CO₂ Release From Pockmarks on the Chatham Rise‐Bounty Trough at the Glacial Termination

Abstract

Pockmarks overlie subsurface deformation features indicative of over-pressurized vertical fluid flow  Negative Δ 14 C anomalies occur in sediments deposited near pockmarks at the glacial termination indicate 14 C-dead carbon was released from subducted carbonates.

Radiocarbon as a Dating Tool and Tracer in Paleoceanography

“…One important aspect of the spatial variability in LGM radiocarbon ventilation ages that has yet to be completely resolved, is the observation of extreme radiocarbon depletions (i.e., the equivalent of more than 4,000–10,000 14 C yrs offset from the contemporary atmosphere). These offsets have been observed in foraminifera from a handful of locations, primarily at intermediate water depths, off Galapagos and in the southern Pacific in particular (Bova et al., 2018; Ronge et al., 2016; Stott et al., 2009, 2019). The same challenge arises in accounting for “extreme” marine radiocarbon depletion anomalies that have been observed at a few locations subsequent to the LGM, across the last deglaciation (in both benthic and planktonic foraminifera), again primarily at intermediate water depths in the low‐latitude eastern Pacific (Lindsay et al., 2015; Marchitto et al., 2007; Rafter et al., 2018, 2019), but also the South Pacific (Ronge et al., 2016, 2019), and Arabian Sea (Bryan et al., 2010).…”

“…The first of these items requires that the proposed addition of geological carbon, directly to the deep ocean, was sufficient to alter the deep ocean's radiocarbon signature, while leaving its δ 13 C signature unaffected (Rafter et al., 2019; Stott et al., 2019), and while also leaving sea floor carbonate sediment preservation unaffected (Marchitto et al., 2007; Rafter et al., 2019). The latter requirement stems from the fact that the addition of CO 2 to the deep ocean would be expected to lower pH and shift the dissolved carbonate system equilibria away from carbonate ion, causing carbonate sediments to dissolve wherever carbonate ion concentrations dropped below carbonate saturation levels (they are close to saturation throughout the modern deep Pacific [Key et al., 2004]).…”

Deglacial Ventilation Changes in the Deep Southwest Pacific

“…Sediment core age models may be substantially improved using wood remains and tephra layers, but such records are geographically limited (Rafter et al, 2018;Siani et al, 2013;Sikes et al, 2000;Skinner et al, 2015;Zhao & Keigwin, 2018). Regardless of materials used, recent studies show that deep-water radiocarbon reconstructions could be further complicated by possible release of 14 C-depleted carbon from local geological settings (Lizarralde et al, 2010;Rafter et al, 2019;Ronge et al, 2016;Stott et al, 2019).…”

Estimates of Methane Release From Gas Seeps at the Southern Hikurangi Margin, New Zealand

“…Seismic and acoustic methods are useful tools to identify, map and characterize free gas accumulations in the subsurface (e.g., Judd and Hovland, 1992;Kim et al, 2020), evidence for past and present seepage at the seafloor (e.g., Stott et al, 2019) and gas release into the water column (e.g., Colbo et al, 2014;Böttner et al, 2020). In the subsurface, the presence of gas in the porespace significantly affects the elastic properties of the bulk sediment, primarily by reducing the bulk seismic velocities and generating a contrast in acoustic impedance.…”