Fluvial paleohydrology provides a link between solar variability and t
errestrial climate during the last two millennia by revealing progress
ive changes in the degree of seasonality which reflect latitudinal shi
fts in climatic belts. A latitudinally diachronous phase of channel de
position which prevailed in AD 300-1850 in Eurasia between 45 degrees
and 25 degrees N indicates more equable stream discharges prompted by
a temporary southward displacement of the Atlantic depression zone. A
similar effect in central Mexico, between 18 degrees and 28 degrees N,
points to changes in the contribution of winter and autumn rains to t
he annual total which may stem from latitudinal shifts in the high-pre
ssure cells. The radiocarbon evidence suggests that the displacements
coincided with an increase in solar activity that reached a maximum in
about AD 600. The proposed association is consistent with evidence fr
om 1948-1966 for increased frontal activity in the North Atlantic duri
ng sunspot maxima, although it is not yet clear whether the process wa
s mediated by UV absorption in the lower stratosphere or by the flux o
f MeV-GeV particles.