Catalina Lake catastrophic drainage

Now you see it, now you don't.  Foreground: the western end of Catalina Lake.  Sometimes this section of the lake is just not there.  When a drainage "event" happens, the lake level falls by over 150m, leaving this area high and not exactly dry....... (PS -- this is a replacement image for one mistakenly labelled by the article authors........) 

Map extract showing Catalina Lake (to the right) at its "filled" size......

How did I miss this?  A report of periodic spectacular lake drainage from Catalina Lake in Renland, East Greenland.   The lake occupies a section of Catalina Dal, a through valley that runs across the island of Renland.

Periodic outburst floods from an ice-dammed lake in East Greenland
Aslak Grinsted,  Christine S. Hvidberg, Néstor Campos & Dorthe Dahl-Jensen

Nature  Scientific Reports volume 7, Article number: 9966 (2017)

https://www.nature.com/articles/s41598-017-07960-9

Abstract

We report evidence of four cycles of outburst floods from Catalina Lake, an ice-dammed lake in East Greenland, identified in satellite imagery between 1966–2016. The lake measures 20–25 km2, and lake level drops 130–150 m in each event, corresponding to a water volume of 2.6–3.4 Gt, and a release of potential energy of 1016 J, among the largest outburst floods reported in historical times. The drainage cycle has shortened systematically, and the lake filling rate has increased over each cycle, suggesting that the drainage pattern is changing due to climate warming with possible implications for environmental conditions in Scoresbysund fjord.

If you compare these two images carefully, you can see that the lake area has been reduced by around 50% between 2003 and 2004.  The western part has just disappeared, leaving behind a somewhat chaotic arrangement of dissected lake-floor sediments and jumbled ice fragments.  The ice has not drained westwards, but northwards beneath the tongue of the Edward Bailey Glacier.    The shelf area or floating section of the glacier has been lifted to allow the water from the lake to drain in the direction of the arrow.  The drainage event took place during the winter.  

Water and ice elevation changes between 1986 and 2007.  We do not know how these changes relate to the drainage cycle.......

Model illustrating how the expanding lake lifts the floating glacier snout and then escapes over the high subglacial col to the right of the diagram.

It is assumed by the authors that another drainage event is due before long, accelerated as a result of enhanced melting of ice caps and glaciers which are contributing meltwater to the lake.  The water level is currently building up inexorably...........

Watch this space.......

Then it gets more complicated.  Here is another article that suggests that in the past the Edward Bailey Glacier has been more extensive and has been solidly grounded, forcing the Catalina Lake to overflow or spill westwards!  In through valleys like this, occupied by assorted glacier snouts and meltwater lakes, anything can happen......

Changes in glacial meltwater alter algal communities in lakes of Scoresby Sund, Renland, East Greenland throughout the Holocene: Abrupt reorganizations began 1000 years before present.

by Krista E H Slemmons, Aaron Medford, Brenda L. Hall, Jasmine Saros et al

November 2016
The Holocene 27(7)
https://journals.sagepub.com/doi/abs/10.1177/0959683616678468

DOI:   10.1177/0959683616678468

I think this is a spring / early summer image from 2019.  The mottled surface looks like a frozen lake just in the process of melting.  I interpret this as showing the the lake is full -- and ready to go at any moment.......