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The NORTH The NORTH - - WATCH program WATCH program We now have compelling evidence that climate change is affecting water resources in many parts of the world. In few places will the changes and challenges be greater than in the higher mid-latitudes of the northern hemisphere. In this circumpolar, transitional climatic zone, slight temperature differences determine the status of frozen ground, whether precipitation falls as rain or snow, and the degree to which winter snow packs accumulate and subsequently melt. Predicting the integrated consequences of climate change on the physical, chemical and biological characteristics of water resources is a difficult area of interdisciplinary environmental science. Fortunately, in many areas, research catchments have been established that provide the long-term data sets that encompass integrated measurement of the linkages between the climate, hydrology, biogeochemistry and ecology of river systems and how these are being affected by climatic change. North-Watch (http://www.abdn.ac.uk/northwatch/ ) is funded by the Leverhulme Trust, UK, and lead by Doerthe Tetzlaff at the Northern Rivers Institute, Univ. of Aberdeen, Scotland, UK. Background Background There has been an increasing interest in understanding the regulating mechanisms of surface water dissolved organic carbon (DOC) over the last decade. A majority of this recent work has been based on individual well characterized research catchments or on regional synoptic datasets combined with readily available landscape and climatic variables. However, as the production and transport of DOC is primarily a function of hydro-climatic conditions, a better description of catchment hydrological functioning across large geographic regions would be favorable for moving the mechanistic understanding forward. To do this we report from a first assessment of catchment DOC from the international inter-catchment comparison program North-Watch. Hydro-climatic controls of catchment DOC across northern catchments within the North-Watch program Hjalmar Laudon 1 , Doerthe Tetzlaff 2,3 , Sean Carey 4 , Chris Soulsby 2 , Jan Seibert 5 , Jim Buttle 6 , Jamie Shanley 7 , Jeff McDonnell 8 , Kevin McGuire 9 HJ Andrews, Pacific NW, US Krycklan, N Sweden Strontian, Scotland Wolf Creek, Canada Mharcaidh, Scotland Girnock, Scotland Affiliations Affiliations 1. Dept. Forest Ecology and Management, SLU, Sweden, [email protected] 2. Northern Rivers Institute, University of Aberdeen, Scotland, [email protected] ; [email protected] 3. IGB Berlin Leibnitz Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany 4. Dept. Geography and Environ. Studies, Carleton Univ. Canada; [email protected] 5. Dept. Geography University of Zurich – Irchel, Switzerland, [email protected] 6. Dept Geography, Trent University, Canada; [email protected] 7. U.S. Geological Survey, Montpelier, USA; [email protected] 8. Dept Forest Engineering, Oregon State Univ., USA; [email protected] 9. Virginia Polytechnic Institute & State Univ., USA; [email protected] Preliminary findings Preliminary findings • Hydroclimatic conditions have profound control on DOC on episodic, seasonal and inter-annual time scales across the northern catchments. •There is a strong seasonality in runoff and DOC export among all catchments but it becomes successively more dominated by export during the spring towards the sites in colder regions (Fig. 2&3). •There is decoupling between runoff and DOC export, with a generally lower relative export of DOC during winter and spring and higher relative export during late summer and fall (Fig. 3). • Winter temperature is a strong predictor of the proportion of annual DOC that is exported during spring and early summer (Fig. 4). Dry Wet Warm Cold Fig. 1. Catchments included in the North-Watch program Jan FebMar Apr May Jun Jul Aug Sep Oct NovDec Proportion of annual flux (%) 0 10 20 30 40 50 J F M A M J J A S O N D Jan FebMar Apr May Jun Jul Aug Sep Oct NovDec Proportion of annual flux (%) 0 5 10 15 20 25 30 35 J F M A M J J A S O N D Jan FebMar Apr May Jun Jul AugSep Oct NovDec Proportion of annual flux (%) 0 5 10 15 20 25 30 35 J F M A M J J A S O N D Runoff DOC Jan FebMar Apr May Jun Jul Aug Sep Oct NovDec Proportion of annual flux (%) 0 5 10 15 20 J F M A M J J A S O N D Jan FebMar Apr May Jun Jul AugSep Oct NovDec Proportion of annual flux (%) 0 5 10 15 20 25 30 35 J F M A M J J A S O N D Jan FebMar Apr May Jun Jul AugSep Oct NovDec Proportion of annual flux (%) 0 5 10 15 20 25 30 35 J F M A M J J A S O N D Jan FebMar Apr May Jun Jul AugSep Oct NovDec Proportion of annual flux (%) 0 5 10 15 20 J F M A M J J A S O N D Fig. 2. Ten year monthly average precipiation (P), runoff (Q) and Evapo- transpiration (ET). Fig. 3. Ten year average proportion of total Q and DOC export each month. T avg =9.2℃ P avg =2158 mm Q avg =1744 mm ET avg =412 mm T avg =9.1℃ P avg =2632 mm Q avg =2213 mm ET avg =417 mm T avg =6.7℃ P avg =1059 mm Q avg =603 mm ET avg =453 mm T avg =5.7℃ P avg =1222 mm Q avg =873 mm ET avg =326 mm T avg =4.9℃ P avg =980 mm Q avg =577 mm ET avg =401 mm T avg =4.7℃ P avg =1256 mm Q avg =743 mm ET avg =510 mm T avg =1.8℃ P avg =651 mm Q avg =327 mm ET avg =323 mm T avg =-2.2℃ P avg =478 mm Q avg =352 mm ET avg =127 mm Fig. 4. Proportion of DOC exported during the spring and early summer period Average winter temperature ( o C) -16 -12 -8 -4 0 4 8 Proportion of DOC exported during spring (%) 0 20 40 60 80 100 r 2 =0.82 p<0.001 Jan FebMar Apr May Jun Jul AugSep Oct NovDec Proportion of annual flux (%) 0 5 10 15 20 J F M A M J J A S O N D Krycklan Wolf Creek HJ Andrews Dorset Sleepers Girnock Strontian Mharcaidh
