30 
Sy, A. et al. (2002): Upper Ocean Climate Ship-of-Opportunity Programme of BSH - A Status Report 
The AX-11 time series from the upper 750 m of the subtropical and tropical Atlantic indicate a 
gradual warming from 1991 to 2000 (Figs. 18 bottom, 19). This coincides with conclusions by 
Yang (1999) who found a significant correlation between observed LSW thickness and the 
equatorial SST dipole, with a time lag of 5 years, and suggested a dynamic linkage between 
these two features. The long period of gradual warming which matches the lagged last period of 
intensified LSW formation (Sy et al., 1997) gives rise to the speculative question whether, and 
how, changes in LSW production affect the northward flow in the upper ocean. 
In order to take a step forward and overcome the limited analysis of our single SOOP lines AX-3 
and AX-11 towards a reconstruction of the North Atlantic circulation, we extended the data base 
by including additional XBT data from lines AX-2, AX-4, AX-7, AX-10, AX-20, AX-29 and AX-32 
which are to be combined with a dynamical model developed in the framework of CLIVAR at 
AWI, Bremerhaven, Germany. Model and measurements will be combined by applying a 
variational assimilation technique, also known as the adjoint method. For further information see 
www.awi-bremerhaven.de. 
The locations of these lines together with the 10-year mean field of heat content of the upper 
750 m is shown in Fig. 20. In Fig. 21 the corresponding annual time series of mean heat content 
anomalies are displayed. Compared to the mean, the upper North Atlantic Ocean was 
significantly colder from 1993 to 1995 and warmer from 1997 to 1999. No clear correlations 
between patterns can be found which could be indicative of the existence of propagation paths 
of anomalies of the upper ocean temperature field. 
3.3 Future plans 
Although the SOOP has been extremely cost-effective in scientific use and operational 
applications, it has been argued that it is time for a change of direction and a new focus. A plan 
for a new world wide network of some 3,000 autonomous profiling floats was developed in the 
late 90s (ARGO, 1998), which may affect the classical XBT network (Smith et al., 2000). This 
Array for Real-time Geostrophic Oceanography (ARGO) is now being implemented. 
Autonomous profiling float technology is a novel and very effective tool in sampling of the upper 
ocean climate variability, especially when combined with an appropriate XBT/XCTD SOOP 
network. Therefore, an ARGO proposal for the A-2 corridor has been drafted by BSH in 
conjunction with proposals by Institut für Meereskunde, Kiel, and Alfred Wegener Institute for 
Polar and Marine Research, Bremerhaven, and submitted to the German Ministry of Education 
and Research (BMBF) in October 2002. 
The main objectives of BSH’s ARGO proposal are 
the investigation of baroclinic variability in time and space in the transition zone between 
subtropical and subpolar gyres, 
improvement of a T/S climatology, 
evaluation of this ARGO contribution as a tool for ocean climate monitoring and, in this 
context, 
evaluation and optimisation of the AX-3 SOOP.