skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: A FRAMEWORK FOR TRANSDISCIPLINARY RADIOCARBON RESEARCH: USE OF NATURAL-LEVEL AND ELEVATED-LEVEL 14 C IN ANTARCTIC FIELD RESEARCH
ABSTRACT Radiocarbon ( 14 C) is an isotopic tracer used to address a wide range of scientific research questions. However, contamination by elevated levels of 14 C is deleterious to natural-level laboratory workspaces and accelerator mass spectrometer facilities designed to precisely measure small amounts of 14 C. The risk of contaminating materials and facilities intended for natural-level 14 C with elevated-level 14 C-labeled materials has dictated near complete separation of research groups practicing profoundly different measurements. Such separation can hinder transdisciplinary research initiatives, especially in remote and isolated field locations where both natural-level and elevated-level radiocarbon applications may be useful. This paper outlines the successful collaboration between researchers making natural-level 14 C measurements and researchers using 14 C-labeled materials during a subglacial drilling project in West Antarctica (SALSA 2018–2019). Our strict operating protocol allowed us to successfully carry out 14 C labeling experiments within close quarters at our remote field camp without contaminating samples of sediment and water intended for natural level 14 C measurements. Here we present our collaborative protocol for maintaining natural level 14 C cleanliness as a framework for future transdisciplinary radiocarbon collaborations.  more » « less
Award ID(s):
1755125
PAR ID:
10317467
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ;
Date Published:
Journal Name:
Radiocarbon
Volume:
63
Issue:
5
ISSN:
0033-8222
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. 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
  2. ABSTRACT Late Holocene relative sea-level reconstructions are commonly generated using proxies preserved in salt-marsh and mangrove sediment. These depositional environments provide abundant material for radiocarbon dating in the form of identifiable macrofossils (salt marshes) and bulk organic sediment (mangroves). We explore if single-step graphitization of these samples in preparation for radiocarbon dating can increase the number and temporal resolution of relative sea-level reconstructions without a corresponding increase in cost. Dating of salt-marsh macrofossils from the northeastern United States and bulk mangrove sediment from the Federated States of Micronesia indicates that single-step graphitization generates radiocarbon ages that are indistinguishable from replicates prepared using traditional graphitization, but with a modest increase in error (mean/maximum of 6.25/15 additional 14 C yr for salt-marsh macrofossils). Low 12 C currents measured on bulk mangrove sediment following single-step graphitization likely render them unreliable despite their apparent accuracy. Simulated chronologies for six salt-marsh cores indicate that having twice as many radiocarbon dates (since single-step graphitization costs ∼50% of traditional graphitization) results in narrower confidence intervals for sample age estimated by age-depth models when the additional error from the single-step method is less than ∼50 14 C yr (∼30 14 C yr if the chronology also utilizes historical age markers). Since these thresholds are greater than our empirical estimates of the additional error, we conclude that adopting single-step graphitization for radiocarbon measurements on plant macrofossils is likely to increase precision of age-depth models by more than 20/10% (without/with historical age markers). This improvement can be implemented without additional cost. 
    more » « less
  3. Abstract Cosmic rays and solar energetic particles pose significant risks to satellites, space stations, and human space exploration. They also produce atmospheric radiocarbon (14C), which enters the carbon cycle and is recorded by paleoenvironmental proxies. Miyake events, rapid increases in atmospheric14C, first identified in annual tree rings and later confirmed through ice core10Be and36Cl isotopes, are thought to result from extreme solar activity, are seven events identified over the last 14,300 years. However, uncertainty in annual14C measurements limits precise inferences about their timing and magnitude. This study examines uncertainties in14C during two Miyake events (774 CE and 993 CE) across trees with differing uptake, storage, and allocation of carbon. We hypothesize that tree species physiology affects tree‐ring Δ14C, with deciduous species recording lagged, attenuated tree‐ring Δ14C relative to evergreen species. Using Δ14C data from pine and larch in Mongolia and a larger multi‐species Northern Hemisphere data set, we employed a Bayesian framework to estimate the timing, duration, and magnitude of these two events. Our AMS results showed no differences in Δ14C between evergreen and deciduous species growing at similar sites during the 774 CE event. The 993 CE event was variable, but parameter estimates were consistent between species. Northern Hemisphere comparisons indicated that annual series of Δ14C from evergreen and deciduous conifers yielded relatively more precise modeled estimates of start date and duration relative to deciduous broadleaf species. Future studies should consider the role of species‐specific carbon allocation strategies and storage dynamics in determining the radiocarbon response to Miyake events. 
    more » « less
  4. ABSTRACT Replicate radiocarbon ( 14 C) measurements of organic and inorganic control samples, with known Fraction Modern values in the range Fm = 0–1.5 and mass range 6 μg–2 mg carbon, are used to determine both the mass and radiocarbon content of the blank carbon introduced during sample processing and measurement in our laboratory. These data are used to model, separately for organic and inorganic samples, the blank contribution and subsequently “blank correct” measured unknowns in the mass range 25–100 μg. Data, formulas, and an assessment of the precision and accuracy of the blank correction are presented. 
    more » « less
  5. The Carbon in Permafrost Experimental Heating Research (CiPEHR) project addresses the following questions: 1) Does ecosystem warming cause a net release of C from the ecosystem to the atmosphere?, 2) Does the decomposition of old C, that comprises the bulk of the soil C pool, influence ecosystem C loss?, and 3) How do winter and summer warming alone, and in combination, affect ecosystem C exchange? We are answering these questions using a combination of field and laboratory experiments to measure ecosystem carbon balance and radiocarbon isotope ratios at a warming experiment located in an upland tundra field site near Healy, Alaska in the foothills of the Alaska Range. This data set includes weekly thaw depth measurements collected from winter warming, summer warming, and control treatment plots at CiPEHR. Additional measurements from on-plot gas flux wells, water table monitoring wells, and off-plot locations are also reported. Note that the experimental warming portion of this experiment concluded in 2022. These data are a continuation of measurements taken at previously warmed plots but plots were not actively manipulated after 2022. At the Gradient Thaw Site, in this larger study, we are asking the question: Is old carbon that comprises the bulk of the soil organic matter pool released in response to thawing of permafrost? We are answering this question by using a combination of field and laboratory experiments to measure radiocarbon isotope ratios in soil organic matter, soil respiration, and dissolved organic carbon, in tundra ecosystems. The objective of these proposed measurements is to develop a mechanistic understanding of the SOM sources contributing to C losses following permafrost thawing. We are making these measurements at an established tundra field site near Healy, Alaska in the foothills of the Alaska Range. Field measurements center on a natural experiment where permafrost has been observed to warm and thaw over the past several decades. This area represents a gradient of sites each with a different degree of change due to permafrost thawing. As such, this area is unique for addressing questions at the time and spatial scales relevant for change in arctic ecosystems. 
    more » « less