More Like this

1. Revisiting Elevated δ ¹³ C Values of Sediment on Modern Carbonate Platforms

   https://doi.org/10.1029/2023GL107703  

   Trower, Elizabeth_J; Hibner, Brianna_M; Lincoln, Tyler_A; Dodd, Jacqueline_E; Hagen, Cedric_J; Cantine, Marjorie_D; Gomes, Maya_L (July 2024, Geophysical Research Letters)

   Abstract The measured carbon isotopic compositions of carbonate sediments (δ¹³C_carb) on modern platforms are commonly¹³C‐enriched compared to predicted values for minerals forming in isotopic equilibrium with the dissolved inorganic carbon (DIC) of modern seawater. This offset undermines the assumption that δ¹³C_carbvalues of analogous facies in the rock record are an accurate archive of information about Earth's global carbon cycle. We present a new data set of the diurnal variation in carbonate chemistry and seawater δ¹³C_DICvalues on a modern carbonate platform. These data demonstrate that δ¹³C_carbvalues on modern platforms are broadly representative of seawater, but only after accounting for the recent decrease in the δ¹³C value of atmospheric CO₂and shallow seawater DIC due to anthropogenic carbon release, a phenomenon commonly referred to as the¹³C Suess effect. These findings highlight an important, yet overlooked, aspect of some modern carbonate systems, which must inform their use as ancient analogs. 

   more » « less
2. Variation in δ ¹⁵ N and δ ¹³ C values of forages for Arctic caribou: effects of location, phenology and simulated digestion: Variation in δ ¹⁵ N and δ ¹³ C values of forages for Arctic caribou

   https://doi.org/10.1002/rcm.7849  

   Vansomeren, Lindsay L.; Barboza, Perry S.; Gustine, David D.; Syndonia Bret-Harte, M. (May 2017, Rapid Communications in Mass Spectrometry)
3. Biological Influence on δ ¹³ C and Organic Composition of Nascent Sea Spray Aerosol

   https://doi.org/10.1021/acsearthspacechem.0c00072  

   Crocker, Daniel R.; Hernandez, Ritchie E.; Huang, Haonan D.; Pendergraft, Matthew A.; Cao, Ruochen; Dai, Jiayin; Morris, Clare K.; Deane, Grant B.; Prather, Kimberly A.; Thiemens, Mark H. (September 2020, ACS Earth and Space Chemistry)

   null (Ed.)
4. Impacts of Carbonate Buffering on Atmospheric Equilibration of CO ₂ , δ ¹³ C _DIC , and Δ ¹⁴ C _DIC in Rivers and Streams

   https://doi.org/10.1029/2023GB007860  

   Winnick, Matthew J.; Saccardi, Brian (February 2024, Global Biogeochemical Cycles)

   Abstract Rivers and streams play an important role within the global carbon cycle, in part through emissions of carbon dioxide (CO₂) to the atmosphere. However, the sources of this CO₂and their spatiotemporal variability are difficult to constrain. Recent work has highlighted the role of carbonate buffering reactions that may serve as a source of CO₂in high alkalinity systems. In this study, we seek to develop a quantitative framework for the role of carbonate buffering in the fluxes and spatiotemporal patterns of CO₂and the stable and radio‐ isotope composition of dissolved inorganic carbon (DIC). We incorporate DIC speciation calculations of carbon isotopologues into a stream network CO₂model and perform a series of simulations, ranging from the degassing of a groundwater seep to a hydrologically‐coupled 5th‐order stream network. We find that carbonate buffering reactions contribute >60% of emissions in high‐alkalinity, moderate groundwater‐CO₂environments. However, atmosphere equilibration timescales of CO₂are minimally affected, which contradicts hypotheses that carbonate buffering maintains high CO₂across Strahler orders in high alkalinity systems. In contrast, alkalinity dramatically increases isotope equilibration timescales, which acts to decouple CO₂and DIC variations from the isotopic composition even under low alkalinity. This significantly complicates a common method for carbon source identification. Based on similar impacts on atmospheric equilibration for stable and radio‐ carbon isotopologues, we develop a quantitative method for partitioning groundwater and stream corridor carbon sources in carbonate‐dominated watersheds. Together, these results provide a framework to guide fieldwork and interpretations of stream network CO₂patterns across variable alkalinities. 

   more » « less
5. ASSESSING THE STRATIGRAPHIC INTEGRITY OF PLANKTIC AND BENTHIC ¹⁴ C RECORDS IN THE WESTERN PACIFIC FOR Δ ¹⁴ C RECONSTRUCTIONS AT THE LAST GLACIAL TERMINATION

   https://doi.org/10.1017/RDC.2020.82  

   Stott, Lowell D (October 2020, Radiocarbon)

   null (Ed.)

   ABSTRACT There is a growing database of radiocarbon ( 14 C) reconstructions from biogenic carbonate taken from marine sediment cores being used to investigate changing ocean circulation and carbon cycling at the end of the last great ice age. Reported here are 14 C results from a marine core taken in the Makassar Straits of the western equatorial Pacific that was intended to test whether there was evidence of geologic carbon release to the ocean during the glacial termination. A thorough investigation of planktic and benthic 14 C ages with stable isotopes and CT-scans revealed extensive burrowing in the upper 2 m of the core that displaced younger sediments downward by more than half a meter into the glacial section of the core. The vertical displacement is evident in both planktic and benthic fossils. However, the extent of displacement and the stratigraphic disturbance became evident only after multiple measurements of different species and genera. A CT-scan prior to sampling would be an effective screening tool to avoid sampling problem cores such as this. 

   more » « less