Territorial claims in Antarctica are drawn along lines of longitude, which all converge at the South Pole, and many overlap.
This is probably because the continent is covered in ice, so there are 'no natural landforms' -- they exist but are not predictable in their visibility -- to be used to mark borders.
Australia claims a pie-shaped section of the Antarctica, but it does not belong to Australia. It's claim -- with all other claims -- were negated by the Antarctic Treaty.
Antarctica is not a possession of any country on earth, although several countries have made claims to pie-shaped slices of the continent.
Territorial claims on the Antarctic continent are all shaped like slices of a pie, and they all meet-- center -- at the South Pole, 90 degrees S. Claims follow lines of longitude, and some claims overlap each other.
Territorial claims follow lines of longitude that all terminate at the South Pole. You could say that these claims are pie-shaped. You can see a map showing the shape, below.
Antarctica is not 'split up'. The surface of the continent is trans-sected by the Trans-Antarctic Mountain Range, and often this demarcation separates east from west Antarctica. Nation-states have laid claim to Antarctic territory, in pie-shaped 'slices' that follow lines of longitude, all of which converge at the South Pole. Some of these claims overlap each other The Antarctic Treaty acknowledges all claims and holds them in abeyance, and prohibits future claims.
No country has scientific claims; all claimant countries exude territorial claims.
Argentina owns zero in Antarctica. Its claim overlaps other claims. All claims are held in abeyance by the Antarctic Treaty (1961).
None. No nation owns any part of Antarctica. Britain and other countries claim territories on the continent, and several other claims overlap the British claim. The British claim reaches between 20°W and 80°W. It is overlapped by claims by Chile and Argentina. All claims are pie-piece-shaped and extend south to the South Pole or 90°S.
New Zealand does not own any of Antarctica. There is an Antarctic Treaty, initiated in 1961, setting this continent aside for scientific purposes. This Treaty currently has about 50 national signatories. Any earlier claims of territory are set aside.
There is no agreement that 'splits up' Antarctica. Antarctica -- and all of earth south of 60 degrees South Latitude -- is governed by the Antarctic Treaty. This treaty negates all previous land claims and prohibits new land claims on the continent.
There are no states in Antarctica. It's all just one continent. There are different areas claimed by different countries and some of these claims overlap each other. Claims have no meaning, however, according to the Antarctic Treaty, which holds all claims in abeyance.
The Antarctic Treaty recognizes and holds in abeyance all existing territorial claims on Antarctica made by nation-states, and precludes any future claims.