The meridian 40° 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.

The 40th meridian west forms a great circle with the 140th meridian east.

Part of the 40th meridian west, from 22.3°N to 45°N, serves as the boundary between the New York and Santa Maria Oceanic flight information regions.

From Pole to Pole Starting at the North Pole and heading south to the South Pole, the 40th meridian west passes through:

{| class="wikitable plainrowheaders" ! scope="col" width="120" | Co-ordinates ! scope="col" | Country, territory or sea ! scope="col" | Notes |- | style="background:#b0e0e6;" | ! scope="row" style="background:#b0e0e6;" | Arctic Ocean | style="background:#b0e0e6;" | |- | style="background:#b0e0e6;" | ! scope="row" style="background:#b0e0e6;" | Lincoln Sea | style="background:#b0e0e6;" |

! scope="row" |

| style="background:#b0e0e6;" | ! scope="row" style="background:#b0e0e6;" | Atlantic Ocean | style="background:#b0e0e6;" | |-valign="top" | ! scope="row" | | Ceará Pernambuco — from Bahia — from Minas Gerais — from Bahia — from Espírito Santo — from |- | style="background:#b0e0e6;" | ! scope="row" style="background:#b0e0e6;" | Atlantic Ocean | style="background:#b0e0e6;" | |- | style="background:#b0e0e6;" | ! scope="row" style="background:#b0e0e6;" | Southern Ocean | style="background:#b0e0e6;" | |-valign="top" | ! scope="row" | Antarctica | Claimed by both (Argentine Antarctica) and (British Antarctic Territory)

See also 39th meridian west 41st meridian west

References