Our post. doc Anna Silyakova spent six weeks frozen into an ice floe in the Arctic Ocean on board the research vessel Lance. In this blog post you can read more about the experiments she conducted in the ice.
Text: Daiki Nomura ( Hokkaido University) and Anna Silyakova (CAGE). Blog was previously published by Norwegian Polar Institute.
We are on the N-ICE2015 cruise to study the chemistry of greenhouse gases in seawater, sea ice, and the atmosphere. We are particularly interested in vertical fluxes through sea ice and snow, of such important greenhouse gases as carbon dioxide (CO2), methane (CH4) and bromoform (CHBr3).
One of our primary tasks is to collect samples of seawater from the twice-weekly CTD casts. These water samples will later be analyzed back home for concentration of dissolved gases, which will provide information on how carbon dioxide, methane, and bromoform are distributed in the water column under sea ice, down to a depth of 1000 metres.
Collecting ice cores and brine
We also collect ice cores from different places around the ice floe, which varies in thickness from 40 cm to 3.6 meters. The cores are cut into 10 cm sections, melted at room temperature over a couple of days, and then the melted water is collected for analysis (see picture). After analyses are done, we get the vertical distribution of gasses throughout sea ice. Samples are also taken from melted snow and slush on top of the sea ice to see how the concentrations of these differ from the sea ice.
In addition, we collect brine, which is a highly concentrated solution of many chemical elements including the dissolved gases which we are interested in. The salinity of the brine on our ice floe is more than 100 psu—much higher than the concentration of seawater, which is 35 psu.
Atmospheric measurements
In the atmosphere, we are measuring carbon dioxide and methane fluxes (from/to snow and sea ice surface) using two different techniques. One technique is called eddy covariance. This method gives the flux from an area of 500 meters around the eddy covariance mast, where the gas analyzers are mounted.
The other technique involves so-called flux chambers. Flux chambers look like big casserole dishes that are flipped over and put on top of ice and snow. If there is outgassing from the ice surface, gases (i.e. methane, carbon dioxide or bromoform) will accumulate under the chamber over time. The gas fluxes are determined by sampling the gas under the chamber every 10 minutes for a total of 30 minutes in order to detect changes in concentration over time.
For all of this work, we must carry a small chemistry laboratory with us to each sampling site. Our laboratory fits into several boxes and includes different sorts of flasks, bottles, syringes, tubes, chemicals, pipettes, and of course; laboratory sterile gloves.
