Cline depth is defined as the midpoint of the segment connecting inflection
points that has the maximum slope. A cline cannot occur over a depth range
of less than 1m and also cannot be the shallowest segment. Violating both
conditions will thrown warnings though this function handles both
differently. Used mostly with wtr_layer
cline_calc(z_seg = z_seg, sigma_seg = sigma_seg)depth in metres; should be an increasing vector
parameter measured in the water column profile
the depth of the cline
Fiedler, Paul C. Comparison of objective descriptions of the thermocline. Limnology and Oceanography: Methods 8.6 (2010): 313-325.
wtr_layer()