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The Little Ice Age and medieval warming in South Africa
Abstract
The Little Ice Age in South Africa, from around AD 1300 to 1800, and medieval warming, from before 1000 to around 1300, are shown to be distinctive features of the regional climate of the last millennium. The proxy climate record has been constituted from oxygen and carbon isotope and colour density data obtained from a well-dated stalagmite derived from Cold Air Cave in the Makapansgat Valley. The climate of the interior of South Africa was around 1°C cooler in the Little Ice Age and may have been over 3°C higher than at present during the extremes of the medieval warm period. It was variable throughout the millennium, but considerably more so during the warming of the eleventh to thirteenth centuries. Extreme events in the record show distinct teleconnections with similar events in other parts of the world, in both the northern and southern hemispheres. The lowest temperature events recorded during the Little Ice Age in South Africa are coeval with the Maunder and Sporer Minima in solar irradiance. The medieval warming is shown to have coincided with the cosmogenic 10Be and 14C isotopic maxima recorded in tree rings elsewhere in the world during the Medieval Maximum in solar radiation.
... The temperature of the last millennium in southern Africa was characterised by positive anomalies during MWP, after which a variable, unstable and mostly cold climate prevailed during 1300-1850, corresponding to the LIA [90,91]. The temperatures for southern Africa over the last millennium were about 3 • C higher during MWP or about −1 • C lower during LIA, compared to the present day [91]. ...
... The temperature of the last millennium in southern Africa was characterised by positive anomalies during MWP, after which a variable, unstable and mostly cold climate prevailed during 1300-1850, corresponding to the LIA [90,91]. The temperatures for southern Africa over the last millennium were about 3 • C higher during MWP or about −1 • C lower during LIA, compared to the present day [91]. The very cold periods reported by Tyson and Lindsey [90] around 1600 and 1700 CE are replicated in the Chapman archive as years with lower rainfall. ...
... The very cold periods reported by Tyson and Lindsey [90] around 1600 and 1700 CE are replicated in the Chapman archive as years with lower rainfall. Tyson et al. [91] established that LIA had two mainly dry periods in 1300-1500 and 1675-1800 CE, alternating with a warmer period in 1500-1675 CE. Although a long dry period is evinced by the isotopic excursions between 1288 and 1306 CE, the wettest conditions were registered in the time frame 1379-1446. ...
A high-resolution climate archive was reconstructed based on carbon isotope analysis and radiocarbon dating of the Chapman baobab in northeastern Botswana. The Chapman baobab, which exhibited an open ring-shaped structure composed of six stems, collapsed in January 2016 during an intense El Niño event. Two samples belonging to the oldest stems were investigated in order to obtain a proxy rainfall record, which provides insight into the precipitation regime over the last millennium, evincing centennial and decadal scale variability. The results indicate that the Medieval Warm Period was marked by relatively stable precipitation, whereas rainfall variability and drought frequency increased during the Little Ice Age. The investigated area has experienced both wetter and drier conditions in the past. The wettest conditions of the last millennium were registered before 1450 while the driest period occurred in 1835. For southern Africa, inter-annual rainfall variability is mainly associated with sea surface temperatures in the Agulhas Current core region, which determine the east–west displacement of tropical temperate troughs. Previous studies suggested that positive sea surface temperature anomalies in the Mozambique Channel led to an eastward movement of the troughs but the Chapman record demonstrates a westward displacement in the past, causing drought in northeastern South Africa and wetter conditions in the central part of southern Africa. The positive rainfall correlation with SST anomalies reversed after 1900, causing a gradual decrease in precipitation and confirming the current aridity trend for Botswana. The results contribute to a better understanding of the past climate of southern Africa for which paleoclimate reconstructions remain scarce.
... Parkington 1987;Jerardino et al. 2016Jerardino et al. , 2018Rick et al. 2020). Among the latter, is the locally under-studied period known as the Medieval Warm Anomaly (MWA) or Medieval Warm Epoch ( c. 1300-650 calibrated years Before Present [cal BP]), characterised by hot and dry local conditions (Tyson et al. 2000;Chase & Meadows 2007;see below). ...
... The first two Neoglacial events c. 4200 cal BP and between c. 2500 and 1800 cal BP also coincided with atmospheric and sea surface cooling phases which probably brought more rain to the central west coast (Cohen et al. 1992;Compton 2001). The MWA, a warm and dry period, with apparently warmer sea surface temperatures and a~0.5 m sea level highstand followed thereafter around 1300-650 cal BP (or AD 800-1400) (Cohen et al. 1992;Tyson et al. 2000;Compton 2001Compton , 2006Chase & Meadows 2007). MWA would have meant frequent droughts or reduced precipitation in Elands Bay, perhaps similar to current rainfall levels further north in Namaqualand. ...
Spring Cave is situated just below the Baboon Point escarpment in Elands Bay and is one of only a handful of central west coast sites with deposits dating to the Medieval Warm Anomaly (MWA, c. 1300-650 cal BP). This was a climatological period of global significance that brought hot and dry conditions to much of the South African west coast, an ecologically stressed period affecting people, animals and plants alike. Although Spring Cave also dates to before and after the MWA, a large amount of its deposits date to this period. Earlier research on the central west coast has shown that most MWA-dated sites are situated at high elevations and near the coast, and that such placement in the landscape allowed monitoring of the movement of game, predators, and groups of people with or without livestock. High mobility, seeking safety and shelter at higher elevations, and a close watch on the landscape were part of general adaptive strategies, but people at Spring Cave may have added repeated ritual slaughter of small carnivores to the range of coping mechanisms. Doing so, according to ethno-historical records among herding groups, would have brought good luck and well-being. When considering Spring Cave's entire sequence, broad late Holocene regional patterns are also confirmed: i) higher frequencies of exotic lithic raw materials before 3000 cal BP; and ii) greater emphasis on gathering limpets after 2000 BP, while mussels dominate assemblages before then. Moreover, metrical data on limpets, mussels and Cape rock lobster suggest that these species were not processed before their transport back to the cave, an observation at variance with barnacles and fish.
... Paleoclimatic records for the regionbased on oxygen, nitrogen and carbon isotopesshow that the rainfall and temperature varied between AD 900 and the present (e.g., Smith et al. 2007Smith et al. , 2010Woodborne et al. 2015). These isotopic analyses indicate that, during the Little Ice Age (AD 1300-1800; Tyson et al. 2000), there was a ±1.4°C decrease in temperature accompanied by a decrease in rainfall (Woodborne et al. 2015). The SLCA also plays host to several different environment types including woodland in the form of a riparian forest, rocky hills, and grasslands (e.g., Eastwood & Blundell 1999;Plug 2000;Rutherford et al. 2010). ...
Rain-control in the Shashe-Limpopo Confluence Area (SLCA) is one sphere in which hunter-gatherer and farmer interaction is archaeologically visible. One avenue of examining this interaction is through faunal analysis. This paper presents an updated taxa list for one of the identified rain-control sites in the SLCA-Ratho Kroonkop. By identifying the taxa accumulated at Ratho Kroonkop and contextualising them using radiocarbon dates and relevant ethnographies, we were able to determine that particular animals were significant to the people who utilised the location as a rain-control site. Additionally, we were able to establish that this significance continued from the K2 period (AD 1000-1220) to the historic period.
... Post glacial climatic cycles, described above, are stabilized at this time i.e. the last 2000 years, although a hot dry period known as the Medieval Warm Anomaly (MWA) or Medieval Warm Epoch (c. 1300-650 cal BP) does appear to impact local conditions (Tyson et al. 2000;Jerardino et al 2021). Peter Mitchell draws attention to: "El Niño events [that] usefully remind us of the value of situating southern Africa history within a global environmental context" (Mitchell 2017: 46). ...
This research investigates the density and distribution of quartz deposited over an area measuring 70,000m2 at the Kurukop in the Nama Karoo, South Africa. My interest was in the quartz artefacts and a possible relationship with engraved depictions, water features and “rubbed” surface abrasions. To investigate this I used a combination of techniques. These include the GIS capability available in Google Earth Pro, primarily to measure and quantify areas, distances and elevations. To improve resolution and measurement accuracy a composite drone image of the entire site was photographed and imported into the Google Earth application. Quartz samples from two squares (SA1, SA2) were collected, counted and weighed, and this data was intercalated with measurements provided by the aerial map and a detailed ground survey. A number of trends can be observed, indicating that the remains of previous activities probably influenced subsequent decisions.
A rhythmanalysis is applied to the ethnoarchaeological dimensions of the study and from this perspective the production of space at the Kurukop is considered. The conclusion I draw is that the presence of water appears to have influenced the way in which people chose to interact with and mark the site.
Key words: quartz, petroglyphs, landscape, rhythmanalysis, spatial mapping, aerial photography
... For the late Holocene, there is evidence for a neoglacial period at around 2 ka for large parts of the country (Rosen et al., 1999;Holmgren et al., 2003;Scott et al., 2003a;Mulder and Grab, 2009). In addition, multiple studies have suggested that climatic events centred around the North Atlantic may also have manifested in southern Africa, such as the Younger Dryas (Abell and Plug, 2000;Gasse et al., 2008;Chase et al., 2015), the so-called "8.2 ka event" Voarintsoa et al., 2019), the Medieval Climatic Anomaly and the Little Ice Age (Tyson et al., 2000;Norström et al., 2018;Du Plessis et al., 2020;Hahn et al., 2021), although there is some contention at least regarding the Younger Dryas . This paper will examine the palaeoclimate dynamics within the SRZ through the use of quantitative climate reconstructions using published pollen records from across the region. ...
South Africa has a particularly spatially heterogeneous climate driven by a complex set of ocean-atmospheric factors. This results in three distinct regions of rainfall seasonality: the summer-(SRZ), winter-(WRZ) and year-round (YRZ) rainfall zones. Even within these zones there is considerable spatio-temporal variability in precipitation patterns, especially in the SRZ which covers the largest terrestrial area. Over the past several thousand years the position of the boundaries of the southern extent of the SRZ have shifted due to the influences of major climate systems, as well as changes in the characteristics of the adjacent oceanic currents. Here we use the Modern Analogue Technique on a new synthesis of pollen records from across the SRZ to quantitatively reconstruct four climate variables (Mean Temperature of the Coldest month, Mean Temperature of the Warmest Month, Mean Summer Precipitation and Winter Climatic Moisture Index), over the past 36,000 years. The climate variables and number of analogues used were selected after thorough examination of the modern dataset. The results provide evidence for three key features: first, an early deglaciation following a cold, dry and prolonged Last Glacial Maximum. Second, a clear manifestation of the African Humid Period in the northeastern part of the zone, supported by reconstructed sea surface temperatures. And third, a short-lived cold period at around 10 cal kyr BP, which may have been obscured by larger statistical errors in past studies. As it is still mostly within the margin of error for our study, this period requires further study. Our results show that the technique can be used successfully on large and diverse compilations of South African records, improving comparability with other regions.
The subsistence practices of Later Stone Age (LSA) foragers and herders living in Namaqualand South Africa are often difficult to differentiate based on their archaeological signatures but characterizing their dietary choices is vital to understand the economic importance of domesticates. However, ethnohistoric accounts have provided information on the cooking/boiling of marine mammal fat, mutton, plants, and milk by early herders and foragers across the Western Cape. To further investigate these reports, we use lipid residue analysis to characterize 106 potsherds from four open-air LSA sites, spanning in time from the early first millennium to the late second millennium AD. Two sites (SK2005/057A, SK2006/026) are located on the Atlantic coast whereas sites Jakkalsberg K and Jakkalsberg M are located further inland on the southern bank of the Orange River. Notably, at the coastal sites, the presence of marine biomarkers suggests the intensive and/or specialized processing of marine products in many vessels. The dominance of ruminant carcass products at inland sites and probable sheep remains confirms the importance of stockkeeping. Furthermore, and in good agreement with ethnohistoric accounts for its use, our results provide the first direct chemical evidence for the use of dairy products in LSA western South Africa.
Over the last 20 years, developments in climatology have provided an amazing array of explanations for the pattern of world climates. This textbook, first published in 2006, examines the earth's climate systems in light of this incredible growth in data availability, data retrieval systems, and satellite and computer applications. It considers regional climate anomalies, developments in teleconnections, unusual sequences of recent climate change, and human impacts upon the climate system. The physical climate forms the main part of the book, but it also considers social and economic aspects of the global climate system. This textbook has been derived from the authors' extensive experience of teaching climatology and atmospheric science. Each chapter contains an essay by a specialist in the field to enhance the understanding of selected topics. An extensive bibliography is included and lists of websites for further study. This textbook will be invaluable to advanced students of climatology and atmospheric science.
April-August temperatures are reconstructed from maximum latewood density and ring-width data for a tree-line site in the Canadian Rockies of Alberta close to Athabasca Glacier. The chronology primarily utilizes Picea engelmannii with some Abies lasiocarpa snags. This reconstruction (AD 1073-1983) is the longest densitometrically based summer temperature record from boreal North America. Mean temperatures from 1101- 1900 were 0.71°C below the 1961-1990 reference period and 0.33°C below the 1891-1990 mean of the instru mental record. The coldest interval was the first half of the nineteenth century and the major cold intervals, c. 1200-1350, 1690s and the nineteenth century, coincide with local and regional periods of glacier expansion. Warmer periods, c. 1350-1440 and in the present century, are also periods of higher tree-line or tree-line advance at the site. The 1961-1990 reference period is clearly warmer than any equivalent-length period over the last 800 years. This record of summer warmth reinforces evidence of significant warming at several high- altitude and high-latitude sites around the Northern Hemisphere in the late twentieth century. The reconstruction also indicates that glacier advances of the 'Little Ice Age' in the Rockies occurred during a period of fluctuating climatic conditions rather than a long period of sustained cold of several centuries duration.
Southern hemisphere and South African regional air temperature anomalies
for the period 1860-1996 are compared to borehole-derived surface
rock-temperature anomalies to assess the extent to which surface rock
temperatures reflect possible global warming in South Africa. The
warming of the southern hemisphere since the mid-nineteenth century is
evident in the regional air temperatures for South Africa. Following a
temperature increase to a maximum in the 1920s, the climate cooled until
strong warming recommenced in the mid 1970s. Highest temperatures have
been experienced in the 1990s. Borehole-derived surface rock
temperatures followed a similar pattern, but with a lag of a few decades
in the case of the 1920s maximum. The overall warming trend is clearly
evident in the rock temperatures. Despite uncertainties in the different
data sets, an encouraging degree of agreement exists between the
increase in rock temperatures during the twentieth century, the
corresponding regional South African air temperature increase and the
southern hemisphere counterpart.
High-resolution stable isotope variations and growth structure analyses of the last three millennia of a 6600-year stalagmite record at Cold Air Cave, Makapansgat Valley, South Africa, are presented. Growth layers, which are measurable over the last 250 years, are shown to be annual. The correlation between the width of growth layers and precipitation is strongly positive. Changes in&dgr;18O and&dgr;13C are positively correlated and inversely correlated to changes in the colour of the growth layers in the stalagmite. Variations in colour are directly correlated with mean annual temperature. Dark colouration is the product of increased temperature and mobilization of organic matter from the soil, and is associated with wetter summers and enhanced growth of C4 grasses. Darker colouring and enriched&dgr;18O and&dgr;13C reflect a warmer, wetter environment, whereas lighter colouring and depleted isotopic values are indicative of cooler, drier conditions. The dominant episode in the 3000-year record is the cool, dry 500-year manifestation of the‘Little Ice Age’, from ad 1300 to about 1800, with the lowest temperatures at around ad 1700. The four centuries from ad 900 to 1300, experiencing above-average warming and high variability, may be the regional expression of the medieval warming. Other cool, dry spells prevailed from around ad 800 to 900 and from about ad 440 to 520. The most prolonged warm, wet period occurred from ad 40 to 400. Some extreme events are shown to correspond well with similar events determined from the Greenland GISP2 ice-core record and elsewhere. Distinct periodicities occur within the record at around 120, 200–300, 500–600 and at about 800 years BP.
We have re-examined the dust record from the GISP2 ice core retrieved from central Greenland and found that the background dust concentration is modulated with a period of 11 years all the way back to ice from at least 100,000 yrs BP. The only known, relevant, naturally occurring phenomenon with such a period is the well-known solar cycle. We believe that the background modulation we observe is related to the solar cycle and discuss this hypothesis.
We measured stable oxygen isotope ratios and skeletal growth rates in the massive corals Pavona clavus and P. gigantea from the west coast of Isabela Island, Galapagos, to assess interannual to decadal climate variability in the eastern Pacific. Comparisons of instrumental data sets show that sea surface temperatures (SST) in the Galapagos region are representative of a broad portion of the eastern equatorial Pacific. The P. gigantea isotope record is nearly monthly in resolution, spans the period 1961-1982, and shows strong correlation with a Galapagos instrumental SST record. Cross-spectral analysis shows that SST can explain greater than 80% of the variance in δ18O at both the annual cycle and within the high-frequency portion of the ENSO band (3-5 years). The P. clavus record is annual in resolution, extends from 1587 to 1953 A.D., and was obtained from a 10-m diameter colony preserved within the Urvina Bay uplift. The isotopic record appears to be a very good, but not perfect, indicator of ENSO events. The dominant oscillatory modes, both within the ENSO and interdecadal frequency bands, shift to shorter periods from the early to middle 1700s and again from the middle to late 1800s. This may reflect major reorganizations within the tropical ocean-atmosphere system and suggests that tropical Pacific climate variability is linked across timescales ranging from years to decades. -from Authors
Models of southern African palaeoclimate implicate surface atmospheric circulation anoma lies as forcing large-scale changes during the Late Quaternary. The available proxy data are insufficient to test the models since they provide information about temperature and rainfall rather than surface circulation. A conceptual model is proposed which links coastal ocean temperatures with atmospheric circulation and allows a history of surface circulation to be inferred from sea-temperature data. A Holocene sea-surface temperature (SST) record was constructed by measuring the oxygen isotope composition of marine mollusc shells preserved in an archaeological cave deposit on the coast of the eastern Agulhas Bank, southern Africa. Radiocarbon-dating of individual shells allowed definition of the timing and timespan of events in the record. By serially sampling along the growth axis of each shell, information was obtained about intra-annual variability as well as millennial-scale trends. During the early Holocene, the sea surface on the eastern Agulhas Bank was colder than it is at present. Maximum summer and winter temperatures obtained 5800 years ago, exceeding by more than 2°C those recorded in the region today during non-El Nino years. On average, temperatures remained high for the following 1500 years but dropped again during the Late Holocene. At 650 BP, at the start of the 'Little Ice Age' in southern Africa, the surface waters on the eastern Agulhas Bank were colder during both winter and summer.
Until recently, relatively little was known of the exact nature of climatic change in southern Africa over the past two millennia. New research based on oxygen isotope analyses of cave speleothems and mollusc remains in shell middens, together with foraminifera studies of inshore marine deposits, palynological and micromammalian research and earlier dendrochronological work, has allowed more reliable identification of the effects of the 'Little Ice Age' in the subcontinent. Cooling prevailed from 1300 to 1850 with a warm episode occurring between about 1500 and 1675. In addition, the generally warmer period from about 900 to 1300 may have been associated with the Medieval Warm Epoch. Earlier distinctive events appear to have been a variable period of cooling from 600 to 900, a warmer period from about AD 250 to 600 and a notable interval of cooling between AD 100 and 200.
Much of the evidence for the 'Little Ice Age' in southern Africa suggests that in the summer rainfall region drier conditions prevailed during the period of cooling. At the same time the winter rainfall region became wetter. This supports a previous postulation that as the tropical easterlies of the general circulation of the atmosphere strengthen and become more perturbed over southern Africa over extended periods, so the climate becomes wetter over the summer rainfall area. As the circumpolar westerlies strengthen and expand northward, so the summer rainfall region becomes drier, while the coastal Mediterranean winter rainfall region becomes wetter.
The coincidence between the Maunder Minimum of solar magnetic activity from 1645 to 1715 and the coldest temperatures of the Little Ice Age raises the question of possible solar forcing of the Earth's climate. Using a correlation which we find between measured total solar irradiance (corrected for sunspot effects) and a Ca II surrogate for bright magnetic features, we estimate the Sun's radiative output in the absence of such features to be 1365.43 W/m2, or 0.15% below its mean value of 1367.54 W/m2 measured during the period 1980 to 1986 by the ACRIM experiment. Observations of extant solar-type stars suggest that the Ca II surrogate was darker during the Maunder Minimum. Allowing for this, we estimate the total solar irradiance to be 1364.28 W/m2 or 0.24% below its mean value for the 1980 to 1986 period. The decrease in the global equilibrium temperature of the Earth due to a decrease of 0.24% in total solar irradiance lies in the range from 0.2°C to 0.6°C, which can be compared with the approximately 1°C cooling experienced during the Little Ice Age, relative to the present.
The most prominent Holocene climatic event in Greenland ice-core proxies, with approximately half the amplitude of the Younger Dryas, occurred ˜8000 to 8400 yr ago. This Holocene event affected regions well beyond the North Atlantic basin, as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane. Widespread proxy records from the tropics to the north polar regions show a short-lived cool, dry, or windy event of similar age. The spatial pattern of terrestrial and marine changes is similar to that of the Younger Dryas event, suggesting a role for North Atlantic thermohaline circulation. Possible forcings identified thus far for this Holocene event are small, consistent with recent model results indicating high sensitivity and strong linkages in the climatic system.
The climatic history over South Africa during the past few centuries is modelled by mathematical inversion of perturbations in temperature profiles measured in boreholes drilled in solid rock. Preliminary investigation reveals that 19th and 20th century rapid warming of the ground surface commenced about 170 years ago and that on average surface temperatures have increased by 1.1K since then in comparison to the 0.8K rise observed in global air temperatures over land since the mid-18th century. Lowest temperatures derived from the South African borehole temperature data set were reached around 1790 in the last phase of the Little Ice Age when mean conditions were 0.3K cooler than in preceding centuries. The model is shown to have considerable potential for determining regional magnitudes and gradients of climatic change in the period before meteorological records. It may even be possible to resolve changes in climate earlier than the Little Ice Age in South Africa if temperature data from deep boreholes become available.