GOSML: A Global Ocean Surface Mixed Layer Statistical Monthly
Climatology: Means, Percentiles, Skewness, and Kurtosis
Abstract
Here we discuss a global ocean surface mixed layer statistical monthly
climatology (GOSML) of depth, temperature, and salinity that includes
means; variances; 5th, 50th, and
95th percentiles; as well as skewness and kurtosis.
Ocean surface mixed layer properties are influenced by a wide variety of
factors that operate over a wide variety of time scales and gravity.
Mixed layer depths can shoal very quickly as a result of surface
heating, precipitation, or “slumping” of horizontal density gradients.
However, deepening the mixed layer in the presence of a strong
pycnocline requires substantial buoyancy loss or strong wind mixing,
which often takes more time. This pattern is clear in the annual cycle
monthly mixed layer depth values, with deepening in the fall much slower
than shoaling in the spring. The 95th percentile
values are chosen as a reasonable indicator of ventilation depth, robust
to extreme outliers. Mean mixed layer depths are on average 0.56 of
95th percentile mixed layer depths, with only 1% of
values below 0.31 and 1% above 0.81. Over 71% of mixed layer depth
distributions are skewed positive, usually when there are more shallow
mixed layer depths than not and deep mixed layers tails are strong.
Comparing 95th percentile depth conditions to mean
values shows in late winter temperatures are generally lower in the
subtropics and salinities generally higher in the subpolar regions,
consistent with the importance of temperature in the midlatitudes and
salinity in the higher latitudes in setting stratification.