Climate-Driven Glacier and Snowpack Changes in the Water Towers of Asia (Invited Presentation)

The high mountain regions of Asia have been highlighted as a critical water resource within and downstream of those mountain systems, and as one of the most vulnerable water towers to climatic change. This is, in part, due to the water storage and supply role of the cryosphere within these mountain settings, and the sensitivity of cryospheric systems to even small changes in climate. Unfortunately, a paucity of in situ climate, glacier, and snow cover data in high mountain Asia (HMA) has hampered significant progress in quantifying the changes in cryospheric systems, the mechanisms driving those changes, and the potential impacts on downstream water resources.

Here, we utilize declassified spy satellite imagery, in combination with modern remote sensing imagery, to quantify glacier volume change over the full Himalayan range over the past half century, and assess the possible mechanisms driving those changes. The results show (1) the rate of glacier mass loss is accelerating over time, (2) accelerating temperature changes in high mountain settings are likely the dominant driving mechanism of glacier change, and (3) trends in snow-covered area are important in the monsoonal Himalaya where surface albedo feedbacks are large. This last point highlights the importance of precipitation phase, timing, and frequency on glacier sensitivity to climatic change. We investigate the spatial patterns in these precipitation statistics using dynamically downscaled climate output at 4 km spatial resolution. Our preliminary results show a complex pattern in precipitation seasonality that depends significantly on elevation and water vapor transport direction. In general, westerly disturbances become progressively important as elevation increases, including in regions traditionally identified as dominated by the summer monsoon. In addition, the relative contribution of large storms to total annual precipitation decreases with increasing elevation. These results demonstrate the spatial complexities in the timing, intensity, and frequency of precipitation in HMA when viewed through a topographic lens, and the resulting spatial complexity in glacier sensitivity to climate across the region.