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doi:10.2204/iodp.proc.318.103.2011

Operations

Wellington port call

Expedition 318 began when the first line was secured to Aotea Quay, Centre Port, Berth 5, in Wellington, New Zealand, at 1420 h on 3 January 2010. All times in the operations section are given in local ship time unless otherwise noted. Initially this was Universal Time Coordinated (UTC) + 13 h. During transit to the first site, the ship’s clocks were set back 1 h at 1200 on 12 January to UTC + 12 h and then another 1 h at 2400 on 13 January to UTC + 11 h, where it remained for the duration of the expedition.

As soon as routine customs and immigration formalities were concluded, off-loading of surface freight was initiated. The expedition United States Implementing Organization staff and Co-Chief Scientists boarded the ship on 4 January. In addition to routine replenishment of expendables and off-loading of the previous expedition’s cores and returning freight, we loaded 740 MT of marine gasoil, repaired one of the thrusters and a propulsion motor, conducted laboratory/ship tours for guests and visiting dignitaries, mounted the wind wall on the core receiving platform, and installed a new touch-screen rig instrumentation monitor in the drillers console.

Because this was a high-latitude expedition that operated in the challenging environment off the coast of Wilkes Land, Antarctica, two critical specialists were added to the shipboard team. A senior weather forecaster with previous IODP expedition experience joined the vessel to provide timely analysis of the complex weather environment of the Southern Ocean. A seasoned ice observer with extensive familiarity with both Arctic and Antarctic regions also joined the expedition. The combined skill set provided by these participants enhanced the safety of the vessel and optimized the ability of the crew to maximize on-site operational flexibility.

Transit to Site U1355

The vessel departed on the 1847 nmi journey to the first site when the last line was released from the dock at 1045 h on 9 January 2010. The vessel sailed at full speed, except for a short time during which the brushes on a propulsion motor (16 A) were replaced. By midnight on 9 January, the ship had sailed 116 nmi at an average speed of 9.3 kt.

The ship transited south-southwest off the east coast of New Zealand’s South Island. Preliminary analysis of ice coverage appeared to be promising for our first planned site (U1360) with temperatures in that region of 0.2°C, winds from the east-southeast increasing to 35–40 kt, and cloudy conditions with occasional snow or sleet.

The vessel passed within 30 nmi of Auckland Island on the morning of 12 January. Once the vessel moved south of the protection of Auckland Island, it was exposed to the open expanse of the Southern Ocean and the powerful low-pressure systems that populate this region. The vessel negotiated through intense winds and sea conditions from 12 January until the morning of 15 January. Frequent course changes and reductions in speed were made to avoid the most intense parts of a large and severe low-pressure system that was crossing the projected ship track. Even though the vessel remained on the outer edge of the system, the combined sea and swell reached 40 ft and the winds were clocked at as high as 60 kt. Vessel motion ranged from moderate to heavy and on one occasion the ship experienced a 13° roll. The ship’s clocks were set back 1 h at 1200 on 12 January to UTC + 12 h and then another 1 h at 2400 on 13 January to UTC + 11 h.

The vessel began to ride more smoothly in improving sea conditions by the afternoon of 15 January and was proceeding at nearly 10 kt to Site U1360. During the evening, the first penguins were observed, hinting that we might be approaching ice-strewn waters. At 0345 h on 16 January, the first iceberg was spotted on radar at 9 nmi and then visually observed at 5 nmi through the fog and mist as it passed on the port side. It was pinnacled and rigged and estimated to be ~300 ft long and 50 ft high. There were also a few growlers in the vicinity. During the day, the vessel speed was reduced when fog and mist reduced the visibility to <⅛ nmi. At 0440 h on the morning of 17 January, ship’s radar picked up a large iceberg at 17 nmi with a calculated closest point of approach of 7 nmi to starboard.

By midnight on 16 January, the vessel had traveled 1505 nmi at an average speed of 8.3 kt. The estimated time of arrival on site was mid-morning on 18 January. Satellite analysis of ice coverage in the region indicated the drill site area was mostly free of large icebergs and floes. The winds at our first site were forecasted to pick up and peak at ~40 kt the evening of 18 January and then decrease. Temperatures were expected to be ~0°C. The new long-range outlook through 22 January indicated good weather conditions on site.

Throughout the week, the drilling crew continued preparations for drilling operations in the severe Antarctic weather conditions. A wind wall was constructed around the drill floor, exposed piping (heating, air, drain, and water) was insulated, electrical lines were run for heaters in the mud pump room and behind the drawworks, and external space heaters were tested.

As we approached Site U1360 at the reduced speed of 8 kt, the captain received an updated satellite image from the National Ice Center that indicated a large tongue of ice in the direct path to Site U1360. This was obscured in previous imagery by cloud cover. This necessitated adding a dogleg in the track to Site U1360 so that we could steer around the leading edge of the tongue.

As the vessel altered course and speed in heavy mist and fog, large icebergs began to appear on the radar and a few growlers were spotted visually. When the fog suddenly cleared, icebergs of various shapes and sizes were observed around the vessel. The vessel proceeded at slow speed attempting to approach Site U1360 amid the ice when the weather deteriorated during the afternoon of 18 January. With the winds gusting to 35 kt and accompanied by snow and reduced visibility, the effort to reach Site U1360 was suspended 19 nmi short of the objective until ice conditions were more favorable. The captain altered course to Site U1355 located ~167 nmi to the north-northwest. The most recent satellite pictures indicated that Site U1355 appeared to be free of floating ice.

Site U1355

The vessel exited the hostile ice conditions and proceeded at an average speed of 6.4 kt to Site U1355, arriving on site at 1045 h on 19 January 2010. The circuitous voyage from Wellington to the first site covered 2021 nmi at an average speed of 8.5 kt. During the voyage from the area of Site U1360 to Site U1355, no icebergs were spotted on the radar or visually.

An APC/extended core barrel bottom-hole assembly (BHA) was made up with an 11 inch bit and lowered to the seafloor. The initial mudline attempt was made at 0705 h on 20 January with the bit at 3735 meters below rig floor (mbrf; 5.7 m shallower than the corrected depth of 3740.7 mbrf inferred from the precision depth recorder). When the core barrel was recovered, we found that the bottom of it had broken off at the connection joining the two 4.5 m nonmagnetic sections. To test the nature of the seafloor, the driller gently tagged seafloor with the bit at ~3740 mbrf. The bit was slowly rotated and a mild increase in torque was observed, indicating that the seafloor was firm but apparently not unusually hard.

Another mudline core was attempted using the more durable standard steel core barrels with the bit positioned at 3735 mbrf. The pressure bleed-off indicated a full stroke but the core winch operator was unable to recover the APC core barrel with the coring line. For nearly 1.5 h, the core winch operator and driller tried various techniques to recover the corer with the coring line without success. The only recourse was to recover the drill string. The bit was back on the rig floor at 2225 h on 20 January. This second APC core barrel was also broken off. Once the remains of the core barrel were cleared from the bit throat, it was decided to attempt a spud with the RCB coring system.

An RCB BHA with a new C-4 9⅞ inch bit and mechanical bit release were made up and deployed. The seafloor depth was again confirmed at 3740.0 mbrf (3729.0 mbsl) by the driller gently tagging the bit on the seafloor. Coring in Hole U1355A was finally started at 0905 h on 21 January. The first core advanced 3.5 m but recovered 5.3 m of core. This could have occurred because of uncertainty in the precise seafloor depth and/or by the drill bit repeatedly tagging the seafloor as a result of ship heave. RCB Cores 318-U1355A-1R through 4R penetrated from 0 to 31.7 mbsf and recovered 14.95 m (47%) (Table T1). The cores recovered unconsolidated coarse sands and gravel, so the recovery was quite remarkable. However, coring had to be terminated because of unstable hole conditions caused by the coarse and unconsolidated sediments.

We decided to abandon this site and find an area less hostile to coring. We considered making another attempt to return to the shelf sites, but based on remote sensing data and information from a research vessel in that region it was felt that ice conditions in the area had not significantly improved. Instead, we decided to move to Site U1356, located 82 nmi west-northwest of Site U1355. After a total time of 2.8 days on site, we departed Site U1355 at 0600 h on 22 January.

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