Updated: Feb, 1992

WFP Ref. No.:		AR12
Project:		VIVALDI '91
Principal Scientists:	R. T. Pollard
			H. Leach
			G. Griffiths
Ship name:		RRS Charles Darwin 
Cruise No.: 		Cruises 58 & 59
Dates:			25 Apr-16 May; 18 May-10 Jun 1991. 


ABSTRACT

Vivaldi was conceived as a series of seasonal surveys of the NE Atlantic.  
The Vivaldi '91 trial combined the high spatial resolution of SeaSoar 
surveys with deep CTD stations spaced every 3 degrees of latitude on the 
tracks 300 km apart.  These primary measurements were complemented by a 
shipboard acoustic Doppler current profiler, chlorofluorocarbon tracer 
chemistry, Oxygen, nutrient and chlorophyll measurements, and mean surface 
meteorology.

The aims of Vivaldi are to:

* calculate seasonal upper ocean heat and fresh water budgets
* map isopycnic potential vorticity variations from the sub-tropical 
  gyre to the subpolar gyre
* map interannual changes in the properties of water masses formed by 
  deep convection
* calculate statistics of upper ocean parameters and air sea fluxes
* investigate the role of eddies


Scientific Personnel 

Cruise No.: 58

Pollard, Raymond T. 	JRC  (Principal Scientist)
Alderson, Steven G.	JRC
Anderson, Tom R.	JRC
Beney, Martin		RVS
Cunningham, Stuart A.	JRC
Griffiths, Gwyn		JRC, Project Manager
Griffiths, Mike J.	JRC
Grohmann, Dave		IOSDL
Gwilliam, T.J. Pat	IOSDL
Haine, Tom W.		Southampton Univ./PML
Holley, Sue E.		JRC
Keene, Steve B.		IOSDL
Lancaster, Peter F.	Southampton Univ.
Paylor, Rodger		JRC
Phipps, Richard A.	RVS
Rios, Aida		CSIC, Vigo, Spain
Smith, Paul K.		IOSDL
White, Cary R.		RVS

Cruise No.: 59

Leach, Harry 		Liverpool Univ. (Principal Scientist)
Bonner, Robin N.	JRC
Bowerman, Sarah J.	Liverpool Univ.
Cumming, Tony R.	RVS
Cunningham, Stuart A.	JRC
Donlon, Craig J.	Southampton Univ.
Griffiths, Gwyn		JRC, Project Manager
Griffiths, Mike J.	JRC
Hemimings, John C.P.	JRC
Holley, Sue E.		JRC
Lowry, Roy K.		BODC
Pearce, Rod		RVS
Phipps, Richard A.	RVS
Preston, Martin R.	Liverpool Univ.
Smith, Paul K.		IOSDL
Smithers, John		IOSDL
Stirling, Moragh W. 	IOSDL


NARRATIVE

	As a major contribution to the UK WOCE effort Vivaldi was conceived 
as a series of seasonal surveys covering the NE Atlantic.  In order to 
obtain both spatial coverage and high resolution a plan was developed in 
which nearly north-south SeaSoar sections, spaced 300 km apart relative to 
longitude 20 W as origin, would be complemented by deep CTD stations every 
3 degrees of latitude.

	Vivaldi'91, Charles Darwin Cruises 58 and 59 together, represents 
the first attempt to carry out a systematic survey as suggested by the 
Vivaldi concept.  It was decided to carry out the survey given the time and 
season available in two parts, first a southeastern part from Barry to 
Ponta Delgada (Cruise 58) and then a western and northern part (Cruise 59)
from Ponta Delgada back to Barry.  The position of the deep CTD stations 
was in theory defined by the formula enunciated above.  However because 
some of the theoretical positions were in untypically shallow water it was 
decided to move these into adjacent deeper water so that the deep water 
would also be samled. 

Cruise 58

	Sailing from Barry was delayed by over 12 hours because of an RVS 
management ban on weekend working.  RRS Charles Darwin passed through the 
lock at 0600Z/25 April (all times will be expressed in GMT) and set course 
for the first station position.  The ADCP was calibrated from 0230-0600/26 
April by a series of 90 course changes at 20 minute intervals with the ADCP 
in bottom track mode on the continental shelf. A trial CTD cast at 1030 
revealed a number of problems, most serious of which was that the lanyards 
supplied with the new 10 litre water bottles were the wrong length. A 
second trial cast was therefore undertaken at 1400.  The casts were 
numbered CTD 11v01 and 11v02.  The first '1' signifies the year 1991 and 
the second '1' signifies the first Vivaldi cruise in that year.  Thus the 
second leg (Cruise 59) will have numbers in the series CTD12...

	After each of the CTD stations, a zoological net was cast on the 
starboard side using a small kevlar winch and with the block held on the 
crane.  Minor problems were corrected after the first cast and the 
procedure was followed after every CTD cast throughout the cruise.  Later 
in the day (1836/26 April) the SeaSoar was deployed for a two-hour trial 
run, using the RVS-supplied block.

Vivaldi leg B

	The first full depth CTD (11v03) in the Vivaldi series was begun at
0252/27 April at position B48.  The numbering scheme signifies a cast on
line B at 48N. Five sections were to be occupied on Crusie 58.  The section
were nearly north-south runs, parallel in the sense of being 300 km apart,
with the third leg along 20W exactly north-south.  Each leg was identified
by a letter of the alphabet, with the first leg being leg B. CTD positions
were nominally at 3 intervals of latitude, at 39, 42, 45 and 48 N.  The
exact positions were adjusted usually by no more than a few miles to
maximise the water depth available and avoid known seamounts.  The first
cast was moved more than a few miles from its nominal position at 48 N
however, to 47.5 N, to reach deep water well south of the Celtic Shelf
edge. 

	After the CTD cast, the SeaSoar was deployed for the passage from
B48-B45 (SS11001).  The block was changed to the IOS supplied U-shaped
sheave so that (a) alength of chain could be removed, (b) the RVS block
could be built up on its cheeks to ensure that the wire could not jam down
the sides of the cheeks.  The SeaSoar run was historic, with the SeaSoar
profiling for the first time to 500 m. It ended at 0222/28 April when
course was altered downwind to recover SeaSoar.  With the IOS block
outboard, quite a few individual fairings snapped. 

	During deployment of the CTD (CTD 11v04, B45) the roller fitted to
the A-frame was not freed from its stowed position.  It sprang free
suddenly, which jarred the CTD and led to poor quality data on casts 11004
and 5.  After changing the stern block back to the RVS one, the SeaSoar was
deployed from 1829 for run B45-B42 (SS11002).  Good speeds were attained,
the SeaSoar preferring speeds of 8.5 - 9 knots to provide the lift needed
to raise the extra weight of cable.  This compensated for the time on
station, which was rather longer than had been allowed. 

	After CTD 11v05 (B42) it had been intended to continue south to 39N, 
but with time lost defore sailing, a slight underestimate of the mean
time between stations, and the need to allow at least a day for bad weather,
it was reluctantly decided that stations B39 and A39 would have to be
abandoned for this Vivaldi trial.  The SeaSoar was therefore deployed to
run west towards A42, but had to be recovered after little over an hour
because of electronics failure.  The problem was quickly shown to be
leakage in a blanking plug, but it was decided not to redeploy the SeaSoar,
but to steam on to the next station.  It was a blow to have to lose this
42 N section, which would have repeated a section occupied in the two
previous years.  However, in the context of Vivaldi it was the right
decision, as it enabled the CTD to be fully checked out during the passage
run.  It had given very noisy data on cast CTD 11v05.  Although no fault
was found, aboard must have been shaken loose when the frame was jarred, as
the noise disapeared after disassembly and reassembly. 

Vivaldi leg A

	Stations A42, A45 and A48 (CTD 11v06-8) were occupied between 30 
April and 2 May, with SeaSoar runs (SS11003-5) inbetween.  During this 
period problems in both CTD and SeaSoar systems were gradually traced and 
corrected, but the consequent strain, particularly on the senior 
electronics engineer,Pat Gwilliam, was high.

	During SS11003 (A42-A45) the SeaSoar was recovered because of a 
noisy signal, traced to a noisy fluorometer lead.  The ship steamed on 
during repair (1337-1448/30 April.  After deployment for run A45-A48 the 
SeaSoar would not respond to command and leaky hydraulics were stripped of 
at either the stem block or the roller at the lead onto the winch.  The 
former was caused by swinging of the stem sheave, which was reduced by 
welding a bar across it to give greater control.  The latter was caused by 
the metal stoppers on th cable catching on the edge of the roller when the 
cable lead was at angle.  This happened when the wire was full out as the 
winch was mounted somewhat to port of the centre line of the ship.  On 
recovery at A48 brooms were used to turn the fairing upwards as it led onto 
the blocks.  The A-frame was held inboard so that the stern block could be 
reached.  A great reduction in fairing damage was noted.  Once inboard, it 
was found that the bottom tail-plane was missing and the impeller blades 
bent.  The loss was most probably due to fatigue, and explained the rather 
poor maximum depths attained during the preceding run.


Vivaldi leg Z-20 W

	Leg Z was completed between 3 May and 6 May from 48 N to 39 N.  CTD 
casts were CTD 11v09 -11v12, and SeaSoar runs SS11006-8.  Weather was good 
throughout.  Because 20 W was the 'master' section, some extra time was 
allowed to run up to each CTD position before recovering SeaSoar and to 
position the ship prior to deployment so that the SeaSoar would be deployed 
and profiling by the time the CTD position was reached again.  This added 
about 30 minutes to manoevering time at each station.

	During leg A, careful examination of salinities, oxygens and 
nutrients from the 101 24 bottle multisampler had led to the definite 
conclusion that the bottles were not firing consistently at the depths at 
which they were triggered according to the deck unit.  Salinities provided 
the most accurate evidence, so from CTD 11v10 (Z45) onwards salinities were 
drawn from every bottle (previously samples had been drawn from alternate 
bottles for CTD calibration).  This proved that two bottles were firing at 
some depths and none at others.  After CTD11v11 the multisampler was 
stripped down, minor seawater damage repaired, and the firing pin position 
retarded.  Double firing was still apparent.  After CTD11v12, the 
multisampler was again stripped down and the firing pin advanced carefully 
to the midpoint between firing positions.  thereafter, near-perfect firing 
was achieved for the rest of the cruise.  The conclusion is that, on a 24 
bottle multisampler, with only 15 between firing positions, setup is 
critical, given that there is some play in the pin turning mechanism.

	At the end of SeaSoar run SS11007 (45-42 N) there was some swell 
and the nose of the SeaSoar slammed into the stern in the final moments 
during recovery.  The fibreglass nose was squashed and the bolts holding 
the weight sheared off, but no further damage was apparent.  Recovery at 
Z39 at the end of the next run was much easier running with the wind but 
kept a little on the quarter to reduce pitching.  Ideally, both deployment 
and recovery should be made running with the wind and the ship speed should 
be quite high, 4 quickly increasing to 7-8 knots on deployment and 6 knots 
dropping at a late stage to 4 knots on recovery.  For run SS11009 (Z39-Y39),
the course was westward running into wind.  Considerable pitching made 
deployment difficult when the faired cable went slack and threatened to 
foul the safety rails.  During run SS11009 trials with varying cable went 
slack and threatened to foul the safety rails.  During run SS11009 trials 
with varying cable lengths were done which confirmed previous calculations. 
A sea anchor was also tested for drag efficiency.

Vivaldi leg Y

	The fourth leg was occupied from 7 May to 11 May, with CTD casts 
11v13-16 at Y39, Y42, Y45 and Y48.  The SeaSoar runs inbetween were 
numbered SS11010-12.  With so little time lost to bad weather, it was 
possible to continue the manoevering described above to avoid any gaps in 
SeaSoar data just before and after each CTD cast.

	Before recovery at position Y42 a metal guide (ploughshare) was 
fitted to the travelling arm of the SeaSoar winch which laid the fairing 
correctly so that it could not foul the next turn.  In addition to being 
safer and reducing by one the number of people needed during recovery, the 
guide saves time, avoiding the two or three occasions on each recovery when 
wire has to be paid out to clear fouled turns.

	With so little bed weather, it was possible to make time for the 
main trawling warp, damaged on a previous cruise, to be ditched after 
CTD11v16 (Y48).  This took 5.5 hours (0533-1105/11 May), including the time 
needed to draw all samples from the multisampler, strip and stow the 
bottles and cover the multisampler to avoid damage or grease contamination 
during the wire cutting operation using the starboard A-frame.

Vivaldi leg X

	After the main warp had been ditched, the SeaSoar was deployed 
(1105-1131/11 May) to run west from Y48 to X48.  During this run, the wind 
increased to force 6 overnight.  By 1000/12 May it was decided that it 
would be impossible to hold station for the next CTD cast at X48, so there 
was no point in risking damage to the SeaSoar by recovering it in marginal 
conditions.  The wind was southwest, putting it on the port side during the 
westward run, but the starboard side after turning south.  The multisampler 
was therefore made more secure, the bottles removed and all gear stowed or 
lashed before the course change at 1122/12 May.

	The weather had eased considerably by the time SeaSoar was 
recovered at X45 (0947/13 May) for CTD11v17.  The SeaSoar runs from X48 to 
X39 (SS11014-16) were without incident apart from the poorer minimum depths 
attainable while the ship speed was reduced to 6-7 knots during the bad 
weather.  The final CTD casts CTD (11v17-19) went smoothly, except that the 
fluorometer fouled at the start of CTD11v19 during the first minutes of the 
cast.  The CTD was brought to the surface, during which time the fouling 
cleared, and the cast restarted.

	After all bottles had been sampled after the final cast, a zigzag 
ADCP calibration run was completed from 1740-2042/15 May, before course was 
set for Ponta Delgada.  RRS Charles Darwin berthed at 0915 on Thursday 16 
May at the end of a very satisfactory Vivaldi trial cruise.


Cruise 59

	The second leg of Vivaldi '91, Charles Darwin Cruise 59, began in 
Ponta Delgada, Azores, on Saturday 18 May 1991 when the ship set sail at 
1000.  We steamed directly to the first station, W39, where at 1110 on the 
19th, after the first CTD and net station (CTD 12v01), we began SeaSoaring 
northwards along section W.  Station W51 (CTD12v05) on 23 May seemed to be 
positioned directly on the Polar Front, which marks the boundary between 
the Subtropical and Subpolar Gyres.  A peregrine falcon and several 
housemartins were observed here.  At 2131 on 24 May we reached the northern 
end of Section W at Station W54 (CTD12v06).  From there we steamed east to 
Station X54 and then south to X48.  During the section east the SeaSoar 
conductivity cell 1 finally failed completely explaining the increasingly 
problematicl salinities of the last day or so.  At the recovery of the 
SeaSoar at Station Y48 on 29 May the towing cable was caught in the side of 
the block and needed reterminating.  From there we steamed north again.  At 
Station Y51 (30 May) the very first test of the IOSDL EG&G MKV CTD was made 
in a double station (CTD12v011 12) in 4002 m of water.  From Station Y54 
(31 May) we steamed east to Z54 (1 June) and then south along Section Z (20W).
Station Z51 many pilot whales and dolphins were observed close to the 
ship.  On the 4th at Station Z48 the bench in the wet laboratory flooded 
due to surplus water from the non-toxic supply not draining away and 
damaged the through-flow fluorometer so that it had to be replaced by an 
older model.  On leaving Station A48 (5 June) as the SeaSoar was being 
deployed in heavy seas the towing cable became jammed in the side of the 
block and need reterminating.  Then we were able to tow off northwards.  
On the 6th June at Station A51 (CTD12v20) bad weather developed while the 
CTD cast was in progress.  As a result the ship remained hove to until 0400 
7 June after which SeaSoaring was resumed and Section A continued 
northwards.  The last station (A54, CTD12v21) was finished by 0530 8 June, 
after which we set sail for Barry.

Final remarks

	For the first time the IOSDL SeaSoar CTD was equipped with two 
conductivity cells to help with the problem of correcting the salinity when 
the conductivity cell fouls.  Although this modification helped to some 
extent it did not solve the problem, which was particularly acute in 
frontal regions with high TS-variability.

	At all CTD stations hauls were made with plankton nets from 100 m 
depth and at most stations on Leg 2 from 300m-450m as well.

	During Leg 2 an air sampler mounted forward was used when the wind 
direction and speed were appropriate to collect aerosols.


