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| Titel |
Climatic and chemical drivers of trends in DOC in northern surface waters in
Europa and North America |
| VerfasserIn |
Heleen A. de Wit, Don T. Monteith, John L. Stoddard |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250135955
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| Publikation (Nr.) |
 EGU/EGU2016-16886.pdf |
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| Zusammenfassung |
| Concentrations of DOC in boreal surface waters have increased to levels that create
challenges for water treatment plants, and that potentially impact lake habitat through
increased anoxia and thermal mixing, and productivity. Aquatic transport of DOC from
land to oceans is likely to increase, even if runoff patterns would remain stable.
Reduced acid deposition appears to be a dominant driver behind the increase in DOC
concentrations, through increasing organic matter solubility. We hypothesize that
the higher solubility of organic matter makes DOC more susceptible to climate
change.
Here, we present trends in DOC from circa 500 lakes and streams in subarctic,
boreal and temperate headwater catchments in Europe (UK, Fennoscandia, Czech
Republic, Slovakia) and North America (Northeastern US, Ontario, Atlantic Canada)
from 1990 until 2012; an extension of the trend analysis presented in Monteith
et al. (2007). The water chemical data stem from national monitoring networks,
assembled by the ICP Waters network. Sampling frequencies vary from 1 to 52
samples per year. Climate data were obtained from Climate Research Unit in the UK.
Trends were calculated using the Mann-Kendall test and the Sen-slope estimator.
We test 1) if DOC responds to changes in the rate of decline in acid deposition,
and 2) if trends in temperature and precipitation affect trends and variability in
DOC.
Positive trends dominate: the median (±2.5% quartile) of the absolute and relative DOC
trends is +0.06 (+0.36 to -0.02) mg C L−1 yr−1 and +1.4 (+4.7 to -0.9) % yr−1, respectively.
Overall, the trends do not level off when comparing 1990-2004, and 1998-2012, except in the
UK and Atlantic Canada. These two regions are strongly impacted by seasalt deposition but
may also experience stronger warming than elsewhere. The response of DOC to changes in
SO4 (expressed as trend ratios) is stronger in 1998-2012 than in 1990-2004. We will explore
whether this changing relates to increasing dominance of drivers, such as temperature or
precipitation, and will present multivariate models of DOC trends in relation to climate and
deposition.
References
Monteith DT, Stoddard JL, Evans CD, de Wit HA, Forsius M, Hogasen T, Wilander A,
Skjelkvale BL, Jeffries DS, Vuorenmaa J, Keller B, Kopacek J, Vesely J (2007) Dissolved
organic carbon trends resulting from changes in atmospheric deposition chemistry. Nature
450(7169): 537-540 |
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