Sy, A. et al. (2002): Upper Ocean Climate Ship-of-Opportunity Programme of BSH - A Status Report 
9 
2.1 North Atlantic line AX-3 
Line AX-3 from the English Channel to the Grand Banks (Halifax/New York) has been operated 
by BSH as a high density line almost without any serious problems since 1988 (Fig. 3). The 
WOCE related programme was funded by the German Ministry of Education and Research 
(BMBF) until the end of 1997. After that period, funding from different sources has allowed, and 
hopefully will continue to allow, these measurements to be carried out as part of BSH's 
contribution to the GOOS climate module (see section 3). 
From the start of the 
programme in 1988, 
measurements have been 
carried out regularly until 
now. In 2000, after 12 years 
of continuous SOOP activity 
(5730 XBT profiles), the 
German container vessel 
"Köln Express" (DAKE, 
9VBL) changed service and 
was replaced by “Bonn 
Express” (DGNB, Fig. 4). 
XBT measurements along 
this line were supplemented 
in 1998, 2000 and 2002 
each by two deep and 
very closely spaced XBT 
sections (resolution 15 nm 
or better, 2000 m depth 
range) carried out by BSH’s 
RV “Gauss” (DBBX). 
Fig. 4: CMS “Bonn Express” operated by 
Hapag-Lloyd, Hamburg, Germany 
A Sippican MK-12 unit and NOAA's SEAS IV (rev. 4.54) software are used for data acquisition 
and transmission. Most transects have a resolution of better than 40 nautical miles (Fig. 5). We 
replaced Sippican’s Deep Blue probes (800 m depth range) in 1995 by the new Fast Deep type 
as a standard because these modified T-5 probes are capable of covering the upper 1200 m at 
a ship's speed of 20 knots. In this way, systematic monitoring of the thermal field in the upper 
kilometre has become possible (WCRP-11, 1988), which allows the Mode Water temperature to 
be measured in the seasonally deep mixed upper layer of the subpolar North Atlantic Ocean as 
far down as the underlying thermocline, providing information on the baroclinicity of this layer. 
To estimate heat transports, measurements using expendable CTD probes (XCTD) have been 
carried out occasionally since 1992. 
So far, the line has been kept operational almost without interruptions. However, data quality 
problems appeared in late 1998 which impeded the programme seriously due to an increased 
probe failure rate exceeding 30 % (see data decrease in Fig. 3). Fast Deep probe failures were 
wire related and occurred as wire stretching, constant signals and premature wire breaks (see 
also section 2.2). After probe replacements (warranty) had been made in October 1999, the 
probe failure rate again dropped to the previous level of about 5 %. No unusual quality 
problems with this probe type have been observed since then.