ABSTRACT
Using bottom pressure measurements and current meter measurements at
3500 m depth at twelve sites under the Gulf Stream near 68oW
daily optimally-interpolated (OI) maps have been constructed for
June 1988 to August 1990. Prior to mapping the pressure records were
leveled (referenced to the same absolute geopotential) using the
current measurements under the assumption that their mean fields are
geostrophic. The leveled pressures were subsequently used
together with the current measurements in a multivariate OI mapping
procedure.This procedure significantly reduced the mapping errors,
because both pressure and its (geostrophic) gradient are specified as
inputs. The mapped bottom pressure and current fields have typical mean
square errors of only 0.0005 dbar2 and 4 cm2
s-2 , compared to typical signal variances of
0.0035 dbar2
and 80 cm2 s-2. The daily maps of abyssal
pressure are used to identify the characteristic space-time structures
of dynamical processes. Examples are shown in which deep-level cyclones
spin up jointly with steep stationary troughs in the Gulf Stream and
deep anticyclones with steep propagating crests. Another sequence
of maps illustrates the propagation of topographic Rossby waves and
ring/stream interactions.
