Millennial variability of terrigenous transport to the central–southern Peruvian margin during the last deglaciation (18–13 kyr BP)
Authors: Yseki Marco , Turcq Bruno , Caquineau Sandrine , Salvatteci Renato , Solis José , Skilbeck C. Gregory , Velazco Federico , Gutiérrez Dimitri 
Published: October 2022

Abstract. Reconstructing precipitation and wind from the geological
record could help researchers understand the potential changes in precipitation and
wind dynamics in response to climate change in Peru. The last deglaciation
offers natural experimental conditions to test the response of precipitation and wind
dynamics to high-latitude forcing. While considerable research has
been done to reconstruct precipitation variability during the last
deglaciation in the Atlantic sector of South America, the Pacific sector of
South America has received little attention. This work aims to fill this gap
by reconstructing types of terrigenous transport to the central–southern
Peruvian margin (12 and 14∘ S) during the last
deglaciation (18–13 kyr BP). For this purpose, we used grain-size
distribution in sediments of marine core M77/2-005-3 (Callao,
12∘ S) and core G14 (Pisco, 14∘ S). We analyzed
end-members (EMs) to identify grain-size components and reconstruct
potential sources and transport processes of terrigenous material across
time. We identified four end-members for both Callao and Pisco sediments. In
Callao, we propose that the changes in the contributions of EM4 (101 µm) and EM2 (58 µm) mainly reflect the hydrodynamic energy and diffuse
sources, respectively, while the variations in EM3 (77 µm) and EM1 (11 µm) reflect changes in the eolian and fluvial inputs, respectively. In
Pisco, where there are strong winds and an extensive coastal desert, changes in
the contribution of EM1 (10 µm) reflect changes in river inputs, while
EM2 (52 µm), EM3 (75 µm), and EM4 (94 µm) reflect an eolian
origin. At millennial scale, our record shows an increase in the fluvial
inputs during the last part of Heinrich Stadial 1 (∼16–14.7 kyr BP)
at both locations. This increase was linked to higher precipitation in the Andes
related to a reduction of the Atlantic Meridional Overturning Circulation
and meltwater discharge in the North Atlantic. In contrast, during the
Bølling–Allerød interstadial (∼14.7–13 kyr BP), there was an
eolian input increase, associated with stronger winds and lower
precipitation that indicate an expansion of the South Pacific Subtropical
High. These conditions would correspond to a northern displacement of the
Intertropical Convergence Zone–South Pacific Subtropical High system associated with
a stronger Walker circulation. Our results suggest that variations in river
discharge and changes in surface wind intensity in the western margin of
South America during the last deglaciation were sensitive to Atlantic
Meridional Overturning Circulation variations and the Walker circulation on
millennial timescales. In the context of global warming, large-scale
increases in precipitation and fluvial discharge in the Andes as a result of a
declining Atlantic Meridional Overturning Circulation and southward
displacement of the Intertropical Convergence Zone should be considered.