It’s easy to get lost when you hear about the accelerated melting of ice at Antarctica. Who has been to Antarctica or even stared at it a long time on a globe’s under side? We hardly know what the continent looks like, let alone its shape or components — for the record, the big pieces are the West Antarctic sheet (with its tail the Antarctic Peninsula) and the humongous East Antarctic sheet. That’s all of Antarctica, right there. The Greenland ice sheet is the other biggie on Earth.
Recently, we learned that the Wilkins ice shelf (a part of the Antarctic Peninsula) is about to break off and the East Antarctic sheet is showing signs of melting, all a result of climate change.

So why is all this melting a problem? And what is the difference between an ice sheet and an ice shelf?

This article in the February issue of Scientific American cleared it all up for me. There are ice shelves, which jut out from Antarctica’s fringe and hang over the water. And then there are more massive sheets, which lie on top of bedrock and are like a huge cap on the continent. The shelves are buttressed by the sheets, but warming air temps are melting the shelves, thereby weakening the buttressing, so the shelves are calving off and the sheets are more likely to melt and even break away eventually. Warming air also is melting the sheets and broadening big lakes and rivers above and below the sheets, which acts like a lubricant and causes sheets to move around more swiftly and to weaken.

When the shelves and sheets weaken and break off into the ocean, sea level rises a lot. How much?

Here is what Robin Bell of Columbia University’s Earth Institute writes in SciAm:

“A third of the world’s population lives within about 300 feet above sea level, and most of the planet’s largest cities are situated near the ocean. For every 150 cubic miles of ice that are transferred from land to the sea, the global sea level rises by about a 16th of an inch. That may not sound like a lot, but consider the volume of ice now locked up in the planet’s three greatest ice sheets. If the West Antarctic ice sheet were to disappear, sea level would rise almost 19 feet; the ice in the Greenland ice sheet could add 24 feet to that; and the East Antarctic ice sheet could add yet another 170 feet to the level of the world’s oceans: more than 213 feet in all. (For comparison, the Statue of Liberty, from the top of the base to the top of the torch, is about 150 feet tall.)