Blog from RV Lance: Measuring, coring, drilling, dug snow pits and a whole lot of other things on the sea ice.
After a week at sea we have been already walking on water many times, at times with more than 2000 m of water below our feet, we have been measuring, coring, drilling, dug snow pits and a whole lot of other things on the sea ice covering the Arctic Ocean north of Svalbard.
The daily routine seems to consist of work interrupted by some sleep and the delicious meals prepared by the kitchen staff on Lance. 24 hours of daylight makes it possible for us to work around the clock, and basically forget the normal daily cycle we are so used to on land. The sea ice team has been pushing 12+ hour days out on the ice irrespective of the weather.
One of the workpackages in ICE Fluxes during the Lance cruise is to investigate the flux of CO2 between the atmosphere and sea ice. We use chambers that have automatically closing lids that can measure the change of CO2 concentration in the air above sea ice or snow. When one chamber is closed, air in the chamber is circulated continuously through an infrared sensor that can measure the concentration of CO2 in the air, and by measuring the change of CO2 concentration with time, will tell us about whether sea ice is a source or sink of CO2. Using three alternating chambers, we can place these on different surface types. The emission or withdrawal of CO2 from/into sea ice is a complex function of the physical state and chemistry of the ice.
On ice station we need to locate ourselves upwind of the ship, and any possible other source of CO2 (ship’s exhaust) to make reliable measurements. A difficult task since we are on a drifting ice floe that can rotate, and winds tend to change direction with time. When we have found a suitable spot on the ice floe, after discussing with the other groups working on the floe, we set some chambers on snow surface, or dig down to the surface of the ice. This way we look at diverse surface types. By measuring the change in CO2 in closed chambers we can estimate whether sea ice emits CO2 to the atmosphere or draws down CO2 from the atmosphere.
We also sample sea ice for alkalinity and inorganic carbon, to understand how the chemistry of the sea ice affects the measured CO2 fluxes. We are especially interested in the brine, a salty solution that forms channels and pockets when sea ice forms. The rest of the sea ice basically (pure water) ice, and all the chemical reactions in sea ice do in fact occur in the brine. We also look for calcium carbonate crystals (CaCO3) that can precipitate in the brine at the low temperatures in the ice. Only recently there has been evidence that actually CaCO3 forms in sea ice and we will be among the first to observe these in Arctic sea ice if we find any. When carbonate rich sea ice melts, it may contribute to a local atmospheric CO2 sink in regions where ice melts, especially in the Nordic Seas.