Why glaciers are melting so fast?

ISLAMABAD, Nov 10: Stronger monsoon, indigenous and trans-boundary black carbon deposits on ice and snowfall shifting towards the end of winters are accelerating glacier melting. A new research by the Pakistan Meteorological Department (PMD) has shown why in the last 30 years glaciers had shown rapid recession. “The ice samples collected at the ends of five glaciers were analysed in the laboratory. The results indicate a significant amount of black carbon deposits on the lower surface of the ice,” said Dr Ghulam Rasul, the chief meteorologist with the PMD. He believed that the sources of the black carbon were indigenous and trans-boundary. Dr Rasul explained how heavy carbon particles flew at low elevations along the wind and subsided at the lower parts of the glaciers. Thick layer of black carbon on the ice reduced the surface reflections, said Dr Rasul adding: “Therefore, they absorbs more heat from incoming solar radiation and accelerate the melting process. Effect of the enhanced melting is translated into greater discharge and increased tendency of formation of terminal lakes near the lower end of glaciers.” The PMD also referred to the findings by Chinese scientists from the Institute of Tibet Plateau Research, who had analysed air samples in the Astore valley of Gilgit-Baltistan and found considerable contents of black carbon in the lower atmosphere closer to the glaciers. “They have traced its origin to northern India where steel industry has been emitting variety of pollutants which travel along the wind flow toward Pakistan and form dark fog in the winter.” Dr Rasul explained how the landing of atmospheric black carbon on the snow and ice aggravated the recession of glaciers. Elaborating how heavy rainfall was also contributing to the glacier recessions, he said water samples taken from different heights of the glaciers had showed that monsoon rainfall had been increasingly falling at elevations higher than usual even up to 20,000 feet. Analysing weather data of last 30 years, Dr Rasul added that easterly monsoon winds had gained strength which produced stronger air lifting while facing the mountains. Torrential rains of Jhar Khand (India 2013) and Nowshera (Pakistan 2010) were the examples. “This phenomenon has not only been yielding heavier downpours in mountainous terrains but also increased the extent of monsoon precipitation to higher elevations where glaciers are located. Monsoon rainwater is warmer than ice, melting the snow and ice rapidly. The increasing extent of the summer rainfall to higher elevations will enhance the melting of glaciers besides contributing to flooding through an increased runoff,” he added. This was not all. Another interesting fact which is a matter of concern with the mass balance of glaciers is the visible seasonal shift in snowfall. “Usually in winter, snowfall starts in November and continues till the end of March with its peak accumulation in January. The longer the snow stays on the surface of the glaciers in cooler air the greater amounts of snow will be converted into ice,” the chief meteorologist said. According to the expert, instead of January, maximum snowfall had been pushed toward February. Increasing temperatures in the northern mountains winter length has already shortened on both ends. As temperatures rise above 0 degree centigrade in March, the snow melts away quickly leaving less mass accumulation to the glaciers in the form of ice after conversion. “If this trend continues, the Hindukush-Himalaya-Karakoram glaciers will accumulate less mass,” he said, adding the glaciers were the most sensitive indicators of global warming. The Met Department has been engaged in studying different aspects of climate change affecting glaciated region in association with international organisations such as Everest-K2-CNR, Future Water and the Tokyo University.–Dawn]]>