Streamflow response to the rapid retreat of a lake‐calving glacier

Abstract

There has been increasing attention over the last decade to the potential effects of glacier retreat on downstream discharge and aquatic habitat. This study focused on streamflow variability downstream of Bridge Glacier in the southern Coast Mountains of BC between 1979 and 2014, prior to and during a period in which the glacier experienced enhanced calving and rapid retreat across a lake‐filled basin. Here we combined empirical trend detection and a conceptual‐parametric hydrological model to address the following hypotheses: (1) streamflow trends in late summer and early autumn should reflect the opposing influences of climatic warming (which would tend to increase unit‐area meltwater production) and the reduction in glacier area (which would tend to reduce the total volume of meltwater generated), and (2) winter streamflow should increase because of displacement of lake water as ice flows past the grounding line and calves into the lake basin. In relation to the first hypothesis, we found no significant trends in monthly discharge during summer. However, applying regression analysis to account for air temperature and precipitation variations, weak but statistically significant negative trends were detected for August and melt season discharge. The HBV‐EC model was applied using time‐varying glacier cover, as derived from Landsat imagery. Relative to simulations based on constant glacier extent, model results indicated that glacier recession caused a decline in mean monthly streamflow of 9% in August and 11% in September. These declines in late‐summer streamflow are consistent with the results from our empirical analysis. The second hypothesis is supported by the finding of positive trends for December, January, and February discharge. Despite the modelled declines in late‐summer mean monthly streamflow, recorded discharge data exhibited neither positive nor negative trends during the melt season, suggesting that Bridge Glacier may currently be at or close to the point of peak water. Further analysis of the impact of lake‐terminating glaciers on downstream discharge is needed to refine the peak water model. Copyright © 2016 John Wiley & Sons, Ltd.

Impact of glacier loss and vegetation succession on annual basin runoff

“…the formation of proglacial lakes will accelerate retreat (Larsen et al, 2007;Moyer et al, 2016) and modify basin evapotranspiration rates; and supraglacial debris in regions with highly erodible rock insulates glacier ice and thereby slows the rate of glacier retreat (Frans et al, 2016;Anderson and Anderson, 2016;Kienholz et al, 2017);…”

“…(1) with a depth-integrated glacier flow model and a simplified landscape model. The use of a dynamic glacier model has been shown to give more accurate results for the glacier melt contribution to runoff than static models of glacier ice (Naz et al, 2014). We assume that the precipitation and mass balance rates depend on elevation and that the evapotranspiration rates are a function of time since deglaciation.…”

Cascading risks to the deterioration in cryospheric functions and services

“…Huss 和 Hock [11] 进一 步将全球冰雪水资源影响区划分为 56 个流域, 分别研究 了过去和未来至 2100 年冰雪融水的变化. 结果发现当前 已有近一半的流域过了"拐点", 而尚未出现拐点的流域通 常是大冰川覆盖区 [12] ; 对冰川储量和径流预估结果表明: [14,20~22] 和北美洲 [23,24] 均将呈减小趋势, 其中下降最大的是亚洲腹地和安第斯山 [25,26] . 预估未来积雪融水短缺风险主要分布于美国 内华达山脉、落基山脉等美国西部山区, 欧洲的比利牛斯 山、欧亚交界处的爱琴海地区、亚美尼亚高地、黎巴嫩及 其争议地区, 拖鲁斯山脉, 扎格罗斯山脉, 亚洲的帕米尔 高原, 兴都库什、青藏高原、喜马拉雅山等地区以及非洲 的大阿特拉斯山 [27] .…”

Robust Adaptation Research in High Mountains: Integrating the Scientific, Social, and Ecological Dimensions of Glacio-Hydrological Change

“…Reductions in glacier area drive a non-linear response in glacial meltwater generation known as peak water. Peak water suggests that enhanced energy fluxes from the atmosphere to glacier surfaces will increase meltwater generation until a discharge peak is reached; increased melt will then cause discharge to decrease as glacier area declines, ending at a discharge level less than pre-climate forcing values, e.g., [20]. Peak water will have important implications for human populations and ecosystems that depend on glacially sourced water [5,21].…”