Impact of glacier loss on annual basin water yields

Abstract

Abstract. We couple a glacier flow model to a simplified landscape model to investigate the effects of glacier dynamics, climate, and vegetation succession on annual basin runoff during glacier retreat. Basin runoff initially increases as water is released from glacier storage but eventually decreases to below preretreat levels due to increases in evapotranspiration and altitudinal losses in precipitation. Peak basin runoff and the time to peak basin runoff are primarily determined by glacier dynamics, with shallow sloping continental glaciers experiencing the largest increases in basin runoff (up to 62 %) and longest time until peak basin runoff (up to 142 years), compared to 14 % and 54 years for steep maritime glaciers subjected to the same rate of climate change. These differences in peak basin runoff and time to peak basin runoff can be characterized by the glacier response time: glaciers with long response times are pushed farther out of equilibrium for a given climate forcing and produce larger variations in basin runoff than glaciers with short response times. After peak basin runoff is reached, vegetation plays an increasingly important role, with basin runoff decreasing considerably faster for heavily vegetated landscapes than for rocky landscapes and ultimately reaching values that are over 50 % lower than preretreat levels. Our results demonstrate that glacier dynamics and landscape evolution should receive roughly equal attention when assessing the impacts of glacier mass loss on water resources.

A Changing Hydrological Regime: Trends in Magnitude and Timing of Glacier Ice Melt and Glacier Runoff in a High Latitude Coastal Watershed

“…On the other hand, a study by Carnahan et al. (2018) identified through glacier flow modeling that glacier dynamics (characterized by glacier response times, linked primarily to climate and slope) and landscape evolution (i.e., vegetation succession after deglaciation) had a roughly equal impact on basin runoff in response to glacier retreat. Together, these findings indicate that peak water is likely to occur at different times in different regions.…”

“…Similarly, Moore et al (2009) identified for Western North America that northern basins with larger glaciers still show increasing runoff while basins with smaller glaciers further south have already passed peak water. On the other hand, a study by Carnahan et al (2018) identified through glacier flow modeling that glacier dynamics (characterized by glacier response times, linked primarily to climate and slope) and landscape evolution (i.e., vegetation succession after deglaciation) had a roughly equal impact on basin runoff in response to glacier retreat. Together, these findings indicate that peak water is likely to occur at different times in different regions.…”