Экстремальные осадки лишь временно замедляют таяние ледников в Гималаях, но не останавливают их долгосрочное сокращение

Extreme precipitation events can temporarily slow glacier loss in the western Himalaya by boosting snowfall and accumulation, but they do not alter the region’s long-term trend of ice decline, a study based on five decades of observations has found. Published in Global and Planetary Change, the study analysed 182 glacier-wide, in situ mass balance observations from 26 glaciers across Ladakh, Jammu & Kashmir, Himachal Pradesh and upper Uttarakhand between 1974 and 2023. The researchers from the National Centre for Polar and Ocean Research, Goa, and the Indian Institute of Tropical Meteorology, Pune, recorded a cumulative mass loss of around 26 ± 1.67 metres water equivalent over the period. The findings underline the sustained deterioration of glacier mass despite occasional years of heavy snowfall. How do extreme precipitation events affect glaciers? The study found that years with a higher number of extreme precipitation events generally had less negative, and in some cases positive, glacier mass balances. Such events can produce substantial snowfall, particularly at high elevations, increasing snow accumulation and temporarily countering seasonal ice loss. The number of extreme precipitation events varied between zero and five a year during the study period. Statistical analysis found a moderate positive relationship between extreme precipitation events and glacier mass balance in the same year, with a correlation of 0.33. The effect did not last, however. The relationship weakened sharply in the following year and disappeared thereafter, suggesting that the gains from extreme snowfall were temporary. Why does it matter whether precipitation falls as snow or rain? The study found that the impact of extreme precipitation depends substantially on the season and the form in which precipitation reaches the glaciers. Winter extreme precipitation events are more likely to bring snowfall at high elevations. This adds to glacier accumulation and can improve mass balance. During warmer months, however, precipitation is more likely to fall as rain. Instead of adding to the snowpack, such rainfall can contribute to melting and worsen glacier mass balance. The researchers cited 1975 as an example of how extreme precipitation can influence glacier conditions. Frequent extreme events that year contributed to a positive mass balance of 0.5 metres water equivalent. High precipitation did not have the same effect in years such as 1995 and 2001. Most of the extreme events in those years occurred during summer and produced liquid precipitation, which intensified melting. What drives most extreme precipitation events? Western disturbances emerged as the dominant source of extreme precipitation in the western Himalaya, accounting for about 60.2% of the events identified in the study. The Indian summer monsoon accounted for 16.4%, cyclogenesis systems for 6.3%, and interactions between western disturbances and cyclogenesis for 4.6%. Other synoptic systems accounted for the remaining roughly 12%. The dominance of western disturbances is important because they occur largely during the colder season. At high elevations, precipitation during this period is more likely to fall as snow, increasing accumulation on glaciers. The study therefore links the frequency and intensity of extreme precipitation events to the wider atmospheric systems that supply moisture to the western Himalaya. Is extreme snowfall enough to reverse glacier loss? The researchers found that temperature remains the stronger long term control on glacier mass balance. While extreme precipitation can explain some year to year fluctuations and temporarily reduce glacier losses, warming has a stronger negative association with mass balance. Rising temperatures increase melting and ablation, maintaining the broader trend of ice loss. The study found that extreme precipitation can therefore produce occasional positive or less negative mass balance years, but the overall trend remains persistent ice loss. The findings indicate that intense snowfall can temporarily counter seasonal glacier loss, but cannot compensate for the longer term effects of warming and enhanced melting associated with climate change. Discover the latest Business News, Sensex, and Nifty updates. Obtain Personal Finance insights, tax queries, and expert opinions on Moneycontrol or download the Moneycontrol App to stay updated! Find the best of Al News in one place, specially curated for you every weekend. Stay on top of the latest tech trends and biggest startup news.