Question: What ocean, intersected by the 30th Meridian, may also be an estuary of the Atlantic Ocean?

full_context: Document 1: 80th meridian west: The meridian 80° west of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, North America, the Atlantic Ocean, the Caribbean Sea, Central America, South America, the Pacific Ocean, the Southern Ocean, and Antarctica to the South Pole.
Document 2: 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.
Document 3: 180th meridian: The 180th meridian or antimeridian is the meridian 180° east or west of the Prime Meridian, with which it forms a great circle dividing the earth into the Western and Eastern Hemispheres. It is common to both east longitude and west longitude. It is used as the basis for the International Date Line because it mostly passes through the open waters of the Pacific Ocean. However, the meridian passes through Russia and Fiji as well as Antarctica.
Document 4: 78th meridian west: The meridian 78° west of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, North America, the Atlantic Ocean, the Caribbean Sea, Central America, South America, the Pacific Ocean, the Southern Ocean, and Antarctica to the South Pole.
Document 5: North American Arctic: The North American Arctic comprises the northern portions of Alaska (USA), Northern Canada and Greenland. Major bodies of water include the Arctic Ocean, Hudson Bay, the Gulf of Alaska and North Atlantic Ocean. The western limit is the Seward Peninsula and the Bering Strait. The southern limit is the Arctic Circle latitude of 66° 33’N, which is the approximate limit of the midnight sun and the polar night.
Document 6: Arctic: The Arctic ( or ) is a polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Alaska (United States), Northern Canada, Finland, Greenland (Denmark), Iceland, Norway, Russia and Sweden. Land within the Arctic region has seasonally varying snow and ice cover, with predominantly treeless permafrost-containing tundra. Arctic seas contain seasonal sea ice in many places.
Document 7: Territorial claims in the Arctic: The Arctic consists of land, internal waters, territorial seas, exclusive economic zones (EEZs) and high seas. All land, internal waters, territorial seas and EEZs in the Arctic are under the jurisdiction of one of the five Arctic coastal states: Canada, Norway, Russia, Denmark (via Greenland), and the United States. International law regulates this area as with other portions of the Earth.
Document 8: 81st meridian west: The meridian 81° west of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, North America, the Atlantic Ocean, the Caribbean Sea, Central America, the Pacific Ocean, South America, the Southern Ocean, and Antarctica to the South Pole.
Document 9: Greenland Sea: The Greenland Sea is a body of water that borders Greenland to the west, the Svalbard archipelago to the east, Fram Strait and the Arctic Ocean to the north, and the Norwegian Sea and Iceland to the south. The Greenland Sea is often defined as part of the Arctic Ocean, sometimes as part of the Atlantic Ocean. However, definitions of the Arctic Ocean and its seas tend to be imprecise or arbitrary. In general usage the term "Arctic Ocean" would exclude the Greenland Sea. In oceanographic studies the Greenland Sea is considered part of the Nordic Seas, along with the Norwegian Sea. The Nordic Seas are the main connection between the Arctic and Atlantic oceans and, as such, could be of great significance in a possible shutdown of thermohaline circulation. In oceanography the Arctic Ocean and Nordic Seas are often referred to collectively as the "Arctic Mediterranean Sea", a marginal sea of the Atlantic.
Document 10: Arctic realm: The Arctic realm is one of the planet's twelve marine realms, as designated by the WWF and Nature Conservancy. It includes the coastal regions and continental shelves of the Arctic Ocean and adjacent seas, including the Arctic Archipelago, Hudson Bay, and the Labrador Sea of northern Canada, the seas surrounding Greenland, the northern and eastern coasts of Iceland, and the eastern Bering Sea.
Document 11: Longitude: Longitude ( or , Australian and British also ), is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees and denoted by the Greek letter lambda (λ). Meridians (lines running from the North Pole to the South Pole) connect points with the same longitude. By convention, one of these, the Prime Meridian, which passes through the Royal Observatory, Greenwich, England, was allocated the position of zero degrees longitude. The longitude of other places is measured as the angle east or west from the Prime Meridian, ranging from 0° at the Prime Meridian to +180° eastward and −180° westward. Specifically, it is the angle between a plane containing the Prime Meridian and a plane containing the North Pole, South Pole and the location in question. (This forms a right-handed coordinate system with the z axis (right hand thumb) pointing from the Earth's center toward the North Pole and the x axis (right hand index finger) extending from Earth's center through the equator at the Prime Meridian.)
Document 12: North America: North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere; it is also considered by some to be a northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea.
Document 13: Arctic cooperation and politics: Arctic cooperation and politics are partially coordinated via the Arctic Council, composed of the eight Arctic nations: the United States of America, Canada, Iceland, Norway, Sweden, Finland, Russia, and Denmark with Greenland and the Faroe Islands. The dominant governmental power in Arctic policy resides within the executive offices, legislative bodies, and implementing agencies of the eight Arctic nations, and to a lesser extent other nations, such as United Kingdom, Germany, European Union and China. NGOs and Academia play a large part in Arctic policy. Also important are intergovernmental bodies such as the United Nations (especially as relates to the Law of the Sea Treaty) and NATO.
Document 14: 79th meridian west: The meridian 79° west of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, North America, the Atlantic Ocean, the Caribbean Sea, Central America, South America, the Pacific Ocean, the Southern Ocean, and Antarctica to the South Pole.
Document 15: Arctic Ocean: The Arctic Ocean is the smallest and shallowest of the world's five major oceans. 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. Alternatively, the Arctic Ocean can be seen as the northernmost part of the all-encompassing World Ocean.
ground_truth: Arctic Ocean