The findings, which will be published in the Journal of Geophysical Research, indicate that Hubbard’s advance is due to its large drainage basin extending far back into the snowy Saint Elias Mountains, and its large moraine, an accumulation of rocks and debris being scraped up and pushed along at the front of the glacier. The glacier is able to advance more easily across the top of the moraine since it does not have to grow as thick to stay grounded.
Twice in the past hundred years, Hubbard Glacier has advanced enough to where the moraine reaches Gilbert Point. Here it blocks off Russell Fjord, causing the fjord’s water levels to rise rapidly – the most recent in 2002 saw levels rise 0.24m (0.8ft) per day.
The natural dam didn’t last long – eventually the water pressure broke through and water levels returned to normal.
But based on current observations, Stearns estimates that the fjord could permanently close by 2043.
“Understanding Hubbard’s behaviour is scientifically interesting,” says Stearn. “But it also has immediate consequences for the [nearby] town of Yakutat,” which relies on marine life in the fjord.