Dataset: Mixed layer depths from R/V Tangaroa cruise 61TG_3052 in the Southern Ocean in 1999 (SOIREE project)

SOIREE Mixed Layer Depth

The mixed-layer depth is defined as the maximum depth at which the sea-water

density is less than the density at 5m + 0.1 kg m-3. This picks up the top of

the seasonal pycnocline, but is insensitive to the weaker stratification that

occurred during the latter part of the experiment.

There is considerable cast-to-cast variation, suggesting the presence of internal

waves. Despite this it appears that the average mixed-layer depth decreased by 5-10m

between the 9th and the 16th of February, and then shoaled by a similar amount during

the remainder of the experiment. The apparent rapid decrease between the 8th and the

9th of February is possibly due to the inclusion of CTD stations on the transect towards

the experimental site, and may just reflect the general northward deepening of the surface

layer.

The development of thermal stratification within the surface layer is visible from Day 5.

This stratification is an order of magnitude weaker than the stratification within the pycnocline

Comments preserved from the original file:

Defined as the maximum depth at which the density is less than the density at 5m + 0.1 kg/m3.


Casts where the mixed layer depth is undefined, either due to bad data or because the

cast was too short, are assigned a value of -1.


This depth is typically at the top of the seasonal pycnocline. During the latter part of the

experiment there was persistent weak stratification at shallower depths.


The upcast column is 0 for downcasts and 1 for upcasts.