IARC ice observers have found themselves rather busy over the last couple of days, as they were able to access ice floes two days in a row to conduct sampling.
The first visit, on the 7th, was a substantial operation involving the deployment of multiple buoys. A floe of considerable size and thickness was needed to accommodate the equipment and the 14 crew members assembled to assist in the undertaking. This proved difficult, as the ship was traveling in a vast expanse of young grey ice, with only an occasional intrusion of cake-size floes of multi-year, or second-year ice. Luckily, as the recon helicopter was making it’s way back to the ship, a suitable floe was found. The large group descended onto the floe late in the afternoon, and worked as quickly as possible given the task at hand, time restriction due to dwindling daylight hours, and cold temperatures.
IARC ice observers were able to drill at 10m intervals along a 100m line, for an ice thickness measurement survey. The line ran perpendicular to the buoy operations, and traversed over several small ridges. Depths ranged from 37cm to 354cm. Several large pockets were found near the middle of the line, approximately 25-35 cm down, indicating a rafting of at least two ice floes or blocks. Thinner ice measurements further down the line towards the floe edge revealed newly formed ice. Two core samples were taken at the beginning and end of the line. The sample at 0m measured 207cm, and the sample at 100m measured 44cm. Production on the later, however, was interrupted by an abrupt call back to the ship. The traditional core temperatures at 10cm intervals were taken, and then the core processing was completed aboard the ship.
Ice operations on the 8th were considerably different. On this day, only one buoy was in need of deployment, and while a sizeable piece of multi-year ice was preferred, it was not a necessity. Ultimately, a small cake size floe was chosen. Due to the size of the floe, IARC observers did not lay a transect line, but decided to concentrate their efforts on taking ice core samples instead. Three cores were taken; an 83cm core came from rafted multi-year ice, a 22cm core was pulled out of this season’s grey-white ice, and the final 156cm core shared the same area of the floe as where the WHOI ITP#44 was deployed. It should be noted that the first core hole was actually greater than 83cm, but an unusually hard surface prevented the ice auger from penetrating beyond approximately 250cm. The situation was perplexing, as the gear, including the corer’s cutting bits, the power source and all connections in between had been in proper working order. The measurements signaled to the ice observers that this floe was rafted multi-year ice with a void between the surface layer and the resilient lower floe/block beneath.
The past two ice visits concludes on-ice work scheduled for cruise participants this year. The remaining days at sea will now focus on retrieving and redeploying another WHOI mooring (BGOS-D), and continued water sampling near the Banks Island shelf break or within the Canada Basin, as time permits.
~ Alice Orlich and Heidi Isernhagen