CRUISE REPORT R/V Farnella FA87-3 March 28 - April 25, 1987 Dennis W. O'Leary U.S. Geological Survey Woods Hole, Mass. 02543 Cruise number: FA 87-3 Vessel: R/V Farnella (fig. 1) Captain: Michael Patterson Parent project: Atlantic EEZ GLORIA survey Funding agency: U.S. Geological Survey Funding amount: $750,000 Cruise start/end dates: March 28-April 25, 1987 Area of operations: (fig. 2) 1. The U.S. EEZ, from 72d10'W, 39d25'N, east along the 400-m contour of The New England Continental Slope to 66d05'W, 41d00'N, southeast an west along the outer border of the EEZ, and then along a line 316d from 69d47'W, 37d49'W. 2. The Continental Rise off Nova Scotia within an area bounded by the eastern margin of the U.S. EEZ, east to approximately 42d15'N, 62d40'W, southeast to 61d15'W, 40d30'N, southwest to 62d00'W, 40d00'N, and west along 40dN to about 64d50'W, and northwest along 316d to the U.S. EEZ. Purpose of Cruise: To obtain complete GLORIA long-range sidescan sonar image coverage within the area of operations as well as ancillary seismic reflection profile data and magnetometer profile data. Pursuant to Project Implementation Plan no. 7, Annex 8, between USGS and National Environment Research Council (NERC) of the U.K. Scientific party: (fig. 3) Dennis O'Leary-USGS: chief scientist John Hughes Clarke-CGS: co-chief scientist Eric Schmuck-USGS: cruise data curator James Vaughan-USGS: MASSCOMP tech Gerard Costello: Canadian Hydrographic Service Roy Sparkes-CGS Max Dobson - IOS Eric Darlington-IOS Linton Wedlock - IOS Ross Walker-IOS Mick Gooden - IOS Steve Williams-IOS David Gunn - IOS Navigation technique: Loran C in the hyperbolic mode was used throughout the survey area for positioning. Four receivers were operational: 2 Megapulse Accufix 500's, a Northstar 7000, and a Racal-Decca MNS2000. Time Differences (TD's) and Lat/Long from the Northstar and MNS2000 were logged on the IOS ABC system for the entire cruise. The 2 Megapulse receivers were interfaced to separate IBM PC's where the observed TD's were converted to Lat/Long. All data were logged on a floppy disc and printed out every 5 minutes. As of April 8 (JDO98) data from one of the Megapulse/IBM's were logged on the ABC system; however, near the end of the cruise it was discovered that a bug in the program (making the tenth of a microsecond (us) digit = 0) rendered the TD's useless. A single "mean" ASF correction for each Master/Secondary pair was determined from the available sources --- DMA and CHS/BIO --- and applied to the observed TD's on the Megapulse/IBM system for the entire survey, as shown below. CHAIN SECONDARY ASF 9960 W Caribou +1.0 us X Nantucket +2.8 us Y C. Beach +2.4 us 5930 X Nantucket +2.1 us Y Cape Race +1.4 us The Northstar receiver had ASF corrections built in at time of manufacture. There was a Lat/Long bias available but was not used. Apparently the Northstar receiver has errors in the TD to Lat/Long conversion and is not reliable or accurate (according to USGS/WHOI). The Northstar receiver was used for bridge navigation and line running. Although a monitor from the Megapulse/IBM was on the bridge, (with waypoint navigation and line running) it was not used because it was difficult to see (numbers too small) and interpret and generally not user friendly; the navigation officers preferred the Northstar. The Northstar receiver sometimes gave problems at dawn -- bad signals, erroneous course corrections and speed --- possibly because of atmospheric noise or skywave interference at long ranges from one of the transmitters. It also gave negative speed values at times. Usually during these periods, waypoint navigation would have to be restarted once good signals were acquired. Overall, the receiver was reliable for navigation and good TD's were logged. The only real problem with the Megapulse receiver occurred when, after a temporary loss of signal, the tracking gate did not necessarily lock back onto the 3rd cycle, thus giving 10 us or multiples of 10 us errors thereafter. This was caused by having the cycle selection disabled (status 4); the problem was prevented by enabling cycle selection (status 3). Carolina Beach (9960 y) went off the air for a six-hour period on March 31 (JDO90) -- a time when transmissions were needed. Alternate stations were used during the six hours but gave less accurate geometry. In addition to all the Loran receivers, a Racal-Decca MNS2000 Transit satellite receiver was available and logged on the ABC system but was not used for navigation, only for comparison to the Loran C. Daily track plots were produced showing the Loran C Northstar, Megapulse, MNS2000 and Transit/DR. Northstar and Megapulse tracks agreed well, but were offset up to lmm (up to 375m) because of the different ASF corrections and TD-Lat/Long conversions used. The observed TD's on both receivers agreed within 0.1 us. Most accurate navigation can be achieved in post-processing by using the observed TD's, applying the best available ASF corrections (from a lookup table based on position), and recomputing the Latitude and Longitude. Scientific equipment: - GLORIA III sidescan sonar system - Continuous seismic reflection profiler with 160cu in airgun, data from Geomechanique streamer fed to MASSCOMP 2-channel logger for digital tape recording; one channel fed to EPC and LSR dry paper recorders: 4 sec. sweep, 10 sec. shot rate (see Appendix A). - Proton precession magnetometer (see Appendix A) - 3.5 kHz bow-towed echosounder - 10 kHz bow-towed bottom profiler - Seas III XBT system (see Appendix A) Tabulated information: - days at sea: 27 - km of continuous data: 10,042 km (6882 km in US EEZ; 3160 km off Canada) total area covered: 208,946 km (75,998 km off Canada; 132,948 km in US EEZ) total down time: 9.86 hours total survey time: 660 hours total transit time: 24 hours Commentary: See scientific report by S.R.J. Williams, Appendix C. Obligations re-Clearance Approval; Canadian Dept. of External Affairs Letter No. TPT-0433, 3/13/87. (attached memo). Note: - The Canadian Geological Survey has possession of data acquired during the cruise off Canada. - Subsequent data processing will be coordinated with USGS personnel at Woods Hole during the remainder of this year. - Further collaboration will include joint publications of scientific interest and possibly an USGS-CGS folio of seafloor image mosaics with geological interpretation. Appendix B XBT Water column temperature profiles were collected throughout the survey area using XBT's and the Sippican MKg Oceanographic Data System. Temperature vs. depth profiles were logged on the SEAS III system and subsequently transmitted via the GEOS satellite to NOAA. Once an XBT was launched, a thermistor measured the varying temperature as the probe fell to the bottom at an assumed velocity. This temperature vs. depth profile was logged on the SEAS III microcomputer. Erroneous temperature spikes at the bottom of the profile could be edited prior to transmission to GEDS. Each profile was logged on floppy disc and hard copy profiles were obtained on a printer. For each drop three profiles were usually plotted: one of the full profile; one to depths of 200-400m where the surface layer and seasonal thermocline occur; and one to a depth of 60m just below the depth of GLORIA. See the Appendices for detailed launch procedures and listing of XBT deployments. During the survey this data was not used quantitatively --- i.e. to correct GLORIA images for refraction --- but as a planning aid and to confirm the existence of warm core rings. Reduced sonar ranges were observed in areas of high thermal gradients near the fish depth and in areas of warm core rings. XBT's were dropped once per day and attempted to give good coverage of the work area. Six model TS's (max. depth 460m) and twenty-one T5's (max. depth 1830m at 6 knots ship speed) were dropped. Maximum depth reached with the T5's was 1650m due to the 8-knot ship speed. About 90% of the drops were successful only a few had to be repeated due to snags in the streaming cables or in rough seas. The port quarter proved to be the optimum launch position, regardless of wind direction or sea state. The deck-mounted launcher would probably work as well as the present "pole" system. The general trend of the profiles was varying gradients in the surface and seasonal layers (temperature variations up to 8 degrees) to depths of 200-300mi then the main negative thermocline to about 1000m; then a relatively constant temperature near 4 degrees C to the bottom (1650m). An exception was drop #62 that showed a positive thermocline to depth 700m and then a negative thermocline to 1600m; also the temperature below 1000m was much higher at 9-7 degrees. Other interesting profiles were #56 and #63 (11 miles apart) which showed a cold layer at depth 75-100m between two warm layers. Farnella N. Atlantic US EEZ Leg III Mar-Apr, 1987 Report by SRJ Williams. (Saved as L387REP on disk) CONTENTS INTRODUCTION PERSONNEL CRUISE SUMMARY SURVEY PATTERN EQUIPMENT Gloria, SRP, 3.5, PES, Magnetometer, XBT NAVIGATION EXTERNAL FACTORS GEOLOGY MOSAICS PHOTOGRAPHY MISCELLANEOUS CONSUMABLES FIGURES 1. Survey tracks (Planned) 2. Survey tracks (Actual) 3. Loran C station coverage 4. Gulf stream analysis charts example 5. The Mosaic 6. Chart boundaries 7. Sea surface Isotherms 8. XBT profile examples 9. XBT datasheet example APPENDICES 1. XBT deployments 2. XBT datafiles or diskette. 3. Photographic consumables 4. Seismic analogue records: Gloria, PEG, 3.5 kHz, SRP. 5. Navigation NARRATIVE The Farnella sailed from Woods Hole on day 087 and arrived in the survey area west of Hudson Canyon at 0200/088. The gear was streamed by 0800/088 and line one commenced in shallow depths along the Slope running east. Lines 2 & 3 were completed in a parallel orientation by 0456/093 although much of Line 2 was dogged by bad weather. The separate Canadian survey commenced at 0456/093 and continued, with good ranges and no major interruptions, until 0003/101 although weather conditions were sometimes marginal during the later stages The USGS survey then recommenced with principle lines in a NW-SE or E-W orientation The lines were run parallel with a separation of approximately 12 NM. Range was restricted by the Gulf Stream's warm core rings and associated currents of up to 4 kts. (see Figure 4). The allotted area was completely surveyed by day 113 whereupon 4 short lines were run to repeat coverage of areas of special interest. The gear was retrieved on Day 114 at 1600, and the ship docked at Woods Hole, early morning on Saturday, April 25, marking the end of a highly successful cruise. SCIENTIFIC PERSONNEL IOS E. Darlington GLORIA Engineer S. Williams Geologist R. Walker GLORIA Engineer D. Gunn Photographer M. Gooden Workshop L. Wedlock (RVS) Computing M. Dobson (Aberystwyth Univ.) USGS (Woods Hole) D. O'Leary Geologist J. Hughes-Clark (Dalhousie U.) Geologist E. Schmuck (USGS) Watchstander/Collator R. Sparkes (GSC) Watchstander/Collator G. Costello (GSC) Watchstander/XBT J. Vaughan (Menlo Park) ET SHIPI'S CREW M. Patterson Master J. Cannon Mate I. Newsome 2nd Officer M. Baldwin Chief Eng. G. McCain 2nd Eng. C. Cook 3rd Eng. G. McFadden Cook E. Merrin 2nd Cook R. Valiente Steward A. Thompson Bosun J. Springal Seaman T. Sayers Seaman M. Brooks Seaman CRUISE SUMMARY (all times GMT). Day 087: Sailed from Woods Hole at 1500. Steamed towards Hudson Canyon. Emergency drill after dropping pilot. Day O88: 0230 Deployed PES fish. 3.5 kHz fish damage found and case replaced after reaming boltholes. Ship power off for cooling pipe repair. 3.5 kHz fish deployed. After 30-min. wait to check repair OK Gloria, Magnetometer & SRP deployed. All equipment OK at SoL 1B at 0900. 1445 Recovered gear for further engine repairs. 1806 Gear redeployed and logging restarted. Day 090: 0100 Weather deteriorating progressively, data quality also. 0200Eol 1, SoL 2. 1900 30 mins of GLORIA data lost due to 240V power failure to portable cabin. Problems with Loran Navigation due to failure of Carolina Beach station on US chain (see Figure 2). Northstar returned to Nantucket for several hours. Day 091: Continued poor weather and poor Gloria data (15 degrees of yaw). 1000 Weather moderating. 1945 Eol 2F, Sol 3A at S.W. survey boundary. 1805 an extra layer of GLORIA cable was let out to spread wear. Day 092: GLORIA signal attenuated due to Gulf Stream Gyre (Warm Core Ring, WCR). Day 093: 0456 Commence survey of Canadian area with line C1. 1900 Increased gain on starboard GLORIA channel from 12 to 18 dB. Marked improvement in range. Day 094: Seas calm to force 1. No swell. Good data. 2300 Strong biological interference at dusk. Day 095: 1200 Force 3 increasing Day 096: 0516 Disabled the MNS2000L as it was playing up. Force 4-5. Day 097: 1315-1412 PES fish cable fouled by fishing floats, slowed to clear. Day 099: Megapulse interfaced to ABC and logging. 0100-0300 Airgun pressure hose problems. 0652-0926 Problems with GLORIA PPA's tripping causing stripy records. c 2300 weather deteriorating, dropouts Day 100: Weather ameliorating. 1900 rapid sea temperature changes. Gloria short-circuits 3 times. Day 101: 0003 End Canadian survey. Restart USGS survey. Close encounters with submarine, whale, and light table. Nice views of seamount. Day 102: Lifeboat muster. Poor ranges, dropouts Day 103: 0547 Northstar jittery. Thunderstorm. Wake-like interference on GLORIA. Swell building. Day 104: Heavy rolling but data OK on NW-SE tracks Day 105: Swell decreases Day 106: Lots of GLORIA dropouts Day 107: Sea state worsening steadily Day 108: 0736 (Line 18) Waxy fuel from Woods Hole causes engine problems, causing generator problems, causing electronic mayhem in the lab. GLORIA and ABC disabled.1111 back on line after loop for reshooting. 2021 (Line 19) Another generator crash with similar results. 2219 back on line for reshooting. Day 109: Mysterious disappearance of hours of magnetometer data from ABC Day 110: 0030 Line 20A waypoint of mix-up. Dogleg required. Day 111: 0200-0300 Significant bio-interference on GLORIA. Continued problems on GLORIA range and ship velocity. Day 113: 1759 Completed coverage of allotted area. Commenced turn for 4 short extra lines to the east for repeat coverage and extra profiles. Day 114: 2000 Terminated data collection. 2130 All gear retrieved and ship underway to Woods Hole SURVEY PATTERN The Leg II area remained uncompleted for Leg IV to fill in at a later date. In A special arrangement 7/8 days of survey had been allocated to Canadian Researchers although the detailed allocation of ship time was not formalized prior to sailing. The original planned survey grids are shown in Figure 1. The survey started with WSW to ENE lines 1,2, and 3 in US waters along the Continental Slope. The quality of GLORIA data and lateral range obtained varied with sea conditions. Much of Line 2 being of poor quality At the end of Line 3 we turned C1 at the start of the Canadian survey. The Original Canadian survey area (Figure 1) was not rigidly defined. The eventual tracks are shown in Figure 2. The survey was restricted to areas with depths greater than 2000 m. for two reasons: a.) in order to maximize areal coverage and b.) because the Rise was of more interest than the Slope. Main track lines were run in a NW-SE direction, perpendicular in the west, becoming more oblique to slope eastwards. This resulted in better imaging of slope-perpendicular channel topography. Correlation of GLORIA images with 3.5 kHz. and SRP were less efficient when running near-parallel to the grain but this was considered acceptable in view of existing 3.5 kHz coverage. The US recommended NW-SE tracks in the east of the EEZ. Some lines were extended slightly to cover local seamounts. Part of Line 2 was reshot as Line 8 from E-W and line 9 was run W-E before continuing the general NW-SE grid. This contour oblique track line orientation, although less efficient than contour parallel lines, produced better quality data in the strong southwesterly swells and facilitated adjustment to local variations in GLORIA range induced by water temperature anomalies (Warm Core Rings shed by the Gulf Stream). The variation in range with water depth was not great in this part of the survey and so no fanning-out of the lines was required. A 1:750,000 transverse Mercator chart was used which showed bathymetric contours (200, 1000, 2000, 3000, and 4000 m.) and the EEZ boundary. A 30' grid as well as 1' ticks on the grid lines made plotting much easier than previously. On this chart were plotted the hourly ship positions and GLORIA ranges for planning survey lines on a day to day basis. By mistake a projection latitude other than 28d N (as used for the Leg II plotting) was used which complicated accurate meshing with Leg II. For simplicity a straight-line boundary was drawn within the area of complete Leg II coverage and it was to this line that Leg III extended. EQUIPMENT GLORIA On starting the Canadian survey it was noticed that signal amplitude on the starboard channel was relatively low. (Previously this had been obscured by topographic effects on contour parallel lines.) The gain was increased from 12 to 18 dB with a marked improvement in record quality. Problems with the PPA's at times resulted in stripy gain variations in the data, but it should be possible to remove this with the MIPS. The system crashed twice on Day 108 due to the generator problem. Between 2100 and 2330 on Day 106 a new and unexplained type of data loss was noticed on the records. SRP (by J.V.) The system comprised the IOS SRP rack (using only airgun triggering circuitry and streamer preamplifiers for channels 1 and 4); the MASSCOMP computer digitizing and recording system; 2 graphic recorders (Raytheon LSR 1807M and EP 3200); a 160 cu in PAR 1500 airgun; various filters, amplifiers, and the extensive support gear for the airgun a Geomechanique 2 element hydrophone. The standard set-up on this cruise was: 10 sec shot interval 4 s recorder sweep 0-4 s deep water delay Either 15-300 Hz BP, (LSR) or 75-150 HZ (EPC) Channel I to LSR & EPC Channels 1 and 4 to MASSCOMP 6 sec data record per MASSCOMP data file. The system collected data from 0807/088 to 2007/114: a total of 660 hours/ 27.5 days, with the following downtimes: 088 1450-1838 Ship engine failure 093 1500-1535 Airgun swap 098 1643-1727 Airgun swap 099 0102-0253 Replaced airgun hose 105 2100-2236 Airgun swap 108 0822-0841 Ship engine failure 108 1519-1522 Circuit breaker tripped 108 2059-2110 Turned off for sharp turn 110 1647-1732 Airgun swap Total downtime: 9.9 hours (1.5%) Problems with the Masscomp occurred due to variable line voltages following the 2 mid cruise engine failures An unexplained small time jitter occurred intermittently on the graphic recorders Further detail is provided in J.V.'s report. All in all, very reliable. 3.5 kHz PROFILER Damage to the fish body during Leg II caused a delay in deployment whilst the upper casing was replaced and the boltholes reamed out. The data were replaced at 1 sweep on a Raytheon LSR. This only has a facility for L-R sweep. It would greatly ease interpretation if the sweep direction could be reversed as with the EPC. Again, it is worth stating that a heave compensator would do wonders for data quality in all but the calmest of seas. 10 kHz PRECISION ECHOSOUNDER (PES) This system performed throughout the cruise. Depths were measured every 6 min. entered in a log, annotated on the records, typed into the ABC computer logging program and then used for slant range correction of GLORIA data. Bathymetric soundings were plotted along track at 1:375,000 scale at the end of the survey but was not particularly clear. It was noticed at one stage that depth readings given by the PES and 3.5 kHz. were up to 100 m. different. This was attributed to the steeply sloping seabed. MAGNETOMETER (by J.V.) The Geometrics G-801 Proton Free precession magnetometer performed well. Data was collected between 088/0911 and 114/2004 (27.5 days). The only downtime was due to ship power supply failures Data were displayed on a pen chart record and logged by the ABC. Sampling rate 1 per 3 sec. The ABC logged 6 BCD for each sample, the recorder displayed the 2 least significant digits. Between 095 2000 and 097 0200 the ABC registered the 2 middle digits as zero and so data had to be transferred manually from the pen records for this period. Values and profiles were plotted along track at the end of the cruise. XBT See Appendix 1. NAVIGATION The Northstar unit utilizing Loran C was used throughout and considered satisfactory except when Loran signals were disrupted on rare occasions for up to 20 mins. Slight jumps also occurred when the unit was jumping between stations. MNS2000 loran fixes were generally inferior for prolonged periods. This gave wildly inaccurate positions. MNS2000 transit satellite/dead reckoning fixes were often very bad due to bunching of satellites and extreme current drift velocities. Megapulse Loran C data were logged on floppy disk but could not initially be supplied to the Level C logging system. LW devised an interface and Megapulse data were logged continuously early in the cruise except for when the ABC crashed. Its results were generally comparable to those of the Northstar system now that asf correction factors was available. Prior to the cruise the Canadians were anxious about using Northstar because of some previous bad experiences. The Trimble GPS system was unfortunately unavailable. Daily plots were produced showing Northstar, MNS2000 and satellite/DR tracks with hourly annotation, 10 minute ticks and 2 minute sampling. Early in the cruise plots of Megapulse data were produced on a micro computer at a similar scale but no significant differences from the Northstar tracks were noted. It has yet to be decided which navigational system will be used for the MIPS work although the general feeling is that Northstar is best, with Megapulse filling in the gaps. See also Appendix 5 EXTERNAL FACTORS The Gulf Stream influence was expected to be greatest in the south of the area (see Figure 4), but warm core rings (WCR) drifting further North were predicted to cause additional obstacles. Indeed, at certain times up to 25- 30d of helm were required to maintain course on Line 2. Severe loss of GLORIA was caused by refraction. Loss of ground speed control also occurred (up to kts. depending on track direction). Ship speed variations and water temperature (GLORIA, XBT, and compressor intake) indicated when we were in the Stream or a WCR. The position of the Stream and WCR's varies fairly slowly according to the weekly charts. (Figure 4). Figure 7 shows the compressor seawater inlet -- temperature measured in Canadian survey. It is expected that major problems will be experienced on Leg 5 west of Florida. Plankton and fish were seen frequently in the water column on GLORIA LSR and PES, sometimes degrading GLORIA data, especially during the upward plankton migration at dusk. There were frequent bursts of ship noise from passing vessels. Correct phasing of the SRP prevented interference on GLORIA records. Strong multiple hyperbolic signals were recorded at certain times and attributed to a submarine or transponder. GEOLOGY For more detailed descriptions please see the summaries of D. O'Leary and J. H-C. US EEZ The survey area continues to the north of the Leg II area with no immediate changes in geological style. The Slope is intensely canyoned. In the west of the area the distribution of major features such as canyons and large mass flow deposits was much as indicted echotype character map of Vassallo, Jacobi and Shor in the Ocean Margin Drilling Atlas but the detailed morphography was better resolved. On the Slope the surficial geology was much as described by O'Leary's Open File Report. There was noticeably good correlation between topographic features and published bathymetry. Large mass flow pathways up to 10's of km wide extended 10's of km across the rise from the base of the slope. These are imaged in great detail. Reflectivity variations on sonographs in the vicinity of mass flow deposits can sometimes be correlated with the 3.5 kHz echo character. Elsewhere smaller incised channels run from individual canyons across the Rise with varying degrees of sinuosity. Evidence of slumping is seen on margins of the channels which extend across the rise. Canyons run largely perpendicular to the Slope, especially the smaller ones. Patchy or wave-like variations in reflectivity which boarder mass flows or channels may have been formed during the overbank deposition or by subsequent reworking by local benthic currents. Large areas of layered, parallel laminated (hemipelagic/contourite) sediments extending down 40 m subbottom occur between major mass flow pathways. The bedding varies from flat to undulating (hemipelagic drape) to regularly undulating (sediment waves with a c 1 km. wavelength). Intermediate styles are common and minor low-angle unconformalities are occasionally visible. In general, the evidence for along-slope sediment is greater than in the Leg II area. Isolated 'massifs' occur, surrounded by debris flows and capped by hemipelagic laminated sequences. These are probably upstanding erosive remnants (rather than olistostromes). Their margins are frequently onlapped by mass flow deposits The airgun records are of fair to good quality. The long bubble pulse obscures much stratigraphic detail. Perhaps post cruise deconvolution can do something for this? SRP data revealed major (X, Au, and A*) and minor unconformalities, the effect of salt swells and shallow igneous bodies as well as the erosional nature of the canyons. Identification of epidermal mass movement decollement zones was more speculative. Minor faulting was detected but correlation with surface scarps was only speculative. Seamounts are imaged well and rugged basement reflectors can be traced several kilometers from their margins. On the Slope canyons are seen to be incised into a sequence of resting on a locally prominent unconformity. A prominent BSR seen in parts of the area at c 0.6 s TWT subbottom may be attributed to a clathrate/free gas interface. Some buried channels were seen on the Rise but the general situation there is a laterally-variable one of low-angle unconformalities separating local sediment lenses. Major channels such as the Hudson are incised as deep as 300 m. into older rocks with little evidence of levees or older, underlying channel base facies. The channel sides are as steep as 1 in 5. CANADIAN AREA The survey only extended to the lower part of the slope where canyons are fairly broad and shallow. The area was dominated by a complex of lenticular mass-flow deposits with a sheet-like or braided surface expression. Channels were relatively shallow but fairly extensive. Oblique crossings by 3.5 kHz did not provide optimum definition. Margins of deposits were not well defined. Extensive areas of hummocky topography are caused by slides and or sediment waves. Some slide scars are evident on the Rise. MOSAICS See section in the Leg II report. For future reference the following production schedule was implemented except for days when logging interruptions occurred. GMT LOCAL 0700 0200 2nd Gloria cartridge full. 1300 0800 Produce 24 hr. track plot and SPDL values on ABC computer. 1400 0900 Start laser printing (after EXACTLY two hours warm up) 1600 1100 Start developing film. 1730 1230 Produce contrast test prints 1745 1245 Print photos (64 copies) 2100 1600 Prints dry. Start mosaicking (data from 0700-0700Z, delay 28-14 hours). The minimum time from ending a Pass to having dry prints is about 4 hours. 8 copies of each print were produced: 1,2, and 3 for IOS for mosaic, spare and archive, 4,5, and 6 similarly for either USGS or GSC, 7 and 8 for M. Dobsom (apprentice mosaicker). PHOTOGRAPHY A Test Pass (No. 29 from Leg II) was used for quality control between films with favourable results, the gray scales are not very helpful. Continued problems with the enlarger luminosity cropped up intermittently; eventually it was thought to be due to using paper from different boxes, despite equivalent purchase dates. Beware of the this! The laser printer will give variable intensity negatives unless the warm up period is standardized. See comments in Leg II report re paper size. MG expertly plumbed-in the large water filter canister beneath the darkroom sink. 3.5 kHz. and some SAP analogue equipment were photographed for onboard interpretation purposes. 2 days data can be photographed and developed in an hour and later printed in an hour. The laser printer technical film gave good results using an Olympus OM-20 SLR at 4 feet with a signal dedicated flash gun attached (with diffuser). Four rechargeable AA-size NiCad batteries were sufficient for at least 72 shots. Attempts were made to photograph the mosaics using two angled floodlights with moderate success. MISCELLANEOUS An old problem: in bad weather water enters the forward hold from somewhere and sloshes about, sometimes getting into the electronics of the airgun compressors. The hazard of slippery metal decks was reduced temporarily by painting with sand-mixed paint, but a better solution is required. Air gun retrieval was complicated by the sticky hydraulics of the cable winch. A gate cut in the gunwale and/or a special davit would make deployment less hazardous. Problems with the hydraulics of the GLORIA winch persisted. Insertion of brass bushes to match the brass liners on the air guns instead of polythene ones solved the seating problem. There seems the be incomplete communication at Leg changeovers regarding the serviceability of survey equipment (e.g. 3.5 kHz fish damage) and this could subsequently lead to avoidable downtime. This should be avoided by compiling a written log or fault list instead of relying, as at present, on oral communications. The ship's crew were, as always, helpful and friendly and this is much appreciated. A list of suggestive improvements has been posted in the wet darkroom (selves, light, etc.) CONSUMMABLES Lists of photographic and general consumables and rate have been produced. These lists are found on the GLORIA disk for the BBC. Please update as required. There appear to be no firm guidelines as to who is responsible for restocking what but please check and reorder for the next Leg either from IOS or USGS (bulky or heavy materials) Present and ordered supplies should be sufficient for the 12 day gap-filling leg from Woods Hole to Norfolk. Appendix 1 Water column temperature profiles were collected throughout the survey area using XBT's and the Sippican MK9 Oceanographic Data System. Temperature vs. depth profiles were logged on the SEAS III system and subsequently transmitted via the GEOS satellite to NOAA. Once an XBT was launched, a thermistor measured the varying temperature as the probe fell to the bottom at an assumed velocity. This temperature vs. depth profile was logged on the SEAS III microcomputer. Erroneous temperature spikes at the bottom of the profile could be edited prior to transmission to GEOS. Each profile was logged on floppy disc and hard copy profiles were obtained on a printer. For each drop three profiles were usually plotted: one of the full profile; one to depths of 200-400m where the surface layer and seasonal thermocline occur and one to a depth of 6L71rn , just below the depth of GLORIA. See the Appendices for detailed launch procedures and listing of XBT deployments. During the survey, this data was quantitatively --- i.e. to correct GLORIA images for refraction --- but as a planning aid and to, confirm the existence of warm core rings. Reduced sonar ranges were observed in areas of high thermal gradients near the fish depth and in areas of warm core rings. XBT's were dropped once per day and attempted to give good coverage of the work area. Six model T6's (max. depth 460m) and twenty-airie T5@s (max. depth 1830rn at 6 knots ship speed) were dropped. Maximum depth reached with the T5's was 1650m due to the 8 knot ship speed. About 90% of the drops were successful ; Only a few had to be repeated due to snags in the streaming cables or in rough seas. The port quarter proved to. be the optimum launch positions regardless of wind direction or sea state. The deck-mounted launcher would probably work as well as the present "pole" system. The general trend of the profiles was varying gradients in the surface and seasonal layers (temperature Variations up to 8 degrees) to depths of 200-300m; then the main negative thermocline to about 1000m; then a relatively constant temperature near 4 degrees C to the bottom ( I 650m) . An exception was drop #62 which showed a positive thermocline to, depth 700m and then a negative thermocline to 1600m; also the temperature below 1000m was much higher at 19-7 degrees. Other- interesting profiles were #56 and #63 (11 miles apart) which showed a cold layer at depth 75-100m between two warm layers. Appendix 5. Navigation by G.C. Loran C in the hyperbolic mode was used throughout the survey area for positioning. Four receivers were operational: 2 Megapulse Accufix 500's a Northstar 7000; and a Racal-Decca MNS2000. Time Differences (TD's) and Lat/Long from the Northstar and MNS2000 were logged on the IOS ABC system for the entire cruise. The 2 Megapulse receivers were interfaced to separate IBM PC9sg where the observed TD's were converted to Lat/Long and all data logged on floppy disc and were printed out every 5 minutes. As of April 8 (JD 098) data from one of the Megapulse/IBM's were logged on the ABC system, but near the end of the cruise it was discovered that a bug in the program (making the tenth of a microsecond (us) digit = 0) Tendered the TD's useless. A single "mean" ASF correction for each Master/Secondary pair was determined from the available sources --- DMA and CHS/BIO --- and applied to the observed TD's on the Megapulse/IBM system for the entire Survey, as shown below. CHAIN SECONDARY ASF 9960 W Caribou +1.0 its X Nantucket +2.8 Lis Y C. Beach +2.4 its 5930 X Nantucket +2.1 Lis Y Cape Race +1.4 LtS The Northstar receiver had ASF corrections built in at time of manufacture. There was a Lat/Long bias available but was not used. Apparently the Northstar receiver, has errors in the TD to Lat/Long conversion and is not reliable/accurate (according to USGS/WHOI). The Northstar receiver, was listed for bridge navigation and line running. Although a monitor from the Megapulse/IBM was on the bridge (with waypoint navigation and line running) it was not used because it was difficult to see (numbers too small) and interpret and generally not user friendly; the navigation officers preferred the Northstar. The Northstar receiver sometimes gave problems at dawn --- bad signals, erroneous course corrections and speed --- possibly because of atmospheric noise or skywave interference at long ranges from one of the transmitters. It also gave negative speed values at times. Usually during these periods, waypoint navigation would have to be restarted once good signals were acquired. Overall, the receiver was reliable for navigation and good TD's were logged. The only real problem with the Megapulse receiver occurred when, after a temporary loss of signal, the tracking gate did not necessarily lock back onto the 3rd cycle, thus giving 10us or multiples of 10us errors thereafter. This was caused by having the cycle selection disabled (status 4) the problem was prevented by enabling cycle selection (Status 3). Carolina Beach (9960 y) went off the air, for a six hour period on March 31 (JD090) at a time it was needed. Alternate stations were listed during this period but giving worse geometry. In addition to all the Loran receivers, a Racal-Decca MNS2000 Transit satellite receiver was available and logged on the ABC system, but was not used for navigation; only for comparison to the Loran C. Daily track plots were produced showing the Loran C Northstar, Megapulse, MNS2000 and the Transit/DR. Northstar and Megapulse tracks agreed well, but were offset up to lmm (up to 375m) because of the different ASF corrections and TD-Lat/Long conversions used. The observed TD's on both receivers agreed within 0.1 us. Best navigation can be achieved in post-processing by using the observed TD's, applying the best available ASF corrections (from a lookup table based on position) and recomputing the Latitude and Longitude.