Kim, H-J. and A. J. Miller, 2007:
Did the thermocline deepen in the California Current
after the 1976-77 climate regime shift?
Journal of Physical Oceanography, 37, 1733-1739.
The 55-year CalCOFI dataset in the southern California Current reveals a
significant surface-intensified warming and stratification (buoyancy frequency) change
across the 1976-77 climate regime shift. However, the average depth of the thermocline,
defined as the maximum gradient of temperature, did not change significantly across the
regime shift. The maximum-gradient criterion for thermocline depth may be more
appropriate than following an isotherm because the isotherm necessarily deepens in the
presence of surface-intensified warming. As the surface heating changed the strength of
stratification, it also changed the slope of the nitrate-temperature relation for the middepth
waters (roughly 30m to 200m). Thus, the quality of upwelled water may have been
fundamentally altered after the shift.