Unraveling the forcings controlling the magnitude and climate variability of the best orbital analogues for the present interglacial in SW Europe

Oliveira D. Desprat S. Yin, Qiuzhen [UCL] et al.

The suitability of MIS 11c and MIS 19c as analogues of our present interglacial and its natural evolution is still debated. Here we examine the regional expression of the Holocene and its orbital analogues over SW Iberia using a model–data comparison approach. Regional climate based on snapshot and transient experiments using the LOVECLIM model is evaluated against the atmospheric and oceanic climatic records from IODP Site U1385. The pollen-based reconstructions show a larger forest optimum during the Holocene compared to MIS 11c and MIS 19c, putting into question their analogy in SW Europe. Snapshot experiments indicate reduced MIS 11c forest cover compared to the Holocene, primarily driven by lower winter precipitation which is critical for Mediterranean forest development. Decreased precipitation was possibly induced by the amplified MIS 11c latitudinal insolation and temperature gradient. In contrast, the reconstructed lower forest optimum at MIS 19c is not reproduced by the simulations probably due to the lack of Eurasian ice sheets and its related feedbacks in the model. Transient experiments with time-varying insolation and CO2 reveal that the SW Iberian forest dynamics over the interglacials are closely coupled to changes in summer temperature and winter precipitation mainly controlled by precession, CO2 playing a negligible role. Model simulations reproduce the observed persistent suborbital atmospherically-driven vegetation changes in SW Iberia and the dramatic forest reductions marking the end of the interglacial “optimum”. This observation highlights the potential role of the interactions between long-term and millennial-scale climate dynamics in amplifying the climate and vegetation response.