Rainfall regime changes and trends in Botswana Kalahari Transect’s late summer precipitation

Mphale, Kgakgamatso; Dash, S. K.; Adedoyin, Akintayo; Panda, Subrat Kumar

doi:10.1007/s00704-013-0907-z

Cited by 11 publications

(9 citation statements)

References 46 publications

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“…The post-1980 CE period represents the most persistent dry conditions across Botswana since 1950 CE [3]. This is also patent in the isotope proxy records for the last 255 years (Figure 3, Figure 6).…”

Section: Resultsmentioning

confidence: 55%

“…The area of the Kalahari Desert from which this tree was sampled is sparsely populated and local rainfall records are rare. We made use of published rainfall records from Tshane, located 115 km north of the sampling site, and Tsabong, located 115 km south of the site [3]. The rainfall from these two sites was averaged to account for the localized variability in convective rainfall in southern Africa [11].…”

Section: Resultsmentioning

confidence: 99%

“…The transition seems to take place in about 1980 CE. In an analysis of instrumental rainfall records across Botswana, Mphale et al [3] also noted a breakdown in the relationship between SST and rainfall and between ENSO and rainfall. These authors identified the date threshold for this change as 1982 CE, and attributed it to an eastward shift of the main rainfall bearing synoptic system that led to a significant reduction in rainfall at this time.…”

Section: Resultsmentioning

confidence: 99%

“…A persistent threat to this economy is rainfall variability, and although the region experiences substantial droughts, the instrumental rainfall records that might elucidate the underlying forcing are generally of short duration. Attempts to understand wet/dry cycles in Botswana, for example, have relied on records as short as 30- [2] to 50- [3,4] years. Despite the poor instrumental records there is strong evidence for the role of the El Niño Southern Oscillation (ENSO) in mediating droughts [5], but the relationship is not linear.…”

Section: Introductionmentioning

confidence: 99%

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A 250-Year Isotopic Proxy Rainfall Record from Southern Botswana

Woodborne¹,

Hall²,

Jones³

et al. 2018

Studia UBB Chemia

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Climate records along aridity gradients where manifestations of climate change are most profound are important for testing climate models. The Kalahari Transect spans such a gradient, but instrumental records of climate parameters are limited in the sparsely populated region. We analysed the δ 13 C and δ 18 O record from a Vachellia erioloba (E.Mey) tree from the southern Kalahari Desert in Botswana to explore its potential as a climate proxy archive. Radiocarbon dates show that the record spans the period 1758-2013 CE. Both the δ 13 C and δ 18 O records correlate with local rainfall. The isotope proxies show a weak positive correlation with sea-surface temperature reconstruction from the southwestern Indian Ocean, and a stronger correlation with the El Niño Southern Oscillation index. This appears to contradict previous evidence that higher sea-surface temperatures are associated with reduced summer rainfall over the southern African interior. Instead of eastward shifts in the temperate tropical trough synoptic system during elevated southwestern Indian Ocean temperature anomalies, the evidence supports a westwards shift. The result demonstrates the potential of Vachellia erioloba as a climate proxy archive that may yield past climate variability from the arid regions of southern Africa.

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Section: Resultsmentioning

confidence: 55%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A 250-Year Isotopic Proxy Rainfall Record from Southern Botswana

Woodborne¹,

Hall²,

Jones³

et al. 2018

Studia UBB Chemia

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“…It is thus likely, that flooding in the southwestern Kalahari during that episode is connected to an enhanced tropical easterly circulation and an associated increase in convective storm cells. Convective storm cells are known for their intense, short-lived character in the Kalahari during austral summer (Mphale et al, 2014). In addition to their short duration, convective storm cells are typically less than a few km in diameter (Reid and Frostick, 2011).…”

Section: Paleoenvironmental Interpretationmentioning

confidence: 99%

Fluvial landscape development in the southwestern Kalahari during the Holocene – Chronology and provenance of fluvial deposits in the Molopo Canyon

et al. 2017

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The Southern Kalahari Drainage network is in a key position to analyze spatiotemporal changes in the tropical easterly and the temperate westerly circulation over the Southern African subcontinent. However, due to the prevailing aridity, paleoenvironmental archives within the southwestern Kalahari are sparse and often discontinuous. Hence, little is known about Holocene environmental change in this region. This study focuses on reconstructing paleoenvironmental change from the timing and provenance of fluvial deposits located within the Molopo Canyon, which connects the Southern Kalahari Drainage to the perennial flow regime of the Orange River. To gain insight into temporal aspects of fluvial morphodynamics within the Molopo Canyon, the entire variety of fluvial landforms consisting mainly of slope sediments, alluvial fans and alluvial fills were dated using Optically Stimulated Luminescence (OSL). We additionally applied a provenance analysis on alluvial fill deposits to estimate potential sediment source areas. Source areas were identified by analyzing the elemental and mineralogical composition of tributaries and eolian deposits throughout the course of the lower Molopo. The results allow the first general classification of fluvial landscape development into three temporally distinct deposition phases in the southern Kalahari: (1) A phase of canyon aggradation associated with short lived and spatially restricted flash floods during the early to mid-Holocene; (2) A phase of fan aggradation indicating a decrease in flood intensities during the mid-to late Holocene; (3) A phase of canyon aggradation caused by the occurrence of supraregional flood events during the Little Ice Age. We interpret the observed spatiotemporal deposition patterns to latitudinal shifts of the tropical easterly circulation in the early to mid-Holocene and the temperate westerly circulation in the late Holocene. However, despite marked changes in the provenance and timing of fluvial deposits in the Molopo Canyon throughout the Holocene, our analysis did not detect a contribution of sediments originating from the Kalahari interior to the deposition of alluvial fills. These results suggest that the Southern Kalahari drainage remained endorheic and therefore disconnected from the Orange River throughout the Holocene.

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