Coccolithophore variability from the Shackleton Site (IODP Site U1385) through MIS 16-10

Coccolithophore productivity at the western Iberian Margin during the middle Pleistocene (310–455 ka) – evidence from coccolith Sr/Ca data

“…At a water depth of 1895 m, site MD03-2699 would have been located above the Antarctic Bottom Water influence (placed near 2500 m in the western North Atlantic; Thunell et al, 2002). Two lines of evidence confirm that corrosive southern sourced waters did not affect the coccolithophore assemblages in core MD03-2699: a) there is no evidence for increased abundance of larger, more calcified coccoliths, more resilient to dissolution, in detriment of smaller and less calcified coccoliths in the coccolithophore flora (Amore et al, 2012); b) at IODP Site U1385, located about 520 500 m deeper than our site, Maiorano et al (2015) found low coccolith dissolution indices, varying between 1 and 0.9, against the values below 0.25 (MIS 12a) and 0.5 (MIS 10a) for core MD01-2446 at 3570 m (Marino et al, 2014). Since https://doi.org/10.5194/cp-2019-131 Preprint.…”

“…Although a possible bias effect exists in those samples, it does not prove 260 that coccolithophore productivity did not decrease significantly during those intervals (see Discussion). Bias due to reworked coccoliths contribution is negligible because reworked coccolith abundance was generally below 2% not only in our study site (Amore et al, 2012) but also in other IbM sites for the same time interval (Maiorano et al, 2015;Marino et al, 2014).…”

“…Off western Iberia, in core MD03-2699, the deglacial SST increase and the subsequent particularly stable SSTs during MIS 11c were linked to a dominant influence of the subtropical waters of the Azores and Iberian Poleward Currents (Rodrigues et al, 2011;Voelker et al, 2010). Accordingly, during MIS 9e and MIS 11c, the abundance of warm coccolith taxa increased (Amore et al, 2012;Maiorano et al, 2015;Marino et al, 2014;Palumbo et al, 2013a) as well as the abundance of tropical planktonic foraminifera species in cores MD01-2443 (de Abreu et al, 2005) Besides changes in the nutrient availability promoted by changes in the advection of the dominant water masses in the IbM, 335 fluctuations in the upwelling regime, precipitation and arid plus windy conditions could also have played a role in determining coccolithophore productivity.…”

“…Previous studies in the IbM used coccolith-derived proxies, such as coccolith assemblages, nannofossil accumulation rates (NAR), and total alkenone fluxes (produced mostly by coccolithophores) to reconstruct changes in coccolithophore paleoproductivity (Amore et al, 2012;Maiorano et al, 2015;Marino et al, 2014;Palumbo et al, 2013a). The traditional proxies depend not only on the supply of coccoliths or organic compounds but also on dilution by minerals and other sediment constituents and on changing preservation conditions (Rullkötter, 2006).…”

Insolation forcing of coccolithophore productivity in the North Atlantic during the Middle Pleistocene

“…Coccolithophores are the main primary producers in temperate regions of the open ocean (Brand, 1994) producing biogenic calcite (Bolton et al, 2016) and mediating cycling, sequestration and export of organic and inorganic carbon (Rost and Riebesell, 2004;Baumann et al, 2005). Coccoliths, the minute calcite plates that cover coccolithophore cell, are very abundant in seafloor sediments and have been extensively used as paleoenvironmental tracers providing information on paleoceanographic conditions and composition of the overlying photic zone's communities (e.g., Flores et al, 2003;Baumann et al, 2005;Marino et al, 2014;Emanuele et al, 2015;Maiorano et al, 2015). Enhanced coccolithophore calcification during glacials and terminations has been suggested to drive a decrease in the availability of the carbonate ion in the ocean and trigger the deglacial rise in atmospheric carbon dioxide (pCO 2 ) (Rickaby et al, 2010;Omta et al, 2013).…”