The authors compute and compare vertical motions from three different
data sources within a 300-km square domain centered in the Gulf Stream
near 38 degrees N, 68 degrees W, and show that vertical motions infer
red from all three independent data sources and different analysis met
hods give similar results. The time derivatives of RAFOS float pressur
es on isopycnal surfaces are used to determine directly observed verti
cal motion w(RAF). Second, vertical motions are inferred from the heat
equation using measured temperature changes and the backing and veeri
ng of currents observed by a stack of current meters to produce w(CM).
Third, vertical motions are calculated from the quasigeostrophic vort
icity equation using geostrophic streamfunctions from inverted echo so
under measurements to produce w(IES) w(CM) agrees well with w(RAF) fro
m all floats that pass within 10 km of a current meter mooring. Daily
fields of w(IES) show very good coherence with time series of w(CM) fo
r periods longer than 16 d, but noise domination for periods shorter t
han 12 d. Typical magnitudes during strong ''events'' as estimated by
all three data sources are on the order of 1-2 mm s(-1) in regions nea
r the center of the Gulf Stream. The characteristic spatial and tempor
al scales of upwelling or downwelling features are clearly defined fro
m the horizontal maps and time series of w, and the location of these
vertical motions relative to Gulf Stream mesoscale features is discern
ed.