BBC science correspondent David Shukman travelled to the Ayles Ice Island in the Canadian Arctic with cameraman Duncan Stone and scientists Luke Copland of the University of Ottawa and Derek Mueller of the University of Alaska Fairbanks. Here are their replies to a selection of readers' questions. They wrote the replies from the Eureka research station.
Iain McKerchar, Hook, UK
A Twin Otter took the team to the research station
Q: How do you justify using an aircraft, the engine of which pollutes the atmosphere, to go and look at a piece of ice-shelf? Even if you have tagged along with a scientific expedition, your additional weight and that of your crew requires additional fuel which means additional carbon dioxide, etc. in the atmosphere. I cannot see that your actions are justifiable.
David Shukman: I'm sorry you feel that way. But as the largest single ice break-up for 40 years, at a time of mounting concern about the dramatic retreat of sea ice and other developments associated with rapid warming in the Arctic, we believe that covering important and original scientific fieldwork into this event is justified. And all of us have offset the carbon cost of the flights or will when the final mileage is known.
Martyn Green, Hong Kong
Derek Mueller and Luke Copland work on your questions
Q: Can you outline some of the major problems you face when filming there - keeping warm while standing still to film, keeping batteries warm, charging batteries, condensation on camera lenses, etc. Basically, what is it like, compared with what you had expected?
Duncan Stone: Keeping warm is an issue when standing still, but most of the time I'm running around getting shots so overheating has become a problem for me. I'm wearing less than my colleagues and still taking off layers.
As for the camera, the batteries are lasting for less time as you would imagine, but I'm carrying plenty of them. I keep my main camera "cold" i.e. outside in a store room in a camera bag. I've got an indoor camera with me. All this, as you've suggested, to stop the lens and camera from misting or clogging up.
Cables have been a problem: they've become really brittle so I've had to be extra careful with them when coiling up.
Other problems have been trying to operate the camera with thick gloves, motion sickness while filming from so many planes and trying to get the correct exposure when everything is so white. The grease in the lens and the tripod have gone really thick so it's difficult to turn both of them.
I'm recording on both tape and external hard drive. The HD has been performing well so far with no problems. It's all pretty much as I expected.
Krishna Mulani, Houston, US
Q: What theories or hypothesis are you trying to prove on your expedition to the Island of Ice? Are you going to the island in hopes of understanding global warming?
Our correspondent David Shukman wraps up against the cold
David Shukman: You can never link a single event to global warming but everything that's happening in the Arctic suggests that warming did have a role in this massive break-up. If we do manage to land on the island, it will be a very weird experience.
Charlie Barker, Oxford, UK
Q: What is the direction of the tidal flows in the area and what is the prediction of the drift? Could it get down to the Atlantic and influence established currents such as the Gulf Stream? Good luck with the weather and I will plot your progress.
Dr Luke Copland: The Ice Island has been drifting to the west since it broke off, along the northern coast of Ellesmere Island. We expect this drift to continue as it is driven by a very large ocean current called the Beaufort Gyre that circulates the water in a clockwise direction over this side of the Arctic Ocean.
As this drift continues, the Ice Island may either get caught up in the islands of the NW part of the Canadian High Arctic, or if it stays in the Arctic Ocean it will ultimately float past northern Alaska, before heading back to the Canadian side of the Arctic across the North Pole. Past islands have completed up to three loops like this around the Arctic Ocean.
If it lasts long enough, the Ice Island will ultimately exit the Arctic Ocean through the gap between eastern Greenland and Svalbard into the north Atlantic. However, once any remnants reach the North Atlantic they would quickly melt due to the warm waters there. It may take several decades for the ice to exit the Arctic Ocean.
Craig Irving, Vernon, British Columbia
Q: I have been following the break-off of this piece since our Canadian science wing found it. With the overall dimensions I have been wondering about the depth of this 'berg, and the overall damage to the sea bed. Can you elaborate on these issues?
Dr Derek Mueller: We have estimated that this mass of ice is in the order of 40m thick.
Roughly 9/10ths of this is under the water. Currently the Ice Island is in very deep water and is not touching the sea bed. If it drifted into shallow water it could certainly scour the sea floor. This would be detrimental to any benthic (bottom dwelling) communities in its path!
Icebergs and thick sections of sea ice also scour the sea floor and leave large scars in the marine sediments. The scouring of ice is also a concern to engineers who have to account for this when planning pipelines and other structures in shallow waters.
Mark, Basingstoke, England
Q: How old is the ice this island is made of and how long will a piece of ice this huge take to melt? Is this type of thing being monitored from space? Is there a website where the general public can look at recent images of this kind of thing?
Dr Luke Copland: It is likely that the Ice Island was in place for at least 3000 years before it broke off. The actual age of the ice within it is probably a couple of hundred years old as new ice is normally continuously added to the ice shelf to replace the ice that is lost via surface melting and calving at the terminus.
However, there has been insufficient production of new ice recently, which is part of the reason why the ice shelf weakened and broke away.
The Ice Island is being regularly monitored by the Canadian Ice Service using satellite imagery. Most of this imagery comes from a Canadian satellite called Radar sat which is able to see through clouds and dark and can therefore monitor the Ice Island in any weather.
Regular updates of its position and satellite imagery can be found here on the website of the Canadian Ice Service.
Mark Mueller, Ottawa, Canada
Q: Derek, this is your father!
Can you say conclusively that the break-up of the ice shelves in the area where you are with the BBC crew is attributable to global warming?
My second question is: who among you is qualified to use a gun to protect yourselves against polar bears?
Derek Mueller: Dad, this is your son!
It would be difficult to demonstrate conclusively that any particular event is related to climate warming. Over the last century, the extent of ice shelves along the northern coast of Ellesmere Island has reduced by 90%.
Much of these changes actually occurred prior to the 1950s and was probably caused by warmer regional temperatures in the 1930s and 40s. In recent decades, scientists have noted a pronounced warming in the Arctic.
At the same time, we are observing further changes in the ice shelves that could be linked to the recent warming. These ice shelf break-up events may also be caused by changes in ocean temperature and currents and other factors.
However, the Ayles Ice Shelf break-up is also consistent with other indicators of climate warming in the Arctic, such as the reduction of sea ice extent, warming permafrost and melting of glaciers.
The most compelling evidence that the ice shelves are responding to climate change is that they are not regenerating from their disintegration over that last 100 years. This suggests that the present climate is not conducive to maintain ice shelves in this region and that any further warming will likely induce more change.
To answer your second question, Luke and I are both qualified and licensed to use a gun to deter polar bears. I should add that the risk of polar bear attack is very low and that we would use a gun only as a last resort.