Estimates of Mixed and Mixing Layer Depths from ASIP

Brian Ward, National University of Ireland, Galway (NUIG), School of Physics, Galway, Ireland, Graig Sutherland, University of Oslo, Dept. of Mathematics, Oslo, Norway, Anneke Ten Doeschate, NUI Galway, Ireland, Leonie Tabea Esters, National University of Ireland, Galway, AirSea Laboratory, Galway, Ireland and Kai H Christensen, Norwegian Meteorological Institute, Oslo, Norway
Abstract:
The ocean surface boundary layer (OSBL) is typically well mixed as a
result of different turbulent processes arising from the action of
wind, waves, and convection. The depth of the OSBL is controlled by
the availability of turbulence, and is characterised by vertically
uniform temperature, salinity, and density.

Methods to estimate the depth of the OSBL are derived from a density
(mixed layer depth MLD) or a dissipation profile (mixing layer depth
XLD), where the lengthscale is estimated using a specified threshold
value, typically 0.03 kg/m3 and 10e-9 W/kg, respectively. However,
these two methods often result in different depths, depending on the
conditions. It has been shown that the dissipation method is more
appropriate for deriving the depth to which the OSBL is uniform, as
this provides a direct estimate of the turbulence.

In this presentation we provide a comparison of XLD and MLD estimates
from the autonomous upwardly-rising OSBL profiler from several cruises
under a variety of conditions to investigate the possibility of
deriving XLD from the more widely available MLD.

Back to: Properties of the Ocean Surface that Directly Influence Air-Sea Exchange and Upper Ocean Dynamics III Posters