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Less Remineralized Carbon in the Intermediate‐Depth South Atlantic During Heinrich Stadial 1
Author(s) -
Lacerra Matthew,
Lund David C.,
Gebbie Geoffrey,
Oppo Delia W.,
Yu Jimin,
Schmittner Andreas,
Umling Natalie E.
Publication year - 2019
Publication title -
paleoceanography and paleoclimatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.927
H-Index - 127
eISSN - 2572-4525
pISSN - 2572-4517
DOI - 10.1029/2018pa003537
Subject(s) - stadial , deglaciation , oceanography , alkalinity , geology , dissolved organic carbon , upwelling , biological pump , carbon dioxide in earth's atmosphere , phytoplankton , climate change , chemistry , holocene , nutrient , organic chemistry
The last deglaciation (~20–10 kyr BP) was characterized by a major shift in Earth's climate state, when the global mean surface temperature rose ~4 °C and the concentration of atmospheric CO 2 increased ~80 ppmv. Model simulations suggest that the initial 30 ppmv rise in atmospheric CO 2 may have been driven by reduced efficiency of the biological pump or enhanced upwelling of carbon‐rich waters from the abyssal ocean. Here we evaluate these hypotheses using benthic foraminiferal B/Ca (a proxy for deep water [CO 3 2− ]) from a core collected at 1,100‐m water depth in the Southwest Atlantic. Our results imply that [CO 3 2− ] increased by 22 ± 2 μmol/kg early in Heinrich Stadial 1, or a decrease in ΣCO 2 of approximately 40 μmol/kg, assuming there were no significant changes in alkalinity. Our data imply that remineralized phosphate declined by approximately 0.3 μmol/kg during Heinrich Stadial 1, equivalent to 40% of the modern remineralized signal at this location. Because tracer inversion results indicate remineralized phosphate at the core site reflects the integrated effect of export production in the sub‐Antarctic, our results imply that biological productivity in the Atlantic sector of the Southern Ocean was reduced early in the deglaciation, contributing to the initial rise in atmospheric CO 2 .