Rapid Climate Changes in the Westernmost Mediterranean (Alboran Sea) Over the Last 35 kyr: New Insights From Four Lipid Paleothermometers (U~(K') _(37), TEX~H _(86), RI-OH', and LDI)

摘要

The westernmost Mediterranean is one of the most sensitive areas to global climate change and high sedimentation rates allow recording high frequency variability. We present a high-resolution paleotemperature reconstruction over the last 35 kyr using, for the first time, four independent organic sea surface temperature (SST) proxies (U~(K') _(37), TEX~H _(86), RI-OH' and LDI) based on alkenones, (hydroxy) isoprenoid GDGTs, and long-chain diols. We also generated a δ~(18)O of planktonic foraminifera G. bulloides record together with records of bulk parameters (total organic carbon content, δ~(13)C_(org)) and the accumulation rates of different biomarkers to provide insights into terrestrial input and primary producers. All derived-SST records showed similar trends over the last 35 kyr, revealing abrupt temperature variations during the last seven Dansgaard- Oeschger (D/O) cycles, the three Heinrich (H) events, the Last Glacial Maximum, and the Younger Dryas. H_3 is recognized as the coldest event, while H1 was recorded by all SST proxies as the most abrupt one. In general, TEX~H _(86)-, RI-OH'- and LDI-SST estimates were lower than those obtained from U~(K') _(37). The LDI paleothermometer recorded the largest range of absolute SSTs over the whole period (ca. 20°C) followed by RI-OH' (ca. 16°C). TEX~H _(86), RI-OH' and LDI proxies reflected sudden SST changes during the D/O 6 and 5 particularly well. Low BIT values and the abundance of C_(32) 1,15-diol in range with typical marine values indicated only minor input of continental organic matter. Accumulation rates of different lipid biomarkers were generally modulated by D/O cycles, suggesting enhanced productivity during D/O interstadials and the B?lling- Aller?d period.