What ocean, intersected by the 30th Meridian, may also be an estuary of the Atlantic Ocean?
30th meridian west: The meridian 30° west of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, Greenland, the Atlantic Ocean, the Southern Ocean, and Antarctica to the South Pole. Arctic Ocean:  The International Hydrographic Organization (IHO) recognizes it as an ocean, although some oceanographers call it the Arctic Mediterranean Sea or simply the Arctic Sea, classifying it a mediterranean sea or an estuary of the Atlantic Ocean.
Arctic Ocean