The physical and biological controls on the distribution of gases and solutes in sea ice from ice growth to ice decay

• Main Author: Zhou, Jiayun
• Other Authors: Delille, Bruno, Tison, Jean-Louis, Chou, Lei, Vancoppenolle, Martin, Thomas, David, Heinesch, Bernard
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universite Libre de Bruxelles 2014
• Subjects: Sciences de la terre et du cosmos; Sciences exactes et naturelles; Biogeochemistry > Polar regions; Sea ice > Polar regions; Gas dynamics; Biogéochimie > Régions polaires; Glace de mer > Régions polaires; Gaz; Dynamique des; nitrogen; dissolved organic carbon; methane; argon; oxygen; brine dynamics; inorganic macronutrients; Barrow; Sea ice; Alaska
• Online Access: http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209219; https://dipot.ulb.ac.be/dspace/bitstream/2013/209219/1/6fa4f03e-b5ff-447c-8374-bb572663e823.txt; https://dipot.ulb.ac.be/dspace/bitstream/2013/209219/4/3b74519f-a4a9-46c0-9907-38506be91af0.txt

The ongoing changes in the extent and the properties of sea ice, associated with the warming climate, are affecting the polar ecosystem and the interactions between the atmosphere, sea ice and the underlying waters. How sea ice biogeochemistry will change in the foreseeable future is currently uncertain, but is a crucial problem to tackle. To better understand how sea ice biogeochemistry could change, we investigated the factors regulating the distribution of some dissolved compounds (e.g. nutrients, dissolved organic matter (DOM)) and gaseous compounds (e.g. Ar, O2, N2, CH4) in sea ice, from ice growth to ice decay. The results were obtained from a 19-day indoor experiment in Hamburg (Germany) and a five-month-long field survey in Barrow (Alaska). They were then compared to the physical properties of the ice (temperature, salinity, and other derived parameters such as brine volume fraction) and different biological parameters (bacterial activity, bacterial abundance, chlorophyll-a and phaeopigments). Our work indicates that the physical properties of sea ice exert a strong influence on the distribution of the biogeochemical compounds in the ice, through their impact on brine dynamics, gas bubble formation and ice permeability. We have described 4 stages of brine dynamics, which affect the distribution of the dissolved compounds (e.g. silicate and DOM) in sea ice. However, inert gas (Ar) shows a different dynamic in comparison to the dissolved compounds, indicating a different transport pathway. We suggest that the formation of gas bubbles in sea ice is responsible for that different transport pathway, because gas bubbles should move upward owing to their buoyancy in comparison to brine, while dissolved compounds are drained downward due to gravity. Our observations further indicate that the critical permeability threshold for the upward gas bubble transport should range between 7.5 and 10 % of brine volume fraction, which is higher than the 5 % suggested for the downward brine transport. Increasing ice ...