Scientists in Antarctica have recorded, for the first time, unusually warm water beneath a glacier (冰川)the size of Florida that is already melting and contributing to a rise in sea levels.
The researchers, working on the Thwaites Glacier, recorded water temperatures at the base of the ice of more than 2℃, above the normal freezing point. Critically, the measurements were taken at the glacier's grounding line, the area where it transforms from resting wholly on bedrock to spreading out on the sea as ice shelves. It is unclear how fast the glacier is getting worse: Studies have forecast its total collapse in a century or in a few decades. The presence of warm water in the grounding line may support estimates at the faster range.
That is worthy of attention because the Thwaites, along with the Pine Island Glacier and several smaller glaciers, acts as a brake on part of the much larger West Antarctic Ice Sheet, which if melted, would raise the world's oceans by more than a meter over centuries, an amount that would put many coastal cities underwater.
"Warm waters in this part of the world, as remote as they may seem, should serve as a warning to all of us about the potential terrible changes to the planet brought about by climate change," said David Holland, director of New York University's Environmental Fluid Dynamics Laboratory.
Glaciologists have previously raised alarm over the presence of warm water melting the Thwaites from below. This is the first time, though, that warm waters have been measured at the glacier's grounding line.
To observe activity beneath the glacier, Dr. Holland's team drilled a hole -about 30 centimeters wide and 600 meters deep-from the surface to the bottom and then placed equipment that measures water temperature and ocean turbulence, or the mixing of freshwater from the glacier and salty ocean water. Collecting the data took about 96 hours in subzero weather. Warm waters beneath the Thwaites are actively melting it, the team found.
While scientists may not yet be able to definitively predict how soon glaciers like the Thwaites will melt, human-caused climate change is a key factor. The biggest predictor of "how much ice we will lose and how quickly we will lose it, "Dr. Holland said, "is human action."
