Enhanced climate instability in the North Atlantic and southern Europe during the Last Interglacial

Abstract

Considerable ambiguity remains over the extent and nature of millennial/centennial-scale climate instability during the Last Interglacial (LIG). Here we analyse marine and terrestrial proxies from a deep-sea sediment sequence on the Portuguese Margin and combine results with an intensively dated Italian speleothem record and climate-model experiments. The strongest expression of climate variability occurred during the transitions into and out of the LIG. Our records also document a series of multi-centennial intra-interglacial arid events in southern Europe, coherent with cold water-mass expansions in the North Atlantic. The spatial and temporal fingerprints of these changes indicate a reorganization of ocean surface circulation, consistent with low-intensity disruptions of the Atlantic meridional overturning circulation (AMOC). The amplitude of this LIG variability is greater than that observed in Holocene records. Episodic Greenland ice melt and runoff as a result of excess warmth may have contributed to AMOC weakening and increased climate instability throughout the LIG.

Asynchronous Antarctic and Greenland ice-volume contributions to the last interglacial sea-level highstand

“…Whenever the reconstructed AIS sealevel record falls below −10 m (notably after~119 ka), North American and/or Eurasian ice-sheet growth contributions likely became important. This timing agrees with a surface-ocean change south of Iceland from warm to colder conditions 27 .…”

“…This record suggests (albeit within combined uncertainties) generally lower GrIS contributions than Yau et al 9 , which may agree with results from other modelling studies for GrIS 14,15 . Both the modelling and δ 18 O sw approaches indicate a late GrIS contribution to LIG sea level, which is further supported by wider N. Atlantic and European palaeoclimate data, which reveal that contributions started after 127 ka, while GrIS started to regain net mass from 121 ka 27 .…”

Atlantic Meridional Overturning Circulation and δ13C Variability During the Last Interglacial

“…This suggests possibly large and abrupt variations in ocean ventilation, which challenges the paradigm of the stability of interglacial thermohaline circulation at short timescales (Galaasen et al, ; Hodell et al, ). While the existence of such AMOC change is consistent with some observed climate variability (Bauch et al, ; Galaasen et al, ; Mokeddem et al, ; Tzedakis et al, ; Zhuravleva & Bauch, ), the relationship between benthic δ 13 C and ocean circulation is not straightforward and requires additional tool such as model simulations to evaluate their degree of interactions (Bakker et al, ).…”

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

“…A major and much-discussed example of a potential global "megadrought" and cooling during the Holocene occurred between ca. 4.2 and 3.9 ka cal BP (the 4.2 ka event hereafter) (Weiss, 2015(Weiss, , 2016. One of the best-documented case studies of the occurrence of the 4.2 ka event in the Mediterranean basin comes from the RL4 flowstone from the Renella Cave (Drysdale et al, 2006;Zanchetta et al, 2016).…”