Larsen C Iceberg has finally gone!

After months of intense scrutiny and media attention the Larsen C iceberg (now known by the catchy name A68) finally broke away from the ice shelf.

To hear about just how big this berg is (how big even is Luxembourg eh, The Guardian?) I went on BBC Radio Berkshire to talk about this trillion ton ice cube, you can listen here.

DEhpDrqWAAECXJP

 

 

 

Should I bet on an iceberg? What is going on with Larsen C?

The ice shelf that my PhD is based on last week hit the headlines with the news that a crevasse in the ice shelf had grown suddenly, and now an iceberg of about 5000 sq km (that’s about 1/4 the size of Wales to use the internationally recognised unit for big things) is set to break away from the ice shelf. Should the iceberg break off it will be one of the top 10 biggest every recorded.

larsen-c-crevasse-nasa

The crevasse between Larsen C and the potential ice berg (image NASA).

However, the big news among glaciologists is surely that that things we find exciting have finally made it in the big time: Paddy Power are offering odds on when the iceberg will detach (or calve to give it its technical name).

screen-shot-2017-01-10-at-23-47-44

So is it worth a punt?

Well even the experts aren’t sure. Prof Adrian Luckmann, who is part of the MIDAS project which released the news about the crevasse told the BBC that he’d be “amazed” if the iceberg doesn’t calve in the next few months. Looking at the scale of the crevasse and the speed at which it seems to have grown recently this seems like pretty sound reasoning:

larsen-c-iceberg-midas

However, before you go splashing all your cash on January and February remember there is still 20 km of ice holding that iceberg on, which is still a fair distance. We also don’t yet know what caused the sudden growth of the crevasse at the end of last year.

Large break up events tend to happen in the Antarctic summer (i.e. our Winter) so if it’s going to happen and it’s not in the next month or two it may well not be until next year.

So that narrows things down quite a bit but there’s still a bit of guessing to be done if you feel this is more worthy of your money than guessing how many goals Chelsea will score against Leicester on Saturday which I’d personally recon as being a much safer bet.

A few other notes about this iceberg that may be of general interest:

  • Its breaking away won’t contribute to sea level rise (it’s already floating on the ocean so it has already displaced its own weight in the water), but it may make the ice shelf less stable.
  • aAlthough previous ice shelf collapses such as that of Larsen C’s former next door neighbour Larsen B did follow big iceberg events, there was significantly more melting observed on Larsen B prior to this, so a sudden collapse of Larsen C is still unlikely.
  • However, if Larsen C did collapse it could lead to sea level rise through the glaciers that used to flow onto the ice shelf speeding up and flowing into the ocean.
  • Yes, penguins have been known to live on Larsen C 😦

And remember, please gamble responsibly. And that does not mean signing up for your free bonus bets and then putting them on Barnet FC to get promoted. That would be silly.

 

Lost penguins found on my ice shelf!

Carl Anton Larsen (image thecoldestjourney.org)

Carl Anton Larsen (image thecoldestjourney.org)

Earlier last year a new emperor penguin colony was discovered but it appears they may not actually be that new.

In 1893, the explorer Carl Anton Larsen reported what is thought to have been the first sighting of emperor penguins in the area that is now known after him as the Larsen ice shelves. However, this sighting had never been verified until recent satellite images found a colony on the Larsen C ice shelf. It is thought that these are the same colony and are permanently established on the ice shelf, unlike two other colonies who have recently been reported to be moving onto ice shelves due to changes in the development of their natural habitat, sea ice.

This is especially exciting for me as the Larsen C ice shelf is the one my work is based on. For better or for worse it is much easier for me to put my work into context if I tell people about penguins losing their homes than sea level rise, although one of these may be a much bigger problem for us in the long term.

http://www.livescience.com/42431-emperor-penguins-ice-shelf-colonies.html

Antarctica in the news: The ‘unstoppable’ collapse of the West Antarctic Ice Sheet

Thwaites glacier (Image from NASA ICE)

Thwaites glacier (Image from NASA ICE)

What’s happening?

Two studies hit headlines (confusingly several media articles reported either one or both of them with similar headlines) this week that suggest that glaciers on the West Antarctic Ice Sheet (WAIS), which was already thought to be vulnerable, are shrinking and are set to contribute significantly to sea level rise.

Map of Antarctica showing the Amundsen Sea, which glaciers of the WAIS flow into.

Map of Antarctica showing the Amundsen Sea, which glaciers of the WAIS flow into.

The outcome isn’t certain: we don’t know enough about Antarctica, it’s history and the Earth’s climate system to really say very much to 100% certainity- but here we have one study that is based on modelling a key glacier on the ice sheet (Thwaites Glacier) and one that is based on observations so the combination of the two provides strong evidence.

The first study models changes in Thwaites Glacier for different levels of melting and for all but the lowest level of melt the onset of rapid collapse of the glacier happens within a millenium (current observations match the higher end of the melting levels they melted, this would have collapse somewhere within the next 300 years or so). The second study  is based on observations that several glaciers are melting faster than most scientist had expected.

Thwaites Glacier meeting the ocean (Image NASA ICE).

Thwaites Glacier meeting the ocean (Image NASA ICE).

 

How much ice are we talking here?

The loss of the whole West Antarctic ice sheet would contirbute 3.3m of sea level rise, and just the glaciers in the 2nd study could contribute over 1.2m between them. However, as mentioned above this is over potentially long time scales but that still doesn’t mean that significant changes could happen, potentially within our lifetimes- these glaciers are already releasing the same amount of ice annually as Greenland.

So why is the WAIS so much at risk?

A simplified diagram of a grounding line (www.AntarcticGlaciers.org).

A simplified diagram of a grounding line (www.AntarcticGlaciers.org).

As the ice shelves coming from the glaciers are melting, they become lighter, meaning that they can float above areas where they used to be grounded. The point where the ice flows off of the land and becomes a floating ice shelf is called the grounding line and the grounding lines of the glaciers studies are moving further back towards the sources of the glaciers.

This retreat can be held back by “pinning points”, hills or bumps beneath the ice- a lack of these and the gerneal shape of the land below the ice reduced that WAIS’s ability to slow the glaciers down.

Bonus extra bit of cool science

You can watch a video by Eric Rignot, author of one of the 2nd study, with lots of exciting graphics and images of what’s underneath the WAIS here:

 

If this sounds interesting and you’d like a more in depth explanation I’d recommend heading here.

 

References:

1st study (Joughin et al.): http://www.sciencemag.org/content/344/6185/735

2nd Study (Rignot et al.): http://onlinelibrary.wiley.com/doi/10.1002/2014GL060140/abstract

Potential sea level rise from the west Antarctic ice sheet: http://www.sciencemag.org/content/324/5929/901

 

 

Antarctica in the news: B31 iceberg

Satellite images of the B31 iceberg as it heads out of the Pine Island Bay (original image NASA, edited S.Buzzard)

Satellite images of the B31 iceberg as it heads out of the Pine Island Bay (original image NASA, edited S.Buzzard). The white stuff in the bay in the first picture is sea ice/ cloud, not part of the ice shelf.

 

What is it?

The B31 iceberg (which to use my favorite comparison is half the size of Greater London) hit the news last year when it broke away from the Pine Island Glacier on Antarctica. It hit headlines again more recently as it was observed that it had left the bay around the glacier and is therefore entering open ocean.

The location of Pine Island Glacier (image BBC).

The location of Pine Island Glacier (image BBC).

Is this going to cause sea level rise?

Not directly. The iceberg itself was part of an ice shelf which means that the ice had flowed from the land on Pine Island Glacier and was floating on the water. So at the time it left the land and became part of the ice shelf it displaced water which would have contributed to sea level rise (in the same way that the level goes up in your glass of water (or in my case more likely G&T) when you add ice cubes to it). Ice shelf creation is balanced by other processes taking water out of the system, it’s when the ice shelves collapse or change this can lead to an imbalance, such as was the case for Larsen B.

Schematic of the pine island glacier demonstrating how the ice shelf floats on the water. (Image from antarcticglaciers.org- go there, it's excellent)

Schematic of the Pine Island Glacier demonstrating how the ice shelf floats on the water. (Image from antarcticglaciers.org- go there, it’s excellent)

If it’s not sea level rise then why does it matter?

The issue is that the iceberg is now floating into open ocean, causing a shipping hazard. The iceberg will also end up melting, adding cold, fresh water to the ocean where it wouldn’t normally be, potentially affecting ocean circulation, biological habitat, etc.

Bonus extra bit of cool science

(Yes I used the word cool deliberately here. No I’m not ashamed) The iceberg is being tracked via GPS monitoring devices contained on ice javelins which were dropped onto the iceberg out of an airplane.

Ponds on ice- What I do and why (I think!) it matters

Melt ponds, which are exactly what the name implies – ponds of melted water formed on ice – have been observed in recent years on the Antarctic Peninsula, the most northern part of Antarctica. Previously this area had been too cold for melting to occur but, due to a 2.5 degrees Centigrade warming trend on the Peninsula over the last 50 years (several times the global average), this has begun to change.[1]

Melt ponds on Arctic sea ice such as those initially modelled by CPOM, copyright NASA Goddard Space Flight Center

Melt ponds on Arctic sea ice such as those initially modelled by CPOM, copyright NASA Goddard Space Flight Center

The Larsen B ice shelf on the Antarctic Peninsula hit the headlines in 2002 when it spectacularly (see image below- definitely a justified use of the word spectacular!) collapsed and an area of ice larger than Rhode Island was lost in a matter of weeks.[2] This collapse occurred during record warm air temperatures when both the length and extent of the melt season reached a new high. Areas of the ice shelf with melt ponds collapsed whereas adjacent areas with few or no melt ponds did not. This suggests that melt ponds may be playing a role in triggering ice shelf collapse. However, there are many other processes – such as rising ocean temperatures – which may also play a role and so a greater understanding of ice-shelves and the mechanisms affecting them is essential in predicting their future.

A common misconception is that when ice shelves collapse they contribute to sea level rise. This is not strictly true; ice shelves are already floating on the water and in the same way that when ice cubes in your glass of water melt the water level in the glass doesn’t go up, ice shelf break-up (and subsequent melting) won’t add to global sea level. By Archimedes’ Principle (that’s the one from the ‘jumping out of the bath shouting “Eureka”’ story) the floating ice has already displaced a volume of water that is virtually the same as the amount that would be added to the sea if the ice shelf were to melt.*

However, the fact that ice shelf break-up doesn’t contribute to sea level directly doesn’t mean that it doesn’t have an effect on it. When Larsen B broke up it was observed that the glaciers which fed into the ice sheet accelerated, possibly because there was no longer any force from the ice sheet blocking their flow. The ice coming from these glaciers is coming from the land and going into the sea so does contribute to sea level rise. This acceleration can continue for several years after the ice shelf has collapsed,[3] so the effect of a large collapse can actually be quite significant. On top of this, there is also the loss of habitat and the effect that large amounts of cold fresh water from the melted ice shelves have on ocean circulation and chemical make-up to be considered.

The break up of Larsen B in early 2002. The dark marks on the ice shelf you can see are melt ponds or drained melt ponds. Copyright NASA.

The break up of Larsen B in early 2002. The dark marks on the ice shelf you can see are melt ponds or drained melt ponds. Copyright NASA.

So what is it about these ponds makes them so key in understanding what will happen to the ice shelves? Firstly, it’s important to note that ‘pond’ is quite a deceptive term – on the Antarctic Peninsula we’re talking about something that can cover several square kilometers as oppose to something that would be found in your back garden, so these ponds are actually a fairly significant feature of the ice shelf.

One of the crucial things that melt ponds affect is albedo. Albedo is the proportion of incoming radiation that a surface reflects back. Ice, being white, has a high albedo whereas a melt pond is darker and has a lower albedo: it will reflect less energy and thus absorb more energy. Absorbing more energy means more heat is absorbed, more ice melts, ponds grow, albedo is further decreased, more energy is absorbed and so on in a positive feedback loop that results in greater and greater amounts of ice melting.

Meltwater is also thought to influence ice shelf break up when it fills crevasses in the ice. The forces that act on crevasses that open in the ice sheet tend to close them but meltwater filling existing surface crevasses provides an outward pressure that can allow them to remain open. Additionally, meltwater can cause the crevasses to penetrate further through the ice shelf, possibly far enough for them to reach the ice shelf’s base and impact on its structural integrity.[1]

greenlandponds_ali_2010185

A melt pond on the Greenland ice sheet- very similar to those I’m looking at and hopefully a lot of my work can be applied to Greenland too. Copyright NASA Earth Observatory.

Researchers in the group that I’m part of- Centre for Polar Observation and Modelling (CPOM) [4] at the University of Reading are looking at improving climate models by incorporating a better understanding of the processes affecting melt pond formation into the models. Initially, work was done on modelling melt ponds on Arctic sea ice [5]; one of the greatest uncertainties in predicting future global temperature changes is sea ice level fluctuations and this is something the level of melt ponds will play a role in. Now they have successfully incorporated a physically based melt pond scheme into the CICE sea ice model in order to simulate the stages of melt pond development.[6]

So where do I come into this? I’m going to be adapting a physical model of Arctic sea ice melt ponds to look at the Antarctic, focussing on the Larsen C ice shelf as melt ponds have appeared there and it is thought to be a potential candidate for future collapse. The ponds found on Antarctica are much larger and over a greater scale than the Arctic sea ice ones and, unlike sea ice, the ice-shelves do not contain salt, adding an extra challenge in modifying previous work. If successful this model will help to provide new insights into the role of meltwater in the collapse of ice shelves and help to improve future versions of ice sheet models and climate predictions. I’ll keep you updated.

*Technically, a very small amount of sea level rise would occur on melting as ice shelves are made of fresh water and sea water is salty (and therefore more dense than fresh water) so slightly less water is displaced than the total melted amount would add but the effect is so small it is negligible: the equivalent of less than 4cm of sea level rise if all floating ice (ice shelves and sea ice) were to melt.

References:

[1] Scambos et al. (2000), The link between climate warming and break-up of ice shelves in the Antarctic Peninsula, Journal of Glaciology, Vol. 46, No. 154, pg 516-529

[2] http://nsidc.org/news/press/larsen_B/2002.html

[3] Scambos et al. (2004), Glacier acceleration and thinning after ice shelf collapse in the Larsen B embayment Antarctica, Geophys. Res. Lett., 31, L18402, doi:10.1029/2006GL020670

[4] http://www.cpom.org/research.html

[5] Scott and Feltham (2010), A model of the three-dimensional evolution of Arctic melt ponds on first-year and multiyear sea ice, J. Geophys. Res., Vol.115, C12064, doi:10.1029/2010JC006156

[6] Flocco et al. (2010), Incorporation of a physically based melt pond scheme into the sea ice component of a climate model,  J. Geophys. Res., Vol.115, C08012, doi:10.1029/2009JC005568