Combination of insolation and ice-sheet forcing drive enhanced humidity in northern subtropical regions during MIS 13

• Main Authors: Oliveira, Dulce, Desprat, Stéphanie, Rodrigues, Teresa, Yin, Qiuzhen, Naughton, Filipa, Trigo, Ricardo M., Su, Qianqian, Grimalt, Joan O., Alonso-García, Montserrat, Voelker, Antje H.L., Abrantes, Fátima, Sánchez Goñi, Maria Fernanda
• Other Authors: Ministerio de Ciencia e Innovación (España)
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2020
• Subjects: Mid-Brunhes event; Interglacial MIS 13; Mediterranean vegetation; Model-data comparison; Insolation; Ice-sheets; Ice Sheet
• Online Access: http://hdl.handle.net/10261/221055; https://doi.org/10.1016/j.quascirev.2020.106573; https://doi.org/10.13039/501100004837

Marine Isotope Stage (MIS) 13, ∼533–478 ka, has received particular attention due to the unexpected enhancement of monsoon systems under a cool climate characterized by lower atmospheric CO2 and larger ice volume than many other interglacials. Key questions remain about its regional expression (intensity, climate variability, length), and underlying forcing factors, in particular at the mid-latitudes. Here we examine the SW Iberian vegetation, terrestrial climate and sea surface temperature (SST) variability during MIS 13 by combining pollen and biomarker data from IODP Site U1385 with climate-model experiments. We show, for the first time, that despite strong precessional forcing, MIS 13 stands out for its large forest expansions with a reduced Mediterranean character alternating with muted forest contractions, indicating that this stage is marked by a cool-temperate climate regime with high levels of humidity. Results of our data-model comparison reveal that MIS 13 orbitally driven SW Iberian climate and vegetation changes are modulated by the relatively strong ice-sheet forcing. We find that the Northern Hemisphere ice-sheets prescribed at the MIS 13 climate optimum reinforce the insolation effect by increasing the tree fraction and both winter and summer precipitation. We propose that the interactions between ice-sheets and major atmospheric circulation systems may have resulted in the persistent influence of the mid-latitude cells over the SW Iberian region, which led to intensified moisture availability and reduced seasonality, and, in turn, to a pronounced expansion of the temperate forest. Financial support was provided by the Portuguese Foundation for Science and Technology (FCT) through the project CLIMHOL (PTDC/AAC-CLI/100157/2008), ULTImATum (IF/01489/2015), SAICT-45-2017-02 projects (WARM WORLDS: 29897 and HOLMODRIVE: 29029), CCMAR FCT Research Unit - project UIDB/04326/2020, D. Oliveira’s contract (CEECIND/02208/2017), F. Naughton’s contract (IF/01489/2015), T. Rodrigues’s contract (WarmWorld- ...