From Romania to Kazakhstan, summer droughts linked to less winter ice in two rapidly warming seas
Scientists show direct link between winter ice cover in Barents and Kara seas and summer drought in eastern Europe and central Asia
This summer, with its scarce rainfall and repeated heatwaves, witnessed one of the most severe droughts in European history since 1540. The resulting wildfires across western Europe received considerable media attention, but eastern Europe was also heavily hit, worsening the humanitarian crisis caused by the war in Ukraine. Simulations have shown that such droughts are bound to become more frequent and severe in the future due to man-made global warming.
But what if such droughts could be predicted in advance? This would make it possible to take timely mitigating action. Exploring whether winter sea ice cover might offer an early clue to summer drought risk was the goal of a new study in Frontiers in Water.
"Here we show evidence of a directional, mechanistic link from reduced winter sea ice in the Barents and Kara Seas, in the Arctic, to more summer drought across a wide area of Eurasia, stretching from eastern Romania, Moldova and Ukraine, across the northern Black Sea and Caspian regions, into western Kazakhstan,” said lead author Dr Petru C Vaideanu, a scientist at the Centre of Excellence for Climate and Societal Changes at the University of Bucharest, Romania.
“If we have a winter with much less sea ice than usual, we have an early clue that drought is more likely in these regions the following summer."
Fastest warming seas on Earth
The researchers focused on the Barents and Kara Seas to look for a link with drought, because these waters have seen some of the Arctic’s steepest declines in winter sea ice since the 1980s. Unless measures are taken to reduce CO2 emissions, IPCC simulations project that by the end of this century, sea surface temperatures there could increase by 4°C to 5°C. This rapid warming is due to several interacting factors, including warmer Atlantic water entering the region, local feedbacks involving shrinking sea ice, changes in clouds, and other atmospheric processes.
Vaideanu and colleagues from the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research in Bremerhaven, Germany, retrieved historic records of sea ice in these waters from October through March. They used ERA5, a database from the European Centre for Medium-Range Weather Forecasts, which combines observations with a weather model to estimate monthly averages for atmospheric conditions across Eurasia from 1940 onwards. They calculated drought conditions separately, using records of precipitation and estimates of potential evapotranspiration. They then looked for areas with unusually dry conditions from May through September, reflecting less-than-average rainfall or greater atmospheric demand for moisture.
The authors took care to adjust for the long-term rise in atmospheric CO2 concentrations. This was important, as both sea ice cover and summer drought are known to change in response to the resulting warming of the climate, which could drive a spurious correlation between them.
With techniques borrowed from applied physics and economics, the authors found evidence that this discovery went beyond a mere association: rather, a reduction in winter sea ice is likely an important driver of summer drought.
Planetary waves
But how can a decline in Arctic sea ice lead to droughts thousands of kilometers away? Here, the researchers found an atmospheric pattern consistent with a possible role for Rossby or planetary waves, whose behavior is shaped in part by Earth’s rotation.
“Rossby waves appear as broad north–south bends, thousands of kilometers across, in the winds high above the Earth. In the northern hemisphere, northward bends called ‘ridges’ often favor warm, dry weather. In our data, winters with less sea ice in the Barents and Kara Seas were followed by a bendier pattern over the North Atlantic and Eurasia, consistent with a possible change in Rossby waves,” explained Vaideanu.
“Such a bendy atmospheric circulation pattern can bring relatively warm, dry air into our newly identified drought corridor in Eurasia and lead to stagnant weather. We also observed fewer clouds there, so more sunlight heats the land, potentially worsening the drought.”
Journal
Frontiers in Water
Method of Research
Data/statistical analysis
Subject of Research
Not applicable
Article Title
Winter Barents–Kara sea ice loss preconditions a summer drought corridor across eastern Europe and Eurasia
Article Publication Date
12-Nov-2026
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