Friday, October 17, 2003

Jonna here:

Hi everyone. I hope everything is great is your neck of the woods! Well, I can report that I am feeling a lot more chipper because my knee is on the mend. It has not been very fun being the cripple in the group. You may have noticed that I have been absent from the diving and outdoor work and I can tell you that sitting in the lab icing my knee while everyone else goes diving is no fun--I am counting the hours until I can get in the water and start contributing to the dive work our group is doing. It turns out that when I slipped and fell at Happy Camper School I pulled my medial collateral ligament pretty badly and damaged the cartilage in my knee joint. I have to go to the medical clinic again on Monday but I am expecting to get clearance to dive that day. My knee feels a lot better!

I attended Sea Ice Training class today --the same class that Jim, Jennifer, and Craig attended on Monday, Oct. 13. Jennifer wrote about their experiences and I will try and complement her journal entry. My Field Safety Training instructor was Matt Szundy, an expert mountaineering guide when he is not working for FSTP.

We started out the morning in the classroom learning about the factors that contribute to sea ice break-up, the types of sea ice cracks, and how to profile them. Of course it is very important for our group to be trained and knowledgeable about assessing sea ice conditions because we are out on the sea ice almost every day doing our work.

Matt covered the environmental, geographical and mechanical factors that play a role in sea ice break-up. The environmental factors include temperature, sunlight, tides, currents, swells, snow cover (snow insulates the ice and can extend the amount of time it takes for sea ice to break-up), melt ponds, and seals (yes, seals).

	Here's a seal in its typical slug-like terrestrial pose.

I was surprised that Matt had seals on the list. It turns out that seals spend a lot of time chewing on the ice to make air holes; in fact they can spend up to 5 hours a day chewing away. I am not sure what the McMurdo Sound Weddell Seal population count is (I will find out and tell you later) but there are a great number of them. Another thing the seals do is poop a lot on top of the ice. Their poop is dark and it heats up from sunlight and that causes the ice to melt--amazing, eh?

The geographical factors involved in sea ice break-up include seismic activity, ice bergs, glaciers, shoals, peninsulas, coast lines, and debris. Scientists in the Northern Hemisphere have actually detected the seismic activity caused by the C17 ice berg banging against the sea ice and Ross Island. C17 is at the entrance to McMurdo Sound. I think that is incredible. One of the many things we did during the day was drive out to the place where the Erebus Ice Tongue meets the sea ice. The Erebus Ice Tongue is the front edge of the Erebus Glacier. It is causing the sea-ice a long distance in front of it to crack.

	Digging out the crack caused by the Erebus Glacier. Mt. Erebus in the background.

Glaciologists have found that the sea ice is preventing the forward movement of the glacier and there is a lot of pressure building up. When the sea ice breaks-up, which is predicted to happen sometime this season (it has not broken up for the past three years), it is thought that the Erebus Ice Tongue will move forward a quarter mile with incredible force. This may occur instantly or over several weeks. We dug out one of the cracks caused by the glacier and found that is was a classic example of an active sea ice crack (I will get to the different types of ice cracks in a minute).

Lastly Matt covered the mechanical causes of sea ice break-up. These include ice-breaker ships, vehicles, and planes. I found it interesting to learn that the planes that land on the sea ice (the C-17s, C-141s and the C-130s) are constrained by a 10% deflection limit such that when they sit on the ice they can only cause it to subside 10% of its overall depth. For example, if the sea ice is two meters deep (200cm), the plane is allowed to sink 20cm or less. If it causes the ice to sink lower, that model of plane is no longer allowed to land on the sea ice runway. Later in the season as the sea ice thins, the runway is moved to Willy Field which is located on the permanent Ross Ice Shelf which is about 250 meters thick!

Matt then went on to talk about the types of sea ice cracks that develop and how to profile them. There are tidal cracks, pressure cracks, straight edge cracks, and working or active cracks. Active cracks are the ones we are most concerned with although we watch for the others as well. The reason we profile cracks is to assess the safety of crossing them. This is a VERY important thing to do and there are several measurements that must be made. Profiling is done by drilling holes across the width of the crack. We measure the distance the drill penetrates the ice before hitting the sea water several times as we transect the crack. The main thing we are concerned about is that the effective width, that is the width where the sea ice is less than 30 inches, is less than a third the length of the vehicle track. For instance, the Piston Bully we drive has a track length of 108 inches. So we cannot safely cross a crack that has an effective width of 36 inches or less.

From the classroom we headed out onto the sea ice to put into practice what we had just learned. Like Jim, Jennifer, and Craig had done on Monday, we went out to the Sea Ice Training hut where we learned how to erect tents on the sea ice and start stoves. We should all be prepared for surviving what the Antarctic has to throw at us after Happy Camper School and Sea Ice Training. I thought that the v-anchors we learned to make for lashing down the tent was really cool. And I think I have the trucker's hitch, a very useful knot, wired. After lunch we headed out to look for cracks. Word had filtered back to FSTP that the hut our group had set up for diving out at Cinder Cones was surrounded by cracks. I was there when we drilled our dive holes so I told Matt that yes, there were lots of cracks to profile at our dive hut.

	Castle rock (left), Cinder Cones (right) and our dive hut-#8.

While the weather was certainly not Condition 1 like it had been on Monday, the wind was howling out at Cinder Cones. We were all completed bundled up as we drilled eight holes by hand across a big crack in the sea ice (it goes much faster with an Echo drill). We found that where the ice was the thinnest it was well above the required 30 inches (76cm)--in fact it was over 170cm (nearly 2 yards). So this was clearly a safe crack to cross over.

	Using the hand drill to profile a crack at Cinder Cones.

From Cinder Cones we headed out to the Erebus Ice Tongue where we looked at another crack about a half mile in front of the ice tongue (I described this above). After that we headed home to McMurdo. Because of my bad knee I got to ride in the front of the Haglunnds the whole day and was treated to fantastic views all around McMurdo Sound (I guess there are some perks to being injured). This place really is stunningly beautiful. So now I too have completed all the training requirements and will soon be diving with our group. Sea Ice Training and Happy Camper School were really valuable courses.

In the meantime...

While Jonna was off being a Happy SeaIce Trainee (she was probably happier than we had been, since she didn't have a blizzard with which to contend) the rest of us were doing other important stuff. We've established a bit of a rhythm by now that goes something like this: dive, sieve, dive, sieve, dive, sieve. Stacy did another hard-hat sewer dive (she particularly likes the broccoli, but we won't go into that here...) with Rob the Super Dive Boy. Then Jen and Dan did a dive in front of town, with Jen doing clam counts and video transects, and Dan taking sediment samples for TOC, grainsize analysis, and heavy metal analysis, along with 6 replicate cores for benthic infaunal community analysis (hence the sieving alluded to earlier). They also both collected a few specimens for bioaccumulation analysis. After lunch and a bout of sieving, Craig and I did a dive similar to Dan and Jens. Our assignment was the dreaded Cursed Hole, the station which had required numerous dives to complete last year. Although the curse tried to exert itself, we perservered, and got everything done. We all ate a well-earned hearty dinner (we eat a lot), and dispersed to our rooms, our computers, or in the case of Jen and Craig, to do a trial deployment of the CTD that Craig had managed to decipher.