Holocene hydrography evolution in the Alboran Sea: a multi-record and multiproxy comparison

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 and previously published alkenone-SST reconstructions from the same region for both Holocene and glacial period. 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. In contrast, short-term Holocene SST variability is larger in the Mg/Ca-SST than in the alkenone-SST records. It is proposed that larger Mg/Ca-SST variability to be the result of spring season variability, while the smoothed alkenone-SST variability represents average annual temperatures. Mg/Ca-SST record differentiates the Holocene in three periods (1) The warmest SST values occurred during the Early Holocene (11.7 - 9 kyr BP); (2) During the middle Holocene occurred a continuous cooling trend that culminated with the coldest Holocene SST in a double peak structure centred at around 4.2 kyr BP; (3) The Late Holocene (4.2 kyr BP to the present) did not follow any clear cooling/warming trend but millennial-scale oscillations were enhanced. This SST evolution is discussed in the context of changing properties in the Atlantic inflow associated to North Atlantic circulation conditions and also to local hydrographical and atmospheric changes. To conclude, we propose a tight link between North Atlantic circulation patterns and inflow of surface waters into the Mediterranean playing a major role in the controls of Holocene climatic variability of this region.