  Solar sub-surface fluid topology provides an indirect approach to examine the
internal characteristics of active regions (ARs). Earlier studies have revealed
the prevalence of strong flows in the interior of ARs having complex magnetic
fields. Using the Doppler data obtained by the Global Oscillation Network Group
(GONG) project for a sample of 74 ARs, we have discovered the presence of steep
gradients in meridional velocity at depths ranging from 1.5 to 5 Mm in flare
productive ARs. The sample of these ARs is taken from the Carrington rotations
1980--2052 covering the period August 2001-January 2007. The gradients showed
an interesting hemispheric trend of negative (positive) signs in the northern
(southern) hemisphere, i.e., directed toward the equator. We have discovered
three sheared layers in the depth range of 0 - 10 Mm, providing an evidence of
complex flow structures in several ARs. An important inference derived from our
analysis is that the location of the deepest zero vertical vorticity is
correlated with the remaining life time of ARs. This new finding may be
employed as a tool for predicting the life expectancy of an AR.
