probing the melt zone of kilauea iki lava lake kilauea volcano hawaii new drilling techniques were recently used to drill and core the melt zone of kilauea iki lava lake to a depth of 93 m a partial melt zone was found to exist at depths between 58 m and 89 m consisting of 40 volume percent melt downhole seismic shots detonated in and below the melt zone resulted in the first in situ measurements of seismic velocity directly through well characterized partial melt zone periodic seismic sources were used to effectively penetrate the highly fractured hydrothermal zone of the lava lake crust low velocity p wave layers or 2 0 km s were found at the surface at 40 m depth and at 90 m depth thermal convective experiments in the melt zone resulted in the first controlled in situ measurements of the interaction of water with a basaltic melt zone transient energy rates of 900 kw 980 kw m sup 2 and steady rates of 85 kw 93 kw m sup 2 were observed the full water recovery 100 high downhole steam temperatures 670 c and high energy transfer rates 93 to 980 kw m sup 2 observed in these thermal experiments are consistent with a closed cavity model where the injected water steam directly contacted basaltic melt ormore near melt in addition to understanding lava lakes these seismic and thermal experiments have applications for the location of magma bodies in the crust and for the efficient extraction of energy from these bodies less

equatorward pathways of solomon sea water masses and their modifications the solomon sea is a key region of the southwest pacific ocean connecting the thermocline subtropics to the equator via western boundary currents wbcs modifications to water masses are thought to occur in this region because of the significant mixing induced by internal tides eddies and the wbcs despite their potential influence on the equatorial pacific thermocline temperature and salinity and their related impact on the low frequency modulation of el nino southern oscillation modifications to water masses in the solomon sea have never been analyzed to our knowledge a high resolution model incorporating a tidal mixing parameterization was implemented to depict and analyze water mass modifications and the solomon sea pathways to the equator in a lagrangian quantitative framework the main routes from the solomon sea to the equatorial pacific occur through the vitiaz and solomon straits in the thermocline and intermediate layers and mainly originate from the solomon sea south inflow and from the solomon strait itself water mass modifications in the model are characterized by a reduction of the vertical temperature and salinity gradients over the water column the high salinity of upper thermocline water subtropical mode water stmw is eroded and exported toward surface and deeper layers whereas a downward heat transfer occurs over the water column consequently the thermocline water temperature is cooled by 0 15 0 3 c from the solomon sea inflows to the equatorward outflows this temperature modification could weaken the stmw anomalies advected by the subtropical cell and thereby diminish the potential influence of these anomalies on the tropical climate the solomon sea water mass modifications can be partially explained 60 by strong diapycnal mixing in the solomon sea as for stmw about a third of this mixing is due to tidal mixing

exchange of neodymium and its isotopes between seawater and small and large particles in the sargasso sea the concentrations and isotopic ratios of nd were measured in small 1 53 m and large 53 m in situ filtered particles sediment trap material sediment and aerosol samples collected during oligotrophic and productive conditions in the sargasso sea atmospheric input is the main source of exogeneous nd into the sargasso sea based on ndal ratios in trapped material we suggest that up to 50 of atmospheric nd could dissolve at the air sea interface the concentration and isotopic composition of nd vary with both depth and the particle size neodymium concentrations of small and large particles increase with depth from 2 9 12 g g and 5 8 11 8 g g respectively at 40 m the nd signature of large particles is significantly more negative nd 0 13 1 0 2 than that of the small ones nd 0 11 7 0 3 and the particles filtered deeper below 237 m the nd 0 values for small particles match the seawater whereas the nd 0 values of large particles remain less radiogenic these differences are related to the different behaviors of the particulate fractions small particles apparently exchange nd with seawater and then sink rapidly to depth as biologically formed aggregates large particles these aggregates isolate the small particles slowing the exchange with the water to produce different signatures between large particles and seawater since these exchange processes modify the particulate nd signature the shallow radiogenic nd 0 signature observed in the surface and subsurface waters in the nw atlantic is not due to external contributions and is likely of advective origin at depth below 800 m the magnitude of the aggregation disaggregation process varies significantly with season the fraction of small particles repackaged into large aggregates can vary from 0 8 to 80 100 in productive and oligotrophic conditions respectively this seasonal variation may correspond to sinking particles of different zooplanktonic origin vertical fluxes of nd into and out of the sargasso sea as well as exchange fluxes in the water column are examined about 50 of the particulate flux from the surface is remineralized at depth a net scavenging flux of 0 8 10 4 g m2 y is required this value corresponds to a scavenging nd residence time of 1900 y considerably longer than previous estimates of global oceanic residence time of nd on the order of 400 y

rare earth element concentrations and nd isotopes in the southeast pacific ocean 1 three vertical profiles of rare earth element concentrations and nd isotopic compositions have been measured in the remote southeast pacific ocean the three stations represent contrasting environments the oligotrophic center of the gyre station gyr the transition zone east of the south tropical front station egy and the peru chile upwelling marked by a pronounced oxygen minimum station upx rare earth concentrations display nutrient like vertical profiles except at upx where surface waters are enriched at this station nd isotopic compositions are clearly more radiogenic than in the open ocean suggesting that boundary exchange process is releasing lithogenic rare earth element from the volcanic andes unexpected radiogenic values end reaching 3 7 are also observed at 2000 m at station gyr in the upper circumpolar deep water that commonly have end values around 6 exchange processes related to hydrothermal activity are suspected to produce this increase in end in the vicinity of the east pacific rise these results provide some guidance for higher resolution studies planned in this region by the international geotraces program

heat transfer in magma in situ heat transfer rates in a basaltic magma were measured under typical magma chamber conditions and a numerical model of the experiment was used to estimate magma viscosity the results are of value for assessing methods of thermal energy extraction from magma bodies in the upper crust as well as for modeling the evolutionary track of these systems

the large scale evolution of neodymium isotopic composition in the global modern and holocene ocean revealed from seawater and archive data neodymium isotopic compositions 143nd 144nd or end have been used as a tracer of water masses and lithogenic inputs to the ocean to further evaluate the faithfulness of this tracer we have updated a global seawater end database and combined it with hydrography parameters temperature salinity nutrients and oxygen concentrations carbon isotopic ratio and radiocarbon of dissolved inorganic carbon archive end data are also compiled for leachates foraminiferal tests deep sea corals and fish teeth debris from the holocene period 10 000 years at water depths 1500 m property property plots show clear correlations between seawater end and the other variables suggesting that large scale water mass mixing is a primary control of deepwater end distribution at 200 m basin scale seawater t s end diagrams demonstrate the isotopic evolution of different water masses seawater and archive end values are compared using property property plots and t s end diagrams archive values generally agree with corresponding seawater values although they tend to be at the upper limit in the pacific both positive and negative offsets exist in the northern north atlantic applying multiple regression analysis to deep 1500 m seawater data we established empirical equations that predict the main large scale deepwater end trends from hydrography parameters large offsets from the predicted values are interpreted as a sign of significant local regional influence dominant continental influence on seawater and archive end is observed mainly within 1000 km from the continents generally seawater and archive end values form gradual latitudinal trend in the atlantic and pacific at depths 600 m consistent with the idea that nd isotopes help distinguish between northern southern sourced water contributions at intermediate and deep water depths

spatial distribution of dissolved neodymium and end in the bay of bengal role of particulate matter and mixing of water masses abstract the concentration and isotope composition of dissolved nd have been measured in the water column along an 87 e transect gio1 section of international geotraces program in the bay of bengal bob to investigate the effect of water mass mixing and nd release from particulate matter in determining these properties the concentration of nd in surface waters of the bob shows a north south decreasing non linear trend 46 to 22 pmol kg with salinity whereas its depth profiles typically show a high value in surface waters a minimum 15 to 23 pmol kg in the shallow subsurface 50 200 m followed by a gradual increase with depth the nd concentration of bob waters is generally higher than that in nearby oceanic basins on the other hand the e nd values in the bob are less radiogenic compared to those reported for other regions of the global oceans except baffin bay the north atlantic subpolar gyre and the niger delta margin and show a greater variation in the upper water column surface waters of the southernmost profile 6 n show a more radiogenic e nd value 8 which decreases to 15 in the northernmost profile 20 n close to the values for dissolved and particulate phases of the ganga brahmaputra g b rivers this latitudinal trend is most likely a result of variations in mixing proportion between the more radiogenic indonesian throughflow surface waters iw and unradiogenic bob low salinity water the former s signature being more clearly discernible in surface waters of the two southernmost profiles 6 n and 8 5 n attempts to balance the nd budget in the water column based on an inversion model suggest that in addition to water masses other source s is required the strength of which is estimated to vary from 1 to 65 of the measured nd concentration the calculations also show that the e nd of this additional source s has to be in the range of 16 2 typical of g b river sediments these observations coupled with the north south distribution of dissolved nd and e nd indicate that this additional source is release from particulate phases supplied by the g b river system the calculations also bring out the presence of hot spots of nd release excess nd near the sediment water interface along the northern slope of the bay indicating supply of nd from continental margin sediments this study underscores the significant role of dissolved particulate nd from the ganga brahmaputra river system in contributing to the dissolved nd budget of the global oceans

the southwest pacific ocean circulation and climate experiment spice the southwest pacific ocean circulation and climate experiment spice is an international research program under the auspices of clivar the key objectives are to understand the southwest pacific ocean circulation and the south pacific convergence zone spcz dynamics as well as their influence on regional and basin scale climate patterns south pacific thermocline waters are transported in the westward flowing south equatorial current sec toward australia and papua new guinea on its way the sec encounters the numerous islands and straits of the southwest pacific and forms boundary currents and jets that eventually redistribute water to the equator and high latitudes the transit in the coral solomon and tasman seas is of great importance to the climate system because changes in either the temperature or the amount of water arriving at the equator have the capability to modulate the el nino southern oscillation while the southward transports influence the climate and biodiversity in the tasman sea after 7 years of substantial in situ oceanic observational and modeling efforts our understanding of the region has much improved we have a refined description of the spcz behavior boundary currents pathways and water mass transformation including the previously undocumented solomon sea the transports are large and vary substantially in a counter intuitive way with asymmetries and gating effects that depend on time scales this paper provides a review of recent advancements and discusses our current knowledge gaps and important emerging research directions

the origin of the pacific equatorial 13 c water abstract examination of the vertical distributions of temperature salinity oxygen and nutrient salts in the thermostad of the equatorial 13 c water in the eastern pacific ocean indicates that local vertical mixing is unimportant in creating the thermostad and the characteristics of the 13 c water maps are presented that show the oceanwide distributions of depth geostrophic flow salinity oxygen phosphate silica and nitrate on the 160 cl t 1 isanosteric surface which nearly coincides with the core of the 13 c water the maps suggest that the original characteristics of the 13 c water are acquired in the surface and thermocline layers to the northeast of new zealand and in the tasman sea by winter convection and vertical mixing the acquired characteristics are advected to the thermostad in the eastern pacific via a long route starting from the source region the flow is first eastward in high latitudes and then returns westward in low latitudes around the anticyclonic subtropical gyre of the sout

western pacific coastal sources of iron manganese and aluminum to the equatorial undercurrent 1 we present results from the first zonal transect of iron aluminum and manganese conducted from the western source region of the equatorial undercurrent euc to the central equatorial pacific trace metals were elevated along the slope of papua new guinea and within the new guinea coastal undercurrent ngcu which is the primary southern hemisphere entry path of water to the euc subsurface maxima in total acid soluble iron aluminum and manganese were evident in the euc these maxima were generally greatest in the western equatorial pacific and decreased in magnitude eastward maxima in iron and aluminum persisted to 140 w maxima in manganese extended to 175 w iron and manganese maxima were deeper 25 75 m than aluminum maxima and located in the lower euc which undergoes less interior ocean mixing than shallower waters the depth of the aluminum subsurface maxima correlated strongly r 0 88 with the depth of the euc velocity maximum surface waters were enriched in aluminum and manganese offshore of papua new guinea surface metal concentrations decreased eastward throughout the western warm pool up to the longitude 180 w of the salinity front detrital sediment input from either direct riverine input or sediment resuspension appeared to be the primary mechanism of supplying metals to the ngcu we estimated eastward fluxes of metals in the euc and found greatest fluxes in the western equatorial pacific between 160 e and 165 e except for aluminum fluxes of aluminum and to a lesser extent manganese increased concurrently with water volume transport in the central equatorial pacific iron transport in the euc remained constant east of the dateline apparently due to the combined effects of dilution by meridional entrainment and scavenging iron was mobilized in a highly active western boundary current region and transported eastward in the lower euc

heat transfer measurements of the 1983 kilauea lava flow convective heat flow measurements of a basaltic lava flow were made during the 1983 eruption of kilauea volcano in hawaii eight field measurements of induced natural convection were made giving heat flux values that ranged from 1 78 to 8 09 kilowatts per square meter at lava temperatures of 1088 and 1128 degrees celsius respectively these field measurements of convective heat flux at subliquidus temperatures agree with previous laboratory measurements in furnace melted samples of molten lava and are useful for predicting heat transfer in magma bodies and for estimating heat extraction rates for magma energy

oceanic transports through the solomon sea the bend of the new guinea coastal undercurrent 1 thermocline waters of the tropical southwest pacific can be traced back to the center of the south pacific basin and have a potential influence on equatorial surface conditions and on the characteristics of the el nino southern oscillation on decadal timescales the solomon sea is traversed by this influential flow and therefore is an optimal place for exploring this oceanic connection to the equator from a high resolution hydrographic survey at which we applied an inverse box model we describe the main pathways at the entrance of the solomon sea and more particularly the extremely sharp bend of the western boundary current around the south east tip of papua new guinea of the 30 sv subtropical waters transported into the coral sea from the east above 1300 m 29 5 sv makes its way through the solomon sea with a large part transported in a boundary current at the entrance of the solomon sea around the south east tip of papua new guinea the gulf of papua current turns abruptly to the north in a very sharp bend as it merges into the new guinea coastal undercurrent on its way toward the equator the warm currents transport large amounts of internal energy with a total of 1 0 0 3 1015w entering the solomon sea from the south

rare earth element input and transport in the near surface zonal current system of the tropical western pacific abstract continental sources and current transport play a major role in rare earth element ree and other trace element input and distribution in the tropical western pacific here we present spatially highly resolved distributions of dissolved ree concentrations ree along three transects in the zonal extra equatorial current system and the solomon strait of the tropical western pacific we use seawater ree in combination with direct physical oceanographic observations e g current velocity data to characterize the geochemical composition origin and pathways of the complex surface and upper layer currents of the tropical western pacific and to quantify the input fluxes of rees we identify papua new guinea png volcanic rocks sediments and or river particles as the key source adding trace elements to the equatorial eastward zonal currents of the tropical western pacific our and published data indicate temporal and spatial variability of this input and transport in the png source area and the equatorial eastward currents the westward currents on the other hand lack this ree input signal suggesting lateral transport of preformed seawater ree at the transition between these zonal eastward and westward currents our data indicate lateral mixing of eastern and western pacific source waters

magma flow and interaction with waste packages in a geologic repository at yucca mountain nevada abstract the likelihood that a nuclear waste repository at yucca mountain could be intersected by igneous activity is very low but its potential consequences are nevertheless important to performance assessments an ongoing critical area of concern is the nature and magnitude of the thermal interaction of magma with tunnel walls high level nuclear waste packages and waste forms previous assessments consider a variety of dynamic scenarios but large uncertainties remain in understanding the rheological nature of the magma likely to be involved and its behavior within a repository drift here we specifically address the issue of magma rheology during degassing cooling and solidification as basaltic magma approaches earth s surface and enters a drift magma containing significant amounts 2 wt of dissolved water wet magma as is anticipated for this region at or near its liquidus temperature and saturated with water at 200 mpa is at a temperature near or below the 1 atm solidus temperature isentropic ascent from this near liquidus temperature promotes extensive solidification and or glassification exsolving water with approach to the surface promotes rapid vesiculation leading to fragmentation and tephra production with continued ascent the still water saturated magma traverses the solidification phase field and undergoes a combination of rapid crystallization and quenching becoming a glassy highly viscous 108 pa s mass of greatly reduced mobility this immobility is reflected in the high effective viscosity regulating flows from nearby cinder cones associated with wet basalt this also matches well with the experimentally determined rheology of dry basalt glass this rheology greatly restricts the mobility of basalt within repository drifts amounting to

convective heat extraction from molten magma the convective heat of molten magma in the upper 10 km of the continental crust represents a significant geothermal energy resource shallow basaltic magmas 10 km near the liquidus 1250 c are predicted to offer heat extraction rates in the range of 15 50 kw m2 20 80 mw well more accessible andesitic and wet rhyolitic magmas are predicted to offer heat extraction rates in the range of 5 25 kw m2 8 40 mw well convective heat transfer correlations are used which include corrections for high prandtl number fluids and cylindrical boundary layers the calculations based on these correlations agree well with laboratory tests using molten basalt at superliquidus temperatures 1450 1650 c at liquidus and subliquidus temperatures an additional correction is developed for the thick solidified crust that forms on the heat exchanger non newtonian rheology is considered and shown to have a possible effect on the initiation of convection in the liquidus and subliquidus temperature range in addition to heat extraction estimates the analysis presented here is also relevant to convective heat loss to walls of magma bodies

convective transport in crustal magma bodies abstract convective transport in enclosures is reviewed as it relates to magma bodies convective effects are discussed that are peculiar to the rheological character of magma the large prandtl number of magma delays onset of turbulence and causes velocity disturbances to extend far beyond the thermal boundary layer and well into the fluid core a boundary layer analysis is used to show that convective transport in enclosed magma bodies produces an upward heat flux which can lead to migration of magma by upmelting multicellular convection is discussed and shown to produce upflow at the walls in cases where extensive cooling occurs at the top of the magma chamber multicellular convection can lead to bimodal magma systems and can also produce vertical zonation and layering examples of oscillatory convective circulation are given and this phenomena is discussed as a possible mechanism for eruptive cycles and for vertical zonation in magma chambers non newtonian rheology is also examined as it applies to convection in magma

from the subtropics to the equator in the southwest pacific continental material fluxes quantified using neodymium data along modeled thermocline water pathways the southwestern tropical pacific part of a major pathway for waters feeding the equatorial undercurrent is a region of important geochemical enrichment through land ocean boundary exchange here we develop an original method based on the coupling between dynamical modeling and geochemical tracer data to identify regions of enrichment along the water pathways from the subtropics to the equator and to allow a refined quantification of continental material fluxes neodymium data are interpreted with the help of modeled lagrangian trajectories of an ocean general circulation model we reveal that upper and lower thermocline waters have different pathways together with different geochemical evolutions the upper thermocline waters entering the solomon sea mainly originate from the central subtropical gyre enter the coral sea in the north vanuatu jet and likely receive radiogenic neodymium from the basaltic island margins encountered along their route the lower thermocline waters entering the solomon sea mainly originate from northeast of new zealand and enter the coral sea in the north caledonian jet depletion of their neodymium content likely occurs when flowing along the australian and papua coasts downstream from the solomon sea waters flowing along the papua new guinea margins near the sepik river mouth become surprisingly depleted in their neodymium content in the upper thermocline while enriched in the lower thermocline this coupled approach is proposed as strong support to interpret the origin of the equatorial pacific natural fertilization through a better understanding of the circulation important objectives of the international geotraces and spice programs respectively

the subtropical mode waters of the south pacific ocean abstract the subtropical mode waters stmw of the southwestern pacific ocean are described including their physical characteristics spatial distribution and temporal variability stmw is a thermostad or minimum in stratification having temperatures of about 15 19 c and vertical temperature gradient less than about 2 c per 100 m typical salinity is 35 5 psu at 16 5 c the stmw layer is formed by deep mixing and cooling in the eastward flowing waters of the separated east australia current surface mixed layers are observed as deep as 300 m north of new zealand in winter in the center of a recurring anticyclonic eddy the stmw thermostad in the south pacific is considerably weaker than its counterparts in the north atlantic and north pacific a contrast that may help to discriminate between physical processes contributing to its formation a quarterly time series of expendable bathythermograph transects between new zealand and fiji is used to study the temporal variability of stmw large fluctuatio

from the subtropics to the central equatorial pacific ocean neodymium isotopic composition and rare earth element concentration variations 1 neodymium isotopic compositions end and rare earth element ree concentrations were measured for filtered surface to deep waters 112 samples in the southern tropical pacific the relatively detailed picture of these tracer distributions allowed us to refine the areas where oceanic end variations occur end values increase for most of the water masses flowing from samoa to the solomon sea and in the papua new guinea png area as already observed furthermore water masses arriving from the eastern equatorial pacific 200 550 m depth also revealed radiogenic values possibly acquired in the vicinity of the south american coasts and galapagos islands these end variations affect the whole water column the most likely process causing such variations is boundary exchange between the numerous radiogenic slopes margins located in this area and seawater flowing past dissolution of atmospheric deposition and or diffuse streaming of volcanic ash are also suggested to explain the radiogenic end observed at the surface in the png area interestingly a positive europium eu anomaly characterizes the normalized ree patterns of most of the studied water masses this anomaly is consistent with the ree patterns of sediment and rock samples that are potential sources for the local waters such consistency reinforces the hypothesis that lithogenic sources play a major role in the oceanic ree budget thanks to boundary exchange the data set presented here is a good basis for further sampling that will be realized in the framework of the ongoing geotraces program www geotraces org

contrasting holocene sedimentary geologies of lower daly river northern australia and lower sepik ramu papua new guinea abstract the estuarine plain of the macrotidal daly river in monsoonal northern australia is underlain by extensive mid holocene mangrove swamp sediments which accumulated during the last stages of post glacial sea level rise sediment yield from the catchment is too low to account for the volume which accumulated during sea level rise and onshore transport is invoked this is supported by radiocarbon ages and facies analysis of the transgressive sediment tract beneath the maximum flooding surface mfs and of the tract of vertical sedimentation which extends from the mfs to the surface of estuarine fluvial transition the eft the eft occurred about 5000 to 6000 bp throughout the estuarine plain a contrasting situation exists in the lowland holocene basin of the microtidal sepik and ramu rivers in papua new guinea which derive sediment from highly tectonic catchments a tectonic basin which was a shallow brackish inland sea after post glacial transgression is separated by a low divide from a deltaic plain progradation of the deltaic plain commenced about 3500 bp after regressive sedimentation eclipsed the inland sea in the tectonic basin contrasting organic facies mangrove in the daly and freshwater swamp deposits in the sepik ramu highlight differences between facies models of the two systems differences between fluvio tidal regimes are reflected by the eft which is synchronous in the daly and diachronous in the sepik ramu and possibly by the mfs which is diachronous in the daly and may be synchronous in the sepik ramu

volcano surveillance using infrared cameras abstract volcanic eruptions are commonly preceded accompanied and followed by variations of a number of detectable geophysical and geochemical manifestations many remote sensing techniques have been applied to tracking anomalies and eruptive precursors and monitoring ongoing volcanic eruptions offering obvious advantages over in situ techniques especially during hazardous activity whilst spaceborne instruments provide a distinct advantage for collecting data remotely in this regard they still cannot match the spatial detail or time resolution achievable using portable imagers on the ground or aircraft hand held infrared camera technology has advanced significantly over the last decade resulting in a proliferation of commercially available instruments such that volcano observatories are increasingly implementing them in monitoring efforts improved thermal surveillance of active volcanoes has not only enhanced hazard assessment but it has contributed substantially to understanding a variety of volcanic processes drawing on over a decade of operational volcano surveillance in italy we provide here a critical review of the application of infrared thermal cameras to volcano monitoring following a summary of key physical principles instrument capabilities and the practicalities and methods of data collection we discuss the types of information that can be retrieved from thermal imagery and what they have contributed to hazard assessment and risk management and to physical volcanology with continued developments in thermal imager technology and lower instrument costs there will be increasing opportunity to gather valuable observations of volcanoes it is thus timely to review the state of the art and we hope thereby to stimulate further research and innovation in this area

rare earth elements and yttrium in seawater icp ms determinations in the east caroline coral sea and south fiji basins of the western south pacific ocean abstract using inductively coupled plasma mass spectrometry icp ms vertical profiles of yttrium and all the rare earth elements rees in seawater were obtained at three locations in the western south pacific the east caroline coral sea and south fiji basins based on the data we have analyzed the inter ree iii relationships and found that ree iii s heavier than dy and particularly close neighbors show strong coherencies in their oceanic behavior considering that the heavy ree iii s are less particle reactive than the light and middle ree iii s and that they have very tight correlations with regressions passing almost through the origin the neighboring element ratios of the heavy ree iii s behave virtually conservatively and are suitable as tracers of water masses the dy ho er system is practically good because its dynamic range signal to noise ratio is large in the ocean the highest ho dy ratios 0 31 are found in intermediate and deep waters throughout the western south pacific which overlie the antarctic bottom water with a low ho dy ratio 0 27 these high ho dy waters are probably formed in the polar and subantarctic frontal zone and advect northward ree iii data provide better insights into the deep water recirculation in the south pacific than those discussed based upon the regular oceanographic properties alone

interannual variability of the subsurface high salinity tongue south of the equator at 165 e abstract a 14 yr time series of salinity at thermocline level was constructed from repeated meridional ctd sections averaging about 110 days apart spanning the equator along 165 e during 1984 97 a tongue of high salinity water extends along the isopycnal t 24 5 from its surface outcrop in the southeast pacific to 175 m depth near 5 10 s along the section at 165 e in the west the tongue moves vertically with the thermocline mostly as part of the enso cycle while salinity in the tongue varied interannually over a range of 0 4 psu most of this variability was due to zonal advection along the isopycnal tongue with similar changes observed at other longitudes in the west and central pacific part of the interannual salinity signal can be attributed to changes in the near zonal flow of the south equatorial current associated with el nino but a general 0 3 psu rise occurring during the 1990s probably starting even earlier was not apparently consistent with this explanation an attempt was made to

tracing papua new guinea imprint on the central equatorial pacific ocean using neodymium isotopic compositions and rare earth element patterns abstract the nd isotopic composition ic and rare earth patterns of hydrodynamic structures of the equatorial pacific ocean were characterized along 140 w the nd ic of antarctic intermediate water aaiw and of the lower layer of the equatorial undercurrent euc at 140 w 13 c water are much more radiogenic at the equator than at their origin in the south equatorial current 12 s revealing that these water masses have been in contact with the highly radiogenic papua new guinea png slope in both cases only a small fraction less than 9 of the sediment deposited on the png slope is required to be exchanged or dissolved to explain these nd ic variations whereas the hydrographic properties of the same water masses remain unchanged this confirms the usefulness of this tracer to identify pathways of water masses these results emphasize the importance of jets in transporting lithogenic material into the subsurface layers of remote areas where aeolian inputs are particularly weak and corroborate the previous results on fe and al maximum in this area m l wells g k vallis e a silver nature 398 1999 601 604 the nd ic of the upper layer of the euc contrasts strongly to that of the subpycnocline layer indicating that the equatorial upwelling only affects the surface waters and is not effective between 120 and 150 m we calculate that the nd imprint of the png input is likely to vanish from this surface layer as it traverses the basin due to the replacement of upwelled waters by non radiogenic ones

dissolved rare earth elements distribution in the solomon sea abstract trace elements and isotopes teis were measured as part of the geotraces pandora cruise july august 2012 r v l atalante among them rare earth elements rees as pertinent tracers of land ocean inputs and water mass transformations this work discusses results of 19 dissolved ree dree profiles measured using a trispike method in the coral sea and inside and at the exits of the solomon sea a semi enclosed sea with complex topography and straits overall drees except the insoluble ce show nutrient like profiles i e depleted at the surface and enriched at depth illustrative nd concentrations range from 5 pmol kg at the surface to 25 pmol kg at 5000 m depth however local dree enrichments are observed mostly in the straits indispensable solomon and vitiaz straits and along the island coasts a box model allows calculating and discussing the fate of the drees in the different water layers flowing through the solomon sea finally subtle variations revealed by la ce eu anomalies and the normalized light versus heavy ree ratio expressed as ndn ybn allows the identification of specific mechanisms affecting the distribution of the different drees the positive eu anomaly observed in the surface layers reflects the basaltic origin of external inputs consistent with the intensive weathering and or volcanic activity affecting the surrounding islands these data also confirm that the distributions of heavy drees like yb are better correlated to the dsi concentrations than that of the other rees 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

iron isotopes in the seawater of the equatorial pacific ocean new constraints for the oceanic iron cycle abstract this study presents the isotopic compositions and concentrations of dissolved and particulate iron from two seawater profiles of the western and central equatorial pacific ocean sampled during the eucfe cruise most of the 56 fe values are positive relative to irmm 14 from 0 01 to 0 58 in the dissolved fraction dfe and from 0 02 to 0 46 in the particulate fraction pfe the mean measurement uncertainty of 0 08 2sd allows the observation of significant variations most of the isotope variations occur in the vertical and not in the horizontal direction implying that each isotope signature is preserved over long distances within a water mass the thermocline waters of the papua new guinea png area mostly influenced by sedimentary inputs display a mean 56 dfe value of 0 37 0 15 2sd this isotopic signature suggests that the process releasing dissolved iron into the seawater in this area is a non reductive dissolution of sediments discharged by local rivers and likely re suspended by strong boundary currents rather than dissimilatory iron reduction dir within the sediment characterized by negative 56 dfe these positive 56 dfe values seem to be the result of a mean isotopic fractionation of 56 fe dfe pfe 0 20 0 11 2sd produced by the non reductive dissolution at 0 n 180 e the fe isotope signature of the equatorial undercurrent euc waters is identical to that of the png station within the range of the uncertainty this suggests that the dissolved iron feeding the euc and ultimately the eastern pacific high nutrient low chlorophyll area is of png origin likely released by a non reductive dissolution of terrigenous sediments significant fe removals are observed within the thermocline and the intermediate waters between the png and the open ocean stations the corresponding isotopic fractionations appear to be small with 56 fe removed sw fe values of 0 30 0 31 to 0 18 0 12 2sd for dfe removal and of 0 10 0 04 to 0 05 0 31 2sd for pfe removal in the chlorophyll maximum of the open ocean station the isotopic fractionation associated with biological uptake is estimated at 56 fe phyto dfe 0 25 0 10 to 0 13 0 11 2sd although these fractionations are based on a limited dataset and need to be further constrained they appear to be small and to limit the transformations of the iron source signatures within the ocean

interpreting d seismic structure using synthetic waveforms computed from dynamic models we have formulated dynamic models of processes hypothesized to give rise to observed seismological structure at the base of the mantle one dimensional seismic models are determined from thermo chemical convection calculations from which synthetic waveforms are computed of the three scenarios studied 1 a thermal slab 2 a thermal slab interacting with simple chemical layer and 3 a thermal slab interacting with a phase transition the strength of seismic phases computed from 3 best correlates with the global geography of the observed d triplication seismic structures predicted by 1 or 2 are inconsistent with the global geography and strength of the triplication our successful model motivates a new class of 1 d seismic models with two mild gradients and a small discontinuity to test this hypothesis we searched for seismic models that both contain these features and fit d seismic observations our preferred model contains a gentle positive gradient initiated 350 km above the cmb and a 1 jump in s velocity near 200 km a strong negative gradient begins about 100 km above the cmb similar to previous studies representing the lower thermal boundary layer with the reduced first order discontinuity the p wave triplication becomes too small to observe and provides a simple explanation for the observed weakness of the p in proportion to the s triplication

the influence of trench migration on slab penetration into the lower mantle abstract a two dimensional numerical convection model in cartesian geometry is used to study the influence of trench migration on the ability of subducted slabs to penetrate an endothermic phase boundary at 660 km depth the transient subduction history of an oceanic plate is modelled by imposing plate and trench motion at the surface the viscosity depends on temperature and depth a variety of styles of slab behaviour is found depending predominantly on the trench velocity when trench retreat is faster than 2 4 cm a the descending slab flattens above the phase boundary at slower rates it penetrates straight into the lower mantle although flattening in the transition zone may occur later leading to a complex slab morphology the slab can buckle independent of whether it penetrates or not especially when there is a localised increase in viscosity at the phase boundary flattened slabs are only temporarily arrested in the transition zone and sink ultimately into the lower mantle the results offer a framework for understanding the variety in slab geometry revealed by seismic tomography

origin and pathway of equatorial 13 c water in the pacific identified by a simulated passive tracer and its adjoint abstract the origin and pathway of the thermostad water in the eastern equatorial pacific ocean often referred to as the equatorial 13 c water are investigated using a simulated passive tracer and its adjoint based on circulation estimates of a global general circulation model results demonstrate that the source region of the 13 c water lies well outside the tropics in the south pacific some 13 c water is formed northeast of new zealand confirming an earlier hypothesis on the water s origin the south pacific origin of the 13 c water is also related to the formation of the eastern subtropical mode water estmw and the sub antarctic mode water samw the portion of the estmw and samw that eventually enters the density range of the 13 c water 25 8 26 6 kg m 3 does so largely by mixing water formed in the subtropics enters the equatorial region predominantly through the western boundary while its interior transport is relatively small the fresher north pacific estmw and central mode wate

the geochemical balance of the rare earth elements and neodymium isotopes in the oceans profiles of ree concentrations and neodymium isotope measurements in the western indian ocean are consistent with published data from the other major oceans ree concentrations show a strong hydrographic control the influence of intermediate water masses is particularly significant surface water concentrations vary with salinity paniculate rees are less than 5 of dissolved concentration except for ce where up to 20 of total rees are present as 0 4 m particles in contrast to dissolved profiles concentration profiles of paniculate rees including ce all increase with depth ree concentrations correlate with silica over all but the deepest waters although in detail correlations are complex the neodymium isotopic composition of indian ocean seawater avg nd 0 8 3 is intermediate between that for the atlantic and pacific oceans comparison of ree data from the major oceans shows that the hrees behave more like si than do the lrees sm nd ratios are near constant for all oceans whereas ernd ratios vary between the atlantic indian and pacific oceans the fractionation of the rees in surface seawaters can be explained by fractionation factors relative to silica from 0 12 for la to 0 05 for er use of a seven box model shows that the interoceanic variations in neodymium isotopic compositions and nd concentrations cannot be reconciled unless particle water exchange is invoked the degree of exchange required is consistent with particle residence times of 1 10 yr

western pacific modulation of large phytoplankton blooms in the central and eastern equatorial pacific 1 satellite observations show that large scale phytoplankton blooms increases in chlorophyll occurred in the equatorial pacific in 1998 2003 and 2005 following termination of the three most recent el nino events the occurrence of blooms following successive el nino events cannot be explained by local enhancement of vertical nutrient flux as evidenced by observations of equatorial winds thermocline depth and the depth and strength of the equatorial undercurrent euc which supplies the limiting nutrient iron to the euphotic zone however near the peak of each el nino event late in 1997 2002 and 2004 while the thermocline of the western equatorial pacific was anomalously shallow the flow of the new guinea coastal undercurrent ngcuc which is the primary source of iron enriched waters to the euc intensified and its core shoaled from 200 m to 100 m depth analysis of ngcuc variability using a high resolution terrain following three dimensional ocean circulation model simulation indicates that as the ngcuc shoals and intensifies it develops meanders and eddies that augment coupling of the new guinea shelf and upper slope to the euc we hypothesize that these changes in ngcuc circulation during el nino enhance iron transport from the new guinea margin into the euc and thereby trigger large scale blooms when iron enriched waters subsequently reach the euphotic zone along the equator the threefold to fourfold chlorophyll increases over large regions up to 5 105 km2 must have profound impacts on the equatorial ecosystem and biogeochemical cycles

iron sources and dissolved particulate interactions in the seawater of the western equatorial pacific iron isotope perspectives this work presents iron isotope data in the western equatorial pacific marine aerosols and top core margin sediments display a slightly heavy fe isotopic composition 56 fe of 0 33 0 11 2sd and 0 14 0 07 respectively samples reflecting the influence of papua new guinea runoff sepik river and rabaul volcano water are characterized by crustal values in seawater fe is mainly supplied in the particulate form and is found with a 56 fe between a0 49 and 0 34 0 07 the particulate fe seems to be brought mainly by runoff and transported across continental shelves and slopes aerosols are suspected to enrich the surface vitiaz strait waters while hydrothermal activity likely enriched new ireland waters dissolved fe isotopic ratios are found between a0 03 and 0 53 0 07 they are almost systematically heavier than the corresponding particulate fe and the difference between the signature of both phases is similar for most samples with 56 fe dfe pfe 0 27 0 25 2sd this is interpreted as an equilibrium isotopic fractionation revealing exchange fluxes between both phases the dissolved phase being heavier than the particles suggests that the exchanges result in a net nonreductive release of dissolved fe this process seems to be locally significantly more intense than fe reductive dissolution documented along reducing margins it may therefore constitute a very significant iron source to the ocean thereby influencing the actual estimation of the iron residence time and sinks the underlying processes could also apply to other elements

kinematics of the pacific equatorial undercurrent an eulerian and lagrangian approach from gcm results abstract three dimensional monthly velocity fields from an ocean general circulation model are used to study the annual mean mass balance of the pacific equatorial undercurrent euc eulerian diagnostics are used to evaluate the various meridional vertical and zonal mass fluxes related to the euc there are several distinct regimes along the equator showing clear asymmetries between the western and eastern parts of the basin and between the northern and southern edges of the euc meridional fluxes are decomposed into pure ekman divergence and geostrophic convergence and it is shown that the asymmetries are mainly related to the spatial structure of the ekman divergence and thus to that of the trade winds lagrangian calculations are used to evaluate accurately the mass transfers between various sections of the euc and between the euc domain and the tropics the authors show that geostrophic convergence only ventilates the upper layers of the euc and that the euc really is a tongue of water flowing

sources and processes affecting the distribution of dissolved nd isotopes and concentrations in the west pacific abstract in the atlantic where deep circulation is vigorous the dissolved neodymium nd isotopic composition expressed as nd is largely controlled by water mass mixing in contrast the factors influencing the nd distribution in the pacific marked by sluggish circulation is not clear yet indication for regional overprints in the pacific is given based on its bordering volcanic islands our study aims to clarify the impact and relative importance of different nd sources rivers volcanic islands vertical bio geochemical processes and lateral water mass transport in controlling dissolved nd and nd concentration nd distributions in the west pacific between south korea and fiji we find indication for unradiogenic continental input from south korean and chinese rivers to the east china sea in the tropical west pacific volcanic islands supply nd to surface and subsurface waters and modify their nd to radiogenic values of up to 0 7 these radiogenic signatures allow detailed tracing of currents flowing to the east and differentiation from westward currents with open ocean pacific nd composition in the complex tropical pacific zonal current system modified radiogenic nd of west pacific intermediate to bottom waters upstream or within our section also indicates non conservative behavior of nd due to boundary exchange at volcanic island margins submarine ridges and with hydrothermal particles only subsurface to deep waters 3000 m in the open northwest pacific show conservative behavior of nd in contrast we find a striking correlation of extremely low down to 2 77 pmol kg nd and laterally constant nd with the high salinity north and south pacific tropical water indicating lateral transport of preformed nd from the north and south pacific subtropical gyres into the study area this observation also explains the previously observed low subsurface nd in the tropical west pacific similarly western south pacific central water antarctic intermediate water and lower circumpolar deep water in the southern and equatorial west pacific are marked by vertically and laterally almost invariant nd indicating a dominance of conservative behavior of nd in contrast central and intermediate water in the north west pacific are characterized by increasing nd with depth reflecting nd release from particles overall our data demonstrate a dominant lateral transport control on nd distributions and clear non conservative modification of nd in the west pacific the latter affords tracing of surface and subsurface zonal transport in the tropical pacific but prevents the use of nd as strictly conservative tracer of the major meridionally circulating water masses in the west pacific between 15 s and 28 n

fingerprinting northeast atlantic water masses using neodymium isotopes dissolved neodymium nd isotopic composition expressed as end has been analysed for 82 seawater samples collected from 13 stations stretching from the alboran sea to the iceland basin the distribution of the end values of water masses was thus investigated for the first time along the western european margin in order to explore whether the water masses flowing in the eastern subpolar and subtropical atlantic reveal distinct isotopic patterns the modified atlantic water maw in the alboran sea displays end values between 9 2 0 2 and 8 9 0 2 that are significantly more radiogenic than those reported in previous studies 10 8 0 2 to 9 7 0 2 suggesting temporal variations in the nd isotopic composition of the water that enters the mediterranean sea from the strait of gibraltar the end value of the underlying modified winter intermediate water wiw has been established for the first time 9 8 0 3 and is compatible with a nd signature acquired from the sinking of maw in the northwestern mediterranean sea within the gulf of cadiz southern mediterranean sea water msw 10 6 0 2 differs slightly from the northern msw 9 9 0 4 owing to a significant contribution of modified east antarctic intermediate water eaaiw 10 9 0 2 in the northeast atlantic the north atlantic current surface water located in the inter gyre region north of 46 n displays end values of between 14 0 0 3 and 15 1 0 3 reflecting the subpolar gyre signature along the western european margin end values of surface water decrease toward the north from 10 4 1 6 to 13 7 1 0 in agreement with the gradual mixing between subtropical and subpolar water at intermediate depth end values decrease from 9 9 0 4 within the gulf of cadiz to 12 1 0 3 within the porcupine seabight indicating a strong dilution of the msw with subpolar water within the rockall trough and the iceland basin the more negative end values at mid depth 13 5 0 3 indicate that the msw has no influence even during periods of low nao index water masses deeper than 1200 m in the northeast atlantic are clearly influenced by the less radiogenic labrador sea water lsw 13 2 0 3 and 14 5 0 3 that mixes locally end between 10 3 0 2 and 11 3 0 3 in the iceland basin with the iceland scotland overflow water isow

late winter generation of spiciness on subducted isopycnals the origins of density compensating anomalies of temperature and salinity spice are investigated using a model forced with the most realistic surface products available over the 40 years 1958 97 in this hindcast the largest interannual spiciness anomalies are found in the pacific ocean near the isopycnal s 0 5 25 5 where deviations as great as 1 28c and 0 6 psu are generated equatorward of winter outcropping in the eastern subtropics in both hemispheres these source regions are characterized by very unstable salinity gradients and low mean density stratification in winter two related signatures of winter mixing in the southeast pacific sep are density that is well mixed deeper than either temperature or salinity and subsurface density ratios that approach 1 all ocean basins in the model are shown to have regions with these characteristics and signatures however the resultant spiciness signals are focused on different isopycnals ranging from s 0 5 25 0 in the northeast pacific to s 0 5 26 5 in the south indian ocean a detailed examination of the sep finds that large positive anomalies are generated by diapycnal mixing across subducted isopycnals e g s 0 5 25 5 whereas negative anomalies are the result of a steady isopycnal advection moderated by vertical advection and heave there is considerable interannual variability in the strength of anomalies and in the density on which they occur historical observations are consistent with the model results but are insufficient to verify all aspects of the hindcast including the processes of anomaly generation in the sep it was not possible to relate isopycnal anomaly genesis to local surface forcing of any kind a complex scenario involving basinwide circulation of both the ocean and atmosphere especially of surface water through the subtropical evaporation zones is put forward to explain the decadal time scale evident in sep salinity anomalies on s 0 5 25 5 pacific anomalies generated on s 0 5 25 5 can be traced along mean geostrophic streamlines to the western boundary where decadal salinity variations at 78s are about 2 times as large order 60 1 psu as at 128n although there may be more variance on shallower isopycnals in the north at least portions of the s 0 5 25 5 signals appear to continue along the boundary to a convergence at the equator suggesting that the most robust sources of pacific spiciness variance coincide with equatorial exchange pathways

observed characteristics and vertical structure of mesoscale eddies in the southwest tropical pacific in the southwest pacific ocean waters transit from the subtropical gyre before being redistributed equatorward and poleward while the mean pathways are known the contribution to the mixing and transport of the water from mesoscale eddies has not been comprehensively investigated in this research satellite altimetry data combined with an eddy detection and tracking algorithm is used to investigate the distribution and surface characteristics of mesoscale eddies in this region of complex bathymetry 10 s 30 s 140 e 190 e detected eddies are then colocalized with in situ data from argo floats to determine their vertical structure and the effect of eddies on the water masses the numerous islands affect the eddy behavior as most eddies are formed in the lee of islands propagate westward and decay when encountering shallow bathymetry eddies are sparse and short lived in the tropical area north of fiji impacting only the top 200 meters of water they do not appear to be able to trap and transport waters in this region in the coral sea a region of lateral shear between currents transporting waters of different origins eddies are more numerous and energetic they affect the water properties down to at least 500 m depth and anticyclonic eddies trap water to 200 m contributing to the upper thermocline waters mixing and transport south of new caledonia mesoscale eddies are ubiquitous with typical lifetimes longer than 5 months they affect the temperature salinity and velocities down to 1 000 m depth and weakly contribute to the mixing of lower thermocline waters

rare earth element transport in the western north atlantic inferred from nd isotopic observations the isotopic composition of nd in the water column from several western north atlantic sites and formational areas for north atlantic deep water shows extensive vertical structure at all locations in regions where a thermocline is well developed large isotopic shifts 2 to 3 units are observed across the base of the thermocline regions without a thermocline are characterized by much more gradual shifts in isotopic composition with depth in general the data reveal an excellent correlation between the nd isotopic distribution in the western north atlantic water column and the distribution of water masses identified from temperature and salinity characteristics nadw as identified from t s properties is also characterized by a well defined isotopic composition having nd 0 13 5 0 5 this signature is associated with waters identified as nadw from high latitudes near formational areas in the labrador sea down to the equatorial region the isotopic signature of nadw would appear to be formed by a blend of more negative waters originating in the labrador sea nd 0 18 and more positive waters originating in the overflows from the norwegian and greenland seas nd 0 8 to 10 and is consistent with classical theories on the formation of nadw the isotopic signature of nadw is propagated southward to the equator where it is gradually being thinned out by mixing from above and below with more radiogenic nd associated with northward spreading antarctic intermediate and bottom waters the preservation of the isotopic signature of nadw over these large distances indicate that the ree undergo extensive lateral transport the isotopic composition of nd is largely conservative over the time scales of mixing within the atlantic in spite of the intrinsic nonconservative behavior of neodymium nd concentration gradients generally show surface waters to be depleted in nd relative to deep waters which must require vertical transport processes however isotopic differences in the water column preclude the local downward transport of ree from the surface into underlying deep waters as a simple explanation of the concentration gradient the apparent decoupling of ree in nadw from overlying local surface waters and the increasing concentration with depth provide a conflict with simple vertical transport mechanisms that is not yet resolved