paired dissolved and particulate phase cu isotope distributions in the south atlantic abstract copper cu is both an essential micronutrient and toxic to photosynthesizing microorganisms at low concentrations its dissolved vertical distribution in the oceans is unusual being neither a nutrient type nor scavenged type element this distribution is attributed to biological uptake in the surface ocean with remineralisation at depth combined with strong organic complexation by dissolved ligands scavenging onto particles and benthic sedimentary input we present coupled dissolved and particulate phase cu isotope data along the uk geotraces south atlantic section alongside higher resolution dissolved and particulate phase cu concentration measurements our dissolved phase isotope data contribute to an emerging picture of homogeneous deep ocean 65cu at about 0 65 relative to nist srm 976 we identify two pools of cu in the particulate phase a refractory lithogenic pool at about 0 and a labile pool accessed via a weak acidic leach at about 0 4 these two pools are comparable to those previously observed in sediments we observe deviations towards lighter 65cu values in the dissolved phase associated with local enrichments in particulate cu concentrations along the continental slopes and in the surface ocean copper isotopes are thus a sensitive indicator of localised particle associated benthic or estuarine cu inputs the measurement of cu isotopes in seawater is analytically challenging and we call for an intercalibration exercise to better evaluate the potential impacts of uv irradiation storage time and different analytical procedures

a field study of hydraulic geochemical and stable isotope relationships in a coastal wetlands system both chemical and stable isotope data provide important supplemental information to more traditional hydraulic data and unravel the processes that underpin the large variations in chemical and stable isotopic composition within a coastal wetland system the system studied was the lake warden wetlands located in esperance in south coast of western australia the spatial and temporal variations of chemical and isotopic composition of the individual water bodies within the system were measured for an annual cycle in broad terms the groundwater levels appear to follow the topography but the distinct higher chloride and isotopic concentrations observed within the wetlands were not reflected in the low lying coastal plain groundwater the hydraulic analysis of the region surrounding the wetlands suggest that the wetlands are flow through bodies however the chemical and isotope information indicates the lakes almost invariably act as discharge points for the surface water flows and the north south groundwater flow the northeast southwest groundwater flow is along an observed paleochannel within the wetlands system and in this case the chemical and isotopic evidence are complimentary with the hydraulic study the study highlighted the importance of correcting the isotopic values for the salt effect in highly saline water the isotopic activity ratios of 2h 2ha of some samples were up to 15 higher than the uncorrected values the high salinity of the terminal lake in the wetlands chain also required implementation of a theoretical evaporative model to explain the lower enrichment of the isotopic results as compared to expectations for a shallow and ephemeral lake the inter lake variation in the theoretical evaporative model parameters coupled with a significant variation in the hydrochemistry and isotope composition suggests that the lakes within the wetlands system cannot be treated as single water body as is implied by the bathymetry survey

scale dependence of seismic energy to moment ratio for strike slip earthquakes in japan we analyzed four pairs of a large m w 6 and a small m w 3 5 to 4 shallow strike slip earthquakes to investigate the scale dependence of the seismic energy to moment ratio an important macroscopic parameter which reflects the basic physical process of seismic slip these earthquakes occurred in the south western part of japan and high quality close in records epicentral distance 50 km are available for both the small and large earthquakes the paired events have almost the same focal mechanism and hypocenter location we used the spectral ratio of the paired events in order to remove the effects of attenuation along the wave propagation path and the station site response we then estimated the seismic energy from the source spectra estimated from the spectral ratio the energy to moment ratio increases with the earthquake size this scale dependence is very similar to that found earlier for earthquakes in southern california

variations in the zn si record over the last interglacial glacial transition we examined the zinc content of diatom frustules as an indicator of past changes in surface seawater zn2 concentration zn si data of samples from three cores located in the south atlantic sector of the southern ocean spanning the last interglacial glacial transition are presented changes in the zn si record are linked to changes in the surface water zn2 concentration the source of variation in zn2 concentration appears to be via changes in deep water upwelling and circulation we rule out changes in phytoplankton productivity and aeolian dust input as a source of variation in the zn si record likewise the zn si data are not linked to shifts in the diatom species composition of the sediment or sediment preservation effects the zn si results presented do not support the zinc hypothesis there is no link between the uptake of co2 by phytoplankton as inferred from the 13c record and the zn si record

trace metal concentrations in the ross sea and their relationship with nutrients and phytoplankton growth abstract dissolved and particulate trace metal concentrations dissolved fe zn cd co cu and ni particulate fe mn and al were measured along two transects in the ross sea during austral summer of 1990 total fe concentrations in southern ross sea and inshore waters were elevated 3 5 times that of northern waters dissolved zn cd and co concentrations were lower by factors of 4 5 3 5 and 1 6 in southern surface waters relative to northern waters dissolved cu and ni concentrations were similar in both areas elevated fe concentrations coincided with areas of increased productivity phytoplankton biomass and nutrient drawdown indicating that fe is an important factor controlling the location of phytoplankton blooms in the ross sea particulate concentrations of fe mn and al indicate two possible sources of iron to the ross sea resuspension of continental shelf sediments and iron incorporated in annual sea ice and released with meltwaters

dissolved iron in the southern ocean atlantic sector abstract we report a comprehensive dataset of dissolved iron fe comprising 482 values at 22 complete vertical profiles along a 1 latitudinal section at the zero meridian in addition a shorter high resolution 00 09 surface section of the southernmost part of the transect 66 00 69 35 s is presented within the upper surface mixed layer the concentrations of dissolved fe vary between 0 1 and 0 3 nm an inverse trend versus fluorescence suggests significant fe removal by plankton blooms vertical mixing and upwelling are the most important supply mechanisms of iron from deep waters to the upper surface mixed layer at lower latitude 42 s there is a distinct maximum of 0 6 0 7 nm in the 2000 3000 m depth range due to inflow of north atlantic deep water in one region 55 s elevated dissolved fe found in the surface mixed layer is ascribed to the recent deposition of aeolian dust originating from south america close to the antarctic continent there is an indication of fe supply in surface waters from icebergs in the deep waters there is a strong indication of a hydrothermal plume of dissolved fe and mn over the ridge in the bouvet region 52 56 s in the weddell gyre basin the dissolved fe in the deep water is 0 47 0 16 nm in the eastward flow at 56 62 s and is lower with a value of 0 34 0 14 nm in the westward flow at high 62 69 s latitude at the edge of the continental ice sheet on the prime meridian the continental margin of the antarctic continent appears to be lesser source of dissolved fe than in any other place in the world this is likely because it is unique in being overlain by the extending continental ice sheet that largely prevents biogeochemical cycling

evidence for the linked biogeochemical cycling of zinc cobalt and phosphorus in the western north atlantic ocean 1 many trace metals such as iron copper and manganese have lower concentrations in the surface waters of the north pacific ocean than in north atlantic surface waters however cobalt and zinc concentrations in north atlantic surface waters are often as low as those reported in the north pacific we studied the relationship between the distribution of cobalt zinc and phosphorus in surface waters of the western north atlantic ocean both metals show strong depletion in the southern sargasso sea a region characterized by exceedingly low dissolved inorganic phosphorus generally 4 nmol l 1 and measurable alkaline phosphatase activity alkaline phosphatase is a metalloenzyme typically containing zinc that cleaves phosphate monoesters and is a diagnostic indicator of phosphorus stress in phytoplankton in contrast to the north pacific ocean cobalt and zinc appear to be drawn down to their lowest values only when inorganic phosphorus is below 10 nmol l 1 in the north atlantic ocean lower levels of phosphorus in the atlantic may contribute to these differences possibly through an increased biological demand for zinc and cobalt associated with dissolved organic phosphorus acquisition this hypothesis is consistent with results of a culture study where alkaline phosphatase activity decreased in the model coccolithophore emiliania huxleyi upon zinc and cobalt limitation

scale dependence in earthquake processes and seismogenic structures we provide a positive answer to the question whether large earthquakes can be separated from small ones using various observations on the earthquake processes and seismogenic structures for california the boundary of separation is at m 5 this conclusion leads to the possibility of deterministic modeling of earthquake occurrence for prediction we recognize however that the system of earthquake occurrence involves nonlinear physics with many degrees of freedom we suggest that the geometrical barriers and asperities may be a good starting point for the modeling we also discuss the implication of our finding on the numerical simulation of earthquake rupture propagation and conclude that the model fault zone must be made thicker for a more realistic simulation of major earthquakes

a new spectral ratio method using narrow band coda envelopes evidence for non self similarity in the hector mine sequence 1 the use of local and regional s wave coda is shown to provide stable amplitude ratios that better constrains source differences between event pairs we first compared amplitude ratio performance between local and near regional s and coda waves in the san francisco bay region for moderate sized events then applied the coda spectral ratio method to the 1999 hector mine mainshock and its larger aftershocks we find 1 average amplitude ratio standard deviations using coda are 0 05 to 0 12 roughly a factor of 3 smaller than direct s waves for 0 2 f 15 0 hz 2 coda spectral ratios for the mw 7 0 hector mine earthquake and its aftershocks show a clear departure from self similarity consistent with other studies using the same datasets and 3 event pairs green s function and target events can be separated by 25 km for coda amplitudes without any appreciable degradation in sharp contrast to direct waves

cadmium chemical tracer of deepwater paleoceanography the oceanic distribution of cadmium resembles that of phosphorus because the cadmium content of foraminiferal shells is governed by the cadmium content of seawater planktonic and benthic fossil shells can be used to infer nutrient distributions within ancient oceans empirical studies demonstrate that cadmium in benthic foraminiferal shells is related to the bottom water composition through a proportionality constant d 2 9 this constant is the same for each of the species studied cibicidoides wuellerstorfi cibicidoides kullenbergi nuttallides umbonifera and uvigerina spp downcore cadmium data from high quality pacific and atlantic sediment cores suggest that the cadmium inventory of the ocean did not change significantly between the most recent glacial maximum and the present hence changes in the cadmium content of fossils at a site directly reflect changes in nutrient distributions due to altered oceanic circulation patterns studies of cadmium in pleistocene sediments show that deep ocean circulation patterns were significantly different during the most recent glacial maximum in the western north atlantic ocean the nutrient content of waters from 2500 to 3500 m was twice as high during glacials as during interglacial periods signifying an increase in the proportion of waters of antarctic origin in this depth interval and a decrease but not a cessation in the flux of north atlantic deep waters through this depth range below 3500 m the nutrient increase was greater indicating a higher proportion of antarctic bottom water above 2500 m the nutrient content was lower during glacial periods than it has been during interglacial times the cd content of high latitude north atlantic and southern ocean surface waters does not show a significant glacial interglacial change which argues against theories for changes atmospheric carbon dioxide that require changes in high latitude nutrient concentrations

mercury presence and speciation in the south atlantic ocean along the 40 s transect mercury hg natural biogeochemical cycle is complex and a significant portion of biological and chemical transformation occurs in the marine environment to better understand the presence and abundance of hg species in the remote ocean regions waters of south atlantic ocean along 40 s parallel were investigated during uk geotraces cruise ga10 total mercury thg methylated mercury mehg and dissolved gaseous mercury dgm concentrations were determined the concentrations were very low in the range of pg l femtomolar all hg species had higher concentration in western than in eastern basin thg did not appear to be a useful geotracer elevated methylated hg species were commonly associated with low oxygen water masses and occasionally with peaks of chlorophyll a both involved with carbon re cycling the overall highest mehg concentrations were observed in themixed layer 500m and in the vicinity of the gough island conversely dgm concentrations showed distinct layering and differed between the water masses in a nutrient like manner dgm was lowest at surface indicating degassing to the atmosphere and was highest in the upper circumpolar deep water where the oxygen concentration was lowest dgm increased also in antarctic bottom water at one station dimethylmercury was determined and showed increase in region with lowest oxygen saturation altogether our data indicate that the south atlantic ocean could be a source of hg to the atmosphere and that its biogeochemical transformations depend primarily upon carbon cycling and are thereby additionally prone to global ocean change

the cycling of iron zinc and cadmium in the north east pacific ocean insights from stable isotopes abstract dissolved stable isotope ratios of the transition metals provide useful information both for understanding the cycling of these bioactive trace elements through the oceans and tracing their marine sources and sinks here we present seawater dissolved fe zn and cd concentration and stable isotope ratio 56fe 66zn and 114cd profiles from two stations in the pacific ocean the safe station 30 n 140 w in the subtropical north east pacific from the geotraces ic2 cruise and the marginal san pedro basin 33 8 n 118 4 w within the south california bight these data represent to our knowledge the first full water column profiles for 66zn and 56fe from the open ocean north pacific and the first observations of dissolved 66zn and 114cd in a low oxygen marginal basin at the safe station 56fe is isotopically lighter throughout the water column 0 6 to 0 1 relative to irrm 014 compared to the north atlantic suggesting significant differences in fe sources or fe cycling between these two ocean basins a broad minimum in 56fe associated with the north pacific oxygen minimum zone omz

investigating the interaction between crescent spring and groundwater in a chinese dune lake environment using hydraulic gradient and isotope analysis methods this paper investigates the interaction between groundwater and groundwater dominated crescent spring in an aeolian sand environment to determine the drainage source of groundwater for the lake using hydraulic gradient and isotope analysis methods the precipitation is found to have an insignificant effect on the lake in an arid climate environment hydrogen and oxygen isotopic evidence presents at least two aquifer contributions that recharge 87 and 13 water supply of the lake respectively the flow direction of groundwater is theoretically established based on the hydraulic gradient and isotope analysis methods

the influence of hyporheic exchange on reach scale water budgets in a precambrian shield catchment quebec canada the influence of hyporheic exchange on water and solute budgets of streams is widely identified as important yet there is a notable absence of research identifying its role in precambrian shield headwater streams this research addressed this shortcoming by quantifying the proportions of solute mass loss net and gross water gains and losses for selected reaches over a single summer recession period six conservative tracer injections were performed on nine reaches of a 2 94 km2 catchment in gatineau park quebec canada from july to november 2011 high solute exchange occurred for all reaches despite most showing positive net discharge solute losses in stream reaches typically exceeded 10 and substantial gross water losses and gains indicate a high degree of bi directional water exchange along stream reaches both solute loss and the fraction of channel water involved in hyporheic exchange increased throughout the summer in response to a decrease in discharge and increase in the time of contact results support the assertion that reductions in groundwater contributions to streamflow throughout the summer baseflow period allow for greater exchange of water through hyporheic flowpaths which constitute the majority of gross channel losses and gains spatial inter reach variability in mass loss has been previously ascribed to watershed control on exchange potential in this catchment net discharge and gross hydrologic gains were inversely related to the average flowpath gradients within the valley bottom and local hillslope contributing areas copyright 2013 john wiley sons ltd

total dissolved zinc in the upper water column of the subarctic north east pacific abstract total dissolved zn concentrations are reported for winter and summer along the e w line p transect and for summer along s n line z transect extending from ocean station papa osp 50 n 145 w to the respective shelf waters surface water 10 m concentrations ranged from 0 04 nm in the open ocean to 0 9 nm at the canadian shelf station a clear gradient is evident with dissolved zn concentrations decreasing with increasing distance from shore along the e w transect in both summer and winter no consistent trend was observed along the s n transect low concentrations of zn 0 05 0 07 nm were observed in near surface water at osp in winter the vertical distribution of dissolved zn is oceanographically consistent showing a silicon like vertical profile concentrations of silicic acid and dissolved zn at depth are higher than those at equivalent depths in the atlantic as expected from deep water circulation patterns and build up in concentration of these elements dissolved zn si ratios in the upper 200 m indicate a trend of decreasing with distance from shore which infers a decoupling between dissolved zn and silicic acid in the upper ocean we hypothesise that the silicon like profile of dissolved zn is a result of recycling from relatively biologically resistant organic particulate phases that leads to profiles very similar to those of dissolved silicon other than at two stations where there is very high primary production there is no apparent horizontal relationship between total dissolved zn and chlorophyll a or production

a field investigation of groundwater surface water interaction in a fractured bedrock environment abstract to facilitate a better understanding of the exchange processes between a fractured rock aquifer and a bedrock stream a study of groundwater surface water interaction between twenty mile creek and the local aquifer in smithville ont was completed the points of interaction between the creek and the local aquifer were identified and quantified through the use of air photo interpretation detailed stream surveys electrical conductivity and temperature surveys isotopic analysis mixing calculations and point measurements of hydraulic head and discharge obtained using mini piezometers seepage meters and weirs the results indicate that the interaction between twenty mile creek and the local aquifer is extremely limited with greater than 95 of the groundwater within the study area underflowing the creek completely during baseflow conditions in addition it was observed that groundwater discharge in a bedrock stream environment occurs primarily through discrete point sources associated with open fractures as compared to more diffuse or continuous seepage zones often observed in a porous media environment the small quantity of groundwater discharging into twenty mile creek through these features has an electrical conductivity and isotopic signature consistent with shallow groundwater and most likely originates in the upper 3 7 m of bedrock although previous investigations have identified potentially open vertical fractures within the study area it is apparent that the fracture network has extremely poor vertical connections limiting groundwater exchange in the vicinity of the creek in addition the low velocity and discharge rate within the creek does not allow for incising into the bedrock as a result horizontal fractures do not play a significant role in the exchange process within the study area

the zn abundance and isotopic composition of diatom frustules a proxy for zn availability in ocean surface seawater we have developed cleaning methods for extracting diatomopal from bulk marine sediment samples for measurement of both zinc zn abundance and isotope composition this cleaning technique was then applied to a set of holocene core top samples from the southern ocean the measured 66zn reported relative to the jmclyon standard and zn si ratios from the southern ocean diatomopal samples range from 0 7 to 1 5 and from 14 to 0 9 mol mol respectively the zn abundance and isotope composition data show a clear correlation with opal burial rates and other oceanographic parameters in common with previous work we interpret the systematic changes in the zn si ratio to be linked to the variability in the concentrations of bioavailable zn in the ambient surface seawater where the diatom opal is formed this variability is likely to be primarily controlled by the degree to which zn is taken up into phytoplankton biomass the observed systematic pattern in the 66zn compositions of the diatomopal core top samples is similarly likely to reflect changes in the 66zn composition of the ambient zn in the surface waters above the core top sites which is progressively driven towards isotopically heavier values by preferential incorporation of the lighter isotopes into phytoplankton organic material thus the systematic relationship between zn isotopes and abundance observed in the core top diatomopal samples suggests a potential tool for investigating the biogeochemical cycling of zn in the past surface ocean for down core diatomopal material in this respect it may be possible to test hypotheses that attribute variations in atmospheric co2 on glacial interglacial timescales to the degree to which trace metals limited primary productivity in hnlc zones

groundwater surface water interactions in headwater forested wetlands of the canadian shield abstract groundwater and surface water interaction in two conifer swamps located in headwater catchments with contrasting till depth typical of the southern canadian shield were studied from june 1990 to august 1992 both swamps had little influence on the regulation or attenuation of seasonal runoff response in the catchment the two valley bottom swamps were connected to local aquifers but the upland wetland connection was continuous in the catchment with deeper till and ephemeral in the catchment with thin till rock ridges groundwater movement through the wetlands was restricted mainly to the surface peat layer in both wetlands because a large portion of inputs from shallow soil layers and stream inflows enter near the peat surface however differences in upland wetland connections resulted in contrasting hydrologic regimes in the two swamps during seasons with larger inputs both swamps were hydrologically connected to uplands and had a similar hydrology characterized by a high water table rapid storm response and predominance of saturated overland flow in summer upland inputs were absent in the catchment with thin till rock ridges resulting in cessation of baseflow and a lower water table that varied in response to variations in rainfall continuous upland inputs throughout the summer in the catchment with deeper tills 1 3 m sustained baseflow and kept the water table near the peat surface this study demonstrates the control of morphology and shallow subsurface geology on the hydrology of valley bottom swamps influenced by local aquifers

biogeochemical cycling of dissolved zinc along the geotraces south atlantic transect ga10 at 40 s the biogeochemical cycle of zinc zn in the south atlantic at 40 s was investigated as part of the uk geotraces program to date there is little understanding of the supply of zn an essential requirement for phytoplankton growth to this highly productive region vertical zn profiles displayed nutrient like distributions with distinct gradients associated with the water masses present surface zn concentrations are among the lowest reported for the world s oceans 2 0 97 n 460 our results suggest that the use of a global zn si relationship would lead to an underestimation of dissolved zn in deeper waters of the south atlantic by utilizing si and a new tracer zn our data indicate that the preferential removal of zn in the southern ocean prevented a direct return path for dissolved zn to the surface waters of the south atlantic at 40 s and potentially the thermocline waters of the south atlantic subtropical gyre the importance of zn for phytoplankton growth was evaluated using the zn soluble reactive phosphorus srp relationship we hypothesize that the low zn concentrations in the south atlantic may select for phytoplankton cells with a lower zn requirement in addition a much deeper kink at 500m in the zn srp ratio was observed compared to other oceanic regions key points dissolved zinc biogeochemical cycle investigated in the south atlantic ocean 2014 american geophysical union all rights reserved

circulation and water mass modification in the brazil malvinas confluence abstract the confluence between the brazil current and the malvinas current the brazil malvinas confluence bmc in the argentine basin is characterized by a complicated thermohaline structure favoring the exchanges of mass heat and salt between the subtropical gyre and the antarctic circumpolar current acc analysis of thermohaline properties of hydrographic sections in the bmc reveals strong interactions between the acc and subtropical fronts in the subantarctic front subantarctic mode water samw antarctic intermediate water aaiw and circumpolar deep water cdw warm become saltier by 0 4 0 08 0 3 0 02 and 0 6 c 0 1 respectively in the subtropical gyre aaiw and north atlantic deep water have cooled freshened by 0 4 0 07 and 0 7 c 0 11 respectively to quantify those acc subtropical gyre interactions a box inverse model surrounding the confluence is built the model diagnoses a subduction of 16 4 sv 1 sv 106 m3 s 1 of newly formed samw and aaiw under the subtro

variability of subantarctic mode water and antarctic intermediate water in the drake passage during the late twentieth and early twenty first centuries a time series of the physical and biogeochemical properties of subantarctic mode water samw and antarctic intermediate water aaiw in the drake passage between 1969 and 2005 is constructed using 24 transects of measurements across the passage both water masses have experienced substantial variability on interannual to interdecadal time scales samw is formed by winter overturning on the equatorward flank of the antarctic circumpolar current acc in and to the west of the drake passage its interannual variability is primarily driven by variations in wintertime air sea turbulent heat fluxes and net evaporation modulated by the el nino southern oscillation enso despite their spatial proximity the aaiw in the drake passage has a very different source than that of the samw because it is ventilated by the northward subduction of winter water originating in the bellingshausen sea changes in aaiw are mainly forced by variability in winter water properties resulting from fluctuations in wintertime air sea turbulent heat fluxes and spring sea ice melting both of which are linked to predominantly enso driven variations in the intensity of meridional winds to the west of the antarctic peninsula a prominent exception to the prevalent modes of samw and aaiw formation occurred in 1998 when strong wind forcing associated with constructive interference between enso and the southern annular mode sam triggered a transitory shift to an ekman dominated mode of samw ventilation and a 1 2 yr shutdown of aaiw production the interdecadal evolutions of samw and aaiw in the drake passage are distinct and driven by different processes samw warmed by 0 3 c and salinified by 0 04 during the 1970s and experienced the reverse trends between 1990 and 2005 when the coldest and freshest samw on record was observed in contrast aaiw underwent a net freshening by 0 05 between the 1970s and the twenty first century although the reversing changes in samw were chiefly forced by a 30 yr oscillation in regional air sea turbulent heat fluxes and precipitation associated with the interdecadal pacific oscillation with a sam driven intensification of the ekman supply of antarctic surface waters from the south contributing significantly too the freshening of aaiw was linked to the extreme climate change that occurred to the west of the antarctic peninsula in recent decades there a freshening of the winter water ventilating aaiw was brought about by increased precipitation and a retreat of the winter sea ice edge which were seemingly forced by an interdecadal trend in the sam and regional positive feedbacks in the air sea ice coupled climate system all in all these findings highlight the role of the major modes of southern hemisphere climate variability in driving the evolution of samw and aaiw in the drake passage region and the wider south atlantic and suggest that these modes may have contributed significantly to the hemispheric scale changes undergone by those waters in recent decades

silicon and zinc biogeochemical cycles coupled through the southern ocean zinc is vital for the physiology of oceanic phytoplankton the striking similarity of the depth profiles of zinc to those of silicate suggests that the uptake of both elements into the opaline frustules of diatoms and their regeneration from these frustules should be coupled however the zinc content of diatom opal is negligible and zinc is taken up into and regenerated from the organic parts of diatom cells thus since opaline frustules dissolve deep in the water column while organic material is regenerated in the shallow subsurface ocean there is little reason to expect the observed close similarity between zinc and silicate and the dissimilarity between zinc and phosphate here we combine observations with simulations using a three dimensional model of ocean circulation and biogeochemistry to show that the coupled distribution of zinc and silicate as well as the decoupling of zinc and phosphate can arise in the absence of mechanistic links between the uptake of zinc and silicate and despite contrasting regeneration length scales our simulations indicate that the oceanic zinc distribution is in fact a natural result of the interaction between ocean biogeochemistry and the physical circulation through the southern ocean hub our analysis demonstrates the importance of uptake stoichiometry in controlling ocean biogeochemistry and the utility of global scale elemental covariation in the ocean in understanding these controls zinc and silicon distributions co vary in much of the global oceans observations and numerical modelling suggest that this co variation can arise in the absence of mechanistic links between the uptake of zinc and silicate

advances in holocene mountain geomorphology inspired by sediment budget methodology the sediment budget which links sediment sources to sediment sinks with hydroclimatic and weathering processes mediating the response is applied to the analysis of sediments in three alpine lakes in british columbia we provide two ways of using the sediment budget as an integrating device in the interpretation of mountain geomorphology these approaches differ in their resolution and ability to budget the major components of the fine sediment cascade in glaciated environments taken together they provide an integrated index of landscape change over the holocene the first example compares the hydroclimatic controls of lake sedimentation for the last 600 years a d 1370 1998 preserved in varved sediments from two of the lake basins this hydroclimatological approach incorporates contemporary monitoring air photo analysis and detailed stratigraphy of sedimentation events within a single varve to infer the timing sources and preferred pathways of fine grained sediments reaching the lake basins the results indicate that glaciers hillslope and channel instability within the major subbasins are the principal sediment sources to the lake basins transitory sediment storage of glacially derived sediments within the channels is believed to modulate the episodic and more frequent delivery of sediments from adjacent hillslope and fluvial storage sites and direct routing of glacial rock flour during years of prolonged glacial melt the second example relying on the phosphorus geochemistry of sediments in an alpine lake basin considers the evolution of phosphorus forms from mineral to occluded and organic fractions as a function of the soil development inherent slope instability and repeated cycles of glaciation and neoglaciation over the holocene this geochemical approach demonstrates that both neoglaciation and full glaciation have essentially zeroed the system in such a way that a high proportion of mineral phosphorus remains in the present lake sediments and the bioavailability of phosphorus a key to ecosystem development is low both examples illustrate the importance of variable sediment sources the seasonality frequency and magnitude of sediment transfers and the profound influence of ice cover over contemporary neoglacial and pleistocene time scales they also signal the value of including both clastic and dissolved components in the sediment budget d 2003 elsevier science b v all rights reserved

a preliminary assessment of water partitioning and ecohydrological coupling in northern headwaters using stable isotopes and conceptual runoff models we combined a conceptual rainfall runoff model and input output relationships of stable isotopes to understand ecohydrological influences on hydrological partitioning in snow influenced northern catchments six sites in sweden krycklan canada wolf creek baker creek dorset scotland girnock and the usa dry creek span moisture and energy gradients found at high latitudes a meta analysis was carried out using the hydrologiska byrans vattenbalansavdelning hbv model to estimate the main storage changes characterizing annual water balances annual snowpack storage importance was ranked as wolf creek krycklan dorset baker creek dry creek girnock the subsequent rate and longevity of melt were reflected in calibrated parameters that determine partitioning of waters between more rapid and slower flowpaths and associated variations in soil and groundwater storage variability of stream water isotopic composition depends on the following i rate and duration of spring snowmelt ii significance of summer autumn rainfall and iii relative importance of near surface and deeper flowpaths in routing water to the stream flowpath partitioning also regulates influences of summer evaporation on drainage waters deviations of isotope data from the global meteoric water line showed subtle effects of internal catchment processes on isotopic fractionation most likely through evaporation such effects are highly variable among sites and with seasonal differences at some sites after accounting for climate evaporative fractionation is strongest at sites where lakes and near surface runoff processes in wet riparian soils can mobilize isotopically enriched water during summer and autumn given close soil vegetation coupling this may result in spatial variability in soil water isotope pools available for plant uptake we argue that stable isotope studies are crucial in addressing the many open questions on hydrological functioning of northern environments 2015 the authors hydrological processes published by john wiley sons ltd

crustal structure in the southern apennines from teleseismic receiver functions while the upper crustal structure of the southern apennines is known lack of control on the deep structure allows competing thin skinned and thick skinned models of the orogen in thin skinned models the detachment decouples a stack of rootless nappes from the basement in thick skinned models basement is involved in the most recent phase of thrusting to examine crustal structure we use teleseismic data from the calabria apennine tyrrhenian subductionaccretion collision network cat scan array in southern italy we use receiver functions rf processed into a common conversion point stack to generate images of the crust interpretation and correlation to geological structure are done using inversions of individual station rfs we focus on a shallow discontinuity where p to s conversions occur in the foreland it corresponds to velocity jumps between carbonate and clastic strata with basement a similar interpretation for the apennines provides the most parsimonious explanation and supports a thick skinned interpretation in a thick skinned reconstruction the amount of shortening is much smaller than for a thin skinned model this implies considerably less pliocene pleistocene shortening across the apennines and suggests an east southeast motion of the calabrian arc subparallel to the southern apennines rather than a radial expansion of the arc

evidence of deep and bottom water formation in the western weddell sea abstract during ice station polarstern ispol r v polarstern cruise ant xxii 2 november 2004 january 2005 hydrographic and tracer observations were obtained in the western weddell sea while drifting closely in front of the larsen ice shelf these observations indicate recently formed weddell sea bottom water which contains significant contributions of glacial melt water in its upper part and high salinity shelf water in its lower layer the formation of this bottom water cannot be related to the known sources in the south the filchner ronne ice shelf we show that this bottom water is formed in the western weddell sea most likely in interaction with the larsen c ice shelf by applying an optimum multiparameter analysis omp using temperature salinity and noble gas observations helium isotopes and neon we obtained mean glacial melt water fractions of about 0 1 in the bottom water on sections across the weddell gyre farther north melt water fractions are still on the order of 0 04 using chlorofluorocarbons cfcs as age tracers we deduced a mean transit time between the western source and the bottom water found on the slope toward the north 9 3 years this transit time is larger and the inferred transport rate is small in comparison to previous findings but accounting for a loss of the initially formed bottom water volume due to mixing and renewal of weddell sea deep water a formation rate of 1 1 0 5 sv in the western weddell sea is plausible this implies a basal melt rate of 35 19 gt year or 0 35 0 19 m year at the larsen ice shelf this bottom water is shallow enough that it could leave the weddell basin through the gaps in the south scotia ridge to supply antarctic bottom water these findings emphasize the role of the western weddell sea in deep and bottom water formation particularly in view of changing environmental conditions due to climate variability which might induce enhanced melting or even decay of ice shelves

anisotropy and depth related heterogeneity of hydraulic conductivity in a bog peat ii modelling the effects on groundwater flow anisotropy and heterogeneity of hydraulic conductivity k are seldom considered in models of mire hydrology we investigated the effect of anisotropy and heterogeneity on groundwater flow in bog peat using a steady state groundwater model in five model simulations four sets of k data were used the first set comprised measured k values from an anisotropic and heterogeneous bog peat these data were aggregated to produce the following simplified data sets an isotropic and heterogeneous distribution of k an isotropic and homogeneous distribution and an anisotropic and homogeneous distribution we demonstrate that where anisotropy and heterogeneity exist groundwater flow in bog peat is complex fine scale variations in k have the potential to influence patterns and rates of groundwater flow however for our data at least it is heterogeneity and not anisotropy that has the greater influence on producing complex patterns of groundwater flow we also demonstrate that patterns and rates of groundwater flow are simplified and reduced when measured k values are aggregated to create a more uniform distribution of k for example when measured k values are aggregated to produce isotropy and homogeneity the rate of modelled seepage is reduced by 28 we also show that when measured k values are used the presence of a drainage ditch can increase seepage through a modelled cross section our work has implications for the accurate interpretation of hydraulic head data obtained from peat soils and also the understanding of the effect of drainage ditches on patterns and rates of groundwater flow

high stress strike slip faults in the apennines an example from the 2002 san giuliano earthquakes southern italy 1 under the hypotheses that the high frequency part of the seismic spectrum is controlled by source duration and by peak slip velocity we applied a recent coda envelope methodology to obtain stable relative source estimates between selected mainshocks and their aftershocks we computed stable mainshock aftershock s wave spectral ratios and used a simple source model in order to quantify the scaling of the seismic sources of the san giuliano sequence southern italy from the analysis of the ratios obtained between the main shock of 10 31 2002 and 11 aftershocks and of those computed between the other main event of the sequence of 11 01 2002 and 10 aftershocks we observe that the scaling relationships m0 fc 3 holds with 0 89 0 05 despite the strong discrepancy between the moment magnitude and the high frequency ground motion excited by the main shocks ml was much lower than mw that would indicate low stress drop sources we compute anomalously high stress parameters for both events by comparison the same analysis was carried out on seismic data of the hector mine seismic sequence the main event of october 16 1999 mw 7 0 and six of its aftershocks we found m0 fc 3 with 0 8 0 4

geophysical characterization redox zonation and contaminant distribution at a groundwater surface water interface three transects along a groundwater surface water interface were characterized for spatial distributions of chlorinated aliphatic hydrocarbons and geochemical conditions to evaluate the natural bioremediation potential of this environmental system partly on the basis of ground penetrating radar measurements a conductive sediment layer was detected from the shore out to at least 300 m offshore which exhibited gradients in redox pairs and contaminant profiles the cis dichloroethene and 1 chloroethene were predominant in the presence of elevated methane and ferrous iron concentrations and depressed sulfate and aquifer solids bound iron concentrations the shallow monitoring points were generally hypoxic to aerobic and exhibited values of specific conductance reflective of near shore lake water indicating reoxygenation of the contaminant plume due to wave infiltration the barge transect yielded trace contaminant concentrations and showed evidence of sulfate reduction these analyses contributed to the understanding of processes affecting contaminant fate and transport at near shore mixing zones

controls on the barium isotope compositions of marine sediments abstract the accumulation of barium ba in marine sediments is considered to be a robust proxy for export production although this application can be limited by uncertainty in baso4 preservation and sediment mass accumulation rates the ba isotope compositions of marine sediments could potentially record insights into past changes in the marine ba cycle which should be insensitive to these limitations enabling more robust interpretation of sedimentary ba as a proxy to investigate the controls on the ba isotope compositions of marine sediments and their potential for paleo oceanographic applications we present the first ba isotope compositions results for sediments as well as overlying seawater depth profiles collected in the south atlantic variations in ba isotope compositions of the sediments predominantly reflect changes in the relative contributions of detrital and authigenic ba sources with open ocean sediments constraining the isotope composition of authigenic ba to be ba 138 134 0 1 this value is consistent with the average isotope composition inferred for sinking particulate ba using simple mass balance models of ba in the overlying water column and is hypothesized to reflect the removal of ba from the upper water column with an associated isotopic fractionation of ba diss part 138 134 0 4 to 0 5 perturbations to upper ocean ba cycling due to changes in export production and the supply of ba via upwelling should therefore be recorded by the isotope compositions of sedimentary authigenic ba such insights will help to improve the reliable application of ba accumulation rates in marine sediments as a proxy for past changes in export production

surface water groundwater interaction near shallow circular lakes flow geometry in three dimensions steady flow regimes for three dimensional lake aquifer systems are studied via idealized mathematical models that are extensions of earlier simplified vertical section models of interaction between shallow lakes and underlying aquifers the present models apply to a shallow circular lake at the surface of a rectangular aquifer of finite depth yielding a truly three dimensional representation of the resulting flow system flux boundary conditions are applied at the ends of the aquifer with net vertical recharge or evapotranspiration at the water table the lake is defined by a region with constant head by determining and visualizing solutions to the discretized saturated flow equations a range of possible flow regimes is identified and their topological properties are studied tools for analyzing flow regimes are described including a method for locating and mapping three dimensional dividing surfaces within steady flow fields results show strong similarities between two and three dimensional systems including a large number of flow through recharge and discharge regimes and reverse flow cells flow lines calculated on a vertical plane through the middle of a lake resemble but are not identical to two dimensional streamlines for a range of aquifer flow and recharge conditions estimates of the widths and depths of capture and release zones for various lake aquifer geometries are asymptotic to earlier results for two dimensional systems numerical predictions are compared with analytical results for certain limiting flow regimes

alluvial fan and wetland interactions evidence of seasonal slope wetlands from the silurian of south central wales uk distal environs of the ludlow age trichrug formation from south central wales uk detail deposition on the outer fringe of an ephemeral debris flow dominated alluvial fan debrites and subordinate sheetflood deposits are interbedded with sporadic thin sandstone dominated heterolithic units deposited in shallow ephemeral ponds in the axial valley the latter slope wetland system fringed the permeable alluvial fan deposits being maintained by streamflow precipitation and ground water recharge a prolonged high water table is indicated by low chroma intervals interpreted as the result of gleying a variety of redoximorphic indicators including colour mottling and ferricrete concretions are evidence of iron mobilization and concentration associated with a seasonally fluctuating water table the slope wetlands were colonized periodically by skolithos generating organisms most likely to have been arthropods the widespread occurrence of redoximorphic indicators and ferricrete contrasts markedly with calcrete vertisols in penecontemporaneous continental deposits lower old red sandstone of the region it is likely that the alluvial fan toe area was the site of a wetland depression which maintained a high though fluctuating water table in contrast the alluvial channel reaches of the surrounding drainage network were significantly better drained with floodplains prone to wetting and drying and vertisol palaeopedogenesis

pervasive sources of isotopically light zinc in the north atlantic ocean abstract in this study we report seawater dissolved zinc zn concentration and isotope composition 66 zn from the geotraces ga01 geovide section in the north atlantic across the transect three subsets of samples stand out due to their isotopically light signature those close to the reykjanes ridge those close to the sediments and those pervasively in the upper ocean similar to observations at other locations the hydrothermal vent of the reykjanes ridge is responsible for the isotopically light zn composition of the surrounding waters with an estimated source 66 zn of 0 42 this isotopically light zn is then transported over a distance greater than 1000 km from the vent sedimentary inputs are also evident all across the trans atlantic section highlighting a much more pervasive process than previously thought these inputs of isotopically light zn ranging from 0 51 to 0 01 may be caused by diffusion out of zn rich pore waters or by dissolution of sedimentary particles the upper north atlantic is dominated by low 66 zn a feature that has been observed in all zn isotope datasets north of the southern ocean using macronutrient to zn ratios to better understand modifications of preformed signatures exported from the southern ocean we suggest that low upper ocean 66 zn results from addition of isotopically light zn to the upper ocean and not necessarily from removal of heavy zn through scavenging though the precise source of this isotopically light upper ocean zn is not fully resolved it seems possible that it is anthropogenic in origin this view of the controls on upper ocean zn is fundamentally different from those put forward previously

spatio temporal variations of hyporheic flow in a riffle step pool sequence subsurface flow in streambeds can vary at different scales in time and space recognizing this variability is critical for understanding biogeochemical and ecological processes associated with the hyporheic zone the aim of this study was to examine the variability of hydraulic conductivity k vertical hydraulic gradients vhgs and subsurface fluxes over a riffle step pool sequence and at a high spatio temporal resolution a 20 m reach was equipped with a network of piezometers in order to determine the distribution of vhgs and k during a summer month temporal variations of vhgs were regularly surveyed and for a subset of piezometers the water level was automatically recorded at 15 min intervals by logging pressure transducers additionally point dilution tests were carried out on the same subset of piezometers whereas the distribution of vertical fluxes can be derived from k and vhg values point dilution tests allow for the estimation of horizontal fluxes where no vhg is detectable results indicate that spatially vhgs switched from upwelling to downwelling across lateral as well as longitudinal sections of the channel vertical fluxes appeared spatially more homogeneous than vhgs suggesting that the latter can be a poor indicator of the intensity of flow finally during flow events some vhgs showed little or no fluctuations this was interpreted as the result of a pressure wave propagating from upstream through highly diffusive alluvial sediments

hydrology of subarctic canadian shield soil filled valleys the canadian shield landscape includes bedrock uplands and valleys infilled with soil a site near yellowknife in subarctic canada was studied to elucidate the hydrological behaviour of soil filled valleys a suite of hydrological processes was found to be important in the studied valley including snowmelt and rainfall ground frost development evaporation infiltration lateral inflow from adjacent uplands and surface and subsurface flows valley storage requirements during snowmelt are met by local meltwater infiltration but lateral inflows in the summer are needed to satisfy the storage before runoff can be generated from the valley the valleys perform three functions of collecting vertical and lateral water inputs retaining and losing the water held in storage and transferring water down the valley and generating local outflow unlike channel flows in humid areas runoff from the upper valley has to meet the storage demands of the lower valley segments often causing seepage loss along flow paths to render the flows intermittent a fill and spill runoff system is proposed in which the valley physiography results in a series of segments with varying storage conditions as water is supplied to the valley each segment has to be filled until its storage threshold for runoff is exceeded then subsurface or surface flows will be generated but these flows may be arrested to furnish water to satisfy the storage requirements of the segments downstream such a flow system applies also to other valleys in the shield environment

winter and summer distributions of copper zinc and nickel along the international geotraces section gipy05 insights into deep winter mixing abstract first measurements of labile dissolved copper ldcu and dissolved zinc dzn and nickel dni in the atlantic sector of the southern ocean in winter are compared with summer data at reoccupied stations in order to better understand the winter reset state and supply of these trace metals to support productivity in summer vertical profiles of zinc behaved similarly to silicate si and increased from sub nanomolar surface concentrations to 8 nmol kg 1 in bottom waters copper profiles also resembled si and were typically 1 nmol kg 1 in surface waters and increased to 3 nmol kg 1 at depth first summer nickel data reported from this transect displayed comparatively higher surface concentrations of 4 6 nmol kg 1 increasing more rapidly to local intermediate depth maximums between 6 5 and 7 0 nmol kg 1 similar to phosphate po4 trace metal seasonality was most apparent in the mixed layer where the average of winter concentrations within the mixed layer exceeded summer values by approximately 0 2 nmol kg 1 for ldcu 1 2 nmol kg 1 for dzn and 0 3 nmol kg 1 for dni owing to low utilization under unfavourable growth conditions for phytoplankton in an effort to estimate the winter reserve two scenarios were considered scenario 1 accounted for in situ mixed layer depths mld where the winter reserve inventory was calculated by subtracting the summer depth integrated metal inventory surface to summer mld from the winter equivalent surface to winter mld scenario 2 assumed a constant mixed layer taken as the depth of the maximum winter mixed layer where summer depth integrated metal inventories surface to maximum winter mld were subtracted from the winter equivalents surface to maximum winter mld results for scenario 1 were predominantly dependent on the mixed layer depth which varied spatially and seasonally scenario 2 showed a southwards increase in the winter reserve inventory suggesting a greater role for entrainment at higher latitudes in this region this is however heavily dependent on other physical processes controlling vertical trace metal supply e g diapycnal diffusion ekman upwelling downwelling zinc r2 0 75 and copper r2 0 73 were strongly correlated with si throughout the study implicating diatoms as strong controllers of their biogeochemical cycling nickel was more strongly correlated with po4 in the upper water column r2 0 75 as compared to the whole water column r2 0 52 while in the deep ocean nickel appears to correlate with si although more deep ocean data is needed to confirm this trace metal to major nutrient ratios were higher in winter suggesting reduced micronutrient requirement relative to macronutrients under stressed but low productivity conditions this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

the relationship between zinc its isotopes and the major nutrients in the north east pacific abstract trace metal micronutrients play key roles in photosynthesis by oceanic phytoplankton though they are required in much smaller amounts than the major nutrients p n si their bioavailable forms are also present in the seawater solution at much lower levels relationships between the dissolved chemistry of the nutrient type trace metals their stable isotope variations as well those of the major nutrients have highlighted the importance of biological and physical processes in the southern ocean in controlling their oceanic biogeochemistry however the first order southern ocean processes are overprinted by vertical cycling in other parts of the ocean particularly upwelling regions remote from the southern ocean with the north pacific standing out in particular here we present new zinc zn concentration and isotope as well as major nutrient data for the ne pacific and couple these new data with a compilation of published data from across the region with the objective of better understanding the impact of this important region on oceanic biogeochemical cycles the new zn isotope data for two stations along line p p04 and p26 show a large range in 66 zn in the upper ocean 0 4 up to 1 associated with a very small isotope fractionation but extreme depletion of the dissolved pool during photic zone biological uptake and the regeneration of this cellular zn at very shallow depths 50 m beneath this the two profiles approach the 66 zn value of 0 5 seen throughout the deep ocean by about 500 m the minimum 66 zn resulting from regeneration is associated with very high zn concentrations particularly at the marginal p04 station where diatoms dominate the phytoplankton ecology combining the new data with published zn and major nutrient concentrations from across the north pacific emphasises the role of vertical biological cycling in controlling regional biogeochemistry in the north pacific resulting in the partial overprinting of biogeochemical signatures transported out of the southern ocean by the ocean circulation zinc isotope data document the uptake of this metal into diatoms and the co regeneration of zn with phosphate in the upper water column silica in contrast is regenerated at greater depth resulting in a decoupling of the zn si correlation that is set in the southern ocean and that dominates the atlantic previous work has suggested that the decoupling of zn and si in the subarctic north pacific results from removal of zn and other metals to water column particulate sulphide in our dataset and in the compilation of data documenting relationships between zn and the major nutrients across the north pacific this decoupling is clearly due to the different lengthscales of regeneration for organic matter zn and p and diatom opal si

source analysis of the 2002 molise southern italy twin earthquakes 10 31 and 11 01 1 on october 31 2002 a moderate size earthquake mw 5 8 occurred in molise region southern italy causing loss of young human lives in a school collapse and destructions in several villages the day after a slightly smaller earthquake happened a few kilometers westward from the first one without making strong damage we use a complete set of seismological data global regional and local including both body and surface waves to better understand the source process of these two events we show that the two earthquakes are similar in terms of hypocentral depth focal mechanism and source kinematics moreover the imaged slip zones are almost contiguous which makes the time delay between the two shocks 29 hours an open question the identified updip rupture propagation has amplified the radiation usually created by such mw 5 8 earthquakes at 15 20 km depth we model a maximum acceleration zone in agreement with location of damaged villages

the distribution of dissolved zinc in the atlantic sector of the southern ocean the distribution of dissolved zinc zn was investigated in the atlantic sector of the southern ocean in the austral autumn of 2008 as part of the ipy geotraces expedition zero drake research focused on transects across the major frontal systems along the zero meridian and across the drake passage there was a strong gradient in surface zinc concentrations observed across the antarctic polar front along both transects and high zinc levels were found in surface waters throughout the southern ocean vertical profiles for dissolved zinc showed the presence of local minima and maxima in the upper 200 m consistent with significant uptake by phytoplankton and release by zooplankton grazing respectively highest deep water zinc concentrations were found in the centre of the weddell gyre associated with central intermediate water ciw a water mass which is depleted in o2 elevated in co2 and is regionally a cfc minimum our data suggests that the remineralization of sinking particles is a key control on the distribution of zn in the southern ocean disappearance ratios of zinc to phosphate zn p in the upper water column increased southwards along both transects and based on laboratory studies they suggest slower growth rates of phytoplankton due to iron or light limitation zinc and silicate were strongly correlated throughout the study region but the disappearance ratio zn si was relatively uniform overall except for the region close to the ice edge on the zero meridian

landscape controls on the hydrology of stream riparian zones abstract increased knowledge of hydrology is essential to an understanding of the water quality function of stream riparian zones we examined the effect of upland surficial aquifer size topography and riparian sediment lithology on the subsurface hydrology of eight riparian sites on glacial till and outwash landscapes in southern ontario canada riparian sites had a permanent subsurface hydrologic connection to the adjacent upland in landscapes where upland permeable sediment depths were 2 15 m in contrast a hydrologic connection was absent in summer and autumn at riparian sites with 5 where the riparian zone was level to gently sloping

the biogeochemical cycling of zinc and zinc isotopes in the north atlantic ocean zinc zn is a marine micronutrient with an overall oceanic distribution mirroring the major macronutrients especially silicate seawater zn isotope ratios 66zn are a relatively new oceanographic parameter which may offer insights into the biogeochemical cycling of zn to date the handful of published studies of seawater 66zn show the global deep ocean to be both remarkably homogeneous approximately 0 5 and isotopically heavier than the marine sources of zn 0 1 to 0 3 here we present the first high resolution oceanic section of 66zn from the u s geotraces ga03 north atlantic transect from lisbon to woods hole throughout the surface ocean biological uptake and release of isotopically light zn together with scavenging of heavier zn leads to large variability in 66zn in the ocean below 1000 m 66zn is generally homogeneous 0 50 0 14 2 sd though deviations from 0 5 allow us to identify specific sources of zn the mediterranean outflow is characterized by 66zn of 0 1 to 0 3 while margin sediments are a source of isotopically light zn 0 5 to 0 8 which we attribute to release of nonregenerated biogenic zn mid atlantic ridge hydrothermal vents are also a source of light zn close to 0 5 though zn is not transported far from the vents understanding the biogeochemical cycling of zn in the modern ocean begins to address the imbalance between the light 66zn signature of marine sources and the globally homogeneous deep oceans 66zn of 0 5 on long timescales with overall patterns pointing to sediments as an important sink for isotopically light zn throughout the oceans

iron and silicic acid concentrations regulate si uptake north and south of the polar frontal zone in the pacific sector of the southern ocean abstract we investigated the relative roles of fe and silicic acid availabilities in regulating si uptake rates across the polar frontal zone in the pacific sector of the southern ocean 59 68 s 170 w during the us jgofs antarctic environment southern ocean process study aesops meridional gradients in silicic acid concentration si oh 4 of about 0 25 0 56 m km 1 were observed in this area during austral spring and summer 1997 1998 with si oh 4 ranging from 32 si oh 4 and 15 no 3 uptake rates biogenic silica concentrations and si oh 4 no3 uptake ratios fe addition had little or no effect on si uptake rates in enrichments conducted in the low si waters north of the si gradient however fe addition increased si uptake rates 3 5 times over controls in enrichments conducted in the high si waters south of the gradient in both spring and summer fe addition decreased si oh 4 no3 uptake ratios by 2 5 times largely due to stimulation of no3 uptake rates zn addition had no effect on si oh 4 and no3 uptake rates short term 24 h si additions had varying effects on si uptake rates depending on season and location in spring additions of 40 m si to water from bottle enrichments conducted north of the si gradient in situ si oh 4 15 m did not increase si uptake rates initially but did increase uptake rates after 8 days in the summer enrichment north of the si gradient in situ si oh 4 5 m 50 m si additions doubled in situ si uptake rates in the initial water collected for the enrichment and increased si uptake rates as much as 16 fold during the experiment south of the si gradient where in situ si oh 4 was 40 m in both spring and summer si addition had no effect on in situ si uptake rates in the initial enrichment water nor on any si uptake rates measured during the experiment our results indicate that both fe and si availabilities regulate si uptake rates and silica production in the southern ocean along 170 w fe limitation appears to restrict si uptake rates south of the si gradient and plays a role in preventing si depletion south of the acc where ambient si oh 4 never fell below 40 m during 1997 1998 our experiments in the seasonal ice zone at 62 suggest that si uptake in this area switched from being fe limited in the spring when in situ si oh 4 was 40 m to si limited in the summer when si oh 4 was

zinc and nickel isotopes in seawater from the indian sector of the southern ocean the impact of natural iron fertilization versus southern ocean hydrography and biogeochemistry abstract the southern ocean is the site of 20 of global ocean carbon export and the origin of water masses that significantly impact the chemistry of the global ocean much of the southern ocean is a high nutrient low chlorophyll hnlc region iron is the primary limiting nutrient for phytoplankton growth and may also be an important control on the biogeochemistry of the water masses emanating from the southern ocean here we investigate the response of zn and ni and their isotopes to natural fe fertilization from southern ocean islands using samples collected during the keops 2 oct nov 2011 program in the early austral spring near the kerguelen plateau indian sector of the southern ocean zinc and ni concentrations show depth distributions and relationships to major nutrients that are very similar to published data from the atlantic sector of the southern ocean away from island fertilization as in the atlantic sector and other regions outside the southern ocean there is a slight minimum in 66zn at about 100 150 m depth and a slightly heavier value at the surface at the keops 2 sites the light sub surface zn isotopes occur at the depth level where measured chl a has declined to near zero the heaviest zn isotope values in either the atlantic or indian sectors occur in bottom waters are associated with samples that show high dissolved si relative to zn these latter represent possible evidence for a heavy input directly to deep water or from sediment and the zn si 66zn systematics are consistent with a source in diatom opal nickel concentrations show much less variation than those of zn with the most depleted surface value only 15 20 lower than those in upwelled deep water in the southern ocean these small variations in ni concentration are associated with no significant variability in ni isotopes as also previously observed in the atlantic sector overall the key feature of the dataset is the apparent absence of any significant impact of natural fe fertilization on the distribution of zn and ni with the dominant control being the station location relative to the polar front in both the atlantic and indian sectors zinc and ni isotopes are invariant in surface waters whether inside or outside the fertilized zone and whether south or north of the polar front this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

groundwater hydrology of boreal peatlands above a bedrock tunnel drainage impacts and surface water groundwater interactions summary little attention has been given to the pattern of hydrological connectivity between peatlands and water bearing fracture zones in crystalline bedrock the construction of the railway tunnel romeriksporten provided an opportunity for studying impacts of bedrock tunnelling on peatland hydrology and the hydraulic connectivity between peat deposits and deeper layers in an area with fractured precambrian gneisses exposed bedrock and surficial covers of thin till deposits and peatsoils above the tunnel the water level in peat wells fluctuated with maximum depths up to 3 m and water that otherwise would have generated surface runoff infiltrated in the peat drawdowns of the groundwater table in peatlands were observed as far as 340 m away from the tunnel trace the deep drainage base provided prolonged water table drawdowns in peatlands in dry periods and differential settlements in drained peatsoils resulted in secondary changes in patterns of surface water storage and flow the groundwater drawdowns were influenced by the balance between tunnel leakage and water supplies from catchments and the wetland position within the groundwater flow system deep and simultaneous lowering and fluctuations of hydraulic heads in wells in the peat the subpeat sediments and the bedrock above the tunnel demonstrated hydraulic connectivity between the peat layers and the bedrock and revealed vertical flow even through highly humified peat layers in the catotelm this shows that in peatlands with a subsurface of a relatively thin till cover above fractured crystalline bedrock favourable conditions for groundwater flow from peatsoils to rock are not always restricted to a few specific sites and indicates that attention should be given to the influence of peat water bedrock water connectivity on impacts of groundwater exploitation droughts and climate changes in such areas

what we can and cannot learn about earthquake sources from the spectra of seismic waves earthquake sources are commonly viewed as shear dislocations this imposes distinct limitations on what source parameters can be realistically determined from radiated shear wave spectra first the slip velocity on the fault is the real parameter that controls the strength of the high frequency radiation it can be directly determined from acceleration spectra by fitting their high frequency level second the relationship between corner frequency of the spectrum and the radius of the source is fundamentally unclear as a result the source dimensions cannot be accurately determined from the spectra such an estimate would be as accurate as any other informed guess third the stress drop only serves as a proxy for the source radius in the relationship between the radius and the corner frequency it thus cannot be reliably determined from the spectra the quantity usually obtained from the spectra and referred to as the stress drop is a poorly defined parameter that may bear little relevance to the actual stresses acting on faults this parameter has little meaning unless converted to the maximum slip velocity which is the only quantity that can be accurately determined from the spectra the typical value of stress drop of 100 bars established from the spectra of california events may imply that the typical slip velocities have been on the order of 0 5 m sec although it is more accurate to determine slip velocities directly from the spectra

the relationship between cadmium and phosphate in the atlantic ocean unravelled abstract cadmium cd is not generally considered a nutrient element but behaves like a nutrient in the oceans and might play an important role in ocean biology after all the relationship between cd and the nutrient phosphate po4 has been studied for over 40 yrs but the debate on the driving mechanism and reason behind the kink a change in the steepness of the slope is ongoing using new data of high accuracy and spatial resolution covering the west atlantic ocean from north to south in combination with a robust extended optimum multiparameter eomp water mass model we show that mixing between different water masses is the dominant factor explaining the observed correlation and its kink regeneration of cd via remineralisation explains the smaller scale variability notably in the surface ocean observations imply the availability of cd in surface waters determines the cd uptake and thus the cd po4 remineralisation ratio this ratio is variable between different ocean regions notably between the northern and southern high latitude oceans due to their role in deep water formation both the northern and southern high latitude oceans are a driving factor in the atlantic and global cd and po4 relation outside the atlantic ocean the classical kink is not expected but the relationship is by no means linear most likely this is due to the interaction between low latitude surface waters and subsurface waters from high latitude origin but more data are required to assess this in detail

swat cs revision and testing of swat for canadian shield catchments summary canadian shield catchments are under increasing pressure from various types of development e g mining and increased cottagers and changing climate within the southern part of the canadian shield catchments are generally characterized by shallow forested soils with high infiltration rates and low bedrock infiltration generating little overland flow and macropore and subsurface flow are important streamflow generation processes large numbers of wetlands and lakes are also key physiographic features and snow processes are critical to catchment modeling in this climate we have revised the existing publicly available swat version 2009 10 1 beta 3 to create swat cs a version representing hydrological processes dominating canadian shield catchments where forest extends over precambrian shield bedrock prior to this study very few studies applying swat to canadian shield catchments exist we have found three we tested swat cs using the harp lake catchment dataset an ontario ministry of environment research station located in south central ontario simulations were evaluated against 30 years of observational data including streamflow from six headwater sub catchments 0 1 1 9 km2 outflow from harp lake 5 4 km2 and five years of weekly snow water equivalent swe the best nash sutcliffe efficiency nse results for daily streamflow calibration daily streamflow validation and swe were 0 60 0 65 and 0 87 respectively for sub catchment hp4 with detailed land use and soil data for this range of catchment scales land cover and soil properties were found to be transferable across sub catchments with similar physiographic features namely streamflow from the remaining five sub catchments could be modeled well using sub catchment hp4 parameterization the harp lake outflow was well modeled using the existing reservoir based target release method generating nses of 0 72 and 0 67 for calibration and verification periods respectively with significant changes to the infiltration module introducing macropore flow and reduced bedrock percolation more than 90 of interflow was generated close to the soil bedrock interface and the contribution of groundwater flow to total runoff was reduced to small amounts consistent with hydrological process understanding in this terrain these two changes also allowed for a positive linear relationship between nse of swe and q whereas prior to these changes there was a negative relationship with these key revisions to the infiltration and bedrock percolations modules it is concluded that swat cs can reasonably capture key hydrological processes within canadian shield catchments further testing will examine water quality modeling and larger scale applications

the interaction of lakes with variably saturated porous media numerical simulation of variably saturated porous media indicates that groundwater recharge is variable in time and space depending on the thickness of the unsaturated zone through which infiltrating water must move the resulting complex transient groundwater flow systems have significant impact on contiguous surface water in very permeable media small local closed groundwater flow systems can develop and dissipate within a few weeks to several months after major recharge these have a direct effect on contiguous surface water by alternately causing seepage to and seepage from the surface water the transient nature of these flow systems indicates that reversals of the direction of groundwater flow may be common in less permeable media the same complex flow systems may occur but the time for development and dissipation is much greater for example it is conceivable that small local flow systems may exist for many months or years as a result of major recharge therefore directions of flow in such systems are more stable and the effect on contiguous surface water also is more stable the findings of this study indicate that wells and groundwater quality sampling sites need to be carefully located to define accurately water table configuration groundwater recharge direction of seepage through the beds of surface water bodies and complex geochemical processes related to changing directions of groundwater flow

physical properties governing groundwater flow in a glacial till catchment abstract hydraulic conductivity surface topography and sediment thickness influence the spatial and temporal pattern of groundwater flow and stream discharge in an unconfined aquifer in a 3 7ha headwater catchment in central ontario canada groundwater levels in the soils adjacent to the stream also significantly influence the magnitude and spatial distribution of stream discharge topographic convergence in plan and decreasing sediment thickness along flowpaths result in surface saturation and groundwater discharge hillslope gradients adjacent to discharge areas determination how fluctuating groundwater levels influence the extent of spatial variations in surface saturation and saturation within the soils as a result of spatial differences in hillslope gradients the spatial patterns of both groundwater and stream discharge change with fluctuating groundwater levels unsaturated sediment s in upslope locations store water infiltrating during wet periods such that groundwater flow from upslope sediments maintains high groundwater levels near the stream and supplies baseflow during dry periods the direction of horizontal groundwater flow in harp 4 21 is not perpendicular to topographic contours so that subcatchment boundaries based on topographic divides differ by as much as 57 from their true subcatchment boundaries based on groundwater divides therefore groundwater flow models based on surface topography may incorrectly predict the spatial pattern of stream discharge

hillslope hydrology and wetland response of two small zero order boreal catchments on the precambrian shield two precambrian shield zero order catchments were monitored from january 2003 to july 2004 to characterize their hydrological and biogeochemical characteristics prior to a forest management experiment hydrometric observations were used to examine temporal trends in hillslope wetland connectivity and the hillslope runoff processes that control wetland event response the hillslope groundwater flux from the longer transect e1 was continuous throughout the study period groundwater fluxes from a shorter and steeper hillslope e0 were intermittent during the study period large depression storage elements termed micro basins located on the upper hillslope of the e1 catchment appeared to be at least partly responsible for the observed rapid wetland runoff responses these micro basins were hydrologically connected to a downslope wetland by a subsurface channel of glacial cobbles that functioned as a macropore channel during episodic runoff events the runoff response from the hilltop micro basins is controlled by antecedent water table position and water is quickly piped to the wetland fringe through the cobble channel during high water table conditions during periods of low water table position seepage along the bedrock soil interface from the hilltop micro basin and other hillslopes maintained hillslope wetland connectivity the micro basins create a dynamic variable source area runoff system where the contributing area expands downslope during episodic runoff events the micro basins occupied 30 of the e1 catchment and are a common feature on the precambrian shield copyright 2007 john wiley sons ltd

scaling and physiographic controls on streamflow behaviour on the precambrian shield south central ontario summary relationships explaining streamflow behaviour in terms of drainage basin physiography greatly assist efforts to extrapolate streamflow metrics from gauged to ungauged basins in the same landscape the dorset environmental science centre desc has monitored streamflow from 22 small basins 3 4 190 5 ha on the precambrian shield in south central ontario in some cases since 1976 the basins exhibit regional coherence in their interannual response to precipitation however there is often a poor correlation between streamflow metrics from basins separated by as little as 1 km this study assesses whether inter basin variations in such metrics can be explained in terms of basin scale and physiography several characteristics annual maximum minimum and average flow exhibited simple scaling with basin area while magnitude range and timing of annual maximum daily runoff showed scaling behaviour consistent with the representative elementary area rea concept this rea behaviour is partly attributed to convergence of fractional coverage of the two dominant and hydrologically contrasting land cover types in the desc region with increasing basin size three principal components pcs explained 82 4 of the variation among basin physiographic properties and several runoff metrics magnitude and timing of annual minimum daily runoff mean number of days per year with 0 streamflow exhibited significant relationships with one or more pc significant relationships were obtained between basin quickflow qf production and the pcs on a seasonal and annual basis almost all of which were superior to simple area based relationships basin physiography influenced qf generation via its control on slope runoff water storage and hydrologic connectivity however this role was minimized during spring when qf production in response to large rain on snow events was relatively uniform across the desc basins the pc based relationships and inter seasonal changes in their form were consistent with previous research conducted at point slope and basin scales in the desc region and perceptions of key hydrological processes in these small basins may not have been as readily obtained from scaling studies using streamflow from larger basins this process understanding provides insights into scaling behaviour beyond those derived from simple scaling and rea analyses the physiography of the study area is representative of large portions of the precambrian shield such that basin streamflow behaviour could potentially be extended across much of south central ontario this would assist predictions of streamflow conditions at ungauged locations development and testing of hydrological models for this landscape and interpretation of inter basin and intra annual differences in hydrochemical behaviour on the southern precambrian shield

the oceanic biogeochemistry of nickel and its isotopes new data from the south atlantic and the southern ocean biogeochemical divide abstract nickel ni is important for a number of enzymes in oceanic phytoplankton it has received less attention than some other bioactive metals because it is not reduced to extremely low dissolved concentrations in the photic zone however there are strong indications in previous studies that this residual pool is not bio available oceanic ni isotope data are still scarce but have great potential for understanding this issue as well as for understanding the ni mass balance of the oceans now and in the past here we present new concentration and isotope data for the uk geotraces section at 40 s in the atlantic ga10 nickel concentration data show typical nutrient like profiles slightly modified by variable pre formed concentrations in sub surface water masses e g north atlantic deep water nickel isotopes in common with findings in previous studies are homogeneous beneath 500 m at about 1 3 in 60 ni in samples with ni concentrations above 3 3 5 nm the surface south atlantic however has concentrations below 3 nm and shows significantly higher 60 ni up to 1 74 that are closely anti correlated with ni concentrations the data for the deep south atlantic dissolved pool with a 60 ni 1 31 0 12 average and 2sd confirm the homogeneity of the global deep ocean which previous data demonstrate extends all the way to the surface in the upwelling zone of the southern ocean south of the polar front this ni isotope composition is significantly heavier than known inputs to the oceanic dissolved pool this mass balance requires an isotopically light sink that may be represented by sedimentary mn oxide associated ni the magnitude of the isotope fractionation implied by the upper ocean data is not consistent with plausible potential abiotic removal processes rather these data are best explained by biological uptake however consideration of the detailed relationships between ni concentrations and isotope compositions requires that a substantial portion of the oceanic dissolved ni pool is not bio available the data are consistent either with a small preference for the light isotope during uptake about 0 1 or two distinct pools of dissolved ni one bio available and one strongly bound in organic complexes with limited isotopic exchange between them patterns of co variation in ni concentrations and isotopes with the major nutrients point to strong contrasts across the polar front of the southern ocean contrasts that exhibit both similarities and differences with those for the major nutrients and other trace metal micronutrients south of the polar front ni is taken up in modest amounts by diatoms without isotope fractionation north of the polar front the data are most consistent with cyanobacteria as the dominant control on ni uptake leading to significant coupled abundance and isotope variation

on the origin of the marine zinc silicon correlation abstract the close linear correlation between the distributions of dissolved zinc zn and silicon si in seawater has puzzled chemical oceanographers since its discovery almost forty years ago due to the apparent lack of a mechanism for coupling these two nutrient elements recent research has shown that such a correlation can be produced in an ocean model without any explicit coupling between zn and si via the export of zn rich biogenic particles in the southern ocean consistent with the observation of elevated zn quotas in southern ocean diatoms here we investigate the physical and biological mechanisms by which southern ocean uptake and export control the large scale marine zn distribution using suites of sensitivity simulations in an ocean general circulation model ogcm and a box model ensemble these simulations focus on the sensitivity of the zn distribution to the stoichiometry of zn uptake relative to phosphate po4 drawing directly on observations in culture our analysis reveals that ogcm model variants that produce a well defined step between relatively constant high zn po4 uptake ratios in the southern ocean and low zn po4 ratios at lower latitudes fare best in reproducing the marine zn si correlation at both the global and the regional southern ocean scale suggesting the presence of distinct zn biogeochemical regimes in the high and low latitude oceans that may relate to differences in physiology ecology or micro nutrient status furthermore a study of the systematics of both the box model and the ogcm reveals that regional southern ocean zn uptake exerts control over the global zn distribution via its modulation of the biogeochemical characteristics of the surface southern ocean specifically model variants with elevated southern ocean zn po4 uptake ratios produce near complete zn depletion in the si poor surface subantarctic zone where upper ocean water masses with key roles in the global oceanic circulation are formed by setting the main preformed covariation trend within the ocean interior the subduction of these zn and si poor water masses produces a close correlation between the zn and si distributions that is barely altered by their differential remineralisation during low latitude cycling we speculate that analogous processes in the high latitude oceans may operate for other trace metal micronutrients as well splitting the ocean into two fundamentally different biogeochemical and thus biogeographic regimes

testing the groundwater ridging hypothesis of streamflow generation during snowmelt in a forested catchment hydrometric and isotopic techniques were used to test the groundwater ridging hypothesis of stream flow generation during snowmelt in a forested catchment on the canadian shield the catchment contains a central wetland that drains to an ephemeral channel hydrograph separation using 2h as a tracer indicated that approximately 60 of total stream flow during snowmelt was supplied by pre event water this was supported by hydrometric results however contrary to the groundwater ridging hypothesis the response of water table levels in near stream areas to initial melt inputs failed to promote a rapid flux of ground water to the wetland and stream all stream flow originated as saturation overland flow from the wetland and groundwater flow during much of the melt was directed down the catchment s main axis and back under hillslopes surrounding the wetland and channel although the hydrograph separation indicated pronounced short term variations in pre event discharge from the catchment groundwater fluxes to the wetland remained relatively invariant following initiation of surface saturation streamflow fluctuations appear to have been generated by displacement of water held in surface storage induced by melt and rainwater inputs to the wetland this stored water had an isotopic signature intermediate between that of event and pre event water suggested oscillations in pre event runoff were an artifact of the mixing model approach to hydrograph separation rather than the result of rapid changes in groundwater fluxes to the wetland

hydrology of a headwater basin wetland groundwater discharge and wetland maintenance the link between groundwater and surface hydrology in a small headwater drainage basin in the zone of glacial deposition of southern ontario south of the precambrian shield was examined for two years the basin is situated in a discharge zone of a regional aquifer and contains a small treed spring fed swamp the swamp exists because of the groundwater and has little effect on the maintenance of streamflow groundwater input to the swamp is an order of magnitude larger than precipitation groundwater of local and regional origin passes through the swamp by two routes surface streamlets where groundwater that emerges at specific seepage points in the swamp is conveyed over the ground surface with little interaction with the swamp itself and by diffuse seepage in the swamp and through the bed of the stream while the diffuse seepage input is the smaller component of groundwater it maintains the swamp s saturation groundwater input to the swamp from the specific seepage points and diffuse flow varies little over a year therefore the saturation of the swamp and baseflow from the basin display little seasonal variation compared to other wetland types the existence of the valley bottom in the headwater basin alters the seasonal and storm hydrology and is important to biogeochemical transformation of emerging groundwater

constraining groundwater discharge in a large watershed integrated isotopic hydraulic and thermal data from the canadian shield or a thin veneer of coarse grained sediments natural conservative d 2 h d 18 o cl and specific conductance radioactive 222 rn and thermal tracers are integrated with streamflow measurements and a steady state advective model to delimit the discharge locations and quantify the discharge fluxes to lakes wetlands creeks and the tay river the groundwater discharge rates to most surface water body types are low indicating that the groundwater and surface water system may be largely decoupled in this watershed compared to watersheds underlain by porous media groundwater discharge is distributed across the watershed rather than localized around lineaments or high density zones of exposed brittle fractures the results improve our understanding of the rate localization and conceptualization of discharge in a large fractured rock watershed applying hydraulic isotopic or chemical hydrograph separation techniques would be difficult because the groundwater discharge signal is small compared to the background surface water inflows or volumes of the surface water bodies although this study focuses on a large watershed underlain by fractured bedrock the methodology developed is transferable to any large regulated or unregulated watershed the low groundwater discharge rates have significant implications for the ecology sustainability and management of large crystalline watersheds

tracing the agulhas leakage with lead isotopes the transport of warm and salty waters from the indian ocean to the south atlantic by the agulhas current constitutes a key return route of the meridional overturning circulation despite the importance of the agulhas leakage on interoceanic exchange its role on biogeochemical cycles is poorly documented here we present the first lead pb concentration and isotope data for surface seawater collected during the geotraces cruise d357 in the agulhas current system lead in surface waters of the cape basin is described by three distinct end members the south african coast open south atlantic seawater and indian ocean seawater the latter stands out in its pb isotopic composition and can be tracked within two distinct agulhas rings high pb concentrations in the agulhas rings further corroborate an indian ocean provenance of waters and suggest that the agulhas leakage represents a major conduit not only for heat but also for trace metals

opal zn si ratios as a nearshore geochemical proxy in coastal antarctica during the last 50 years the antarctic peninsula has experienced rapid warming with associated retreat of 87 of marine and tidewater glacier fronts accelerated glacial retreat and iceberg calving may have a significant impact on the freshwater and nutrient supply to the phytoplankton communities of the highly productive coastal regions however commonly used biogenic carbonate proxies for nutrient and salinity conditions are not preserved in sediments from coastal antarctica here we describe a method for the measurement of zinc to silicon ratios in diatom opal zn si opal which is a potential archive in antarctic marine sediments a core top calibration from the west antarctic peninsula shows zn si opal is a proxy for mixed layer salinity we present down core zn si opal paleosalinity records from two rapidly accumulating sites taken from nearshore environments off the west antarctic peninsula which show an increase in meltwater input in recent decades our records show that the recent melting in this region is unprecedented for over 120 years