Open AccessCarbon storage in the mid‐depth Atlantic during millennial‐scale climate events
Author(s) -
Lacerra Matthew,
Lund David,
Yu Jimin,
Schmittner Andreas
Publication year - 2017
Publication title -
paleoceanography
Language(s) - English
Resource type - Journals
eISSN - 1944-9186
pISSN - 0883-8305
DOI - 10.1002/2016pa003081
Subject(s) - stadial , geology , deglaciation , oceanography , north atlantic deep water , younger dryas , tropical atlantic , atlantic multidecadal oscillation , thermohaline circulation , isotopes of carbon , benthic zone , climatology , total organic carbon , climate change , holocene , sea surface temperature , chemistry , environmental chemistry
Carbon isotope minima were a ubiquitous feature of the mid‐depth Atlantic during Heinrich Stadial 1 (HS1, 14.5–17.5 kyr BP) and the Younger Dryas (YD, 11.5–12.9 kyr BP), yet their cause remains unclear. Recent evidence indicates that North Atlantic processes triggered the δ 13 C anomalies, with weakening of the Atlantic Meridional Overturning Circulation (AMOC) being the most likely driver. Model simulations suggest that slowing of the AMOC increases the residence time of mid‐depth waters in the Atlantic, resulting in the accumulation of respired carbon. Here we assess ΣCO 2 variability in the South Atlantic using benthic foraminiferal B/Ca, a proxy for [CO 3 2− ]. Using replicated high‐resolution B/Ca records from ~2 km water depth on the Brazil Margin, we show that [CO 3 2− ] decreased during HS1 and the YD, synchronous with apparent weakening of the AMOC. The [CO 3 2− ] response is smaller than in the tropical North Atlantic during HS1, indicating there was a north–south gradient in the [CO 3 2− ] signal similar to that for δ 13 C. The implied variability in ΣCO 2 is consistent with model results, suggesting that carbon is temporarily sequestered in the mid‐depth Atlantic during millennial‐scale stadial events. Using a carbon isotope mass balance, we estimate that approximately 75% of the HS1 δ 13 C signal at the Brazil Margin was driven by accumulation of remineralized carbon, highlighting the nonconservative behavior of δ 13 C during the last deglaciation.