Coccolithophore variability across Marine Isotope Stage 11 in the Pacific sector of the Southern Ocean and its potential impact on the carbon cycle

Abstract

Proxy‐based reconstructions of past changes in the marine biological carbon pumps are limited, especially in the Southern Ocean. This work provides new insights into the productivity variations in the Pacific sector of the Southern Ocean. We present new data derived from three sediment cores that show glacial/interglacial coccolithophore variability across Marine Isotope Stage 11 (MIS 11). The cores were retrieved during R/V Polarstern cruise PS75 from the Subantarctic Zone and Polar Front Zone at the western flank of the East Pacific Rise and in the vicinity of the Antarctic‐Pacific Ridge. Coccolithophore assemblages were overwhelmingly dominated by the species Gephyrocapsa caribbeanica and small Gephyrocapsa. Total numbers of coccoliths, coccolith accumulation rates, coccolith fraction (CF; <20 μm fraction) Sr/Ca data, and temperature‐corrected CF Sr/Ca records consistently showed an increase in coccolithophore productivity during Termination V (MIS 12‐11 boundary), highest productivity throughout MIS 11 (~424–374 kyr), and a decrease during late MIS 11 in all the cores. We end with a discussion of back‐calculated coccolith calcification rate in the surface ocean and its potential contribution to changes in the concentration of atmospheric CO2.

Variations in export production, lithogenic sediment transport and iron fertilization in the Pacific sector of the Drake Passage over the past 400 kyr

“…3). A similar rise in CaCO 3 accumulation has also been recognized at other SAZ locations in the Atlantic (Hodell et al, 2000) and the Pacific (Gersonde, 2011;Saavedra-Pellitero et al, 2017) sectors of the SO, suggesting that the increase in CaCO 3 MAR during MIS 11 in core PS97/093-2 is part of a general pattern comprising at least the Pacific and Atlantic SAZ, likely caused by an exceptional southward migration of the ACC frontal systems in the Pacific sector of the SO (Saavedra-Pellitero et al, 2017). In order to assess the zonal dynamics of productivity and lithogenic flux variations along the Southern Ocean's SAZ, we compare our MAR reconstructions with previously published records from open-ocean areas of the SAZ (Anderson et al, 2014;Frank et al, 1999;Lamy et al, 2014;Martínez-Garcia et al, 2014;Nürnberg et al, 1997;Thöle et al, 2019).…”

Variations in export production, lithogenic sediment transport and iron fertilization in the Pacific sector of the Drake Passage over the past 400 ka

“…However, the absence of peaks 465 in the TOC and Ba xs MAR during the Holocene and MIS 5 suggest that the increased CaCO 3 export production did not impact significantly in the integrated proxies of export production, implying that export production by calcareous organisms was too small to have a noticeable impact on the total export during such intervals (Fig 3) Unlike other interglacials, during MIS 11, a prominent nannofossil ooze, primarily composed of Gephyrocapsa coccolithophore and foraminifera has been reported in the area (Lamy, 2016;Toyos et al, 2020) that is mirrored at our site by 470 CaCO 3 MARs one order of magnitude higher than in the Holocene and in MIS 5, and by increases in the Ba xs and TOC MARs (Fig 3). A similar rise in CaCO 3 accumulation has also been recognized at other SAZ locations in the Atlantic (Hodell et al, 2000) and the Pacific (Gersonde, 2011;Saavedra-Pellitero et al, 2017)…”

Control Mechanisms of Primary Productivity Revealed by Calcareous Nannoplankton From Marine Isotope Stages 12 to 9 at the Shackleton Site (IODP Site U1385)

“…Placoliths <3 µm of Gephyrocapsa genus were grouped as small Gephyrocapsa group following Flores, Bárcena, and Sierro (2000). This cluster mainly contains specimens of G. aperta and G. ericsonii , and those specimens with a closed central area widely considered as small G. caribbeanica (e.g., Saavedra‐Pellitero et al., 2017). Occasional small‐sized (<3 µm) G. muellerae/G.…”

“…The proportions of this group are here considered an indicator of the availability of highly fertilized surface waters of upwelling origin over the Site U1385. The extant G. caribbeanica is believed to have an affinity for ecological conditions comparable to those of the blooming Emiliania huxleyi (e.g., Saavedra‐Pellitero et al., 2017). In the modern IbM, maximum cell densities of E. huxleyi are closely associated with the highest Chl‐ a concentrations (e.g., Guerreiro et al., 2014).…”