"It gave it a pretty big nudge," Neal Young, an Australian Antarctic Division glaciologist, told The Associated Press news agency, speaking about the older iceberg.
The two icebergs are drifting together about 100 to 150km off eastern Antarctica following the collision on February 12 or 13, Young said.
"They are now floating right next to each other."
Each massive block of ice contains enough water to supply a fifth of the world's needs for an entire year.
Scientists said the impact of the incident may not be felt for decades or longer, but a slowdown in the production of colder, dense water could result in less temperate winters in the north Atlantic.
They said both natural cycles and man-made climate change can contribute to the collapse of ice shelves and glaciers.
However, David Santillo, a scientist with Greenpeace Research Laboratories in the UK, said evidence indicates the event is rare, but "entirely natural".
"That doesnt' mean that we shouldn't be concerned about it. It could have some far-reaching impact," he told Al Jazeera.
"The area in which these icebergs are located isn't usually an area where you would find a lot of sea ice.
"It could make it more difficult for the key species in those ecosystems to be able to find their food. They may have to travel farther.
"The second concern is that this is one of a few major areas around the globe that is important for the development of very cold, dense oxygen-rich water, which sinks to the sea floor and keeps the deep oceanswell-oxygenated.
"If this interferes with that process, by making the water less dense, that could have far reaching impacts on a ... global scale over many years."