Sea Ice Training
It was a beautiful day today! It warmed up to -9°F (-23°C), and -26°F (-32°C) with the wind chill. That meant we could complete our Sea Ice Training. Five of us, from 3 different science groups, dressed in our ECW (Extreme Cold Weather gear) and piled into a Pisten Bully with our trainer, Ben. A Pisten Bully is a large track vehicle (pictured in the photo below), and it’s very stable and good to bring out on the sea ice before the ice roads are completed. First order of business was to learn to visually identify cracks in the sea ice and then how to profile them. Because of land, currents, and wind dynamics, there are certain areas of the sea ice where cracks form every year, and those perennial cracks have been named by the people here at McMurdo.
We first headed out to Backhoe Crack, an active crack that is keeping the Field Safety & Training (FS&T) staff on their toes. We went to the nearest marked vehicle crossing to profile the crack. We measured the crack at the measuring station – a series of four flags that will move as the crack expands or contracts – and noted that it had widened by several centimeters since the last measurement. While we were visually inspecting the crack, we heard a distinctive chuff – a Weddell seal was breathing in a hole beneath the snow, right there near the crossing! This was a good indication that we should move the vehicle crossing to a different part of the crack. So we moved over and began the process of profiling the crack again. First, we cleared away the snow until we knew we were at the surface of the sea ice. Then we drilled down into the center of the crack and into the slightly higher areas on either side. We measured the sea ice thickness with a special measuring tape. This was a healthy reminder that we were standing on ice that covers open ocean! Everyone took a turn drilling and measuring, and we learned how to determine which vehicles (Pisten Bullies, snowmobiles, and Challengers) could safely cross the crack at this spot. Based on our measurements, we determined this spot was a safe new crossing.
From there, we moved on to Big John Crack, which had closed up and formed a sizeable pressure ridge. The sea ice was more than a meter thick everywhere we measured at this crack. But sea ice moves and changes constantly throughout the season, so FS&T will keep monitoring the crack on a regular basis.
The final skill we practiced was making a “v-thread.” If there is not enough snow to make a snow anchor, this is a way to use the sea ice to anchor things like a tent or portable shelter. We used a small ice screw to form a v-shaped funnel in the ice. Then we threaded a small rope into the V, which could be used to tie something down to the sea ice. It’s quite strong and very useful for when the wind picks up while you’re working!
With a successful Sea Ice Training behind us, we are now preparing our equipment for when the sea ice roads are complete and officially “open for travel.” Then we will begin scouting for our mama seals and determining specific locations we plan to work this season.
Written by: Heather Liwanag