Cosmogenic radionuclides in Arctic Ocean sediments - applications for paleoceanography and geochronology

In this thesis, the use of the authigenic 10Be/9Be ratio extracted from the reactive phase of marine
sediments is evaluated for its potential as a proxy for paleoceanographic reconstructions in the Arctic
Ocean. Cosmogenic 10Be is produced in the atmosphere and transferred to Earth’s surface through wet
deposition (Lal & Peters, 1967). In the Arctic Ocean, in addition to direct atmospheric input, 10Be is also
supplied by oceanic advection, with the North Atlantic inflow representing the dominant modern source
(Frank et al., 2009; Ollive et al., submitted – Manuscript 2). Arctic rivers also contribute a fraction of 10Be
that was previously deposited on land (Strobl et al., 1999). In contrast, stable 9Be, of terrigenous origin, is
released through continental weathering and transported to the Arctic Ocean mainly via rivers, although
a portion is likewise delivered by Atlantic water masses.
The interplay between oceanic and riverine inputs can be effectively traced in the sediments using the
authigenic 10Be/9Be ratio, as these two sources exhibit distinct signatures differing by approximately one
order of magnitude ([5 - 8] × 10-8 and [0.5 - 1.5] × 10-8, respectively for oceanic and riverine inputs; Frank
et al., 2009). This characteristic enables several applications, including tracing the transfer of riverine
signals from continental shelves to the open ocean - a process critical for understanding the Arctic 10Be
budget (Manuscript 1) - and reconstructing variability in North Atlantic inflow during glacial-interglacial
cycles (Manuscript 2), with further implications for marine ecosystems, sea-ice evolution, and
paleoglaciology.
Furthermore, as a radionuclide, 10Be can be applied to decay dating of old Arctic deep-sea sediments (e.g.,
Frank et al., 2008). In combination with another cosmogenic radionuclide, 26Al, this thesis presents the
first attempt to apply the 26Al/10Be ratio as a decay-dating tool to a well-studied sediment core from the
Lomonosov Ridge (PS2185-3/6; Manuscript 3).