Half-precession cycles and orbital-scale hydroclimate variability in the low-latitude Atlantic over the past 1.3 million years: connecting oceanic and continental records.

Over the past 1.3 million years, about forty glacial-interglacial cycles occurred, linked to orbital-scale variability. In tropical regions, short-term periodicities such as half-precession (HP) cycles (~12–8 kyr) offer insights into tropical responses to abrupt climate shifts and the interplay between orbital and millennial-scale events. Yet, their expression remains unclear due to limited long-term tropical records. We present a new inorganic geochemical record from ODP Site 663 (1°N, Gulf of Guinea) spanning ~1.3 million years. We aim to detect HP cycles and understand the possible drivers and their hydroclimate effects on the continent. Preliminary results suggest enhanced aeolian input during glacial periods, likely driven by Sahara expansion and intensified Harmattan winds. In contrast, interglacials show increased fluvial input probably driven by a northward migration of the Intertropical Convergence Zone and an intensified West African Monsoon. Spectral analyses reveal that HP cycles are mainly expressed during interglacials with high planetary eccentricity. These intervals also coincide with the highest recurrence of millennial-scale events, suggesting a modulation of tropical hydroclimate by orbital-scale insolation forcing. Our findings emphasize the role of tropical processes in modulating millennial-scale climate variability, a mechanism traditionally attributed to high-latitude dynamics. Our findings align with HP signals in Lake Bosumtwi (Ghana) between ~650–550 ka BP (MIS 13–11) and hydroclimate variability during MIS 5 in Lake Petén Itzá, Fúquene, and Chalco. Together, these records underscore the critical role of low-latitude processes in shaping global climate variability and offer new perspectives on tropical hydroclimate mechanisms across glacial-interglacial timescales.