  We test recent claims that the polar field at the end of Cycle 23 was
weakened by a small number of large, abnormally oriented regions, and
investigate what this means for solar cycle prediction. We isolate the
contribution of individual regions from magnetograms for Cycles 21, 22 and 23
using a 2D surface flux transport model, and find that although the top ~10% of
contributors tend to define sudden large variations in the axial dipole moment,
the cumulative contribution of many weaker regions cannot be ignored. In order
to recreate the axial dipole moment to a reasonable degree, many more regions
are required in Cycle 23 than in Cycles 21 and 22 when ordered by contribution.
We suggest that the negative contribution of the most significant regions of
Cycle 23 could indeed be a cause of the weak polar field at the following cycle
minimum and the low-amplitude Cycle 24. We also examine the relationship
between a region's axial dipole moment contribution and its emergence latitude,
flux, and initial axial dipole moment. We find that once the initial dipole
moment of a given region has been measured, we can predict the long-term dipole
moment contribution using emergence latitude alone.
