期刊
CLIMATE OF THE PAST
卷 18, 期 11, 页码 2509-2521出版社
COPERNICUS GESELLSCHAFT MBH
DOI: 10.5194/cp-18-2509-2022
关键词
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资金
- Netherlands Organisation for Scientific Research (NWO)
- SCANALOGUE project
- Netherlands Earth System Science Centre (NESSC) [ALWOP.2015.113]
- Dutch Ministry of Education, Culture and Science (OCW) [024.002.001]
- Australian Research Council (ARC)
- Australian Laureate Fellowship [DE1900100042, LE160100067]
- [FL1201000050]
- [DP200101157]
- [DP200100765]
- Australian Research Council [DP200100765] Funding Source: Australian Research Council
The Ti/Al ratio in eastern Mediterranean sediments can provide valuable records of North African climate changes. X-ray fluorescence core scanning (XRF-CS) is an effective method for generating continuous Ti/Al records, but accurate calibration is crucial. By analyzing a long sediment record, we observed a direct control of low-latitude insolation on North African aridity and humidity, with a subdued relationship after the mid-Pleistocene transition (MPT).
In eastern Mediterranean sediments, the titanium-to-aluminum ratio (Ti/Al) captures relative variability in eolian to river-derived material and predominantly integrates climate signals over the Saharan and Sahel regions. Long Ti/Al time series can, therefore, provide valuable records of North African humidity and aridity changes. X-ray fluorescence core scanning (XRF-CS) can generate near-continuous Ti/Al records with relatively modest effort and in an acceptable amount of time, provided that accurate Ti/Al values are acquired. Calibration of raw XRF-CS data to those of established analytical methods is an important pathway for obtaining the required accuracy. We assess how to obtain reliable XRF-CS Ti/Al calibration by using different calibration reference sample sets for a long sediment record from ODP Site 967 (eastern Mediterranean Sea). The accuracy of reference concentrations and the number of reference samples are important for reliable calibration. Our continuous Ti/Al record allows detailed time series analysis over the past 3 Myr. Near-direct control of low-latitude insolation on the timing and amplitude of North African aridity and humidity is observed from 3 to similar to 1.2 Ma. In our Ti/Al record, most arid North African intervals (i.e., with the longest period and highest amplitude) occur after the mid-Pleistocene transition (MPT similar to 1.2-0.7 Ma), when ice ages intensified. We also observe a subdued relationship between low-latitude insolation and North African climate after the MPT. These findings support the growing consensus that African climate became more sensitive to remote high-latitude climate when a threshold ice volume was reached during the MPT.
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