12/27/01 2 pm
64 12 S
61 13 W
Cloudy with occasional snow showers after a beautiful morning
Beautiful sunset starting around midnight last night. Clear skies, calm winds and temperature right around freezing as we came on shift.
A perfect night for working on deck bringing in a Jumbo Piston Core (JPC) to start. The JPC is designed to collect a very long core. This one was configured for 90 feet and we recovered about 85 feet of sediment. This core preserves the climatic record for the region dating back over 12,000 years. Earlier in the evening the day shift also ran a JPC operation in a nearby cove and recovered close to 90 feet of sediment. The Nathaniel B. Palmer is the only research vessel in the Antarctic collecting these very large cores.
(Click image for larger version.)
The JPC operation is quite involved. Initially a coring site is examined with the Bathy 2000 echosounder to determine the sediment thickness. A test core is done with a 3 meter Kasten core to determine the character of the sediment. The JPC consists of 10 foot segments of 5 inch diameter steel pipe connected with couplers to form the required length. The sections are then lined with 10 foot sections of thick walled PVC pipe. The entire system is constructed on the starboard rail of the back deck. Once assembled, JPC is pivoted to a vertical position with the majority of it in the water. A coil of slack wire is made to allow the JPC to free fall a short distance to the bottom, then release arm and trigger core are attached. One crane lifts the trigger core over the side so that it is free and holding tension on the release arm. A second crane lifts the 5000 lb main weight with the core barrel attached from a special cradle and the entire unit begins it's trip to the bottom. When the trigger core impacts the bottom, weight is released from the release arm. The release arm drops the JPC which free falls the length of the coiled wire and penetrates the sediment. A piston inside the core barrel stops at the seafloor thus providing suction as the barrel continues to sink into the sediment. A tension meter on the winch cable detects the release of the JPC from the cable. Once the core is taken the entire JPC with cores in the trigger core and (hopefully) the entire length of the JPC barrel is returned to the surface.
(Click image for larger version.) Photo caption: JPC barrel rests on the rail following a successful recovery. Top of JPC is 90 feet away near the crane tower.)
On the surface the JPC is again laid along the side rail and a hydraulic ram is used to extrude the PVC liners one at a time. Each 10 foot section of sediment filled PVC pipe is capped and carefully numbered with the station number and it's section number within the JPC.
Ideal weather during the day and night shifts allowed for two JPC's to be done in the course of around 7 hours.
(Click image for larger version.)Photo caption: Heavy iceberg blockade at the head of Brialmont Cove prevents
Following recovery of the 2nd JPC we travelled from Kayak Bay on the west side of the Gerlache Strait to Brialmont Cove on the east side. This is the area we have attempted to establish a station at a number of times so far with no success. Today was no different. Although ice conditions allowed an approach closer than before, lack of room to maneuver if the ice closed in made proceeding closer to the glacier front too risky.
Two stations were established in more open waters in the cove with sediment traps deployed at both.
Tonight we will begin an 8 hour transit to the Boyd Strait near the South Shetland Islands where another JPC operation is planned.
Cheers,
Dave
photo caption:
2 am in Kayak Bay, east side of Brabant Island. Diana Duran, Neil Basu, David Amblas and Scott McCallum prepare to unload a JPC.
