Abstract ID
climch14
Type
Oral
Theme
climch
Full title
Increased organic carbon runoff in Estonian rivers in 1992-2007 as affected by changes in drought regime
Abstract text
The soil contains a third of the world’s terrestrial carbon. More than 20% of it is stored in the northern
peatlands. Global warming has started to destabilize these sinks, gradually turning them into sources. In Estonia,
there are 10,091 km<sup2</sup> of peatlands, constituting 22.3% of the total area of the country. The aim of the
current study was to explain the dynamics of the total organic carbon (TOC) in the Estonian streams for the
15-year period 1992-2007. The national environmental monitoring programme initiated the measurements of
TOC in streams in 1998. Therefore, we reconstructed the earlier concentrations of TOC by correlating this with
the permanganate oxygen consumed (POC). TOC data of 64 weirs were studied. In Northwestern Estonia, a
weak rising trend of TOC concentrations was observed. The trend accords with earlier data from northern
catchments, demonstrating a possible positive feedback in the global carbon cycle. One of the reasons for this
trend is a deepening hydrologic drought (decreasing average water runoff from April to September) during the
last decade. Additionally, there has been an increase in the number of drought days recorded during the last 50
years in Estonia. Due to changing enzymatic activity, severe droughts initiate an increased flux of dissolved
carbon. We found a further weak positive correlation (R²=0.28) between the ratio of average
summer-runoff values in 1992-1999, 2000- and 2007, and difference between average TOC concentrations from
the same periods. Thus, a change in the pulsing regime of rivers enhances carbon losses from catchments with a
high percentage of peatlands.
Submission date
2009-10-22
Keywords
Catchments; Hydrologic drought, Peatlands; Runoff, Total organic carbon
Will be submitting paper?
Yes