The PIG now contributes more to rising sea level than any other ice stream on the planet.
It is believed that this was first been triggered by a period of strong warming of West Antarctica, associated with El Nino activity.
This weather system caused a warm ocean cavity to open beneath the glacier in 1945, according to the study, and eventually unground the glacier from it’s secure footing on a ridge in 1970.
Since then, the erosion has been thinning the glacier by as much as a metre per year and made it one of the largest potential sources of rising sea levels, according to the British Antarctic Survey.
Several models suggest that unstable and irreversible retreat of the grounding line is underway, changes which are regarded by experts as unprecedented in thousands of years.
Melting into the Amundsen Sea, the PIG drains a region of the West Antarctic ice sheet as big as two-thirds the size of the United Kingdom.
Dr James Smith, told BBC News: “This glacier used to be pinned to a ridge and once it moved away from that ridge, it started to retreat rapidly; and without other pinning points it could continue to retreat rapidly inland, contributing significantly to global sea level.”