The Bowdoin Glacier in Greenland has been warming deep inside due to meltwater refreezing in crevasses near its base. This warming is happening faster than expected, indicating a significant heat source within the glacier. The researchers measured temperatures at different depths over three years and found an average temperature difference of 2.07 degrees Celsius between two boreholes. The englacial warming rate of up to 0.39 degrees Celsius per year suggests that the heat source is likely from meltwater refreezing in crevasses reaching the glacier's base.