A continuous, centennial-scale lake record from southern Iberia captures fluctuations in effective moisture and temperature throughout the EemianMarta

Abstract

<p>The Eemian (~130 to 115 ka yr BP), also called Marine Isotope Stage (MIS) 5 or the Last Interglacial, was the most recent interglacial period prior to the Holocene. Since temperatures during the Eemian were, on average, ~2 °C warmer than today, studies of this period offer insights into how variables like effective moisture may change under near-future warming scenarios. Such information could improve climate projections for drought-prone regions like the Mediterranean that are particularly vulnerable to future warming. Therefore, a study was initiated to investigate carbonate-rich, Eemian-aged sediments from Padul Wetland (southern Iberia), a site which contains one of the oldest (>200 ka yr) continuous sediment records in the Mediterranean. The resulting proxy record includes stable isotope (<em>δ</em><sup>13</sup>C and <em>δ</em><sup>18</sup>O) and clumped isotope (Δ<sub>47</sub>) compositions of aquatic gastropods (<em>e.g., Radix balthica</em>, <em>Anisus spirorbis</em>) and bivalves (<em>e.g., Pisidium </em>sp.). An age-depth model for the entire 200 000-year record was previously established using a mixture of 43 Accelerator Mass Spectrometry (AMS) radiocarbon dates, 10 Amino Acid Racemization (AAR) dates from gastropods (<em>hydrobiid Milesiana schuelei</em>), and two different sediment accumulation rates (SAR) for peat and carbonate/marl lithologies. Variations in <em>δ</em><sup>18</sup>O and <em>δ</em><sup>13</sup>C closely correspond with<em> </em>the Pollen Climate Index (PCI) for Padul, which is used to discriminate between cold/arid and warm/humid conditions. The close resemblance of these records suggests that variations in <em>δ</em><sup>18</sup>O and <em>δ</em><sup>13</sup>C at Padul are also sensitive to moisture changes. Variations in <em>δ</em><sup>18</sup>O and <em>δ</em><sup>13</sup>C of shelly fauna at Padul also resemble<em> </em>shifts in <em>δ</em><sup>18</sup>O from the NGRIP ice core(Greenland) and alkenone-based marine sea surface temperature (SST) records of the western Mediterranean region. Similarities among these records underscore the sensitivity of Padul Wetland to regional- and global-scale climatic changes as well as more local moisture variations. One measurement of Δ<sub>47</sub> in the aquatic gastropod <em>Radix balthica </em>suggests that average temperatures at Padul during the Eemian were 19.7 ± 2.6 °C, which is consistent with marine records from the Iberian margin. The interpretation of Δ<sub>47 </sub>in <em>Pisidium sp. </em>is more complicated, perhaps due to vital effects or because <em>Pisidium </em>sp. have highly variable lifespans and individuals that lived only a few months may not reflect average annual conditions. In summary, the stable and clumped isotope records generated in this ongoing study build on previous Eemian-aged reconstructions from southern Iberia by providing higher resolution proxy data constrained by quantitative temperature reconstructions. This research deepens our understanding of how effective moisture in southern Iberia may change in the near future.</p>