Nearly 50 per cent of the glacier disintegrated over two months, a team of researchers found after analysing geophysical data and satellite imagery over time.
Hektoria retreated by about 25km between January 2022 and March 2023.
The retreat included about 8km lost between November and December 2022.
According to the team, led by researchers from the University of Colorado Boulder, the glacier's underlying flat bedrock enabled the glacier to go afloat after it substantially and rapidly thinned, causing it to calve quickly.
"When we flew over Hektoria in early 2024, I couldn't believe the vastness of the area that had collapsed," lead author Naomi Ochwat said.
"I had seen the fjord and notable mountain features in the satellite images, but being there in person filled me with astonishment at what had happened."
Ochwat said the team's use of satellite data at different time intervals was key to detecting how quickly the retreat happened.
"If we only had one image every three months, we might not be able to tell you that the glacier lost two and a half kilometres in two days," Ochwat said.
"Combining these different satellites, we can fill in time gaps and confirm how quickly the glacier lost ice."
Team member Ted Scambos said that the glacier's retreat "is a bit of a shock - his kind of lighting-fast retreat really changes what's possible for other, larger glaciers on the continent".
"If the same conditions set up in some of the other areas, it could greatly speed up sea level rise from the continent," Scambos said.
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