Abstract
Volcanic eruptions provide tests of human and natural system sensitivity to abrupt shocks because their repeated occurrence allows the identification of systematic relationships in the presence of random variability. Here we show a suppression of Nile summer flooding via the radiative and dynamical impacts of explosive volcanism on the African monsoon, using climate model output, ice-core-based volcanic forcing data, Nilometer measurements, and ancient Egyptian writings. We then examine the response of Ptolemaic Egypt (305–30 BCE), one of the best-documented ancient superpowers, to volcanically induced Nile suppression. Eruptions are associated with revolt onset against elite rule, and the cessation of Ptolemaic state warfare with their great rival, the Seleukid Empire. Eruptions are also followed by socioeconomic stress with increased hereditary land sales, and the issuance of priestly decrees to reinforce elite authority. Ptolemaic vulnerability to volcanic eruptions offers a caution for all monsoon-dependent agricultural regions, presently including 70% of world population.
Introduction
The need to adapt to and mitigate the impacts of anthropogenic climate change has revived interest in longstanding but unsettled questions concerning how past climatic changes have influenced human societies1. Egypt provides a unique historical laboratory in which to study social vulnerability and response to abrupt hydroclimatic shocks. As one of the Ancient World’s great “hydraulic civilizations”2, its prosperity was overwhelmingly tied to the annual cycle of Nile summer flooding, with diminished flooding (Nile failure) often associated with major human impacts through its many millennia of recorded history3. Of all Ancient Egyptian history, that of Ptolemaic Egypt (305–30 BCE; Fig. 1a) is most richly furnished with contemporary documentation. As the longest-lived successor to Alexander the Great’s empire, the Ptolemaic state was a major force in the transformative Hellenistic era, a period marked by large-scale conflict but also material and cultural achievement. Ptolemaic Egypt featured one of the largest cities of the Ancient Mediterranean (Alexandria), including the Great Library and Lighthouse, and was a hub for invention, boasting minds such as Euclid and Archimedes. Technological advances such as the saqiya4, a rotary-wheel water-lifting machine documented by the mid-third century BCE, maslin (mixed wheat-barley) cropping, as well as grain storage, acted to mitigate the impacts of the mercurial Nile flood. Families also distributed land in geographically dispersed individual shares to further hedge against the risk of Nile failure, and tailored agricultural decisions to annual flood conditions6. External territories (e.g., Anatolia, Syria) capable of rainfed agriculture also helped buffer the state against Nile failure. The existence of these mitigation and adaptation strategies highlights the importance of managing Nile variability in Ptolemaic Egypt, yet discussion of the impact of hydroclimatic shocks is effectively absent from modern histories of the period.
At ~6825 km, the Nile is among the Earth’s great rivers, fed by rainfall in Africa’s equatorial plateau (mainly via the White Nile) and the Ethiopian Highlands (mainly via the Blue Nile and Atbara rivers)8. Before twentieth century damming, the summer flood, driven primarily by monsoon rainfall in the Ethiopian highlands, began with rising waters observed at Aswan as early as June, peaking from August to September, and largely receding by the end of October, when crop sowing began2. Nile flood suppression from historical eruptions has been little studied, despite Nile failures with severe social impacts coinciding with eruptions su
Explosive eruptions can perturb climate by injecting sulfurous gases into the stratosphere; these gases react to form reflective sulfate aerosols that remain aloft in decreasing concentrations for approximately one to two years11. While most studies of the climatic effects of volcanism have focused on temperature changes, contemporary and historical societies were also vulnerable to hydrological changes12. Hydroclimate is harder to reconstruct and model, but studies are increasingly noting global and regional hydroclimatic impacts from explosive volcanism. Volcanic aerosols influence hydroclimate through multiple mechanisms. Aerosol scattering of solar radiation to space reduces tropospheric temperatures; if lower-tropospheric relative humidities remain unchanged, the mass of water converged by a given wind distribution decreases, and precipitation minus surface evaporation (P-E) is thus reduced21. This thermodynamic effect may represent the principal means by which equatorially symmetric aerosol distributions from tropical eruptions alter P–E15. In addition, extratropical eruptions increase sulfate aerosols on one side of the equator, cool that hemisphere, and may thus alter tropical P–E primarily by changing winds. In particular, a high-latitude energy sink in one hemisphere forces an anomalous Hadley circulation, shifting the intertropical convergence zone (ITCZ) away from that energy sink1. Aerosol cooling of northern high latitudes can thus force a southward shift of northern hemisphere (NH) summer monsoon precipitation, promoting drought in the northern parts of monsoon regions. These energy-budget arguments provide a more fundamental perspective on the controls on tropical rainfall than arguments based on land-ocean temperature contrast because large-scale tropical circulations are driven by horizontal gradients in the total (sensible plus latent) energy input to the atmosphere24. The hypothesis that a decrease in land-ocean temperature contrast will cause monsoon rainfall to weaken has been disproven by the observation that continental monsoon regions are cooler during years of enhanced monsoon precipitation25, and by the fact that monsoon winds weaken as land-ocean temperature contrast strengthens in projections of next-century warming.
Egypt | The Pollution of the Nile River
Source of Pollution
1. Factories
There are about 700 facilities manufacturing a variety different products located along the Nile river. Some of these facilities dump chemicals into the Nile, while others’ runoff finds its way to the water.
Some of the chemicals that find their way into the river would be phosphors, nitrogen, and pesticide residue. Once dumped, these chemicals can have negative affects on the microorganisms living in the water, by increasing the population of unhealthy bacteria by 50%-180%
2. Food Industry
Studies show that more then 350 different factories discharge their waste in to the Nile. The majority of these factories are involved in the food industry.
The Nile is suffering from the amount of agricultural waste that’s being dumped into the river. The waste is full of toxic chemicals like detergents, heavy metals, and pesticides. Discharge of oil and grease can come from untreated domestic waste water. Fortunately, those chemicals can be treated and removed from the water, but some like mutagens, and neurotoxins remain unaffected by water treatment.
3. Phosphate
On April 22 2015, an Egyptian military owned barge spilled 500 tons of phosphate in to the Nile.
Phosphate is a mineral that comes from rocks when they are eroding. In small amounts, phosphate is good for water bodies. For example, it can help the growth of plankton and aquatic plants.
But in large amounts, like what was dumped into the Nile, it is very harmful. The mineral can cause a nutrient imbalance in the water, which can damage the aquatic plants and kill them, and can also speed up the aging process of the river.
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