28 results found
Morley JD, Myers RJ, Plancherel Y, et al., 2022, A Database for the Stocks and Flows of Sand and Gravel, RESOURCES-BASEL, Vol: 11
Mason AR, Gathorne-Hardy A, White C, et al., 2022, Resource requirements for ecosystem conservation: A combined industrial and natural ecology approach to quantifying natural capital use in nature, ECOLOGY AND EVOLUTION, Vol: 12, ISSN: 2045-7758
Meuriot O, Lique C, Plancherel Y, 2022, Properties, sensitivity, and stability of the Southern Hemisphere salinity minimum layer in the UKESM1 model, CLIMATE DYNAMICS, ISSN: 0930-7575
Morley JD, Myers RJ, Plancherel Y, et al., 2022, A Database for the Extraction, Trade, and Use of Sand and Gravel (Retraction of Vol 11, art no 38, 2022), RESOURCES-BASEL, Vol: 11
Morley JD, Myers RJ, Plancherel Y, et al., 2022, A Database for the Extraction, Trade, and Use of Sand and Gravel, RESOURCES-BASEL, Vol: 11
Conway TM, Horner TJ, Plancherel Y, et al., 2021, A decade of progress in understanding cycles of trace elements and their isotopes in the oceans*, CHEMICAL GEOLOGY, Vol: 580, ISSN: 0009-2541
Rasheed S, Warder SC, Plancherel Y, et al., 2021, An improved gridded bathymetric data set and tidal model for the Maldives Archipelago, Earth and Space Science, Vol: 8, Pages: 1-15, ISSN: 2333-5084
The Maldives faces a unique range of environmental challenges. While the country is almost entirely dependent upon oceanic resources with more than 99% of the area covered by ocean, the absence of a suitable bathymetric map of the seafloor of the Maldives severely limits the adoption and application of modern scientific methods for the prediction of both physical and biological oceanic processes across the country. Here, we present a new bathymetric data set for the country based upon accumulating data from various sources and demonstrate that the synthesis of these provides a far more accurate representation of the shallow water areas of the region than currently available products. We also show that the new bathymetric data set is of sufficiently high resolution to model tidal flows across the archipelago for the first time. The new bathymetric data set provides numerous opportunities to better understand oceanic flow, associated physical and biogeochemical processes, and their correlation to one another across the Maldives archipelago.
Robinson S, Ivanovic R, van de Flierdt T, et al., 2021, Global continental and marine detrital εNd: an updated compilation for use in understanding marine Nd cycling, Chemical Geology, Vol: 567, Pages: 1-20, ISSN: 0009-2541
Understanding the role of sediment-water interactions in the oceanic cycling of neodymium (Nd) isotopes is essential for its reliable use as a modern and palaeoceanographic tracer of ocean circulation. However, the exact processes that control Nd cycling in the ocean are poorly defined and require an up-to-date knowledge of the sources, sinks and transformation of this tracer to and within the ocean (e.g. as per the GEOTRACES core mission). We propose a considerable improvement of Nd-source identification by providing an extensive and up-to-date compilation of published terrestrial and marine sedimentary Nd isotopic measurements. From this database, we construct high resolution, gridded, global maps that characterise the Nd-isotopic signature of the continental margins and seafloor sediment. Here, we present the database, interpolation methods, and final data products. Consistent with the previous studies that inform our compilation, our global results show unradiogenic detrital Nd isotopic values (εNd ≈ -20) in the North Atlantic, εNd values of ≈ -12 to -7 in the Indian and Southern Ocean, and radiogenic values (εNd ≈ -3 to +4) in the Pacific. The new, high-resolution interpolation is useful for improving conceptual knowledge of Nd sources and sinks and enables the application of isotope-enabled ocean models to understand targeted Nd behaviour in the oceans. Such applications may include: examining the strength and distribution of a possible benthic flux required to reconcile global Nd budgets, establishing the potential use of Nd isotopes as a kinematic tracer of ocean circulation, and a general quantification of the non-conservative sedimentary processes that may contribute to marine Nd cycling.
Rasheed S, Warder SC, Plancherel Y, et al., 2021, Response of tidal flow regime and sediment transport in North Male' Atoll, Maldives to coastal modification and sea level rise, Ocean Science, Vol: 17, Pages: 319-334, ISSN: 1812-0784
Changes to coastlines and bathymetry alter tidal dynamics and associated sediment transport processes, impacting upon a number of threats facing coastal regions, including flood risk and erosion. Especially vulnerable are coral atolls such as those that make up the Maldives archipelago, which has undergone significant land reclamation in recent years and decades and is also particularly exposed to sea level rise. Here we develop a tidal model of Malé Atoll, Maldives, the first atoll-scale and multi-atoll-scale high-resolution numerical model of the atolls of the Maldives and use it to assess potential changes to sediment grain size distributions in the deeper atoll basin, under sea level rise and coastline alteration scenarios. The results indicate that the impact of coastline modification over the last two decades at the island scale is not limited to the immediate vicinity of the modified island but can also significantly impact the sediment grain size distribution across the wider atoll basin. Additionally, the degree of change in sediment distribution which can be associated with sea level rise that is projected to occur over relatively long time periods is predicted to occur over far shorter time periods with coastline changes, highlighting the need to better understand, predict and mitigate the impact of land reclamation and other coastal modifications before conducting such activities.
Malik A, Nowack PJ, Haigh JD, et al., 2020, Tropical Pacific climate variability under solar geoengineering: impacts on ENSO extremes, ATMOSPHERIC CHEMISTRY AND PHYSICS, Vol: 20, Pages: 15461-15485, ISSN: 1680-7316
Rodgers KB, Schlunegger S, Slater RD, et al., 2020, Reemergence of anthropogenic carbon into the ocean's mixed layer strongly amplifies transient climate sensitivity, Geophysical Research Letters, Vol: 47, Pages: 1-9, ISSN: 0094-8276
A positive marine chemistry‐climate feedback was originally proposed by Revelle and Suess (1957, https://doi.org/10.3402/tellusa.v9i1.9075), whereby the invasion flux of anthropogenic carbon into the ocean serves to inhibit future marine CO2 uptake through reductions to the buffering capacity of surface seawater. Here we use an ocean circulation‐carbon cycle model to identify an upper limit on the impact of reemergence of anthropogenic carbon into the ocean's mixed layer on the cumulative airborne fraction of CO2 in the atmosphere. We find under an RCP8.5 emissions pathway (with steady circulation) that the cumulative airborne fraction of CO2 has a sevenfold reduction by 2100 when the CO2 buffering capacity of surface seawater is maintained at preindustrial levels. Our results indicate that the effect of reemergence of anthropogenic carbon into the mixed layer on the buffering capacity of CO2 amplifies the transient climate sensitivity of the Earth system.
Stichel T, Kretschmer S, Geibert W, et al., 2020, Particle-seawater interaction of neodymium in the North Atlantic, ACS Earth and Space Chemistry, Vol: 4, Pages: 1700-1717, ISSN: 2472-3452
Dissolved neodymium (Nd) isotopes (expressed as εNd) have been widely used as a water mass tracer in paleoceanography. However, one aspect of the modern biogeochemical cycle of Nd that has been sparsely investigated is the interplay between dissolved and particulate phases in seawater. We here present the first regional data set on particulate Nd isotope compositions (εNdp) and concentrations ([Nd]p) from five stations in the western North Atlantic Ocean along the GEOTRACES GA02 transect, in conjunction with previously published dissolved Nd isotope compositions (εNdd) and concentrations ([Nd]d)1. Key observations and interpretations from our new particulate data set include the following: (1) A low fractional contributions of [Nd]p to the total Nd inventory per volume unit of seawater (~5%), with significant increases of up to 45% in benthic boundary layers. (2) Increasing Nd concentrations in suspended particulate matter ([Nd]SPM) and fractions of lithogenic material with water depth, suggesting the removal of Nd poor phases. (3) Different provenances of particulates in the subpolar and subtropical gyres as evidenced by their Nd isotope fingerprints reaching from εNdp ≈ -20 near the Labrador Basin (old continental crust), over εNdp ≈ -4 between Iceland and Greenland (young mafic provenance), to values of εNdp ≈-13 in the subtropics (similar to African dust signal). (4) Vertical heterogeneity of εNdp, as well as large deviations from ambient seawater values in the subpolar gyre, indicate advection of lithogenic particles in this area. (5) Vertically homogenous εNdp values in the subtropical gyre, indistinguishable from εNdd values, are indicative of predominance of vertical particulate supply. The process of reversible scavenging only seems to influence particulate signatures below 3 km. Overall, we do not find evidence on enhanced particle dissolution, often invoked to explai
Skinner LC, Sadekov A, Brandon M, et al., 2019, Rare Earth Elements in early-diagenetic foraminifer 'coatings': Pore-water controls and potential palaeoceanographic applications, Geochimica et Cosmochimica Acta, Vol: 245, Pages: 118-132, ISSN: 0016-7037
Rare Earth Element (REE) distributions in the ocean bear the fingerprints of several key environmental processes, including vertical particle/organic carbon fluxes, water column/pore-water oxygenation and ocean transports. The use of ‘fossil’ REE analyses in the service of palaeoceanography as redox, water transport or nutrient cycling ‘proxies’ has long been a tantalizing possibility. Here we demonstrate the application of a novel laser-ablation microanalysis approach for the rapid and accurate measurement of the REE composition of early diagenetic ‘coatings’ on fossil foraminifera. By applying this new method to a range of core-top and multi-core samples, we show that ‘authigenic’ REE enrichments on planktonic foraminifer surfaces (REEfs) reflect a primary seawater signature that becomes overprinted during sediment burial due to early diagenetic processes that control the flux of REEs to pore-fluids. Thus ‘light’ REEs (LREEs), and eventually ‘middle’ REEs (MREEs) are generally enriched in foraminifer 'coatings' relative to seawater, while Ce-anomalies (Ce/Ce*) recorded in surface sediments are typically more positive than local seawater values and are further ‘eroded’ during burial with the onset of anoxic conditions in the sediment. Similar patterns have previously been observed in pore-fluid measurements. Indeed, we show that Mn and Fe concentrations measured in foraminifer ‘coatings’ track the availability of these elements in pore-water, indicating that they are not associated with a secondary oxide phase. We propose that these elements, along with REEs are instead adsorbed directly from pore-fluids. In contrast, U in authigenic coatings tracks the removal of this element from solution under sub-oxic conditions, supporting the use of U/Ca in foraminifer coatings as a redox proxy. Although our results confirm a significant early diagenetic influence on REEfs, we also
Lique C, Johnson HL, Plancherel Y, 2018, Correction to: Emergence of deep convection in the Arctic Ocean under a warming climate, Climate Dynamics, Vol: 50, Pages: 3849-3851, ISSN: 0930-7575
Lique C, Johnson HL, Plancherel Y, 2018, Emergence of deep convection in the Arctic Ocean under a warming climate, Climate Dynamics, Vol: 50, Pages: 3833-3847, ISSN: 0930-7575
The appearance of winter deep mixed layers in the Arctic Ocean under a warming climate is investigated with the HiGEM coupled global climate model. In response to a four times increase of atmospheric CO2 levels with respect to present day conditions, the Arctic Basin becomes seasonally ice-free. Its surface becomes consequently warmer and, on average, slightly fresher. Locally, changes in surface salinity can be far larger (up to 4 psu) than the basin-scale average, and of a different sign. The Canadian Basin undergoes a strong freshening, while the Eurasian Basin undergoes strong salinification. These changes are driven by the spin up of the surface circulation, likely resulting from the increased transfer of momentum to the ocean as sea ice cover is reduced. Changes in the surface salinity field also result in a change in stratification, which is strongly enhanced in the Canadian Basin and reduced in the Eurasian Basin. Reduction, or even suppression, of the stratification in the Eurasian Basin produces an environment that is favourable for, and promotes the appearance of, deep convection near the sea ice edge, leading to a significant deepening of winter mixed layers in this region (down to 1000 m). As the Arctic Ocean is transitioning toward a summer ice-free regime, new dynamical ocean processes will appear in the region, with potentially important consequences for the Arctic Ocean itself and for climate, both locally and on larger scales.
Tachikawa K, Arsouze T, Bayon G, et al., 2017, The large-scale evolution of neodymium isotopic composition in the global modern and Holocene ocean revealed from seawater and archive data, Chemical Geology, Vol: 457, Pages: 131-148, ISSN: 0009-2541
Neodymium isotopic compositions (143Nd/144Nd or εNd) 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 εNd database and combined it with hydrography parameters (temperature, salinity, nutrients and oxygen concentrations), carbon isotopic ratio and radiocarbon of dissolved inorganic carbon. Archive εNd 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 εNd and the other variables, suggesting that large-scale water mass mixing is a primary control of deepwater εNd distribution. At ≥ 200 m, basin-scale seawater T-S-εNd diagrams demonstrate the isotopic evolution of different water masses. Seawater and archive εNd values are compared using property-property plots and T-S-εNd 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 εNd 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 εNd is observed mainly within 1000 km from the continents. Generally, seawater and archive εNd 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.
Osborne AH, Hathorne EC, Schijf J, et al., 2017, The potential of sedimentary foraminiferal rare earth element patterns to trace water masses in the past, Geochemistry, Geophysics, Geosystems, Vol: 18, Pages: 1550-1568, ISSN: 1525-2027
Dissolved rare earth element (REE) concentration data from intermediate and deep seawater form an array characterized by higher middle‐REE enrichments (MREE/MREE*) in the North Atlantic and a progressive increase in heavy‐to‐light REE ratios (HREE/LREE) as water masses age. The REEs in foraminifera are fractionated toward higher MREE/MREE* and lower HREE/LREE relative to seawater. Calculations based on a scavenging model show that the REE patterns in uncleaned core‐top foraminifera resemble those adsorbed onto calcite, particulate organic material, and hydrous ferric oxides but the full extent of the REE fractionation measured in foraminifera was not reproduced by the model. However, differences in the HREE/LREE and MREE/MREE* ratios and the cerium anomaly between ocean basins are preserved and are in agreement with the seawater REE distribution. Under oxic conditions, the HREE/LREE and MREE/MREE* compositions of uncleaned foraminifera at the sediment/seawater boundary are preserved during burial but the cerium anomaly is sensitive to burial depth. In suboxic sedimentary environments, all uncleaned foraminiferal REE concentrations are elevated relative to core‐top values indicating addition of REEs from pore waters. The HREE/LREE ratio is highest when sedimentation rates were greatest and when high Fe/Ca ratios in the uncleaned foraminifera indicate that Fe was mobile. In sediments that have not experienced suboxic conditions during burial, uncleaned foraminifera preserve the seawater signal taken up at the sediment/seawater interface and are therefore suggested to be a suitable archive of changes in the REE signal of past bottom waters.
Iudicone D, Rodgers KB, Plancherel Y, et al., 2016, The formation of the ocean's anthropogenic carbon reservoir, Scientific Reports, Vol: 6, ISSN: 2045-2322
The shallow overturning circulation of the oceans transports heat from the tropics to the mid-latitudes. This overturning also influences the uptake and storage of anthropogenic carbon (Cant). We demonstrate this by quantifying the relative importance of ocean thermodynamics, circulation and biogeochemistry in a global biochemistry and circulation model. Almost 2/3 of the Cant ocean uptake enters via gas exchange in waters that are lighter than the base of the ventilated thermocline. However, almost 2/3 of the excess Cant is stored below the thermocline. Our analysis shows that subtropical waters are a dominant component in the formation of subpolar waters and that these water masses essentially form a common Cant reservoir. This new method developed and presented here is intrinsically Lagrangian, as it by construction only considers the velocity or transport of waters across isopycnals. More generally, our approach provides an integral framework for linking ocean thermodynamics with biogeochemistry.
Zheng X-Y, Plancherel Y, Saito MA, et al., 2016, Rare earth elements (REEs) in the tropical South Atlantic and quantitative deconvolution of their non-conservative behavior, GEOCHIMICA ET COSMOCHIMICA ACTA, Vol: 177, Pages: 217-237, ISSN: 0016-7037
Osborne AH, Haley BA, Hathorne EC, et al., 2015, Rare earth element distribution in Caribbean seawater: Continental inputs versus lateral transport of distinct REE compositions in subsurface water masses, MARINE CHEMISTRY, Vol: 177, Pages: 172-183, ISSN: 0304-4203
Lique C, Johnson HL, Plancherel Y, et al., 2015, Ocean change around Greenland under a warming climate, CLIMATE DYNAMICS, Vol: 45, Pages: 1235-1252, ISSN: 0930-7575
Plancherel Y, 2015, Hydrographic biases in global coupled climate models and their relation to the meridional overturning circulation, CLIMATE DYNAMICS, Vol: 44, Pages: 1-44, ISSN: 0930-7575
Plancherel Y, 2014, On the relationships between features of the depth-latitude meridional overturning streamfunctions across global coupled climate models, CLIMATE DYNAMICS, Vol: 42, Pages: 2983-3004, ISSN: 0930-7575
Rodgers KB, Aumont O, Fletcher SEM, et al., 2014, Strong sensitivity of Southern Ocean carbon uptake and nutrient cycling to wind stirring, BIOGEOSCIENCES, Vol: 11, Pages: 4077-4098, ISSN: 1726-4170
Plancherel Y, Rodgers KB, Key RM, et al., 2013, Role of regression model selection and station distribution on the estimation of oceanic anthropogenic carbon change by eMLR, BIOGEOSCIENCES, Vol: 10, Pages: 4801-4831, ISSN: 1726-4170
Lam P, Jensen MM, Kock A, et al., 2011, Origin and fate of the secondary nitrite maximum in the Arabian Sea, BIOGEOSCIENCES, Vol: 8, Pages: 1565-1577, ISSN: 1726-4170
Plancherel Y, Cowen JP, 2007, Towards measuring particle-associated fecal indicator bacteria in tropical streams, WATER RESEARCH, Vol: 41, Pages: 1501-1515, ISSN: 0043-1354
Wang J, Ray K, Brito-Parada P, et al., A Bayesian approach for the modelling of material stocks and flows with incomplete data
Material Flow Analysis (MFA) is used to quantify and understand the lifecycles of materials from production to end of use, which enables environmental,social and economic impacts and interventions. MFA is challenging as availabledata is often limited and uncertain, giving rise to an underdetermined systemwith an infinite number of solutions when attempting to calculate the values ofall stocks and flows in the system. Bayesian statistics is an effective way toaddress these challenges as it rigorously quantifies uncertainty in the dataand propagates it in a system flow model to provide the probabilitiesassociated with model solutions. Furthermore, the Bayesian approach provides anatural way to incorporate useful domain knowledge about the system through theelicitation of the prior distribution. This paper presents a novel Bayesian approach to MFA. We propose a mass basedframework that directly models the flow and change in stock variables in thesystem, including systems with simultaneous presence of stocks anddisaggregation of processes. The proposed approach is demonstrated on a globalaluminium cycle, under a scenario where there is a shortage of data, coupledwith weakly informative priors that only require basic information on flows andchange in stocks. Bayesian model checking helps to identify inconsistencies inthe data, and the posterior distribution is used to identify the variables inthe system with the most uncertainty, which can aid data collection. Wenumerically investigate the properties of our method in simulations, and showthat in limited data settings, the elicitation of an informative prior cangreatly improve the performance of Bayesian methods, including for bothestimation accuracy and uncertainty quantification.
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