Central Mediterranean rainfall varied with high northern latitude temperatures during the last deglaciation

Abstract

Similarly to the effects of current climate change, the last deglaciation (Termination I) rapidly altered northern latitude temperatures and ice-sheet extent, as well as the Atlantic Meridional Overturning Circulation. However, it is still unclear how these changes propagated and impacted the central Mediterranean continental rainfall variability. This prevents a full understanding on how global warming will affect Mediterranean areas in the future. Here, we present a high-resolution reconstruction of rainfall changes in the central Mediterranean across Termination I, based on a novel δ18O time series from a southern Italian stalagmite. Across Termination I the availability of Atlantic moisture varied in response to northern latitude temperature increases (decreases) and ice-sheet decreases (increases), promoting a higher (lower) intensity of the Atlantic Meridional Overturning Circulation, and resulting in a relatively wetter (drier) climate in the Mediterranean. In the light of future warming, this study emphasises the role of high-latitude climate changes in causing rainfall variation in highly populated Mediterranean areas.

Temperature and hydrological variations during the late-glacial in the Central Mediterranean: Application of the novel ostracod-clumped isotope thermometer

“…16 ky indicating a general decrease of rainfall amount (Fig. 5), corresponds well to the δ 18 Oc speleothem records from Sant'Angelo cave (southern Italy, Columbo et al, 2022), Ostolo cave (Northern Iberian Peninsula, Bernal-Wollum et al, 2021) and Soreq cave (Israel, Bar-Matthews et al, 2003). This trend, also observed in the NGRIP record (Rasmussen et al, 2016), confirms the continues influence of the ice-sheet extent variations at higher latitude on central Mediterranean area.…”

“…However, seasonal temperatures are different (11.8 ± 2.1 and 23.2 ± 2.5 °C). The same paleohydrological behavior has been observed in Lake Pergusa and Lake Preola (southern Italy) (Magny et al, 2012) and in Sant'Angelo cave (southern Italy, Columbo et al, 2022), as well as in eastern Mediterranean (Marino et al, 2009;Develle et al, 2010). Conversely, records from northern Italy and western Mediterranean present a higher seasonality contrast with drier summers during and after ca.…”

“…Ostracod assemblages still indicate low lake level/ephemeral conditions (Marchegiano et al, 2018) suggesting warmer season conditions more arid than today, as also recorded by pollen archives from southern and central Italy (Magny et al, 2012). On the contrary, speleothem δ 18 Oc mean annual records, indicate the onset of wetter conditions due to the decrease of ice-sheet extent, high availability of Atlantic moisture and increase of westerly-driven winter rainfall amount across the Mediterranean (Columbo et al, 2022). This contrasting signal continues to support a different seasonal rainfall amount most probably linked to summer insolation.…”

“…5). Considering that several studies in central and southern Italy, including pollen (e.g., Allen et al, 1999;Follieri et al, 1988) and speleothem records (Columbo et al, 2022), suggest a low precipitation during MIS2 in the central Mediterranean area, and that ostracod assemblages at Lake Trasimeno also indicate low lake level/ephemeral conditions (Marchegiano et al, 2018), the lighter values, in average, during MIS2 compared to MIS3 can be due to a decrease of evaporation as consequence of lower summer insolation (Fig. 5).…”

Dripping and underground river waters shed light on the ecohydrology of a show cave

“…Indeed, the investigation of infiltrating waters permits to clarify the natural biogeochemical processes occurring in the vadose zone ecosystem, and to assess their ecological features in relation to potential anthropogenic impacts (Fairchild & Treble, 2009; Fehér et al, 2016; Hartland et al, 2012; Moldovan et al, 2007; Motyka et al, 2005). In particular, the analysis of dripping water allows to understand and reconstruct the processes leading to speleothem deposition, hence their use as significant paleoenvironmental archives (Baldini et al, 2006; Columbu et al, 2018, 2019, 2020, 2022; Fairchild et al, 2000; Fairchild & Baker, 2012; Fairchild & Treble, 2009; Lauritzen, 2018; Nava‐Fernandez et al, 2020; Riechelmann et al, 2013; Rossi & Lozano, 2016; Tremaine & Froelich, 2013; Wong et al, 2011). Indeed, several studies on cave waters have been, and still are, primarily focused on the ecohydrology of karst systems (Motyka et al, 2005; Nannoni et al, 2020), comprising the dissolution/precipitation processes (Fairchild & Baker, 2012) and the surface pollution sources affecting them (D'Angeli et al, 2017; Jiménez‐Sánchez et al, 2008; Mahler & Massei, 2007; Ruggieri et al, 2017).…”