Whether it be at the poles or high altitudes, glaciers the world over are responding to hotter temperatures, retreating at rates that can be terrifyingly fast. The great anomaly to this pattern, the Karakoram range, now has a possible explanation.
The stability, and sometimes even growth, of the glaciers of the Karakoram is more than an intriguing puzzle. The Karakoram mountains, at the point where Pakistan, India and China meet, provides much of the water for the Indus River, on which most of the population of Pakistan depends. Precipitation falling on these mountains will inevitably reach these rivers eventually, but glaciation means the water is released at a controlled rate, rather than a boom-bust cycle of flood and dry.
Many of the Karakoram glaciers are covered in rubble, and one previous theory runs that this may have had an insulating effect.
For climate change deniers, the Karakoram anomaly outweighs the evidence of ice decline in the Arctic, Antarctic and the rest of the world's high mountains, including the majority of the Himalayas. An inaccurate prediction on glacial decline in the region was the one significant error in the 3,000 page Intergovernmental Panel on Climate Change fourth assessment report.
In Nature Geoscience, Princeton University's Dr. Sarah Kapnick pins the blame on seasonal weather patterns. She points out that most of the Himalayas experience heavy summer rain as a result of the south Asian monsoon, and this far outweighs the winter snows. In Karakoram the situation is reversed, with cold winter winds from Central Asia bearing most of the precipitation. The monsoon seldom reaches Karakoram, usually being blocked by the Great Himalayan Range to the south.
Modeling the effects of climate change on this snowfall is complicated by the area's extreme topography – including K2, the world's second highest mountain and three others over 8,000 meters. Past efforts have used average altitudes for the region, but Kapnick replaced these with high-resolution maps and monthly precipitation data.
Kapnick found that, even with some warming, the higher slopes of the mountains were too cold in the summer to melt the glaciers, and there is no reason to expect average snowfalls to decrease. Consequently, she predicts snowmass to stay stable or increase above 4,500 meters until 2100, offsetting declines at lower altitudes.
While this is great news for Pakistan, Kapnick does not believe her findings are applicable to the rest of the Himalayas, already experiencing sharp glacial declines. “Something that climate scientists always have to keep in mind is that models are useful for certain types of questions and not necessarily for other types of questions. While the IPCC models can be particularly useful for other parts of the world, you need a higher resolution for this area."