Today we live in an interglacial period that started about 11,000 years ago. Interglacials occurred alternated with the longer glacial periods. Forecasting the future climatic evolution of the current interglacial period is a great challenge. Therefore it is necessary to determine the evolution of past interglacials and evaluate the response of the different components of the Earth’s climatic system. For a long period, paleoceanographic studies have considered that Marine Isotope Stage (MIS) 11 (400,000 yr ago) is a better analogue of our current status than any other more recent interglacial due to the similar orbital situation.
Following this idea, we reconstruct Sea Surface Temperature (SST) conditions for the MIS 11 and for the Holocene in the Iberian Margin. For this study we use core MD03-2699 retrieved from the Estremadura Spur north of Lisbon at 1850m water depth for the MIS 11, while the Holocene reconstruction is based on two sediment sequences: 1) core MD03-2699 in conjunction with box core PO287-44B; and 2) core D13882, D13902 and box core PO287-26B from the Tagus prodelta off Lisbon, collected at 90m water. SST was estimated from the relative composition of C37 unsaturated alkenones (Uk’37=0.033*SST+0.044; r2= 0.96; n= 370 (Müller et al., 1998).
The results show the Holocene maximum SST was close to 19ºC and occurred between 10.5 and 9.7 ka while MIS 11 record reveals two warm phases: the first with maximum SST close to 18ºC (427 to 412 ka) and a second with temperatures close to 19ºC (407 to 395 ka). Both periods display a SST decrease following the maximum. However, in the case of MIS 11, that decrease was interrupted by the second SST increase along with the sea level high stand at 407ka. This observed parallelism was a pre-condition for further comparison of these two periods in the assessment of MIS 11 as a possible model for the future Holocene evolution. However, the forthcoming climate conditions of the Holocene remain an open question.