By Kenneth Hewitt
PAKISTAN has a greater dependence on water from glaciers than any other country in Asia, possibly the world. The good news is that, contrary to common belief, its glaciers are not ‘disappearing’.
The bad news is that glaciers and climate are changing, with major implications for water management. The worst news is that monitoring and understanding of how the glaciers respond to climate change are woefully inadequate.
Since direct sunshine does most of the melting, cloud cover and snowfall are important. A summer storm can shut down melting for many days, causing a huge drop in river flows. Reports suggest increased summer storminess in recent decades. Studies of the Hunza River reveal a marked decline in flows. Since the basin has a 40 per cent ice cover, snowfall has not declined and may have increased, the glaciers are storing ice not disappearing.
Nevertheless, all indications are that climate warming is occurring at high altitudes; but at average temperatures well below zero leading to warmer snow and ice rather than increased melting. Maybe this is why glaciers are expanding in the high Karakoram — warmer ice flows faster. By contrast, climate stations at low elevations like Skardu show a slight cooling in recent decades; more precisely summer cooling and winter warming, but cooler on balance.
It is important not to focus only on total ice cover or annual water yields. Even in drought years, a large part of glacier melt and monsoon rainfall flows to the ocean. The two generally coincide, to create maximum river flows and make the more urgent glacier-related problems about floods not shortage. Meanwhile, water management headaches mostly concern the ‘shoulder seasons’: a few weeks’ or even days’ delay in spring snowmelt, a sudden shutdown or unusual continuation of heavy glacier melt in autumn. This stresses another need; to understand how climate change alters the balance between glacier melt, snowmelt and rainfall, since each responds differently.
Much has been said of the hazards of lakes formed by glacier retreat and that threaten outburst floods. They are important in Nepal but do not apply in Pakistan! The great Indus floods from the Shyok, Shimshal and Karambar ice dams were due to glacier advances and tributary glaciers blocking trunk streams.
If glaciers continue advancing, that is a concern. Attention should be paid to glacier surges: when ice movement suddenly accelerates 10-fold or more, and advances several kilometres in a few months. The UIB has one of the greatest concentrations of surging glaciers. Some threaten communities in the Northern Areas. Since 1987, at least 12 glaciers have surged, more than in any comparable period since records were kept. Climate change is involved but no one knows exactly how.
However, the worst danger, as noted above continues to be the lack of effective monitoring of ice or climate in those critical elevations 3,800-6,500 metres above sea level.
Read More : State of glaciers