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.
Until recently it was thought that all emperor penguins bread on fast ice, that’s sea ice attached to the land; much easier to navigate than the cliffs of ice shelves (image Photo Volcania).
It has been well publicised recently that despite sea ice in the Arctic decreasing, sea ice in the Antarctic has been on the increase. Emperor penguins breed on sea ice, so surely this would be a good thing for the penguins?
Unfortunately, this isn’t the case- even though there is more ice forming it’s forming too late for the penguins’ breeding season. The climate of Antarctica is changing, it has warmed more than 5 times the global average over the last century. It is thought that one of the colonies discovered moved as a result of the late arrival of the sea ice, potentially due to a changing climate.
Penguin colonies can actually be spotted in satellite images such as the one below and it was a combination of this and aerial views from planes that alerted scientist to the fact that these colonies that have moved onto ice shelves.
A satellite image of an emperor penguin colony on an ice shelf (Image BAS/Digital Global). Guano is a term for penguin excrement.
It’s not known quite how the penguins manage to climb up cliffs onto the ice shelves as the colonies haven’t been studied up close but it is thought they might be able to shuffle up between ridges formed by draining water on the ice shelves.
Although it is bad news that the penguins are having to do this it’s a nice positive in their chances of future survival. Polar regions warm faster than other areas so this may not be the end of unusual penguin behaviour if the planet continues to warm.
An emperor penguin huddle. The males are left to look after the eggs while the females go off and hunt, they huddle together to try and survive the freezing conditions such as during the blizzard shown here (image Australian Antarctic Division).
The original research article (Fretwell et al.) is http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0085285
Radar measurements have shown that Antarctica is losing ice at twice the rate previously estimated- it is contributing to 0.45mm of sea level rise per year.
This work was carried out by the Centre for Polar Observation and Modelling (CPOM) at Leeds University- CPOM are the group I’m part of but I’m in the Reading branch so this is extra exciting.
Ice loss from Antarctica- look towards the West, the area around the Amundsen Sea was in the news last week. Image ESA/CPOM/M.McMillan/Leeds Uni
How much is being lost?
0.45mm of sea level rise might not sound like a lot but in terms of the amount of ice involved that’s 159 billion tonnes of ice disappearing each year- to use a media favorite comparison I make that over 6 million Olympic sized swimming pools of ice.
Isn’t Antarctica supposed to be gaining ice?
Sea ice around Antarctica has been increasing recently (this could be for several reasons including changes in ocean circulation and weather) but this is only sea ice- frozen sea water, floating on the sea. The ice loss in this study is ice coming from off of the land and going into the ocean.
Extra bit of cool science
The reason this radar information is so much better than anything we’ve had previously is because the satellite involved, Cryosat can penetrate cloud. Previous satellites couldn’t do this so estimates had to be made wherever there was cloud suing information from cloud free areas. We now have 96% satellite coverage of Antarctica which makes monitoring future changes much easier.
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).
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)
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.