Pronounced northward shift of the westerlies during MIS 17 leading to the strong 100-kyr ice age cycles

Goni, Maria Fernanda Sanchez; Ferretti, Patrizia; Polanco-Martinez, Josue M.; Rodrigues, Teresa; Alonso-Garcia, Montserrat; Javier Rodriguez-Tovar, Francisco; Dorador, Javier; Desprat, Stephanie

http://hdl.handle.net/10400.1/14385

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Authors

Goni, Maria Fernanda Sanchez

Ferretti, Patrizia

Polanco-Martinez, Josue M.

Rodrigues, Teresa

Alonso-Garcia, Montserrat

Javier Rodriguez-Tovar, Francisco

Dorador, Javier

Desprat, Stephanie

Abstract(s)

The MIS 17 interglacial, similar to 715-675 ka, marks the end of the Mid-Pleistocene Transition as intensified, long and asymmetrical 100-kyr ice age cycles became eminently established. Increasing arrival of moisture to the Northern Hemisphere high latitudes, resulting from the northwestward migration of the Subpolar Front and the intensification of the Norwegian Greenland Seas (NGS) convection, has been put forward to explain the emergence of this quasi-periodic 100-kyr cycle. However, testing this hypothesis is problematic with the available North Atlantic precipitation data. Here we present new pollen-based quantitative seasonal climate reconstructions from the southwestern Iberian margin that track changes in the position and intensity of the westerlies. Our data compared to changes in North Atlantic deep and surface water conditions show that MIS 17 interglacial was marked by three major changes in the direction and strength of the westerlies tightly linked to oceanographic changes. In particular, we report here for the first time a drastic two-steps northward shift of the westerlies centered at similar to 693 ka that ended up with the sustained precipitation over southern European. This atmospheric reorganization was associated with northwestward migration of the Subpolar Front, strengthening of the NGS deep water formation and cooling of the western North Atlantic region. This finding points to the substantial arrival of moisture to the Northern Hemisphere high latitudes at the time of the decrease in summer energy and insolation contributing to the establishment of strong 100-kyr cycles. (C) 2019 Elsevier B.V. All rights reserved.

Keywords

U1385 Shackleton Site Midpleistocene revolution Climate variability Ocean circulation Iberian margin Storm tracks Atlantic Vegetation Pollen Precession