Not only does the dust of the Aralkum Desert left in place of the Aral endanger residents, it also can accelerate the melting of glaciers and thus exacerbate the water crisis in the region
Abandoned boats rusting away in the sand at the once blooming sea port of Moynaq, Uzbekistan. Photo: iStock The Aral Sea, the world’s fourth-largest lake until the early 1960s, dried up after that decade in Soviet Central Asia and became a byword for environmental disaster later, almost on the lines of the Chernobyl nuclear disaster.
Now, a new study has found that the desert which emerged due to the drying up of the lake, has made Central Asia a much dustier place. Not only is the dust more hazardous than normal dust but it will also have impacts on global climate, though more studies are needed to ascertain that.
“The drying up of the Aral Sea has made Central Asia dustier by 7 per cent over the past 30 years. Between 1985 and 2015, dust emissions from the growing desert almost doubled from 14 to 27 million tonnes. This is the result of a study by the Leibniz Institute for Tropospheric Research (TROPOS) and Freie Universität Berlin,” noted a statement by TROPOS on April 17, 2024.
It added that the amounts of dust have probably been underestimated so far because two-thirds are stirred up under cloudy skies and therefore go unnoticed by traditional satellite observations.
“The dust not only endangers residents in the region, but also affects air quality in the capitals of Tajikistan and Turkmenistan. In addition, it can accelerate the melting of glaciers and thus exacerbate the water crisis in the region,” according to the statement.
The research has been released at the ongoing Second Central Asian DUst Conference (CADUC-2). It began on April 15 in Nukus, Uzbekistan, on the former Aral Sea and will end on April 22, Earth Day.
The Aral was fed by the two great rivers of Central Asia — the Amu Darya (Oxus in Antiquity) and the Syr Darya (Jaxartes) — flowing from the Pamir and Tien Shan mountain ranges of High Asia, respectively.
Read Sea that isn't
“Due to the excessive use of rivers to irrigate agriculture, less and less water entered the lake. As a result, huge areas dried up, the lake shrunk to a fraction and the vast majority became a desert,” the statement noted.
The Aralkum Desert, which came up in place of the Aral, has an area of 60,000 square kilometres. While significantly smaller than the neighbouring natural deserts of Karakum (350,000 square kilometres) in the south of Turkmenistan and Kyzylkum (300,000 square kilometres) in the southeast of Uzbekistan and Kazakhstan. The Aralkum is, nevertheless, one of the most important human-made dust sources on earth, according to the statement.
More importantly, its dust is much more dangerous as it contains residues of fertilisers and pesticides from former agriculture.
The TROPOS and FU Berlin team of researchers aimed to estimate the effects of dust from the Aralkum Desert. They used the atmospheric dust model COSMO-MUSCAT, which simulates emissions, concentration in the atmosphere and radiation effects of dust particles.
They found that while agricultural areas on the Syr Darya are negatively affected by the dust, it can even be felt in the large cities of Central Asia such as Asgabat (capital of Turkmenistan) and Dushanbe (capital of Tajikistan), more than 800 kilometres away.
On the ground, the dust cools down during the day because it dims sunlight, and warms up at night because it re-emits the heat radiation from the ground.
“The net radiative effect of dust can therefore be cooling or warming, depending on the amount of dust in the atmosphere, the time of day, the season, the surface albedo, and the precise mineralogical and optical properties of the dust,” the statement said.
‘Albedo’ is the fraction of sunlight emitted by a body or a surface.
“Looking at the changes between the past and the present, the near doubling of dust emissions over the Aral Sea/Aralkum region has led to an increase in both radiative cooling and radiative heating at the surface and in the atmosphere,” lead author Jamie Banks said.
Banks added though that these “new” dust events do not occur throughout the year, but in episodes in June, September, November, December and March:
On an annual average, the Aralkum dust probably cools both on the surface and in the atmosphere, but only minimally at -0.05 ±0.51 watts per square metre.
The researchers also found evidence that the dust could change the overall weather patterns. It increases the air pressure on the ground in the Aral region by up to +0.76 Pascal on the monthly time scale. This means an intensification of the Siberian high in winter and a weakening of the Central Asian warm low in summer.
The Siberian High is a massive collection of cold dry air that accumulates in the northeastern part of Eurasia from November until February.
“Since many questions about the climate effects of the dust are still unanswered, the researchers recommend investigating the optical properties of this dust in more detail,” according to the statement.
The Aral Sea is not the only such ‘dust bowl’ in West and Central Asia. Lake Urmia in Iran and Lake Hamoun on the Iran-Afghanistan border have also dramatically shrunk in the last few decades and become strong local sources of dust.
“This desertification therefore has a major impact on the climate and living conditions of the people in the region. Accordingly, there is great interest among international scientists in gaining a better understanding of these processes in order to be able to better assess future trends, including the global climate,” the statement said.
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