The iceberg A66 is about 15 km at it's widest point in this image.
We can do a bit simple maths. Estimate the iceberg has a 200 m thickness and it is triangular in shape with a base of ~4 km.
the volume = 0.5 x 15 km x 4 km x 0.2 km = 6 km3.
So the relatively small A66 contains of 6000 gigtons of water. It's a lot. But it's not a lot.
Icebergs get their reference number depending on where they originate from. This one has an identifier "A" which means it came from the sector 0° to 90°W - that's the Bellingshausen and Weddell Sea region. You can track icebergs like this both visually - like in in the image above - or using something called a Scatterometer. A scatterometer can measure the winds over the ocean, and because the winds change over the ice one can track the icebergs. Prof David Long at Brigham Young University provides an excellent database of Antarctic iceberg data based on that idea (this is their research paper on how they do that).
If we look at the location data from the ASCAT sensor you can see that A66 is at the tip of the Antarctic Peninsula - but this data is only from this year. I will have to dig a little deeper. A job for later.
Once the icebergs reach the edge of the Weddell Sea they get to South Georgia very quickly. I did write about that in a paper in the OU database Physical oceanography in the Scotia Sea during the CCAMLR 2000 survey, austral summer 2000.
And some of these icebergs (although not A66) ground at South Georgia and ultimately can affect the ecosystem. Jon Amos wrote about some work I did at a San Francisco conference in 2010 about that - it's still available on the BBC website: Giant icebergs head to watery end at island graveyard.
Overall A66 is nothing special, this is not an unusual observation.
It is a beautiful image though.