(Chong et al., 2000). Variations in the geostrophic
transport through the Indonesian Throughflow
based on XBTs show a mean of 5 Sv and a large
seasonal and interannual component, with the
transport reaching as high as 12 Sv (Meyers et al.,
1995), the latter in agreement with current meter
measurements in Makassar Strait (Gordon et al.,
1999a; see also Gordon, Chapter 4.7).
Monitoring the transport of the Kuroshio south
of Japan has been carried out with in-situ current
and hydrographic observations (WOCE PCM5
array) and TOPEX/POSEIDON altimetry data
(Imawaki et al., 1997, 2000a, Fig. 7.3.11). The 7year long record (1992–99) shows a mean transport of 57 Sv with large variability. Of this, 42 Sv
flows on through, excluding recirculations, and
has only a small seasonal signal compared with the
transport of the western boundary current inferred
with the theory for a wind-driven, flat-bottom
ocean. Thus most of the variability of the 57 Sv is
due to variations in the recirculation.
Variations in production rates and properties of
various components of the NADW cell in the
North Atlantic have been studied using WOCE
and historical data. Some studies have employed
current meter arrays in strategic locations such as
the Denmark Strait Overflow and most include
repeat hydrography. These studies are continuing
as part of CLIVAR, and should be a part of any
climate-monitoring system.
Interannual to decadal variation in water properties have been studied in most oceans where
there are repeat hydrographic data, including considering the WOCE survey as a 1990s ‘data point’,
for comparison with previous decades (Dickson
et al., Chapter 7.3).
Because the mid-latitude North Atlantic is the
seat of a major decadal climate phenomenon, the
North Atlantic Oscillation (NAO), considerable
effort has been given to characterizing upper ocean
anomalies of temperature and salinity in the North
Atlantic, their relation to circulation, and relation
to the NAO. Hansen and Bezdek (1996) and
Sutton and Allen (1997) demonstrated the propagation of surface temperature anomalies originating near the western boundary eastward with the
North Atlantic Current.
Labrador Sea Water (LSW) is a major component of the NADW that departs southward from
the North Atlantic into the southern hemisphere.
Ongoing hydrographic work along a section in the
Labrador Sea during WOCE has continued the
time series started as Ocean Weather Station
Bravo, but with coast-to-coast coverage including
the boundary currents. Major shifts in LSW properties (temperature, salinity and thickness) were
apparent from earlier data, but the shifts towards
fresher and colder LSW in the 1990s were especially large (Lazier, 1995). The response of LSW
production and properties to the NAO both
within the Labrador Sea and downstream several
years later in the subtropical gyre has been clearly
demonstrated (Curry et al., 1998), with LSW thinning and warming when the NAO index decreases,
and vice versa. Sy et al. (1997) showed that the
entire subpolar North Atlantic at mid-depth
responded within 5 years to changes in convection
properties in the Labrador Sea. Koltermann et al.
(1999) compare mass, heat and freshwater transports in the North Atlantic for the 1950s, 1980s
and 1990s, concluding that there was highest
northward transport of warm water and southward
transport of deep water in the 1980s, coinciding
with a decrease in production and transport of
Labrador Sea Water.
Time series at point locations were continued
during WOCE at several locations, including at
Bermuda and at Ocean Weather Stations Mike
(Norwegian Sea) and Papa (northeast Pacific). A
new time series was established at Hawaii. Ongoing hydrographic work in the western North
Pacific continues long-time-series hydrographic
sections there. Repeat sections have also been
established in the Southern Ocean at key locations
crossing the Antarctic Circumpolar Current. Many
of the results obtained from incorporation of the
WOCE time series, and from considering the
WOCE one-time survey as a decadal data point,
are described by Dickson et al. (Chapter 7.3).
7.1.2.4 Climatologies and atlases
The WOCE observational programmes produce
both basic data sets and averaged fields (climatologies). The latter will be substantial improvements
to currently available climatologies and will serve as
a basic description of the mean ocean state, helping
to improve and initialize circulation models. Averaged fields include means over different time
periods and regions, and various sets of statistics.
These statistics are necessary for the state estimation efforts described below, which will use basic
data for the most part rather than climatological
SECTION 7 INSIGHTS FOR THE FUTURE
532
transport through the Indonesian Throughflow
based on XBTs show a mean of 5 Sv and a large
seasonal and interannual component, with the
transport reaching as high as 12 Sv (Meyers et al.,
1995), the latter in agreement with current meter
measurements in Makassar Strait (Gordon et al.,
1999a; see also Gordon, Chapter 4.7).
Monitoring the transport of the Kuroshio south
of Japan has been carried out with in-situ current
and hydrographic observations (WOCE PCM5
array) and TOPEX/POSEIDON altimetry data
(Imawaki et al., 1997, 2000a, Fig. 7.3.11). The 7year long record (1992–99) shows a mean transport of 57 Sv with large variability. Of this, 42 Sv
flows on through, excluding recirculations, and
has only a small seasonal signal compared with the
transport of the western boundary current inferred
with the theory for a wind-driven, flat-bottom
ocean. Thus most of the variability of the 57 Sv is
due to variations in the recirculation.
Variations in production rates and properties of
various components of the NADW cell in the
North Atlantic have been studied using WOCE
and historical data. Some studies have employed
current meter arrays in strategic locations such as
the Denmark Strait Overflow and most include
repeat hydrography. These studies are continuing
as part of CLIVAR, and should be a part of any
climate-monitoring system.
Interannual to decadal variation in water properties have been studied in most oceans where
there are repeat hydrographic data, including considering the WOCE survey as a 1990s ‘data point’,
for comparison with previous decades (Dickson
et al., Chapter 7.3).
Because the mid-latitude North Atlantic is the
seat of a major decadal climate phenomenon, the
North Atlantic Oscillation (NAO), considerable
effort has been given to characterizing upper ocean
anomalies of temperature and salinity in the North
Atlantic, their relation to circulation, and relation
to the NAO. Hansen and Bezdek (1996) and
Sutton and Allen (1997) demonstrated the propagation of surface temperature anomalies originating near the western boundary eastward with the
North Atlantic Current.
Labrador Sea Water (LSW) is a major component of the NADW that departs southward from
the North Atlantic into the southern hemisphere.
Ongoing hydrographic work along a section in the
Labrador Sea during WOCE has continued the
time series started as Ocean Weather Station
Bravo, but with coast-to-coast coverage including
the boundary currents. Major shifts in LSW properties (temperature, salinity and thickness) were
apparent from earlier data, but the shifts towards
fresher and colder LSW in the 1990s were especially large (Lazier, 1995). The response of LSW
production and properties to the NAO both
within the Labrador Sea and downstream several
years later in the subtropical gyre has been clearly
demonstrated (Curry et al., 1998), with LSW thinning and warming when the NAO index decreases,
and vice versa. Sy et al. (1997) showed that the
entire subpolar North Atlantic at mid-depth
responded within 5 years to changes in convection
properties in the Labrador Sea. Koltermann et al.
(1999) compare mass, heat and freshwater transports in the North Atlantic for the 1950s, 1980s
and 1990s, concluding that there was highest
northward transport of warm water and southward
transport of deep water in the 1980s, coinciding
with a decrease in production and transport of
Labrador Sea Water.
Time series at point locations were continued
during WOCE at several locations, including at
Bermuda and at Ocean Weather Stations Mike
(Norwegian Sea) and Papa (northeast Pacific). A
new time series was established at Hawaii. Ongoing hydrographic work in the western North
Pacific continues long-time-series hydrographic
sections there. Repeat sections have also been
established in the Southern Ocean at key locations
crossing the Antarctic Circumpolar Current. Many
of the results obtained from incorporation of the
WOCE time series, and from considering the
WOCE one-time survey as a decadal data point,
are described by Dickson et al. (Chapter 7.3).
7.1.2.4 Climatologies and atlases
The WOCE observational programmes produce
both basic data sets and averaged fields (climatologies). The latter will be substantial improvements
to currently available climatologies and will serve as
a basic description of the mean ocean state, helping
to improve and initialize circulation models. Averaged fields include means over different time
periods and regions, and various sets of statistics.
These statistics are necessary for the state estimation efforts described below, which will use basic
data for the most part rather than climatological
SECTION 7 INSIGHTS FOR THE FUTURE
532