Do you know what can be found under ice caps?

I asked my friends what they thought was under an ice cap – the reply… more ice? 

The truth is that there can be many different things hidden under ice for example: large mountain ranges like the Transantarctic Mountains in Antarctica or many geomorphic features formed by the ice as seen now in the Scottish landscape.

Martin Sharp from the University of Alberta showcased his new findings at the Hutton Club seminar on the 18th of Jan 2019 discussing what has been recently found under the Devon Ice Cap (DIC). The DIC is found on Devon Island as part of the Canadian Arctic. Previously there has been limited research on the understanding of the Canadian Arctic and the large ice caps in this area have been unknown. However, recently there has been radar campaigns allowing for many recent discoveries.

Sub-glacial lakes

Sharp wanted to be able to determine what features had formed under the DIC and so used the technique of radio-echo sounding measurements which can be used to identify sub-glacial lakes. The technique can highlight the presence of lakes, as the lakes show up as flat, bright areas in the data with mirror like reflections.  The technique demonstrated that there were two sub-glacial lakes that had formed in the NE of the ice cap. The presence of these lakes was supported by looking a geological maps of the area which emphasised that there were geological troughs at the location of the lakes allowing for a build up of water.

Figure 1: Location of the sub-glacial lakes on the Devon Ice Cap (Rutishauser et al., 2018).

The basal temperature of the ice was modeled to gauge if it is possible for the water to be located there. The calculated temperature was from -12 to -10.5 degrees celsius which is too cold for natural uncontaminated water to have not frozen. Therefore, there must be contaminating elements in the water which are lowering the freezing temperature. It was proposed that NaCl (sodium chlorite) may be contaminating the water to make the lakes hyper-saline as the modeled basal temperature is lower than the freezing temperature of NaCl.

These are the first identified hyper-saline lakes in the world.

How could saline sub-glacial lakes form?

There has been two ideas proposed for the formation of a hyper-saline lake under an ice cap.

1: From projecting the geological maps of the surrounding area it is found that there is Ordovician anhydrite (salt evaportate) found at the site. Therefore, the anhydrite could easily dissolute and be mixed with the water to become more saline.

2: Or it could be that the lakes had water in them which has frozen and unfrozen repetitively to become more and more concentrated over time resulting in saline waters.

Figure 2: Geological map of  the area surrounding the sub-glacial lakes. The yellow colour highlights the areas with anhydrite geology (Rutishauser et al., 2018).

 Clearly there are still many questions to be asked to understand these lakes fully such as the depth of the water and the hydrological dynamics. But perhaps there may be more hyper-saline sub-glacial lakes in the world and more radio-echo sounding measurements in the world may highlight this.

What else could be found under DIC?

The Sverdrup glacier which is NW of the glacial lakes on the DIC has been found to have a very interesting sub-glacial drainage system which has not be discovered in the past. Sharp visited the glacier and explored the sub-glacial drainage system network. Firstly, there are many layers of fluvial gravel forming as ice flows over the bedrock with findings of plant life, bivalves and insects in the gravel. The different findings in the fluvial gravel could highlight that the glacier retreated allowing for raised beaches to have formed and then re-advanced taking beach deposits into the centre of the glacier.

Also found that in there were ice crystals formed on the roof of the ice caverns below the glacier. It has been hypothesised that the ice crystals formed when the sub-glacial water evaporates and results in condensation at the roof to form crystals.

Overall, Sharp’s research on the DIC was very interesting and was a clear talk that was easy to follow. The research is also key to the understanding of the Canadian Arctic area and will hopefully get other glaciologists  interested in this area (me after this talk). Moreover, since the finding of the hyper-saline sub-glacial lakes in the DIC, there has also been the identification of an underground lake on Mars using a similar technique. Maybe there are more sub-glacial or underground lakes to be found in the future?

More information: 

National Geographic, 2018 – Underground Lake Found on Mars? Get the facts. https://www.nationalgeographic.co.uk/science/2018/07/underground-lake-found-mars-get-facts

 Rutishauser, A., Blankenship, D., Sharp, M., Skidmore, M., Greenbaum, J., Grima, C., Schroeder, D., Dowdeswell, J. and Young, D. (2018). Discovery of a hypersaline subglacial lake complex beneath Devon Ice Cap, Canadian Arctic. Science Advances, 4(4), pp.1-6.