A winter without snow

Mountain peaks in the Hindu Kush Himalayan (HKH) region are usually blanketed by snow during the winter. But this winter has been unusual. With little to no snowfall, the peaks are noticeably bare. The central region of high-altitude Hunza valley in northern Pakistan has not seen a single snowflake this winter. In Humla district of northwestern Nepal, Limi valley saw an unusual early snowfall event in late September but has since experienced a lack of precipitation.

In the HKH region, snow typically begins to accumulate around October or November and continues through March. However, temperatures have been warmer than average this season—2023 was the hottest year on record when global mean temperature rise crossed the guardrail of 1.5°C for the first time. This is a likely reason for the below-normal snow cover.

For snow, the region depends on the western disturbance—a meteorological phenomenon that forms over the Mediterranean Sea, Caspian Sea and Black Sea, moves eastwards and crosses Iraq, Iran, Afghanistan and Pakistan before reaching northern and northwestern India and western Nepal. This brings sudden winter rain, sleet and snow to the HKH region.

But this phenomenon is getting disrupted in a fast heating-up world. Although the precise mechanisms are not fully understood, global warming is believed to contribute to prolonged and intense La Nina–El Nino conditions—the warm and cool phases of a recurring climate pattern across the tropical Pacific Ocean that can influence weather patterns across the world, including the western disturbance. In April 2023, when the weather pattern switched to El Nino, after three years of La Nina, it caused marine heatwaves in the Mediterranean, Gulf of Mexico, Indian Ocean, North Pacific and North Atlantic that were experiencing persistently high sea surface temperatures in 2023. This temperature anomaly in 2023 appear to have weakened and delayed the western disturbance, affecting winter precipitation and snowfall in the HKH region.

What we are experiencing is the reality of what 1.5°C means for the HKH region. “Even if there is significant snowfall in February and March as temperatures start to rise, it will probably be too little and too late to make up for the existing deficit,” says Sher Muhammad, cryosphere expert at the International Centre for Integrated Mountain Development (ICIMOD), an intergovernmental organisation.

Cascading impact

The western disturbance serves as the main source of snowfall that nourishes the HKH glaciers, particularly those in the western part of the region. For eastern Himalayan glaciers, summer precipitation is the main source. On average, annual snowmelt contributes 23 per cent of the flow of the 12 major river basins that originate in the HKH region and flow downstream to farmlands and cities, with snowmelt runoff from individual basins varying from 5 to 77 per cent. The combination of seasonal snowmelt and glacial melt thus plays a key role in river hydrology and in daily life downstream.

The extremely dry winter, which follows years of below-average snowpack accumulation, is expected to further strain water resources this spring and summer. “We are worried about the implications for agriculture and our mountain ecosystems,” says Paljor, ward chairperson in Halji village in Humla district of Nepal. Majority of people in this Himalayan district are farmers. “Winters are being pushed later into spring. This means that we may see snowfall in April or May, or no snowfall in some years. These changes could lead to drought, severely affecting agriculture and drinking water supplies in the region,” Zarina Baig, a climate researcher and resident of Pakistan’s Hunza valley.

“While an exceptionally dry winter is a big challenge, heavy snowfall in spring could be an even bigger challenge as it could bring catastrophes like avalanches and flash floods. Urgent action is required to build the resilience of Himalayan communities in the face of snow drought and its cascading impacts,” says Arun Shrestha, senior climate change specialist at ICIMOD.

Snow cover also helps regulate temperature of the earth’s surface. Variations in snow cover can affect regional weather patterns. Cooling associated with moist spring soils and a heavy snowpack in Eurasia is believed to shift arrival of the summer monsoon season and influence its strength and duration. This is another reason why heavy spring snow does not augur well for the region.

While data gap is a major concern for the HKH region, it has become paramount to make the most of existing data and expedite uptake of adaptive measures to mitigate the future risks. Understanding what drives the western disturbance and how it is changing are key to predicting the snowfall. The information can be used to forecast potential impact on water availability and associated risks in the highlands and downstream areas. There is also an urgent need for advancing the science of monitoring the influence of the western disturbance on snowfall in the region, as the topic is not well understood particularly among decision makers. In a changing climate, it is crucial that the science and decision-making processes move parallel.

Arshini Saikia is atmospheric scientist at the International Centre for Integrated Mountain Development or ICIMOD. Chimi Seldon is communications officer at ICIMOD

This was first published in the 16-29 February, 2024 print edition of Down To Earth

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