Heidelberg 2015 – scientific programme

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UP: Fachverband Umweltphysik

UP 10: Ozeanographie

UP 10.7: Invited Talk

Thursday, March 26, 2015, 18:45–19:15, G/gHS

Evolution of nuclear weapon-produced tritium and its decay product He-3 in the Mediterranean Sea, 1952-2011 — •Wolfgang Roether — IUP Univ. Bremen

After 1952, tritium in the Mediterranean Sea (Med) rose 100-fold up to a 30 TU peak in 1965 (1 TU = [H-3/H] · 10¹⁸) and thereafter declined to about 1 TU in 2011. This resulted in a strong supply of its stable daughter He-3, concentrated in the 1960s. Terrigenic He being low in He-3 due to a predominantly crustal origin allowed precise determination of the tritiugenic He-3 (± 0.7% in delta He-3). The highest He-3 was found off the Tyrrhenian Sea in 1983 (delta He-3 ∼ 16%). The principle input into the subsurface waters occurs in the Eastern Med by way of the Levantine Intermediate Water (LIW), which moves as a high-salinity core westward toward the Strait of Gibraltar. The observations demonstrate strong longitudinal flow dispersion. As tritium-He-3 ages are biased toward times of strong input, one finds an age increase with calendar year of observation, attributed to fast flow contributions showing up first. A realistic estimate for transfer from the LIW source up to the Western Med is 22 years. Especially in the East, He-3 lately decreased distinctly, in response to the reduced He-3 generation.