Monday, 24 August 2009

Day 14 – 20th August

After cruising all through the ‘night’ the boat finally arrived in the Petermann Fjord (81o North) early this morning and wow what and incredible place! The Fjord is surrounded on both sides by huge, towering cliffs that shoot up vertically for the waters/ice edge and reach heights of just under 1000m. The immense scale is completely un-comprehendible until you get right underneath the cliff and look up at the cliffs soaring into the sky. The fjord itself is completely dominated by the Petermann Glacier which measures 60-70 km from where it floats off the bedrock at the head of the fjord to the ice front/terminus. Unlike many other glaciers in Greenland which do not float and therefore lose the majority of their mass via calving, the Petermann Glacier loses 90% of it mass from melting as it thins from 600m at the fjord head to 50m at the ice front over a period of 50 years (the ice advances at a rate of 1200m per year).
There were three main aims of the day. These were to firstly tow a CTD along the ice front to locate and measure melt-water freshened outflows from beneath the glacier, secondly to retrieve data from times lapse cameras set up on the cliffs above the glacier by Jason Box (Ohio State University) operating from the Greenpeace ship Arctic Sunrise and finally to take a full CTD section along the ice front.
I was very fortunate to be involved with towing the CTD along the entire length of the ice front and what a fantastic experience it was. To be so close to a glacier in the Larsen’s relatively small RIB must be a once in a lifetime experience. The team involved was myself, Helen and two of the crew called Shannon and Izzy, and we were on the water from 10.30 till 3.30. One of the CTDs had been modified and attached to a homemade fin making it look somewhat like an elongated fish. Unfortunately to make it fly level in the water we also had to attach an immense amount of weight on the front which made moving it up and down the water column a serious undertaking. It was always a sure fire method to warm you up though if you were a little cold! We settled with towing the CTD at around 1.5 – 2m below the surface and had to keep the RIBs speed pretty slow as we weaved our way in between the chunks of floating ice. The results we collected were somewhat varied. At the very beginning of the tow we noticed the ice was moving at a significant pace right where the glacier meets the base of the cliffs indicating an outflow, and here the salinities were particularly low representing a freshwater outflow. This early success got our hopes up. Unfortunately the rest of the tow did not produce such good results. We didn’t really locate any other significant fresh water outflows with the salinity only varying by one or two. In fact at one point the salinity was so constant we thought the CTD my have broken.
The job of flying in the helicopter up to the cliff tops to replace the cards in the time lapse cameras was given to Dave and Ron. The cameras are designed to photograph the possible imminent calving of a large (7 by 5.5km or larger) tabular berg from the ice shelf. The cameras themselves were located pretty close to the edge of the 900m drop so Dave and Ron had to be pretty careful working up there. The pictures they got up there were fantastic even if some of the positions they took them from must have been pretty hairy. They took quite a few aerial photos of the boat which looks the size of a toy compared to the massive ice floes dotted all over the surface.
The CTD section was completed throughout the afternoon with the deepest cast reaching down to just over 1000m. I’m glad I wasn’t operating the winch for that one! I will be processing the data in the next couple of days and it will be interesting to see what it shows.
After the long days work for most people, the evening was spent relaxing in the officer’s lounge. We had even decided that normal ice was not good enough so instead had chipped a small amount off the glacier itself to drink with our Screech (Newfoundland rum) and coke. What a way for ice that is thousands of years old to melt!

No comments:

Post a Comment