Tiny Trace Gases in Arctic Sea Ice

Quelle: blogs.helmholtz.de/polarstern/en/ 27 May 2015
by Meri Korhonen, Shannon McPhee and Kirstin Werner
Valérie Gros and Roland Sarda-Esteve from the Laboratoire des Sciences du Climat et de l'Environnement (LSCE) in Paris have experience measuring trace gases in the ocean, but are new to working with sea ice. In addition to the gear they packed to work on ice floes, they brought their own air because they do not really trust the cool Arctic air. Their air is stored in gas bottles in front of their chemistry lab on deck E. From here, the air is transported through a very fine tube and mixed with seawater that is pumped from under the ship into the lab. “The air we are using to extract gases from the water is 100 percent clean. That means it does not contain any trace gases we aim to measure during our campaign on board RV Polarstern”, says Roland. Valérie and Roland are both interested in the very tiny amounts of carbon monoxide, dimethyl sulphide and various Volatile Organic Compounds (VOCs), which are found in seawater and sea ice. “The proportion of the gases we are measuring in the Arctic Ocean is very small. For example, the measurement of one Volatile Organic Compound in the ocean is equivalent to find just one inhabitant of India within the total population of one billion inhabitants“, explains Valérie. Even though the amount of these gases is very small, they are highly relevant to the atmospheric and climate system. While dimethyl sulphide provides nuclei for cloud condensation, other gases such as carbon monoxide and the VOCs take part in the formation of ozone in the atmosphere. „Our research is like a big puzzle. I am very excited to see how these small parts influence the whole picture of the Arctic climate“, Valérie adds. In addition, Roland is particularly interested in how the instruments set-up, a Proton Transfer Mass Spectrometer and a Gas chromatograph coupled to an Online Water Extraction Device, work aboard the RV Polarstern (for more information see here pdf). These instruments have been running since the RV Polarstern departed Bremerhaven in order to obtain continuous measurements on the journey from the North Sea to the Arctic. Both scientists are very excited to reach the first sea-ice station to start their sampling on ice.