Are they comparing the jagged coast line to the smooth equator?

Where are you getting the 53000 km number?

Interesting.

The perimeter of Antarctica's ice sheet is roughly 53,610 kilometers (33,312 miles). This is longer than the circumference of the Earth, which is about 40,070 kilometers (24,898 miles).

Explanation

The perimeter of Antarctica is longer than the Earth's circumference because Antarctica's ice sheet has many irregular sides.

This is an example of the "coastline paradox", which states that the closer you look at a coastline, the more complex its geometry becomes.

Measuring Antarctica's perimeter using less accurate methods will result in a shorter measurement than measuring it by tracing the complexity of its icy outcrops, inlets, and bays.

Same logic is why brains are wrinkled..... and not smooth.

Canada 200,000-260,000 km