Abrupt or gradual? Change point analysis of the late Pleistocene–Holocene climate record from Chew Bahir, southern Ethiopia

Abstract

We used a change point analysis on a late Pleistocene–Holocene lake-sediment record from the Chew Bahir basin in the southern Ethiopian Rift to determine the amplitude and duration of past climate transitions. The most dramatic changes occurred over 240 yr (from ~15,700 to 15,460 yr) during the onset of the African Humid Period (AHP), and over 990 yr (from ~4875 to 3885 yr) during its protracted termination. The AHP was interrupted by a distinct dry period coinciding with the high-latitude Younger Dryas stadial, which had an abrupt onset (less than ~100 yr) at ~13,260 yr and lasted until ~11,730 yr. Wet-dry-wet transitions prior to the AHP may reflect the high-latitude Dansgaard-Oeschger cycles, as indicated by cross-correlation of the potassium record with the NorthGRIP ice core record between ~45–20 ka. These findings may contribute to the debates regarding the amplitude, and duration and mechanisms of past climate transitions, and their possible influence on the development of early modern human cultures.

Classifying past climate change in the Chew Bahir basin, southern Ethiopia, using recurrence quantification analysis

“…We reconstructed climate fluctuations in the Chew Bahir from six short (<17 m) sediment cores (CB01-06), collected along a ~20 km transect from Northwest to Southeast in the basin (Foerster et al, 2012(Foerster et al, , 2015Trauth et al, in 2018) (Fig. 1).…”

“…We used the potassium (K) concentrations of the sediment, determined by micro X-ray fluorescence (μXRF) scanning, as a proxy of aridity (Foerster et al, 2012;Trauth et al, 2015;Foerster et al, 2018). Dynamic time warping (DTW) was employed for aligning the K records from the six cores CB01-06 (Trauth et al, 2018). The composite age model of Trauth et al (2015), based on 32 AMS 14 C ages derived from biogenic carbonate, fossilized charcoal and organic sediment, resulting in a very solid chronology for lake record spanning the last ~45 kyr, was then used to convert composite core depths into ages.…”

“…There are currently ongoing discussions concerning global and regional climate fluctuations that had an effect on human habitats (e.g. Trauth et al, 2007;Foerster et al, 2015;Lamb et al, 2018;Ivory and Russell, 2018;Maley et al, 2018;Garcin et al, 2018;Trauth et al, 2018) and which did not, either because these fluctuations had little or no effect on the African climate (e.g. Timmerman and Friedrich, 2016) or because their effect was buffered by the environmental system (e.g.…”

“…We first used the method on prototypical data in order to assess its performance with typical palaeoclimate transitions. We then performed an RQA on the Late Quaternary climate record from Chew Bahir cores CB01-06 because it provides one of the most detailed records of climate change available from the vicinity of important sites for modern human fossil (Foerster et al, 2012(Foerster et al, , 2015(Foerster et al, , 2018Trauth et al, 2015Trauth et al, , 2018.…”

distantia: an open‐source toolset to quantify dissimilarity between multivariate ecological time‐series

“…DTW evaluates the extent to which one time-series has to be reshaped in order to match another reference time-series. The method is implemented in the R packages 'dtw' (Giorgino 2009) and 'Tsdist' (Mori et al 2016), and has been used to align remote sensing data with different temporal resolutions (Baumann et al 2017), cluster areas with similar temporal dynamics (Suominen 2018), and to correlate stratigraphical data from different sediment cores (Trauth et al 2018).…”