Component separation of oceanic helium

Abstract

Abstract. A new procedure to quantify, the components of oceanic helium ("terrigenic" 3He and 4He released from the ocean floor and "tritiugenic" 3He from tritium decay) is described. Terrigenic He and nonatmospheric 3He (i.e., terrigenic and tritiugenic combined) are obtained in terms of measured concentrations of the He isotopes and also of neon (Ne) (which improves the separation considerably), asstuning terrigenic He to vanish in the mixed layer. For the subsequent separation of terrigenic and tritiugemc 3He, additional information is required and 3He due to natural tritium represents a complication. The procedure is applied to data from a

Modelling of the anthropogenic tritium transient and its decay product helium-3 in the Mediterranean Sea using a high-resolution regional model

“…Helium-3 in the ocean originates from three different sources: (i) gas dissolution in equilibrium with atmospheric helium; (ii) addition by radioactive decay of tritium (called tritiugenic helium-3); and (iii) by injection of helium-3 into the oceans by the hydrothermal activity at deep sea spreading ridges, and also from the sediment above crusts by α-decay of heavy elements (called terrigenic helium-3). The most commonly used method of isolating the tritiugenic portion of helium-3 is the two-step procedure of Roether et al (1998) and Roether and Well (2001), using concurrent values of He, δ 3 He and neon (Ne) concentration, because the Ne generates a similar excess as the 3 He, but has no sources in the ocean interior. This methodology has already been applied on tritium data by Roether et al (1998Roether et al ( , 2013.…”

“…The most commonly used method of isolating the tritiugenic portion of helium-3 is the two-step procedure of Roether et al (1998) and Roether and Well (2001), using concurrent values of He, δ 3 He and neon (Ne) concentration, because the Ne generates a similar excess as the 3 He, but has no sources in the ocean interior. This methodology has already been applied on tritium data by Roether et al (1998Roether et al ( , 2013.…”

“…In this study, we simulate only the tritiugenic helium-3 (anthropogenic source), without representing the terrigenic helium-3 component (natural source). To isolate this tritiugenic helium-3 component in the observations, we apply the procedure of Roether et al (1998) and Roether and Well (2001).…”

Interbasin deep water exchange in the western Mediterranean

“…The gas content of the samples (40 mL) Atmospherically derived helium is dominating the distributions within the water, but the far more interesting property for studying interior processes within the ocean is the helium from the internal sources. Separating these components is generally difficult, but a method using neon measurements has been developed to separate the atmospheric influence from the interior source [Roether et al, 1998]. It makes use of the fact that, while neon is subject to the same changes as helium in the mixed layer, it does not have any interior sources.…”

Crustal helium in deep Pacific waters

“…Thereafter, in section 3 we address the data and the uncertainties of the quantities derived from them. A special approach is needed to deal with the fact that over much of the P17 section no neon data are available, while such data are needed in the separation procedure of terrigenic helium [Roether et al, 1998]. Property sections along P17 are presented and discussed in section 4, and in section 5 the results are summarized.…”