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Cryospheric Sciences

Dronning Maud Land

Image of the Week — Hidden lakes in East Antarctica !

Image of the Week — Hidden lakes in East Antarctica !

Who would have guessed that such a beautiful picture could get you interviewed for the national news?! Certainly not me! And yet, the photo of this englacial lake (a lake trapped within the ice in Antarctica), or rather science behind it, managed to capture the media attention and brought me, one of the happy co-author of this study,  on the Belgian  television… But what do we see on the picture and why is that interesting?


Where was the picture taken?

The Image of this Week shows a 4m-deep meltwater lake trapped 4 m under the surface of the Roi Baudouin Ice Shelf (a coastal area in East Antarctica). To capture this shot, a team of scientists led by Stef Lhermitte (TU Delft) and Jan Lenaerts (Utrecht University) went to the Roi Baudouin ice shelf, drilled a hole and lowered a camera down (see video 1).

Video 1 : Camera lowered into borehole to show an englacial lake 4m below the surface. [Credit: S. Lhermitte]

How was the lake formed?

In this region of East Antarctica, the katabatic winds are very persistent and come down from the centre of the ice sheet towards the coast, that is the floating ice shelf (see animation below). The effect of the winds are two-fold:

  1. They warm the surface because the temperature of the air mass increases during its descent and the katabatic winds mix the very cold layer of air right above the surface with warmer layers that lie above.
  2. They sweep the very bright snow away, revealing darker snow/ice, which absorb more solar radiation

The combination leads to more melting of the ice/snow in the grounding zone — the boundary between the ice sheet and ice shelf — , which further darkens the surface and therefore increases the amount of solar radiation absorbed, leading to more melting, etc. (This vicious circle is very similar to the ice-albedo feedback presented in this previous post).

Animation showing the processes causing the warm micro-climate on the ice shelf. [Credit: S. Lhermitte]

All the melted ice flows downstream and collects in depressions to form (sub)surface lakes. Those lakes are moving towards the ocean with the surrounding ice and are progressively buried by snowfalls to become englacial lakes. Alternatively, the meltwater can also form surface streams that drain in moulins (see video 2).

Video 2 : Meltwater streams and moulins that drain the water on the Roi Baudouin ice shelf. [Credit: S. Lhermitte]

Why does it matter ?

So far we’ve seen pretty images but you might wonder what could possibly justify an appearance in the national news… Unlike in Greenland, ice loss by surface melting has  often been considered negligible in Antarctica. Meltwater can however threaten the structural integrity of ice shelves, which act as a plug of the grounded ice from upstream. Surface melting and ponding was indeed one of the triggers of the dramatic ice shelves collapses in the past decades, in the Antarctic Peninsula . For instance, the many surfaces lakes on the surface of the Larsen Ice shelf in January 2002, fractured and weakened the ice shelf until it finally broke up (see video 3), releasing more grounded ice to the ocean than it used to do.

Of course surface ponding is not the only precondition for an ice shelf to collapse : ice shelves in the Peninsula had progressively thinned and weakened for decades, prior their disintegration. Our study suggests however that surface processes in East Antarctica are more important than previously thought, which means that this part of the continent is probably more vulnerable to climate change than previously assumed. In the future, warmer climates will intensify melt, increasing the risk to destabilise the East Antarctic ice sheet.

Video 3 : MODIS images show Larsen-B collapse between January 31 and April 13, 2002. [Credit:NASA/Goddard Space Flight Center ]

Reference/Further reading

Edited by Nanna Karlsson

Image of the Week – Antarctic fieldwork 50 years ago!

Image of the Week – Antarctic fieldwork 50 years ago!

So far this blog has published many pictures of current polar field work campaigns. Today, we would like to take you back to Antarctic expeditions during the 1960s. The photos presented in this post date back from the Belgian-Dutch Antarctic field campaigns of 1964-1966.

The first picture shows Ken Blaiklock (red overalls) with a Belgian surveyor. Ken was part of the 1955–58 Commonwealth Trans-Antarctic Expedition – completing the first overland Antarctic crossing via the south pole. This shot was taken during the 1964-1965 summer campaign, as they were surveying the displacement of glaciers in the Sør Rondane Mountains, East Antarctica.  At that time, the men had to leave the base station for three weeks with two dog-sled pulled by a small skidoo-like vehicle. Remarkably, this shot doesn’t look too dissimilar to many field campaigns today, where the same type of sledges are still used and the clothing worn is also very similar. However, logistical support was very different, with no technicians or field guides those who were part of the polar expeditions of 50 years ago had to be experts at everything!

The second picture illustrates how precise positions (and relative displacements) were measured at that time. No fancy GPS technology, but a network of markers and theodolites. The shot was taken on a pinning point, close to the front of the Roi Baudouin Ice shelf, during the overwintering campaign of 1965 (where people had to stay in Antarctica for 15 months).

A geodesist measuring the precision position of a marker with his theodolite, overwintering campaign in Antarctica, 1965. (Credit: Jean-Jacques Derwael)

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My first journey to Antarctica – Brice Van Liefferinge

My first journey to Antarctica – Brice Van Liefferinge
(Credit B. Van Liefferinge)

(Credit B. Van Liefferinge)

19 November 2014, the Iliuchine 76 gently lands on the runway of the Russian Antarctic station, Novolazarevskaya, in Dronning Maud Land. For the first time, I’m in Antarctica! It is 4 o’clock in the morning and we need to hurriedly offload 2 tons of material intended for our field mission near the Belgian Princess Elisabeth Station. I’m deeply impressed by the landscape although it is dotted with containers, people and machines. I am impressed by the fuzz. I am impressed by the novelty. I am impressed by the icescape. It is cold, but I don’t feel it.

(Credit B. Van Liefferinge)

(Credit B. Van Liefferinge)

I take part in an expedition lasting five weeks and led by the Laboratoire de Glaciologie of the Université Libre de Bruxelles (ULB) in the framework of the Icecon project.The project aims at constraining past and current mass changes of the Antarctic ice sheet in the coastal area of Dronning Maud Land (East Antarctica) to better understand past and present ice volumes and the extension of the Antarctic ice sheet across the continental shelf during the last glacial period. This year we are a team of 5 to do the job: GPS measurements, ice-core drilling, high- and low-frequency radar measurements (GSSI and ApRES), televiewer measurements … The ApRES radar is a new phase-sensitive radar developed by British Antarctic Survey (BAS), capable of detecting internal structures in the ice and changes in the position of internal layering over time.

After a couple of hours at the Russian base, it’s time to fly to the Princess Elisabeth Station (the Belgium base, PEA). The arrival in a Bassler (a former DC3 re-equipped with turbo-props) with stunning views of the Sor Rondane Mountains and the Princess Elisabeth station on the Utsteinen rim is simply magnificent. Alain Hubert, the base manager, gives us the first security rules and shows us the different parts of the base.

(Credit B. Van Liefferinge)

(Credit B. Van Liefferinge)

 

After following the various field training and especially an exercise that aims at pulling yourself out of crevasses, it’s time to inspect, to set up, and to test our equipment. While one part of the team sets up the drill, Frank Pattyn and I test the GPS and radar equipment, mainly the ApRES that is a new “toy” for us. The first results are promising, we can clearly identify the bed topography and internal layers. The two GPS systems sponsored by the “10km of the ULB”, a run organised by the students of our Faculty, are also tested next to the L1L2 GPS systems for precise positioning. As our departure is imminent, I’m excited (even though my level of Coca-cola are getting low – I ‘m an avid consumer of this “evil drink” and Frank was afraid that I wouldn’t survive without sufficient sugar intake).

(Credit B. Van Liefferinge)

(Credit B. Van Liefferinge)

On 27 November, we leave PEA in the evening for one night and one day across the Roi Baudouin Ice Shelf to Derwael ice rise. We are 6 scientists, 2 field guides and 1 technician. After 25 hours of travel, we set up the camp on the top of the divide. We start immediately with the radar measurements to locate potential drill sites. However, we get caught in a storm the following day and as Frank says “not a nice one”.

(Credit F. Pattyn and B. Van Liefferinge)

(Credit F. Pattyn and B. Van Liefferinge)

 

The snow drift is just amazing and the atmospheric pressure drops frighteningly (“can this still go lower?”). The whiteboard installed in the living container is not wide enough to draw the graph of pressure change, nor is it high enough to accommodate the lowest values. Furthermore, it’s quite warm, meaning that snow melts in contact with persons and goods. Despite efforts of everyone to clear away the snow, we leave our tents and sleep in the containers for 2 days. Not the most comfortable nights, because we share a two-bunk space with three people, and despite a container it remains very shaky! After three days of amazing experience, we clean up the camp and the science restarts. For one week Frank and I perform radar and GPS measurements in a 10km radius around the camp. These measurements will be repeated in 2015-2016 to provide new data on ice compaction, density and flow. While Frank thoroughly checks the collected data, I have some time to get familiar with the drill, which should prove to be very useful thereafter. The “drill part” led by Jean-Louis Tison and Morgane Philippe aims at drilling two 30 m deep ice cores on Derwael Ice Rise, 2 km on each side of the divide. We want to investigate the spatial variability of snow accumulation induced by this ice rise that sticks approximately 300 m above the surrounding flat ice shelf and therefore perturbs the surface mass balance distribution (Lenaerts et al., 2014).

Blog_EGU (12)_mod

(Credit B. Van Liefferinge)

(Credit F. Pattyn and B. Van Liefferinge)

I use this week to improve my knowledge on other scientific techniques, such as the coffee-can method (will complement the results from the ApRES) or geodetic GPS measurements with Nicolas Bergeot. I also learn the basics of snowmobile mechanics (it’s surprising to see the amount of snow that can be put in an engine!). Unfortunately we get stuck for another 2 days by a new storm event. We use this time to have a look on the first radar profiles and to prepare the second part of the expedition.

 

 

On 9 December, we leave the camp on Derwael ice rise and move towards the Roi Baudouin Ice Shelf, 40km to the west. We set up the camp in a longitudinal depression (like a trench) on the ice shelf that stretches from the grounding line to the coast.

The purpose of this part of the field work is twofold: first of all, determine the mass budget of ice shelves. To do that, we need to map carefully the flow speed of the ice-shelf. Secondly, understand the formation of the trench in evaluating if under the ice-shelf, the ice is melting or accreting (formation of marine ice) and analyze the surface melt history by investigating near-surface melt layers.

The first three days are devoted to make radar measurements (ApRES) in the center and on the sides of the trench. The thickness of ice and the reflection at the interface with the ocean is different from the one on the ice rise; we take some time to develop a robust method and determine the best settings of the radar. Together with Frank Pattyn and Jan Lenaerts (InBev Baillet Latour fellowship, http://benemelt.blogspot.be/) I perform a 120km transect with a high-frequency radar towed by a snowmobile to map the near-surface internal structure along the ice shelf and link the drill site with the grounding zone. Driving at 8 km per hour for 8 hours a day, it’s an opportunity for me to think about how lucky I am to be here. Alone in the vastness of the Roi Baudouin ice-shelf, I feel very small. Back in camp, we find out that the drill got stuck at a depth of 54m in the borehole and preparations to free the drill are on their way. During this time I carry out a number of high-frequency radar measurements with Alain Hubert (the base manager) to fine-tune the equipment to potentially detect crevasses near the surface. To our surprise, we stumble upon a crevasse more than 500m long, 10m wide and 20m high. Moreover, we can safely descend through the apex of the crevasse to discover its vastness. Truly a magic moment!

(Credit A. Hubert)

(Credit A. Hubert)

 

Thirty-six hours later, and thanks to antifreeze, the drill restarts. This small technical incident pushes us to work the next couple of days through the day and the night (under the sun at 3am is rather special) and we take turns in operating the drill. We reach a depth of 107m, not far from the 155 meters needed to reach the bottom of the ice shelf, but the brittle ice makes progress very difficult. Nevertheless, this is the third core of the (short) season, and as valuable as the previous ones. We can clearly identify every single ice layer over 200 years as well as the surface melting history.

(Credit A. Hubert)

(Credit A. Hubert)

Before leaving back to the base, we finish the installation of the famous Tweetin’IceShelf project (http://tweetiniceshelf.blogspot.com); a project also presented at the EGU General Assembly in 2015. We deploy two GPSes on the flanks of the trench and one in the center. These are simple GPS systems that record their position every hour. They are named GPS CGEO (from Cercle de Géographie et de Géologie de l’ULB) and GPS CdS (from Cercle des Sciences). In the center of the trench, the ApRES is installed which measures once a day the radar signal through the ice. All systems will be effective throughout the Antarctic winter. Data are sent via Twitter to be followed by a larger community. Just follow the @TweetinIceShelf on Twitter. You will not be disappointed.

(Credit F. Pattyn)

(Credit F. Pattyn)

It’s time to go back to the station, which is reached after 20 hours of travel across the ice shelf and the coastal ice sheet. Over 2 days we will be at Cape Town and we have to clean up everything for the next field season.

(Credit N. Bergeot)

(Credit N. Bergeot)

 

I know it is my first time to Antarctica, and as most first-timers, an unforgettable experience of vastness, whiteness, silence, laughter, hard work and fun. When I board the plane I feel delighted and fulfilled and ready to find back green landscapes and city soundscapes in less than ten hours.

The text is based on the blog that was held during the mission: http://icecon2012.blogspot.be/

Brice Van Liefferinge is a PhD student and a teaching assistant at the Laboratoire de Glaciology, Universite Libre de Bruxelles, Belgium. His research focuses on the basal conditions of the ice sheets.

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