that mg ca based paleotemperature estimates for the quaternary during which surface ocean ph has been at or above modern levels have not been biased by variations in surface water ph sr ca increased linearly by 1 6 0 4 per 0 1 unit increase in ph shell mg ca increased exponentially with temperature in o universa where mg ca 0 85 exp 0 096 t whereas the change in sr ca with temperature was within the reproducibility of replicate measurements copyright 2004 elsevier ltd

preliminary experiments to assess the effectiveness of magnetite powder as an erosion tracer on the loess plateau abstract soil water erosion monitoring is essential for long term soil conservation and ecological restoration on the loess plateau region of china traditional approaches such as runoff plots and water weirs in a watershed provide reliable spatially averaged soil erosion data but cannot validate process based erosion prediction models for dynamic soil erosion evaluation erosion tracer techniques are capable of quantitatively determining spatial distribution of soil erosion ideal tracers are expected to provide highly contrasting values compared with background ones and be analyzed efficiently and acquired cost effectively in this laboratory study magnetite powder was selected as an erosion tracer to test the tracer was implanted into loessial soils from the loess plateau using a wet soil tracer mixing procedure the effectiveness of magnetite powder as an erosion tracer was evaluated in aspects of basic magnetic features between the tracer and soils distribution under different soil aggregate sizes mobility along soil profiles and detachment of tracer labeled loessial soils by shallow surface flow along a slope results showed that magnetite powder was bound tightly to loessial soil aggregates with no noticeable vertical mobility under long term leaching conditions and almost synchronous detachment with the eroded soils furthermore the tracer is an inexpensive tracer approximately 0 08 us kg 1 which has higher magnetic susceptibility over two or three orders of magnitude than ordinary soils and high sensitivity of analysis

modelling ice bed coupling during a glacier speed up event haut glacier d arolla switzerland fischer u h mair d kavanaugh j l willis i nienow p hubbard b 2011 modelling ice bed coupling during a glacier speed up event haut glacier d arolla switzerland hydrological processes 2599 1361 1372

deep sea carbonate preservation in the western philippine sea over the past 1ma abstract in this paper we present a continuous record of calcium carbonate caco 3 content that covers the last 1 ma from core md06 3050 15 57 0943 n 124 46 7747 e water depth 2967 m which was collected in the western philippine sea wps the caco 3 content in this study core is characterized by maxima during deglaciations and minima during the onsets of glacial periods and generally shows pacific style patterns with relatively high and low values during glacial and interglacial periods respectively proxies of dissolution and primary productivity pp the caco 3 content and the oxygen isotope record from this core are compared throughout the 1 ma study interval to improve our understanding of the mechanisms that affected carbonate preservation and dissolution at this site the planktonic foraminifera shell fragmentation ratio shell fragment is used as a dissolution proxy in this study the shell fragment data from md06 3050 provide evidence of preservation maxima during most of the deglaciations whereas intense dissolution is recorded at the onsets of glacial periods within the past 1 ma the variations in shell fragments are similar to those seen in the caco 3 content which demonstrates that the bulk caco 3 content patterns were controlled by dissolution in deep seawater the primary productivity from the coccolith record shows limited similarity with the caco 3 content on glacial interglacial time scales since 1 ma which suggests that pp played a negligible role in the glacial interglacial caco 3 cycle however a bloom of the coccolithophores geophyrocapsa caribbeanica that extended from mis 9 to mis 12 likely contributed to the increased caco 3 content observed during the mid brunhes interval mbe over the glacial interglacial fluctuations therefore the caco 3 content should be used as a dissolution proxy with caution during the mbe in the tropical pacific especially for water depths that are shallower than the carbonate lysocline

biological and chemical characteristics of high chlorophyll low temperature water observed near the sulu archipelago abstract according to ocean color remote sensing data a low phytoplankton biomass exists in the central parts of the sulu and celebes seas whereas higher concentrations of chlorophyll a are observed in the waters near the sulu archipelago which separates these water bodies these high chlorophyll a waters have lower temperatures than those of surrounding waters indicating vertical mixing of nutrient rich subsurface water that is attributable to the topographical features of the sulu ridge differences in photosynthetic parameters primary productivity and the phytoplankton community structure between the high chlorophyll area near the sulu archipelago and the oligotrophic basin area in the philippine sulu and celebes seas were investigated in november 2002 during the r v hakuho maru kh 02 4 cruise entrainment of subsurface water and vertical mixing by intense tidal flow from the sulu archipelago to the celebes sea created a low temperature high nutrient condition at the southeastern edge of the sulu ridge chlorophyll a concentrations greater than 2 g l 1 were observed at stations 5 15 km offshore at the edge of the sulu ridge this high chlorophyll tongue in the celebes sea showed high primary productivity it was 1 6 18 times higher than those measured in oligotrophic central basin regions of the philippine sulu and celebes seas microscopic observation of these high chlorophyll waters showed the dominance of chain forming large centric diatoms extension of high chlorophyll waters was not observed at the sulu sea side where the surface water salinity was lower than in the celebes sea and consequently prevented intrusion of the celebes sea water into the surface layer occasional extensions of productive chlorophyll rich surface water from the archipelagic zone to the surrounding basin area seems to be an important factor causing spatiotemporal variability in the phytoplankton biomass in the southern sulu sea and the western celebes sea

seasonal variation of planktonic foraminiferal isotopic composition from sediment traps in the south china sea abstract the imprint of seasonal hydrographic changes on two widely distributed tropical subtropical planktonic foraminifer species globigerinoides sacculifer without sac and globigerinoides ruber white variety has been investigated using specimens collected in sediment traps deployed in the northern south china sea scs october 2000 october 2002 the faunal assemblage is dominated by g ruber during the warm summer months whereas g sacculifer is consistently present year round at abundances of less than 20 in general the measured 18o and 13c isotopic compositions of g ruber are more depleted than those of g sacculifer and the 18o difference between seasons summer vs winter is comparable to that of the local glacial interglacial cycle ca 1 the lowest 13c values are associated with relatively heavy 18o values in january and march for both species and suggest higher nutrient levels in the surface water that are likely related to the prevailing winter monsoon this speculation is supported by the increase in terrigenous input to the traps brought by the winter monsoon the ratio between 18o and 13c in g ruber is approximately two times that of g sacculifer with a 18o 13c slope of 1 18 vs 0 55 and differs from that in most biogenic carbonates 0 25 0 33 based on culture and field studies which indicate enhanced kinetic fractionation at higher ambient carbonate ion concentrations co3 however similar regression slopes of 18o 13c 0 52 to 0 6 are also derived for g sacculifer collected from plankton tows factors other than the carbonate ion effect hence appear to be responsible for the negative relationship between 18o and 13c in this region

evaluating the utility of b ca ratios in planktic foraminifera as a proxy for the carbonate system a case study of globigerinoides ruber b ca ratios in foraminifera have attracted considerable scientific attention as a proxy for past ocean carbonate system however the carbonate system controls on b ca ratios are not straightforward with inline image inline image in situ inline image at saturation correlating best with b ca ratios in benthic foraminifera rather than ph inline image or inline image as a simple model of boron speciation in seawater and incorporation into caco3 would predict furthermore culture experiments have shown that in planktic foraminifera properties such as salinity and b sw can have profound effects on b ca ratios beyond those predicted by simple partition coefficients here we investigate the controls on b ca ratios in g ruber via a combination of culture experiments and core top measurements and add to a growing body of evidence that suggests b ca ratios in symbiont bearing foraminiferal carbonate are not a straightforward proxy for past seawater carbonate system conditions we find that while b ca ratios in culture experiments covary with ph in open ocean sediments this relationship is not seen in fact our b ca data correlate best with inline image a previously undocumented association and in most regions salinity these findings might suggest a precipitation rate or crystallographic control on boron incorporation into foraminiferal calcite regardless our results underscore the need for caution when attempting to interpret b ca records in terms of the ocean carbonate system at the very least in the case of mixed layer planktic foraminifera

recent planktonic foraminifers and their relationships to surface ocean hydrography of the south china sea the relative abundances of recent planktonic foraminifers from surface sediments on the sea floor reveal relationships to hydrographic variables of the ocean surface to investigate whether the evect of the vertical structure of oceanic upper layer environments is important to the changes in the abundance of planktonic foraminifers a set of 173 coretop faunal data from modern south china sea scs surface sediments was compiled for comparison with direct observations of sea surface temperature sst and the depth of thermocline dot the coretops used in this study are distributed within the area of 25 n and 105 125 e with water depths ranging from 68 to 3990 m the relationships between the abundances of planktonic foraminifer species and hydrographic variables were examined using simple correlation analyses in the analyses four groups of planktonic foraminifers with diverent ecological preferences were identified group i faunas primarily reliant on dot with positive correlations n dutertrei group ii faunas reliant on both sst and dot showing negative correlations with sst and positive correlations with dot g glutinata p obliquiloculata and g bulloides group iii faunas reliant on both sst and dot showing positive correlations with sst and negative correlations with dot including g sacculifer g menardii and g aequilateralis and group iv faunas reliant on both sst and dot with positive correlations g ruber though each of these species displays selectivity of ecological controls these results indicate that in the scs correlations between faunal abundances of planktonic foraminifers and sst or dot are about equally significant this study also indicates a need for re evaluating the relationships between planktonic foraminifer abundances and many other important hydrographic variables in the upper layer of oceans on a more regional scale 1998 elsevier science b v all rights reserved

variability in ice motion at a land terminating greenlandic outlet glacier the role of channelized and distributed drainage systems we use a combination of field observations and hydrological modelling to examine the mechanisms through which variability in meltwater input affects ice motion at a land terminating greenlandic outlet glacier we find a close agreement between horizontal ice velocity vertical ice velocity and modelled subglacial water pressure over the course of a melt season on this basis we argue that variation in horizontal and vertical ice velocity primarily reflects the displacement of basal ice during periods of cavity expansion and contraction a process itself driven by fluctuations in basal water pressure originating in subglacial channels this process is not captured by traditional sliding laws linking water pressure and basal velocity which may hinder the simulation of realistic diurnal to seasonal variability in ice velocity in coupled models of glacial hydrology and dynamics

abrupt glacier motion and reorganization of basal shear stress following the establishment of a connected drainage system three episodes of strong basal motion occurred at trapridge glacier yukon territory canada on 11 june 1995 following the establishment of a connected subglacial drainage system responses to these spring events are noted in the records for 42 instruments and were recorded throughout the 60 000 m study area strong basal motion during the events is indicated by ploughmeter load bolt and vertical strain records and abrupt pressure changes in several transducer records denote damage caused by extreme pressure pulses these pressure pulses generated by the abrupt basal motion also resulted in the failure of seven pressure sensors records for pressure turbidity and conductivity sensors indicate that basal drainage patterns did not change significantly during the events geophone records suggest that the episodes of basal motion were precipitated by the gradual failure of a sticky spot following hydraulic connection of part of the study area this failure resulted in the transfer of basal stress to the unconnected region of the bed during the course of the events no evidence for strong basal motion is seen in the instrument records for several weeks following the events suggesting that the mechanical adjustments resulted in a stable configuration of basal stresses this event illustrates how unstable situations can be quickly accommodated by mechanical adjustments at the glacier bed

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

155 000 years of west african monsoon and ocean thermal evolution a detailed reconstruction of west african monsoon hydrology over the past 155 000 years suggests a close linkage to northern high latitude climate oscillations ba ca ratio and oxygen isotope composition of planktonic foraminifera in a marine sediment core from the gulf of guinea in the eastern equatorial atlantic eea reveal centennial scale variations of riverine freshwater input that are synchronous with northern high latitude stadials and interstadials of the penultimate interglacial and the last deglaciation eea mg ca based sea surface temperatures ssts were decoupled from northern high latitude millennial scale fluctuation and primarily responded to changes in atmospheric greenhouse gases and low latitude solar insolation the onset of enhanced monsoon precipitation lags behind the changes in eea ssts by up to 7000 years during glacial interglacial transitions this study demonstrates that the stadial interstadial and deglacial climate instability of the northern high latitudes exerts dominant control on the west african monsoon dynamics through an atmospheric linkage

rheological nonlinearity and flow instability in the deforming bed mechanism of ice stream motion contrary to what has recently been assumed in modeling the proposed deforming bed mechanism for the rapid motion of antarctic ice streams the rheology of water saturated till is probably highly nonlinear according to information from soil mechanics and preliminary experiments on till from the base of ice stream b the equivalent flow law exponent n is probably as high as 100 and the nonlinearities of the shear stress and effective pressure dependences are closely linked the high nonlinearity has important consequences for the deforming bed mechanism a flow system operating by this mechanism can be unstable as a result of feedback from the generation of basal water by shear heating of basal till the short term feedback effect is analyzed for a perturbation in a model ice stream in which the basal meltwater is transported through a distributed system of narrow gap conduits at the ice till interface although the analysis is approximate and some of the system parameters are poorly known the results suggest that the deforming bed mechanism is unstable for n 20 the apparent lack of such an instability in the currently active ice streams implies that their motion is controlled not by the deforming bed mechanism but by some other as yet unidentified mechanism

structures and fabrics in glacial ice a review abstract glaciers ice sheets and ice caps represent tectonic systems driven by gravity their movement can be studied in real time and the rheological properties and strength of ice determined from laboratory experiments and field measurements all glacial ice has primary stratification exhibited by variations in grain size bubble content and debris content as it deforms with deformation dominated by plastic flow and recrystallization accompanied locally by fracture under tension a suite of structures develops that reflects the primary fabric of the ice and the anisotropy that develops as a result of cumulative deformation initial variations in solid impurity content and strain dependent anisotropy as a result of a crystallographic fabric give rise to effective viscosity increases or decreases compared to isotropic polycrystalline ice of about a factor of ten foliation develops from inherited mostly stratification or introduced mostly ice veins or fracture traces fabric elements and from dynamic recrystallization it is largely dependent on the accumulated strain which is highest at the base and near the margins of glaciers ice sheets and ice streams folds develop largely passively due to initial amplification of irregularities in the primary stratification to variations in flow with time or to inhomogeneous flow associated with shear zones and ductile accommodation around open fractures buckle folds and boudinage mostly on a small scale occur where viscosity contrast is large mostly in basal ice thrusting and wrench faulting are documented in surging glaciers but theoretically most unlikely and rare or absent elsewhere many structures interpreted as faults are not due to shear failure but rather result from shear displacements during opening and closing of tensile fractures

waves of accelerated motion in a glacier approaching surge the mini surges of variegated glacier alaska u s a periods of dramatically accelerated motion in which the flow velocity increases suddenly from about 55 cm d to a peak of 100 300 cm d and then decreases gradually over the course of a day occurred repeatedly during june and july 1978 81 in variegated glacier alaska a surging type glacier that surged in 1982 83 these mini surges appear to be related mechanistically to the main surge the flow velocity peak propagates down glacier as a wave at a speed of about 0 3 km h over a reach of about 6 km in length it is accompanied by a propagating pressure wave in the basal water system of the glacier in which after a preliminary drop the pressure rises rapidly to a level greater than the ice overburden pressure at the glacier bed and then drops gradually over a period of 1 2 d usually reaching a new low for the summer the peak velocity is accompanied by a peak of high seismic activity due to widespread fresh crevassing it is also accompanied by a rapid uplift of the glacier surface amounting to 6 11 cm which then relaxes over a period of 1 2 d maximum uplift rate coincides with the peak in flow velocity the peak in accumulated uplift lags behind the velocity peak by 2 h the uplift is mainly due to basal cavitation driven by the high basal water pressure although the strain wave associated with the mini surge motion can also contribute basal cavitation is probably responsible for the pulse of high turbidity that appears in the terminal outflow stream in association with each mini surge in the down glacier reach where the mini surge waves are attenuating the observed strain wave corresponds to what is expected for the propagating pulse in flow velocity but in the reach of maximum mini surge motion the strain wave has a form quite different possibly related to special features in the mini surge initiation process from that point up stream the flow acceleration in the mini surges is due to enhanced basal sliding caused by the high basal water pressure and the consequent reduction of bed friction a preliminary velocity increase shortly before the pressure wave arrives is caused by the forward shove that the main accelerated mass exerts on the ice ahead of it and the resulting preliminary basal cavitation causes the drop in water pressure shortly before the pressure wave arrives the mini surge wave propagation is controlled by the propagation of the water pressure wave in the basal water conduit system the propagation characteristics result from a longitudinal gradient up glacier increase in hydraulic conductivity of the basal water system in response to the up glacier increase of the basal water pressure in the mini surge wave the mini surge waves are initiated in a succession of areas situated generally progressively up glacier during the course of the summer season in these areas presumably melt water that has accumulated in subglacial reservoirs is released suddenly into the basal water system immediately below generating a pressure rise that propagates down stream from there relationships of the mini surges to the main surge are seen in the role of high basal water pressure in causing the rapid glacier motion in both phenomena in the pulse propagation features of both and in the high outflow turbidity associated with both the mini surges of variegated glacier have a strong resemblance to movement and uplift events observed in unteraargletscher and findelengletscher switzerland this bears on the question whether the mini surges are a particular characteristic of surge type glaciers prior to surge

hydrological discharges and motion of fels and black rapids glaciers alaska u s a implications for the structure of their drainage systems characteristics of the hydrology and motion of black rapids and fels glaciers alaska were observed from 1986 to 1989 hydrological measurements included stage electrical conductivity and suspended sediment concentration in the discharge stream of each glacier and were made at 0 5 1 h intervals continuously through most of the melt seasons variations in the glacier speed were monitored through the full year at a number of locations along the length of each glacier using time lapse photography 1 d time resolution strain meters 0 5 1 h resolution and seismometers set up to count acoustic emissions both glaciers show similar seasonal diurnal and short term event changes in hydrological discharges and ice speed the hydrological behavior is analyzed in terms of a fast sub system composed of surface streams moulins and large tunnels with discharge that responds rapidly and a slow sub system composed of heterogeneous small passageways through the ice and distributed over the bed that maintain approximately uniform discharge over a day the timing and amplitude of water discharge in the diurnal cycle indicate that roughly 10 40 of the water is routed directly into the fast system the remaining 90 60 of the water enters the slow system dilution of the solute discharged from the slow system by the variable discharge in the fast system results in changes in water discharge and solute concentration that are approximately equal in relative amplitude and inversely related a small time lag from discharge maximum minimum to solute minimum maximum suggests that the fast system is confined to roughly the lowermost 30 40 of the full glacier length the residence time of water in the fast system is short compared to 1 d the slow system contains both short and long residence time passages characteristics of the diurnal cycles are somewhat variable through the melt season but no systematic evolutionary patterns were discerned even though large changes in the mean discharges of water and solutes occur which suggests parallel evolution of the variables that control the response of the fast system events were characterized by contemporaneous increases in suspended sediment concentration in the discharge water and distinct changes in straining on the glaciers events caused by increases in melt or precipitation related to weather and events related to release from reservoirs internal to the glaciers could be distinguished based on the changes in electrical conductivity of the discharge water the correlated changes in sediment discharge and motion of the glaciers indicate that the events were associated with temporary modifications of the slow passages distributed over the bed that allowed enhanced sliding and access of basal water flow to erosion products hydrological differences between black rapids and fels glaciers can be explained by differences in the size of the glaciers if there is a difference in bed structure that explains the difference in dynamics surge black rapids glacier versus non surge fels glacier it does not affect the hydrological parameters that were observed

propagating strain anomalies during mini surges of variegated glacier alaska u s a analyse des deplacements acceleres observes a l aide de jauges de deformation et de geophones 1979 1980 1981 evolution des mini surges deformations glissement basal

a late quaternary planktonic foraminifer faunal record of rapid climatic changes from the south china sea abstract a high resolution planktonic foraminifer record from a core recovered from the south china sea scs sonne 17938 2 19 47 2 n 117 32 3e 2840 m t 250 1000 years shows rapid millennial scale changes in the western pacific marginal sea climate during the last 30 000 years the scs is the largest western pacific marginal sea off the southeast asian continent the area today dominated by seasonal monsoon changes quantitative analyses of planktonic foraminifer faunal abundance data from the core indicate large downcore variations in the relative abundances of the dominant taxa since about 30 000 years ago in the isotope stage 3 further analyses indicate that the abundance of g inflata a good indicator species for cold sst 13 19 c and deep mld 100 125 m waters shows abrupt shifts during stages 2 and 3 the abundance record of g inflata tends to be punctuated by quasi periodic short intervals 2000 3000 yrs where its abundance reaches 15 or greater superimposed on generally low 5 10 background values this pattern suggests an instability of surface ocean conditions of the scs during the past 30 000 years the abrupt abundance changes of g inflata correlate well with similar climatic changes observed from a gisp2 ice core 18o and north atlantic core dsdp 609 n pachyderma s and lithic grain abundances during heinrich events these results suggest that the millennial scale variability of climate is not peculiar to the atlantic region apparently the rapid scs climatic changes during heinrich events are driven by effective mechanisms of particularly the effects of shifts in the latitudinal position of the siberia high pressure system

instruments and methods direct measurement of sliding at the glacier bed sliding at the base of trapridge glacier yukon territory canada was measured using a drag spool we describe this simple and inexpensive instrument as well as its installation and operation from 1990 to 1992 seven sites were instrumented with drag spools at six of the sites basal sliding during the period of observation accounted for 50 70 of the total flow observed at the glacier surface the contribution from ice creep is known to be small so most of the remaining surface motion must be attributed to subglacial sediment deformation for the seventh site the observed sliding rate was 90 of the total flow an indication that the sliding contribution varies spatially across the bed diurnal variations in the response of one of our instruments appear to be correlated to subglacial water pressure fluctuations and are interpreted in terms of changes in sliding velocity rather than the opening and closing of basal cavities

combined measurements of subglacial water pressure and surface velocity of findelengletscher switzerland conclusions about drainage system and sliding mechanism interpretation des mesures de pression dans les forages et des vitesses superficielles la comparaison avec les modeles suggere que l on a neglige le frottement du aux debris dans les modeles et qu il n existe jamais de chenaux cylindriques rectilignes

seasonal variations of modern planktonic foraminifera in the south china sea although foraminiferal census and isotope analyses from sediment cores have been widely applied to paleoceanographic reconstructions in the south china sea scs their modern counterparts i e foraminiferal shells from sediment traps and plankton tows have been the subjects of few studies in this region in this investigation relative abundances of the most popular species used to reconstruct late quaternary tropical sea surface conditions have been studied in plankton tows from the scs in order to offer better constraints on the interpretation of downcore records in addition to the seasonal differences the spatial variations in the faunal assemblage are evident from south to north in the scs basin based on contemporary tows for example the species globigerinella aequilateralis is found to be relatively dominant in the southern lower latitude basin but its relative abundance is significantly higher in planktonic tows than in sediments indicating its proneness to burial dissolution pulleniatina obliquiloculata an index taxon for the kuroshio current is only abundant in the northern part of the scs basin the measured oxygen isotope compositions 18o of globigerinoides ruber globigerinoides sacculifer neogloboquadrina dutertrei and p obliquiloculata all show a good relationship with temperature in the mixed layer tmix the carbon isotope compositions 13c also display a positive distribution pattern relative to tmix but with a less significant correlation in winter months than 18o differences of 18o between shallower g sacculifer and g ruber and deep dwellers n dutertrei and p obliquiloculata accurately record the temperature gradient between the surface mixed layer and 100 m water depth supporting application of this proxy to the reconstruction of upper water column stratification

basal hydraulic system of a west antarctic ice stream constraints from borehole observations pressure and tracer measurements in boreholes drilled to the bottom of ice stream b west antarctica are used to obtain information about the basal water conduit system in which high water pressures are developed these high pressures presumably make possible the rapid movement of the ice stream pressure in the system is indicated by the borehole water level once connection to the conduit system is made on initial connection here also called breakthrough to the basal water system the water level drops in a few minutes to an initial depth in the range 96 117 m below the surface these water levels are near but mostly somewhat deeper than the flotation level of about 100m depth water level at which basal water pressure and ice overburden pressure are equal which is calculated from depth density profiles and is measured in one borehole the conduit system can be modelled as a continuous or somewhat discontinuous gap between ice and bed the thickness of the gap has to be about 2 mm to account for the water level drop on breakthrough and about 4 mm to fit the results of a salt tracer experiment indicating downstream transport at a speed of 7 5 mm s 1 the above gap conduit model is however ruled out by the way a pressure pulse injected into the basal water system at breakthrough propagates outward from the injection hole and also by the large hole to hole variation in measured basal pressure which if present in a gap conduit system with 2 or 4 mm would result in unacceptably large local water fluxes an alternative model that avoids the e objections called the gap opening model involves opening a gap as injection proceeds starting with a thin film the injection of water under pressure lifts the ice mass a round the borehole creating a gap 3 or 4 mm wide at the ice bed interface evaluated quantitatively the gap opening model accounts for the volume of water that the basal watery system accepts on breakthrough which obviates the gap conduit model in order to transport basal meltwater from upstream it is then necessary for the complete hydraulic model to contain also a network of relatively large conduits of which the most promising type is the canal conduit proposed theoretically by walder and fowler 1994 flat low conduits incised into the till 0 1 m deep and perhaps 1 m wide with a flat ice roof the basal water pressure data suggest that the canals are spaced 50 300 m apart much closer than r tunnel would be the deepest observed water level 117 m i the most likely to reflect the actual water pressure in the canals corresponding to a basal effective pressure of 1 6 bar in this interpretation the shallower water levels are affected by loss of hydraulic head in the narrow passageway s that connect along the bed from borehole to canal s once a borehole has frozen up and any passageways connecting with canals have become closed a pressure sensor in contact with the unfrozen till that underlies the ice will measure the pore pressure in the till given enough time for pressure equilibration this pressure varies considerably with time over the equivalent water level range from 100 to 113 m basal pressure sensors 500 m apart report uncorrelated variations whereas sensors in boreholes 25 m apart report mostly but not entirely well correlated variations of unknown origin in part of the record remarkable anticorrelated variations are interspersed with positively correlated one and there are rare abrupt excursions to extreme water levels as deep as 125m and as shallow as 74 m a diurnal pressure fluctuation intermittently observed may possibly be caused by the ocean tide in the ross sea the lack of any observed variation in ice stream motion when large percentagewise variations in basal effective pressure were occurring according to our data suggests that the observed pressure variations are sufficiently local and so randomly variable from place to place that they are averaged out in the process by which the basal motion of the ice stream is determined by an integration over a large area of the bed

planktonic foraminifera differential dissolution and the quaternary stable isotope record in the west equatorial pacific differential dissolution affects the isotopic composition of different species of planktonic foraminifera in different ways in the two species studied here in cores from ontong java plateau the less resistant species globigerinoides sacculifer is more readily affected at a shallower depth than the more resistant species pulleniatina obliquiloculata 2 9 versus 3 4 km but shows a smaller and less predictable response to partial dissolution 0 2 to 0 3 per mil versus 0 6 to 0 7 per mil comparison of isotopic values from the last glacial period with those from the late holocene indicates that the apparent dissolution effect is considerably reduced during the last glacial presumably due to reduced dissolution intensity during glacial time a change in the level of the lysocline of about 400 m is suggested in the published isotope records from pacific cores v28 238 and v28 239 the dissolution generated difference in 18o noted previously by shackleton and opdyke 1976 is seen to describe a mid brunhes dissolution maximum between 300 and 500 thousand years ago this mid brunhes dissolution excursion is well known from the pacific and the indian ocean

benthic foraminiferal paleoceanography of the south china sea over the last 40 000 years benthic foraminifera in gravity and piston cores from two sites of the northern and southern slopes of the south china sea scs were analyzed to evaluate changes in surface productivity and deep water mass characteristics over the last 40 000 years our observations suggest that changes in organic carbon flux that is food supply and chemical and or physical properties of the ambient water mass may be the two primary and intercorrelated factors controlling the distribution patterns of benthic foraminifera when organic carbon flux increased above 3 5 g c m 2 yr 1 in the southern scs during the last glacial maximum and in the northern scs during the first part of the holocene around 10 ka b p a group of detritus feeders including bulimina aculeata and uvigerina peregrina dominated the benthic foraminiferal assemblage as shown by relative abundance and accumulation rates this may reflect episodes of increased surface productivity possibly induced by increased input of nutrients from nearby river runoff suspension feeders such as cibicidoides wuellerstorfiand a group of opportunistic species including oridorsalis umbonatus melonis barleeanum and chilostomella ovoidea gradually became more abundant than detritus feeders as soon as the organic carbon flux decreased to 2 5 3 5 g c m 2 yr 1 similar glacial to interglacial changes in relative abundance and accumulation rates were observed in both cores for a number of species including eggerella bradyi globocassidulina subglobosa astrononion novozealandicum sphaeroidina bulloidesand cibicidoides robertsonianus these changes were not correlated to the distribution patterns of organic carbon in both cores and may have been related to yet unspecified changes in chemical and or physical properties of the ambient water mass independent of changes in organic carbon flux 1999 elsevier science b v all rights reserved

svalbard surge dynamics derived from geometric changes geometric changes on a sample of svalbard glaciers were studied using subtraction of repeat digital terrain models to determine early surge stage dynamics changes in surface features were also analyzed a number of new surges were found for glaciers not known to have surged previously the surge development could be followed through three stages of which the first two had not been previously described in svalbard the first two stages are mainly identified from glacier thickness changes and showed little visual evidence in stage 1 initial surface lowering was found in the upper part of the glacier followed by a thickening further down glacier in stage 2 stage 3 represents the period of well developed surge dynamics that is usually reported some surges ceased at stage 2 as a partial surge and never developed into a fully active surge these partial surges could be misinterpreted as rapid response to climate change the results of this study further support previous findings that the majority of svalbard glaciers are of surge type data archives have greatly facilitated the search for signs of surges and the recapturing of the course of events in this paper we present a number of new observations of svalbard surge type behaviour based on evidence from geometric changes and complemented by observations of newly developed crevasse fields two criteria are used to identify a surge either individually or in combination 1 mass displacement from the upper to the lower glacier part and 2 presence of new crevasse fields which indicate rapid or strong changes in stresses the aims of our study are to contribute to a more complementary picture and better understanding of the transition from build up stage via initial surge dynamics to the previously described mature stage where the changes are more pronounced we also investi gate whether all surges develop fully the implications of partial surges for interpretation of surface lowering related to varying climate conditions and finally the large spread in estimates for the number of surge type glaciers in svalbard

ice stream subglacial access for ice sheet history and fast ice flow the beamish project on rutford ice stream west antarctica and initial results on basal conditions

reduced el nino southern oscillation during the last glacial maximum el nino southern oscillation enso is a major source of global interannual variability but its response to climate change is uncertain paleoclimate records from the last glacial maximum lgm provide insight into enso behavior when global boundary conditions ice sheet extent atmospheric partial pressure of co2 were different from those today in this work we reconstruct lgm temperature variability at equatorial pacific sites using measurements of individual planktonic foraminifera shells a deep equatorial thermocline altered the dynamics in the eastern equatorial cold tongue resulting in reduced enso variability during the lgm compared to the late holocene these results suggest that enso was not tied directly to the east west temperature gradient as previously suggested rather the thermocline of the eastern equatorial pacific played a decisive role in the enso response to lgm climate

the variation of upper ocean structure and paleoproductivity in the kuroshio source region during the last 200 kyr a core from the source region of the kuroshio warm current east of the luzon island was analyzed using several proxies in order to study the variability of the western pacific warm pool wpwp during the last two glacial interglacial cycles primary productivity pp variations were deduced from variations in the coccolith flora primary productivity was higher during glacial periods the end of marine isotope stage mis 3 some periods in mis 2 and 6 and decreased during interglacial periods mis 7 mis se and probably mis 5c 5d with the lowest pp in mis 5e variations in the delta 13 c difference in benthic and bulk carbonate thus in the vertical gradient of delta 13 c in dissolved inorganic carbon delta delta 13 c c wuellerstorfi n dutertrei and delta delta 13 c c wuellerstorfi coccolith coincided with the pp changes showing that export productivity was low during interglacial periods mis 7 mis 5e and holocene and high during glacial periods mis 6 probably mis 5c 5d late mis 4 and late mis 3 comparison of foraminiferal carbonate dissolution indicators and pp changes reveals that nannofossil assemblage in core ph05 5 is not sensitive to carbonate dissolution intensity the depth of the thermocline dot was estimated from planktonic forminiferal assemblages and was relatively greater during interglacial periods mis 7 mis 5e probably mis 5c and holocene than during glacials middle mis 6 probably mis 5b and 5d some periods in mis 4 mis 3 and mis 2 good coherence between the paleoproductivity records and the dot suggests that the dot changes could be the primary control factor in changes of paleoproductivity and the glacial high productivity in the kuroshio source region could be associated with a global increase of nutrient concentration in the intermediate waters that upwelled into the photic zone the low co 2 values derived for intervals of high productivity and a relatively shallow dot suggest that the changes in biological productivity and dot in the equatorial pacific could have modified atmospheric co 2 concentrations high sea surface temperatures ssts during the warm mis 5e in combination with intensified monsoonal rain fall could have resulted in a more intense stratification of the upper waters resulting in low nutrient supply to the surface waters and a resulting decrease in productivity c 2010 elsevier b v all rights reserved

gaining insights into interrill erosion processes using rare earth element tracers abstract increasing interest in developing process based erosion models requires better understanding of the relationships among soil detachment transportation and deposition the objectives are to 1 identify the limiting process between soil detachment and sediment transport for interrill erosion 2 understand the dynamic relationships between transport and deposition by tracking sediment fate with multiple tracers and 3 verify the effects of slope length on interrill soil erosion five rare earth element ree tracers were applied in five bands or segments to track sediment dynamics on a 10 4 4 m long uniform slope under simulated rainfall a silt loam soil with 8 clay and 87 silt was used six rain events were applied the first four with 60 mm h 1 and the last two with 90 mm h 1 sediment in runoff and deposition along the slope were measured results confirmed that interrill soil erosion was controlled by the transport process thus soil erodibility estimated with many interrill erosion models was actually sediment transportability as the slope length increased soil erosion rates initially increased and then decreased indicating that the upper section was dominated by erosion and the lower section by transport raindrop driven creeping prevailed in the upper section while flow driven rolling dominated in the lower section sediment influx from upslope clearly suppressed soil detachment downslope moreover the steady state sediment discharge from a segment was positively correlated to the amount of sediment deposited downslope from that segment implying that 1 re detachment transport and deposition occurred simultaneously in the system and 2 sediment was transported in a form of bedload mainly rolling or creeping on interrill areas sediment delivery ratios of each segment tended to slightly increase downslope suggesting the flow driven transport was more efficient than the raindrop driven transport the sequence of sediment discharged from different slope positions was inconsistent with the transport distance theory however interrill erosion processes vary with soil slope and rainfall properties and the findings here need to be verified in different conditions

characterizing the may 2015 karayaylak glacier surge in the eastern pamir plateau using remote sensing we investigate an internal surge of karayaylak glacier which was reported by the media in may 2015 to differentiate the may 2015 glacier surge from other glacier advances we surveyed changes in velocity crevasses and glacier area using landsat 8 oli l1t zy 1 02c and gaofen 1 images from october 2014 to july 2015 the velocity measured by automatic feature extraction and tracking during the active phase was 10 100 times the velocity during the quiescent phase with a maximum of 20 2 0 9 m d 1 mean standard error from 8 to 15 may 2015 in the west branch of the glacier the surge initiation and termination took place from 13 april to 16 june 2015 ice in the west branch length 7 km area 6 8 km 2 of karayaylak glacier accelerated down to the east branch leading to the development of crevasses and ice covering an additional 0 1 km 2 of summer pasture on the northwestern side however we detected no advance of the glacier s terminus

seasonal variations in planktonic foraminiferal flux and oxygen isotopic composition in the western north pacific implications for paleoceanographic reconstruction abstract the oxygen isotopic composition 18o of planktonic foraminiferal shells in seafloor sediment provides information on past surface oceanography knowledge of seasonal and depth habitat as well as the 18o disequilibrium vital effect is essential to constrain the interpretation of sedimentary 18o here we present a 1 year time series of planktonic foraminiferal shell fluxes and 18o from a sediment trap moored in the northwestern margin of the north pacific the vital effect and calcification depth for four species were estimated by comparing shell 18o and the predicted values of equilibrium calcite calculated from temperature and estimated 18o in seawater six major species neogloboquadrina incompta neogloboquadrina dutertrei neogloboquadrina pachyderma globigerina quinqueloba globigerina bulloides and globorotalia scitula constituted 97 of the total foraminiferal flux most major species showed large fluxes in june and december corresponding to periods of the development and disruption of the seasonal thermocline implying the importance of nutrient injection and or circulation for foraminiferal fluxes additional peaks in n dutertrei and n pachyderma were observed in august the seasonal successions of foraminiferal fluxes corresponded to surface ocean stratification conditions and food availability which are closely related to circulation of local currents vital effect estimations suggest that shells calcified in equilibrium for g bulloides and n pachyderma sinistral s and with a 0 7 offset for n dutertrei dextral d a 1 0 offset for n incompta d and a 0 3 offset for n pachyderma d the calculation of flux weighted 18o values reveals that the sedimentary 18o values of g bulloides n dutertrei d and n incompta d reflect surface temperature in winter season and those of n pachyderma s and n pachyderma d reflect summer and annual mean subsurface temperature respectively the shallow calcification depths for the four species suggest that 18o between different species 18o in the western north pacific does not work for reconstructing past stratification conditions unlike in other regions rather the 18o between n pachyderma s and g bulloides n dutertrei d or n incompta d may be a more suitable proxy for past seasonality

tracing sediment redistribution across a break in slope using rare earth elements experimentally determined spatial patterns of soil redistribution across a break in slope derived using 10 rare earth element ree oxides as sediment tracers are presented an erosion experiment was conducted using simulated rainfall within a laboratory slope model measuring 2 5 m wide by 6 m long with a gradient of 15 declining to 2 soil was tagged with multiple ree and placed in different locations over the slope and at the end of the experiment ree concentrations were measured in samples collected spatially a new method was developed to quantify the erosion and deposition depths spatially the relative source contributions to deposited sediment and the sediment transport distances particle size selectivity over an area of net deposition was also investigated by combining downslope changes in particle size distributions with changes in sediment ree composition within a flow pathway during the experiment the surface morphology evolved through upslope propagation of rill headcuts which gradually incised the different ree tagged zones and led to sediment deposition at the break in slope and the development of a fan extending over the shallow slope segment the spatial patterns in ree concentrations the derived erosion and deposition depths the relative source contributions to deposition zones and the sediment transport distances corroborate the morphological observations and demonstrate the potential of using ree for quantifying sediment transport processes

rare earth element oxides for tracing sediment movement the development of soil conservation plans and evaluation of spatially distributed erosion models require knowledge of rates of soil loss and sedimentation on different landscape elements and slope positions characterization of soil erosion rates and patterns within watersheds is important for the understanding of erosion processes and landscape evolution experimental data that show spatial translocation of soil on slopes are limited a method for obtaining spatially distributed information on sediment movement employing rare earth element ree oxides is proposed five ree oxides in powder form were uniformly mixed with the soil on different parts of a 10 slope in a 4 4 m soil bed particle translocation was measured during eight simulated rainfalls at 60 mm h 1 intensity a laser scanner was utilized to obtain digital elevation models dems of the soil surface that were used as the reference data to compare with the tracer method ree concentration in soil and runoff samples was determined by inductively coupled plasma mass spectrometry icp ms erosion rates for different slope positions estimated from ree concentrations correlated with those calculated from the dems with relative differences for different slope sections of 4 40 the enrichment ratio for this type of tracer was 1 7 the amount of sediment produced on different parts of the slope varied with the greatest erosion occurring on the upper middle part of the slope the experiment showed that the multi element tracer method provided a satisfactory way to study soil erosion distribution on a uniform slope d 2003 elsevier b v all rights reserved

pleistocene sea surface temperature evolution early cooling delayed glacial intensification and implications for the mid pleistocene climate transition the mid pleistocene climate transition mpt is defined by the emergence of high amplitude quasi 100 ka glacial interglacial cycles from a prior regime of more subtle 41 ka cycles this change in periodicity and amplitude cannot be explained by a change in external astronomical forcing here we review and integrate published records of sea surface temperatures ssts to assess whether a common global expression of the mpt in the surface ocean can be recognized and examine our findings in light of mechanisms proposed to explain climate system reorganization across the mpt we show that glacial interglacial variability in ssts is superimposed upon a longer term cooling trend in oceanographic systems spanning the low to high latitudes regional variability exists in the timing of the onset and magnitude of cooling but in most cases a long term cooling trend begins or intensifies from 1 2 ma marine isotope stage mis 35 34 the sst cooling accompanies a long term trend towards higher global ice volume as recorded in benthic foraminifera 18o but predates a step like increase in 18o at 0 9 ma mis 24 22 that is argued to reflect expansion of continental ice sheets the strongest expression of pleistocene cooling is found during glacial stages whereas minor or negligible trends in interglacial temperatures are identified however pronounced cooling during both glacial and interglacial maxima is evident at 0 9 ma alongside the long term sst cooling trends quasi 100 ka cycles begin to emerge in both the sst and 18o records at 1 2 ma and become dominant with the expansion of the ice sheets at 0 9 ma we show that the intensified glacial stage cooling is accompanied by evolving pco2 abyssal ocean ventilation atmospheric circulation and or dust inputs to the southern ocean these changes in diverse environmental parameters suggest that glacial climate boundary conditions evolved across the mpt in turn these modified boundary conditions may have altered climate sensitivity to orbital forcing by placing pre existing ice sheets closer to some threshold of climate ice sheet response

mindanao dome variability over the last 160 kyr episodic glacial cooling of the west pacific warm pool we present sea surface upper thermocline and benthic delta 18 o data as well as temperature and paleoproductivity proxy data from the international marine global change study program images core md06 3067 6 degrees 31 n 126 degrees 30 e 1575 m water depth located in the western equatorial pacific ocean within the flow path of the mindanao current our records reveal considerable glacial interglacial and suborbital variability in the mindanao dome upwelling over the last 160 kyr dome activity generally intensified during glacial intervals resulting in cooler thermocline waters whereas it substantially declined during interglacials in particular in the early holocene and early marine oxygen isotope stage mis 5e when upwelling waters did not reach the thermocline during mis 3 and mis 2 enhanced surface productivity together with remarkably low sst and low upper ocean thermal contrast provide evidence for episodic glacial upwelling to the surface whereas transient surface warming marks periodic collapses of the mindanao dome upwelling during heinrich events we attribute the high variability during mis 3 and mis 2 to changes in the el nino southern oscillation state that affected boreal winter monsoonal winds and upper ocean circulation glacial upwelling intensified when a strong cyclonic gyre became established whereas el nino like conditions during heinrich events tended to suppress the cyclonic circulation reducing ekman transport thus our findings demonstrate that variations in the mindanao dome upwelling are closely linked to the position and intensity of the tropical convection and also reflect far field influences from the high latitudes

basal conditions and glacier motion during the winter spring transition worthington glacier alaska u s a observations of the motion and basal conditions of worthington glacier alaska u s a during late winter and spring melt seasons revealed no evidence of relationship between water pressure and sliding velocity measurements included borehole water levels used as a proxy for basal water pressure surface velocity englacial deformation sliding velocity and time lapse videography of subglacial water flow and bed characteristics the boreholes were spaced 10 15 m apart six were instrumented in 1997 and five in 1998 in late winter the water pressure field showed spatially synchronous fluctuations with a diurnal cycle the glacier s motion was relatively slow and non cyclic in spring the motion was characterized by rapid diurnally varying sliding the basal water pressure displayed no diurnal signal but showed high magnitude fluctuations and often strong gradients between holes this transition in character of the basal water pressure field may represent a seasonal evolution of the drainage system from linked cavities to a network of isolated patches and conduits these changes occurred as the glacier was undergoing a seasonal velocity peak the apparent lack of correlation between sliding velocity and water pressure suggests that local scale water pressure does not directly control sliding during late winter or early in the melt season

a general theory of glacier surges we present the first general theory of glacier surging that includes both temperate and polythermal glacier surges based on coupled mass and enthalpy budgets enthalpy in the form of thermal energy and water is gained at the glacier bed from geothermal heating plus frictional heating expenditure of potential energy as a consequence of ice flow enthalpy losses occur by conduction and loss of meltwater from the system because enthalpy directly impacts flow speeds mass and enthalpy budgets must simultaneously balance if a glacier is to maintain a steady flow if not glaciers undergo out of phase mass and enthalpy cycles manifest as quiescent and surge phases we illustrate the theory using a lumped element model which parameterizes key thermodynamic and hydrological processes including surface to bed drainage and distributed and channelized drainage systems model output exhibits many of the observed characteristics of polythermal and temperate glacier surges including the association of surging behaviour with particular combinations of climate precipitation temperature geometry length slope and bed properties hydraulic conductivity enthalpy balance theory explains a broad spectrum of observed surging behaviour in a single framework and offers an answer to the wider question of why the majority of glaciers do not surge

spatial distribution and controlling factors of planktonic foraminifera in the modern western pacific abstract studies of the spatial distribution of living planktonic foraminifera in modern water columns are still lacking in the western pacific in this study 40 plankton tows at 8 stations were conducted focusing on the terminus of the north equatorial current nec and its two bifurcated branches in the western pacific the results show that planktonic foraminifera were in high abundance around the kuroshio current kc source region and the mindanao current mc system but in low abundance in the nec the planktonic foraminiferal assemblage was dominated by g sacculifer and g ruber with relative abundances of 44 0 and 27 3 respectively according to a cluster analysis of the results of seven stations the stations can be divided into three groups namely group nec group kc and group mc which displayed different features of planktonic foraminiferal assemblages the low abundance of planktonic foraminifera that characterized the nec stations may be induced by the thick mixed layer and deep thermocline nutricline in this region however stations in the kc region which also had thick mixed layers and deep thermoclines showed higher abundances of planktonic foraminifera than the nec stations this result was probably caused by the higher terrigenous input the planktonic foraminifera show the highest abundance at the mc stations which may be the result of existing upwelling conditions

stable isotopes in modern planktonic foraminifera sediment trap and plankton tow results from the south china sea abstract this study reports on the stable isotopic composition of modern planktonic foraminifera tests collected from plankton tows and sediment trap moorings in the northern south china sea plankton tow samplings were conducted at water depths of 50 100 and 200 m during various seasons between december 2002 and august 2008 the sediment trap array was deployed between august 2004 and february 2005 at water depths of 121 m 619 m and 3451 m four common and widely distributed tropical subtropical planktonic foraminifer species including globigerinoides ruber white variety globigerinoides sacculifer without sac neogloboquadrina dutertrei and pulleniatina obliquiloculata were analyzed for 18o and 13c within narrow shell size ranges and compared with the concurrent sea surface temperature sst and wind stress our results show that foraminiferal 18o is primarily influenced by seawater temperature while 13c is affected by surface water nutrients which in this region can be discerned from wind stress data the 18o and 13c values from foraminifers recovered in plankton tows generally show greater variability and more depleted 18o than values of tests collected by sediment traps for foraminifer tests collected by sediment trap the 18o of the shallow dwelling g ruber shows the largest amplitude variation ca 1 6 among the four species in contrast the 13c of p obliquiloculata shows relatively constant values throughout the study period a pattern of enriched 18o values associated with marked 13c depletion is common to three species collected between late october and late december 2004 this distinct isotopic signal corresponds to a decrease in sst and increase in wind stress indicating the onset of prevailing northeast winds during the winter season

benthic foraminiferal b ca ratios reflect deep water carbonate saturation state boron calcium ratios were measured in four benthic foraminiferal species three calcitic cibicidoides wuellerstorfi cibicidoides mundulus and uvigerina spp and one aragonitic hoeglundina elegans from 108 core top samples located globally comparison of coexisting species shows b ca of c wuellerstorfi c mundulus h elegans uvigerina spp suggestive of strong vital effects on benthic foraminiferal b ca a dissolution effect on benthic b ca is not observed core top data show large intra species variations 50 130 mol mol in b ca within a single species benthic foraminiferal b ca show a simple linear correlation with deep water co32 providing a proxy for past deep water co32 reconstructions empirical sensitivities of co32 on b ca have been established to be 1 14 0 048 and 0 69 0 072 mol mol per mol kg for c wuellerstorfi and c mundulus respectively the uncertainties associated with reconstructing bottom water co32 using b ca in c wuellerstorfi and c mundulus are about 10 mol kg a preliminary application shows that the last glacial maximum lgm b ca ratios were increased by 12 at 1 2 km and decreased by 12 at 3 5 4 0 km relative to holocene values in the north atlantic ocean this implies that the lgm co32 was higher by not vert similar 25 30 mol kg at intermediate depths and lower by not vert similar 20 mol kg in deeper waters consistent with glacial water mass reorganization in the north atlantic ocean inferred from other paleochemical proxies

surface ice motion deviating toward the margins during speed up events at gornergletscher switzerland 1 high frequency ice flow measurements during speed up events in gornergletscher switzerland revealed intriguing ice motion which has never been reported in detail before during the summer 2005 more than a 100 flow speed increase was observed three times at four gps stations installed across gornergletscher the speed ups were accompanied by a decimeter scale surface uplift two of the events were triggered by intensive surface melt and rainfall while the third one was due to the outburst of gornersee a glacier dammed lake located 2 km upglacier an interesting observation was ice motion deviating toward the side margins during the events as the glacier accelerated a transverse cross glacier velocity component was generated turning the flow direction away from the central flow line toward the margins when the glacier decelerated the transverse velocity component reversed so that the ice flowed back to the azimuth of the initial flow direction in the most significant case the trajectory of the survey stake deviated from the original track by 0 2 m in the transverse direction we hypothesize that the observed lateral ice motion was caused by locally elevated subglacial water pressure when the ice sole decoupled from the bed at a part of the glacier a point source of vertical displacement was transmitted to the surface through viscous ice this caused the transverse as well as vertical surface motion as observed in ground motion during magma intrusion the hypothesis was tested with a two dimensional ice flow model applied to the transverse glacier cross section the model confirmed that the surface ice would move toward the margins as observed in gornergletscher if subglacial water pressure exceeded the ice overburden pressure over a limited part of the bed

tracer techniques in aeolian research approaches applications and challenges abstract aeolian processes the entrainment transport and deposition of sediments by wind impacts climate biogeochemical cycles food security environmental quality and human health considering the multitude of interactions between aeolian processes and all the major components of the earth system there is a growing interest in the scientific community to quantify the wind related sediment movement process and redistribution rates at different spatial and temporal scales however this quantification is rather challenging due to the complexities of physical mechanisms involved in aeolian processes and the inherent fundamental differences from the rather well studied processes controlling fluvial erosion traditional techniques such as erosion plots and surveying methods for monitoring wind erosion are capable of quantifying sediment movement on small scales but they have a number of limitations in terms of the representativeness of the data obtained spatial and temporal resolution and the patterns over extended areas and the costs involved the demand for alternative methods of soil loss and sediment redistribution assessment in order to complement and enhance the existing methods has directed attention to use tracing approaches for monitoring rates and spatial patterns of sediment redistribution at various scales a comprehensive synthesis of available information from different scientific disciplines on aeolian tracer techniques their applications and limitations are important in understanding the role of aeolian processes and their interactions with the earths systems in changing climate and management scenarios the objective of this paper is to provide a scientific review of the current tracer approaches in aeolian studies including fallout radionuclides rare earth elements sediment finger printing and soil magnetism as well as giving an introduction of the potential tracers that are in development

glacier velocity and water input variability in a maritime environment franz josef glacier new zealand short term glacier velocity variations typically occur when a water input is accommodated by an increase in the subglacial water pressure although these velocity variations have been well documented on many glaciers few studies have considered them on glaciers where heavy rain and glacier melt occur year round this study investigates the relationship between water inputs and glacier velocity on franz josef glacier new zealand we installed six gnss stations across the lower glacier during austral summer 2010 11 and one station during summer 2012 13 glacier velocity remained elevated at all stations for 7 days following large rain events during diurnal melt events we find velocity variations in the early afternoon 12 00 16 00 at 600 m a s l and in the late evening 20 00 01 00 at 400 m a s l we hypothesize that the late evening velocity variations occurred as an upstream region of high subglacial water pressures and accelerated ice motion propagated downstream this mechanism may also explain the increased longitudinal compression and transverse extension across the lower glacier during speed up events our results indicate that the subglacial drainage system likely decreases in efficiency upstream and that the water input variability can still cause short term velocity variations despite the large year round water inputs

planktonic foraminifera in the sediment of a western boundary upwelling system off cabo frio brazil abstract the distribution of planktonic foraminifera in box core tops under the influence of a western boundary upwelling system along the southeastern brazilian continental margin was examined to evaluate the similarity percentage simper and to create a biofacies model for paleoenvironmental applications species associated with warm and oligotrophic water were distributed in the rio de janeiro sector of the campos basin while productive water species were most abundant in the rio de janeiro sector of the santos basin and cold water species were most abundant in the cabo frio upwelling system cfus four major biofacies are associated with the oceanographic setting of the cfus one from the campos basin a brazil current front one from the santos basin b mixture of coastal and oceanic waters and two associated with the cabo frio high in the northern biofacies c and southern biofacies d the distribution of biofacies c and d was associated with temperature differences biofacies c represents a mixture of upwelling and tropical waters while biofacies d represents a mixture of cold nutrient rich and santos basin waters these biofacies were also defined in core cf10 01b in which six main paleoceanographic phases were characterized during the last 9 cal kyr predominantly showing alternating dominance between biofacies c and d from 9 0 to 5 0 cal kyr before the present bp the system was dominated by biofacies c between 4 0 and 3 5 cal kyr bp biofacies d was dominant between 3 5 and 2 5 cal kyr bp a strong influence of coastal waters and weakened upwelling activity were indicated by the dominance of biofacies b c d the last 2 5 cal kyr was dominated by biofacies d the sst in this core was reconstructed using the modern analog technique mat which revealed 0 35 c of variability indicating no sst changes during the holocene the weak sensitivity of the mat was due to the interplay among different oceanographic features

planktonic foraminiferal records of east asia monsoon changes in the southern south china sea during the last 40 000 years planktonic foraminiferal assemblages and benthic foraminiferal oxygen isotopes were obtained in a gravity core n507 25 6 degrees 39 945 n 113 degrees 32 9361 e water depth 2006 m collected from the southern south china sea scs to investigate east asia monsoon changes during the last 40 000 years four cold events identified from four peaks of the relative abundance of neogloboquadrina pachyderma dex and globigerina quinqueloba correlate well with those in the hulu monsoon record within age uncertainty and can be linked to heinrich events in the northern atlantic high latitudes we suggest that the relative abundance of n pachyderma dex and g quinqueloba in the southern scs can be used as a direct proxy for east asia winter monsoon eawm changes during glacial periods in contrast to its low abundance in the northern scs and okinawa trough the relative abundance of pulleniatina obliquiloculata shows high values during the last glacial in the southern scs caused likely by the combined impact of optimum winter sea surface temperature sst and stronger mixing enhanced upwelling at that time a p obliquiloculata minimum event pme found in the okinawa trough and the northern and southern scs during the h1 period was possibly related to a large drop in winter sst due to the intensified eawm we propose that this pme can be also used as a reliable regional stratigraphic marker as the holocene one a 9 cm sandy silt layer deposit in core ns07 25 during the hi period probably related to the enhanced current that was caused by the especially strengthened eawm at that time the last deglacial warming recorded in the relative abundance of warm and cold species of planktonic foraminifer reveals that changes between the easm and eawm were not in phase but alternating between a winter monsoon dominated northern hemisphere influence and a summer monsoon dominated influence of the tropical dynamics and or southern hemisphere climate changes c 2009 elsevier b v all rights reserved

investigating source areas of eroded sediments transported in concentrated overland flow using rare earth element tracers rare earth element oxides reos have excellent potential for use as tracers in erosion studies using laboratory and field experiments we aimed to develop and test a simple application method for spreading reos and to use reos to determine the source of sediment to concentrated overland flow paths tracks left by farm machinery tramlines in fields act as concentrated flow paths delivering a large amount of surface runoff and entrained sediment to the field boundary however little is known regarding where this sediment is sourced from two field experiments were conducted to investigate this one looking at whether sediment is entrained from different points along the length of the tramline and one looking at the area over which sediment is entrained from either side of a tramline results from leaching tests and rainfall simulations clearly demonstrated the potential of this method for tracing sediment there was very little movement of reos through the soil profile and they were transported with sediment in overland flow in the field experiment a large proportion of the sediment transported in the tramline originated within the first metre either side of it however the total area over which eroded sediment collects and flows into the tramline is potentially large with small amounts of sediment eroded from the between 4 and 6 m being transported in the tramline reos have an excellent potential for use as a tracer of soil erosion they provide a quick and cheap method of identifying sources of eroded sediments and have good potential for use in determining erosion rates

links between proglacial stream suspended sediment dynamics glacier hydrology and glacier motion at midtdalsbreen norway two hourly suspended sediment concentration variations observed during the summer of 1987 in the proglacial stream draining midtdalsbreen norway are modelled using multiple regression and time series techniques suspended sediment fluctuations are influenced by stream discharge variations diurnal hysteresis effects medium term sediment supply and transport variations and the recent suspended sediment concentration history of the stream they do not appear to be influenced by seasonal exhaustion or rainfall variations possible reasons for this are discussed large positive residuals from the fitted models are major pulses of suspended sediment unrelated to discharge variations these sediment flushes correlate with periods of enhanced glacier motion they cannot be explained by enhanced sediment production by subglacial erosion but are probably due to the tapping of subglacially stored sediment during sudden changes in the hydraulics and or configuration of the subglacial hydrological system seasonal changes in the lag between glacier motion peaks and suspended sediment flushes suggest that the subglacial hydrological system evolves over the summer from a distributed to a more channelized configuration

foraminiferal faunal estimates of paleotemperature circumventing the no analog problem yields cool ice age tropics the sensitivity of the tropics to climate change particularly the amplitude of glacial to interglacial changes in sea surface temperature sst is one of the great controversies in paleoclimatology here we reassess faunal estimates of ice age ssts focusing on the problem of no analog planktonic foraminiferal assemblages in the equatorial oceans that confounds both classical transfer function and modern analog methods a new calibration strategy developed here which uses past variability of species to define robust faunal assemblages solves the no analog problem and reveals ice age cooling of 5 o to 6oc in the equatorial current systems of the atlantic and eastern pacific oceans classical transfer functions underestimated temperature changes in some areas of the tropical oceans because core top assemblages misrepresented the ice age faunal assemblages our finding is consistent with some geochemical estimates and model predictions of greater ice age cooling in the tropics than was inferred by climate long range investigation mapping and prediction climap 1981 and thus may help to resolve a long standing controversy our new foraminiferal transfer function suggests that such cooling was limited to the equatorial current systems however and supports climap s inference of stability of the subtropical gyre centers

the role of hydrologically driven ice fracture in drainage system evolution on an arctic glacier 1 observations from ellesmere island suggest that the connection between surface and subglacial drainage on a predominantly cold glacier is made abruptly by hydrologically driven propagation of fractures from the surface to the bed where ice is 150 m thick water ponded to a depth of 6 9 m within a supraglacial stream system before establishing a permanent bed connection multiple premonitory drainage events preceded the final drainage of ponded water implying that fracturing is necessary but insufficient to establish a permanent link between surface and subglacial drainage refreezing of water that penetrates the first fractures to form may reseal the connection while flow resistance within the subglacial system may delay the onset of continuous through flow a large volume of ponded water is required to enlarge fractures sufficiently by melting to maintain continuous drainage while feedbacks between subglacial hydrology and ice dynamics may assist in maintaining the connection and initiating subglacial outflow

using unsupported lead 210 measurements to investigate soil erosion and sediment delivery in a small zambian catchment abstract traditional techniques used to assemble information on rates of erosion and soil redistribution possess many important limitations as a result the use of environmental radionuclides and more particularly 137 cs measurements has attracted increasing attention in recent years as a means of obtaining spatially distributed information on rates of erosion and deposition the application of the 137 cs approach is however hampered in some areas of the world where 137 cs inventories are low and the low concentrations of 137 cs found in soils and sediments cause problems for laboratory analysis these problems will increase as time progresses due to the radioactive decay of the existing inventory most of which was deposited as fallout ca 40 years ago this contribution explores the potential for using another fallout radionuclide namely unsupported 210 pb as an alternative to 137 cs in the small 63 km 2 upper kaleya catchment in southern zambia where 137 cs inventories are already very low the approach employed with unsupported 210 pb is similar to that used for 137 cs although the essentially constant fallout of unsupported 210 pb through time means that the resulting estimates of erosion and soil redistribution rates reflect a longer period of time ca 100 years rather than ca 40 years the estimates of erosion and deposition rates derived from the unsupported 210 pb measurements are used to construct typical sediment budgets for the three main land use types in the upper kaleya catchment namely commercial cultivation communal cultivation and bush grazing the results obtained from the unsupported 210 pb are compared with equivalent results based on 137 cs measurements provided by a previous investigation undertaken in the study catchment the two sets of results are highly consistent the study reported confirms the viability of using unsupported 210 pb as an alternative to 137 cs in this environment and demonstrates that conjunctive use of both radionuclides can provide additional information on the erosional history of a study area