Radiocarbon constraints on the extent and evolution of the South Pacific glacial carbon pool

Abstract

During the last deglaciation, the opposing patterns of atmospheric CO2 and radiocarbon activities (Δ14C) suggest the release of 14C-depleted CO2 from old carbon reservoirs. Although evidences point to the deep Pacific as a major reservoir of this 14C-depleted carbon, its extent and evolution still need to be constrained. Here we use sediment cores retrieved along a South Pacific transect to reconstruct the spatio-temporal evolution of Δ14C over the last 30,000 years. In ∼2,500–3,600 m water depth, we find 14C-depleted deep waters with a maximum glacial offset to atmospheric 14C (ΔΔ14C=−1,000‰). Using a box model, we test the hypothesis that these low values might have been caused by an interaction of aging and hydrothermal CO2 influx. We observe a rejuvenation of circumpolar deep waters synchronous and potentially contributing to the initial deglacial rise in atmospheric CO2. These findings constrain parts of the glacial carbon pool to the deep South Pacific.

Massive remobilization of permafrost carbon during post-glacial warming

“…during the deglaciation undoubtedly demonstrates that important reorganization has occurred among Earth system carbon reservoirs6. It is still unclear to what extent marine and terrestrial carbon pools have contributed although the emerging picture suggests that a combination of processes must have been operating278101112. Our results from Arctic sediments confirm that the last glacial–interglacial transition exerted first-order control on permafrost stability in high latitude watersheds with important consequences for large-scale carbon-climate feedbacks similar to what we might experience as a result of the modern climate change.…”

“…A unique process to explain the CO 2 variations has so far not been found. Upwelling of poorly ventilated abyssal water masses is one of the leading hypotheses78, although the search for a 14 C-depleted carbon reservoir in the deep ocean remains a matter of current debate910. Recently, alternative studies based on atmospheric records11, terrestrial records3 and modelling exercises21213 have inferred that destabilization of PF-C reservoirs might have played a key role in regulating atmospheric CO 2 levels on glacial–interglacial timescales.…”

Expedition 383 Prospectus: Dynamics of the Pacific Antarctic Circumpolar Current (DYNAPACC)

“…Figure F9. Antarctic Circumpolar Current (ACC) overturning circulation in the Pacific sector of the Southern Ocean (modified from Ronge et al, 2016). Glacial pattern (left): northernmost extent of sea ice and strong westerly winds (SWW).…”

Carbon burial in deep-sea sediment and implications for oceanic inventories of carbon and alkalinity over the last glacial cycle

“…It has been suggested that the rate of carbon input to the active pool increased during glacial maxima (Lund et al, 2016;Ronge et al, 2016) and/or deglaciations (Huybers and Langmuir, 2009;Stott et al, 2009;Zech, 2012). The magnitude of these carbon input variations is highly uncertain, and reconstructions of relative changes in volcanic outgassing rates over time suggest that the volcanic carbon input was notably delayed, relative to the deglacial increase in pCO 2 recorded in ice 5 cores, requiring other mechanisms to be important at this time Huybers and Langmuir (2009) and Roth and Joos (2012).…”