Comparisons of dissolved organic matter and its optical characteristics in small low and high Arctic catchments

Coch, Caroline; Juhls, Bennet; Lamoureux, Scott F.; Lafrenière, Melissa J.; Fritz, Michael; Heim, Birgit; Lantuit, Hugues

doi:10.5194/bg-16-4535-2019

Cited by 30 publications

(40 citation statements)

References 78 publications

(133 reference statements)

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“…In areas of boreal forest, the frost-free period is extended and the surface water can be in contact with soil carbon for a longer time resulting in higher DOC concentrations in boreal lakes. Previous studies confirm that vegetation is an important driver for DOC in permafrost catchments (Harms et al, 2016;Coch et al, 2019). Coch et al (2019) found higher DOC concentrations in moss and plant rich Low Arctic catchment on Herschel Island in Northwest Canada compared to a High Arctic catchment at Cape Bounty, Northeast Canada.…”

Section: Ecoregion Zonation As Key Factor For Pan-arctic Lake Docmentioning

confidence: 68%

“…Previous studies confirm that vegetation is an important driver for DOC in permafrost catchments (Harms et al, 2016;Coch et al, 2019). Coch et al (2019) found higher DOC concentrations in moss and plant rich Low Arctic catchment on Herschel Island in Northwest Canada compared to a High Arctic catchment at Cape Bounty, Northeast Canada. In our database we found high lake DOC concentrations in the boreal forest regions of Interior Alaska which are dominated by white and black spruce (Halm & Griffith, 2014).…”

Section: Ecoregion Zonation As Key Factor For Pan-arctic Lake Docmentioning

confidence: 68%

“…For this synthesis, we searched the scientific literature for the keywords DOC and lakes in permafrost regions and largely focused on local to regional lake DOC syntheses that provided data at the individual lake level (i.e., not averaged values for groups of lakes or regions). From identified references (Pienitz et al, 1997a,b;Hamilton et al, 2001;Lim et al, 2001;Kokelj et al, 2005;Medeiros et al, 2012;Halm & Griffith, 2014;Manasypov et al, 2014;Manasypov et al, 2015;Northington & Saros, 2016;Larsen et al, 2017;Osburn et al, 2017;Coch et al, 2019;Serikova et al, 2019;Johnston et al, 2020) data for 1,757 DOC samples, collected from 1,478 individual lakes, were extracted into a database for further analysis. Unpublished field data of the author team was included in the database (410 samples from 355 lakes).…”

Section: Data Extraction From Existing Studiesmentioning

confidence: 99%

“…et al, 2004;Wickland et al, 2007;Prokushkin et al, 2009;Fritz et al, 2015;Tanski et al, 2016). The export of riverine DOC has also been frequently investigated in the High Arctic (Semkin et al, 2005;Raymond et al, 2007;Holmes et al, 2012, Frey et al, 2016Fouché et al, 2017;Coch et al, 2019), the Low Arctic (Coch et al, 2018), and Subarctic regions (Carey, 2003;Laudon et al, 2004;Petrone et al, 2006). While high-latitude rivers usually have a pronounced seasonal DOC concentration peak during snowmelt (Finlay et al, 2006), this river-borne DOC was found to be utilized rapidly by microbes (Spencer et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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First Pan-Arctic Assessment of Dissolved Organic Carbon in Permafrost-Region Lakes

Stolpmann

Coch

Morgenstern

et al. 2020

Preprint

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Abstract. Lakes in permafrost regions are dynamic landscape components and play an important role for climate change feedbacks. Lake processes such as mineralization and flocculation of dissolved organic carbon (DOC), one of the main carbon fractions in lakes, contribute to the greenhouse effect and are part of the global carbon cycle. These processes are in focus of climate research but studies so far are limited to specific study regions. In our synthesis, we analysed 2,167 water samples from 1,833 lakes across the Arctic in permafrost regions of Alaska, Canada, Greenland, and Siberia to provide first pan-Arctic insights for linkages between DOC concentrations and the environment. Using published data and unpublished datasets from the author team we report regional DOC differences linked to latitude, permafrost zones, ecoregions, geology, near-surface soil organic carbon contents, and ground ice classification of each lake region. The lake DOC concentrations in our dataset range from 0 mg L−1 to 1,130 mg L−1 (10.8 mg L−1 median DOC concentration). Regarding the permafrost regions of our synthesis, we found median lake DOC concentrations of 12.4 mg L−1 (Siberia), 12.3 mg L−1 (Alaska), 10.3 mg L−1 (Greenland), and 4.5 mg L−1 (Canada). Our synthesis shows a significant relationship of lake DOC concentration and ecoregion of the lake. We found higher lake DOC concentrations in boreal permafrost sites compared to tundra sites. About 22 % of the lakes in our extensive dataset are located in regions with ice-rich syngenetic permafrost deposits (yedoma). Yedoma contains large amounts of easily erodible organic carbon and we found significantly higher DOC concentrations in yedoma lakes compared to non-yedoma lakes. Compared to previous studies we found a weak significant relationship of soil organic carbon content and lake DOC concentration as well as between ground-ice content and lake DOC. Our pan-Arctic dataset shows that the DOC concentration of a lake strongly depends on its environmental properties, especially on permafrost extent and ecoregion, as well as vegetation, which is the most important driver of lake DOC in this study. This new dataset will be fundamental to quantify a pan-Arctic lake DOC pool for estimations of the impact of lake DOC on the global carbon cycle and climate change.

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Section: Ecoregion Zonation As Key Factor For Pan-arctic Lake Docmentioning

confidence: 68%

Section: Ecoregion Zonation As Key Factor For Pan-arctic Lake Docmentioning

confidence: 68%

Section: Data Extraction From Existing Studiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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First Pan-Arctic Assessment of Dissolved Organic Carbon in Permafrost-Region Lakes

Stolpmann

Coch

Morgenstern

et al. 2020

Preprint

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“…Percolation and the leaching of older and more degraded DOM from deeper in the soil would explain both observations. Changes in SUVA can be linked to changes in source and age of DOM (Stedmon et al, 2011;O'Donnell et al, 2014;Coch et al, 2019) and can indicate the intensity of permafrost degradation within the catchment (Abbott et al, 2014). Furthermore, direct relationships are found between dissolved organic δ 14 C and SUVA (Neff et al, 2006;Butman et al, 2012;O'Donnell et al, 2014).…”

Section: Drivers Of Seasonal Variability In Hydrochemistry and Dommentioning

confidence: 99%

Identifying Drivers of Seasonality in Lena River Biogeochemistry and Dissolved Organic Matter Fluxes

Juhls

Stedmon

Morgenstern

et al. 2020

Front. Environ. Sci.

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Warming air temperatures, shifting hydrological regimes and accelerating permafrost thaw in the catchments of the Arctic rivers is affecting their biogeochemistry. Arctic river monitoring is necessary to observe changes in the mobilization of dissolved organic matter (DOM) from permafrost. The Lena River is the second largest Arctic river and 71% of its catchment is continuous permafrost. Biogeochemical parameters, including temperature, electrical conductivity (EC), stable water isotopes, dissolved organic carbon (DOC) and absorption by colored dissolved organic matter (a CDOM) have been measured as part of a new high-frequency sampling program in the central Lena River Delta. The results show strong seasonal variations of all biogeochemical parameters that generally follow seasonal patterns of the hydrograph. Optical indices of DOM indicate a trend of decreasing aromaticity and molecular weight from spring to winter. High-frequency sampling improved our estimated annual fluvial flux of annual dissolved organic carbon flux (6.79 Tg C). EC and stable isotope data were used to distinguish three different source water types which explain most of the seasonal variation in the biogeochemistry of the Lena River. These water types match signatures of (1) melt water, (2) rain water, and (3) subsurface water. Melt water and rain water accounted for 84% of the discharge flux and 86% of the DOC flux. The optical properties of melt water DOM were characteristic of fresh organic matter. In contrast, the optical properties of DOM in subsurface water revealed lower aromaticity and lower molecular weights, which indicate a shift toward an older organic matter source mobilized from deeper soil horizons or permafrost deposits. The first year of this new sampling program sets a new baseline for flux calculations of dissolved matter and has enabled the identification and characterization of water types that drive the seasonality of the Lena River water properties.

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Geomorphology and vegetation drive hydrochemistry changes in two Northeast Greenland streams

Pastor

Skovsholt

Christoffersen

et al. 2021

Hydrological Processes

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Climate change is causing drastic landscape changes in the Arctic, but how these changes modify stream biogeochemistry is not clear yet. We examined how catchment properties influence stream nitrogen (N) and dissolved organic carbon concentrations (DOC) in a high-Arctic environment. We sampled two contrasting headwater streams (10-15 stations over 4.8 and 6.8 km, respectively) in Northeast Greenland (74 N). We characterized the geomorphology (i.e., bedrock, solifluction and alluvial types) and the vegetation (i.e., barren, fell field, grassland and tundra types) cover of each subcatchment area draining into each sampling station and collected water samples for hydrochemistry characterization. The two sampled streams differed in geomorphology and vegetation cover in the catchment. Aucellaelv catchment was mostly covered by a 'bedrock' geomorphology (71%) and 'fellfield' vegetation (51%), whereas Kaeerelv was mostly covered by 'alluvial' geomorphology (65%) and 'grassland' and 'tundra' vegetation (42% and 41% respectively). Hydrochemistry also differed between the two study streams, with higher concentrations of inorganic N forms in Aucellaelv and lower DOC concentrations, compared to Kaerelv. The results from the linear mixed model selection showed that vegetation and geomorphology had contrasting effects on stream hydrochemistry. Subcatchments with higher solifluction sheets and limited vegetation had higher nitrate concentrations but lower DOC concentrations. Interestingly, we also found high variability on the production and removal of nitrate across subcatchments. These results indicate landscape controls to nutrient and organic matter exports via flow paths, soil organic matter stocks and nutrient retention via terrestrial vegetation. Moreover, the results suggest that climate change induced alterations to vegetation cover and soil physical disturbance in high-Arctic catchments will affect stream hydrochemistry, with potential effects in stream productivity, trophic relations as well as change of solute export to downstream coastal areas.

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Comparisons of dissolved organic matter and its optical characteristics in small low and high Arctic catchments

Cited by 30 publications

References 78 publications

First Pan-Arctic Assessment of Dissolved Organic Carbon in Permafrost-Region Lakes

First Pan-Arctic Assessment of Dissolved Organic Carbon in Permafrost-Region Lakes

Identifying Drivers of Seasonality in Lena River Biogeochemistry and Dissolved Organic Matter Fluxes

Geomorphology and vegetation drive hydrochemistry changes in two Northeast Greenland streams

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