Forecasting temperate alpine glacier survival from accumulation zone observations

Abstract

Abstract.Temperate alpine glacier survival is dependent on the consistent presence of an accumulation zone. Frequent low accumulation area ratio values, below 30%, indicate the lack of a consistent accumulation zone, which leads to substantial thinning of the glacier in the accumulation zone. This thinning is often evident from substantial marginal recession, emergence of new rock outcrops and surface elevation decline in the accumulation zone. In the North Cascades 9 of the 12 examined glaciers exhibit characteristics of substantial accumulation zone thinning; marginal recession or emergent bedrock areas in the accumulation zone. The longitudinal profile thinning factor, f , which is a measure of the ratio of thinning in the accumulation zone to that at the terminus, is above 0.6 for all glaciers exhibiting accumulation zone thinning characteristics. The ratio of accumulation zone thinning to cumulative mass balance is above 0.5 for glacier experiencing substantial accumulation zone thinning. Without a consistent accumulation zone these glaciers are forecast not to survive the current climate or future additional warming. The results vary considerably with adjacent glaciers having a different survival forecast. This emphasizes the danger of extrapolating survival from one glacier to the next.

Changes in the southeast Vatnajökull ice cap, Iceland, between ~ 1890 and 2010

“…Glaciers in Iceland experienced among the most negative mass balance worldwide in the early 21st century (Vaughan et al, 2013;Gardner et al, 2013). In this time period increased surface lowering on the southeast outlets of Vatnajökull is evidenced in emerging rock outcrops and expansion of nunataks up to an elevation of approximately 1200 m. A pattern of increased downwasting in the accumulation areas in recent years has been observed in Alaska (Cox and March, 2004), the Alps (Paul et al, 2004), North Cascade glaciers (Pelto, 2010), and Svalbard (James et al, 2012).…”

“…10). The outlets terminating in overdeepened basins seem to lose mass by thinning rather than retreat, as has been shown to be the retreat pattern ), Eyjafjallajökull 1998), Snaefellsjökull 1999-2008), and Hofsjökull 1995-2010 is presented with dotted lines in (b). The two latest time periods of Langjökull (1997Langjökull ( -2002Langjökull ( and 2002Langjökull ( -2010 are based on surface mass balance measurements (data base Glaciological group Institute of Earth Sciences, University of Iceland).…”

“…Wise, 2000). The appearance of nunataks was used to determine ice surface elevation changes in the accumulation area of the southeast outlets, as has been done to estimate downwasting elsewhere (Paul et al, 2007;Rivera et al, 2007;Pelto, 2010). The aerial images were laid on top of and georeferenced with a shaded relief lidar image and the outline of the nunataks digitized.…”

Heterogeneity in glacier response in the upper Shyok valley, northeast Karakoram

“…Further, uncertainty may arise due to the fact that the upper glacier boundaries were considered constant in the present study and the adjustments were restricted to the lower part of the glaciers. This approach can be justified because the area changes in the upper glacier parts are usually minor and occur only when there is a significant thinning along with a clear negative mass budget (Pelto, 2010). However, in the case of balanced budgets as true for most of the glaciers in Karakoram (Gardelle et al, , 2013Kääb et al, 2012) insignificant or only very little area changes occur in the accumulation area (Schwitter and Raymond, 1993;Pelto, 2010).…”

Contrasted surface mass balances of debris-free glaciers observed between the southern and the inner parts of the Everest region (2007–15)

“…Indeed lowmaximum-elevation glaciers, such as Pokalde or Changri Nup Glacier, experience ablation over the entire surface area with low-albedo bare ice exposed to their highest elevations and the accumulation zone reduced almost to zero in some years (Table 3). These glaciers are imbalanced with the present climate as their accumulation area is too reduced to regenerate the glacier (Pelto, 2010), and the albedo feedback on MB is strong leading to extremely negative MBs. On the other hand, Mera Glacier is located high enough to always accumulate snow, even during (Fig.…”