G02_P01

Radiocarbon geochemistry of amino acids in marine sediments

Blattmann T^1,2,  Ishikawa N², Keil R³, Yokoyama Y⁴, Ogawa N², Haghipour N^1,5, Sun Y^2,4,6, Neibauer J³, Duffy M³, Suga H², Miyairi Y⁴, Eglinton T¹, Takano Y², Ohkouchi N²

¹ETH Zurich, Zurich, Switzerland, ²Biogeochemistry Research Center, JAMSTEC, Yokosuka, Japan, ³School of Oceanography, Seattle, USA, ⁴Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Japan, ⁵Laboratory of Ion Beam Physics, ETH Zurich, Zurich, Switzerland, ⁶Department of Earth and Planetary Science, The University of Tokyo, Tokyo, Japan

The “building blocks of life” occur ubiquitously on Earth’s surface in the form of proteins, peptides, and single amino acids. To shed light on amino acid sources, cycling, and preservation, we have conducted amino acid-specific radiocarbon analysis on surficial marine sediment from the North American west coast. As the main goal for these investigations, we test a hypothesis that amino acid-specific radiocarbon signatures reflect the interactions of organic matter with mineral surfaces on a molecular level. This hypothesis was inspired by laboratory-based sorption experiments showing strong differences in the partitioning of different amino acids between dissolved and clay mineral adsorbed states (Blattmann & Ishikawa, 2020). We employed high-performance liquid chromatography described in Blattmann et al. (2020) to isolate individual amino acids extracted from marine sediment which were vetted for their purity via chromatography and elemental composition. Isolated amino acids were measured on accelerator mass spectrometers as gas and graphite samples at ETH Zurich and the University of Tokyo, respectively. Amino acids showed multiple centuries age difference demonstrating differential turnover within this compound class in marine surface sediments. The results highlight the role of clay minerals in modulating the preservation of amino acids in the sedimentary record.

References:

Blattmann, T.M. & Ishikawa, N.F. (2020) Theoretical amino acid-specific radiocarbon content in the environment: Hypotheses to be tested and opportunities to be taken. Frontiers in Marine Science 7.

Blattmann, T.M. et al. (2020) Liquid chromatographic isolation of individual amino acids extracted from sediments for radiocarbon analysis. Frontiers in Marine Science 7.

G02_P02

Ensuring comparability of radiocarbon measurements in dissolved inorganic carbon of seawater between ETH-Zurich and NOSAMS

Castrillejo M^1,2,  Hansman R³, Wacker L², Lester J¹, Graven H¹

¹Department of Physics, Imperial College London, London, United Kingdom, ²Laboratory of Ion Beam Physics, ETH-Zurich, Zurich, Switzerland, ³Woods Hole Oceanographic Institution - National Ocean Sciences Accelerator Mass Spectrometry Facility, Woods Hole, USA

Radiocarbon observations provide useful information about carbon cycling and ocean circulation of the real ocean and of model simulations. In an effort to provide high-quality radiocarbon observations, the Laboratory of Ion Beam Physics (LIP) developed the ETH-LIP analytical method allowing the rapid and precise analysis of radiocarbon in small seawater samples. The performance of this method is continuously assessed by following several internal quality controls. Yet, further steps have been taken to ensure the comparability of the data produced at ETH to previously existing observations.

In the absence of standards or reference materials of seawater, comparability can be assessed through inter-laboratory comparisons. To that end, an inter-comparison exercise was conducted in 2021 between ETH and the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) Facility at Woods Hole Oceanographic Institution. In February 2020, duplicate seawater samples were collected from 14 depths and geographical locations distributed along the GO-SHIP A05 line in the subtropical North Atlantic (~ 24.5° N). This work presents the results reported from the two laboratories, which overall showed a very good agreement. We further discuss important aspects related to the different sample collection, preservations and storage techniques used to collect the seawater for NOSAMS and ETH.

G02_P03

AMS ¹⁴C dating and stable isotope analysis on an 8-kyr oyster shell from Taipei Basin: Sea level and SST changes

Chou C¹,  Kang S¹, Liu T¹, Li H¹

¹Department Of Geosciences, NTU, Taipei, Taiwan

A giant oyster shell ( 42 cm long), Crassostrea gigas, was uncovered from an oyster reef on the ancient shore of eastern Taipei Basin in 2002. The oyster reef was 14.9 m below the ground surface which has an elevation of 10 m a.s.l. Eight AMS ¹⁴C dates along the growth axis of the shell are from 8130±200 yr BP to 8435±155 yr BP, indicating that the shell was formed and deposited about 8300 years ago during the high sea level stand of middle Holocene. A plancenta shell collected 5 m above the oyster reef shows a ¹⁴C age of 7640±60 yr BP, indicating that Taipei Basin was covered by ocean water during 7640±60 ~ 8435±155 yr BP. A total of 79 stable isotope samples were collected in a 5.5-cm section from the oldest part of the shell, giving δ¹⁸O range of -6.03‰ ~ -1.33‰ and δ¹³C range of -2.21‰ ~ -0.31‰ (VPDB). These δ¹⁸O and δ¹³C profiles show clear seasonal cycles, indicating a 4-year growth in the 5.5-cm section. Both δ¹⁸O and δ¹³C values illustrate that the oyster grew in a saline environment. Compared with the δ¹⁸O profiles of modern oyster shells in Taiwan, the ancient oyster grew in a much warmer shoreline water environment. According to the studying section, the oyster reef had an elevation of 0 m at 8300 yr BP, and the Plancenta shell had 3-5 m a.s.l. at 7600 yr BP.

Key words: Taipei Basin, early-Mid Holocene, oyster shell, ¹⁴C dating, stable isotopes

G02_P04

Tracking the ¹⁴C bomb peak recorded in Arctica Islandica across the North Sea and Northeast Atlantic Ocean

Christiane Y¹, Christl M¹,  Witbaard R², Wacker L¹, Hattendorf B³, Welte C^1,4, Synal H¹

¹ETH Zurich, Laboratory of Ion Beam Physics, Zurich, Switzerland, ²Royal Netherlands Institute for Sea Research, Texel,, , ³ETH Zurich, Trace Element and Microanalysis, Zurich, Switzerland, ⁴ETH Zurich, Biogeosciences, Zurich, Switzerland

Spatially resolved radiocarbon profiles were recorded using Laser Ablation AMS (LA-AMS) from six Arctica Islandica shells collected at different locations in the North Sea and Northern Norway. The profiles were combined with independently derived chronologies from counting the growth bands of the bivalves to reconstruct spatial and temporal differences in the marine ¹⁴C bomb pulse. Shells were sampled from a range of water depths, i.e., 15 to 150 m, with growth rates varying between 3 and <0.1 mm/yr. For ¹⁴C sampling, the shells were moved under the laser with a speed of 10-25 μm/s with an integration time of 10 s. The recorded ¹⁴C profiles were further integrated to reduce noise and scatter of the data resulting in a final sampling resolution between 1 and 10 yrs. Comparison of the LA-AMS derived data with graphite measurements from earlier studies was very good.

The ¹⁴C bomb peak was identified in all samples, but with different timing and amplitude compared to the modeled marine mixed layer (MMML) calibration curve. The maximum of the ¹⁴C signal in the shells correlates inversely with water depth, while the delay of the peak increases with greater water depth. Both observations consistently indicate a dampening of the atmospheric signal with water depth due to the increased influence of Atlantic deep waters. The presented profiles show the potential of LA-AMS to map the spatiotemporal variation of the marine bomb pulse, providing valuable information on local deviations from the MMML and constraining simulations of the marine bomb peak.

G02_P05

Radiocarbon in the ocean: ensuring high quality results

Hansman R¹,  Key R², McNichol A¹, Sonnerup R³

¹Woods Hole Oceanographic Institution, Woods Hole, United States, ²Princeton University, Princeton, United States, ³University of Washington, Seattle, United States

Repeat open ocean radiocarbon measurements of dissolved inorganic carbon (DIC) have led to a better understanding of key ocean processes such as mixing, ventilation rates, air-sea gas exchange, and ocean biogeochemistry.  Until recently, only a few laboratories had the ability to make the precise ¹⁴C analyses necessary to document ocean circulation and the oceanic uptake of anthropogenic CO₂, but technological advances have reduced sample size requirements, brought new methods online, and made it easier for more laboratories to collect and analyze DI¹⁴C in the ocean.  However, as there are presently no recognized standards or reference materials for radiocarbon in seawater, it is critical to ensure the quality and data comparability of these measurements across laboratories and over time.  To this end, a three-day virtual workshop sponsored by the Ocean Carbon & Biogeochemistry program was held in November 2021 to discuss best practices for the measurement, data handling, and reporting of carbon isotopes in the ocean.  While the workshop included the analysis of both DI¹³C and DI¹⁴C, an immediate need for an inter-laboratory comparison exercise of radiocarbon in seawater DIC was determined.  We will present a summary of the workshop discussion and outcomes, including imminent plans for this DI¹⁴C inter-comparison, as well as work towards establishing reference materials for the community.

G02_P06

Long Term Time Series of Surface Water Dissolved Inorganic Carbon Isotopes from the Southern California Bight

Hauksson N¹,  Griffin S¹, Xu X¹, Martinez H¹, Pedron S¹, Druffel E¹

¹University Of California, Irvine, Irvine, United States

The Southern California Bight is an oceanographically complex region in a Mediterranean climate, strong upwelling, and limited rainfall. The health of kelp forests and marine protected areas in these waters depend on the balance of waters from wind-driven upwelling, the California current, and the California counter-current. Water mass tracers, such as carbon isotopes, inform the movement of water masses in this region. We report dissolved inorganic carbon (DIC) ∆¹⁴C and 𝛅¹³C values in seawater collected from the Newport Beach Pier in Orange County, California from 2011 to 2022. The ∆¹⁴C values decrease over this period, consistent with depletion of the ¹⁴C generated by thermonuclear weapons testing and dilution of ¹⁴C-free CO₂ from fossil fuel combustion. We analyze the relationship of these isotopes with the environmental conditions during this time series.

G02_P07

The chronology of the sedimentation in the Danube abyssal fan records the major episodes of the late-Holocene Black Sea evolution

Ilie M^1,2,  Sava T¹, Vespremeanu-Stroe A³, Duliu O², Cristea G⁴, Ion G⁵, Olteanu D^1,3, Haliuc A⁶, Manailescu C¹, Sava G¹

¹RoAMS Laboratory, Horia Hulubei National Institute For R&D In Physics And Nuclear Engineering (IFIN-HH), Magurele, Ilfov, Romania, ²University of Bucharest, Faculty of Physics, Magurele, Romania, ³GEODAR Research Center for Geomorphology, Geoarchaeology and Paleo-environments, Faculty of Geography, University of Bucharest, Bucharest, Romania, ⁴Department of Mass Spectrometry, Chromatography and Applied Physics, National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca, Romania, ⁵National Institute of Marine Geology and Geo-Ecology (GeoEcoMar), Bucharest, Romania, ⁶Romanian Academy, Institute of Speleology, Cluj-Napoca, Romania

The construction for the high-resolution Bayesian sedimentation model spanning the last 5500 years based on 25 AMS radiocarbon dated sediments of bulk organic matter (OM) sampled from the NW Black Sea anoxic waters of the continental slope is presented in this paperwork. The corrections for the ¹⁴C ages due to marine reservoir effect (MRE) and detritus organic carbon are correlated with exogenous information such as 210Pb dating, metallurgy pollution and human-induced soil erosion, highlighting the Danube influence on the geochemistry and chronology of the NW Black Sea sediments through the input of terrigenous organic matter.

The results show excellent agreement with some of the previous studies, supporting a total age offset for the bulk OM of 60 years as MRE and 580 years as detritus organic carbon influence. The revisited chronology pinpoints the first and second invasion of the coccolitho-phores Emiliania huxleyi at 2524 ± 87 and 625 ± 65 years cal. BP. The sedimentation rate shows an increase of about three times with the starting of the late Medieval, which corresponds to the highest observed sediment discharge of the Danube as are considered the last 500-300 years.

This type of high-resolution sedimentation model is an important step for constructing the carbon budget in bottom waters of variable oxygen concentration.

G02_P08

Organic carbon cycling in the deep ocean: Implications from radiocarbon

Kim M^1,2,3,  Hwang J², Haghipour N^3,4, Eglinton T³

¹Kyungpook National University, Daegu, South Korea, ²School of Earth and Environmental Sciences/Research Institute of Oceanography, Seoul National University, Seoul, South Korea, ³Geological Institute, Swiss Federal Institute of Technology in Zürich (ETHZ), Zurich, Switzerland, ⁴Laboratory of Ion Beam Physics, ETH Zürich, Zurich, Switzerland

The transport of carbon from surface waters to the deep ocean via primary production and subsequent export of POC, known as the biological carbon pump, is a crucial process for sequestration of atmospheric CO₂. Large-scale sediment trap studies have advanced our understanding of material fluxes during vertical transit from surface to deep waters. However, despite the potential importance in the oceanic carbon cycle, the global feature of lateral supply of aged organic matter hosted on lithogenic particles derived from sediment resuspension has not been systematically examined.

Here I summarize the results of previous studies that have insights on the lateral transport of aged organic matter: Amundsen Sea, East/Japan Sea, deep abyssal Pacific, and the Northwest Atlantic. Especially in Kim et al. (2020), we compiled concentrations and fluxes of lithogenic material in the ocean on a global-scale by using literature data of sediment trap studies to understand the contribution of resuspended sediment to sinking particulate matter. Examination of Δ¹⁴C values of sinking POC revealed strong relationships with parameters that represent contribution of resuspended sediment. We then derive estimates for the contribution of aged POC from sediment resuspension to sinking POC based on these relationships and global lithogenic material flux data. Based on this relationship, and the global mean of lithogenic content of sinking particulate matter, we calculate that aged POC from sediment resuspension comprises 3~5 % of sinking POC intercepted by sediment traps.

G02_P09

Tracing bomb radiocarbon in sinking particulate organic carbon in the deep Sargasso Sea

Schnepper C¹,  Pedrosa-Pamies R², Conte M², Gruber N¹, Haghipour N¹, Eglinton T¹

¹Geological Institute, ETH , Zürich, Switzerland, ² Marine Biological Laboratory, WHOI, Woods Hole, USA

The imprint of bomb radiocarbon on sinking particulate organic carbon (PO¹⁴C) intercepted by sediment traps, together with flux and compositional data, provides information about the origin and dynamics of oceanic particles (Hwang et al., 2010). Of particular interest is the question of whether the intercepted POC in the deep ocean stems from overlying primary production, i.e., as part of the “extrinsic“ biological pump, or whether the POC additionally originates from advection and subsequent aggregation of resuspended sedimentary carbon originating from continental margins and other far-away sources (“intrinsic” flux). Measurements by Kim et al. (2020) revealed significant variability in PO¹⁴C, however the processes driving this variability remain poorly understood. To quantify the intra- and inter-annual variability in PO¹⁴C, an in-depth study was initiated at the Ocean Flux Program site in the Sargasso Sea. This sediment trap time-series has generated (bi-)weekly samples and resulting information on particle fluxes and flux compositions at three water depths (500, 1500, 3200 m) since 1978. Preliminary data reveal intra-annual variations in PO¹⁴C with an amplitude of ca. 100 ‰. Seasonal Δ¹⁴C variations are paralleled by shifts in the POC/Lithogenic ratio. This supports the notion that POC with high Δ¹⁴C values, high POC/Lithogenic ratio and POC flux reflects supply of particles that originate via the “extrinsic“ biological pump, while lower Δ¹⁴C values and POC/Lithogenic ratios may reflect the “intrinsic” flux including resuspended sediments with higher lithogenic content emanating from continental margins. A nascent global PO¹⁴C database will allow to assess the broader relevance of our findings.

G02_P10

Age offsets between marine-derived lipid biomarkers, TOC, and foraminifera during cross shelf-slope lateral transport revealed by compound-specific radiocarbon dating

UCHIDA M¹,   Eglinton T², Coppola L³, Gustafsson Ö⁴, Mollenhauer G⁵, Hayes J^6,8, Ahagon N⁷, Harada N⁷

¹Earth System Division, National Institute For Environmental Studies, Tsukuba, Japan, ²Geological Institute, ETH, Zurich, Switzerland, ³Villefranche-sur-mer, Alpes Maritimes, France, ⁴Institute of Applied Environmental Research, Stockholm University, Stockholm, Sweden, ⁵Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany, ⁶National Ocean Sciences Accelerator Mass Spectrometry facility, Woods Hole Oceanographic Institution, Woods Hole, U.S.A., ⁷Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan, ⁸Deceased 3 February 2017, ,

Compound-specific radiocarbon analysis was performed on bulk sediments and different grain-size fractions (>250μm, 150-250μm, 63-150μm,38-63μm, <38μm) of shelf-slope surface sediments (0-2cm, outer shelf of 150m water depth and upper slope of 600m water depth) from Washington Margin to examine their relationships between hydrodynamic sorting of sediments and timescales and preservation of organic carbon. Here we obtained datasets of radiocarbon ages of alkenone, low molecular weight fatty acids (LMW-FAs, C₁₄, C₁₆, and C₁₈), high molecular weight fatty acids (HMW-FAs, C₂₄, C₂₆, and C₂₈), total organic carbon and planktic foraminifera. These results were also discussed with previous reported lateral transport times of organic carbon (Bao et al., 2019). Age offsets between planktonic foraminifera, LMW-FAs, and alkenone in bulk phase sediments were significantly large in shelf compared with slope. On the other hand, age offsets between size fractions were not likely observed between LMW-FAs and alkenone except for large fractions(>250μm). Ages of LMW-FAs for both shelf and slope were younger than those of alkenone in all fractions including bulk-phase sediments. Moreover, we obtained radiocarbon ages of marine-derived compounds (alkenone, LMW-FAs), plant wax-derived compounds(HMW-FAs), planktic foraminifera, and total organic carbon from the last deglaciation- Holocene covered-marginal sediments from western North Pacific (1366m water depth, N41°) and Okhotsk Sea (1225m water depth, N44°). We discuss with palaeoceanographic interpretation on sedimentary records such as alkenone temperatures and ventilation.

G02_P11

Carbon isotopic constraints on the sources and preservation of organic compounds in sediment of the South China Sea

Wang F^1,2, Fu W¹, Ren P², Zhang H¹, Luo C¹, Wang X^1,2

¹Ocean University Of China, Qingdao, China, ²Qingdao National Laboratory of Marine Science and Technology, Qingdao, China

Organic matter (OM) preservation in marine sediments is an important sink of carbon cycle and provides useful information on the sources, biodegradation and transformation of organic carbon during early diagenesis.  The South China Sea (SCS), as one of the largest semi-enclosed marginal sea in the western North Pacific Ocean, receives large amount of organic carbon fluxes from river input and land erosion, especially in its northern shelf and slope regions. The burial of organic compounds in sediment of the SCS, however, has not been well studied. Here, we present the first data set of radiocarbon combined with stable carbon isotope measurements of total organic carbon (TOC), hydrolysable amino acids (THAA), total lipids, humic acids (HA), and acid-base insoluble OM in four sediment cores collected from the northern slope of the SCS. Distinct differences in both ¹³C and ¹⁴C values were found among these compound classes. The δ¹³C values are more depleted for total lipids and HA (-23.1‰ to -30.2‰) than the THAA and the acid-base insoluble OM (-15.3‰ to -20.6‰). The D¹⁴C values ranged from -632‰ to -194‰ in TOC, -331‰ to -66‰ in THAA, -574‰ to -253‰ in total lipids, -569‰ to -168‰ in HA, and -848‰ to -458‰ in acid-base insoluble OM, respectively. The acid-base insoluble OM has the oldest ¹⁴C ages (mean 7800 years) among the compound classes in the sediments. These distinct isotopic signatures provide new insight and reveal the selective decomposition, transformation and preservation mechanisms of OM derived from different sources in marine sediment.

G02_P12

Bomb-pulse radiocarbon record for a well-dated Caribbean coral core

Winkler S^1,2,  Steier P², Carilli J³

¹Helmholtz-zentrum Dresden-Rossendorf, Dresden, Germany, ²Universität Wien, Wien, Austria, ³ University of California San Diego, La Jolla , USA

The radiocarbon bomb-pulse created by nuclear weapons testing in the 1950s and 1960s has created a massive spike of atmospheric ¹⁴C, which has been used in the study of the global carbon cycle in many subsystems including the marine environment. Coral records of bomb-pulse era ¹⁴C have been studied over the past decades to gain insight into the uptake and mixing of atmospheric CO₂ in the ocean. The ¹⁴C level seen in surface waters is specific to the origin of the water masses and ocean-atmosphere exchange of CO₂.

We present results for radiocarbon levels in coral aragonite with yearly resolution for a coral core from Belize. The core has a well-established stratigraphy, stretching from the onset of atmospheric testing of thermonuclear devices to 2007. The core has previously been analyzed for and trace metal content in relation to environmental impacts and the bomb-pulse of ²³⁶U. We compare the results with existing results and model expectations for the Caribbean Sea. We further discuss the close agreement for the prior results in terms of feasibility and the achievable accuracy of cross-dating of cores using the rise of radiocarbon by the atmospheric bomb-pulse.