| Summary: | The objective of this study was to summarize the available data on the surface activity in the Reykjanes geothermal area for the last eight years and reveal the changes which have taken placethere during this period and also to evaluate the methods which have been used. Annually since 2004, soil measurements werecarried outon soil temperature at 15 cm depth and CO2 emission through soil on a measurement grid with a 25 x 25 m grid spacing except in 2011 when two such datasets were made. Total heat flow, total CO2 flux and uncertainty was calculated for each year’s measurements and the distribution shown on maps. A thermal infrared image, obtained in May 2011 from Reykjanes, snowmelt tracks, done in March 2011 and results from temperature loggers which obtained data during four periods from May 2011 to April 2012 were also used. The soil measurements show that heat flow has increased from 17 ± 1.4 MW to 36.1 ± 2.5 MW and the CO2flux has increased from 13.5 ± 1.7 tons per year to 36.6 ± 3.9 tons per year and the area where surface activity is present has grown, especially to the south and southeast. These changes can mostly be traced to the geothermal power plant in the area even though changes of this order of magnitude are known to be able to take place in Reykjanes without any utilization. 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 the 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, increased heat flow and CO2 emission. The TIR image from 2011 was calibrated from few soil measurements which were carried outat the time of the flight. The image was compared to soil temperature measurements, snowmelt tracks and a similar TIR image obtained in 2004 from Reykjanes. The comparisonrevealed a weak relationship with the results of the soil temperature measurements but these two methods showed a similar ...
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