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

Abstract

 High-resolution coccolithophore record reveal upwelling-related primary productivity variations not previously described.  Multiproxy integration allows the assessment of the control by major atmospheric circulation changes at orbital and suborbital timescales.  Reductions in surface productivity during abrupt cold episodes is the result of upwelling limitation by hydrological changes.

New Insights Into the Surface‐Ocean Dynamics of the Northeastern Atlantic Ocean Across the Marine Isotope Stage 7

“…This could have resulted in high surface productivity of SW Iberian Margin (Figure 6), a scenario similar to the modern (+) NAO‐like configuration, when the North Atlantic atmospheric circulation intensifies and the westerly wind system shifts northward (e.g., Alvarez et al., 2009; Barton et al., 2001; Coste et al., 1986; Pailler & Bard, 2002; Sousa & Bricaud, 1992; Vitorino et al., 2002). Our interpretations are in agreement with the earlier studies from the SW Iberian Margin proposing a similar scenario to explain the surface productivity changes during MIS 11 and MIS 9 interglacials (Amore et al., 2012; González‐Lanchas et al., 2021). Coupled ocean‐atmosphere general circulation model studies have also demonstrated that present‐day NAO‐like modes also operated in the past at orbital timescale (e.g., Lohmann, 2017).…”

“…-based SST records than our SST records during the stadials, might be due to the preferential degradation of C 37:3 alkenones (e.g., Gong & Hollander, 1999;Kim et al, 2009;Rontani & Wakeham, 2008;Turich et al, 2013;Zabeti et al, 2010).…”

“…Surface hydrography and productivity conditions along the SW Iberian Margin are modulated by various physical parameters such as the surface winds, surface currents, migration of the thermal fronts, nutrients in the sub‐surface waters and the offshore displacement of the coastal upwelling filaments (e.g., Amore et al., 2012; Ausín et al., 2020; Cavaleiro et al., 2020; González‐Lanchas et al., 2021; Incarbona et al., 2010; Pailler & Bard, 2002; Palumbo et al., 2013; Salgueiro et al., 2014; Singh et al., 2023; Voelker et al., 2009). A detailed assessment of these coupled ocean‐atmospheric parameters is essential to better understand the underlying processes driving the surface ocean conditions.…”

“…Conversely, the low surface productivity during the early phases of MIS 7e, MIS 7c and MIS 7a could be attributed to the reduced upwelling due to the weaker trade winds (weakening and southward shift of the AH) and the enhanced AzC/IPC influence bringing the nutrient‐poor ENACWst water along the SW Iberian Margin. Earlier studies from the Iberian Margin have suggested a common physical forcing that is, AH pressure system, responsible for the productivity variability during the interglacials (e.g., Amore et al., 2012; Argenio et al., 2021; Ausín et al., 2020; Cavaleiro et al., 2020; González‐Lanchas et al., 2021; Singh et al., 2023). Hence, the AH pressure system might have played a crucial role in modulating the upwelling and surface productivity during MIS 7e, MIS 7c, and MIS 7a, analogous to the modern conditions (Barton et al., 2001; Fiúza et al., 1998; Relvas et al., 2007).…”