From geology.com:

“We knew of such scour marks from places like the Antarctic and
Greenland. They arise when large ice sheets become grounded on the ocean
floor and then scrape over the ground like a plane with dozens of
blades as they flow. The remarkable feature of our new map is that it
indicates very accurately right off that there were four or more
generations of ice masses, which in the past 800,000 years moved from
the East Siberian Sea in a north-easterly direction far into the deep
Artic Ocean.” Quoted from the Alfred Wegener Institute press release.