Vertical motion at 700 m in the Gulf Stream main thermocline is comput
ed using the adiabatic heat equation and a combination of data from in
verted echo sounders and moored current meter measurements of T and (u
, v) at 400, 700, 1000, and 3500 m. Daily maps of all data on a regula
r grid were created using optimal estimation; from these maps the tend
ency and advection terms in the heat equation were calculated. The map
ped vertical motions w agree well with w observed contemporaneously al
ong isopycnal RAFOS float tracks. Strong events occur frequently withi
n the Gulf Stream: diagnosed vertical motions greater than 2 mm s(-1)
that persist for days are common, occurring roughly every week within
the 250-km mapped region. Upwelling and downwelling regions have horiz
ontal scales of about 100 km both along and across stream. Case studie
s and animation elucidate the relationship between meander properties
and the and amplitude of the w fields: typically, the largest ur is po
sitioned near the steepest thermocline slope, downwelling/upwelling oc
curs entering/exiting troughs, strongest vertical motions occur in slo
wly propagating features, and vertical motions are usually weaker for
rapidly propagating features. This observed dependence upon phase spee
d is opposite to predictions of recent kinematic and conceptual models
, The main contribution to observed w (and the factor missing in those
models) is the existence of strong abyssal flow, serving as a barotro
pic reference for the entire water column, with a component which may
flow orthogonal to the baroclinic front along sloping isopycnals. The
strongest vertical and cross-frontal components are usually associated
with slowly moving, or stalled, steep meanders, associated with which
abyssal cyclones or anticyclones have developed. The vertical motion
which is forced in these cases can significantly alter the vertical vo
rticity and/or frontal strength through tilting of the strong vertical
shear and of the strong vertical stratification. Vertical and cross-f
rontal transports of 5 Sv occur in steep meanders.