Links between the Antarctic Oscillation and winter rainfall over western South Africa

Abstract. We established a multi-proxy time series comprising analyses of major elements in bulk sediments, Sr and Nd isotopes and grain size of terrigenous fraction, and δ18O and δ13C in tests of Neogloboquadrina pachyderma (sinistral) from a marine sediment sequence recovered off the Orange River. The records reveal coherent patterns of variability that reflect changes in wind strength, precipitation over the river catchments, and upwelling of cold and nutrient-rich coastal waters off western South Africa. The wettest episode of the Holocene in the Winter Rainfall Zone (WRZ) of South Africa occurred during the "Little Ice Age" (700–100 yr BP). Wet phases were accompanied by strengthened coastal water upwellings, a decrease of Agulhas water leakage into the southern Atlantic, and a reduced dust incursion over Antarctica. A continuous aridification trend in the WRZ and a weakening of the southern Benguela Upwelling System (BUS) between 9000 and 5500 yr BP parallel with increase of dust deposition over Antarctica and an enhanced leakage of warm Agulhas water into the southeastern Atlantic. The temporal relationship between precipitation changes in the WRZ, the thermal state of the coastal surface water, and leakage of warm water in southern Atlantic, and variation of dust incursion over Antarctica suggests a causal link that most likely was related to latitudinal shifts of the Southern Hemisphere westerlies. Our results of the mid-Holocene time interval may serve as an analogue to a possible long-term consequence of the current and future southward shift of the westerlies that may result in a decline of rainfall over southwest Africa and a weakened upwelling with implication for phytoplankton productivity and fish stocks. Furthermore, warming of the coastal surface water as a result of warm Agulhas water incursion into the southern BUS may affect coastal fog formation that is critical as moisture source for the endemic flora of the Namaqualand.

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The Influence of Atmospheric Rivers over the South Atlantic on Winter Rainfall in South Africa

Journal of Hydrometeorology ◽

10.1175/jhm-d-17-0111.1 ◽

2018 ◽

Vol 19 (1) ◽

pp. 127-142 ◽

Cited By ~ 26

Author(s):

R. C. Blamey ◽

A. M. Ramos ◽

R. M. Trigo ◽

R. Tomé ◽

C. J. C. Reason

Keyword(s):

South Africa ◽

South African ◽

Extreme Rainfall ◽

Detection Algorithm ◽

Winter Rainfall ◽

Atmospheric Rivers ◽

The North ◽

Study Support ◽

Topographic Barriers ◽

High Topography

Abstract A climatology of atmospheric rivers (ARs) impinging on the west coast of South Africa (29°–34.5°S) during the austral winter months (April–September) was developed for the period 1979–2014 using an automated detection algorithm and two reanalysis products as input. The two products show relatively good agreement, with 10–15 persistent ARs (lasting 18 h or longer) occurring on average per winter and nearly two-thirds of these systems occurring poleward of 35°S. The relationship between persistent AR activity and winter rainfall is demonstrated using South African Weather Service rainfall data. Most stations positioned in areas of high topography contained the highest percentage of rainfall contributed by persistent ARs, whereas stations downwind, to the east of the major topographic barriers, had the lowest contributions. Extreme rainfall days in the region are also ranked by their magnitude and spatial extent. The results suggest that although persistent ARs are important contributors to heavy rainfall events, they are not necessarily a prerequisite. It is found that around 70% of the top 50 daily winter rainfall extremes in South Africa were in some way linked to ARs (both persistent and nonpersistent). Overall, the findings of this study support similar investigations on ARs in the North Atlantic and North Pacific.

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A Decade Plus of Monoculture Wheat Compared to Wheat/Legume Pastures – Long-term Effects of Management Practices on Some Soil Physicochemical and Microbial Properties in the Winter Rainfall Region of South Africa

International Research in Environment, Geography and Earth Science Vol. 8 ◽

10.9734/bpi/ireges/v8/6243d ◽

2021 ◽

pp. 144-161

Author(s):

A. Marais ◽

M. Booyse ◽

A. Botha

Keyword(s):

South Africa ◽

Management Practices ◽

Long Term Effects ◽

Winter Rainfall ◽

Microbial Properties ◽

Rainfall Region

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Taxonomy and phylogeny of two subgroups of Pelargonium section Otidia (Geraniaceae). 1. The Pelargonium carnosum complex

Bothalia ◽

10.4102/abc.v39i1.231 ◽

2009 ◽

Vol 39 (1) ◽

pp. 73-85 ◽

Cited By ~ 2

Author(s):

M. Becker ◽

F. Albers

Keyword(s):

South Africa ◽

Molecular Evidence ◽

Monophyletic Clade ◽

Winter Rainfall ◽

Diagnostic Features ◽

Molecular Analyses ◽

Specific Rank ◽

Complex Distribution

This contribution deals with the taxonomy and phylogeny of the Pelargonium carnosum complex, a group of closely related taxa of Pelargonium L’Hér. section Otidia (Sweet) DC. (Geraniaceae) that is distributed in the winter rainfall area of South Africa. According to molecular analyses via AFLP, P. adriaanii M.Becker F.AIbers, P. carnosum (L.) L’Uér., P. ferulaceum (C'av.) Willd. and P. polycephalum (E.Mey. ex Harv.) R.Knuth form a monophyletic clade. Although hybridization may occur between the taxa, three are assigned to specific rank. The fourth taxon, P. ferulaceum is recognized as a subspecies ot'P carnosum. As is implied from the occurrence of morphological intermediates and partly from molecular evidence,hybridization does not only occur among the taxa in this complex but also involves species closely related to this group (P. panifiorum J.C.Wendl., P. laxum (Sweet) G.Don, P. dasyphyllum R.Knuth). For the taxa in the P. carnosum complex, distribution areas are delineated and diagnostic features that have until now remained obscure, are outlined.

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Spatio‐temporal patterns of rainfall trends and the 2015–2017 drought over the winter rainfall region of South Africa

International Journal of Climatology ◽

10.1002/joc.6768 ◽

2020 ◽

Cited By ~ 2

Author(s):

Piotr Wolski ◽

Stefaan Conradie ◽

Christopher Jack ◽

Mark Tadross

Keyword(s):

South Africa ◽

Temporal Patterns ◽

Winter Rainfall ◽

Rainfall Trends ◽

Spatio Temporal ◽

Rainfall Region

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A tetrapod fauna from within the Devonian Antarctic Circle

Science ◽

10.1126/science.aaq1645 ◽

2018 ◽

Vol 360 (6393) ◽

pp. 1120-1124 ◽

Cited By ~ 9

Author(s):

Robert Gess ◽

Per Erik Ahlberg

Keyword(s):

South Africa ◽

North America ◽

Late Devonian ◽

Body Fossil ◽

The Antarctic

Until now, all known fossils of tetrapods (limbed vertebrates with digits) and near-tetrapods (such asElpistostege,Tiktaalik, andPanderichthys) from the Devonian period have come from localities in tropical to subtropical paleolatitudes. Most are from Laurussia, a continent incorporating Europe, Greenland, and North America, with only one body fossil and one footprint locality from Australia representing the southern supercontinent Gondwana. Here we describe two previously unknown tetrapods from the Late Devonian (late Famennian) Gondwana locality of Waterloo Farm in South Africa, then located within the Antarctic Circle, which demonstrate that Devonian tetrapods were not restricted to warm environments and suggest that they may have been global in distribution.

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