Abstract
Abstract. A new high-resolution deglacial and Holocene sea surface temperature (SST) reconstruction is presented for the Alboran Sea (western Mediterranean), based on Mg∕Ca ratios measured in the planktonic foraminifera Globigerina bulloides. This new record is evaluated by comparison with other Mg∕Ca SST records and previously published alkenone SST reconstructions from the same region for both the Holocene and glacial periods. In all cases there is a high degree of coherence between the different Mg∕Ca SST records but strong discrepancies when compared to the alkenone SST records. We argue that these discrepancies are due to differences in the proxy response during deglaciation which we hypothesize to reflect a resilience strategy of G. bulloides, changing its main growth season, and consequently Mg∕Ca records a shorter deglacial warming than alkenones. In contrast, short-term Holocene SST variability is larger in the Mg∕Ca SST than in the alkenone SST records. We propose that the larger Mg∕Ca SST variability is a result of spring temperatures variability, while the smoothed alkenone SST variability represents averaged annual temperatures. The Mg∕Ca SST record differentiates the Holocene into three periods: (1) the warmest SST values occurred during the Early Holocene (11.7–9 cal. kyr BP), (2) a continuous cooling trend occurred during the Middle Holocene that culminated in the coldest Holocene SST having a double cold peak structure centred at around 4.2 cal. kyr BP, and (3) the Late Holocene (4.2 cal. kyr BP to present) did not follow any clear cooling/warming trend although millennial-scale oscillations were enhanced. This SST evolution is discussed in the context of the changing properties in the Atlantic inflow water associated with North Atlantic circulation conditions and also with local hydrographical and atmospheric changes. We propose that a tight link between North Atlantic circulation patterns and the inflow of surface waters into the Mediterranean played a major role in controlling Holocene climatic variability of this region.
Highlights
Overall, Holocene climate evolution (11.7 cal. kyr BP to present) is considered more stable than during the previous glacial period (115–17.7 cal. kyr BP; Bond et al, 1997; Cacho et al, 1999; Martrat et al, 2014)
It is interesting to note that the presented isotopic records show a strong gradient between the western and eastern Alboran Sea, probably due to strong surface mixing with the underlying Mediterranean waters driven by the two anticyclonic gyres (Tintore et al, 1988; Millot, 1999), supporting the argument that the Atlantic inflow became rapidly modified within the Alboran Sea
The analysis of Mg/Ca sea surface temperature (SST) and the δ18O from the ALB-2 record have allowed the reconstruction of the paleoceanography of the Alboran Sea during the Holocene and its possible interactions with the Atlantic Ocean
Summary
Holocene climate evolution (11.7 cal. kyr BP to present) is considered more stable than during the previous glacial period (115–17.7 cal. kyr BP; Bond et al, 1997; Cacho et al, 1999; Martrat et al, 2014). The western Mediterranean Sea is very sensitive to changes in Atlantic Ocean conditions. These oceanic and atmospheric connections have been welldocumented and described for the last glacial period (Cacho et al, 1999; Moreno et al, 2002; Sierro et al, 2005; Frigola et al, 2008; Toucane et al, 2012) when intense millennial-scale variability occurred that was associated with major changes in the AMOC (the so-called Dansgaard–Oeschger cycles and Heinrich events). Cacho et al, 2001; Frigola et al, 2007; Rodrigo-Gámiz et al, 2011; Ausin et al, 2015; Jalali et al, 2016), unlike the glacial periods, potential connections to the changes that occurred in the North Atlantic Ocean still remain unclear Even though the Holocene climate variability over the western Mediterranean has been extensively studied (i.e. Cacho et al, 2001; Frigola et al, 2007; Rodrigo-Gámiz et al, 2011; Ausin et al, 2015; Jalali et al, 2016), unlike the glacial periods, potential connections to the changes that occurred in the North Atlantic Ocean still remain unclear
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