productivity collapses in the arabian sea during glacial cold phases 1 productivity in the arabian sea is one of the highest in the world it is controlled by seasonally reversing monsoonal wind driven upwelling of nutrient rich deeper waters which fuel phytoplankton growth the detailed history of upwelling induced productivity in the eastern arabian sea is unknown here we present paleoproductivity records from a composite sediment core at the millennial scale during the last 80 kyr b p these records are based on relative abundance counts of planktonic foraminifera and organic carbon contents which are shown to mainly vary in concert the eastern arabian sea upwelling induced productivity was higher in the glacial period than in the holocene but it fell repeatedly on millennial timescales these productivity declines occurred during cold events in the north atlantic region with the most pronounced changes prevailing during the heinrich events hence seasonal monsoon winds that drive upwelling induced productivity in the east were weak when the north atlantic was cold these weak winds resulted in stratification of the water column comparable to today s arabian sea stratification in the intermonsoonal period combining the new eastern with published western arabian sea results shows that the entire biological factory was severely diminished during the north atlantic heinrich events and the seasonal productivity change in the arabian sea monsoon system was reduced with year round low productivity

observational evidence for westward propagation of temperature inversions in the southeastern arabian sea 1 a warm pool forms in the southeastern arabian sea seas prior to the onset of the summer monsoon over india in early june the core of this warm pool is in the lakshadweep sea ls xbt and surface salinity data collected in the ls during may 2002 april 2003 show that temperature inversions occur off the southwest coast of india in early december with the arrival of low salinity waters from the bay of bengal the low salinity waters and the inversions propagate westward along with the downwelling rossby waves that constitute the lakshadweep sea level high inversions occur in the western ls 73 e about 40 days after they occur near the coast in the eastern ls 75 5 e they disappear in april when the tropical convergence zone moves over the seas and the warm pool engulfs the region ocean dynamics and air sea fluxes are together responsible for the formation and westward propagation of the inversions

carbonate and carbon fluctuations in the eastern arabian sea over 140 ka implications on productivity changes biological productivity in the western arabian sea was higher during interglacial than glacial times in the eastern arabian sea productivity was higher during the glacials compared to interglacials which is in sharp contrast to the southwest monsoon intensity variations to examine temporal changes in productivity in the eastern arabian sea over the last 140 ka oxygen isotopes calcium carbonate and organic carbon on three cores sl 1 4 and sk 129 cr05 were analyzed oxygen isotope records display distinct glacial and interglacial transitions in the northeastern core sl 1 and eastern arabian sea core sl 4 both calcium carbonate and organic carbon variations show no significant systematic relationship with glacial and interglacials periods in the southeastern arabian sea core sk 129 cr05 calcium carbonate shows high and low values during interglacial and glacials respectively and temporal changes in organic carbon concentration are significant only during mis 5 differential variation of calcium carbonate and organic carbon concentration at the northeastern and southeastern arabian sea and between glacials and interglacials are attributed to regional differences in sedimentation rates dilution and preservation which modify the signal of carbonate and carbon production

why is the bay of bengal less productive during summer monsoon compared to the arabian sea 1 the bay of bengal is traditionally considered to be a less productive basin compared to the arabian sea we explore the reasons for this in the central bay during summer copious rainfall and river water freshen the upper layers of the bay by 3 7 psu during summer and sst was warmer by 1 5 2 c than in the central arabian sea this leads to a strongly stratified surface layer the weaker winds over the bay are unable to erode the strongly stratified surface layer thereby restricting the turbulent wind driven vertical mixing to a shallow depth of 20 m this inhibits introduction of nutrients from below situated close to the mixed layer bottom into the upper layers while advection of nutrients rich water into the euphotic zone makes the arabian sea highly productive this process is unlikely in the bay of bengal

a bayesian approach for inversion of hydraulic tomographic data 1 hydraulic tomography is a promising methodology that shows the potential to map subsurface hydraulic properties at an unprecedented level of detail by interpreting a suite of hydraulic tests in the present work we apply the hydraulic tomography concept to a multiple pulse multiple receiver mpmr cross well configuration which consists of two boreholes subdivided into intervals by packers a short pressure or flow pulse is applied sequentially to all the intervals and for each perturbation the transient heads are recorded at the remaining intervals the resulting tomograms are inverted within the bayesian framework by using the pilot point approach in addition to the values of the hydraulic conductivity at the pilot points we assume that the stochastic parameters of the spatial variability model the structural parameters are unknown using synthetic two dimensional and three dimensional examples we demonstrate the effectiveness of the mpmr configuration and the inversion procedure for characterizing the spatial variability of the hydraulic conductivity with limited or no prior information we observed that increasing the number of source points the locations at which the pulse is alternatively applied provides more details on the spatial variability and that the parameters of the hydrogeological model of spatial variability are inferred with an acceptable although variable level of accuracy in particular the theoretical variance of the log conductivity is estimated with large errors while the estimate of the anisotropic integral scales depends on the distance between the boreholes inversion preserves the overall spatial pattern of hydraulic conductivity although low conductivity values are less connected in the inferred than in the true conductivity fields

transient hydraulic tomography in a fractured dolostone laboratory rock block experiments 1 the accurate characterization of fractured geologic medium imaging of fracture patterns and their connectivity have been a challenge for decades recently hydraulic tomography has been proposed as a new method for imaging the hydraulic conductivity k and specific storage ss distributions of fractured geologic media while encouraging results have been obtained in the field the method has not been rigorously assessed in a controlled laboratory setting in this study we assess the performance of transient hydraulic tomography tht in a fractured dolomitic rock block the block is characterized through flow through tests and multiple pumping tests the pumping test data were then analyzed with the tht code of zhu and yeh 2005 to image the fracture patterns and their connectivity through the delineation of k and ss distributions or tomograms results show that the tht analysis of pumping tests yields high k and low ss zones that capture the fracture pattern and their connectivity quite well and those patterns become more vivid as additional pumping test data are added to the inverse model the performance of the estimated k and ss tomograms are then assessed by 1 comparing the tomograms obtained from synthetic to real data 2 comparing the tomograms from two different pumping configurations 3 comparing the estimated geometric mean of the hydraulic conductivity kg from the k tomogram to the effective hydraulic conductivity keff estimated from the flow through tests and 4 predicting five independent pumping tests not used in the construction of the k and ss tomograms the performance assessment of the k and ss tomograms reveals that tht is able to image high k and low ss zones that correspond to fracture locations in the fractured rock block and that the tomograms can be used to predict drawdowns from pumping tests not used in the construction of the tomograms with reasonable fidelity

last glacial interglacial productivity and associated changes in the eastern arabian sea abstract we reconstruct paleo productivity and bottom water oxygenation changes during the past 32 ka from the southeastern arabian sea using absolute abundance of planktic foraminifera relative abundance of globigerina bulloides angular asymmetrical benthic foraminifera aabf measurements of total organic carbon c org caco 3 and globigerinoides ruber 18 o and 13 c the faunal and geochemical proxies suggest that productivity in the southeastern arabian sea was high during mis 3 a distinct decrease in productivity is inferred during the last glacial maximum 19 23 ka lgm bottom water was well oxygenated during mis3 only to become oxygen depleted during the lgm productivity decreased abruptly during heinrich stadial 1 hs 1 but the response to heinrich stadial 2 hs 2 was different low productivity during the early deglaciation is also synchronous with an increase in ice volume corrected 18 o 18 o sw ivc a salinity proxy between 18 9 18 3 18 9 ka bp and 15 9 15 0 16 3 ka bp and a concomitant decrease in 13 c between 18 2 17 5 18 7 ka bp and 16 4 15 3 16 7 ka bp these patterns suggest that the global 13 c minimum event during the last deglaciation was associated with the weak monsoon interval during hs 1 and a drop in productivity in tropical regions a progressive increase in productivity is observed throughout the holocene with a distinct jump at 5 4 3 8 6 3 ka bp we infer that although productivity was higher in the eastern arabian sea during most of the last glacial interval the overall resultant carbon sequestration was confined only to a restricted zone and not large enough to substantially alter atmospheric co 2

the cause of carbon isotope minimum events on glacial terminations the occurrence of carbon isotope minima at the beginning of glacial terminations is a common feature of planktic foraminifera carbon isotopic records from the indo pacific sub antarctic and south atlantic we use the 13 c record of a thermocline dwelling foraminifera neogloboquadrina dutertrei and surface temperature estimates from the eastern equatorial pacific to demonstrate that the onset of 13 c minimum events and the initiation of southern ocean warming occurred simultaneously timing agreement between the marine record and the 13 c minimum in an antarctic atmospheric record suggests that the deglacial events were a response to the breakdown of surface water stratification renewed circumpolar deep water upwelling and advection of low 13 c waters to the convergence zone at the sub antarctic front on the basis of age agreement between the absolute 13 c minimum in surface records and the shift from low to high 13 c in the deep south atlantic we suggest that the 13 c rise that marks the end of the carbon isotope minima was due to the resumption of north atlantic deep water influence in the southern ocean

fluxes of planktic foraminifera in response to monsoonal upwelling on the somalia basin margin abstract sediment trap samples collected off somalia bi weekly from early june 1992 through mid february 1993 show large seasonal variations in the shell flux and species composition of planktic foraminifera these variations mirror the monsoon driven circulation which resulted in massive upwelling and offshore eddy transport in summer during the sw monsoon june september and accounted for nearly 90 of the estimated annual shell flux of planktic foraminifera g bulloides dominated the sw monsoon along with g glutinata t quinqueloba n dutertrei and t iota in a fauna rich species but with a low diversity and equitability during the autumn intermonsoon november december the ocean became stratified and the nutrient exhausted whereas during the ne monsoon january march a warm surface mixed layer developed with the nutrients entrained by deep wind mixing it was dominated by g ruber in association with g tenella g aequilateralis g trilobus g sacculifer and g menardii in a fauna poorer in species but with a higher diversity and equitability consequently the ratio in the abundance of g bulloides and g ruber follows the monsoonal cycle closely as both species persist throughout the year only the rare g theyeri seems to be restricted to the sw monsoon in october at the end of the sw monsoon the trap at 265 m above the bottom intercepted massive amounts of fine grained carbonate m resuspended from the shelf and upper slope it contained extreme fluxes of bioclastic fragments benthic foraminifera and benthic ostracods as well as enhanced fluxes of small sized planktic foraminifera m notably g rubescens integrated over the year the species composition intercepted by the trap shows a very good match with the shell fauna in a core top sediment from the same site apparently the year estimated monsoonal record of planktic foraminifera which is strongly dominated by the sw monsoon production survives burial intact consequently the species composition of planktic foraminifera and measures such as the bulloides ruber ratio can be applied as a proxy for past changes in the intensity of the sw monsoon off somalia compared to the modern condition

variations in δ13c values of sedimentary organic matter since late miocene time in the indus fan iodp site 1457 of the eastern arabian sea

primary production in the arabian sea during the last 135 000 years abstract variations in primary productivity pp have been reconstructed in eutrophic mesotrophic and oligotrophic parts of the arabian sea over the past 135 000 years applying principal component analysis and transfer function to planktic foraminiferal assemblages temporal variation in paleoproductivity is most pronounced in the mesotrophic northern nast site and oligotrophic eastern east site arabian sea and comparatively weak in the western eutrophic geob 3011 1 site in the upwelling area off oman higher pp during interglacials 250 320 g c m 2 year 1 than during cold stages 210 270 g c m 2 year 1 at geob 3011 1 could have been caused by a strengthened upwelling during intensified summer monsoons and increased wind velocities at nast during interglacials pp is estimated to exceed 250 g c m 2 year 1 and during glacials to be as low as 140 180 g c m 2 year 1 these fluctuations may result from a 1 varying impact of filaments that are associated to the oman coastal upwelling and 2 from open ocean upwelling associated to the findlater jet at east highest productivity of about 380 g c m 2 year 1 is documented for the transition from isotope stage 5 to 4 we suggest that during isotope stages 2 4 5 2 the transition 5 4 and the end of stage 6 deep mixing of surface waters was caused by moderate to strong winter monsoons and induced an injection of nutrients into the euphotic layer leading to enhanced primary production the deepening of the mixed layer during these intervals is confirmed by an increased concentration of deep dwelling planktic foraminiferal species a high productivity event in stage 3 displayed by estimated pp values and by planktic foraminifera and radiolaria flux and accumulation rate likely resulted from a combination of intensified sw monsoons with moderate to strong ne monsoons differential response of globigerina bulloides globigerinita glutinata and mixed layer species to the availability of food is suited to subdivide productivity regimes on a temporal and spatial scale

abrupt climate induced changes in carbonate burial in the arabian sea causes and consequences we present high resolution records of aragonite contents and pteropods abundance in two sediment cores sk 17 and md 76 131 within the oxygen minimum zone omz of the eastern arabian sea we show large increases in aragonite contents during glacial and particularly during stadials heinrich events using aragonite content pteropods abundance organic carbon percentage and abundance of fertile species of planktonic foraminifer we demonstrate that aragonite contents in the eastern arabian sea primarily reflects preservation linked to the deepening of aragonite compensation depth acd in the arabian sea we show that these aragonite preservation events correspond with time equivalents of henrich events when arabian sea experienced large declines in monsoon driven productivity and greater penetration of antarctica intermediate water aaiw into the arabian sea thus pteropod preservation in the arabian sea appears to be the result of rapid climate change through atmospheric and oceanic teleconnections we suggest that the role of aragonite carbonate production and burial in margins and the resultant co2 climate feedback to rapid climate changes remains poorly constrained

origin and consequences of cyclic ice rafting in the northeast atlantic ocean during the past 130 000 years deep sea sediment cores recovered from the northeast atlantic ocean were examined in order to elucidate the influence of the earth s orbital parameters on major ice rafting analyses of coarse grained ice rafted debris and planktonic foraminifers revealed a strong reaction to the precession signal since 130 000 yr b p dropstone layers have been deposited each half period of a precessional cycle 11 000 1000 yr ice rafting occurs during times of winter minimum summer maximum insolation and summer minimum winter maximum insolation in the first case high summer insolation forces meltwater discharge from the ice sheets into the polar seas which subsequently enhances formation of sea ice during the winter in the second case growth of continental ice enhances iceberg production which also leads to a salinity reduction of surface seawater both situations result in a southward penetration of polar water thus the marine record of dropstones documents ice rafting not only during weichselian stades but also during cold events within interstades the regularity of ice rafting yields a useful framework to calibrate and elucidate climatic changes not only in the region of the north atlantic ocean but also in remote areas such as the pacific ocean and the antarctic

paleoproductivity in the equatorial indian ocean for the last 260 000 yr a transfer function based on planktonic foraminifera a principal component analysis pca of planktonic foraminifera in surface sediment of the northern equatorial indian ocean defines two major assemblages the first one dominated by globigerinoides sacculifer g ruber globigerinella aequilateralis and globoquadrina conglomerata characterizes non upwelling areas the second dominated by globigerina bulloides g falconensis and globigerinita glutinata characterizes upwelling areas the distribution of planktonic foraminiferal species in the area is mainly related to primary production pp the pca applied to core md 900963 samples defines an alternation of the two assemblages through time a non upwelling one similar to that present in the core tops and an upwelling assemblage which contains in addition neogloboquadrina dutertrei globorotalia menardii and g crassaformis equatorial indian ocean core top samples are introduced as additional rows in the pca calculated on core md 900963 samples and a transfer function is constructed correlating factorial coordinates of core tops within the range of changes occurring in core md 900963 with estimated pp values applied to the last 260 000 yr the transfer function indicates that the precession is the major orbital forcing on equatorial productivity changes and that annual pp increases by about 85 from interglacial to glacial interstadials these results are in agreement with an independent productivity index based on coccoliths direct impact of insolation on equatorial productivity could be explained by the link between southern oscillation and intensity of zonal winds which seem to lead the productivity of surface waters at the location of core md 900963

truncated higher order sequences as responses to compressive intraplate tectonic events superimposed on eustatic sea level rise abstract high resolution sequence stratigraphic analysis of the lignite bearing miocene siliciclastic sequence of the salotarjan lignite formation slf has been performed by lithostratigraphic dissection of more than 1350 boreholes and by detailed analysis of well logs from more than 150 boreholes biostratigraphic data indicate that the slf represents a single 3rd order eustatic sequence namely the bur 4 of vakarcs et al vakarcs g hardenbol j abreu v s vail p r varnai p tari g 1998 oligocene middle miocene depositional sequences of the central paratethys and their correlation with regional stages sepm special publication vol 60 209 231 as for facies conditions facies models for sandy shorefaces and or wave dominated deltas can be applied twenty six parasequences have been identified and mapped in the adjacent sub basins from well log correlations the sharp based sand bodies of ps 10 and 17 were interpreted as the falling stage systems tract fsst of higher order sequences the subsequent transgressive systems tracts tst are represented by retrograding sets of 2 3 parasequences ps 11 13 18 19 based on the regional unconformity at the base and the regionally extended sharp based sand bodies three sequence boundaries sb were determined that dissect the 3rd order sequence into three higher order sequences one of the special features of the sequence is that the fssts interrupt the rapid relative sea level rises ps 9 and 16 and lie directly on the silty material of nearshore environments leading to the lack of the higher order highstand system tracts hst truncated transgressive semi cycles another characteristic is the striking basinward fore stepping of the sedimentary depocentres and that of the facies belts of the lignite seams the rapid relative sea level falls implied by the two fssts are unexpected in the context of an overall eustatic rise thus the possibility of tectonic origin of shallowing was investigated this verification was based primarily on the observations that 1 the basin was united when parasequences 1 to 13 were developed whereas 2 by the end of the sequence development the palaeozoic basement protruded to the surface dividing the basin reflecting intense tectonic events simultaneous with sequence development the fssts with the sbs above and the formation of higher order sequences can thus be regarded as sedimentary responses to syn sedimentary tectonic elevation and tilting of the basement this elevation was induced by tectonic compression and associated imbrication along a regional reverse fault that was known as the darno line the imbrication could have controlled not only the repeated relative sea level falls but also the striking fore stepping of the sedimentary depocentres and facies belts of the associated lignite seams tectonic tilting influenced not only the fssts but the subsequent early tsts as well thus lignite seams associated with the tectonically counteracted tsts are characterized by multiple seams with several accessory seams va iiia b and ia while those associated with tectonically quiescent periods are aerially extensive and solitary comparison with other coal bearing formations enhanced the importance of the fsst in the interpretation of stratigraphic truncations coal seam geometry conditions facies shiftings and stratal geometry enabling a more accurate description of syn sedimentary tectonic events

testing the hydrological coherence of high resolution gridded precipitation and temperature data sets testing the hydrological coherence of high resolution gridded precipitation and temperature data sets

links between iron supply marine productivity sea surface temperature and co2 over the last 1 1 ma received 3 july 2008 revised 9 october 2008 accepted 27 october 2008 published 14 february 2009 1 paleoclimatic reconstructions have provided a unique data set to test the sensitivity of climate system to changes in atmospheric co2 concentrations however the mechanisms behind glacial interglacial g ig variations in atmospheric co2 concentrations observed in the antarctic ice cores are still not fully understood here we present a new multiproxy data set of sea surface temperatures sst dust and iron supply and marine export productivity from the marine sediment core ps2489 2 odp site 1090 located in the subantarctic atlantic that allow us to evaluate various hypotheses on the role of the southern ocean so in modulating atmospheric co2 concentrations back to 1 1 ma we show that antarctic atmospheric temperatures are closely linked to changes in so surface temperatures over the last 800 ka and use this to synchronize the timescales of our marine and the european project for ice coring in antarctica epica dome c edc records the close correlation observed between iron inputs and marine export production over the entire interval implies that the process of iron fertilization of marine biota has been a recurrent process operating in the subantarctic region over the g ig cycles of the last 1 1 ma however our data suggest that marine productivity can only explain a fraction of atmospheric co2 changes up to around 40 50 ppmv occurring at glacial maxima in each glacial stage in this sense the good correlation of our sst record to the edc temperature reconstruction suggests that the initial glacial co2 decrease as well as the change in the amplitude of the co2 cycles observed around 400 ka was most likely driven by physical processes possibly related to changes in antarctic sea ice extent surface water stratification and westerly winds position

planktonic foraminifera of the northern indian ocean distribution and preservation in surface sediments in the northern indian ocean planktonic foraminiferal tests accumulate in a wide variety of surface water environments and depositional settings this variability enables us to isolate the effects that surface water ecology and differential dissolution have on the distribution of planktonic foraminifera from 251 geographically widespread surface sediment samples foraminiferal abundance varies from 0 to 104 whole foraminifera in the greater than 150 m fraction per gram dry sediment values 10 characterize the three deep basins of the equatorial indian ocean and the western bay of bengal foraminiferal tests are most abundant on carbonate covered ninety east and carlsberg ridges absolute abundance patterns are mainly controlled by non ecological processes variations in dissolution resistant species rsp with water depth reveal that the foraminiferal lysocline fl varies regionally the fl is deepest 3 800 m in the equatorial region rises abruptly to 3 300 m in the arabian sea and varies from 2 600 m to near 2 000 m moving northward in the bay of bengal deep samples with anomalously low rsp 30 suggest redeposition systematic geographic and depth related variation is observed for the 17 most abundant foraminiferal species dissolution resistant species g menardii g tumida g dutertrei p obliquiloculata generally exhibit a rapid and continuous increase in relative abundance at and below the fl susceptible species g ruber g bulloides g glutinata for example exhibit a rapid and continuous decrease in relative abundance at and below the fl moderately susceptible species g conglobatus g aequilateralis g conglomerata for example rapidly increase in abundance at the fl and systematically decrease with depth below the fl principal components analysis pca of faunal data from minimally dissolved 30 rsp samples reveals important ecologically related species intercorrelations the major biogeographic gradient is the negative covarying relationship between ag bulloides g glutinata species pair and a grouping ofg sacculifer g conglobatus g aequilateralis andg ruber pca of all samples demonstrates how differential dissolution alters this and other species relationships species groupings that incorporateg ruber g menardii andg dutertrei are particularly affected by dissolution comparison of average faunal data from minimally dissolved samples in the northern indian ocean with similar samples from other tropical regions suggests varying environmental factors produce distinct faunas within the tropical ocean for example g bulloides g falconensis andg hexagona are significantly more abundant in northern indian ocean surface sediments while such species asg ruber g sacculifer g dutertrei andp obliquiloculata dominate in other tropical regions

a quantitative approach for identifying plant ecogroups in the romanian early jurassic terrestrial vegetation abstract community level ecology is considered to support significantly the recognition of the ecological status of plant taxa and the identification of plant ecogroups thus it generally provides extended data sets on the spatial and temporal changes of ecological factors since research based exclusively on plant structure and their supposed adaptation to the environment is now considered inadequate statistical methods can be used assuming that co occurrence of plant fossils on a single hand specimen in the case of autochthonous or parautochthonous floras is the result of their growth in the same phytocenosis quantitative ecological analysis on mesozoic materials would yield significant insights in this paper statistical and multivariate quantitative analyses of early jurassic plant fossil records from the steierdorf formation in anina south carpathians romania are presented four palaeoecological groups of taxa were distinguished by principal component analysis pca and interpreted as plant assemblages of various palaeobiotopes associated with the sedimentary facies of the enclosing formation a group of samples was analysed using the principal coordinate pco method and the statistical significance p less than or equal to 0 05 p 0 05 of individual binary responses of taxa along the first two pco ordination axes was tested by general linear model glm they revealed putative palaeoecological gradients axis 1 disturbance caused by water level fluctuations axis 2 temperature corresponding with the already assumed environmental and climatic change at the hettangian sinemurian boundary multivariate analyses enabled the identification of palaeoecological groups and thus inferring palaeogeographical conditions based on mesozoic materials

early to late holocene contrast in productivity omz intensity and calcite dissolution in the eastern arabian sea the oxygen minimum zone omz is a potential source of co2 to the atmosphere and the extensive omz spread to 1 37 106 km2 in the northern arabian sea would be an important contributor to the co2 budget in this perspective we report here that the eastern arabian sea experienced coeval increase in productivity and denitrification from 7 to 0 kyr which coincides with minimum dissolved oxygen levels in bottom waters in addition during the same period an increased calcium carbonate dissolution occurred as evidenced by low caco3 content decreasing shell weights of planktonic foraminifer species globigerinoides ruber with well marked dissolution features on their shells therefore this study has implications on the role of omz in governing caco3 dissolution and contributing to an increase in atmospheric co2

reconstruction of palaeo depositional environment in north eastern arabian sea a sediment gravity core recovered from the north eastern arabian sea was investigated for sediment grain size total organic carbon toc and selected trace metals to understand the changes in the depositional environment over time the core exhibited three distinct zones of sediment the lower zone i middle zone ii and upper zone iii representing the varying conditions of sediment deposition the lower zone is dominated by the silt sized fraction with low organic carbon that revealed a shallow depositional environment and led to oxidation of organic matter while the low metal concentration in this zone was either due to the low intensity of monsoon or the dilution by biogenic components and aeolian sediment influx on other hand the middle zone represented a transition phase where metal along with clay and organic carbon concentration started increasing due to strengthening monsoon intensity further the upper zone that represented the holocene sediments pointed to the increase in concentration of metals al fe co and cu that indicated an increase in the intensity of the south west monsoon and led to large fluvial inputs toc also increased towards the surface indicating an increase in productivity that was controlled by south west monsoon

improved predictions of saturated and unsaturated zone drawdowns in a heterogeneous unconfined aquifer via transient hydraulic tomography laboratory sandbox experiments summary interpretation of pumping tests in unconfined aquifers has largely been based on analytical solutions that disregard aquifer heterogeneity in this study we investigate whether the prediction of drawdown responses in a heterogeneous unconfined aquifer and the unsaturated zone above it with a variably saturated groundwater flow model can be improved by including information on hydraulic conductivity k and specific storage s s from transient hydraulic tomography tht we also investigate whether these predictions are affected by the use of unsaturated flow parameters estimated through laboratory hanging column experiments or calibration of in situ drainage curves to investigate these issues we designed and conducted laboratory sandbox experiments to characterize the saturated and unsaturated properties of a heterogeneous unconfined aquifer specifically we conducted pumping tests under fully saturated conditions and interpreted the drawdown responses by treating the medium to be either homogeneous or heterogeneous we then conducted another pumping test and allowed the water table to drop similar to a pumping test in an unconfined aquifer simulations conducted using a variably saturated flow model revealed 1 homogeneous parameters in the saturated and unsaturated zones have a difficult time predicting the responses of the heterogeneous unconfined aquifer 2 heterogeneous saturated hydraulic parameter distributions obtained via tht yielded significantly improved drawdown predictions in the saturated zone of the unconfined aquifer and 3 considering heterogeneity of unsaturated zone parameters produced a minor improvement in predictions in the unsaturated zone but not the saturated zone these results seem to support the finding by mao et al 2011 that spatial variability in the unsaturated zone plays a minor role in the formation of the s shape drawdown time curve observed during pumping in an unconfined aquifer

rock magnetic records of the sediments of the eastern arabian sea evidence for late quaternary climatic change abstract rock magnetic measurements along with grain size acid insoluble residue air organic carbon oc caco3 and 18o of the planktonic foraminifers of the sediments were determined for 15 gravity cores recovered from the western continental margin of india magnetic susceptibility ms values in the surficial sediments reflect the land derived input and in general are the highest in terrigenous sediment dominated sections of the cores off saurashtra ratnagiri followed by the sediments off indus gulf of kachchh and then mangalore cape comorin the down core variations in mineral magnetic parameters reveal that the glacial sediments off the indus are characterized by low ms values s ratios associated with high air content low oc caco3 contents and relatively high 18o values while those off sw india are characterized by low ms values high s ratio associated with low air content and relatively high oc caco3 and 18o values conversely the early holocene sediments of all cores are characterized by high ms values s ratio associated with high air content low oc caco3 contents and gradually decreased 18o values these results imply that during the last glacial maximum lgm the cores off northwestern india received abundant continental supply leading to the predominance of eolian fluvial sedimentation in the sw region the influence of hinterland flux is less evident during this period but convective mixing associated with the ne monsoon resulted in increased productivity during the early holocene intense sw monsoon conditions resulted in high precipitation on land which in turn contributed increased air content ms values in the continental margin sediments a shallow water core off kochi further suggests that the intense sw monsoon conditions prevailed until about 5 ka the late holocene organic rich sediments of the sw margin of india were however subjected to early diagenesis at different intervals in the cores therefore caution is needed when interpreting regional climatic change from down core changes in sediment magnetic properties

detrital sr nd isotopes sediment provenances and depositional processes in the laxmi basin of the arabian sea during the last 800 ka 87sr 86sr ratios and end values of detrital particles at international ocean discovery program iodp site u1456 in the laxmi basin of the arabian sea were measured to trace changes in sediment provenance over glacial interglacial cycles based on the correlation of planktonic foraminiferal globigerinoides ruber 18o fluctuations with the lr04 stack of benthic foraminifera 18o values combined with shipboard biostratigraphic and palaeomagnetic data the studied interval spans 1 2 ma over the past 800 ka 87sr 86sr values ranged from 0 711 to 0 726 while end values ranged between 12 5 and 7 3 in the detrital particles by comparing 87sr 86sr ratios and end values of the possible sources of river sediments with our data we found that sediments in the laxmi basin were influenced to various degrees by proportions of at least three sediment sources i e tapi river narmada river and indus river the indus river might be a more important contributor to glacial sediments although 87sr 86sr ratios and end values varied quasi cyclically this pattern did not correspond precisely to the glacial interglacial cycles in particular low magnetic susceptibility low ms intervals coinciding with pelagic carbonates were characterized by low 87sr 86sr ratios and high end values whereas high ms intervals matching turbidite deposits showed high 87sr 86sr ratios and low end values thus this study reveals that differences in the depositional processes between glacial and interglacial periods governed by changes in sea level and monsoon activity are an important factor in deciding 87sr 86sr ratios and end values of the detrital fraction in the indus fan of the arabian sea

late holocene long arid phase in the indian subcontinent as seen in shallow sediments of the eastern arabian sea abstract multi proxy record of benthic and planktic foraminifera total organic carbon and carbon and oxygen isotope ratios from core sk291 gc15 off the coast of goa eastern arabian sea reveals significant paleoceanographic and paleoclimatic turnovers during 6000 to 1700 calibrated years before the present cal yr bp benthic foraminiferal census data was analyzed with multivariate techniques including factor and cluster analyses of highest ranked species from the studied core that enabled to identify seven biofacies the record suggests centennial to millennial scale changes in the surface conditions driven by monsoon linked upwelling in the eastern arabian sea during the studied interval various benthic biofacies combined with isotope and planktic foraminiferal data suggest that depletion of dissolved oxygen and increase in organic productivity in the study area was caused by intense monsoonal upwelling since the middle holocene the results suggest that during 5400 4700 and 3000 2500 cal yr bp the southwest sw monsoon was strong leading to intense upwelling in the study area as reflected by increased globigerina bulloides percentages these were generally warmer intervals in the northern hemisphere the sw monsoon significantly weakened abrupt decrease in g bulloides population during 4700 3400 cal yr bp roughly coinciding with a long arid phase in the indian subcontinent and a cold interval in europe our record suggests an abrupt increase in sw monsoon intensity during 3000 to 2500 cal yr bp when a pronounced change in benthic biofacies is also noted that suggests a major shift in the sub surface conditions our data document a prolong weak sw monsoon phase beginning at 4600 cal yr bp little earlier than 4 2 ka event in the eastern arabian sea

glacial interglacial co2 change the iron hypothesis several explanations for the 200 to 280 ppm glacial interglacial change in atmospheric co2 concentrations deal with variations in southern ocean phytoplankton productivity and the related use or nonuse of major plant nutrients an hypothesis is presented herein in which arguments are made that new productivity in today s southern ocean 7 4 1013g yr 1 is limited by iron deficiency and hence the phytoplankton are unable to take advantage of the excess surface nitrate phosphate that if used could result in total southern ocean new production of 2 3 1015 g c yr 1 as a consequence of fe limited new productivity holocene interglacial co2 levels preindustrial are as high as they were during the last interglacial 280 ppm in contrast atmospheric dust fe supplies were 50 times higher during the last glacial maximum lgm because of this fe enrichment phytoplankton growth may have been greatly enhanced larger amounts of upwelled nutrients may have been used and the resulting stimulation of new productivity may have contributed to the lgm drawdown of atmospheric co2 to levels of less than 200 ppm background information and arguments in support of this hypothesis are presented

intense reducing conditions during the last deglaciation and heinrich events h1 h2 h3 in sediments from the oxygen minimum zone off goa eastern arabian sea abstract two sediment cores abp 32 gc 01r and abp 32 gc 03 were collected at a water depth of 642 m and 1086 m off goa from the present day oxygen minimum zone omz of eastern arabian sea eas cover time span of last 18 ka and 32 ka respectively were analysed for multi proxy redox sensitive elements to understand the variation in the redox conditions and factors responsible for its development redox sensitive elements concentration and their normalized ratios mn al u th mo al and ce ce suggest that sediment core abp 32 gc 01r is under more reducing conditions due to its location within the centre of omz compared to core abp 32 gc 03 which is at the base of omz sediments from the eas are of non euxinic environments where dissolved sulfide is present but restricted to the sediment pore waters lack of significant correlation r n yb n ratio is 1 during the last 10 ka holocene 14 10 ka includes younger dryas and b lling aller d 18 14 ka last deglaciation and heinrich events suggesting less reducing terrigenous dominated and intense reducing condition respectively

sea surface temperature pattern reconstructions in the arabian sea from throughout the arabian sea for four distinct time intervals 0 ka 8 ka 15 ka and 20 ka with the aim of understanding the history of the indian monsoon and the climate of the arabian sea region this was accomplished through the use of paired mg ca and d 18 o measurements of the planktonic foraminifer globigerinoides ruber by analyzing basin wide changes and changes in cross basinal gradients we assess both monsoonal and regional scale climate changes sst was colder than present for the majority of sites within all three paleotime slices furthermore both the indian monsoon and the regional arabian sea mean climate have varied substantially over the past 20 kyr the 20 ka and 15 ka time slices exhibit average negative temperature anomalies of 2 5 3 5 c attributable in part to the influences of glacial atmospheric co2 concentrations and large continental ice sheets the elimination of the cross basinal sst gradient during these two time slices likely reflects a decrease in summer monsoon and an increase in winter monsoon strength changes in d 18 ow that are smaller than the d 18 o signal due to global ice volume reflect decreased evaporation and increased winter monsoon mixing ssts throughout the arabian sea were still cooler than present by an average of 1 4 ci n the 8 ka time slice these cool ssts along with lower d 18 ow throughout the basin are attributed to stronger than modern summer and winter monsoons and increased runoff and precipitation the results of this study underscore the importance of taking a spatial approach to the reconstruction of processes such as monsoon upwelling

surface and deep water variations in the northeast indian ocean during 34 6 ka bp evidence from carbon and oxygen isotopes of fossil foraminifera abstract 13c and 18o records from planktic globigerinoides ruber and benthic foraminifera cibicides spp were obtained from a deep sea sediment core sk157 18 collected in the central bay of bengal the chronology of this gravity core 11 59 n 90 01 e water depth 3069 m core length 230 cm has been established using six radiocarbon ages large variations in carbon and oxygen isotopes are suggestive of significant changes in surface and deep water of the bay of bengal during 34 6 ka bp planktic 18o values in core sk157 18 are significantly higher compared to cores in the western bay of bengal and the andaman sea a marked 18o decrease at 8 7 ka bp is suggestive of low salinity surface water in the central bay of bengal probably due to the intensification of the indian southwest monsoon ism an increasing 13c trend in g ruber is seen during 34 26 and 14 7 ka bp and decreasing 13c trend between 26 and 15 ka bp intervals however these 13c shifts in planktic foraminifera are not coherent with the glacial interglacial change and may have been caused by wind induced variability in surface water 13c the 18o and 13c values in benthic foraminifera show considerable variations during the holocene and glacial times last glacial maximum lgm to holocene 18o shift in benthic foraminifera 1 5 exceeds ice volume effect by 0 5 suggesting glacial deep water cooling of 2 c assuming no salinity change this glacial deep water cooling may have been caused by the introduction of cooler southern ocean deep water sodw large fluctuations in benthic 13c are due to the changes in source water characteristics during the holocene and last glaciation glacial benthic foraminifera exhibit pronounced decrease in 13c suggesting reduced contribution from the north atlantic deep water nadw and increased influx of sodw in addition oxidation of organic matter due to the reduced ventilation of deep water masses during the lgm may have contributed in the significant decrease in 13c

palaeoproductivity and associated changes in the north eastern indian ocean since the last glacial evidence from benthic foraminifera and stable isotopes abstract here we present the first detailed planktonic and benthic 13c records and benthic foraminiferal assemblage records from the north eastern indian ocean to decipher the palaeoceanographic changes during the last 56 kyr we identified three different palaeoceanographic stages clearly differentiated by significant variations in the benthic foraminiferal assemblages and 13c records the results of this study indicate that productivity was generally higher during the glacial periods than during the holocene comparison of the benthic foraminiferal assemblage distributions and planktonic and benthic 13c records show a significant correlation between productivity and the bottom water oxygenation on glacial interglacial timescales productivity gradually increased during the period between 56 and 27 5 kyr during this period the dominance of melonis spp and oridosalis umbonatus were correlated with conditions of intermediate to high surface productivity and moderate bottom water oxygenation increased higher equatorial productivity and low bottom water oxygenation during the period between 27 5 and 15 kyr are supported by planktonic 13c and faunal records during this period the dominance of benthic foraminifera assemblages characterised by uvigerina peregrina indicates sustained continuous phytodetritus flux to the seafloor from enhanced surface water productivity and relatively low bottom water oxygenation the absence or minimal occurrences of high productivity indicating u peregrina the dominance of intermediate to low productivity indicating fauna and relatively low planktonic 13c records suggest low productivity and active deep water oxygenation after 15 kyr concurrent river discharge and rising sea levels during this period are indicated by negative 18o of g ruber at the site

ice age terminations 230th dated oxygen isotope records of stalagmites from sanbao cave china characterize asian monsoon am precipitation through the ends of the third and fourthmost recent ice ages as a result am records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments establishing the timing and sequence of major events in all four cases observations are consistent with a classic northern hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets meltwater and icebergs entering the north atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon causing increases in atmospheric co2 and antarctic temperatures that drive the termination in the southern hemisphere increasing co2 and summer insolation drive recession of northern ice sheets with probable positive feedbacks between sea level and co2

planktonic foraminiferal and alkenone records of the last deglaciation from the eastern arabian sea the oxygen isotope record of planktonic foraminifera from tropical core md77194 eastern arabian sea exhibits a clear two step deglaciation with a brief 18o transient event in the tropics this 18o maximum could correspond to a cooling or to a change in the 18o content of sea water in this study past sea surface temperature sst and primary production pp are reconstructed from foraminiferal transfer functions and compared to values estimated from alkenone measurements sst and pp records from both proxies indicate a 1 5 2 5 c deglacial warming coupled with a pp decrease and a 0 5 1 c cooling during the younger dryas yd a detailed comparison between independent micropaleontological and geochemical proxies helps us identify potential biases and thus strengthen the paleo reconstructions

carbon isotope constraints on the deglacial co2 rise from ice cores the stable carbon isotope ratio of atmospheric co2 13catm is a key parameter in deciphering past carbon cycle changes here we present 13catm data for the past 24 000 years derived from three independent records from two antarctic ice cores we conclude that a pronounced 0 3 per mil decrease in 13catm during the early deglaciation can be best explained by upwelling of old carbon enriched waters in the southern ocean later in the deglaciation regrowth of the terrestrial biosphere changes in sea surface temperature and ocean circulation governed the 13catm evolution during the last glacial maximum 13catm and atmospheric co2 concentration were essentially constant which suggests that the carbon cycle was in dynamic equilibrium and that the net transfer of carbon to the deep ocean had occurred before then

should hydraulic tomography data be interpreted using geostatistical inverse modeling a laboratory sandbox investigation the robust performance of hydraulic tomography ht based on geostatistics has been demonstrated through numerous synthetic laboratory and field studies while geostatistical inverse methods offer many advantages one key disadvantage is its highly parameterized nature which renders it computationally intensive for large scale problems another issue is that geostatistics based ht may produce overly smooth images of subsurface heterogeneity when there are few monitoring interval data therefore some may question the utility of the geostatistical inversion approach in certain situations and seek alternative approaches to investigate these issues we simultaneously calibrated different groundwater models with varying subsurface conceptualizations and parameter resolutions using a laboratory sandbox aquifer the compared models included 1 isotropic and anisotropic effective parameter models 2 a heterogeneous model that faithfully represents the geological features and 3 a heterogeneous model based on geostatistical inverse modeling the performance of these models was assessed by quantitatively examining the results from model calibration and validation calibration data consisted of steady state drawdown data from eight pumping tests and validation data consisted of data from 16 separate pumping tests not used in the calibration effort results revealed that the geostatistical inversion approach performed the best among the approaches compared although the geological model that faithfully represented stratigraphy came a close second in addition when the number of pumping tests available for inverse modeling was small the geological modeling approach yielded more robust validation results this suggests that better knowledge of stratigraphy obtained via geophysics or other means may contribute to improved results for ht

interhemispheric atlantic seesaw response during the last deglaciation the asynchronous relationship between millennial scale temperature changes over greenland and antarctica during the last glacial period has led to the notion of a bipolar seesaw which acts to redistribute heat depending on the state of meridional overturning circulation within the atlantic ocean here we present new records from the south atlantic that show rapid changes during the last deglaciation that were instantaneous within dating uncertainty and of opposite sign to those observed in the north atlantic our results demonstrate a direct link between the abrupt changes associated with variations in the atlantic meridional overturning circulation and the more gradual adjustments characteristic of the southern ocean these results emphasize the importance of the southern ocean for the development and transmission of millennial scale climate variability and highlight its role in deglacial climate change and the associated rise in atmospheric carbon dioxide

the marine record of the onset of farming around the arabian sea at the dawn of the bronze age the rise and fall of human cultures are strongly modulated by the strong environmental changes taking place during the holocene here we use the sedimentological and geochemical records of a core

characterization of aquifer heterogeneity using transient hydraulic tomography 1 hydraulic tomography is a cost effective technique for characterizing the heterogeneity of hydraulic parameters in the subsurface during hydraulic tomography surveys a large number of hydraulic heads i e aquifer responses are collected from a series of pumping or injection tests in an aquifer these responses are then used to interpret the spatial distribution of hydraulic parameters of the aquifer using inverse modeling in this study we developed an efficient sequential successive linear estimator ssle for interpreting data from transient hydraulic tomography to estimate three dimensional hydraulic conductivity and specific storage fields of aquifers we first explored this estimator for transient hydraulic tomography in a hypothetical one dimensional aquifer results show that during a pumping test transient heads are highly correlated with specific storage at early time but with hydraulic conductivity at late time therefore reliable estimates of both hydraulic conductivity and specific storage must exploit the head data at both early and late times our study also shows that the transient heads are highly correlated over time implying only infrequent head measurements are needed during the estimation applying this sampling strategy to a well posed problem we show that our ssle can produce accurate estimates of both hydraulic conductivity and specific storage fields the benefit of hydraulic tomography for ill posed problems is then demonstrated finally to affirm the robustness of our ssle approach we apply the ssle approach to a hypothetical three dimensional heterogeneous aquifer

quantifying carbonate dissolution and calibration of foraminiferal dissolution indices in the somali basin two sediment traps moored off somalia in 1992 1993 collected similar settling fluxes of carbonate and siliceous shells formed by various plankton groups planktic foraminifera showed large seasonal variations with more than 74 of the total planktic foraminifera flux collected during the sw monsoon summer upwelling when globigerina bulloides was dominating along with globigerinita glutinata and neogloboquadrina dutertrei the intermonsoon and ne monsoon assemblages were dominated by globigerinoides ruber we used the trap records as our no dissolution reference for comparison with three boxcore recorders in order to quantify the carbonate dissolution along a depth transect dissolution increases downslope from station 905 to 907 and 915 at depths of 1567 m 2807 m and 4035 m respectively the carbonate fraction of the sediment at station 915 which is located near the ccd is the most affected by dissolution with more than 97 of the planktic foraminifera dissolved here the planktic foraminifera assemblage is strongly modified with thick walled species such as n dutertrei globorotalia tumida and pulleniatina obliquiloculata as the most resistant it is not representative of the settling assemblage the planktic foraminiferal assemblages of the sediment surface at stations 905 and 907 remain similar to the trap assemblages and the foraminifera are well preserved although only 25 of foraminifera are apparently preserved at station 905 and 8 at station 907 those numbers are surprisingly low and infer that only a small fraction of the foraminiferal carbonate production is buried and removed from the carbon cycle this discrepancy between the export and buried flux is partly be due to bio mechanical destruction by benthic processes and to supralysoclinal dissolution due to metabolic co2 generated by the benthic organisms another important factor is the interannual variability of the productivity well known in the arabian sea the calibration of commonly used foraminiferal dissolution indices percentage of foraminiferal fragments percentage of resistant species foraminiferal dissolution index fdx to our data only shows reliable results for high dissolution levels 97 off somalia the most accurate of the proxies is the percentage of foraminiferal fragments compared to the other methods tested i e fdx planktic foraminiferal loss l percentage of radiolarians and diatoms percentage of benthic foraminifera the species assemblage appears to be not significantly modified by dissolution unless the estimated shell loss is high 92 of the arriving shells in our samples this level is expressed in the percentage of fragmentation the percentage of radiolarians and diatoms the percentage of resistant foraminifera species and fdx as 80 35 25 and 1 8 respectively the relative abundance of globigerina bulloides is a valid sw monsoon upwelling proxy only when dissolution is moderate 92 globigerina bulloides and globigerinoides ruber have similar burial efficiencies and susceptibilities to dissolution thus the ratio g bulloides g ruber is a valid proxy for past changes in the intensity of the sw monsoon even in the strongly dissolved samples in our sediment record the ratio g bulloides g ruber indicates that the sw monsoon was stronger in the recent past than in 1992 93

hydraulic conductivity imaging from 3 d transient hydraulic tomography at several pumping observation densities 1 3 d hydraulic tomography 3 d ht is a method for aquifer characterization whereby the 3 d spatial distribution of aquifer flow parameters primarily hydraulic conductivity k is estimated by joint inversion of head change data from multiple partially penetrating pumping tests while performance of 3 d ht has been studied extensively in numerical experiments few field studies have demonstrated the real world performance of 3 d ht here we report on a 3 d transient hydraulic tomography 3 d tht field experiment at the boise hydrogeophysical research site which is different from prior approaches in that it represents a baseline analysis of 3 d tht performance using only a single arrangement of a central pumping well and five observation wells with nearly complete pumping and observation coverage at 1 m intervals we jointly analyze all pumping tests using a geostatistical approach based on the quasi linear estimator of kitanidis 1995 we reanalyze the system after progressively removing pumping and or observation intervals significant progressive loss of information about heterogeneity is quantified as reduced variance of the k field overall reduced correlation with slug test k estimates at wells and reduced ability to accurately predict independent pumping tests we verify that imaging accuracy is strongly improved by pumping and observational densities comparable to the aquifer heterogeneity geostatistical correlation lengths discrepancies between k profiles at wells as obtained from ht and slug tests are greatest at the tops and bottoms of wells where ht observation coverage was lacking

variation in the indian summer monsoon intensity during the bolling allerod and holocene variations in the indian summer monsoon ism intensity during the last 16 7 ka have been studied using organic carbon corg 15 n of sedimentary organic matter caco3 sediment texture 18 oc and mg ca derived sea surface temperature 18 o of sea water and sea surface salinity in a 14 c dated sediment core from the eastern arabian sea the 18 o in water and planktonic foraminifera shells off the central west coast of india may be controlled by the ism intensity as this area receives high precipitation and land runoff also the corg and caco3 contents of sediments and 15 n of sedimentary organic matter may be linked to ism induced productivity and denitrification the results of the present study reveal that between 16 and 15 2 ka bp the ism was weak with minor fluctuations and started intensifying around 15 2 ka bp at the onset of the bolling allerod b a event the b a event is characterized by higher water column denitrification rates comparable to the present day the ism signatures observed in the 18 oc record of b a event compare well with those from timta cave of the western himalayas and also the asian summer monsoon signatures from the hulu caves in china and warming signatures in greenland ice sheet project 2 gisp2 suggesting atmospheric tele connections through intertropical convergence zone itcz the boundary between the younger dryas and the holocene is discernible with small episodes of abrupt events of increased ism intensity this decrease in 18 oc values at 11 8 ka bp is contemporary with june solar insolation maximum at 30 north and the increase in methane in the gisp2 ice core supporting episodes of warmer climate and increase in ism intensity the ism seems to have been most stable between 7 and 5 6 ka bp the core exhibits periodicity of 500 that is comparable to the atlantic water formation and the chinese monsoon

transient pumping well flow in weakly heterogeneous formations 1 the solution of pumping well flow serves for identifying aquifer s properties most results available in the literature assume homogeneous aquifers or at most stratified structures this study investigates the unsteady well flow in heterogeneous aquifers by modeling the hydraulic conductivity as a three dimensional stationary random function of axisymmetric anisotropy and gaussian correlations the main result of the investigation is the mean drawdown in a transient flow toward a fully penetrating well pumping at a constant rate the solution is obtained in terms of one quadrature over time and is easily calculated closed form approximations of the mean head are developed for moderate and large times the mean drawdowns derived in the study generalize the theis and copper and jacob distributions for aquifers of constant transmissivity it is shown that the transmissivity which is identified by using the cooper and jacob asymptotic is precisely the effective conductivity for uniform horizontal flow khefu this is compared with the finding that the equivalent conductivity for the steady state flow approaches khefu with distance from the well indelman et al 1996

benthic foraminiferal diversity response to the climate induced changes in the eastern arabian sea oxygen minimum zone during the last 30kabp abstract a high resolution record of deep sea benthic foraminiferal diversity variations in the eastern arabian sea for the last 30 ka bp was obtained from two sediment cores sk17 and md131 retrieved from the present day oxygen minimum zone omz in the indian margin off goa the benthic foraminiferal diversity is represented in terms of sander s rarefaction number s 100 shannon wiener index h s equitability e and alpha index records of diversity indices exhibit millennial scale changes during the late glacial and deglacial periods corresponding to the northern hemisphere climatic events we compared the faunal diversity with proxy records of primary productivity c org and bottom water oxygen low o 2 taxa we suggest that benthic foraminiferal diversity in the eastern arabian sea omz is largely controlled by the primary productivity induced organic carbon flux and strength of bottom water oxygenation the less diverse fauna along with increased percentages of c org and low o 2 taxa during the last glacial maximum 18 22 5 ka bp suggest eutrophic and oxygen poor benthic environment attributed mainly to a strong omz associated with intense winter monsoon wind induced productivity and a weak deep ocean circulation the intervals of distinct increase in diversity closely correspond with north atlantic cold heinrich events when eastern arabian sea experienced significant declines in monsoon driven productivity and better deep sea ventilation due to enhanced inflow of antarctic intermediate water aaiw

can benthic foraminiferal morpho groups be used as indicators of paleomonsoonal precipitation a technique is proposed for the quick and easy assessment of paleomonsoonal precipitation through the study of morphological groups of foraminifera in a shallow water 20 m water depth sediment core collected off karwar near kali river mouth central west coast of india the percentage distribution of two morpho groups i e rounded symmetrical and angular asymmetrical morpho groups showed considerable fluctuations which correlate well with the 7 years average rainfall over a period of 116 years of the catchment area of kali river the dominance of rounded symmetrical forms indicates a period of higher rainfall whereas angular asymmetrical forms tend to increase in abundance during dry periods poor monsoons the inferences drawn shown high potential in generating proxy data for paleomonsoonal precipitation required to develop predictive climatic models

coal facies studies in hungary a historical review the objective of this short summary is to provide an overview on the work of hungarian geoscientists who published their results mainly in hungarian language the aim of their studies was to understand coal formation and to make reconstruction on the different peat forming environments in addition to coal petrographical methods other investigation tools such as palynology sedimentology and organic geochemistry were applied to understand the formation accumulation and diagenesis of land derived organic matter in different geological realms and environments

iceberg discharges of the last glacial period driven by oceanic circulation changes proxy data reveal the existence of episodes of increased deposition of ice rafted detritus in the north atlantic ocean during the last glacial period interpreted as massive iceberg discharges from the laurentide ice sheet although these have long been attributed to self sustained ice sheet oscillations growing evidence of the crucial role that the ocean plays both for past and future behavior of the cryosphere suggests a climatic control of these ice surges here we present simulations of the last glacial period carried out with a hybrid ice sheet ice shelf model forced by an oceanic warming index derived from proxy data that accounts for the impact of past ocean circulation changes on ocean temperatures the model generates a time series of iceberg discharge that closely agrees with ice rafted debris records over the past 80 ka indicating that oceanic circulation variations were responsible for the enigmatic ice purges of the last ice age

oxygen isotope evidence for a stronger winter monsoon current during the last glaciation a variety of palaeoclimate data from the northern indian ocean has shown that the asian summer monsoon was weaker during the last glacial maximum 18 000 years ago than it is today1 5 it has also been inferred from these data that the winter monsoon was stronger at that time5 here we present evidence that the transport of low salinity water from the bay of bengal to the arabian sea caused by the winter monsoon6 was higher during the last glacial maximum this inference is based on a negative excursion up to about 1 in magnitude in the oxygen isotope ratios of three planktonic foraminiferal species detected in a sediment core from the arabian sea by high resolution 1 2 cm sampling our results place an upper limit of about 4 000 years on the length of time during which the winter monsoon was stronger than today

geochemical evidence for anoxic deep water in the arabian sea during the last glaciation various paleoceanographic studies have indicated that the deep ocean was probably depleted in dissolved oxygen during the last glacial period approximately 18 kyr b p delta sup 18 o stage 2 compared to present time however direct evidence of low oxygen content in the deep waters has been lacking here the authors report geochemical evidence of near anoxic conditions in the deep arabian sea during the entire last glacial cycle delta sup 18 o stages 2 3 and 4 anoxia is inferred from the concomitant enrichment of organic carbon and authigenic uranium in the glacial sections of a core from the deep eastern arabian sea the anoxic conditions during the last glacial period probably caused by a change in deep water circulation evidently enhanced preservation of organic matter and simultaneous removal of uranium from seawater 57 refs 3 figs 2 tabs

on the importance of geological data for three dimensional steady state hydraulic tomography analysis at a highly heterogeneous aquifer aquitard system abstract hydraulic tomography ht has been shown to map subsurface heterogeneity accurately through the joint interpretation of multiple pumping tests previous research has shown that smooth hydraulic conductivity k estimates are obtained beyond where pumping observation data are available using the geostatistical inversion approach when the inversion begins with a homogeneous k and when data densities are not high however geological data are typically available through outcrops and borehole logs to provide geological variability therefore we investigate the usefulness of geological data for ht analysis at a highly heterogeneous field site by 1 comparing calibrated geological models of two different resolutions to two homogeneous and four highly parameterized geostatistical inverse models in terms of both model calibration and validation performances as well as correspondence of estimated k values with permeameter estimated k profiles along boreholes and 2 using geological models as prior information for the geostatistical inversion approach results reveal that the simultaneous calibration of geological models to seven pumping test data yields k values that correctly reflect the general patterns of vertical distributions of permeameter estimated k we also find that the geostatistical inversion approach using a geological model as prior information performs better for both model calibration and validation than using a homogenous k as a prior and more importantly improves the correspondence of k estimates to permeameter test results along wells as well as in preserving geological features where drawdown measurements are lacking overall our results suggest the joint use of both geological and pumping test data for ht analysis when accurate geological data are available

influence of orographically enhanced sw monsoon flux on coastal processes along the se arabian sea 1 the arabian sea has an excess evaporation over precipitation regime the southeast arabian sea is however anomalous because it has 2800 4800 mm rainfall during the southwest monsoon swm despite a high rainfall the fluvial influence on supply of total suspended matter tsm and marine productivity is deemed insignificant and remains unevaluated we evaluated the poorly resolved influence of fluvial influx on shelf processes we documented low salinity stratification high productivity and turbidity over the entire inner shelf chlorophyll a 2 4 mg m 3 po4 3 2 5 m no3 6 8 2 1 m tsm 88 182 mg l 1 salinity near shore region 26 offshore region 33 8 34 6 p s u the deeper regions 40 m however had greatly reduced tsm and nutrient levels no3 po4 3 1 0 m tsm 24 mg l 1 and patches of high chlorophyll a upon cessation of the swm nutrient levels and tsm reduced considerable we identify two processes that contribute to the marine productivity and turbidity during the swm over the deeper regions there is a poor influence of fluvial supply and upwelling regulates productivity over the shallow inner shelf the sequestering of fluvial influx due to the prevalence of strong winds upwelling and equatorward flow is dominant the later processes induced high marine productivity and eutrophication in the near shore region and may have implications for siltation of channels reduced turbidity nutrient and chlorophyll a levels and higher salinity of the coastal waters during rest of the year imply a substantial role of fluvial fluxes on coastal processes

joint inversion in coupled quasi static poroelasticity geodetic surveys now provide detailed time series maps of anthropogenic land subsidence and uplift due to injection and withdrawal of pore fluids from the subsurface a coupled poroelastic model allows the integration of geodetic and hydraulic data in a joint inversion and has therefore the potential to improve the characterization of the subsurface and our ability to monitor pore pressure evolution we formulate a bayesian inverse problem to infer the lateral permeability variation in an aquifer from geodetic and hydraulic data and from prior information we compute the maximum a posteriori map estimate of the posterior permeability distribution and a gaussian approximation of the posterior computing the map estimate requires the solution of a large scale minimization problem subject to the poroelastic equations for which we propose an efficient newton conjugate gradient optimization algorithm the covariance matrix of the gaussian approximation of the posterior is given by the inverse hessian of the log posterior which we construct by exploiting low rank properties of the data misfit hessian first and second derivatives are computed using adjoints of the time dependent poroelastic equations allowing us to fully exploit transient data using three increasingly complex model problems we find the following general properties of poroelastic inversions augmenting standard hydraulic well data by surface deformation data improves the aquifer characterization surface deformation contributes the most in shallow aquifers but provides useful information even for the characterization of aquifers down to 1 km in general it is more difficult to infer high permeability regions and their characterization requires frequent measurement to resolve the associated short response timescales in horizontal aquifers the vertical component of the surface deformation provides a smoothed image of the pressure distribution in the aquifer provided that the mechanical properties are known coupled poroelastic inversion is therefore a promising approach to detect flow barriers and to monitor pore pressure evolution

east west similarities and differences in the surface and deep northern arabian sea records during the past 21kyr abstract this study analyses monsoon proxy globigerina bulloides from ocean drilling program odp hole 723a western arabian sea and hole abp 25 02 northeastern arabian sea as well as dominant benthic foraminifera pteropods total organic carbon toc inorganic carbon ic and stable isotope values of benthic foraminifera from hole abp 25 02 to understand summer monsoon driven changes in the western and eastern arabian sea and their impacts on deep sea ventilation during the past 21 kyr we have also combined published toc data from odp hole 724b to understand if deep sea conditions in the arabian sea were same throughout the region during the studied interval the summer monsoon was generally weaker during cold intervals including the last glacial maximum the younger dryas and the bond events of the holocene from 20 to 10 kyr the deep northeastern arabian sea was better oxygenated with less organic carbon supply except during 14 12 5 kyr when toc values increased indicating a weaker summer monsoon and a weak oxygen minimum zone omz the toc values and the abundance of the eutrophic benthic foraminiferal species bulimina aculeata melonis barleeanum and uvigerina peregrina increased during the late holocene whereas well oxygenated low organic carbon benthic species sphaeroidina bulloides as well as pteropods decreased indicating an intense omz and an increased supply of refractory organic material to the arabian sea it is important to note that although the surface response to monsoon variability was more or less similar in the western and northeastern arabian sea the deep sea conditions show a marked contrast in the two regions during the past 21 kyr

change in the intensity of low salinity water inflow from the bay of bengal into the eastern arabian sea from the last glacial maximum to the holocene implications for monsoon variations a 100 400 km wide region of the coastal eastern arabian sea eas off the west coast of india is characterized by a low salinity tongue formed by the inflow of low salinity surface water from the bay of bengal bob this low salinity tongue is largely driven by the sea level higher in bob than in the arabian sea and by alongshore pressure gradient between southern and northern eas and is expected to respond to summer monsoon freshwater flux to the bay here we report past variation in the relative intensity of summer and winter monsoons based on changes in the north south salinity gradient within this low salinity tongue the salinity gradient is estimated from paired measurement of 18 o and mg ca in globigerinoides sacculifer extracted from sediment cores collected at northern high salinity and southern low salinity locations within this tongue the last glacial maximum lgm to peak holocene 18 o and sea surface temperature gradients at both locations are 2 and 2 o c respectively while the sea surface salinity gradient at northern eas is 0 5 psu higher than in the southern eas suggesting distinctly different sss structure in the lgm eas the north south surface salinity gradient was also larger by 0 5 psu during the lgm 1 2 psu as compared to the gradient during the holocene 0 7 psu increased north south surface salinity gradient during the lgm suggests diminished flow of low salinity water into the coastal eas caused by combined effect of decreased freshening of the bob and reduced seasonal mountain rivers discharge into the eas such surface hydrographic conditions in the coastal eas clearly indicate significantly weakened summer monsoons and strengthened winter monsoons during the lgm

coupled sea surface temperature seawater δ18o reconstructions in the arabian sea at the millennial scale for the last 35 ka two sediment cores from the western 905 10 46 9 n 51 56 4 e water depth 1586 m and eastern sk17 15 15 n 72 58 e water depth 840 m arabian sea were used to study past sea surface temperatures sst and seawater 18o 18ow variations for the past 35 ka we used coupled mg ca 18o calcite variability in two planktonic foraminiferal species globigerinoides ruber which thrives throughout the year and globigerina bulloides which occurs mainly when surface waters contain high nutrients during upwelling or convective mixing ssts in both areas based on mg ca in g ruber were 3 to 4 c lower during the last glacial maximum lgm 21 ka than today and the holocene period the sst records based on g bulloides also indicate general cooling down to 18 c in both areas ssts in the western arabian sea based on g bulloides were always lower than those based on g ruber indicating the presence of strong seasonal temperature contrast during the holocene and lgm we interpret the consistent presence of this seasonal temperature contrast to reflect a combination of seasonal summer upwelling sw monsoon and winter convective mixing ne monsoon in the western arabian sea in the eastern arabian sea g bulloides based ssts were slightly lower about 1 c than g ruber based ssts during the holocene indicating the almost absence of a seasonal temperature gradient similar to today however a large seasonal temperature contrast occurred during the lgm which favors the assumption that strong ne monsoon winds forced winter upwelling or convective mixing offshore goa sst and 18ow reconstructions reveal evidence of millennial scale cycles particularly in the eastern arabian sea here the stadial periods northern hemisphere cold periods such as younger dryas and heinrich events are marked by increasing ssts and salty sea surface conditions relative to those during the interstadial periods indeed the 18ow record shows evidence of low saline surface waters during interstadial periods indicating increased freshwater runoff from the western ghats as a consequence of enhanced sw monsoon intensity

abrupt changes in the asian southwest monsoon during the holocene and their links to the north atlantic ocean during the last ice age the indian ocean southwest monsoon exhibited abrupt changes that were closely correlated with millennial scale climate events in the north atlantic region1 2 3 suggesting a mechanistic link in the holocene epoch which had a more stable climate the amplitude of abrupt changes in north atlantic climate was much smaller and it has been unclear whether these changes are related to monsoon variability here we present a continuous record of centennial scale monsoon variability throughout the holocene from rapidly accumulating and minimally bioturbated sediments in the anoxic arabian sea our monsoon proxy record reveals several intervals of weak summer monsoon that coincide with cold periods documented in the north atlantic region4 including the most recent climate changes from the medieval warm period to the little ice age and then to the present we therefore suggest that the link between north atlantic climate and the asian monsoon is a persistent aspect of global climate

monsoon related changes in sea surface productivity and water column denitrification in the eastern arabian sea during the last glacial cycle sea surface salinity reconstruction for the holocene and the last glacial maximum lgm suggests that the lgm eastern arabian sea was more saline by 1 5 psu than the holocene due to weakened freshwater flux to the region and intensified winter monsoons time series of sedimentary organic carbon corg p alkenone and y 13 corg for the last 100 kyr together indicate increased glacial productivity significantly reduced sedimentary y 15 n during the lgm indicates however diminished water column denitrification in spite of increased productivity the distinct decoupling of denitrification from productivity during the lgm can be explained by vigorous ventilation of the thermocline as a result of simultaneously intensified formation of high salinity water and deep winter mixing in northern arabian sea related to the extreme cold climate the closely comparable time series y 15 n records across the arabian sea suggest basin wide homogenisation of the isotopic signal this probably resulted from combined monsoon dependent surface water mixing due to changes in the relative strength of reversing surface circulations and intermediate water mixing due to changes in north south salinity gradient d 2005 elsevier b v all rights reserved

intrusion of the bay of bengal water into the arabian sea during winter monsoon and associated chemical and biological response this work was supported by the department of ocean development under the program marine research living resources mr lr jayu narvekar acknowledges the financial support from csir

a glimpse of the quaternary monsoon history from india and adjoining seas abstract the evolution of the monsoon is briefly summarized taking into account previous studies conducted on both terrestrial and marine records recovered from the indian subcontinent and the adjoining seas while the initiation of the monsoon is debated it seems clear that a major intensification of the summer monsoon occurred at 8 2 ma a seasonal monsoon circulation with distinct summer and winter monsoon phases was established at 2 8 ma in the late quaternary the summer monsoon weakens during glacial periods as compared to interglacial periods the centennial to sub centennial scale changes in the monsoon during both glacial and interglacial periods suggest strong links between high latitude processes and the tropical monsoon and its role in modulating northern hemispheric climate the glacial terminations are marked by weak monsoon activity the summer monsoon weakened during the middle holocene after the early holocene optimum a change in the monsoon intensity though alters the salinity of the seas surrounding india the quantitative paleosalinity reconstructions still have large associated uncertainties and an effort should be made to lower them

a revisit of drawdown behavior during pumping in unconfined aquifers received 16 march 2010 revised 7 february 2011 accepted 7 march 2011 published 6 may 2011 1 in this study the s shaped log log drawdown time curve typical of pumping tests in unconfined aquifers is reinvestigated via numerical experiments like previous investigations this study attributes the departure of the s shape from the drawdown time behavior of the confined aquifer to the presence of an additional source of water unlike previous studies this sourceof water isreinvestigated byexaminingthetemporal and spatial evolution of the rate of change in storage in an unconfined aquifer during pumping this evolution is then related to the transition of water release mechanisms from the expansion of water and compaction of the porous medium to the drainage of water from the unsaturated zone above the initial water table and initially saturated pores as the water table falls during the pumping of the aquifer afterward the 1 d vertical drainage process in a soil column is simulated results of the simulation show that the transition of the water release mechanisms in the 1 d vertical flow without an initial unsaturated zone can also yield the s shaped drawdown time curve as in an unconfined aquifer we therefore conclude that thetransitionofthewaterreleasemechanismsandverticalflowintheaquiferarethecauseof the s shaped drawdown time curve observed during pumping in an unconfined aquifer we also find that the moisture retention characteristics of the aquifer material have greater impact than its relative permeability characteristics on the drawdown time curve furthermore influences of the spatial variability of saturated hydraulic conductivity specific storage and saturated moisture content on the drawdown curve in the saturated zone are found to be more significant than those of other unsaturated properties finally a cross correlation analysis reveals that the drawdown at a location in a heterogeneous unconfined aquifer is mainly affected by local heterogeneity near the pumping and observation wells applications of a model assuming homogeneity to the estimation of aquifer parameters as such may require a large number of observation wells to obtain representative parameter values in conclusion we advocate that the governing equation for variably saturated flow through heterogeneous media is a more appropriate and realistic model that explains the s shaped drawdown time curves observed in the field

inferring spatial distribution of the radially integrated transmissivity from pumping tests in heterogeneous confined aquifers 1 hydrologists routinely analyze pumping test data using conventional interpretation methods that are based on the assumption of homogeneity and that consequently yield single estimates of representative flow parameters however natural subsurface formations are intrinsically heterogeneous and hence the flow parameters influencing the drawdown vary as the cone of depression expands in time in this paper a novel procedure for the analysis of pumping tests in heterogeneous confined aquifers is developed we assume that a given heterogeneous aquifer can be represented by a homogeneous system whose flow parameters evolve in time as the pumping test progresses at any point in time the interpreted flow parameters are estimated using the ratio of the drawdown and its derivative observed at that particular time the procedure is repeated for all times yielding time dependent estimates of transmissivity ti t and storativity si t based on the analysis of the sensitivity of drawdown to inhomogeneities in the t field the time dependent interpreted transmissivity values are found to be a good estimate of tg r the geometric mean of the transmissivity values encompassed within a progressively increasing radius r from the well the procedure is illustrated for gaussian heterogeneous fields with ln t variances up to a value of 2 the impact of the separation distance between the pumping well and observation point on data interpretation is discussed the results show that information about the spatial variability of the transmissivity field can be inferred from time drawdown data collected at a single observation point

a high resolution record of late quaternary upwelling along the oman margin arabian sea based on planktonic foraminifera planktonic foraminiferal abundances fluxes test sizes and coiling properties are influenced in various ways by the southwest monsoon winds and associated upwelling in the western arabian sea to determine the short term changes in the southwest monsoon we have carried out a high resolution time series analysis of three upwelling indices total flux of planktonic foraminiferal tests and flux and relative abundance of the planktonic foraminiferal species globigerina bulloides from ocean drilling program odp site 723a oman margin western arabian sea spanning the last 19 kyr in addition we have determined the relationships between upwelling intensity and the relative abundance fluxes and shell concentrations of various planktonic foraminiferal species upwelling indices suggest that from 19 to 16 ka 22 to 18 2 cal kyr b p the sw monsoon was relatively strong compared to the period 15 8 to 12 5 ka 17 8 to 13 8 cal kyr b p the intensification of the sw monsoon took place at 12 ka 13 1 cal kyr b p and reached a peak between 10 and 5 ka 10 6 and 4 8 cal kyr b p the high resolution data further demonstrate that the sw monsoon has started weakening from 5 ka 4 8 cal kyr b p and the weakest phase was in place at 3 5 ka 3 cal kyr b p which coincides with evidence of an arid climate in western tibet fluxes and shell concentrations of many of the planktonic foraminiferal species increased between 12 and 5 ka in response to the intensification of the sw monsoon winds after the last glacial period globigerina bulloides shows a fivefold to tenfold increase in flux during this period of intense upwelling the other species whose fluxes are influenced by this upwelling change are in order from strongest to weakest response globigerinita glutinata globigerinoides ruber neogloboquadrina dutertrei globigerinella aequilateralis globigerina falconensis and globigerinoides sacculifer the relative abundances of g bulloides and g ruber increased during intense upwelling whereas the relative abundances of g glutinata n dutertrei g falconensis and g sacculifer did not increase during this period which might be due to differences in the productivity of various species in relation to upwelling change therefore the fluxes and shell concentrations provide better and more reliable information about the changes in the monsoon system in the arabian sea than relative abundance data

a high resolution record of atmospheric 14c based on hulu cave speleothem h82 abstract the development of a calibration of atmospheric radiocarbon 14c is a significant scientific goal because it provides the means to link the numerous 14c dated paleoclimate records to a common timescale with absolutely dated records and thereby improve our understanding the relationships between the carbon cycle and climate change currently few calibration datasets that directly sample the atmospheric 14c reservoir are available beyond the end of the dendro dated holocene tree ring record at 12 6 kyr bp before 1950 ad in the absence of suitable true atmospheric records 14c calibrations beyond this age limit are based largely on marine data that are complicated by the marine reservoir effect which may have varied over the glacial cycle in this paper we present a high resolution record of u th series and 14c measurements from hulu cave speleothem h82 spanning 10 6 26 8 kyr bp corrections for detrital 230th are negligible and the contribution of 14c free geologic carbon to the speleothem calcite is small 5 6 and is stable across major climate shifts the time series provides a 16 kyr record of atmospheric 14c as well as an updated age model for the existing hulu cave 18o record the 14c data are in good overall agreement with existing marine and terrestrial 14c records but comparisons with the cariaco basin marine 14c record through the deglacial interval reveal that the cariaco reservoir age appears to have varied during parts of the younger dryas and heinrich stadial 1 cold events this highlights the importance of developing extended high resolution marine and terrestrial 14c records as a means of detecting changes in ocean circulation over the glacial cycle

late quaternary biogenic productivity and organic carbon deposition in the eastern arabian sea abstract paleoproductivity variations in the eastern arabian sea during the late quaternary period 42 ka bp to present have been studied using accumulation rates of sedimentary biogenic components organic carbon corg nitrogen n caco3 sr and ba such a multi proxy approach reveals decreased surface productivity during the last glacial interglacial transition the observed change of surface water productivity during the last glacial interglacial period is in antiphase to those observed in other low and mid latitude upwelling areas however consistent with some of the upwelling regions like nw africa and nw mexico sedimentary corg and n are found to be decoupled from surface productivity trend with significant enrichments in corg and n during the last glacial maximum lgm this is interpreted in terms of increase in sedimentation rates by a factor of 3 4 resulting in the better preservation of corg during the lgm

capturing aquifer heterogeneity comparison of approaches through controlled sandbox experiments 1 groundwater modeling has become a vital component to water supply and contaminant transport investigations these models require representative hydraulic conductivity k and specific storage ss estimates or a set of estimates representing subsurface heterogeneity currently there are a number of approaches for characterizing and modeling k and ss heterogeneity in varying degrees of detail but there is a lack of consensus for an approach that results in the most robust groundwater models with the best predictive ability the main goal of this study is to compare different heterogeneity modeling approaches e g effective parameters geostatistics geological models and hydraulic tomography when input into a forward groundwater model and used to predict 16 independent cross hole pumping tests we first characterize a sandbox aquifer through single and cross hole pumping tests and then use these data to construct forward groundwater models of various complexities both homogeneous and heterogeneous distributions two effective parameter models are constructed 1 by taking the geometric mean of single hole test k and ss estimates and 2 calibrating effective k and ss estimates by simultaneously matching the response at all ports during a cross hole test heterogeneous models consist of spatially variable k and ss fields obtained via 1 kriging single hole data 2 calibrating a geological model and 3 conducting transient hydraulic tomography zhu and yeh 2005 the performance of these parameter fields are then tested through the simulation of 16 independent cross hole pumping tests our results convincingly show that transient hydraulic tomography produces the smallest discrepancy between observed and simulated drawdowns

prediction of solute transport in a heterogeneous aquifer utilizing hydraulic conductivity and specific storage tomograms a sequential procedure of hydraulic tomographical inversion is applied to characterize at high resolution the spatial heterogeneity of hydraulic conductivity and specific storage at the field test site stegemuhle germany the shallow aquifer at this site is examined by five short term multilevel pumping tests with 30 pumping observation pairs between two wells utilizing travel time diagnostics of the recorded pressure response curves fast eikonal based inversion is shown to deliver insight into the sedimentary structures thus the structural information from the generated travel time tomogram is exploited to constrain full calibration of the pressure response curves based on lateral extrapolation from the measured inter well profile a three dimensional reconstruction of the aquifer is obtained it is demonstrated that calibration of spatially variable specific storage in addition to hydraulic conductivity can improve the fitting of the model while the structural features are only slightly changed at the field site two tracer tests with uranine and sodium naphthionate were also performed and their concentrations were monitored for 2 months the measured tracer breakthrough curves are employed for independent validation of the hydraulic tomographical reconstruction it is demonstrated that major features of the observed solute transport can be reproduced and structures relevant for macrodispersive tracer spreading could be resolved however for the mildly heterogeneous aquifer the tracer breakthrough curves can also be approximated by a simplified homogeneous model with higher dispersivity therefore improved validation results that capture specific characteristics of the breakthrough curves would require additional hydraulic measurements

estimation of field scale soil hydraulic and dielectric parameters through joint inversion of gpr and hydrological data 1 a method is described for the joint use of time lapse ground penetrating radar gpr travel times and hydrological data to estimate field scale soil hydraulic parameters we build upon previous work to take advantage of a wide range of cross borehole gpr data acquisition configurations and to accommodate uncertainty in the petrophysical function which relates soil porosity and water saturation to the effective dielectric constant we first test the inversion methodology using synthetic examples of water injection in the vadose zone realistic errors in the petrophysical function result in substantial errors in soil hydraulic parameter estimates but such errors are minimized through simultaneous estimation of petrophysical parameters in some cases the use of a simplified gpr simulator causes systematic errors in calculated travel times simultaneous estimation of a single correction parameter sufficiently reduces the impact of these errors we also apply the method to the u s department of energy doe hanford site in washington where time lapse gpr and neutron probe np data sets were collected during an infiltration experiment we find that inclusion of gpr data in the inversion procedure allows for improved predictions of water content compared to predictions made using np data alone these examples demonstrate that the complimentary information contained in geophysical and hydrological data can be successfully extracted in a joint inversion approach moreover since the generation of tomograms is not required the amount of gpr data required for analyses is relatively low and difficulties inherent to tomography methods are alleviated finally the approach provides a means to capture the properties and system state of heterogeneous soil both of which are crucial for assessing and predicting subsurface flow and contaminant transport

deglacial indian monsoon failure and north atlantic stadials linked by indian ocean surface cooling during the last deglaciation the indian summer monsoon failed during periods of cooling in the north atlantic sediment records suggest that the concomitant cooling of the surface of the arabian sea contributed to the monsoon weakening

early deglacial 19 17 ka strengthening of the northeast monsoon 1 earlier studies that mostly relied on bulk 14c dating indicated a weaker southwest monsoon swm and a stronger than present northeast monsoon nem during the last glacial maximum lgm 18000 14c years or 21000 calendar years ago we have analyzed a sediment core from the equatorial indian ocean where planktonic foraminifera were dated by accelerator mass spectrometry ams 14c 18o analysis of three species of foraminifera viz globigerinoides ruber globigerinoides sacculifer and globorotalia menardii reveals that the nem strengthened during the early deglacial period 15000 14c years ago or 18000 calendar years ago relative to the present and not during the lgm as surmised earlier

sea level and deep water temperature changes derived from benthic foraminifera isotopic records we show that robust regressions can be established between relative sea level rsl data and benthic foraminifera oxygen isotopic ratios from the north atlantic and equatorial pacific ocean over the last climatic cycle we then apply these regressions to long benthic isotopic records retrieved at one north atlantic and one equatorial pacific site to build a composite rsl curve as well as the associated confidence interval over the last four climatic cycles our proposed reconstruction of rsl is in good agreement with the sparse rsl data available prior to the last climatic cycle we compute bottom water temperature changes at the two sites and at one southern indian ocean site taking into account potential variations in north atlantic local deep water 18o our results indicate that a last glacial maximum lgm enrichment of the ocean mean oxygen isotopic ratio of 0 95 is the lowest value compatible with unfrozen deep waters in the southern indian ocean if local deep water 18o did not increase during glacials with respect to present such a value of the lgm mean ocean isotopic enrichment would impose a maximum decrease in local bottom water 18o at the north atlantic site of 0 30 during glacials

deglaciation in the tropical indian ocean driven by interplay between the regional monsoon and global teleconnections abstract high resolution climate records of the ice age terminations from monsoon dominated regions reveal the interplay of regional and global driving forces speleothem records from chinese caves indicate that glacial terminations were interrupted by prominent weak monsoon intervals wmi lasting a few thousand years deglacial wmis are interpreted as the result of cold temperature anomalies generated by sea ice feedbacks in the north atlantic most prominently during heinrich events recent modeling results suggest however that wmis reflect changes in the intensity of the indian rather than the east asian monsoon here we use foraminiferal trace element mg ca and ba ca and stable isotope records from a sediment core off the malabar coast in the southeastern arabian sea with centennial scale resolution to test this hypothesis and to constrain the nature and timing of deglacial climate change in the tropical indian ocean the malabar deglacial sst record is unique in character and different from other tropical climate records sst at the last glacial maximum was 2 7 0 5 c colder than pre industrial sst deglacial warming started at 18 6 95 ci range 18 8 18 1 kyr bp within error of the onset of warming at other tropical sites as well as in antarctica and the southern ocean and either coeval with or up to 1 kyr before the atmospheric co 2 rise warming took place in two steps separated by an interval of stable sst between 15 7 16 2 14 9 and 13 2 13 9 12 0 kyr bp the 18 o water record and the ba ca record which is a measure of indian sub continent riverine runoff indicate that the last ice age termination was marked by a prominent weak indian monsoon interval interrupted by an intense monsoon phase as seen in speleothem records and predicted by modeling a strong correspondence between the timing of the malabar 18 o sw record and the hulu cave monsoon record suggests that deglacial 18 o changes in both localities dominantly reflect compositional changes in precipitation likely driven by changes in the north atlantic

carbonate and organic carbon content changes over last 20 ka in the southeastern arabian sea paleoceanographic implications two gravity cores aas 38 4 and aas 38 5 recovered from the eastern arabian sea were analyzed for calcium carbonate caco3 organic carbon aluminium al and titanium ti in order to understand the calcium carbonate and terrigenous fluctuations during the holocene and last glacial period high caco3 and low al and ti during the holocene and low caco3 and high al and ti during the last glacial period suggest that caco3 content in these two cores appears to be controlled by the dilution of terrigenous material the supply of terrigenous material to the core sites was higher during the last glacial period than in the holocene organic carbon values were lower 2 during the last glacial period in core aas 38 4 but the opposite was found in core aas 38 5 this inconsistent pattern of organic carbon changes in the two cores studied indicates that the distribution of organic carbon in the eastern arabian sea is controlled not only by the supply of organic matter from the water column but also by sediment texture and dilution of sediment components

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr