the paleoclimatic record provided by eolian deposition in the deep sea the geologic history of wind the mineral component of pelagic sediment is brought to the deep sea by transport in the wind extraction and analysis of this dust allows estimation of the past aridity of the eolian source region via flux determinations and of the intensity of the transporting winds from grain size data these two parameters the grain size and mass flux of dust vary independently there are three significant sources of modern dust eastern and central asia northwest africa and arabia all in the northern hemisphere as the rainfall associated with the intertropical convergence zone is an effective barrier to southerly transport of dust the northern hemisphere is an order of magnitude more dusty than is the southern an asymmetry that has characterized most of the cenozoic eolian flux data show that most of the northern hemisphere was more arid during glacial maxima with 3 to 5 times as much dust transported during glacial stages than during interglacials only northwestern south america varied in the opposite sense the periodicity of quaternary variation in both eolian flux and eolian grain size data is strongly influenced by the milankovitch cycles of orbital variability wind intensities vary on a shorter time scale than the general 100 kyr cycles of glaciation and general aridity eolian grain sizes display forcing at precessional 19 and 23 kyr tilt 41 kyr and at approximately 30 kyr periodicities as a result the generalization that winds are uniformly stronger during glacial times is not valid whole cenozoic records show that the largest change in dust flux an order of magnitude increase occurred in the northern hemisphere and reflects continental drying associated with the late pliocene onset of northern hemisphere glaciation southern hemisphere eolian records show no sign of paleoclimatic changes in the late pliocene the most important change in cenozoic atmospheric circulation was a severalfold reduction in wind intensity that occurred at the time of the paleocene eocene boundary before then latest cretaceous and paleocene winds were essentially as strong as those of the late cenozoic this shift appears to be one of several climatic responses to a change in the nature and amount of global heat transport at about 55 ma

regional trends in evaporation loss and water yield based on stable isotope mass balance of lakes the ontario precambrian shield surveys abstract stable isotopes of water oxygen 18 and deuterium were measured in water samples collected from a network of 300 lakes sampled in six 100 km 2 blocks centred at 49 72 n 91 46 w 48 49 n 91 58 w 50 25 n 86 62 w 49 78 n 83 98 w 48 24 n 85 49 w 47 73 84 52 w within precambrian shield drainages in the vicinity of lake superior northern ontario canada additional sampling was also conducted within the turkey lakes watershed 47 03 n 84 38 w a research basin situated in the algoma region located 50 km north of sault saint marie ontario the studies were undertaken to gain a better understanding of hydrology and geochemistry of watersheds in the region in order to better predict acid sensitivity of lakes the main objective of this paper is to describe the hydrologic variations observed based on stable isotope results evaporative isotopic enrichment of lake water was found to be systematic across the region and its deviation from the isotopic composition of precipitation was used to estimate the evaporation inflow to the lakes as well as runoff or water yield based on a simple isotope mass balance model the analysis illustrates significant variability in the water yield to lakes and reveals a pattern of positively skewed distributions in all six widely spaced blocks suggesting that a high proportion of lakes have relatively limited runoff whereas relatively few have greater runoff such basic information on the drainage structure of an area can be valuable for site specific hydrologic assessments but also has significant implications for critical loads assessment as low runoff systems tend to be less buffered and therefore are more sensitive to acidification importantly the turkey lakes sampling program also suggests that isotope based water yield is comparable in magnitude to hydrometric gauging estimates and also establishes that uncertainty related to stratification can be as high as 20 or more for individual lakes although it likely has only a minor influence on regional survey results while further analysis in gauged lake watersheds would be beneficial to constraining the accuracy of the method or calibrating it for operational use it is nevertheless a powerful tool in its present form for lake to lake and regional runoff inter comparisons

deep sea fluid and sediment dynamics influence of hill to seamount scale seafloor topography abstract deep sea sediments play a central role in a wide range of subject areas a number of important controls on the formation of sedimentary deposits have been studied however to date the impact of submarine landscape geometry as a possible control has received comparatively little attention this seems to be particularly true for intermediate scale topographic features such as abyssal hills knolls and seamounts that can be found in many regions of the global seafloor recent estimates suggest that in the deep open oceans away from continental margins there might be as many as 25 106 abyssal hills knolls and seamounts despite this large number very little is known about how they influence environmental complexity and patchiness biogeochemical fluxes and the formation of sedimentary records this paper reviews the currently known types of fluid flow interactions with abyssal hills knolls and seamounts that could potentially influence the way sediments are formed the main types of relevant flow components are quasi steady to eddying background flow internal lee and near inertial waves barotropic and baroclinic tides and seamount trapped waves previous studies looking into systematic links between fluid dynamics and sediments at hills knolls and seamounts are reviewed finally a case study is presented which aims to combine our current knowledge and investigate whether a given combination of recent fluid flow components leaves a detectable imprint in the recent sediments on and around a short seamount the main conclusions and implications are as follows 1 topographically generated flow field geometries that are composed of a number of different prevailing fluid flow components can be reflected and detected in properties of the underlying sediments 2 tidal and other higher frequency lee wave near inertial components of deep ocean currents can be essential for locally driving total current velocities across threshold values for non deposition erosion resuspension of freshly deposited deep sea sediments moreover there is evidence suggesting that not only maximum current speeds but also intensities of higher frequency tidal and or near inertial current direction variability might control sediment dynamics and sediment formation this relativises the view that current speed is the main or even only controlling factor for sediment dynamics and sediment formation 3 when it comes to the reconstruction of paleo flows these findings imply that certain sedimentary records may well reveal more about variability in the higher frequency flow components than about variability in the basin scale net flow component that often is the focus of paleoceanographic studies 4 single core paleo records from hill seamount or similarly controlled sediment deposits may be biased due to the asymmetry of flow fields around these topographic features to arrive at unbiased paleo records for non fluid dynamic parameters the influence of the flow field geometry would have to be removed from the record first 5 it seems the mechanistic understanding of hill and seamount related flow topography interactions and their links to sediment dynamics is approaching a level that may a facilitate improved interpretation of topographically controlled sedimentary paleo records b help fill in the knowledge gap that exists for functional deep sea biodiversity at intermediate space scales and c improve predictive capabilities for exploration of economically relevant iron manganese fe mn crusts on seamounts

nd and sr isotope compositions of different phases of surface sediments in the south pacific extraction of seawater signatures boundary exchange and detrital dust provenance the radiogenic isotope composition of neodymium nd and strontium sr are useful tools to investigate present and past oceanic circulation or input of terrigenous material we present nd and sr isotope compositions extracted from different sedimentary phases including early diagenetic fe mn coatings unclean foraminiferal shells fossil fish teeth and detritus of marine surface sediments core tops covering the entire midlatitude south pacific comparison of detrital nd isotope compositions to deep water values from the same locations suggests that boundary exchange has little influence on the nd isotope composition of western south pacific seawater concentrations of rare earth elements ree and al ca ratios of unclean planktonic foraminifera suggest that this phase is a reliable recorder of seawater nd isotope composition the signatures obtained from fish teeth and nondecarbonated leachates of bulk sediment fe mn oxyhydroxide coatings also agree with unclean foraminifera direct comparison of nd isotope compositions extracted using these methods with seawater nd isotope compositions is complicated by the low accumulation rates yielding radiocarbon ages of up to 24 kyr thus mixing the signal of different ocean circulation modes this suggests that different past seawater nd isotope compositions have been integrated in authigenic sediments from regions with low sedimentation rates combined detrital nd and sr isotope signatures indicate a dominant role of the westerly winds transporting lithogenic material from south new zealand and southeastern australia to the open south pacific the proportion of this material decreases toward the east where supply from the andes increases and contributions from antarctica cannot be ruled out

the stable isotopes of site wide waters at an oil sands mine in northern alberta canada abstract oil sands mines have large disturbance footprints and contain a range of new landforms constructed from mine waste such as shale overburden and the byproducts of bitumen extraction such as sand and fluid fine tailings each of these landforms are a potential source of water and chemical release to adjacent surface and groundwater and consequently the development of methods to track water migration through these landforms is of importance the stable isotopes of water i e 2 h and 18 o have been widely used in hydrology and hydrogeology to characterize surface water groundwater interactions but have not been extensively applied in mining applications or specifically to oil sands mining in northern alberta a prerequisite for applying these techniques is the establishment of a local meteoric water line lmwl to characterize precipitation at the mine sites as well as the development of a catalogue of the stable water isotope signatures of various mine site waters this study was undertaken at the mildred lake mine site owned and operated by syncrude canada ltd the lmwl developed from 2 years 2009 2012 of sample collection is shown to be consistent with other lmwls in western canada the results of the study highlight the unique stable water isotope signatures associated with hydraulically placed tailings sand or fluid fine tailings and overburden shale dumps relative to natural surface water and groundwater the signature associated with the snow melt water on reclaimed landscapes was found to be similar to ground water recharge in the region the isotopic composition of the shale overburden deposits are also distinct and consistent with observations made by other researchers in western canada on undisturbed shales the process water associated with the fine and coarse tailings streams has highly enriched 2 h and 18 o signatures these signatures are developed through the non equilibrium fractionation of imported fresh river water during evaporation from cooling towers used within the raw water process circuit this highly fractionated surface water eventually becomes part of the recycled tailings water circuit and as a consequence it undergoes further non equilibrium fractionation as a result of surface evaporation leading to additional enrichment along local evaporation lines

paleogene calcite compensation depth in the eastern subtropical pacific answers and questions 1 ocean drilling program leg 199 drilled a north south transect across the eocene paleoequator in the eastern pacific permitting reconstruction the calcite compensation depth ccd since earliest eocene time the ccd was relatively shallow near the early eocene pacific equator 3200 m and unlike modern latitudinal ccd gradients deepened to the north to 3600 m paleolatitude 10 n at 41 ma the ccd underwent a brief sharp transient deepening of 700 m then remained shallow until the eocene oligocene boundary at the e o boundary the ccd deepened by 1200 m in less than 300 kyr this rapid deepening served to more than double the area of seafloor subject to caco3 deposition sea level fall associated with ice volume buildup and ensuing shelf basin fractionation is unlikely to be the sole cause of the increased deep ocean caco3 burial rather a sudden rapid increase in the amount of ca entering the ocean appears necessary to explain the observations

neogene history of the calcite compensation depth and lysocline in the south pacific ocean the depth time pattern of calcite accumulation recorded at deep sea drilling project dsdp sites beneath the oligotrophic subtropical gyre in the south east pacific ocean allows us to define here both the calcite compensation depth ccd and the lysocline the neogene ccd history is one of shoaling before 15 or 20 myr and subsequent deepening to the present level of 4 100 m a broad zone of increased calcite dissolution 600 m thick formed during early to middle miocene time and has remained this zone the lysocline denotes an important change in ocean chemistry and may reflect either an increase in the volume of more corrosive deep water beginning about 18 myr and reaching steady state by 14 myr the time of rapid ice build up in antarctica or an increase in calcite rain rate caused by an increase in surface water productivity

pacific farallon relative motion 42 59 ma determined from magnetic and tectonic data from the southern austral islands we have used recently collected magnetic profiles and high resolution multibeam bathymetry data near the southern austral islands in french polynesia to constrain the relative motion of the pacific and farallon plates between chron 25 and chron 18 42 59 ma a change in plate motion at about chron 21 50 ma which reoriented spreading direction in the area by 10 12 clockwise was apparently accommodated by a southward propagating rift which transferred 160 km of pacific crust to the farallon plate the outer pseudofault of which is preserved as the adventure trough these new constraints significantly revise previous estimates of pacific farallon relative motion at the crucial time period encompassing the bend in the hawaiian emperor chain believed to represent an abrupt change in the absolute motion of the pacific plate disrupted lithosphere at the adventure trough has apparently been a preferred site for later midplate volcanic activity

the conrad rise as an obstruction to the antarctic circumpolar current the antarctic circumpolar current acc carries water freely around the whole continent of antarctica but not without obstructions some such as the drake passage constrict its path while others such as mid ocean ridges may induce meandering in the current s cores and may cause the genesis of mesoscale turbulence it has recently been demonstrated that some regions that are only relatively shallow may also have a major effect on the flow patterns of the acc this is here shown to be particularly true for the conrad rise using the trajectories of surface drifters altimetry and the simulated velocities from a numerical model we show that the acc bifurcates at the western side of this rise in this process it forms two intense jets at the two meridional extremities of the rise with a relatively stagnant water body over the rise itself preliminary results from a recent cruise provide compelling support for this portrayal

direct observations of eddy turbulence at a ridge in the southern ocean 1 mesoscale turbulence in the acc is concentrated where the current interacts with prominent bottom topography an unusual region of high levels of turbulence is found downstream of the south west indian ridge it has been inferred that this turbulence consists largely of eddies generated at a fracture zone in the ridge a dedicated research cruise to the region has now presented data that allow us for the first time to track these eddies and to describe them in hydrographic detail we show that these eddies are at least 1000 m deep have a diameter of 250 km exhibit azimuthal speeds of up to 0 74 ms 1 have subsequent translation speeds of up to 0 09 ms 1 and consist of water masses derived from either north or south of the saf and apf eddies in general are shown to advect in a north eastward direction and dissipate before reaching a longitude of 40 e

subsidence of the seafloor in the atlantic and pacific oceans regional and large scale variations we present a deteiled survey of seafloor subsidence over the entire atlantic ocean and in the pacific ocean we examine the evolution of depth as age increases within narrow 200 km wide tectonic corridors elongate in the direction of spreading over the part of the young seafloor where the depth age12 relationship is valid we estimate the subsidence rate by a least squares adjustment in the three oceanic regions west atlantic east atlantic and pacific the subsidence rate shows regional 1000 2000 km and basin scale fluctuations of the order of 100 150 m m y 12 we also note that in some regions subsidence rate and axial depth are correlated with shallow ridges showing fast subsidence and deep ridges slow subsidence on the basis of published models we infer that regional variations in subsidence rate reflect temperature changes in the subaxial mantle of 100 c asymmetrical subsidence is observed in the atlantic especially in the south atlantic the age of departure from the depth age12 linear trend is highly variable with values larger than 100 m y reported in several instances but very low values 20 m y or less characterizing the central pacific flattening predicted by the plate model occurs in some areas in a number of cases however quite distinct behaviour is observed with a sudden depth increase where the depth age12 relationship breaks down and a slow rise of the seafloor at older ages our results suggest that the subsidence behaviour of the seafloor is much more complex than global plate or half space cooling models predict

evolution of deep sea sediments across the paleocene eocene and eocene oligocene boundaries abstract the composition and distribution of deep sea sediments is the result of a multitude of climatic biotic and oceanic conditions relating to biogeochemical cycles and environmental change here we utilize the extensive sediment archives of the international ocean discovery program iodp and its predecessors to construct maps of deep sea sediment type across two critical but contrasting boundaries in the paleogene one characterised by an interval of extreme warmth paleocene eocene and the other by global cooling eocene oligocene ocean sediment distribution shows significant divergence both between the latest paleocene and paleocene eocene thermal maximum petm across the eocene oligocene transition eot and in comparison to modern sediment distributions carbonate sedimentation in the latest paleocene extends to high southern latitudes disappearance of carbonate sediments at the petm is well documented and can be attributed to dissolution caused by significant ocean acidification as a result of carbon cycle perturbation biosiliceous sediments are rare and it is posited that the reduced biogenic silica deposition at the equator is commensurate with an overall lack of equatorial upwelling in the early paleogene ocean in the southern ocean we attribute the low in biosiliceous burial to the warm deep water temperatures which would have impacted biogenic silica preservation in the late eocene our sediment depositional maps record a tongue of radiolarian ooze in the eastern equatorial pacific enhanced biosiliceous deposits in the late eocene equatorial pacific and south atlantic are due to increased productivity and the spin up of the oceans our compilation documents the enhanced global carbonate sedimentation in the early oligocene confirming that the drop in the carbonate compensation depth was global

the large scale horizontal structure of the antarctic circumpolar current from fgge drifters the last decade of research in the southern ocean has shown that the antarctic circumpolar current acc is a complex system composed of narrow high speed currents separated by broad quiescent zones the circumpolar nature of this structure was examined using position and velocity data obtained from approximately 300 surface drifting buoys deployed in the southern ocean during the first garp global experiment fgge the distribution of buoys on 1 1 squares shows that in some regions most notably south of australia the buoys form three coherent bands of high buoy density which are separated by regions of low buoy density the latitudes of these bands coincide with those of the subtropical front subantarctic front and polar front to further examine the relationship between these fronts and buoy distribution locations of the three fronts determined from historical hydrographic data were used to partition the buoys into zonal bands corresponding to front and nonfront regions a mean buoy density and mean near surface speed were then computed for each zonal band high buoy densities were associated with all three fronts in the region south of australia other regions also showed a tendency although not as pronounced for buoys to accumulate in fronts the mean near surface speeds suggest that the subantarctic and polar fronts are circumpolar moreover the mean near surface speeds associated with the three frontal regions differ speeds within the subantarctic and polar front regions are approximately twice that associated with the subtropical front

variation of hydrological regime with permafrost coverage over lena basin in siberia 1 we use monthly discharge and permafrost data to examine the relationship between discharge characteristics and basin permafrost coverage for the nested subbasins of the lena river in siberia there are similarity and variation in streamflow regimes over the basin the ratios of monthly maximum minimum flows directly reflect discharge regimes the ratios increase with drainage area from the headwaters to downstream within the lena basin this pattern is different from the nonpermafrost watersheds and it clearly reflects permafrost effect on regional hydrological regime there is a significant positive relationship between the ratio and basin permafrost coverage this relationship indicates that permafrost condition does not significantly affect streamflow regime over the low permafrost less than 40 regions and it strongly affects discharge regime for regions with high permafrost greater than 60 temperature and precipitation have similar patterns among the subbasins basin precipitation has little association with permafrost conditions and an indirect relation with river flow regimes there exists a good relation between the freezing index and permafrost extent over the basin indicating that cold climate leads to high coverage of permafrost this relation relates basin thermal condition with permafrost distribution the combination of the relations between temperature versus permafrost extent and permafrost extent versus flow ratio links temperature permafrost and flow regime over the lena basin over the aldan subbasin the maximum minimum discharge ratios significantly decrease during 1942 1998 due to increase in base flow this change is consistent in general with permafrost degradation over eastern siberia

southeast pacific tectonic evolution from early oligocene to present plate tectonic reconstructions of the nazca antarctic and pacific plates are presented from late oligocene to present these reconstructions document major plate boundary reorganizations in the southeast pacific at dirons 6c 24 ma 6 o 20 ma and 5a 12 ma and a smaller reorganization at chron 3 o 5 ma during the chron 6 o reorganization it appears that a ridge propagated into crust north of the northernmost pacific antarctic ridge between the chiloe fracture zone fz of the chile ridge and agassiz fz of the pacific nazca ridge which resulted in a northward jump of the pacific antarctic nazca pac ant naz mid ocean triple junction during the chron 5a reorganization the chile ridge propagated northward from the valdivia fz system to the challenger fz through lithosphere formed roughly 5 myr earlier at the pacific nazca ridge during this reorganization a short lived microplate the friday microplate existed at the pac ant naz triple junction the pac ant naz triple junction jumped northward 500 km as a result of this reorganization from a location along the valdivia fz to a location along the challenger fz the chron 5a reorganization also included a change in spreading direction of the chile and pacific antarctic ridges the reorganization at chron 3 o initiated the formation of the juan fernandez and easter microplates along the east pacific rise the manner of plate boundary reorganization at chron 6 o and chron 5a and possibly today at the juan fernandez microplate included a sequence of rift propagation transfer of lithosphere from one plate to another microplate formation and microplate abandonment and resulted in northward migration of the pac ant naz triple junction the associated microplate differs from previously studied microplates in that there is no failed ridge

interaction of gravity flows with a rugged mid ocean ridge seafloor an outcrop example from macquarie island rugged bathymetry along slow spreading mid ocean ridges has the potential to impinge a strong control on gravity flows derived from oceanic fault scarps sedimentary lithofacies from the macquarie island ophiolite supports this hypothesis by displaying systematic variations that correspond with volcanic substrate differences and proximity to rift related faults pillow basalt terranes are associated with tightly confined bedrock corridors that funnel gravity flows into one direction vertical lithofacies variations formed from high density to low density turbidity currents record successive fill stages of the corridor axis during initial stages tight confinement in the axis suppressed flow dilution and fluid turbulence with continued corridor axis filling more dilute gravity flows predominated and formed lateral gradations from axial coarse grained turbidites into thinly interbedded overbank lithofacies along corridor margins these gravity flow lithofacies converge into very thin muddy condensed intervals along inter corridor highs where significant bottom current reworking occurred conversely partly confined tabular basalt floored basins promoted lateral expansion and dilution of gravity flows throughout the duration of basin filling variable paleocurrent indicator directions record multiple reflections of single gravity flow events off basin bounding fault barriers coarsening upward trends in these partly confined basins from thinly interbedded pelagic chert and ripple bedded sandstones up into stacked turbidites preserves the ponding of sediment starved submarine fans in general these ponded basins preserve the fine grained distal ends of a gravity flow continuum from coarse grained fault proximal en masse failures and cohesionless debris flows into medial high density turbidity flows and distal dilute turbidity flows

geophysics of the pitman fracture zone and pacific antarctic plate motions during the cenozoic multibeam bathymetry and magnetometer data from the pitman fracture zone fz permit construction of a plate motion history for the south pacific over the past 65 million years reconstructions show that motion between the antarctic and bellingshausen plates was smaller than previously hypothesized and ended earlier at chron c27 61 million years ago the fixed hot spot hypothesis and published paleomagnetic data require additional motion elsewhere during the early tertiary either between east antarctica and west antarctica or between the north and south pacific a plate reorganization at chron c27 initiated the pitman fz and may have been responsible for the other right stepping fracture zones along the ridge an abrupt 8 clockwise rotation in the abyssal hill fabric along the pitman flowline near the young end of chron c3a 5 9 million years ago dates the major change in pacific antarctic relative motion in the late neogene

runoff to boreal lakes linked to land cover watershed morphology and permafrost thaw a 9 year isotope mass balance assessment stable isotopes of oxygen and hydrogen were measured in water samples collected annually from a representative suite of 50 lakes in northeastern alberta over a 9 year period and are interpreted using a steady state isotope mass balance model to determine water yield and runoff ratios for the lake watersheds and residence time of the lakes this isotopic perspective on hydrology of the region provides new insight into the role of land cover watershed morphometry climatic drivers and permafrost thaw on lakes bog cover permafrost and presence of thaw features in bogs are found to be the dominant hydrologic drivers although morphometric properties such as elevation lake area and drainage basin area are also influential in addition to quantifying the hydrologic fluxes the analysis establishes contrasting conditions in more southerly lakes located in the stony mountains and west of fort mcmurray as compared with more northerly sites in the birch mountains caribou mountains and northeast of fort mcmurray mainly because of contributions from thawing permafrost at the northerly sites distinct hydrologic conditions are also noted for shield systems north of lake athabasca where bogs and permafrost are absent while permafrost thaw is not directly labelled by oxygen and hydrogen isotope composition isotope mass balance calculations suggest that contributions of up to several hundred millimetres per year are occurring in 14 of the 50 lake watersheds under study several of these lakes have water yields in excess of precipitation in some years and regional groups of lakes display significant correlations between water yield and percentage of bogs that have collapsed copyright 2015 john wiley sons ltd

detailed characterization of a cold antarctic eddy 1 eddy formation in the southern ocean plays a critical role in meridional exchanges of heat and salt it has also been shown to have a significant impact on primary productivity and on the creation of preferred feeding regions for birds and other predators this eddy formation is not geographically uniform but is concentrated in certain specific regions particularly where the antarctic circumpolar current crosses shallow bathymetry one such region is at the south west indian ridge where eddies are formed that subsequently drift past the prince edward islands we have studied such an eddy in detail it was at least 1000 m deep had a radius of 60 90 km a heat content of 5 40 1019 j and rotated at a rate of 1 revolution every 5 days altimetric observations show that it was formed at 51 s 32 e and that its intensity as expressed as its sea level anomaly declined by 40 of the original value within 144 days this relatively rapid dissipation suggests that these eddies do not have a lifetime of more than 14 months during that period they will have carried their anomalous heat and salt content about 1 5 degrees of latitude

post eocene intensification of deep water circulation in the central south pacific micropalaeontological clues from dredged sites along the eastern manihiki plateau margin reconstruction of early cenozoic deep water circulation is one of the keys to modelling earth s greenhouse to icehouse surface evolution but it has long been hampered by the paucity of information from the central south pacific to help overcome this knowledge gap we present new micropalaeontological data from dredged carbonates r v sonne expedition so193 at several eastern volcanic salients of the manihiki plateau interestingly despite appreciable longitudinal separations among the dredged sites ages indicated by the foraminiferal assemblages are consistently around the middle eocene including mixed turonian late cretaceous eocene at a single site suggesting widespread post eocene cessation of the pelagic sedimentation by integrating with independent seismic and chronostratigraphic data deep sea drilling project leg 33 for large scale erosion of top eocene oligocene sedimentary units on the eastern manihiki plateau our results can be viewed as novel physical evidence for the intensification of central south pacific deep water circulation since the eocene oligocene climatic transition

helium 3 plume over the east pacific rise at 25 s 1 we have measured helium isotopic ratios of sixty eight water samples collected in the southeastern pacific at 25 s the maximum excess 3he of 47 5 is observed just above the east pacific rise which is comparable to that of 50 5 at 15 s in literature a negative correlation between helium isotopes and neon to helium ratios of seawater samples suggests that the source of excess helium 3 in the mid depth water is considered to be a morb type mantle contour of excess 3he shows symmetrical pattern that is plume of 30 excess can be traced up to 1000 km on both east and west of the east pacific rise this pattern is consistent with a northward flow along the rise at 25 s estimated by a physical model our observation also supports a flow pattern of deep ocean currents which has been suggested by contour of excess 3he obtained from previous studies

hydrothermal helium plumes in the pacific ocean hydrothermal activity along the global mid ocean ridge system and at active seamounts introduces a 3 he rich signal into the deep ocean basins which can be used to trace patterns of ocean circulation and mixing this hydrothermal helium signal is especially strong in the pacific ocean where the spreading rate of the ridges is the greatest in several areas of the pacific the hydrothermal activity is of sufficient strength to produce intense helium plumes which clearly define the regional circulation among these are 1 a pair of helium plumes at 2500 m depth which extend westward from the east pacific rise at 10 n and 15 s into the interior of the pacific basin 2 a helium plume at 2000 m depth extending southwest from sources on the juan de fuca ridge in the northeast pacific and 3 a plume at 1100 m depth emanating from loihi seamount at 20 n which extends eastward from hawaii to the coast of mexico the flow field implied by the helium distribution appears to be in reasonable agreement with reid s 1997 steric height analysis for the pacific

observational evidence for a cross frontal heat pump in the southern ocean 1 transient eddies in the southern ocean play a central role in the global thermohaline circulation meridional exchange of heat and salt is not geographically uniformly distributed but may be concentrated in a number of specific regions where high levels of mesoscale turbulence are generated we have identified a powerful example of such a region at the south west indian ridge in which cross acc heat transport is dependent on eddy shedding we show that antarctic eddies are shed across the apf into the subantarctic at an average of 3 a year and that they have a longevity of 11 months furthermore we calculate the meridional heat and salt deficit of 5 6 1 5 1019 j and 8 1 1 5 1011 kg relative to the surrounding subantarctic waters of one such eddy despite the importance of this process eddy heat transport remains one of the most poorly observed quantities in the southern ocean

piston core record of late paleogene 31 ma to recent seafloor hydrothermal activity in the southwest pacific basin a large diameter piston core containing 8 35 m of metalliferous sediment has been recovered from a small abyssal valley in the remote southwest pacific basin 31 42 194 s 143 30 331 w 5082 m water depth providing unique insight into hydrothermal activity and eolian sedimentation there since the early oligocene a combination of fish teeth sr isotope stratigraphy and inaa geochemical data reveals an exponentially decreasing hydrothermal flux 31 ma to the present although hydrothermal sedimentation related to seafloor spreading explains this trend a complex history of late eocene early oligocene ridge jumps propagating rifts and plate tectonic reorganization of south pacific seafloor could have also played a role a possible hiatus in deposition as recorded by changes in core composition just below 2 m depth is beyond the resolution of the fish teeth sr isotope dating method employed here however the timing of this interval may be coincident with extinction of the pacific farallon ridge at 20 ma a low flux eolian component accumulating at this site shows an increase relative to the hydrothermal component above 2 m depth consistent with dust generating continental sources far to the west australia new zealand this is the first long term paleoceanographic record obtained from within the south pacific bare zone rea et al 2006 an anomalous region where pacific seafloor has largely escaped sediment accumulation since the late cretaceous

broad region of no sediment in the southwest pacific basin a broad region nearly the size of the mediterranean sea exists in the central south pacific ocean that is devoid of sediment and has been so since the late cretaceous the requirements for remaining sediment free are very low biological productivity a shallow calcite compensation depth essentially no dust input and no deposition of hydrothermal oxides and hydroxides one or two of these conditions are common but nowhere else do all four occur the combined effect of these sediment inhibiting factors is a consequence of crustal age seawater chemistry and atmospheric oceanographic and physiographic isolation furthermore this unique combination of conditions has prevailed for more than 80 million years

a coupled isotope tracer method to characterize input water to lakes summary we develop a new coupled isotope tracer method for characterizing the isotopic composition of input water to lakes and apply it in the context of ongoing hydrological process studies in the peace athabasca delta a large remote riparian ecosystem in the boreal region of western canada the region has a highly seasonal climate with floodplain lakes typically receiving input only during the 4 6 month open water season from varying proportions of spring snowmelt summer rains and river flooding these possible input sources have distinct ranges of isotopic compositions that are strongly constrained to a well defined local meteoric water line thus affording the opportunity to derive lake specific estimates of the integrated isotopic composition of input waters after accounting for the effects of secondary evaporative isotopic enrichment as shown by comparison of the results of isotopic surveys of delta lakes prior to freeze up in 2000 and 2005 this isotopic characterization of input waters can be combined with other data and field observations to provide new insight into spatial and temporal variability in delta lake recharge processes this includes evidence that summer rainfall in 2000 played an important role in replenishing shallow basins delta wide especially in the central low lying region compensating for below average snow accumulation during the previous winter in contrast 2005 was marked by greater relative contributions from both snowmelt and river flooding because of high winter snow accumulation and a spring ice jam that caused river floodwaters to enter some basins in the southern part of the delta the method is readily transferable to investigations in other remote regions that are sparsely monitored by conventional hydrometric networks

higher tritium concentrations measured in permafrost thaw lakes in northern alberta tritium concentrations were measured in a survey of 24 lakes 15 wetlands and 133 groundwaters in the oil sands region of northeastern alberta and compared with both recent precipitation and precipitation sampled during the 1960s tritium peak caused by atmospheric thermonuclear weapons testing water samples from lakes included a group of 14 thaw lakes that had higher runoff attributed to melting of permafrost in peat plateaus within their watersheds while tritium in all lakes was found to be intermediate between recent and 1960s concentrations the thaw lakes were found to be significantly enriched in tritium compared with other lakes as were unfrozen wetlands characterized by a thick sequence of low hydraulic conductivity peat the results provide further evidence of different water sources to the thaw lakes and may indicate that melting of modern permafrost in part formed since the 1950s is occurring in these systems copyright 2015 john wiley sons ltd

distribution of biogenic silica and quartz in recent deep sea sediments all available quartz and biogenic silica concentrations from deep sea surface sediments were intercalibrated plotted and contoured on a calcium carbonate free basis the maps show highest concentrations of biogenic silica opal along the west african coast along equatorial divergences in all oceans and at the polar front in the southern indian ocean these are all areas where upwelling is strong and there is high biological productivity quartz in pelagic sediments deposited far from land is generally eolian in origin its distribution reflects dominant wind systems in the pacific but in much of the atlantic and indian oceans the distribution pattern is strongly modified by turbidite deposition and bottom current processes

discovery of widely available abyssal rock patches reveals overlooked habitat type and prompts rethinking deep sea biodiversity habitat heterogeneity and species diversity are often linked on the deep seafloor sediment variability and hard substrate availability influence geographic patterns of species richness and turnover the assumption of a generally homogeneous sedimented abyssal seafloor is at odds with the fact that the faunal diversity in some abyssal regions exceeds that of shallow water environments here we show using a ground truthed analysis of multibeam sonar data that the deep seafloor may be much rockier than previously assumed a combination of bathymetry data ruggedness and backscatter from a trans atlantic corridor along the vema fracture zone covering crustal ages from 0 to 100 ma show rock exposures occurring at all crustal ages extrapolating to the whole atlantic over 260 000 km2 of rock habitats potentially occur along atlantic fracture zones alone significantly increasing our knowledge about abyssal habitat heterogeneity this implies that sampling campaigns need to be considerably more sophisticated than at present to capture the full deep sea habitat heterogeneity and biodiversity

evidence of a southward eddy corridor in the south west indian ocean mesoscale eddies and meanders have been shown to be one of the dominant sources of flow variability in the world s ocean one example of an isolated eddy hotspot is the south west indian ridge swir several investigations have shown that the swir and the corresponding planetary potential vorticity field f h exert a strong influence on the location and dynamics of the antarctic circumpolar current acc resulting in substantial fragmentation of the jets downstream of the ridge the easterly extension of this eddy corridor appears to be restricted to the deep channel separating the conrad rise from the del cano and crozet plateau however while the fate of eddies formed at the swir has been widely investigated and the frontal character of this eastward extension is well known the zone of diminishing variability that extends southwards to approximately 60 s remains poorly sampled using a combination of argo aviso and ncep ncar datasets the character of this eddy corridor as a conduit for warm core eddies to move across the acc into the antarctic zone is investigated in this study we track a single warm core eddy as it moves southwards from an original position of 31 e 50 20 s to where it dissipates 10 months later in the enderby basin at 56 20 s an argo float entrained within the eddy confirms that its water masses are consistent with water found within the antarctic polar frontal zone north of the apf latent and sensible heat fluxes are on average 8w m2 and 10w m2 greater over the eddy than directly east of this feature it is estimated that the eddy lost an average of 5w m2 of latent heat and 5w m2 of sensible heat over a 1 year period an amount capable of melting approximately 0 92m of sea ice in addition using an eddy tracking algorithm a total of 28 eddies are identified propagating southwards 25 of which are anti cyclonic in rotation based on the new argo float data combined with aviso and ncep ncar datasets these results suggest that the southward passage of warm core eddies act as vehicles transporting heat salt and biota southwards across the acc and into the eastern boundary of the weddell gyre

origin and hydrogeological setting of saline groundwater discharges to the athabasca river geochemical and isotopic characterization of the hyporheic zone abstract identifying impacts of oil sands development on aquatic ecosystems requires understanding of the natural background water quality in the athabasca oil sands region of alberta this is challenging because the athabasca river is incised directly into bitumen saturated sands of the mcmurray formation and other saline cretaceous and devonian formations this study compares the geochemical and isotopic composition of porewater sampled from the alluvial sediment beneath the athabasca river with regional groundwater data to identify the geological origin of these saline groundwaters and improve characterization of natural background sources of solutes entering the athabasca river terrain conductivity surveys conducted along the athabasca river were used to identify areas with evidence of saline groundwater discharge porewater samples were obtained from the alluvial sediment using drive point piezometers installed between 1 and 3 m below the water sediment interface and were analyzed for 18o 2h 34s so4 18o so4 87sr 86sr 13c dic 13c doc 3h and 14c the porewater in the alluvial sediment showed variable degrees of mixing with the overlying athabasca river water but the geochemical and isotopic composition in zones 1 3 and 5 are consistent with discharge of saline groundwater from cretaceous or devonian units the low percentages of modern carbon and 18o 2h 34s so4 18o so4 and 87sr 86sr signatures in the deepest porewater samples from zones 1 3 and 5 indicate glaciogenic water with high total dissolved solids originating from devonian sourced solutes theses saline groundwater discharge zones occur where higher horizontal hydraulic gradients coincide with areas of higher salinity in the adjacent cretaceous and devonian aquifers and areas with vertical connectivity with underlying devonian aquifers the results of this study demonstrate the influence of groundwater surface water interactions and saline bedrock formation water discharge to water quality along some reaches of the athabasca river which need to be considered in monitoring and water management strategies

effect of climate change and mining on hydrological connectivity of surficial layers in the athabasca oil sands region this is the peer reviewed version of the following article kompanizare m petrone rm shafii m robinson dt rooney rc effect of climate change and mining on hydrological connectivity of surficial layers in the athabasca oil sands region hydrological processes 2018 32 3698 3716 https doi org 10 1002 hyp 13292 which has been published in final form at https doi org 10 1002 hyp 13292 this article may be used for non commercial purposes in accordance with wiley terms and conditions for use of self archived versions

broad region of no sediment in the southwest pacific basin comment and reply reply we thank glasby 2007 1 for his comments regarding the sedimentary history of the southwest pacific basin our definition of this region of extremely low deposition which we termed a bare zone was based largely on our two not one as noted by glasby north south transects of the region and

predicting sediment thickness on vanished ocean crust since 200 ma tracing sedimentation through time on existing and vanished seafloor is imperative for constraining long term eustasy and for calculating volumes of subducted deep sea sediments that contribute to global geochemical cycles we present regression algorithms that incorporate the age of the ocean crust and the mean distance to the nearest passive margin to predict sediment thicknesses and long term decompacted sedimentation rates since 200 ma the mean sediment thickness decreases from 220 m at 200 ma to a minimum of 140 m at 130 ma reflecting the replacement of old panthalassic ocean floor with young sediment poor mid ocean ridges followed by an increase to 365 m at present day this increase reflects the accumulation of sediments on ageing abyssal plains proximal to passive margins coupled with a decrease in the mean distance of any parcel of ocean crust to the nearest passive margin by over 700 km and a doubling of the total passive margin length at present day mean long term sedimentation rates increase from 0 5 cm ky at 160 ma to over 0 8 cm ky today caused by enhanced terrigenous sediment influx along lengthened passive margins superimposed by the onset of ocean wide carbonate sedimentation our predictive algorithms coupled to a plate tectonic model provide a framework for constraining the seafloor sediment driven eustatic sea level component which has grown from 80 to 210 m since 120 ma this implies a long term sea level rise component of 130 m partly counteracting the contemporaneous increase in ocean basin depth due to progressive crustal ageing

circulation pathways and transports of the southern ocean in the vicinity of the southwest indian ridge circulation pathways and transports of the antarctic circumpolar current acc and agulhas return current arc around the complex bathymetry of the southwest indian ridge and del cano rise have been established from two hydrographic surveys and two year long moorings after crossing the southwest indian ridge in a 110 sv 1 sv 106 m3s 1 flow concentrated at 48 s the acc fragments before being reconcentrated into several branches by the bathymetry in particular 30 40 sv turns north around the eastern flank of the del cano rise turns west as part of anticyclonic flow round the del cano rise finally returning eastward as part of the crozet front eddy variability from both satellite data and moorings is low over the bathymetry of the del cano rise so the strong currents found between the del cano rise and the crozet plateau are believed to be permanent features this largely barotropic time independent transport is the major pathway for the acc to enter the crozet basin the anticyclonic flow also transfers water from the mozambique basin across the southwest indian ridge to the south side of the del cano rise given the evidence for fragmentation of the acc where it crosses the southwest indian ridge and the concentration of several jets into the crozet front from the acc subtropical front and agulhas return current it is misleading to relate standard frontal definitions such as the polar front and subantarctic front to the major transport pathways

broad region of no sediment in the southwest pacific basin comment and reply comment in their recent paper rea et al 2006 1 claim to have discovered an area covering 2 106 km2 located between 28 s and 42 5 s in the central south pacific that has been devoid of sediment since the late cretaceous or covered by less than 7 m of sediment the maximum thickness of

structure and transport of the antarctic circumpolar current and agulhas return current at 40 e hydrographic data are presented from a near meridional section across the agulhas return current the subtropical front and the antarctic circumpolar current acc in the southwest indian sector of the southern ocean the location and characteristics of the fronts are examined and the water masses are defined the agulhas return current emerges as a strong current as far east as 40 e which forms a marked front that is separate from the subtropical front and can be distinguished by a separate water mass comparisons are made with a similar hydrographic section at the greenwich meridian and several notable differences are found the subantarctic front at the greenwich meridian is a pronounced feature carrying a large proportion of the geostrophic transport of the acc on the southwest indian section however the subantarctic front is merged with the polar front at 48 s where the flow associated with the acc is concentrated geostrophic calculations show a large volume transport 84 to 103 sverdrup 1 sv 106 m3 s 1 associated with the agulhas return current at 40 s this is quite separate from the transport of the acc which totals 138 sv south of the subantarctic zone and the crozet plateau or 150 sv including flow in the subantarctic zone the transport of the acc out of the south atlantic sector appears to be higher than the transport into the south atlantic sector at drake passage with the extra transport most probably carried by upper layer and intermediate waters eddies are seen to be an important feature of the subantarctic zone where they help to modify the water masses antarctic intermediate water appears in two forms a saline 34 4 indian ocean variety and a fresh 34 2 atlantic ocean variety the atlantic variety is freshest at the polar front and occupies the southern half of the subantarctic zone within the eddies in the central subantarctic zone there is interleaving between these two forms of antarctic intermediate water north atlantic deep water is unable to cross the southwest indian ridge but can pass south of the crozet plateau in the form of circumpolar deep water which is slightly more saline 34 75 than at drake passage 34 73

using stable isotopes to characterize the conditions of groundwater formation on the eastern slope of the baltic shield nw russia abstract repeated continental glaciations and marine transgressions had a strong influence on the geochemical evolution of groundwater systems of the eastern slope of the baltic shield arkhangelsk region russia the spectrum from modern fresh waters to very old brines is distributed from the surface to a depth of 1 km in quaternary and vendian ediacaran sediments the purpose of this study was to i assess the isotopic composition of various types of groundwater ii assess the degree of participation of glacial melt and meteoric waters in the processes of dilution of seawater and brines according to isotope geochemical data and iii employ the use of stable isotopes to clarify previously performed groundwater dating it has been established that the salty water in the upper part of the vendian aquifer near the modern sea coast has maximum enrichment by heavy isotopes 18o 7 7 and 2h 98 9 on average it is a mixture of 19 51 glacial meltwater and 49 81 seawater the age of the marine component is 115 130 ka and the age of the glacial water is similar to that of the middle pleistocene the relict brackish water in the middle part of the vendian aquifer has the most depleted isotope composition 18o 14 1 and 2h 106 7 on average it is a mixture of 3 brine 8 19 glacial and 78 89 interglacial water and was formed in the range of 35 3 22 3 ka late pleistocene the maximum brine content 10 17 is characteristic of salt water in the lower part of the vendian aquifer the isotope composition of the fresh water is close to the weighted annual composition of modern precipitations 18o 13 2 and 2h 98 9 fresh water is a mixture of about 2 seawater up to 16 glacial water and 84 100 holocene water the age of this water is in the range from the present day to 11 8 1 6 ka the maximum depth of penetration of melt glacial waters of the middle pleistocene is assumed to be 600 m

geochemical isotopic and hydrological mass balance approaches to constrain the lake water groundwater interaction in dal lake kashmir valley it is important to have qualitative as well as quantitative understanding of the hydraulic exchange between lake and groundwater for effective water resource management dal a famous urban fresh water lake plays a fundamental role in social cultural and economic dynamics of the kashmir valley in this paper geochemical isotopic and hydrological mass balance approaches are used to constrain the lake water groundwater interaction of dal lake and to identify the sources of lake water water samples of precipitation n 27 lake water n 18 and groundwater n 32 were collected across the lake and its catchment for the analysis of 18o and 2h a total of 444 lake water samples and 440 groundwater samples springs tube wells and dug wells were collected for the analysis of ca2 mg2 hco3 so4 2 cl no3 na and k water table and lake water level were monitored at 40 observation locations in the catchment water table map including ph and ec values corroborate and verify the gaining nature of the dal lake stable isotopes of lake water in boddal and gagribal basins showed more deviation from the global meteoric water line than hazratbal and nigeen basins indicating the evaporation of lake water the isotopic and geochemical mass balance suggested that groundwater contributes a significant proportion 23 40 to dal lake the estimated average groundwater contribution to dal lake ranged from 31 2 103 to 674 103 m3 day 1 with an average of 276 103 m3 day 1 the study will be useful to delineate the possible sources of nutrients and pollutants entering the lake and for the management of lake water resources for sustainable development

landscape gradient assessment of thermokarst lake hydrology using water isotope tracers thermokarst lakes are widespread in arctic and subarctic regions in subarctic quebec nunavik they have grown in number and size since the mid 20th century recent studies have identified that these lakes are important sources of greenhouse gases this is mainly due to the supply of catchment derived dissolved organic carbon that generates anoxic conditions leading to methane production to assess the potential role of climate driven changes in hydrological processes to influence greenhouse gas emissions we utilized water isotope tracers to characterize the water balance of thermokarst lakes in nunavik during three consecutive mid to late summer seasons 2012 2014 lake distribution stretches from shrub tundra overlying discontinuous permafrost in the north to spruce lichen woodland with sporadic permafrost in the south calculation of lake specific input water isotope compositions i and lake specific evaporation to inflow e i ratios based on an isotope mass balance model reveal a narrow hydrological gradient regardless of diversity in regional landscape characteristics nearly all lakes sampled were predominantly fed by rainfall and or permafrost meltwater which suppressed the effects of evaporative loss only a few lakes in one of the southern sampling locations which overly highly degraded sporadic permafrost terrain appear to be susceptible to evaporative lake level drawdown we attribute this lake hydrological resiliency to the strong maritime climate in coastal regions of nunavik predicted climate driven increases in precipitation and permafrost degradation will likely contribute to persistence and expansion of thermokarst lakes throughout the region if coupled with an increase in terrestrial carbon inputs to thermokarst lakes from surface runoff conditions favorable for mineralization and emission of methane these water bodies may become even more important sources of greenhouse gases