Finding the Brine
Dec 9, 2008
At this point I’ve adjusted to life going from one ice station to the next- it’s pretty hectic getting all our equipment out onto the next station of floating sea ice at around 9am every morning, drilling ice cores in 2 shifts led by my lab mate until around 4pm, then trying to store and process samples for the rest of the night, but at least now I know what to expect and what to do. We’re on our sixth station so far and I’m about halfway through my first set of bottle experiments, which will take about 3 days each to process. The latest word onboard is that we’ll have our last station on Dec 28th and then it’ll take about 13 days to cross the Amundsen sea to McMurdo base, so I’m trying to get as much done before then as possible.
What do I do on the ice? I am trying to collect samples of ice core from the floating sea ice, brine within the sea ice, and seawater under the ice to measure the concentration of halocarbons (chemicals with carbon and at least one halogen atom), which can be destructive to the ozone layer and are produced both biogenically (by organisms) and anthropogenically (by people and machines). As you saw in the last post, we use ice augers (drills) to take cores of sea ice, and once we’re done we can also collect seawater from underneath the ice, but brine is the tricky part. Brine are the pockets of super-salty seawater that get trapped within the sea ice, because as liquid water freezes and becomes ice, it pushes all of the impurities, including salt, away and freezes as ‘pure’ water. This happens because pure water has a higher freezing temperature (0C) than salt water. This creates a series of extra-salty ‘pockets’ of salt water within the sea ice that stay in liquid form because of all of the impurities and compounds in them. Extracting brine can be tough because we never know where the ‘pockets’ will be, and if the ice is mushy there often aren’t well-defined pockets because the brine gets pushed out of the ice altogether, so we have to hope for fairly solid layers of ice that have frozen quickly to trap the brine. These conditions don’t exist at every ‘station’ of sea ice our ship stops near, however, so I just have to hope that we are able to find it often enough that I can collect enough brine to analyze the halogens (that make up salts) inside.
Here is a very simple video I created to explain the process-