A 130,000-year record of Levantine Intermediate Water flow variability in the Corsica Trough, western Mediterranean Sea

Abstract

Sortable silt particle-size data and stable isotope analyses from the Corsica Trough, western Mediterranean Sea, provide a continuous palaeoceanographic record of the inflow, ventilation and vertical fluctuations of the Levantine Intermediate Water (LIW) in the northern Tyrrhenian Sea for the last 130,000 years. The results presented herein reveal that climate changes drive the Mediterranean intermediate circulation on Milankovitch to millennial timescales. Intensified intermediate inflow and ventilation in the Corsica Trough occurred throughout the last glacial interval, with a cold/fasterwarm/slower pattern existing between the Dansgaard-Oeschger climatic oscillations (including Heinrich events) and the LIW variability. By contrast, a weak intermediate ventilation characterised the Holocene and the Last Interglacial period, especially during insolation maxima and the sapropel deposition in the eastern Mediterranean. This variability probably reflects the changes of the eastern Mediterranean net evaporation, as well as the propagation to the western Mediterranean of the profound hydrographic adjustments of the Levantine Sea and adjacent areas to climate forcing. The implications for the formation and ventilation of the Western Mediterranean Deep Water (WMDW) in the northwestern Mediterranean basin, as well as for Mediterranean-Atlantic exchange through the Strait of Gibraltar are discussed. Highlights ► The LIW dynamics in the Corsica Trough is reconstructed for the last 130,000 years. ► Climate changes drive the LIW dynamics on Milankovitch to millennial timescales. ► A cold/fasterwarm/slower pattern exists between climate and the LIW variability. ► Role of LIW in deep-water formation and Mediterranean-Atlantic exchange is examined.

Hydrological variations of the intermediate water masses of the western Mediterranean Sea during the past 20 ka inferred from neodymium isotopic composition in foraminifera and cold-water corals

“…Synchronously, cosmogenic dating of Alpine glacier retreat throughout the western Mediterranean hinterland suggests maximum retreat rates (Ivy-Ochs et al, 2007;Kelly et al, 2006). Overall, these events are responsible for freshening Mediterranean waters and reduced surface water density and, hence, weakened ventilation of intermediate (Toucanne et al, 2012) and deep-water masses Sierro et al, 2005). Similarly, lower benthic δ 13 C values obtained for the Balearic Sea (Fig.…”

“…Similarly, a grain-size record obtained from a sediment core collected within the LIW depth range (∼ 500 m water depth) at the eastern Corsica margin also documents enhanced bottom currents during the glacial period and for specific time intervals of the deglaciation, such as HS1 and YD (Toucanne et al, 2012). The Early Holocene is characterized by a collapse of the LIW (Kuhnt et al, 2008;Schmiedl et al, 2010;Toucanne et al, 2012) synchronous with the sapropel S1 deposition (10.2-6.4 cal ka BP; Mercone et al, 2000).…”

“…Similarly, a grain-size record obtained from a sediment core collected within the LIW depth range (∼ 500 m water depth) at the eastern Corsica margin also documents enhanced bottom currents during the glacial period and for specific time intervals of the deglaciation, such as HS1 and YD (Toucanne et al, 2012). The Early Holocene is characterized by a collapse of the LIW (Kuhnt et al, 2008;Schmiedl et al, 2010;Toucanne et al, 2012) synchronous with the sapropel S1 deposition (10.2-6.4 cal ka BP; Mercone et al, 2000). Proxies for deep-water conditions reveal the occurrence of episodes of deep-water overturning reinforcement in the eastern Mediterranean basin at 8.2 ka BP (Rohling et al, 1997(Rohling et al, , 2015Kuhnt et al, 2007;Abu-Zied et al, 20082015), responsible for the interruption of the sapropel S1 in the eastern Mediterranean basin (Mercone et al, 2001;Rohling et al, 2015).…”

“…The δ 18 O record obtained on G. bulloides indicates an abrupt 1 ‰ excursion towards lighter values centered at about 16 cal ka BP (Table 4) . (e) Sortable silt mean grain size of core MD01-2472 (Toucanne et al, 2012). (f) Ln Zr / Al ratio at IODP site U1387 (36 • 48.3 N 7 • 43.1 W; 559 m) .…”

Ten Years of Paleoceanographic Studies at ODP Site 963 (Central Mediterranean Sea)

“…However, physico-chemical properties (e.g. salinity and/or temperature), speed, ventilation and the vertical location of the LIW, the intermediate water mass formed in the Rhodes gyre area, seem to change during Stadial/Interstadial oscillations over the past 130 ka, both in the Sicily Channel and the Corsica Trough [14,16,60]. Further investigation is needed to understand processes that acted in the eastern Mediterranean basin, among others the role of the African monsoon variability in driving and/or preconditioning LIW formation processes.…”