Snow changes in Asia’s mountains

Hydrate

In a new study led by Philip and published in Nature Climate Change, we have assessed the distribution, importance, and past and future changes of seasonal snowpacks across all major river basins in High Mountain Asia.

We found that the amount of snowmelt surpasses that of glacier melt for all river basins, and is mostly three to five times as large. Changes to the region’s snowpacks due to climate change therefore have potentially stronger impacts on the water balance than retreat of its glaciers.

Over the past 40 years there have been significant reductions in snowpacks in several of HMA’s river basins, e.g. Syr Darya, Indus and Brahmaputra (Fig. 1). This has resulted in shifts in timing of the snowmelt seasons and attenuation of snowmelt discharge peaks.

Figure 1: Basin-aggregated trends in snow water equivalent (SWE) for all major river basins in HMA. The size of the bars show the trend in percentage, while the color indicated absolute changes in mm water equivalent per year.

If we are able to limit temperature rise by the end of the century to 1.5 °C, we project region-wide reductions in snowmelt of only 6%. In stabilization scenario SSP2−4.5, snowmelt will reduce by 22% and for specific regions by even more than 50%. The worst-case SSP5-8.5 scenario would result in a region-wide loss of over 40%. Sensitivity of snowmelt changes are thus strongly dependent on the degree of climate change (Fig. 2). There is really something to gain for people downstream from limiting future climate change in terms of future snow meltwater supply.

Figure 2: Projected losses in snowmelt in the end of century for different CMIP6 climate scenarios.

Differences in end of century glacier meltwater output between climate scenarios are much smaller. This is due to specific dynamics under each scenario related to the timing of “peak water”, the point in the future where glacier discharge will peak. Nevertheless, we will lose a considerable amount of HMA glacier mass and meltwater. Percentagewise even more than snowmelt. But since there is much more snowmelt to begin with, the overall impacts of snow changes on HMA hydrology will likely be larger.

Of course, snow and glacier change are only a part of the water puzzle. Climate change acts on other fronts as well, many of which affect water supply from the mountains. On the other side there are changing water demands to consider due to socioeconomic developments.

Interested in our snow study?

  • Access a free-to-read version of the paper here
  • Watch the video in which Philip explains about this study and the Pan-TPE project:

Kraaijenbrink, P. D. A., Stigter, E. E., Yao, T., and Immerzeel, W. W. (2021). Climate change decisive for Asia’s snow meltwater supply. Nat. Clim. Chang., 1–7. doi:10.1038/s41558-021-01074-x.

The post Snow changes in Asia’s mountains appeared first on Mountain Hydrology.

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