Speleothem Evidence for Megadroughts in the SW Indian Ocean during the Late Holocene

Abstract

Abstract. The 4.2 ka BP event is widely described as a 200–300 years long interval of major climate anomaly (typically, arid and cooler conditions potentially across the globe), which defines the beginning of the current Meghalayan age in the Holocene epoch. The 4.2 ka event however, has been disproportionately reported from proxy records situated at low-mid latitudes in the Northern Hemisphere. Consequently, the climatic manifestation of the 4.2 ka event in both spatial and temporal domains is still much less clear in Southern Hemisphere. This is particularly the case for the southwest sector of the southern Indian Ocean. Here we present high-resolution and chronologically well-constrained speleothem oxygen and carbon isotopes records of hydroclimate variability between ~ 6 and 3 ka ago from Rodrigues Island, located in the southwest subtropical Indian Ocean, ~ 600 km east of Mauritius. Our records reveal a major shift to drier condition at circa 4 ka BP, which culminated into a multicentennial period of drought (i.e., megadrought) that lasted continuously from ~ 3.9 to 3.5 ka BP. The inferred hydroclimatic conditions between 4.0 and 4.2 ka BP, are however not distinctly distinguishable from the region’s mean hydroclimatic state over the length of our record. Because the precipitation variability at Rodrigues is distinctly modulated by meridional movement of the Inter-Tropical Convergence Zone and the El Nino Southern Oscillation dynamics, our proxy data may ultimately provide critical constraints in our understanding the timing and dynamical forcing of the 4.2 ka event.

Neoglacial climate anomalies and the Harappan metamorphosis

“…Aridification after ca. 4200 years ago in a series of sensitive records from southern East Africa to Australia (Berke et al, 2012;de Boer et al, 2014;Denniston et al, 2013;Li et al, 2018;Russell et al, 2003;Schefuss et al, 2011;Wurtzel et al, 2018) argue for a narrowing of the ITCZ migration belt during ENA within and around the Indian Ocean domain (Li et al, 2018).…”

Fossil leaf wax hydrogen isotopes reveal variability of Atlantic and Mediterranean climate forcing on the southeast Iberian Peninsula between 6000 to 3000 cal. BP

“…Such a first evidence of climate related collapses or transformations in ancient societies have promoted intense investigations of the "climatic" 4.2 ka BP event, which resulted in a variety of associated paleoclimatic studies from the Mediterranean area [6,7,11,12], Asia [13][14][15], North America [16], the northern North Atlantic region [17][18][19], and the southern hemisphere as well [20,21]. Altogether, paleoclimatic studies point to a series of climatic anomalies between 4400 and 3800 cal.…”