The meridian 45° west of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, Greenland, the Atlantic Ocean, South America, the Southern Ocean, and Antarctica to the South Pole.
In Greenland the meridian defines the borders of Avannaata, Qeqertalik, and Qeqqata municipalities with the Sermersooq municipality and the Northeast Greenland National Park.
The East Antarctic Ice Sheet (EAIS) lies between 45° west and 168° east longitudinally. It was first formed around 34 million years ago, and it is the largest ice sheet on the entire planet, with far greater volume than the Greenland ice sheet or the West Antarctic Ice Sheet (WAIS), from which it is separated by the Transantarctic Mountains. The ice sheet is around 2.2 km (1.4 mi) thick on average and is 4,897 m (16,066 ft) at its thickest point. It is also home to the geographic South Pole, South Magnetic Pole and the Amundsen–Scott South Pole Station.