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.