The 4.2 ka BP Event in the Mediterranean Region: an overview

Abstract

Abstract. The Mediterranean region and the Levant have returned some of the clearest evidence of a climatically dry period occurring around 4200 years ago. However, some regional evidence are controversial and contradictory, and issues remain regarding timing, progression and regional articulation of this event. In this paper we review the evidence from selected proxies (sea-surface temperature, precipitation and temperature reconstructed from pollen, δ18O on speleothems, and δ18O on lacustrine carbonate) over the Mediterranean basin to infer possible regional climate patterns during the interval between 4.3 and 3.8 cal ka BP. The values and limitations of these proxies are discussed, and their potential for furnishing information on seasonality is also explored. Despite the chronological uncertainties, which are the main limitations for disentangling details of the climatic conditions, the data suggests that winter over the Mediterranean was drier condition, in addition to already dry summers. However, some exceptions to this prevail, – where wetter condition seems to have persisted – suggesting regional heterogeneity in climate patterns. Temperature data, even if sparse, also suggest a cooling anomaly, even if this is not uniform. The most common paradigm to interpret the precipitation regime in the Mediterranean – a North Atlantic Oscillation-like pattern – is not completely satisfactory to interpret the selected data.

Western Mediterranean hydro-climatic consequences of Holocene ice-rafted debris (Bond) events

“…Following the line of argument above, peaks in the Sidi Ali δ 18 O curve are interpreted as North Atlantic-derived winter rain minima. This corresponds to noticeable parallels between the Sidi Ali δ 18 O curve and the prominent subpolar North Atlantic ice-rafted debris record (Bond et al, 2001) from stacked MC52 and VM29-191 marine cores (pale blue/orange bars in Fig. 3).…”

“…The direct comparison of palaeo-hydrological and palaeoecological data from the same core enables a multi-proxy interpretation without age uncertainties that allows a better understanding of the Western Mediterranean hydro-climate history. Furthermore, we correlate for the first time the newly established Sidi Ali δ 18 O record with the North Atlantic icerafting debris record (Bond et al, 2001) to identify a probable teleconnection between Western Mediterranean winter rains and ocean-atmosphere coupled cooling phases in the subpolar North Atlantic. Finally, we provide an analysis of the Western Mediterranean hydro-climate during the 4.2 ka climatic event (Bond event) that is the focus of the present Climate of the Past special issue.…”

“…Gerard C. Bond reconstructed a Holocene series of North Atlantic ice-rafting events (Bond et al, 1997(Bond et al, , 2001) based on the numbers of counted quartz and haematite-stained grains in marine cores recovered from the subpolar North Atlantic (Fig. 1a).…”

The 4.2 ka event in the central Mediterranean: new data from a Corchia speleothem (Apuan Alps, central Italy)

“…Thus, as a first-order interpretation, higher δ 18 O c values are considered to indicate a shift towards drier conditions, while lower values are associated with more humid periods (Drysdale et al, 2004;Zanchetta et al, 2007;Regattieri et al, 2014a). This "paradigm" holds for central and eastern Mediterranean speleothems (e.g., Bar-Matthews et al, 2003;Finné et al, 2017) and is also utilized for interpreting lacustrine marls, land snail shells and pedogenic carbonates in the region (e.g., Colonese et al, 2007Colonese et al, , 2014Regattieri et al, 2015Regattieri et al, , 2017Boretto et al, 2017;. However, this picture can be complicated by changes in the seasonality of rainfall distribution.…”

“…This effect cannot be completely captured from available SST data, which record spring and/or annual average temperature and not specific late summer-autumn temperature (e.g., Fig. 6; Cisneros et al, 2016;Jalali et al, 2016;Bini et al, 2018). From the available data, it seems possible that a general reduction in precipitation, as reflected in the CC27 stable isotope and trace element data for the Apuan Alps, must have involved reduced advection of vapor masses during winter and a reduction in cyclogenesis over the Gulf of Genoa.…”