An iceberg as big as Delaware! For those of you that are saying, “what’s a Delaware,?” — it is the second smallest State of the USA’s 50 States. Even so, an iceberg that big is really impressive. If it ran into the Titanic, the ship’s orchestra would probably not have had time to play for the people before the ship sank. (That’s from the movie– I am not sure the orchestra really played while the ship sank.)
Around 12 July this year, this huge piece of ice broke off from the Larson C ice shelf in Antarctica. The iceberg, named A68, has an area of 5800 km² (2239 miles²). The authorities say it is the 5th largest berg in history. Because the continent of Antarctica is so inhospitable, it wasn’t till 1821 when an American seal hunter became the first person to actually put foot on this continent. History, in this instance, is very short.
The record iceberg size, according to geologists, is B15 that floated out to sea in 2000, It’s area was measured at 9,250 km². Which is just about 1.5X the size of A 68. Tony Heller found a newspaper account of an US Navy ice breaker coming across an iceberg measuring 208 miles by 80 miles or 12,480 miles² (32,320 km²). From Heller’s website is this article”
The Navy icebreaker siting and the other two in the article are all more than 60 years into the past. That no scientists use them in their record keeping of sizes of Icebergs, suggests that many icebergs of various sizes were likely to have escaped the attention of the scientists studying Antarctica at that time. My guess the is that measurements by Admiral Byrd are probably accurate. The other two are more questionable.
What are the lessons we take from this new event? The scientists in the Antarctica will not say that we are seeing climate change in action. They are saying it could be, and time will tell, but for now, not climate change. The media found some researchers that say it is definitely global warming. Some surprise that is.
It reported that there are volcanoes underwater in the vicinity of the Larsen Ice Shelf. Perhaps we will have a guest posting on this issue.
A68’s estimated weight is one trillion tonnes. So how much will it raise sea level?
Everybody( with the exception of some of the people in the media) say—-it will not raise it at all.
The trick here is that it came from an ice shelf that was already floating in the water. It had displaced its weight in the sea water and so any effect on global sea level had already taken place.
From the stuff I learned in college or somewhere—Ice, unlike most things, expands when it freezes. If I remember correctly, it expands by 4%. Thus, it is slightly less dense than the liquid water. Add to that, salt water is more dense that fresh water. So for the same volumes, icebergs are lighter than the sea water. You have heard the old saying, “the tip of the iceberg”.
Taking a look at what an ice shelf is using a drawing by Dr. Sue Cook as shown below:
Dr. Cook says “”Ice shelves are constantly flowing into the ocean, losing a bit off the end.”
The Larsen C ice shelf is the leading seaward part of a glacier that is moving out to sea. The glacier might be one or two miles deep and the bulk is still resting on the ground. While the sea is melting the glacier on the underside, the top is cantilevering out and floating on the sea. Eventually the leading edge of the cantilevered ice breaks away from the main body and goes out to sea.
There is a protocol to keep track of where an iceberg like A68 is located. This information is used to protect vessels at sea.
Rest easy for now.