By Hanne Aavang
Over the centuries, millions of visitors have come to Skagen to witness an extraordinary wonder of nature: the “two seas” phenomenon. At the tip of Skagen is Grenen beach, where the Skagerrak and Kattegat seas meet in eternally clashing waves.
Kattegat flows into the Baltic Sea, and Skagerrak into the North Sea. Their convergence at Grenen creates unique conditions for wave interaction, currents and sediment transport.
The seas have a marginal difference in saline content and water density. Skagerrak is saltier than Kattegat due to its proximity to the Atlantic Ocean and the fact that Kattegat is diluted by the Baltic Sea, which has a lower saline level.
At times the unique wave and sand interactions* at Grenen attain a vehemence that makes for spectacular viewing from the shore. Massive quantities of sand are transported along the western and northern coast toward Grenen. Part of this sediment—approximately one million cubic meters per year—is deposited on the northern coast, gradually forming new dunes from layers of sand and seabed material.
Waves continually rise from both sides and break into each other at the end of the peninsula on Skaw Spit, a sand reef that extends almost a nautical mile into the sea. As Skaw Spit is curved like a dog’s tail, the effect is peculiar: the tail seems to wag back and forth in response to the wind and sea currents. You never really know what Grenen will look like, and it is always exciting to see it time and again.
Within the dynamic waters of the two seas, fish and ocean mammals thrive; whales and seals are often spotted at Grenen.
—Hanne Aavang is a guide at Skagens Museum.
*The unique wave interactions off Grenen Beach served as the inspiration for our new wave link bands as well as our brand logo.