Monsoonal Forcing of European Ice‐Sheet Dynamics During the Late Quaternary

Abstract

The dynamics of Northern Hemisphere ice sheets during Late Quaternary glacials have yet been dominantly examined from a Laurentide Ice Sheet perspective, which helped shaping the idea of moisture‐starved glacials and small‐scale ice volume variability. However, the waxing and waning of the European Ice Sheet (EIS) casts doubt on this perception. Understanding EIS dynamics under glacial boundary conditions is crucial because its meltwater pulses influence global climate by weakening deepwater formation in the North Atlantic Ocean. Here we show that the advection of subtropical water toward the continental margin of western Europe lead to enhanced moisture availability on the continent and fueled the growth of EIS lobes during glacials. This warm‐water pooling was caused by monsoonally paced enhanced Mediterranean Outflow Water (MOW) entrainment that dragged subtropical surface waters toward the European margin. This mechanism presents a yet unrecognized marine‐terrestrial pathway that allows low‐latitude forcing to shape high‐latitude glaciations.

Mediterranean Overflow Over the Last 250 kyr: Freshwater Forcing From the Tropics to the Ice Sheets

“…The fine sand content at Site U1389 today is relatively high due to the high speed of the MOW flowing over this site, which is in the order 0.1–0.5 m s −1 (Sanchez‐Leal et al, 2017). The overall good correlation between the record of fine sand content and the Zr/Al record published by (Bahr et al, 2015; Kaboth‐Bahr et al, 2018) (Figure 4c) support that the fine sand percentage used in this study is a good proxy for the strength of the MOW at this site. The high abundance of detrital particles, including heavy minerals, in the fine sand fraction (Bahr et al, 2015) explains this correlation and supports the existence of a high‐velocity bottom current capable of transporting fine sand detrital particles along the slope of the Gulf of Cadiz.…”

“…Removal of fine-grained particles by winnowing due to this high-speed current was behind the generation of these sandy-rich contourite beds as reported by various authors (Gonthier et al, 1984;Stow et al, 1986). (Bahr et al, 2015;Kaboth-Bahr et al, 2018). Codes at the bottom show MIS stages and substages after Railsback et al (2015).…”

“…(b) Percent fine sand (fraction 62–150 μm). (c) Zr/Al record (Bahr et al, 2015; Kaboth‐Bahr et al, 2018). Codes at the bottom show MIS stages and substages after Railsback et al (2015).…”

“…Because of the net loss of water in the Mediterranean (evaporation exceeding precipitation plus runoff) and the cold winds reaching the northern margins of the basin the density of Mediterranean water at Gibraltar is much higher than that of the Atlantic surface water, resulting in a Mediterranean Outflow at depth and an Atlantic inflow at surface (Bethoux & Gentili, 1999; Bryden et al, 1994). A series of studies have investigated the evolution of the MOW by analyzing changes in the physical or geochemical properties of the sediments in various sites along the Gulf of Cadiz contourite depositional system (Bahr et al, 2015; Bryden & Kinder, 1991; Bryden & Stommel, 1982; Kaboth et al, 2016; Kaboth, de Boer, et al, 2017; Kaboth, Grunert, et al, 2017; Kaboth‐Bahr et al, 2018; Lebreiro et al, 2015, 2018; Llave et al, 2006; Singh et al, 2015; Stow et al, 2013; Toucanne et al, 2007; Voelker et al, 2006, 2015). Most of them point to the straight relationship between the intensity of MOW and Northern Hemisphere climate variability.…”

“…Most of them point to the straight relationship between the intensity of MOW and Northern Hemisphere climate variability. The longer records suggest a strong correlation with orbital changes in African monsoons (Bahr et al, 2015; Kaboth et al, 2017; Kaboth‐Bahr et al, 2018; Lofi et al, 2016; Voelker et al, 2015). However, there are still some features of the MOW variability, that remain poorly understood, especially those associated to MOW behavior during Heinrich stadials (HSs) and the interaction between orbital and millennial‐scale variability because most of the works already published about the millennial response of the MOW are focused on the last 60 kyr, where the influence of precession is small.…”