Sub-seasonal thaw slump mass wasting is not consistently energy limited at the landscape scale

• Main Authors: Zwieback, Simon, Kokelj, Steve, Günther, Frank, Boike, Julia, Grosse, Guido, Hajnsek, Irena
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Copernicus 2017
• Subjects: The Cryosphere; The Cryosphere Discussions
• Online Access: https://epic.awi.de/id/eprint/45376/; https://epic.awi.de/id/eprint/45376/1/tc-2017-141.pdf; https://www.the-cryosphere-discuss.net/tc-2017-141/; https://hdl.handle.net/10013/epic.51519; https://hdl.handle.net/10013/epic.51519.d001

Predicting future thaw slump activity requires a sound understanding of the atmospheric drivers and geomorphic controls on mass wasting across a range of time scales. On sub-seasonal time scales, sparse measurements indicate that mass wasting at active slumps is often limited by the energy available for melting ground ice, but other factors such as rainfall or the formation of an insulating veneer may also be relevant. To study the sub-seasonal drivers, we derive topographic changes from single-pass radar interferometric data acquired by the TanDEM-X satellite (12 m resolution). The high vertical precision (around 30 cm), frequent observations (11 days) and large coverage (5000 km2) allow us to track volume losses as drivers such as the available energy change during summer in two study regions. We find that thaw slumps in the Tuktoyaktuk coastlands, Canada, are not energy limited in June, as they undergo limited mass wasting (height loss of around 0 cm/day) despite the ample available energy, indicating the widespread presence of an insulating snow or debris veneer. Later in summer, height losses generally increase (around 3 cm/day), but they do so in distinct ways. For many slumps, mass wasting tracks the available energy, a temporal pattern that is also observed at coastal yedoma cliffs on the Bykovsky Peninsula, Russia. However, the other two common temporal trajectories are asynchronous with the available energy, as they track strong precipitation events or show a sudden speed-up in late August, respectively. The observed temporal patterns are poorly related to slump characteristics like the slump area. The contrasting temporal behaviour of nearby thaw slumps highlights the importance of complex local and temporally varying controls on mass wasting.