Publication Date:
2013-09-11
Description:
[1] Low planktic and benthic δ 18 O and δ 13 C values in sediments from the Nordic seas of cold stadials of the last glaciation have been attributed to brines, formed similar to modern ones in the Arctic Ocean. To expand on the carbon isotopes of this hypothesis I investigated benthic δ 13 C from the modern Arctic Ocean. I show that mean δ 13 C values of live epibenthic foraminifera from the deep Arctic basins are higher than mean δ 13 C values of upper slope epibenthic foraminifera. This agrees with mean high δ 13 C values of dissolved inorganic carbon (DIC) in Arctic Bottom Water (ABW), which are higher than mean δ 13 C DIC values from shallower water masses of mainly Atlantic origin. However, adjustments for oceanic 13 C-Suess depletion raise subsurface and intermediate water δ 13 C DIC values over ABW δ 13 C DIC ones. Accordingly, during preindustrial Holocene times, the δ 13 C DIC of ABW was as high or higher than today, but lower than the δ 13 C DIC of younger subsurface and intermediate water. If brine-enriched water significantly ventilated ABW, brines should have had high δ 13 C DIC values. Analogously, high-δ 13 C DIC brines may have been formed in the Nordic seas during warm interstadials. During cold stadials, when most of the Arctic Ocean was perennially sea-ice covered, a cessation of high-δ 13 C DIC brine rejection may have lowered δ 13 C DIC values of ABW, and ultimately the δ 13 C DIC in Nordic seas intermediate and deep water. So, in contrast to the idea of enhanced brine formation during cold stadials, the results of this investigation imply that a cessation of brine rejection would be more likely.
Print ISSN:
0883-8305
Electronic ISSN:
1944-9186
Topics:
Geosciences
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