Faster iceberg glacier in the world?

Answer 1

An iceberg is a body of ice floating in the ocean. A glacier is a land based 'river of ice' flowing from the mountains to its ultimate terminus, wherever that may be.

Thus they are very different things.

As to speed, like a river, that depends upon the gradient - in the cirques at the head, the velocity would be quite high, but slowing as the glacier grew and its gradient shallowed.

Answer 2

The fastest iceberg-producing glacier in the world is likely Jakobshavn Glacier in Greenland. This glacier flows at a rate of about 45 meters per day, calving large icebergs into the ocean. Its fast flow rate and calving activities have made it a subject of scientific interest and concern regarding climate change impacts.