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Southwest Pacific Vertical Structure Influences on Oceanic Carbon Storage Since the Last Glacial Maximum
Author(s) -
Clementi Vincent J.,
Sikes Elisabeth L.
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 - 10.1029/2018pa003501
Subject(s) - deglaciation , last glacial maximum , geology , oceanography , glacial period , water column , circumpolar deep water , deep sea , isotopes of carbon , transect , stadial , north atlantic deep water , holocene , total organic carbon , thermohaline circulation , geomorphology , chemistry , environmental chemistry
Abstract Lower atmospheric CO 2 concentrations during the Last Glacial Maximum (LGM; 23.0–18.0 ka) have been attributed to the sequestration of respired carbon in the ocean interior, yet the mechanism responsible for the release of this CO 2 during the deglaciation remains uncertain. Here we present calculations of vertical differences in oxygen and carbon isotopes (∆δ 18 O and ∆δ 13 C, respectively) from a depth transect of southwest Pacific Ocean sediment cores to reconstruct changes in water mass structure and CO 2 storage. During the Last Glacial Maximum, ∆δ 18 O indicates a more homogenous deep Pacific below 1,100 m, whereas regional ∆δ 13 C elucidates greater sequestration of CO 2 in two distinct layers: enhanced CO 2 storage at intermediate depths between ~940 and 1,400 m, and significantly more CO 2 at 1,600 m and below. This highlights an isolated glacial intermediate water mass and places the main geochemical divide at least 500 m shallower than the Holocene. During the initial stages of the deglaciation in Heinrich Stadial 1 (17.5–14.5 ka), restructuring of the upper ~2,000 m of the southwest Pacific water column coincided with sea‐ice retreat and rapid CO 2 release from intermediate depths, while CO 2 release from the deep ocean was earlier and more gradual than waters above it. These changes suggest that sea‐ice retreat and shifts in Southern Ocean frontal locations contributed to rapid CO 2 ventilation from the Southern Ocean's intermediate depths and gradual ventilation from the deep ocean during the early deglaciation.