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