Thursday, March 14, 2013, 4:30PM - 5:30PM
RL-1 room 269
Full title: "Reconstructing the vertical 14C gradient of the Baja Margin during the last deglaciation"
Abstract: The radiocarbon activity (Δ14C) of the atmosphere decreased in two steps during the last deglaciation, coinciding with the well-known Heinrich 1 (H1) and Younger Dryas (YD) stadials. A leading explanation for these periods of decline involves the release of 14C-depleted carbon from a deep, isolated ocean reservoir, which could also help explain the deglacial rise in atmospheric CO2. Reconstructions of intermediate water Δ14C in the eastern Pacific (Marchitto et al., 2007 Science) and the Arabian Sea (Bryan et al., 2010 Earth Planet. Sci. Lett.) document two intervals of extreme depletion relative to the coeval atmosphere during H1 and the YD that are interpreted as evidence of the return of aged carbon from a deep reservoir to the upper ocean and atmosphere.
14C measurements in planktic and benthic foraminifera from several cores near the Baja California margin expand the depth range of these observations and enable reconstruction of the vertical Δ14C gradient during deglaciation. In preliminary results, the reconstructed deglacial gradient supports a source of aged carbon that reached the Baja margin laterally, rather than upwelling from a local deep source, and suggests enhanced local upwelling during the Bølling-Allerød period. This talk will use the current study as a way to introduce the audience to the use of 14C as a paleoceanographic carbon cycle tracer.