Europe's Seas, From the Barents to the Azov

The Barents Sea opens the trail at the Arctic edge of Europe, north of Norway and Russia, and covers about 1.4 million square kilometers. Part of it is warmed by an extension of the Gulf Stream, so it stays ice-free longer than most Arctic waters, and its greatest recorded depth is 600 meters.

The Norwegian Sea lies in the northeastern Atlantic between Norway, Iceland and the Greenland Sea, and covers about 1.38 million square kilometers. It is far deeper than the Barents Sea, reaching 3,970 meters, and it carries warm Atlantic water northward into the Arctic.

The Skagerrak is the strait between Norway, Sweden and Denmark's Jutland peninsula, covering about 47,000 square kilometers. It connects the North Sea to the Kattegat and, beyond it, the Baltic, so it is the gateway the next stop depends on.

The Baltic Sea is a largely enclosed sea about 1,600 kilometers long, covering 377,000 square kilometers and bordered by nine countries. Its deepest point, 459 meters on the Swedish side, is modest beside the Norwegian Sea, and its low salinity makes it unlike the open ocean it connects to.

The Gulf of Bothnia is the northernmost arm of the Baltic, between Sweden and Finland. It is 725 kilometers long and covers 117,000 square kilometers, with a maximum depth of 295 meters, and heavy river inflow keeps its northern end close to fresh water.

The Gulf of Finland is the eastern arm of the Baltic, bordered by Finland, Estonia and Russia, with Saint Petersburg at its head. It is about 400 kilometers long and covers 30,000 square kilometers, and its maximum depth of 115 meters is much shallower than the Bothnian arm.

The English Channel separates southern England from northern France and joins the North Sea to the Atlantic. At about 75,000 square kilometers it is the smallest of the shallow seas around Europe's continental shelf, and its deepest point is 174 meters at Hurd's Deep.

The Bay of Biscay is a gulf of the northeastern Atlantic off western France and northern Spain, covering 223,000 square kilometers. Its shelf drops steeply to a maximum depth of 4,735 meters, the deepest water on this trail so far.

The Mediterranean Sea is almost entirely enclosed by land and reaches the Atlantic only through the Strait of Gibraltar. It is about 4,000 kilometers long and covers roughly 2.5 million square kilometers, with a maximum depth of 5,267 meters, and its coasts and islands linked the peoples of three continents.

The Adriatic Sea is an arm of the Mediterranean between the Italian and Balkan peninsulas, covering 138,600 square kilometers and about 800 kilometers long. It is split into three basins, with the shallow northern one and the deepest southern one reaching 1,233 meters.

The Aegean Sea lies between the Greek and Anatolian peninsulas and covers about 214,000 square kilometers. It is about 700 kilometers long, reaches 2,639 meters at its deepest, and is the first link in the chain of waters that leads to the Black Sea.

The Sea of Marmara lies wholly within Turkey and joins the Aegean to the Black Sea through the Dardanelles and the Bosphorus. At 11,350 square kilometers, it is considered the smallest sea in the world, yet its greatest depth is 1,370 meters, and Istanbul sits at its northeastern end.

The Black Sea lies between southeastern Europe and Asia Minor and covers 436,400 square kilometers, reaching 2,212 meters at its deepest. Below roughly 150 meters its water is anoxic, which preserves ancient shipwrecks in near-pristine condition.

The Sea of Azov ends the trail, joined to the Black Sea by the narrow Kerch Strait and fed chiefly by the Don River. It is 360 kilometers long and covers 39,000 square kilometers but is only 14 meters deep at its maximum, among the shallowest seas anywhere.