[1] The existence of mesoscale eddies was predicted by Henry Stommel in the 1960s,[3] but there was no way to observe them with traditional sampling methods.
[1] POLYGON was led by Leonid Brekhovskikh, from the Andreev Acoustics Institute, involving six research vessels and an extensive network of current meters.
The flow meters were disposed in a cross, spanning a region of 113 by 113 nautical miles dubbed the "polygon".
It looks as though some largescale eddy or wave disturbances were travelling across the POLYGON site from east to west.
[1] Walter Munk commented that the POLYGON experiment "ignited the mesoscale revolution [and that] MODE defined the new order" and that "oceanography has never been the same" since.