Single-Atom Counting for Ocean Science: 39Ar Circulation and 41Ca Marine Chronology

durch Prof. Zheng-Tian Lu (University of Science and Technology of China)

Montag 23.03.2026, 13:00 → 16:00 Europe/Berlin

5-1.213 - PAZIFIK / PACIFIC- Rechte Seite - Großer, unterteilbarer Konferenzraum (GEOMAR - Standort Ostufer / GEOMAR - East Shore)

Abstract:Understanding ocean circulation and reconstructing past climate both rely on reliable chronometers that operate over appropriate time scales. Atom Trap Trace Analysis (ATTA) is a laser-based method that counts individual atoms of rare isotopes with isotopic abundances as low as 10⁻¹⁸, free of isobaric interference. Originally developed for ⁸¹Kr groundwater and ice dating, ATTA now enables new applications in ocean science.

I will present recent progress in two areas. First, ³⁹Ar (half-life 300 yr) provides a direct tracer for intermediate and deep ocean ventilation over the 50–1500 year range, bridging the gap between ¹⁴C and transient tracers such as CFCs and SF₆. Advances in ATTA have reduced sample-size requirements to a few liters of seawater, compatible with standard Niskin bottle sampling.

Second, ⁴¹Ca (half-life 99 kyr) establishes a new radiocalcium chronometer for calcium-bearing marine archives. A global survey reveals a uniform deep-ocean ⁴¹Ca/Ca ratio, enabling dating of foraminifera and cold-water corals over ~40–500 kyr, complementary to U-series and stratigraphic methods.