Gas properties of winter lake ice in Northern Sweden: implication for carbon gas release

[摘要] This paper describes gas composition, total gas content and bubblescharacteristics in winter lake ice for four adjacent lakes in adiscontinuous permafrost area. Our gas mixing ratios for O₂, N₂,CO₂, and CH₄ suggest that gas exchange occurs betweenthe bubbles and the water before entrapment in the ice. Comparison betweenlakes enabled us to identify 2 major "bubbling events" shown to be relatedto a regional drop of atmospheric pressure. Further comparison demonstratesthat winter lake gas content is strongly dependent on hydrologicalconnections: according to their closed/open status with regards to waterexchange, lakes build up more or less greenhouse gases (GHG) in their waterand ice cover during the winter, and release it during spring melt. Thesediscrepancies between lakes need to be taken into account when establishinga budget for permafrost regions. Our analysis allows us to present a newclassification of bubbles, according to their gas properties. Our methaneemission budgets (from 6.52 10⁻⁵ to 12.7 mg CH₄ m⁻² d⁻¹at 4 different lakes) for the three months of winterice cover is complementary to other budget estimates, as our approachencompasses inter- and intra-lake variability.

Most available studies on boreal lakes have focused on quantifying GHGemissions from sediment by means of various systems collecting gases at thelake surface, and this mainly during the summer "open water" period. Onlyfew of these have looked at the gas enclosed in the winter ice-cover itself.Our approach enables us to integrate, for the first time, the history ofwinter gas emission for this type of lakes.

[学科分类] 地球化学与岩石