Introduction | Case study 1 | Case study 2 | Summary
What is glacial surging?
Glacial surging refers to the sudden movement of ice over a relatively short period of time resulting in rapid glacier advance that is different from the usual glacier activity 1. Examples of surging can be found across the world, e.g. on Gilkey Glacier, Alaska, where periods of downwasting and stagnation are followed by rapid glacier velocity and advancing (see Figure 1 for an illustration of surge activity).
FUN FACT: The Karakoram region of the Himalaya has the highest concentration of surging glaciers than anywhere in the world 6.
Why is surging considered a hazard?
Generally, our understanding of surge activity is limited, and a lot of surge activity goes unnoticed, with surge activity often being identified by a series of characteristic landforms.
Surging rarely poses a direct hazard to humans because of the relatively rare occurrence, and the fact most of these glaciers are located far from human infrastructure 3.
Where surging does directly impact humans, damage is generally limited, for instance following surging of the Belvedere glacier in 2001, a number of trails were damaged and lifts closed 3. For the most part, action can often be taken to avoid major surge-related disasters (see Case Study 1).
Case Study 1: Glacial surging and the Trans Alaska Pipeline System
Background information
The Trans Alaska Pipeline System (TAPS) crosses three mountain ranges as well as numerous rivers on its journey from the northern coast to the marine terminal in the south. Due to the mountainous terrain, TAPS also crosses paths with several surging glaciers (e.g. Black Rapids Glacier) along its journey, particularly in the Alaska Range (Figure 2), posing a hazard to the system. Not only is there a possibility for glaciers to directly contact the pipeline (with two occurrences over the last 3400 years), flooding from dammed lakes could also impact the system.
Mitigation
As a result, weekly helicopter surveillance is conducted across the TAPS corridor, and streamflow is monitored across the length of the corridor, along with ground surveys and monitoring of aerial imagery 3
Far more common however, is the indirect hazard caused by flooding as a result of surge activity.
Surging glaciers can suddenly release stored subglacial waters during advancing, causing flash floods. But they are also responsible for forming ice-dammed lakes.
When surging glaciers advance across river valleys they form temporary ice-dammed lakes 4. Once formed, the volume of these ice-dammed lakes rises rapidly, often in a matter of days or weeks. Once the water pressure in the lake increases enough, flotation of the ice dam is triggered and the dammed water is released causing flooding 3,5.
Flooding caused by glacial surging has led to devastation in downstream communities across the world, from the 1934 Glacier Grande del Nevado Del Plomo flood that killed more than 60 people, to the 2017 Khurdopin valley flood that caused considerable damage to houses, bridges, roads and farmlands (see Case Study 2).
Case Study 2: Glacial surging of Kyagar glacier
Background information
One glacier found in the Karakoram, the Kyagar glacier, has produced more than 30 recorded outburst floods due by surge activity between 1880 and present day. The advancing glacier blocks the flow of the Yarkant River and as a result, large ice-dammed glacial lakes form (Figure 3) 4. These lakes subsequently burst, generating GLOFs with volumes that have exceeded 40 million m3.
Implications
Past outbursts have resulted in widespread implications e.g. fatalities, infrastructural damage, loss of livelihoods and huge economic damage. For example, the 1961 outburst resulted in more than 7 deaths, loss of 124 houses, and inundation of 700ha of croplands 7, whilst subsequent outburst in 1997 and 1999 resulted in 12.5 M$ and 25 M$ worth of damage each! 8.
Summary
In summary, surging glaciers can have implications for nearby human populations, and as such can be classed as ‘glacial hazards’. While surge dynamics are still relatively understudied, as climates warm and glacier thermal regimes change it may become more important to understand surge activity if disasters are to be avoided.