Combination of insolation and ice-sheet forcing drive enhanced humidity in northern subtropical regions during MIS 13
International audience 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 CO 2 and larger ice volume than many other interglacials. Key questions remain about its r...
Published in: | Quaternary Science Reviews |
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Main Authors: | , , , , , , , , , , , |
Other Authors: | , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
HAL CCSD
2020
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Subjects: | |
Online Access: | https://insu.hal.science/insu-03678686 https://doi.org/10.1016/j.quascirev.2020.106573 |
Summary: | International audience 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 CO 2 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. |
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