Age determination and sea surface temperature reconstruction from marine and lake records, Iberian Peninsula

Selected multi-proxy and accurately dated marine and terrestrial records covering the past 2000 years in the Iberian Peninsula (IP) facilitated a comprehensive regional paleoclimate reconstruction for the Medieval Climate Anomaly (MCA: 900-1300 AD). The sequences enabled an integrated approach to land-sea comparisons and, despite local differences and some minor chronological inconsistencies, presented clear evidence that the MCA was a dry period in the Mediterranean IP. It was a period characterized by decreased lake levels, more xerophytic and heliophytic vegetation, a low frequency of floods, major Saharan eolian fluxes, and less fluvial input to marine basins. In contrast, reconstruction based on sequences from the Atlantic Ocean side of the peninsula indicated increased humidity. The data highlight the unique characteristics of the MCA relative to earlier (the Dark Ages, DA: ca. 500-900 years AD) and subsequent (the Little Ice Age, LIA: 1300-1850 years AD) colder periods. The reconstruction supports the hypothesis of Trouet et al. (2009, doi:10.1126/science.1166349), that a persistent positive mode of the North Atlantic Oscillation (NAO) dominated the MCA.

AMS 14C dating points, isotopic compositions, Mg/Ca ratios and sea surface temperatures of sediment cores GeoB10029-4 and GeoB10038-4

Quantifying the spatial and temporal sea surface temperature (SST) and salinity changes of the Indo-Pacific Warm Pool is essential to understand the role of this region in connection with abrupt climate changes particularly during the last deglaciation. In this study we reconstruct SST and seawater d18O of the tropical eastern Indian Ocean for the past 40,000 years from two sediment cores (GeoB 10029-4, 1°30'S, 100°08'E, and GeoB 10038-4, 5°56'S, 103°15'E) retrieved offshore Sumatra. Our results show that annual mean SSTs increased about 2-3 °C at 19,000 years ago and exhibited southern hemisphere-like timing and pattern during the last deglaciation. Our SST records together with other Mg/Ca-based SST reconstructions around Indonesia do not track the monsoon variation since the last glacial period, as recorded by terrestrial monsoon archives. However, the spatial SST heterogeneity might be a result of changing monsoon intensity that shifts either the annual mean SSTs or the seasonality of G. ruber towards the warmer or the cooler season at different locations. Seawater d18O reconstructions north of the equator suggest fresher surface conditions during the last glacial and track the northern high-latitude climate change during the last deglaciation. In contrast, seawater ?18O records south of the equator do not show a significant difference between the last glacial period and the Holocene, and lack Bølling-Allerød and Younger Dryas periods suggestive of additional controls on annual mean surface hydrology in this part of the Indo-Pacific Warm Pool.