An iceberg four miles long has begun threatening a village in Greenland after it broke off from a glacier.
There are fears that if the iceberg splits in two it could create a tsunami effect.
New York University professor David Holland, an expert in atmospheric and ocean science, said it is "the largest event we’ve seen in over a decade in Greenland".
A video of the incident was taken by his wife, Denise Holland of New York University’s environmental fluid dynamics laboratory.
They camped by the Helheim Glacier for weeks to collect data to better project sea level changes.
Mr Holland said the time-lapse video, speeded up 20 times, shows "3% of the annual ice loss of Greenland occur in 30 minutes".
"It sounded like rockets going off," he said, describing it as "a very complex, chaotic, noisy event".
While the couple is studying Greenland, he said that "the real concern is in Antarctica, where everything is so big the stakes are much higher".
In north-western Greenland, another large iceberg has apparently grounded on the sea floor near the village of Innarsuit.
Residents with houses near the shore are prepared to evacuate if necessary.