An iceberg the size of Sydney has broken off of the Amery Ice Shelf in Antarctica, but freighters sailing about the Southern Hemisphere don't need to worry just yet.

"I wouldn't expect it to produce a big risk to shipping at the moment," said Dr. Sue Cook, an ice shelf glaciologist with the University of Tasmania's Institute of Marine and Antarctic Studies (IMAS), in an interview with the ABC.  "It's so large it should be easy to track and easy to plan where the iceberg is going to move."

The iceberg is now named D28, and it's 1,636-square-kilometers in size.  D28 calved off of an area of the ice shelf known as the "Loose Tooth" last Thursday, which scientists determined from satellite imagery.

"The calving will not directly affect sea level, because the ice shelf was already floating, much like an ice cube in a glass of water," said glaciologist Dr. Ben Galton-Fenzi of the Australian Antarctic Division (AAD).  "But what will be interesting to see is how the loss of this ice will influence the ocean melting under the remaining ice shelf and the speed at which the ice flows off the continent."

This event isn't necessarily related to global warming, however.  Scientists spotted the rift two decades again, and predicted it would separate in 2010-2015 - D28 is actually late.

"I am excited to see this calving event after all these years. We knew it would happen eventually, but just to keep us all on our toes, it is not exactly where we expected it to be," said Helen Amanda Fricker, from the Scripps Institution of Oceanography in the US.  "We don't think this event is linked to climate change; it's part of the ice shelf's normal cycle, where we see major calving events every 60-70 years."

But Dr. Cook in Tasmania says we should expect more icebergs to break off because of climate change.

"There are a number of different processes that'll happen. As waters around Antarctica warm up, they'll start thinning the ice shelves and making them more vulnerable to breaking up," she said, "Also you get increased surface melt on the ice shelves and that can get into fractures and forces them to expand."