Not many people in the world work on sea ice. There is a reason why. Sea ice forms when the sea temperature is -1.8 0C, the air temperature must be below -5 0C and when it first forms the wind must be <5 knots. Over time with these perfect conditions the sea ice gets thicker and thicker.
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| Looking from the Ramp at Rothera with the sea ice in North Cove (Left of the photo) |
Before we are allowed to work on the sea ice we go out with the field guides and test it. Before we go on the sea ice, we check the past three days of weather conditions and if it's going to be stable for the length of time the sea ice party is out there. When you get to the edge of the ice we call opps to let them know our intentions. We then use a bog chisel to check the ice is fully fasted to the land, tide cracks form around the edges and out into the bay made by the movement of the tide, we hit this tidal crack with a bog chisel to test it.
WE then test the thickness of the ice out from the tidal crack and past the areas that we need to work. It must be >20 cm for us to walk on and >40 cm for us to skidoo on. So on the first time we go out we do everything on skis.
First you removed the snow.
Then you drill through the sea ice with a hand drill. We then use a handmade measuring tool that has a little arm that you hold vertical to the pole when you drop it through the hole, then once you've got through the thickest part you release the arm and measure the depth of the ice.
Once the weather conditions are perfect and the drilling had been complete. WE then get the go ahead to work on the sea ice from the feild guides, our station leader and people in Cambridge.
WE tested the ice in south cove and north cove this week, it's >40 cm in Hangar cove but <25cm in south cove. So we conducted a CTD at site 3 which is our closest sampling site to base.
We manhauled a nansen sledge to which we had attached the CTD winch from our boat Stella. This was really fun, but hard work over the brash ice that had formed the fast ice.
WE walked through an ice rose garden...
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| Bradders using an axe to cut a small hole to fit the CTD through. |
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| I'm using a bog chisel to sort out the sides of the hole |
WE then sent the CTD to 100 m to get a temperature, salinity and fluorescence profile.
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| Controlling the rate at which the CTD drops so that we get a good profile. |
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| Beautiful scenery. |
Sampling complete with the help of Bradders and Kate! A tropical -18 air temperature that day, as you can see by our frozen hair, beards and eye lashes!
The other work that we've been doing regullary is assisting Emily with her Dutch projects. She completes ice cores in both South cove and Hangar cove weekly.
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| Using a zarge box to get more pressure to make the first cut. |
Emily loving it!
55 cm thick this ice core was!! Going to get more and more difficult as it freezing from beneath!
One of the most exciting things we do here is that Kate, Ben and I dive through the ice in both Hangar cove and south cove! But first we need to cut the dive hole which is an epic mission! The ice was finally stable enough at the same time that the weather was good enough for us to drag a chainsaw out into Hangar cove.
Adam our boaty is currently out of work with an injured ankle so Kate took the very willingly liberty of cutting the first dive hole. She was so excited. I think it was because she was the one holding the chainsaw whilst the boys had to watch as she was the only trained personnel on the ice! Very awesome.
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| First she did a small cut to get the rough shape. |
After cutting a rough shape we attached ice screws into each block.
Kate then used a systematic way around the blocks to cut them individually. We then attached a piece of rope to the ice screw to pull out the blocks. The main thing about this job is keeping the chainsaw warm, it had been run for 30 minutes before it was brought out onto the ice. We were then fast at putting in the screws and then pulling out the blocks so she could continue cutting!
What a pro!
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| Check out how thick that is! |
Nice one Kate...now the fun bit....we got to dive through it!
We cover the holes with boards to try and insulate it slightly from the air temperature to decrease the freezing time, but with it freezing from underneath it is still going to freeze up quickly. So now our job every day that we can get out onto the ice is to bash out the dive holes so it does not get thicker than a bog chisel being able to go through it!
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| Marked by flags. The main dive hole and then the emergency dive hole closer into the shore. |
Emily doing an epic job of bashing out the dive hole!
The first time we dived through the hole was last week. It was actually pretty scary because as you can see from the photo above it looks pitch black. Our only worry is that a big leopard seal had been hanging out a few weeks previous to us cutting the hole, but with the sea ice formed way past the islands and down to the south and north we were fairly confident that all seals had followed the ice edge away from Rothera. Kate jumped in first and did a quick seal check, we then descended into the darkest depths to complete the monthly collections. It was an awesome first through the sea ice dive!
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My head on the ice ceiling.
The most terrifying thing about sea ice and the reason why we have strict weather conditions is that for the past few days the wind increased to 25 knots gusting 50 kts and the air temperature has rises to 1.5 degrees C....as you can see from the photo below the sea ice that we had been working on in south cove just a few days before to complete a CTD has now fully blown out and is all open water! Very changeable conditions but very manageable and perfectly safe when the conditions are right, but now you can see why we drill before we work!
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