| Summary: | On the west coast of Greenland near Disko Bay an outlet glacier named Sarquardliup sermia forms an ice dam across a valley to produce Lake Tiningnilik. Expeditions in the early 20th century reported that the lake drains cyclically about every 10 years establishing an important baseline for a stable pattern in nature lasting through the 19th and 20th centuries until now. In summer 2010 the lake drained after just 7 years and at a lower water stand than the 2003 pre-drainage levels. This represents an adjustment to new equilibrium conditions with the ice dam and might be an index of recent local climate change in Greenland. We take a close look at Lake Tiningnilik and previous studies to constrain the timing of the drainage events using historical air photos and satellite imagery starting in the 1940s and 1970s, respectively. Tiningnilik has been occasionally surveyed on the ground since the 1980s and since the late 1990s regularly scanned by both aircraft and satellite laser altimetry, as well as satellite radar. Incorporating these data we are able to close some gaps in the historic chronology of the drainage events and suggest mechanisms to account for the recent change in the stable cycle. This information is important to understanding glacier dynamics and prediction of jökulhlaup which may erode the Sarqardliup sermia terminus and facilitate glacial surges. Improving upon previous estimates our data constrain the timing and therefore flow rates of the Lake Tiningnilik drainages in 2003 and 2010.
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