The Evolution of CO2 Emissions and Heat Flow Through Soil Since 2004, in the Utilized Reykjanes Geothermal Area, SW Iceland

Abstract

We present a study on the evolution of CO2 flux and heat flow through soil in the Reykjanes geothermal field, SV-Iceland, based on annual measurements carried out since 2004. The heat flow and CO2 flux was annually mapped by measuring the soil temperature at 15 cm depth and CO2 emission through soil based on a closed chamber method on a grid with 25 x 25 m spacing. The total heat flow and CO2 flux calculated for each year, using the sGs algorithm, show that heat flow has doubled from 2004 to present and the CO2 flux has almost tripled during this period. Surface activity has increased significantly and the anomalies have grown. The changes in surface activity and soil flux are most likely caused by the commissioning of the 100 MWe Reykjanes Geothermal Power Plant in the area in 2006. The production involves withdrawal of large volumes of geothermal fluid which causes pressure lowering in the system. One of the consequences of the pressure lowering is a formation or increase of a boiling zone in the upper part of the system which can result in more pathways for steam towards the surface, hence enhancing heat flow and CO2 emission.