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Waterborne Carbon in Northern Streams: Controls on dissolved carbon transport across sub-arctic Scandinavia
Stockholm University, Faculty of Science, Department of Physical Geography. (Hydrology)
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Waterborne carbon (C) forms an active and significant part of the global C cycle, which is important in theArctic where greater temperature increases and variability are anticipated relative to the rest of the globe withpotential implications for the C cycle. Understanding and quantification of the current processes governing themovement of C by connecting terrestrial and marine systems is necessary to better estimate future changes ofwaterborne C. This thesis investigates how the sub-arctic landscape influences the waterborne carbon exportby combining data-driven and modeling methods across spatial and temporal scales. First, a study of the stateof total organic carbon monitoring in northern Scandinavia was carried out using national-scale monitoringdata and detailed data from scientific literature. This study, which highlights the consistency in land cover andhydroclimatic controls on waterborne C across northern Scandinavia, was combined with three more detailedstudies leveraging field measurements and modeling. These focused on the Abisko region to provide insightto processes and mechanisms across scales. The thesis highlights that the governing transport mechanismsof dissolved organic and inorganic carbon (DOC and DIC respectively) are fundamentally different due todifferences in release rates associated with the nature of their terrestrial sources (geogenic and organic matterrespectively). As such, the DIC mass flux exhibits a high flow-dependence whereas DOC is relatively flowindependent.Furthermore, these investigations identified significant relationships between waterborne C andbiogeophysical as well as hydroclimatic variables across large to small spatial scales. This thesis demonstratesthat both surface and sub-surface hydrological processes (such as flow pathway distributions) in combinationwith distributions of C sources and associated release rates are prerequisite for understanding waterborne Cdynamics in northern streams.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography, Stockholms Universitet , 2015.
Series
Dissertations from the Department of Physical Geography, ISSN 1653-7211 ; 48
Keyword [en]
dissolved carbon, DOC, DIC, TOC, sub-arctic, hydrology, Abisko
National Category
Physical Geography
Research subject
Physical Geography
Identifiers
URN: urn:nbn:se:su:diva-115883ISBN: 978-91-7649-141-6 (print)OAI: oai:DiVA.org:su-115883DiVA: diva2:800639
Public defence
2015-05-22, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 2007-8393
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 4: Accepted.

Available from: 2015-04-29 Created: 2015-04-07 Last updated: 2015-04-30Bibliographically approved
List of papers
1. The state of dissolved carbon export across boreal and tundra environments in Scandinavia
Open this publication in new window or tab >>The state of dissolved carbon export across boreal and tundra environments in Scandinavia
(English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026Article in journal (Refereed) Submitted
National Category
Earth and Related Environmental Sciences
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-115259 (URN)
Available from: 2015-03-18 Created: 2015-03-18 Last updated: 2017-12-04Bibliographically approved
2. Subsurface release and transport of dissolved carbon in a discontinuous permafrost region
Open this publication in new window or tab >>Subsurface release and transport of dissolved carbon in a discontinuous permafrost region
2013 (English)In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 17, no 10, 3827-3839 p.Article in journal (Refereed) Published
Abstract [en]

Subsurface hydrological flow pathways and advection rates through the landscape affect the quantity and timing of hydrological transport of dissolved carbon. This study investigates hydrological carbon transport through the subsurface to streams and how it is affected by the distribution of subsurface hydrological pathways and travel times through the landscape. We develop a consistent mechanistic, pathway- and travel time-based modeling approach for release and transport of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC). The model implications are tested against observations in the subarctic Abiskojokken catchment in northernmost Sweden (68 degrees 21'N, 18 degrees 49'E) as a field case example of a discontinuous permafrost region. The results show: (a) For DOC, both concentration and load are essentially flow-independent because their dynamics are instead dominated by the annual renewal and depletion. Specifically, the flow independence is the result of the small characteristic DOC respiration-dissolution time scale, in the range of 1 yr, relative to the average travel time of water through the subsurface to the stream. (b) For DIC, the load is highly flow-dependent due to the large characteristic weathering-dissolution time, much larger than 1 yr, relative to the average subsurface water travel time to the stream. This rate relation keeps the DIC concentration essentially flow-independent, and thereby less fluctuating in time than the DIC load.

National Category
Oceanography, Hydrology, Water Resources
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-97404 (URN)10.5194/hess-17-3827-2013 (DOI)000326603200010 ()
Funder
Swedish Research Council, 2007-8393
Note

AuthorCount:3;

Available from: 2013-12-11 Created: 2013-12-09 Last updated: 2017-12-06Bibliographically approved
3. Catchment-scale dissolved carbon concentrations and exportestimates across six subarctic streams in northern Sweden
Open this publication in new window or tab >>Catchment-scale dissolved carbon concentrations and exportestimates across six subarctic streams in northern Sweden
Show others...
2014 (English)In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, 525-537 p.Article in journal (Refereed) Published
Abstract [en]

Climatic change is currently enhancing permafrostthawing and the flow of water through the landscape in subarcticand arctic catchments, with major consequences forthe carbon export to aquatic ecosystems. We studied streamwater carbon export in several tundra-dominated catchmentsin northern Sweden. There were clear seasonal differencesin both dissolved organic carbon (DOC) and dissolved inorganiccarbon (DIC) concentrations. The highest DOC concentrationsoccurred during the spring freshet while the highestDIC concentrations were always observed during winterbaseflow conditions for the six catchments considered in thisstudy. Long-term trends for the period 1982 to 2010 for oneof the streams showed that DIC concentrations has increasedby 9% during the 28 yr of measurement while no clear trendwas found for DOC. Similar increasing trends were alsofound for conductivity, Ca and Mg. When trends were discretizedinto individual months, we found a significant linearincrease in DIC concentrations with time for September,November and December. In these subarctic catchments, theannual mass of C exported as DIC was in the same orderof magnitude as DOC; the average proportion of DIC to thetotal dissolved C exported was 61% for the six streams. Furthermore,there was a direct relationship between total runoffand annual dissolved carbon fluxes for these six catchments.These relationships were more prevalent for annual DIC exportsthan annual DOC exports in this region. Our results alsohighlight that both DOC and DIC can be important in highlatitudeecosystems. This is particularly relevant in environmentswhere thawing permafrost and changes to subsurfaceice due to global warming can influence stream water fluxesof C. The large proportion of stream water DIC flux also hasimplications on regional C budgets and needs to be consideredin order to understand climate-induced feedback mechanismsacross the landscape.

National Category
Earth and Related Environmental Sciences
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-114282 (URN)10.5194/bg-11-525-2014 (DOI)
Available from: 2015-02-25 Created: 2015-02-25 Last updated: 2017-12-04Bibliographically approved
4. Spatial Variability of Dissolved Organic and Inorganic Carbon in Subarctic Headwater Streams
Open this publication in new window or tab >>Spatial Variability of Dissolved Organic and Inorganic Carbon in Subarctic Headwater Streams
2015 (English)In: Arctic, Antarctic and Alpine research, ISSN 1523-0430, E-ISSN 1938-4246, Vol. 47, no 3, 529-546 p.Article in journal (Refereed) Published
Abstract [en]

The subarctic landscape is composed of a complex mosaic of vegetation, geology and topography, which control both the hydrology and biogeochemistry of streams across space and time. We present a synoptic sampling campaign that aimed to estimate dissolved C export variability under low-flow conditions from a subarctic landscape. The results included measurements of stream discharge and concentrations of both dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and carbon dioxide (CO2) for 32 subcatchments of the Abiskojokka catchment in northern Sweden. For these subarctic headwater streams, we found that DOC, DIC and CO2 concentrations showed significant variability (p < 0.05) relative to catchment size, discharge, specific discharge, lithology, electrical conductivity, weathering products, and the estimated travel time of water through the subcatchment. Our results indicate that neither vegetation cover nor lithology alone could explain the concentrations and mass flux rates of DOC and DIC. Instead, we found that mass flux rates of DOC, DIC, and CO2 depended mainly on specific discharge and water travel time. Furthermore, our results demonstrate the importance of studying lateral carbon transport in combination with hydrological flow paths at small scales to establish a knowledge foundation applicable for expected carbon cycle and hydroclimatic shifts due to climate change.

National Category
Earth and Related Environmental Sciences
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-115245 (URN)10.1657/AAAR0014-044 (DOI)000359679000011 ()
Available from: 2015-03-18 Created: 2015-03-18 Last updated: 2017-04-24Bibliographically approved

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