Earth and Space Science Open Archive This work was has been accepted for publication in Journal of Geophysical Research - Biogeosciences. Version of RecordESSOAr is a venue for early communication or feedback before peer review. Data may be preliminary. Learn more about preprints. preprintOpen AccessYou are viewing an older version [v2]Go to new versionLeaf Wax Hydrogen Isotopes as a Hydroclimate Proxy in the Tropical PacificAuthors Sarah Nemiah Ladd iD Ashley Elizabeth Maloney iD Daniel Nelson iD Matthew Prebble iD Giorgia Camperio iD David Ayres Sear iD Jonathan Hassall Peter Langdon Julian P Sachs iD Nathalie Dubois iDSee all authors Sarah Nemiah LaddiDCorresponding Author• Submitting AuthorEawagiDhttps://orcid.org/0000-0002-0132-5785view email addressThe email was not providedcopy email addressAshley Elizabeth MaloneyiDPrinceton UniversityiDhttps://orcid.org/0000-0003-3079-6073view email addressThe email was not providedcopy email addressDaniel NelsoniDUniversity of BaseliDhttps://orcid.org/0000-0002-2716-7770view email addressThe email was not providedcopy email addressMatthew PrebbleiDUniversity of CanterburyiDhttps://orcid.org/0000-0001-8577-7190view email addressThe email was not providedcopy email addressGiorgia CamperioiDEawagiDhttps://orcid.org/0000-0001-7704-0041view email addressThe email was not providedcopy email addressDavid Ayres SeariDUniversity of SouthamptoniDhttps://orcid.org/0000-0003-0191-6179view email addressThe email was not providedcopy email addressJonathan HassallUniversity of Southamptonview email addressThe email was not providedcopy email addressPeter LangdonUniversity of Southamptonview email addressThe email was not providedcopy email addressJulian P SachsiDUniversity of WashingtoniDhttps://orcid.org/0000-0002-6247-9286view email addressThe email was not providedcopy email addressNathalie DuboisiDEawagiDhttps://orcid.org/0000-0003-2349-0826view email addressThe email was not providedcopy email address
Significant uncertainties persist in the reconstruction of past sea surface temperatures in the eastern equatorial Pacific, especially regarding the amplitude of the glacial cooling and the details of the post‐glacial warming. Here we present the first regional calibration of alkenone unsaturation in surface sediments versus mean annual sea surface temperatures (maSST). Based on 81 new and 48 previously published data points, it is shown that open ocean samples conform to established global regressions of U 37 K′ versus maSST and that there is no systematic bias from seasonality in the production or export of alkenones, or from surface ocean nutrient concentrations or salinity. The flattening of the regression at the highest maSSTs is found to be statistically insignificant. For the near‐coastal Peru upwelling zone between 11–15°S and 76–79°W, however, we corroborate earlier observations that U 37 K′ SST estimates significantly over‐estimate maSSTs at many sites. We posit that this is caused either by uncertainties in the determination of maSSTs in this highly dynamic environment, or by biasing of the alkenone paleothermometer toward El Niño events as postulated by Rein et al. (2005).
Abstract. Leaf wax n-alkanes are increasingly used for quantitative paleoenvironmental reconstructions. However, this is complicated in sediment archives with associated hydrological catchments since the stored n-alkanes can have different ages and origins. 14C dating of the n-alkanes yields independent age information for these proxies, allowing their correct paleoenvironmental interpretation. This also holds true for fluvial sediment–paleosol sequences (FSPSs) that integrate two different n-alkane signals: (i) a catchment signal in fluvial sediments and (ii) an on-site signal from local biomass that increasingly dominates (paleo)soils with time. Therefore, the age and origin of n-alkanes in FSPSs are complex: in fluvial sediment layers they can be pre-aged and reworked when originating from eroded catchment soils or from organic-rich sediment rocks in the catchment. In (paleo)soils, besides an inherited contribution from the catchment, they were formed on-site by local biomass during pedogenesis. Depending on the different relative contributions from these sources, the n-alkane signal from an FSPS shows variable age offsets between its formation and final deposition. During this study, we applied compound-class 14C dating to n-alkanes from an FSPS along the upper Alazani in eastern Georgia. Our results show that preheating the n-alkanes with 120 ∘C for 8 h before 14C dating effectively removed the shorter chains (<C25) that partly originate from n-alkanes from Jurassic black clay shales in the upper catchment. The remaining petrogenic contributions on the longer chains (≥C25) were corrected for by using a constant correction factor that was based on the n-alkane concentrations in a black clay shale sample from the upper catchment. Due to different degrees of pre-aging and reworking, the corrected leaf wax n-alkane ages still indicate relatively large age offsets between n-alkane formation and deposition: while intensively developed (paleo)soils showed no age offsets due to a dominance of leaf wax n-alkanes produced on-site, less intensively developed paleosols showed much larger age offsets due to larger proportions of inherited leaf wax n-alkanes from the fluvial parent material. Accordingly, age offsets in nonpedogenic fluvial sediments were largest and strongly increased after ∼4 ka cal BP. The leaf wax n-alkane homolog distribution from intensively developed (paleo)soils indicates a local dominance of grasses and herbs throughout the Holocene, which was most likely caused by anthropogenic activity. The leaf wax n-alkanes from fluvial sediments show a dominance of deciduous trees and shrubs as well as grasses and herbs in different parts of the catchment between ∼8 and ∼5.6 ka cal BP. Since no older deciduous tree- or shrub-derived n-alkanes were dated, this seems to confirm a delayed regional postglacial reforestation of parts of the catchment compared with western and central Europe.
The Radiocarbon Inventories of Switzerland (RICH) project aims to construct the first national-scale census of (radio)carbon across aquatic, terrestrial, and atmospheric reservoirs. Within the carbon cycle, inland waters play a crucial role with lakes integrating carbon from various sources within their catchments in addition to that fixed by local primary productivity. Here we will present radiocarbon measurements of water-column dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and particulate organic carbon (POC) from 15 lakes across Switzerland covering a range of sizes, elevations, and trophic states. In addition, a year of monthly water column measurements from Switzerland’s two largest lakes - Lake Constance and Lake Geneva - reveal seasonal trends resulting from changes in productivity and river inflow. Preliminary results show that the average radiocarbon signature of DIC in both Lake Constance and Lake Geneva is depleted in 14C relative to atmospheric CO2, indicating a ca. 15-20% contribution from bedrock weathering (14C-dead carbon). The timeseries at Lake Constance builds on earlier measurements which have shown a decline in DI14C since the late 1960s due to decreasing concentrations of bomb radiocarbon in the atmosphere. DO14C values in Lake Constance are more enriched compared to DI14C, indicating the importance of terrestrial DOC sources. In contrast, DO14C values in Lake Geneva are similar to DI14C, consistent with lake primary productivity as the main source of DOC. Overall, variations in radiocarbon values between different lakes are much greater than seasonal variations observed in either Lake Constance or Lake Geneva. These results form the basis of a radiocarbon inventory of Swiss lakes and provide new insights into carbon cycling in these dynamic aquatic systems.
Abstract Industrial activities of a silk dyeing factory in Thalwil, on the shore of Lake Zurich, Switzerland, caused extreme Sn contamination of lake sediments. In this study, we determine the contamination source, spread, and age using a multiproxy approach. We used X-ray fluorescence spectroscopy (XRF) core scanning and further geochemical analyses to assess the contamination spreading and thickness in the sedimentary column. We found elevated Sn levels throughout sediments of Lake Zurich, ranging from 177 $$\hbox {g} \,\hbox {kg}^{-1}$$ gkg-1 in front of the former silk factory to 0.05 $$\hbox {g} \,\hbox {kg}^{-1}$$ gkg-1 at the southeast end (background: ca. 0.006 $$\hbox {g}\, \hbox {kg}^{-1}$$ gkg-1 ). The rapid concentration drop away from the shore suggests quick precipitation of a sparingly soluble inorganic Sn compound, which is confirmed by Scanning Electron Microscope Imaging in tandem with Energy-dispersive XRF spectroscopy (SEM-EDX) data. The Sn XRF profile of a varved core indicates a contamination onset in the early 1890s, a maximum around 1900, and a gradual decrease to low levels in the 1940s. High Sn concentrations in turbidite layers from the deep basin indicate that mass movements physically remobilised Sn. However, in stable conditions, in-situ porewater measurements (conc. < 0.5 $$\upmu \hbox {g}\, \hbox {L}^{-1}$$ μgL-1 ) using dialyse plates show little Sn remobilisation into the lake water (0.05 $$\hbox {mg} \,\hbox {a}^{-1} \,\hbox {m}^{-2}$$ mga-1m-2 ). The low remobilisation, reducing conditions, and high sulphide contents in the contaminated layers suggest that Sn is firmly bound to the sediments. Combined with the low toxicity of Sn, we conclude that the Sn contamination poses no threat to lake biota or drinking water production.
This roadmap is the product of a grassroots effort by the Swiss Geosciences community. It is the first of its kind, outlining an integrated approach to research facilities for the Swiss Geosciences. It spans the planning period 2025-2028. Swiss Geoscience is by its nature leading or highly in-volved in research on many of the major national and global challenges facing society such as climate change and meteorological extreme events, environmental pol-lution, mass movements (land- and rock-slides), earth-quakes and seismic hazards, global volcanic hazards, and energy and other natural resources. It is essential to under- stand the fundamentals of the whole Earth system to pro-vide scientific guidelines to politicians, stakeholders and society for these pressing issues. Here, we strive to gain efficiency and synergies through an integrative approach to the Earth sciences. The research activities of indivi- dual branches in geosciences were merged under the roof of the 'Integrated Swiss Geosciences'. The goal is to facilitate multidisciplinary synergies and to bundle efforts for large research infrastructural (RI) requirements, which will re-sult in better use of resources by merging sectorial acti- vities under four pillars. These pillars represent the four key RIs to be developed in a synergistic way to improve our understanding of whole-system processes and me- chanisms governing the geospheres and the interactions among their components. At the same time, the roadmap provides for the required transition to an infrastructure adhering to FAIR (findable, accessible, interoperable, and reusable) data principles by 2028.The geosciences as a whole do not primarily profit from a single large-scale research infrastructure investment, but they see their highest scientific potential for ground-break-ing new findings in joining forces in establishing state-of-the-art RI by bringing together diverse expertise for the benefit of the entire geosciences community. Hence, the recommendation of the geoscientific community to policy makers is to establish an integrative RI to support the ne- cessary breadth of geosciences in their endeavor to ad-dress the Earth system across the breadth of both temporal and spatial scales. It is also imperative to include suffi-cient and adequately qualified personnel in all large RIs. This is best achieved by fostering centers of excellence in atmospheric, environmental, surface processes, and deep Earth projects, under the roof of the 'Integrated Swiss Geosciences'. This will provide support to Swiss geo-sciences to maintain their long standing and internatio- nally well-recognized tradition of observation, monitor-ing, modelling and understanding of geosciences process-es in mountainous environments such as the Alps and beyond.
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