When Glaciers Start to Speed Up
Glaciers are curious features on our planet. Masses of ice somehow unevenly distributed over all continents, with some uniform features many tens of kilometers in length, other just blobs hanging on a steep head-wall shaded from the sun. How they work and why they change is something that isn’t known since very long and many aspects of it are still big topics of debate in the scientific community. And among all these glaciers some are especially strange — those that repeatedly speed up their flow velocity and advance quickly into lower regions. They are generally referred to as surging glaciers and many different ways of surging exist.
A recent article in the Science Magazine provides great graphics and descriptions of how such surges work, using recent extreme examples as visualizations.
However these surging glaciers often confuse people not familiar with glacier dynamics. The glaciers seem to grow, rather than what glaciers in times of a warming climate normally do, to recede. But surging glaciers generally still loose mass, they just quickly transport ice from higher up to lower down, thus elongating the tongue but decreasing the ice thickness, and hence the overall mass. Then there are also other glacier processes that move ice rapidly — and here even the specialists disagree on what to call a surge and what not.
It becomes even more complicated in the Karakoram and Kunlun Mountain ranges, where overall glacier mass is relatively stable, i.e. the overall mass change each year is nearly zero or sometimes even positive, and these areas also have a really high density of surging glaciers. Tricky business for us scientists, tricky business if you want to correctly communicate to the public what is happening in High Mountain Asia as a response to a changing climate (see a recent article from our group on the topic below).
Recently we monitored a surge in the Karakoram, that resulted in a lake forming in the valley below that eventually broke and caused floods downstream. Here these advancing tongues also pose a natural hazard.
Images from the Planet cubesats allows us to improve our monitoring on two essential levels. First, for the pure research interest, using multiple image pairs that were sometimes available only a few days apart, we could pick up peak velocities of 15–20 meters/day. That is incredibly fast for a glacier that otherwise moves that distance within one year!
In the animation on the left you can see what such a surge looks like, and that within only 4 months. The snaky pattern in the middle of the glacier is typical for these surge type tongues.
Second we could track how the lake is forming over time (you can see on the upper right side of the tongue in the animation just after the glacier makes a strong bend) and when it became so large that it was likely going to break through the ice and flood. Planet images are so high in resolution that we can even track ice floes forming on the surface of the lake, which could be a potential threat as well.
Repeatedly informing our partners on site, we could therefore employ this satellite imagery to directly provide a first assessment of possible risks. Optical images are relatively easy to interpret and training of staff in local agencies in future will hopefully enable them to make this assessment directly. The development of higher resolution imagery that is more and more easily accessible will likely have a significant impact on such opportunities.
Data for these findings was made accessible by the Planet Education and Research Program. Learn more here.
