The cores are collected by melting holes through the sea ice (or ice shelf) and then lowering a pipe through the ice, the water column, and drilling into the seafloor to sample the sediment below and bring these samples back to the surface for scientists to study.
The benefit of collecting these records from the Antarctic margin is that they record the primary evidence for the advance and retreat of the ice across the Antarctic margin and thereby can help to calibrate the records of climate from deepsea cores located far away from Antarctica.
Read the full article here:
ANDRILL Investigates Climate History of Antarctica – Discover Magazine (blog)