Dynamic Intermediate Waters Across the Late Glacial Revealed by Paired Radiocarbon and Clumped Isotope Temperature Records

Abstract

Paired radiocarbon and clumped isotope temperature records from U/Th-dated Desmophyllum dianthus corals in the North Atlantic and Southern Ocean provide unique information about the history of intermediate waters (∼1,500-1,700 m) across the late glacial and deglaciation (∼35-10 ka). These measurements allow for the construction of radiocarbon-temperature crossplots, which help to identify water mass endmembers at different times across the deglaciation. Radiocarbon and temperature values from the late glacial fall outside the range of modern ocean data from near the sample collection sites. In the North Atlantic, radiocarbon values tend to be much older than the modern, while in the Southern Ocean, they are more often younger than the modern. Reconstructed temperatures vary around respective modern ocean values; however, warm waters are observed at the Last Glacial Maximum and across the deglaciation in the north and south. We interpret our data in the context of the modern hydrography of the Western North Atlantic and Southern Ocean, and we draw upon direct comparisons between sediment core-derived reconstructions of ocean circulation from the South Indo-Pacific and our deep-sea coral data from the Southern Ocean. Our North Atlantic data support accepted patterns of reduced North Atlantic Deep Water formation during Heinrich Stadials 1 and 2. In the Southern Ocean, deep-sea coral populations respond to changes in ocean structure that are also reflected in a depth profile of 13 C data from New Zealand, and data indicate that there was less influence of Pacific Deep Water between 1,500 and 1,700 m south of Tasmania across much of the deglaciation.

Stable and clumped isotope characterization of authigenic carbonates in methane cold seep environments

“…The Bonifacie et al, 2017 compilation has been found to be suited for carbonate minerals from -1 to 300 °C; however, the low temperature (T <20 °C) calibration points used in their compilation come from labs that produce "shallow slope" calibrations lines. The Caltech clumped isotope lab consistently produces calibration lines with steeper slopes (Ghosh et al, 2006;Tripati et al, 2010;Thiagarajan et al, 2011;Eagle et al, 2013;Hines et al, 2019). Additionally, the slowest growth inorganic calcite in an inorganic calcite experiment show that  47 values are consistent with the steep slope  47 -temperature calibration of Ghosh et al 2006 (see Figure 6 and 7 in (Levitt et al, 2018)).…”

Radiocarbon Evidence for the Contribution of the Southern Indian Ocean to the Evolution of Atmospheric CO2 Over the Last 32,000 Years

“…However, after the transformation of CDW to AAIW, 14 C-depleted waters that were not completely equilibrated with the atmosphere were possibly exported toward the north and decreased the radiocarbon content of intermediate waters in the Arabian Sea (Bryan et al, 2010). The comparison of our Southern Ocean records and the Drake Passage and Tasman coral records ( Figure S5; Burke & Robinson, 2012;Hines et al, 2019) further highlights the importance of the Indian sector and its role in the deglacial carbon cycle. Both records reach modern-like ε 14 C values before the onset of the YD and do not show any excursion during the second rise in atmospheric CO 2 ( Figure S5).…”

“…Coral dredges that were performed at a similar latitude in the Drake Passage and off Tasmania also recorded upwelling CDW (Burke & Robinson, ; Hines et al, ). Converted to epsilon ε 14 C data (as used by Hines et al, ), Drake Passage data show similar values as recorded by PS69/907‐2, while the Tasman Sea corals that are located further to the north than the Drake Passage and our Kerguelen records show higher glacial values and might be indicative of a reduce influence of Pacific Deep Water (Figure S5; Burke & Robinson, ; Hines et al, ). At the end of the LGM, however, ΔΔ 14 C at 567 m (PS69/912) decreased by ~80‰, Δδ 13 C increased by ~0.3‰, and showed a decoupled trend from the atmosphere.…”

Climate Induced Thermocline Aging and Ventilation in the Eastern Atlantic Over the Last 32,000 Years

“…(b) CO 2 compilation record (Bereiter et al, 2015). (c) B-Atmosphere age reconstructed from cold-water corals: Azores Front Corals, Mauritania, and Angola (this study), as well as equatorial Atlantic (Chen et al, 2015(Chen et al, , 2020, New England Seamounts in 1,100-1,400 m depth (NESM; Eltgroth et al, 2006;Hines et al, 2019;Robinson et al, 2005;Thiagarajan et al, 2014), Tasmania (Hines et al, 2015), southwest Australia (Trotter et al, 2022) and Drake Passage (DP, Burke & Robinson, 2012;Chen et al, 2015;Li et al, 2020). Note: All B atm ages have been recalculated using IntCal20 and SHCal20 (Hogg et al, 2020;Reimer et al, 2020).…”

“…The CWCs off Mauritania are located near the Cap Verde Frontal Zone, while those off Angola are situated near the Angola-Benguela-Front. The Benguela Current carries water from the Antarctic Circumpolar Current and Agulhas Current, while the Angola Current flows southward.Our observations are compared to previously published CWC results (white stars) from the New England Seamount(Adkins et al, 1998;Eltgroth et al, 2006;Hines et al, 2019;Robinson et al, 2005;Thiagarajan et al, 2014), equatorial Atlantic(Chen et al, 2015(Chen et al, , 2020, Drake Passage(Burke & Robinson, 2012;Chen et al, 2015;Li et al, 2020), southwest Australia(Trotter et al, 2022) and Tasmania(Hines et al, 2015). (b) Hydrography around sample locations.…”