Many studies on wastage of Himalayan glaciers have come to the conclusion that Himalayan glaciers are retreating with varying rates of retreat between individual glaciers. This glacial retreat can vary between a few meters to up to 61 m/year. Also, mapping carried out of an area of about 11,000 sq km out of 40,000 sq km of glaciated area revealed that about 13 percent of the area has been lost in the last 4 to 5 decades (Kulkarni & Karyakarte, 2014). In this wastage of Himalayan glaciers or a negative mass balance of Himalayan glaciers that could lead to Himalayan glacial retreat is a major climate change concern.
Also forming part of what is known as the Third Pole, the Himalayas have among the highest concentrations of glaciers in the world with major river catchments forming out of Himalayan glaciers. A majority of the Himalayan rivers are perennial due to melted water from Himalayan glaciers. Geological history however, points towards the impermanence of these water sources due to previous climate change bringing about changes in glacial extent.
Various Observations of the Wastage of Himalayan Glaciers
The Intergovernmental Panel on Climate Change (IPCC) in its Fifth Assessment in 2013 affixed that global warming could lead to a warming scenario of between 1 to 4oC by the late 21st Century. This could have enormous consequences for Himalayan glaciers, especially in terms of wastage of Himalayan glaciers.
The IPCC is also reported to have controversially stated that Himalayan glaciers are receding faster than in any other part of the world and predicted that they would disappear by 2035 if the Earth keeps warming at the current rate. This was followed by a rebuttal by the Ministry of Environment & Forests, GoI that a large mountain glacier would take between 100 to 1000 years to respond to warming. In this clarity is required in the nature of the wastage of Himalayan glaciers to know the state of their mass balance, implying conservation of mass, due to the climate.
Observations of the wastage of Himalayan glaciers are difficult and as such of rate of Himalayan glacier retreat because of the considerable difficulties posed by the high altitudes and the remoteness of the Himalayan region. It is this lack of comprehensive observational data that has led to certain speculations based on in situ observations and simulated projections of climate change. The associations used are usually of well observed glaciers and their working under Euro American climes. This method is inadequate in some site-specific queries can be overlooked such as the impacts on surface albedo by the seasonal cycle of precipitation which can in turn impact the wastage of Himalayan glaciers.
Fujita & Nuimura (2011) in their study ‘Spatially Heterogeneous Wastage of Himalayan Glaciers’ pointed out how as compared to the global mean of the mass balance of glaciers rapid wastage of Himalayan glaciers was observed in the period between the 1970s and the 1990s. However, in the first decade of the 21st Century, similar scales of wastages were observed for both the Himalayas and the global mean of the mass balance of glaciers.
To study the possible effects of climate change, Fujita & Nuimura measured the mass balance and equilibrium-line altitude (ELA) (determining ablation and accumulation of glaciers) of three Himalayan glaciers using an energy mass balance model. Using the latest climate datasets available at the time, air temperature and precipitation were used as variables in their simulations to generate the minimum rms error (rmse) against the area-averaged mass balance. The wastage of Himalayan glaciers was measured using in situ measurements.
The study reported that the wastage of Himalayan glaciers with a negative mass balance was highly variable for the first decade of the 21st Century and is at the levels of the global mean. The study found that the wastage of Himalayan glaciers was normally suppressed in relatively arid areas in the Himalayas while in relatively humid areas, strongly accelerated wastage of Himalayan glaciers was observed.
Precipitation thus plays a huge part with a contrast in the wastage of Himalayan glaciers in humid environments as compared to arid environments. In terms of glacial mass balance, previous research has shown that wastage in the mass balance of glaciers occurs more readily in humid environments than in drier environments. Glaciers existing at lower altitudes due to surface albedo and greater warming are specially affected if the region experiences moderate to high precipitation.
Numerous researchers other than Fujita & Nuimura have also carried out observations of the wastage of Himalayan glaciers, although with differing methodologies and with a variety of sites of study. The Geological Survey of India (GSI) has used as its inventory topographical maps, satellite images and aerial photographs. By 2014, the GSI had mapped about 9,040 glaciers and had covered a total area of 18,528 sq km, which however was an inventory carried out only for the Indian part of the Himalayas including 535 glaciers with about 8,240 sq km of total area covered (Kulkarni & Karyakarte, 2014).
For ascertaining the possible effects of climate change on the wastage of Himalayan glaciers, all glaciers as a whole have not usually been considered in studies. Measurements of mass balance using parameters in practice in field studies have been the norm. Analyzing the period between 1975 and 2011, it was found that an overall wastage of 19±7 m of glacial ice had occurred in the Indian Himalayas. This loss of glacial ice has been significantly accelerating since 1975 in the case of wastage of Himalayan glaciers. The areas of accumulation of numerous glaciers located at low altitudes have been affected by this trend, which is marked by a depleted formation of new ice.
Across the world glaciers are retreating with variable rates, which result from glacial ablation rates that exceed the glacial formation and accretion rates due to precipitation. These point to the relevance of Fujita & Nuimura’s 2011 study, which points out that glaciers are retreating at a faster rate in humid conditions than arid conditions. This means that the accretion rates of glaciers due to precipitation in humid conditions are not enough to prevent glacial ablation rates. This is mainly due to increased warming, and foretells a dim picture of the prospects of the wastage of Himalayan glaciers due to climate change. However, with massively increased warming even glaciers in arid regions and high altitudes might be at a higher risk.