Interacting drivers of Holocene climate change in southwestern Africa: the influence of insolation, rainbelt dynamics and upwelling

Understanding regional-scale patterns of long-term climate variability is essential for identifying the drivers of past environmental change. In southern Africa, the continent is often divided into three rainfall zones—summer, winter, and aseasonal—but this framework fails to capture the finer dynamics of transitional areas where tropical, subtropical, and temperate systems converge. This study examines Holocene climate variability along the western margin of the southern African monsoon region using a new 7,300-year nitrogen isotope record from rock hyrax middens at Omanyne-4 in northern Namibia. Unlike other Namib Desert records that indicate progressive aridification through the Holocene, the Omanyne-4 sequence shows a long-term trend toward increasing humidity, consistent with insolation-driven enhancement of tropical and Indian Ocean moisture advection. Comparisons with records from northern Namibia, Botswana, and western Zambia reveal a coherent pattern of mid- to late Holocene humidification across the northwestern interior, in contrast to coastal aridification. Periods of both in-phase and antiphase variability with other regional records highlight the role of the Angola–Benguela Front and associated upwelling dynamics in modulating Namibian hydroclimate. These results delineate distinct Holocene climate response regions in northern Namibia and Botswana and demonstrate the non-linear nature of regional responses to insolation forcing and underscore the importance of coastal–inland atmospheric interactions in shaping long-term hydroclimate variability in southwestern Africa. • New 7.3 kyr hyrax midden δ 15 N record from northern Namibia presented. • Northern Namibia shows long-term humidification, contrasting coastal aridification. • Holocene climate response is distinct from other regions in SW Africa. • Variability linked to shifts in the South Atlantic Anticyclone and rainbelt. • Results clarify antiphase trends in Holocene southern African climate zones.