CO2 evasion and carbon budget of Lake Torneträsk, a large, subarctic lake in northern Sweden (BSc Thesis)

 ABSTRACT

Freshwater systems play an important role in the carbon cycle, but there are still large uncertainties, which must be solved in order to make climate change predictions more accurate. This study quantifies the annual flux of CO2 in lake Torneträsk, a large (345 km2) subarctic lake in northern Sweden, an area of a special interest as global warming is expected to be more severe in polar regions. Torneträsk catchment has been very well studied for decades, but until now not a single study focused on the main component of the landscape, lake Torneträsk. The results of this study are relevant in the carbon budget of the region, as the CO2 evasion from lake Torneträsk to the atmosphere is higher than previously considered. Due to its large surface, the amount of carbon released comprises 25% of the total amount of carbon (C) emitted from all lakes in the catchment (3 231 lakes). Temporal high resolution measurements of CO2 in lake surface water also show interesting daily and seasonal patterns, possibly related to water temperature and photosynthetic activity.

Furthermore, I elaborate a first attempt of the lake carbon budget, the evasion of CO2 to the atmosphere comprises 16% of C entered from the catchment. The amount of C buried in the sediment is around 14%, and the rest flows downstream, 50% as dissolved inorganic carbon (DIC) and 20% as dissolved organic carbon (DOC).

Torneträsk catchment is a unique environment in order to understand the biogeochemical cycles at a landscape scale, due to its large amount of studies carried out and its situation in a sensible area as the subarctic region. This study contributes unveiling the role of the most important lake in the region, in order to develop an accurate carbon budget for the whole catchment.