Precession Controls on Climate and Water Isotope Signals in Northern Africa

Shi, Xiaoxu ORCID: https://orcid.org/0000-0001-7793-9639; Werner, Martin ORCID: https://orcid.org/0000-0002-6473-0243; Yang, Hu ORCID: https://orcid.org/0000-0003-2054-2256; Gao, Qinggang ORCID: https://orcid.org/0000-0001-5561-1720; Liu, Jiping ORCID: https://orcid.org/0009-0002-9111-5972; Lohmann, Gerrit ORCID: https://orcid.org/0000-0003-2089-733X. 2025 Precession Controls on Climate and Water Isotope Signals in Northern Africa. Paleoceanography and Paleoclimatology, 40 (1), e2024PA004999. 20, pp. 10.1029/2024PA004999

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Abstract/Summary

Precessional forcing is a key driver of quaternary climate change. Based on 24 experiments covering a full precession cycle, this study explores spatio-temporal variations of both climate and isotope signals in Northern Africa. We find a synchronous phasing of precipitation variations with solar radiation levels and an asynchronous timing of surface air temperature changes across different sub-regions of Northern Africa. Based on daily precipitation, our results reveal earlier onset and withdrawal, as well as a shorter duration of the West Africa summer monsoon (WASM) at minimum precession compared to maximum precession. The onset of the WASM is controlled by the intensity of the Sahara Heat Low, while the monsoon termination is linked to subtropical solar radiation and interhemispheric thermo contrast. Using a novel scale-flux tracing technique, we find that, precipitation during minimum precession is more influenced by evaporation from warmer and more humid regions compared to maximum precession. Additionally, certain inland areas of Northern Africa exhibit positive temporal isotope-precipitation gradients, violating the “amount effect.” This phenomenon mainly occurs during precession phases associated with Green Sahara periods. The isotope composition changes in such places primarily reflect changes in upstream rainfall quantity, rather than changes in local precipitation as is inferred from present day analogs. Conversely, the “amount effect” remains applicable during dry periods in Africa when the Sahara desert is present. This suggests that isotope-based reconstruction of past precipitation variations during Green Sahara periods over Northern Africa needs to be taken with caution.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1029/2024PA004999
ISSN:	2572-4517
Date made live:	03 Feb 2025 10:21 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/538843

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1029/2024PA004999

ISSN:

2572-4517

Date made live:

03 Feb 2025 10:21 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/538843