Antarctica

Melt Water Features on Antarctic Ice Shelves: Ice Dolines

Ice shelves – ice that flows from the ice sheet and floats on the ocean – cover 70% of Antarctica’s coastline and play a crucial role in future sea level rise. These floating portions of ice mediate loss from the grounded portion of the Antarctic Ice Sheet by providing a backwards force on the flow (called buttressing). Once removed, ice in the interior is more free to flow into the ocean and raise sea level. So how resistant ice shelves are to collapse is an critical component of understanding the future effect of an increasingly warm climate.

One particularly worrying aspect of an increasingly warming climate is that it will spur the surface of these glaciers to melt more frequently and in bigger volumes. In Antarctica, this increasingly takes the form of melt ponds and melt lakes on its ice shelves, and the larger volume of melt water features on ice shelves makes it more susceptible to breaking (calving) and eventually collapsing. However, the volume of this melt water in the future is one of the largest uncertainties in projections, and may double in the next 25 years.

“Ice dolines” are meltwater-related feature caused by the rapid drainage of a (typically buried by frozen ice or snow) meltwater lake. Such features may be important for the future stability of sopme ice shelves but have been relatively understudied. Ice dolines are usually characterized by a >10 meter (> 32 feet) depression. What triggers their collapse is still not well understood, by is likely driven by some fracture that drains the melt to the ocean below which may temporarily increase melting of the ice shelf underneath. Additionally, the depression left by the drainage event may allow liquid water to collect in a place on the ice shelf more vulnerable to breaking.

The 50-year observational history of an ice doline on Amery Ice Shelf

In one study, we focus on an ice doline on the Amery Ice Shelf in East Antarctica that abruptly collapsed within several days in 2015. We present one of the first documentations of the long-term history of an ice doline prior to collapse, the circumstances surrounding the collapse, and the evolution post-collapse. To investigate this long-term history and collapse, we leverage multiple remote sensing observations, derived products, and regional climate and tidal models. We will discuss the evolution of the ice doline prior to collapse, the environmental conditions surrounding the collapse and correlate the factors that lead to its abrupt drainage, as well its evolution over the past eight years.