The Kelp Highway

It is now known that seafaring peoples living in the Ryukyu Islands and Japan near the height of the last glacial period (about 35,000 to 15,000 years ago) adapted to cold waters comparable to those found today in the Gulf of Alaska. From Japan, they may have migrated northward through the Kurile Islands, to the southern coast of Beringia (ancient land bridge between what is now Siberia and Alaska), and into the Americas.

ScienceDaily