Principal Investigators and Contacts
Prof Andrew Brierley
School of Biology
Gatty Marine Laboratory
University of St Andrews
St Andrews, Fife, UK KY16 8LB
Telephone: +44 1334 463458 Fax: +44 1334 463443
E-mail: asb4@st-andrews.ac.uk
Web: http://www.st-andrews.ac.uk/~perg/andrews_page.htm
Prof Paul Fernandes
was at Fisheries Research Services, Marine Scotland
now at the University of Aberdeen.
Prof Mark Brandon
Note: this information provided by G Griffiths, National Oceanography Centre, Southampton in 2008, updated in 2020.
Dates
22 January 2001 to 14 February 2001
Aim of project
The project had two key objectives:
1. To investigate the physical and biological environment of the Antarctic Marginal Ice Zone
(MIZ).
2. To assess the potential of AUVs for improving acoustic estimates of biomass.
Through use of the Southampton Oceanography Centre (now the National Oceanography Centre) Autosub-2 AUV these objectives were coupled. In the polar context, acoustic estimates of biomass were targeted at Antarctic krill (E. superba), an animal at the core of the Southern Ocean ecosystem and food-web. It is widely acknowledged that krill abundance is related to sea-ice, but until this AUV experiment hypotheses on the relationship of krill to the ice edge could not be adequately tested. Within this project, the null hypothesis that the distribution of krill was the same in open water and under sea ice was tested. Critical to a fair experiment were:
(a) The use of the same acoustic instrumentation on board the vessel (RRS James Clark Ross)
and the AUV.
(b) The physical capacity of the AUV to carry and power the instruments.
(c) The assumption that the underwater radiated noise of the AUV and the ship was sufficiently low as not to disturb the krill swarms.
While this is a reasonable assumption for a ship in open water, this is not the case if the vessel was breaking ice if attempting to make krill stock estimates within the sea ice zone. Investigation of the physical environment of the marginal ice zone used the same echo sounder as for biomass estimates to obtain sea ice draft (and hence thickness), and the AUV’s CTD for water column measurements.
Funding Agency
UK Natural Environment Research Council
Details
Location: Northern Weddell Sea - map opposite showing the working area – black box – near 63˚S.
Operational Base: Research ship RRS James Clark Ross.
Ice type: Marginal ice zone with first year (ca. 0-7 – 1m thickness) and multiyear floes (>2m), from open water to 9/10ths cover. Icebergs present, in the pack and in open water. Examples shown in the photographs opposite at the southernmost position for the AUV missions.
Water depth: Over 1000 m.
Deployment/Recovery methods: Dedicated launch and recovery gantry on stern of the ship. Vehicle brought alongside on the starboard side by manoeuvring the ship; recovery float ‘popped’ by command, and lines deployed from the vehicle; grappled from the ship, and the vehicle ‘walked’ aft, round the starboard quarter and to the stern. Critical period is when lines/vehicle near the stern. The gantry was open to the elements, not good, especially when changing batteries and servicing the vehicle. Key lesson learnt – need for heated container housing vehicle and its gantry.
Servicing the Autosub on the aft deck of RRS James Clark Ross under poor conditions. The launch and recovery gantry picks up the vehicle, moves it forward along the rail, when outboard, the vehicle carrier rotates, to bring the vehicle parallel to the stern, and it is then winched down to the sea surface and released.
Vehicle Specifications
AUV class/type: Autosub class 6.8m long, 0.9m in diameter ~3000kg displacement. Endurance over
400km at 1.7 m/s. Diving depth to 1600m. Primary manganese alkaline battery ca. 60kWh.
Navigation/positioning systems: GPS/DR, using Navstar IDAR GPS receiver and Seatex MRU6 fluxgate heading/attitude sensor with downward looking RD Instruments 300 kHz ADCP in water-track mode.
Obstacle avoidance: Not implemented for this cruise; questions remained over the robustness of false target handling. Lack of an obstacle avoidance system resulted in a glancing collision with an iceberg, which the vehicle survived and continued on its mission.Bent acoustic transducer cage after glancing impact with iceberg at a depth of 150m, damage to the gel coat of the front GFRP panel, but the screen over the CTD sensors meant they were not damaged.
Emergency measures: Abort on over depth, on leak in any of the main pressure vessels, on mission over allocated time, on range of faults such as power loss, loss of internal network data communications. Abort drops a weight and vehicle rises to the surface.
Parameters logged: The full inventory of data and parameters logged is available on the British Oceanographic Data Centre (BODC) archive for this project. Also, the full cruise report pdf file can be downloaded from this BODC page.
Other equipment: 120 kHz and 38 kHz Kongsberg Simrad EK500 echo-sounder (transducers could be arranged to look up or to look down); two Sea-bird 911 CTDs, one each side of the vehicle nose; Photosynthetically Active Radiation (PAR) sensor; fluorometer for estimates of chlorophyll A; transmissometer; oxygen probe; 2 RD Instruments 300 kHz ADCPs (one upward looking and one downward looking).
Debrief/dissemination: Publications/web sites arising from project:
Brierley, A.S., Fernandes, P.G., Brandon, M.A., Armstrong, F., Millard, N.W., McPhail, S.D.,
Stevenson, P., Pebody, M., Perrett, J.R., Squires, M., Bone, D.G. and Griffiths, G., 2003. An
investigation of avoidance by Antarctic krill of RRS James Clark Ross using the Autosub-2
autonomous underwater vehicle. Fisheries Research, 60: 569-576.
Brierley, A.S., Fernandes, P.G., Brandon, M.A., Armstrong, F., Millard, N.W., McPhail, S.D.,
Stevenson, P., Pebody, M., Perrett, J.R., Squires, M., Bone, D.G. and Griffiths, G., 2002.
Antarctic krill under sea ice: elevated abundance in a narrow band just south of ice edge.
Science, 295: 1890-1892.
Brandon, M. A. and Banks, C. J., 2006, Investigations of Icebergs in the North-West Weddell
Sea Using the Autonomous Underwater Vehicle AUTOSUB II. Eos Trans. AGU, 87(52), Fall
Meet. Suppl., Abstract C41B-0323
Details of the missions
M244
Start time / position 26-Jan-2001 14:22:00 62.8300S 51.4333W
End time / position 26-Jan-2001 15:15:00 62.8267S 51.4200W
Notes: Compass Calibration Mission. Mission aborted due to extended dive to 405m. EK500 stopped logging shortly after dive. Autosub systems suffer power reset after recovery due to faulty cable on main ON/OFF switch. 1.5 km
M245
Start time / position 26-Jan-2001 23:45:56 62.8144S 51.4362W
End time / position 27-Jan-2001 02:06:26 62.8134S 51.4335W
Notes: Compass calibration mission. Box NE/SW 5 minutes each at 12 m depth. Surface, then correct for quadrant compass errors, then run north for 1 mile at 150 m depth. Surface, get fix then do reciprocal run south for 1 mile. Two GPS navigated reciprocal runs needed for compass alignment/ declination adjustment, as no bottom track navigation available in deep water. 5 km
M246
Start time / position 27-Jan-2001 14:29:18 62.7475S 51.5387W
End time / position 27-Jan-2001 15:05:40 62.7597S 51.5112W
Notes: Straight run at 150 m for about 1 mile in SE direction as a test of systems. Successfully completed. 2 km
M247
Start time / position 27-Jan-2001 15:32:02 62.7590S 51.5128W
End time / position 28-Jan-2001 03:44:30 62.6859S 51.4604W
Notes: First under ice mission. 20 km in, 8 km left, 28 km out. Starting about 5 km from the ice edge. Ship Carrying out reciprocal track. Mission successful. Mission stopped by acoustic command to save time. 50 km
M248
Start time / position 28-Jan-2001 13:41:06 62.8118S 50.1660W
End time / position 29-Jan-2001 02:16:54 62.8810S 50.2317W
Notes: 20 km in, 8 km left, 25 km out. Starting about 5 km from the ice edge. Ship Carrying out reciprocal track. Slow to dive into waves, otherwise no problems. 50 km
M249
Start time / position 29-Jan-2001 14:50:13 62.9322S 49.2855W
End time / position 30-Jan-2001 02:32:00 62.9152S 49.5233W
Notes: 20 km in, 8 km right, 25 km out. Starting about 3 km from the ice edge. Ship carrying out reciprocal track. Little Behemoth (EK500) data, Libretto PC suspected. One mast ripped off by collision with ship on launch. Boat put into water to try and fix; second (Ethernet) mast ripped off by boat. Vehicle brought back onboard for repair. On recovery both antenna masts ripped off by recovery line. 50 km
M250
Start time / position 31-Jan-2001 13:14:21 62.4505S 49.4886W
End time / position 31-Jan-2001 15:25:41 62.0995S 49.5555W
Notes: Attempt to go beneath small icebergs. Run at 240 m deep. Try to go beneath berg in S/N and E/W directions, berg about 60 m diameter. S/N transect successful. E/W missed main berg but glanced underneath second smaller berg. Berg draft measured by EK500 as 134 m. Sub recovered because of concerns about weather worsening. 5 km
M251
Start time / position 31-Jan-2001 20:46:36 62.9281S 49.4415W
End time / position 31-Jan-2001 22:32:42 62.9533S 49.5633W
Notes: Attempt to get under three icebergs in a row, at 240 m depth. Missed all three! Navigation seemed a long way out (too much for known currents) suggesting the need for compass recalibration. 10 km
M252
Start time / position 01-Feb-2001 10:00:49 62.9585S 48.3458W
End time / position 01-Feb-2001 23:27:00 62.8741S 48.2451W
Notes: Box compass calibration. Vehicle surfaced, calibration applied then vehicle sent on transect under sea-ice, 23 km in, 8 km across, 28 km out. Compass calibration suggested significant change from the previous calibration. Suggests that compass calibration should be carried out after each change of batteries or anything moved near the compass. Due to a mistake, the heading offset was set to 0.0 instead 0.085 radians. The ADCP and echo sounder data show that the Autosub hit an iceberg at 150 m depth a few minutes before recovery. Damage to front starboard panel, starboard CTD and bent acoustic transducer guard. Starboard CTD pump damaged - data may be suspect, otherwise little damage. 60 km
M253
Start time / position 02-Feb-2001 10:04:05 -63.0728S 47.3689W
End time / position 02-Feb-2001 23:42:00 -63.0758S 47.5586W
Notes: Under ice mission. In (south) 25 km, turn right (west) 8km, then out 30 km. Mission successful. One recovery line was dropped during recovery, resulting in a difficult recovery. Resultant damage was a lost front panel, broken aerials and broken propeller blades. 63 km
M254
Start time / position 03-Feb-2001 15:25:21 63.0451S 46.8699W
End time / position 03-Feb-2001 16:38:06 63.0452S 46.8680W
Notes: For testing of the CTD sensors by Dr. Stansfield. Profile mission from 100 m up to 7 m, five profiles heading 90˚ Temperature gradients of about 1˚.
M255
Start time / position 03-Feb-2001 17:48:33 63.0522S 46.8830W
End time / position 03-Feb-2001 20:05:00 63.0528S 46.9358W
Notes: Attempt to go under an iceberg with lawnmower pattern, at 180 m depth. Successful, but only small amount of data under iceberg. Drift rate of iceberg exceeded progression rate of lawnmower pattern. Consequently, very little time spent under the iceberg, only intersecting at near end of mission. Autosub surfaced dangerously close to the iceberg. 10 km
M256
Start time / position 03-Feb-2001 20:20:00 63.0528S 46.9358W
End time / position 03-Feb-2001 20:30:00 63.0567S 46.9317W
Notes: Short Mission to run Autosub on the surface to a safer place for recovery (Autosub had
surfaced dangerously close to an iceberg). 0.7 km
M257
Start time / position 05-Feb-2001 12:34:52 62.8882S 51.1845W
End time / position 05-Feb-2001 14:58:37 62.8939S 51.1900W
Notes: Under large (~1.8 km diameter) iceberg mission to collect EK500 (up) and ADCP up tracking data. ADCP data fine, but EK500 failed to collect data. 9 km
M258
Start time / position 05-Feb-2001 16:36:00 62.9093S 51.1788W
End time / position 05-Feb-2001 17:17:00 62.8920S 51.2005W
Notes: Short transit mission at 10 m depth to get into better position for next iceberg mission. As noted previously, no data from EK500. 3 km
M259
Start time / position 05-Feb-2001 17:48:28 62.9093S 51.1813W
End time / position 05-Feb-2001 20:41:00 62.9063S 51.1962W
Notes: Under iceberg mission at a depth of 250 and 330 m with intention of checking out the ADCP tracking performance. Initial heading 147ÛLQNPULJKWNPRXWNPWKHQ repeated pattern at 330 m depth. Successful completion of the mission. No EK500 data again, ADCP data was good. Tracking off lower surface of iceberg at a 170 m range. 15 km
M260
Start time / position 06-Feb-2001 17:04:58 62.9880S 51.4523W
End time / position 06-Feb-2001 22:47:56 63.0206S 51.4724W
Notes: Compass calibration mission run at 50 m, to calibrate the compass following the battery change, followed by short 13km in, 1km (to west), 16 km out, at initial heading of 180ÛDOVRDW 50 m depth. Mission also to test EK500 following lack of data on previous mission. Mission successful. EK500 worked OK. Seems that remedies worked (insulating aerial and cleaning up connector to reduce chance of earth leakage). The port side CTD sensors were found to have the connecting pipe between sensors missing. We do not know whether pipe was missing during mission. 32 km
M261
Start time / position 07-Feb-2001 20:04:11 63.0653S 51.4580W
End time / position 07-Feb-2001 20:10:42 63.0657S 51.4588W
Notes: Under ice at night. Autosub failed to dive, presumably due to unfavourable swell. Mission Aborted. 0.1 km
M262
Start time / position 07-Feb-2001 20:52:59 63.0653S 51.4580W
End time / position 08-Feb-2001 13:20:00 62.9753S 51.5573W
Notes: Under ice mission through the night. In 32.5 km, at 180ÛWXUQWRÛIRUNPWKHQQRUWK and out of the ice for 42.5 km. Mission Successful. Longest Autosub mission under ice so far. Mission was modified to dive on constant heading due to previous failed attempt. Dived without a problem. PAR sensor connector fault noticed, also bulkhead connector pin badly corroded. PAR sensor refitted with replacement connector. PAR data prior to this may be suspect. 80 km
M263
Start time / position 09-Feb-2001 19:46:16 61.8114S 57.0132W
End time / position 09-Feb-2001 22:53:39 61.9467S 56.9667W
Notes: Ship-following mission for krill avoidance studies. Run south for 13 km, at depth of 10m.
Fog and occasional growlers made operation tricky, otherwise successful. 13 km
Lessons learned:
• Adequate heated lab/servicing container is needed to house the vehicle and the launch
and recovery gantry is needed for shipboard polar environments.
• Better endurance can be obtained by insulating the battery housings, this also makes use
of the waste heat generated by the batteries on discharge.
• An effective collision avoidance system is needed; one that handles false targets and
software that provides appropriate responses to collision threats.
• Launch and recovery hazards can be minimised by well-rehearsed procedures involving
the vessel officers and crew, with good communications between the deck and the bridge
essential. When a recovery operation looks as if it will not go well, best to break off and
try again.
Map of the Weddell Sea area with a satellite image of the ice distribution at the time of the expedition. The working area was within the black box. Autosub2 carried out under-ice missions whilst the RRS James Clark Ross made reciprocal transects into open water.
Brash ice typical of the dispersed marginal ice zone at the northern ends of the AUV missions.
Close-packed first year ice along a track that Autosub traversed, with scattered icebergs.
Working conditions on the open deck for the Autosub team were far from ideal. A canvas awning was erected to protect the team and the vehicle when changing batteries. A major lesson learnt was that there was a need for a proper shelter for future polar missions. This took the form of two 20' shipping containers as a T shape; the 'vertical' housing the AUV and the cross being the support workshop.
Here, the purpose-built launch and recovery gantry picks up the vehicle on two lines, moves it outboard, swivels parallel to the stern, then lowers the vehicle into the water using two winches.
Damage to the gel coat of the GFRP nose panels after a collision with the underside of the iceberg below at a depth of 150m. The metal screen protected the CTD sensors although it did get bent.
Lowering the EK500 pressure vessel into Autosub. The large size of Autosub, and its power and energy capacity meant it could carry large, heavy and power-hungry instruments such as this multi-frequency fisheries sonar.
Autosub with the EK500 38kHz transducer nearest the nose (black with orange rim, and in the close-up on deck below) with the 120kHz transducer immediately behind.
A custom-built low data rate two-way acoustic link had been built by Applied Acoustic Engineering. This provided telemetry of the Autosub's own estimated position, depth, heading and battery status that could be integrated with GPS data on the ship to give a map of the vehicle's position and manoeuvres over a range of a few km.
Another lesson learnt, and published, was that the waste heat from the internal resistance of the batteries could be used to keep them well above ambient temperature during a mission. Here is shown a section of foam insulation around one of the later battery modules.