Mareano leg 3 2023

The following Abbreviations are use throughout this report:

AUV : Autonomous Underwater Vehicle – here it is the Kongsberg Munin +.

CT : Conductivity and Temperature (but not Depth as is normal) – the AUV CT sensor does not collect pressure information that is converted into depth as standard, but it does have an altimeter/depth sensor as part of that navigation system so this data is also available.

CTD : Conductivity, Temperature and Depth sampling rosette

FFI: Forsvarets forskningsinstitutt (Norwegian Defence Research Establishment)

FOH: Forsvarets operative hovedkvarter (Norwegian Joint Headquarters)

HF: Hardanger fjord

HI : Havforskningsinstituttet or the Institute of Marine Research as it is called in English.

MBE : MultiBeam Echosounder

NGU : Norsk Geologiske Undersøkelse or the Norwegian Geological Survey as it is called in English.

SVO : Særlig Verdiful Område – translates to “Especially Valuable Area” and is a Norwegian management region that currently has no protection measures but indicates an area of particular ecological value.

• Recover the Chimera video rig that was lost during Mareano leg 2 (approximately 7 nm east of Tromøya.

  • Achieved

• Assist FFI in recovering a shell frame from a dumping ground for munitions (post WWII) in the Norwegian Trench.

  • Achieved

• Sample (physically and using video) Isidella corals along the slope south of Egersund for studies and gene sequencing.

  • Achieved

• Perform full station physical sampling simultaneously with AUV dive.

  • Achieved

• Gain experience with the placement and use of different equipment for cruises equipped with AUV, ROV and physical sampling gear.

  • Achieved

• Perform various tests related to improving data quality with the AUV Munin+ and evaluate the position accuracy and navigational skills.

  • Partly achieved

• Video sample areas in Skagerrak that cannot be mapped with conventional Mareano sampling due to challenging terrains and current conditions (which requires ROV).

  • Partly achieved

• Obtain shallow core samples of bottom sedients both inside and outside of intensively trawled areas for studies of carbon storage in sediments.

  • Partly achieved

• Complete three previously planned video stations that have not been sufficiently surveyed.

  • Deferred due to weather

• Map trawl tracks and investigate the consequences of intensive trawling for seabed conditions, including carbon storage capacity in sediments.

  • Deferred due to weather

The cruise was focused on areas with steep or challenging terrain in Skagerrak, where video sampling using a camera rig is not possible. A planning meeting at NGUs offices in Trondheim where we had access to restricted high-resolution bathymetry was carried out before the cruise in order to plan all targeted stations based on 1) terrain and 2) seabed substrate. This resulted in a total of 31 planned stations of priority as well as 18 backup stations of lower priority. We also planned four areas for AUV mapping, and two back-up areas in secluded areas close to land in case of challenging weather conditions. We had applied (and received permission) from FOH for declassification of seabed data in these areas before the cruise. In addition to the main interest area in Skagerrak, we had planned ROV dives south-west of Karmøy on the recently discovered wreck of a WWII U-boat and in the Isidella hot-spot outside Lindesnes. Due to extreme weather conditions we had to plan a new set of video lines inside the Hardanger fjord. We did not have a suitable declassified area inside the fjord, so AUV missions were not possible to conduct and were therefore not planned. The video stations in the fjord are marked on the inset map (HF).

Priority

• Recover the video rig Chimera (1)

• Finish the two last (grts) video-stations in Skagerrak

• ROV video stations (and physical sampling) in Skagerrak

• Survey trawl marks (AUV + ROV-dives)

• Carbon storage sediment sampling

• Map modelled coral reef with AUV

• Sample Isidella south of Egersund

• Aid FFI in recovery of mussel rig

• Sample a full station simultaneously with AUV-dive

Lower Priority

• Video stations in the southern part of the Norwegian North Sea i SN

• Sample additional full stations in Skagerrak

Information regarding the data collected is shown in the following figures, as well as the overview map (figure 1). More details for each station are available in the day by day overview appendix, on the mareano webpage, or can be given upon request.

We had some major difficulties with weather conditions on the cruise. Waves of op to 12 meters in the North Sea made us withdraw into the fjords for the better part of the cruise. As we had some prioritized operations that demanded fair weather conditions we had to use the small weather windows to complete these at the expense of other activities. We sent an inquiry to end the cruise early due to the demanding conditions, but due to a major surge if ships going in to Bergen Havn and weekend approaching it was not possible to de-mobilise until the pre-planned date we decided to make the best of it and spent the last days surveying the Hardanger fjord.

7.1 - ROV

The Ægir6000 was surprisingly susceptible to wave action and, not least, current conditions. We experienced that a current strength of as little as 2 knots made diving with the ROV challenging. Based on this, we would recommend bringing the TMS if Ægir is to be used on expeditions during the winter season

7.2 - AUV

As somewhat feared in advance, the weather windows for AUV collection were few and short, and as a result, we were not able to use the vessel nearly as much as we wanted. This resulted in two successful dives in the Skagerrak that collected data of apparently good quality. Launch and recovery went well despite challenging weather conditions, which we view as positive.

7.3 - Deck space during the cruise

In one of the Skagerrak's AUV areas, a full station was conducted in parallel with the AUV dive. The deck space for processing samples was effectively resolved in consultation with the trawl boss and bridge. Cleaning and sorting stations on the port side of the trawl deck were well suited for MAREANO's samples. A small “breakwater” (molo) was placed in front of the grate on the stern of the vessel, which worked OK under the prevailing weather conditions, but in rougher seas, the grate should be able to be closed off with a solid plate or the breakwater significantly heightened to secure valuable samples during processing. We envision conducting physical sampling in AUV areas simultaneously where the AUV is operational on upcoming voyages.

This cruise aimed at carrying out tests on the AUV function and particularly how the different acoustic instruments potentially interfered with each other and how much the AUV drifted throughout the dive by covering the same points at the beginning and end of the dive and with different instrument switched on.

Two divers were carried out and went relatively well and collected good data that will enable the intended tests. However, the weather did not allow further dives after the day 2 of the cruise so only 2 dives took place instead of the 6 intended.

8.1 - Dive 1:

This first dive took place at the a relatively flat 400m deep area in the southwesternmost declassified zone. It aimed at collecting acoustic data over an area where the presence of pockmarks and the general topographic setting led to the suspicion that it contained a lot of mud which could store vast amount of carbon.

The AUV used the EM2040 Multibeam while flying at 70m in a grid pattern to provide full bathymetric coverage of the area at <1m resolution.

The Hisas sounder was also used in a grid pattern flying at 20m from the seabed to provide full coverage of the same area at high resolution

Finally a last line was carried out where the vehicle went back over the terrain it had previously surveyed and, particularly, at a noticeable feature that stood out and would be easily identifiable in the resulting surface thus acting as an ‘anchor’. This repetition will enable a precise measurement of the drift in AUV positioning throughout the mission by calculating the distance between the locations of the anchor feature in both MB lines that went over it. At the last point before the AUV started its ascend, the distance between the internal navigation and the navlab processed navigation was 4.85m. This less than 5m drift over 6 hours is considered low.

8.1.1 - Dive Plan 1

# Kongsberg Maritime AUV Mission Plan

# Saved 2023-10-09 14:01:19 by hugin

#:Tag Depth Alt DMo Latitude Longitude Course GMo Speed SMo Dur Dist Flags

# Speed up

:speed 0.0 30.0 D - - 234.0 H 2.30 S 30 - EMPowerOn

: = = = - - = = = = 30 -

# NB: Remember to set Safe 20m and Crit 10m distance in Startup parameters!

: = = = - - = = = = 30 -

# Are we waiting enough for payload to boot?

: = = = - - = = = = 1 - EMPowerOn

: = = = - - = = = = 1 - SASPowerOn

: = = = - - = = = = 1 - ETPowerOn

: = = = - - = = = = 1 -

: = = = - - = = = = 1 -

: = = = - - = = = = 1 -

: = = = - - = = = = 1 -

: = = = - - = = = = 1 -

: = = = - - = = = = 10 -

: 0.0 = = - - = = = = 1 -

# Start dykk til 50m for aa sjekke at alt er ok, Jump here to repeat dive

:dive 50.0 = = - - = = = = 180 -

: = = = - - = = = = 1 -

: 50.0 = = - - = = = = 180 -

# Jump from here to repeat dive, health check here

:health = = = - - = = 2.00 S 20 -

: = = = - - = = = = 1 -

# Submerged, vehicle configuration

:config = = = - - = = = = 1 - RollCtrlOn

: = = = - - = = = = 1 - EM400Int

: = = = - - = = = = 1 - Auto

: = = = - - = = = = 1 -

: = = = - - = = = = 1 -

: = = = - - = = = = 1 -

# Descent to working depth (100 m / 3 min), Activate HiSAS

:descent 300.0 70.0 D - - = = = = 720 - EMOn

: 400.0 70.0 T - - = = = = 180 -

# Lead-in to Survey Pattern

:leadin = = = 58:27.9368N 009:21.4817E (234) = = = - - Auto

:leadin = = = 58:27.8909N 009:21.4018E (222) = = = (57) (115)

: = = = 58:27.8475N 009:21.3591E (207) = = = (45) (91)

:mbline01 = = = 58:26.8607N 009:19.6104E (223) = = = (1250) (2500)

:mbturn = = = 58:26.7903N 009:19.7559E (133) = = = (96) (193)

:mbline02 = = = 58:27.7771N 009:21.5047E (043) = = = (1250) (2500)

:mbturn = = = 58:27.7067N 009:21.6505E (133) = = = (96) (193)

:mbline03 = = = 58:26.7199N 009:19.9013E (223) = = = (1250) (2501)

:mbturn = = = 58:26.6494N 009:20.0468E (133) = = = (96) (193)

:mbline04 = = = 58:27.6362N 009:21.7961E (043) = = = (1250) (2501)

:mbturn = = = 58:27.5658N 009:21.9418E (133) = = = (96) (193)

:mbline05 = = = 58:26.5790N 009:20.1922E (223) = = = (1250) (2501)

:mbturn = = = 58:26.5085N 009:20.3377E (133) = = = (96) (193)

:mbline06 = = = 58:27.4954N 009:22.0874E (043) = = = (1250) (2501)

:mbturn = = = 58:27.4249N 009:22.2331E (133) = = = (96) (193)

:mbline07 = = = 58:26.4381N 009:20.4831E (223) = = = (1250) (2501)

:mbturn = = = 58:26.3677N 009:20.6285E (133) = = = (96) (193) SASMode1

:mbline08 = = = 58:27.3545N 009:22.3787E (043) = = = (1250) (2501) SASHighPower

:em_stop = = = 58:27.4676N 009:22.4003E (006) = = = (105) (211) EMOff

# HISAS - set depth and altitude

:hisas_st 400.0 = = 58:27.5095N 009:22.3245E (317) = = = (53) (107) SASOn

: = = = 58:27.5476N 009:22.2459E (313) = = = (52) (104) CritHeight6

: = = = 58:27.5817N 009:22.1826E (316) = = = (44) (88) SafeDist10

: = 20.0 = 58:27.8194N 009:21.6825E (312) = = = (328) (657)

# Lead-in to Survey Pattern

:leadin = = = 58:27.7928N 009:21.4667E (257) = = = (107) (216) ETOn

:l01 = = = 58:26.8000N 009:19.7455E (222) = = = (1245) (2490)

: = = = 58:26.7692N 009:19.8103E (132) = = = (42) (85)

:l02 = = = 58:27.7620N 009:21.5316E (042) = = = (1245) (2490)

: = = = 58:27.6787N 009:21.7072E (132) = = = (115) (230)

:l03 = = = 58:26.6858N 009:19.9858E (222) = = = (1245) (2491)

: = = = 58:26.6551N 009:20.0506E (132) = = = (42) (85)

:l04 = = = 58:27.6479N 009:21.7721E (042) = = = (1245) (2491)

: = = = 58:27.5647N 009:21.9476E (132) = = = (115) (230)

:l05 = = = 58:26.5718N 009:20.2261E (222) = = = (1245) (2491)

: = = = 58:26.5410N 009:20.2909E (132) = = = (42) (85)

:l06 = = = 58:27.5339N 009:22.0125E (042) = = = (1245) (2491)

: = = = 58:27.4506N 009:22.1880E (132) = = = (115) (230)

:l07 = = = 58:26.4577N 009:20.4664E (222) = = = (1245) (2491)

: = = = 58:26.4269N 009:20.5312E (132) = = = (42) (85)

:l08 = = = 58:27.4198N 009:22.2529E (042) = = = (1245) (2491)

# MB check

: = = = - - = = = = 1 - SASOff

: 400.0 70.0 = 58:27.6712N 009:21.9254E (042) = = = 1 - EMOn

:em_leadi 400.0 70.0 = 58:27.7069N 009:21.6522E (284) = = = (136) (274)

:mb_check = = = 58:26.6496N 009:19.7760E (223) = = = (1340) (2681)

: = = = 58:26.0763N 009:18.7772E (222) = = = (720) (1442) Ascent

8.2 - Dive 2

The second dive took place over a relatively flat 200m deep zone in the easternmost declassified area.

The aim wsa to cover as much surface as possible during a short window of weather suitable for recovery of the AUV. The whole dive could not be carried out and had to be aborted after 4h 50m to ensure safe recovery on board. Hisas data was collected in a grid pattern flying at 20m altitude to offer a high resolution view of the seabed so small objects could be visually detected Initial inspection of the hisas data also revealed large number of trawlmarks. Sub-bottom profiler was also switched on during the dive for an assessment of the sensor by geologists.

8.2.1 - Mission plan Dive 2

# Kongsberg Maritime AUV Mission Plan

# Saved 2023-10-10 06:21:14 by hugin

#:Tag Depth Alt DMo Latitude Longitude Course GMo Speed SMo Dur Dist Flags

# Speed up

:speed 0.0 20.0 D - - 180.0 H 2.30 S 30 - EMPowerOn

: = = = - - = = = = 60 - SASPowerOn

# NB: Remember to set Safe 20m and Crit 10m distance in Startup parameters!

: = = = - - = = = = 1 - ETPowerOn

# Are we waiting enough for payload to boot?

: = = = - - = = = = 1 - SafeDist10

: = = = - - = = = = 1 - CritHeight6

: = = = - - = = = = 1 -

: = = = - - = = = = 1 -

: = = = - - = = = = 1 -

: = = = - - = = = = 1 -

: = = = - - = = = = 1 -

: = = = - - = = = = 1 -

: = = = - - = = = = 1 -

: 0.0 = = - - = = = = 1 -

# Start dykk til 30m for aa sjekke at alt er ok

:dive 100.0 = = - - = = = = 180 -

: 100.0 = = - - = = = = 180 -

# Jump from here to repeat dive, health check here

:health = = = - - = = 2.00 S 20 -

: = = = - - = = = = 1 - Auto

# Submerged, vehicle configuration

:config = = = - - = = = = 1 - RollCtrlOn

: = = = - - = = = = 1 -

: = = = - - = = = = 1 -

: = = = - - = = = = 1 - SASHighPower

: = = = - - = = = = 1 - SASMode1

: = = = - - = = = = 1 - ETOn

# Descent to working depth (100 m / 3 min), Activate HiSAS

:descent 195.0 = T - - 180.0 = = = 360 - SASOn

: = = = - - = = = = 1 -

: = = = - - = = = = 1 -

:setalt = 20.0 = - - = = = = - -

# Lead-in to Survey Pattern

:leadin = = = 58:51.7434N 010:10.4904E (180) = = = - -

:ns_01 = = = 58:48.0441N 010:11.8531E (169) = = = (3495) (6992)

: = = = 58:48.0356N 010:11.7662E (259) = = = (42) (85)

:sn_02 = = = 58:51.7344N 010:10.4041E (349) = = = (3495) (6991)

: = = = 58:51.7111N 010:10.1688E (259) = = = (115) (230)

:ns_03 = = = 58:48.0122N 010:11.5316E (169) = = = (3495) (6991)

: = = = 58:48.0039N 010:11.4437E (260) = = = (43) (86)

:sn_04 = = = 58:51.7012N 010:10.0822E (349) = = = (3494) (6988)

: = = = 58:51.7660N 010:10.7268E (079) = = = (315) (632)

:ns_05 = = = 58:48.0673N 010:12.0882E (169) = = = (3495) (6991)

: = = = 58:48.0758N 010:12.1750E (079) = = = (42) (85)

:sn_06 = = = 58:51.7747N 010:10.8139E (349) = = = (3495) (6991)

:endhisas = = = 58:51.8795N 010:10.7705E (348) = = = (99) (199)

# position check

: = = = 58:51.8200N 010:10.6035E (235) = = = (97) (195)

: = = = 58:51.7808N 010:10.2052E (259) = = = (194) (390)

: = = = 58:51.7013N 010:10.0824E (219) = = = (94) (189)

# position check?

:pos_chk = = = 58:50.5320N 010:10.5133E (169) = = = (1105) (2210)

: = = = - - = = = = - 50 Ascent