I don’t think I’ve talked much yet about my own personal corner of our project. This is actually a bit of science I tacked on at the last minute—it wasn’t in the original grant—and I’m hard pressed now to recall quite how I even came up with it.
You may recall that the effect we’re looking for in the sea ice depends on the formation of hydrohalite crystals inside brine pockets. Rich has actually got a nifty microscope setup in our cold room to look at the brine pockets now (pictures of which will be posted here as soon as I can pilfer them from his collection.)
Rich's tablet displays a highly magnified (and perhaps thoroughly educated) view of some brine pockets.
The brine pockets, as I explained earlier, are there because seawater got trapped in the ice when it was in the process of freezing. However, as you are well aware, seawater isn’t just a collection of water and salts. It is also home to a staggering number of microorganisms, some of which are inevitably trapped in the ice with the seawater as it freezes.
The brine pockets don’t provide a particularly hospitable environment for things to live. As the ice gets colder, the brine pockets also get colder, as well as smaller and saltier. Sharp pointy ice crystals may form. Some of the creatures that get caught up in these brine pockets try to protect themselves from freezing by secreting things that reduce the melting point of water, keeping it liquid at lower temperatures. One of these is a slimey substance called EPS (which stands for “expolymeric substance” or “exopolysaccharide”, but I usually just think of it as “slime.”)
Now, this substance obviously has the potential to mess up our nice simple salt-water physics. Changing the behavior of the water and salt in the brine pocket is exactly what the diatom wants it to do, after all. When our colleague Bonnie Light observed natural sea ice in the lab, she found that not all hydrohalite precipitated at the expected temperature—some brine pockets developed hydrohalite crystals earlier than others (Light, Maykut and Grenfell, 2003.) The difference could, perhaps, be due to EPS content of some brine pockets. So while Steve and Rich are investigated albedos, I’m collecting ice to see how much EPS it might contain.
The process starts when I take an ice core:
You remember this bit.
We strap it to the top of the pisten bully and take it back to the cold lab, where Steve and I cut it into manageable bits.
Even with a couple of layers of gloves, my hands get awfully cold doing this. Presumably my squid hat is also getting pretty chilly, but it remains stoic.
If there are any organisms in the sample—algae or bacteria—I don’t want to shock them too much by exposing them to very different temperatures or salinities. If I shock them, they might explode (or ‘lyse’ in biologist-speak.) When I’m starting out the critters are in brine pockets that started out between -15C and -30C, depending on what day we took the core and what depth they were at. The brine pockets they’re in are very salty at that temperature, so I mix up some very salty artificial brine and dump the samples into that to melt.
Once the samples are melted, I filter them.
The filters are rather delicate and finicky.
This is very similar to a setup that Steve carted around Siberia for two months for snow research. Note handpowered vacuum pump.
There are a couple of common ways to look at EPS. One of them uses the filters plain; for the other, you dye them with something called Alcian blue that binds to the EPS:
Blue. Like a glacier! Well, sort of.
Eventually, you end up with something like this, which I’ll put back in the freezer until it can make it onto a cargo flight back to the States.
All that work for something that fits in a 1.5mL tube with room to spare.