Mode water

Relatively thick mixed layers are also found in the subtropical mode water areas near the separated western boundary currents.

These variations in these near-surface water masses, in temperature, salinity, density and thickness, are linked to surface forcing changes, although in some cases the connection is not yet obvious.

For example, Suga and Hanawa[10] show as the seasons progress, mode water moves away from the formation area and sometimes becomes permanently capped.

To detect the mode water we can use the minimum value in the vertical gradient of potential density, or equivalently in the Brunt–Väisälä frequency.

Dynamically, mode waters also control potential vorticity and baroclinity in the subtropical North Atlantic.