WFP. Ref. No.: 	AR07E
Last Updated: 	August 18, 1991

Ship name:		R/V TYRO
Cruise No.:		91/1
ExpoCode:		64TR91_1

Dates:		

Dep Den Helder	Apr  8, 1991
Arr Reykjavik  	May  1, 1991
Dep Reykjavik  	May  2, 1991
Arr Den Helder 	May 16, 1991

Chief Scientist: Hendrik M. van Aken 

Via the North Sea, the Straits of Dover, the English Channel an the Irish Sea 
the ship sailed towards the shelf area northwest of the Irish Republic. In the 
Irish Sea a test station was carried out in order to shake down the CTD system 
and to obtain water for a test of the analytical instruments on board. 

In the morning of 12 April, the first CTD-station was occupied near 55 45' N, 9 
W, the first way point of section AR7E of the WOCE Hydrographic Programme.  The 
CTD-programme was continued while R.V. TYRO crossed the Rockall Bank and the 
Rockall-Hatton Plateau.  The normal station distance was 30 nautical miles, but 
in parts of the section with steep topography, this distance was reduced to 15 
miles, in accordance with the recommendations in the WHP operational plans.  
While the first 4 stations the CTD-mounted oxygen sensor gave unreliable or no 
results, from station 9 onward, after the repairments the results seem to be 
more reliable.  On the western side of the Hatton Bank the first of 4 ARGOS-
drifters was launched.

In the night of 14 to 15 April section AR7E was left temporarily in order to 
recover two moorings, deployed nearby in 1990.  Sediment trap mooring STRAP II 
was recovered successfully on 15 April.  The upper 2 traps had functioned 
faultless but, due to a rotation failure, the deepest trap collected only for 9 
out of 20 programmed sampling periods.  Current meter mooring IB90/3 was 
recovered successfully on 16 April.  CTD survey along 20 W (section a) could 
start.  Due to favorable weather conditions, this section was finished shortly 
before midnight 29 April at 60 N, 20 W.  

May 2, course was set to station 62 on the Reykjanes Ridge.  From station 71 on 
the Reykjanes Ridge course was set across the Iceland Basin (section b) towards 
the Hatton Bank (section e) where we arrived in the afternoon of 7 May (station 
95).  From the Hatton Bank course was set towards the Icelandic shelf along the 
17 W meridian (section f).  This CTD section was temporarily interrupted because 
of bad weather.  Thereafter two zigzag CTD sections (g & h) were carried out 
from the Icelandic shelf towards the 500 m line on the Faroe-Iceland Ridge.  
Finally from the Faroe-Iceland Ridge towards Lousy Bank and from Lousy Bank 
towards the Hatton Bank.  CTD programme was finished at station 144.  
Summary of observations


During the cruise the following observations have been carried out: 

€	continuous underway recording of position, meteorological and sea surface 
	parameters and echo sounder depths 

€	recordings of CTD-profiles as well as water sampling with a 24 bottle 
	Rosette sampler 

€	6 hourly meteorological observations, sent as OBS messages into the GTS 
	network 

€	launch of 4 ARGOS buoys

€	recovery of 4 current meter moorings and l mooring with sediment traps 

ARGOS drifters

During the first leg of the cruise 4 ARGOS-drifter have been launched according 
to the following: 

ARGOS drifters launched

Date
time (UTC)
Latitude
Longitude
PTT Nr.
14-04-91
21.08
57 30.3'N
20 07.9'W
8523
17-04-91
05.20
57 40.0'N
21 03.2 W
8521
17-04-91
16.43
57 56.7'N
22 46.2'W
8524
18-04-91
02.01
58 13.6'N
24 34.8'W
8522



CTD observations

During the cruise CTD observations have been carried out with a Neil Brown MkIII 
CTD.  The data have been recorded with a frequency of 16 Hz.  The temperature 
sensor consisted of an electronically combined high precision Pt 100 sensor and 
a fast thermistor. 

During the cruise it turned out that for temperatures below 2 C the temperature 
calibration was slightly temperature dependent due to a temperature dependent 
effect in the power supply.  This effect is of the order of a few mK.  At this 
moment we assume that we can cope with this problem.  During the first few 
stations the oxygen measurement with the CTD turned out to be faulty due to a 
loose contact.  This could be repaired and we assume that from station #4 onward 
we can supply reliable CTD- oxygen data. 

The positions of the CTD stations are given in the following table.  The 
definitive positions of the stations may differ slightly from the positions 
given here.  
AR7E
                                                                        

List of CTD stations

Stat. Samples #
C. #
Date
Time UTC
Latitude
Longitude
Depth m
N
1
1
12-Apr-91
10:01
55 44.4N
08 59.9W
  120
  4
44
1
22-Apr-91
22:22
59 40.0N
39.44.9W
2807
24

 
Water samples

The CTD was mounted with a Rosette sampler with 24 Niskin bottles and 3 
thermometer racks. The following analyses were carried out with samples taken:

In situ temperature was measured d with SIS electronic reversing thermometers 
with a display resolution of l mK. 

Salinity was determined by means of a Guideline Autosal salinometer. The 
standard water was from batches P112 and P114, supplied by the IAPSO Standard 
Water Service. 

The Oxygen concentration was determined by means of a high precision photometric 
end point determination, developed at NIOZ. For the stations on section AR7E 
samples from all bottles were analyzed as well as two blanks and one duplicate 
sample per cast. 

Nutrients were analyzed with a Technicon TRAACS 800 autoanalyser. The sample 
rate was set at 60 samples per hour. From all Niskin bottles Samples were taken 
for nutrient analysis so that over 2000 water samples were analyzed. For every 
sample Phosphate, Silicate, and Nitrite were determined. 

The total carbon dioxide content TCO2 was determined by means of a high 
precision coulometric instrument (Coulometrics Inc.). All samples from section 
AR7E were analyzed for TCO2 but at the sections of the control volumes only 
samples from the even bottles were analyzed.

Alkalinity was determined by means of titration. Because of the limited analysis 
capacity only the even bottles of 2 stations per day were analyzed as well as 
all surface samples. Comparison of the data from the two titrators indicated 
that after the cruise new volume calibrations of the titrators have to be 
carried out before final data may become available. 

XBT-observations Along the ship's track occasional XBT's have been launched in 
order to improve the horizontal resolution of the temperature structure in the 
upper ocean and to improve the extension of the information on the upper ocean 
temperature field.   
