homogeneity in the deep North Pacific. WOCE
hydrographic data allows local features to be more
closely defined, as in the Indian Ocean potential
vorticity fields mapped using WHP and historical
data (McCarthy and Talley, 1999). The Indian
Ocean potential vorticity field is zonal at all
depths in the tropics; at mid-latitudes the zonality
fills most of the mid-depth layer while at greater
depths contours of potential vorticity follow the
bathymetry; homogenization does not occur at any
depth or in any region.
Transport calculations
For heat and freshwater transport calculations, the
continuing battle to improve surface fluxes has not
yet been won, although significant progress in producing higher-quality flux data sets has occurred
in WOCE (Josey et al., 1999; WGASF, 2000). The
remaining large error bars on surface fluxes mean
that direct transport estimates based on in-situ
measurements remain the best. Heat and freshwater transport estimates from WHP sections and
from surface fluxes are summarized in Section 6.
These section-based works are preliminary, as
almost all are based on single section analyses
without an attempt at a unified circulation picture
for at least an entire basin. Basin-wide and global
transport estimates based on consistent analyses of
the complete data set will likely improve the current estimates, and will also make direct ocean
transport estimates available for many additional
sections.
7.1.2.2 Process studies
Dedicated local observational studies clarify issues
important for ocean circulation and hence oceanand climate-related modelling. WOCE process
studies have been carried out with multiple observational tools, many with integrated modelling
studies. Completed are the subduction experiment
in the eastern North Atlantic (Price, Chapter 5.3),
a mixing experiment in the same region (Toole
and McDougall Chapter 5.2), and an experiment
on abyssal circulation, upwelling and mixing in
the geographically restricted Brazil Basin (Hogg,
Chapter 4.5). Other regions that have been studied
intensively with respect to a specific process are
the Labrador Sea for convection (Lazier et al.,
Chapter 5.5), the Weddell Sea (Rintoul et al.,
Chapter 4.6), and flow through the Indonesian
passages (Gordon, Chapter 4.7). Many of these
latter experiments were carried out with both
WOCE and non-WOCE resources; all contribute
importantly to understanding ocean circulation
processes and hence the goals of WOCE.
A regional study of North Atlantic Deep Water
(NADW) formation in the subpolar North
Atlantic is in the synthesis phase. Field work was
started late in WOCE (in 1996) and is continuing,
now as part of CLIVAR and national research
programmes. Components of this work include
transformation of upper ocean waters in the subpolar gyre, inflow and outflow over the Greenland–Scotland ridge, flow into and out of the
Labrador Sea, and ongoing study of Labrador Sea
Water formation. Learning how the thick surface
layer changes properties, especially temperature
and salinity, is central to the overall NADW problem. It is apparent from the new observations that
this subpolar layer does not change properties in
the continuous and large-scale fashion suggested
by McCartney and Talley (1982) using a coarser
and non-synoptic data set; rather the North
Atlantic Current (subarctic front) and underlying
circulation following the topography provide a
complex circulation for the surface layer, with preferred regions of convection near topographic features (Talley, 1999b).
Exchange between the Nordic Seas and the
North Atlantic is a central practical problem for
basin- and global-scale ocean models, which do
not resolve straits sufficiently to model the physics
correctly there. This problem is described by
Saunders (Chapter 5.6). One thrust of the ongoing
NADW work is to describe as completely as possible the overflow and to model it theoretically and
with high-resolution numerical models. Recent
results presented at the WOCE North Atlantic
workshop show in particular the presence and
strength of eddies in the Denmark Strait, which
might influence interpretation of moored results
within the strait (Krauss and Käse, 1998; Käse,
2000; Käse and Oschlies, 2001).
7.1.2.3 Variability studies
WOCE goals include observing, where possible, the
ocean’s variability at time scales relevant for climate. There are many open questions, ranging from
simply characterizing the variability and its spatial
structure, to understanding its source and relationship to forcing. Thus in addition to the long-term
average circulation and water properties, studies
7.1 Towards a WOCE Synthesis
529
Talley, Stammer and Fukumori
hydrographic data allows local features to be more
closely defined, as in the Indian Ocean potential
vorticity fields mapped using WHP and historical
data (McCarthy and Talley, 1999). The Indian
Ocean potential vorticity field is zonal at all
depths in the tropics; at mid-latitudes the zonality
fills most of the mid-depth layer while at greater
depths contours of potential vorticity follow the
bathymetry; homogenization does not occur at any
depth or in any region.
Transport calculations
For heat and freshwater transport calculations, the
continuing battle to improve surface fluxes has not
yet been won, although significant progress in producing higher-quality flux data sets has occurred
in WOCE (Josey et al., 1999; WGASF, 2000). The
remaining large error bars on surface fluxes mean
that direct transport estimates based on in-situ
measurements remain the best. Heat and freshwater transport estimates from WHP sections and
from surface fluxes are summarized in Section 6.
These section-based works are preliminary, as
almost all are based on single section analyses
without an attempt at a unified circulation picture
for at least an entire basin. Basin-wide and global
transport estimates based on consistent analyses of
the complete data set will likely improve the current estimates, and will also make direct ocean
transport estimates available for many additional
sections.
7.1.2.2 Process studies
Dedicated local observational studies clarify issues
important for ocean circulation and hence oceanand climate-related modelling. WOCE process
studies have been carried out with multiple observational tools, many with integrated modelling
studies. Completed are the subduction experiment
in the eastern North Atlantic (Price, Chapter 5.3),
a mixing experiment in the same region (Toole
and McDougall Chapter 5.2), and an experiment
on abyssal circulation, upwelling and mixing in
the geographically restricted Brazil Basin (Hogg,
Chapter 4.5). Other regions that have been studied
intensively with respect to a specific process are
the Labrador Sea for convection (Lazier et al.,
Chapter 5.5), the Weddell Sea (Rintoul et al.,
Chapter 4.6), and flow through the Indonesian
passages (Gordon, Chapter 4.7). Many of these
latter experiments were carried out with both
WOCE and non-WOCE resources; all contribute
importantly to understanding ocean circulation
processes and hence the goals of WOCE.
A regional study of North Atlantic Deep Water
(NADW) formation in the subpolar North
Atlantic is in the synthesis phase. Field work was
started late in WOCE (in 1996) and is continuing,
now as part of CLIVAR and national research
programmes. Components of this work include
transformation of upper ocean waters in the subpolar gyre, inflow and outflow over the Greenland–Scotland ridge, flow into and out of the
Labrador Sea, and ongoing study of Labrador Sea
Water formation. Learning how the thick surface
layer changes properties, especially temperature
and salinity, is central to the overall NADW problem. It is apparent from the new observations that
this subpolar layer does not change properties in
the continuous and large-scale fashion suggested
by McCartney and Talley (1982) using a coarser
and non-synoptic data set; rather the North
Atlantic Current (subarctic front) and underlying
circulation following the topography provide a
complex circulation for the surface layer, with preferred regions of convection near topographic features (Talley, 1999b).
Exchange between the Nordic Seas and the
North Atlantic is a central practical problem for
basin- and global-scale ocean models, which do
not resolve straits sufficiently to model the physics
correctly there. This problem is described by
Saunders (Chapter 5.6). One thrust of the ongoing
NADW work is to describe as completely as possible the overflow and to model it theoretically and
with high-resolution numerical models. Recent
results presented at the WOCE North Atlantic
workshop show in particular the presence and
strength of eddies in the Denmark Strait, which
might influence interpretation of moored results
within the strait (Krauss and Käse, 1998; Käse,
2000; Käse and Oschlies, 2001).
7.1.2.3 Variability studies
WOCE goals include observing, where possible, the
ocean’s variability at time scales relevant for climate. There are many open questions, ranging from
simply characterizing the variability and its spatial
structure, to understanding its source and relationship to forcing. Thus in addition to the long-term
average circulation and water properties, studies
7.1 Towards a WOCE Synthesis
529
Talley, Stammer and Fukumori