A subtropical ocean refers to a warm oceanic region near the Earth's equator, which is known for its pleasant climate and abundance of diverse marine life. Full definition
The North Pacific and North Atlantic subtropical ocean gyres are surface intensified, i.e. they don't reach down as deep into the ocean as the southern hemisphere gyres. (realclimate.org)
The surface subtropical oceans were estimated to have cooled by about 5C. (realclimate.org)
An idealised subtropical ocean basin forced by winds circling around a high pressure (anticyclonic) systems such as the Azores - Bermuda high develops a gyre circulation with slow steady flows towards the equator in the interior. (en.wikipedia.org)