2010 Expedition to Antarctica

Week 6

Monday - Friday, February 2 - 5

Several cloudy, cold days have passed since my latest blog entry. For the past four days, we have been trying to find safe routes (leads in the ice that are devoid of shifting pack ice) in the area of Admiralty Sound. Although not an original Larissa target area, Admiralty Sound poses as a refuge for the ship as we wait for the cloudy weather to dissipate to resume helicopter operations. As the ship drifted on Tuesday and Wednesday, we deployed a yo-yo camera off the stern to document mega fauna assemblages on the seafloor. Wednesday morning brought a short opening in weather conditions, allowing us to deploy the helicopters. One of the flights employed the use of a sling-load, which involves the helicopter carrying a suspended load of gear under the body of the aircraft. We succeeded in staging some gear for a GPS station set-up at Cape Marsh on Robertson Island, but unfortunately, the weather proved too unpredictable for the team to continue work on the island. All had returned to the ship by mid-afternoon.

Thursday morning, we moved into the southern basin of Admiralty Sound to conduct a series of CTDs, Kasten cores, and an ROV dive. This area was previously covered by an ice shelf until its break-up in the 1940s. The goal of this sub-project is to document the sedimentologic characteristics of the beginning stages of ice shelf decay as well as to investigate current circulation patterns and water mass exchange with the shelf and the biologic communities on the seafloor. Conducting the sub-project will aid us in the understanding of this area in addition to allowing us to maximize our time on the Palmer as we wait for suitable conditions for helicopter operations. Thursday evening, we succeeded in recovering a 3-meter core of laminated mud. The top 15 centimeters were composed of ice rafted debris, which records the last 100 years of open marine conditions. The ice rafted debris is essentially the coarse-grained sediment, pebbles, or boulders that are released from migrating ice bergs. Curiously, we did not find any sign of biota in the sediment core. Why were there no fossils in the core? We extracted another 2.3-meter core in the Admiralty Sound on Friday morning, and the night shift is finishing the processing of the core (i.e. preparing x-ray slabs and u-channels for magnetic susceptibility analysis) as I write. Throughout the day, Lamont-Doherty doctoral candidate Debra Tillinger manned the CTD control computer, conducting a CTD every three hours for her twelve-hour shift. The time series data acquired from today's CTD deployments will help us determine water velocities at different depths in the water column. Based on past water velocity data that the ship recorded while idling, Tillinger determined that there is a dominant semidiurnal (half-day) tidal pattern at the ship's current location. Today's CTD casts will complement this data. Tonight, we hope to deploy the ROV on the bedrock knoll in the western end of Admiralty Sound with hopes to attain coral specimens for paleoceanographic and radiocarbon analysis.

Saturday - Sunday, February 6 - 7

The Palmer has been buzzing all weekend. On Saturday, Dr. Amy Leventer and Dr. Eugene Domack made it via helicopter to Cape Marsh, where they had staged gear a few days earlier, and completed the installation of a GPS station. While the GPS-stagers were out on the Peninsula, a group of us, led by University of Hawaii professor Craig Smith and Scripps professor Maria Vernet, headed out to the ice floe to drill ice cores, to sample the snow that rests on top the ice, as well as to employ the use of hydro-phones in the underlying waters. Glaciologist Erin Pettit left Lamont Doherty doctoral candidate Debra Tillinger and University of Houston undergraduate Yuribia Muñoz with a side-project to record the acoustic frequency of ice berg movements in the water. To record background level noise, the pair along with University of Hawaii post doctoral fellow Laura Grange and myself lowered hydro-phones into the water through a 1-meter hole that we drilled in the ice. The National Geographic team accompanied the ice party, filming us work as well as taking pictures of the Palmer nestled in the sea ice.

Following the ice floe mission, we deployed a mega-core, capturing seven cores that were each about 30 centimeters in length. Heading the deployment of the mega-core, Dr. Laura Grange and Dr. Craig Smith are interested in documenting the micro- and mega-fauna living in the shallow sediments and sample the cores in 1 centimeter intervals. Soon after the successful recovery of the mega-core, Dr. Domack and Dr. Leventer returned to the ship with red, wind-burnt yet smiling faces after a long, fulfilling day at Cape Marsh.

While the ship-based scientists saw clear weather, the ice camp at Site Beta was in the midst of thick blowing snow on Saturday. Apart from the weather, the team is doing well, and they are set for take-out via Twin Otter back to Rothera Station. We also heard word from the glaciology team that they had a successful flight to Flask Glacier this morning, where they have a planned AMIGOS site. Next on the agenda is to transit to Scar Inlet and install another AMIGOS unit.

Sunday morning greeted us with brilliantly clear, sunny weather—perfect flying conditions. Rested up from yesterday's efforts, Dr. Domack and Dr. Leventer headed out for another GPS installation site at Foyn Point, southwest of yesterday's station. The second helicopter also took flight with Dr. Greg Balco, accompanied by National Geographic photographer Maria Stenzel, to Sjögren Glacier. While Balco returned with several glacial erratics for radio-nuclide dating, Stenzel also succeeded in capturing some beautiful aerial photographs of the receding glacier.

While the helicopters were transiting back and forth with people, equipment, and fuel throughout the day, work continued on the ship. We deployed two mega-cores, a yo-yo camera, and a CTD south of Lockyer Island. Some of us will sleep well tonight and may have to wait until the morning for scores from the Saints-Colts showdown.

— Commentary and photos provided by Kimberly Roe '08