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.