Lability of DOC transported by Alaskan rivers to the Arctic Ocean

Holmes, Robert M.; McClelland, J. W.; Raymond, Peter A.; Frazer, Breton B.; Peterson, Bruce J.; Stieglitz, Marc

doi:10.1029/2007gl032837

Cited by 314 publications

(389 citation statements)

References 28 publications

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“…This is consistent with results from studies in other subarctic and arctic rivers (Striegl et al, 2005Raymond et al, 2007;Walvoord and Striegl, 2007;McNamara et al, 2008;Frey and McClelland, 2009;Guo et al, 2012). The DOC mobilized during high f low events is generally believed to be of modern age (Guo and Macdonald, 2006;Neff et al, 2006) and part of the DOC transported during spring melt may be labile (Holmes et al, 2008). Where changes in permafrost extent are sufficient to alter f lowpaths, the carbon balance of subarctic watersheds could shift from a net sink to a net source Grosse et al, 2011).…”

Section: Interior Alaska Wetlands and Hydrogeologysupporting

confidence: 79%

Sources and sinks of carbon in boreal ecosystems of interior Alaska: A review

Douglas

Jones

Hiemstra

et al. 2014

Elementa: Science of the Anthropocene

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Boreal ecosystems store large quantities of carbon but are increasingly vulnerable to carbon loss due to disturbance and climate warming. The boreal region in Alaska and Canada, largely underlain by discontinuous permafrost, presents a challenging landscape for itemizing carbon sources and sinks in soil and vegetation. The roles of fire, forest succession, and the presence (or absence) of permafrost on carbon cycle, vegetation, and hydrologic processes have been the focus of multidisciplinary research in boreal ecosystems for the past 20 years. However, projections of a warming future climate, an increase in fire severity and extent, and the potential degradation of permafrost could lead to major landscape and carbon cycle changes over the next 20 to 50 years. To assist land managers in interior Alaska in adapting and managing for potential changes in the carbon cycle we developed this review paper by incorporating an overview of the climate, ecosystem processes, vegetation, and soil regimes. Our objective is to provide a synthesis of the most current carbon storage estimates and measurements to guide policy and land management decisions on how to best manage carbon sources and sinks. We surveyed estimates of aboveground and belowground carbon stocks for interior Alaska boreal ecosystems and summarized methane and carbon dioxide f luxes. These data have been converted into similar units to facilitate comparison across ecosystem compartments. We identify potential changes in the carbon cycle with climate change and human disturbance. A novel research question is how compounding disturbances affect carbon sources and sinks associated with boreal ecosystem processes. Finally, we provide recommendations to address the challenges facing land managers in efforts to manage carbon cycle processes. The results of this study can be used for carbon cycle management in other locations within the boreal biome which encompasses a broad distribution from 45° to 83° north.

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Section: Interior Alaska Wetlands and Hydrogeologysupporting

confidence: 79%

Sources and sinks of carbon in boreal ecosystems of interior Alaska: A review

Douglas

Jones

Hiemstra

et al. 2014

Elementa: Science of the Anthropocene

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“…It has been suggested that warming will increase mobilization of soil DOC and DON due to exposure of previously frozen organic material (Frey et al 2007a;Frey and McClelland 2009). This change might not be reflected in DOC and DON concentrations, since this material is rapidly consumed in the stream, especially during spring snowmelt (Holmes et al 2008). In other words, an increase in export of terrestrial organic matter combined with rapid in-stream transformations of DOC and DON might be responsible for the observed increase in NO 3 -concentrations.…”

Section: Changes In C and N Flux In The Kuparuk Rivermentioning

confidence: 99%

“…2b, respectively). The solid lines and symbols represent samples taken during the rising hydrograph, and the open symbols and dashed lines represent samples taken during the falling hydrograph Biogeochemistry (2011) 103:109-124 117 Kuparuk River showed that 20-40% of the DOC transported by rivers in the early spring is microbially available, while late-summer DOC is much less labile (Holmes et al 2008). Seasonally varying UV photolysis (Wetzel et al 1995) may also contribute to changes in discharge-specific DOC concentrations as the summer progresses.…”

Section: Seasonal Variations In Constituent Exportmentioning

confidence: 99%

Seasonal and hydrologic drivers of dissolved organic matter and nutrients in the upper Kuparuk River, Alaskan Arctic

et al. 2010

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As the planet warms, widespread changes in Arctic hydrology and biogeochemistry have been documented and these changes are expected to accelerate in the future. Improved understanding of the behavior of water-borne constituents in Arctic rivers with varying hydrologic conditions, including seasonal variations in discharge-concentration relationships, will improve our ability to anticipate future changes in biogeochemical budgets due to changing hydrology. We studied the relationship between seasonal water discharge and dissolved organic carbon and nitrogen (DOC and DON) and nutrient concentrations in the upper Kuparuk River, Arctic Alaska. Fluxes of most constituents were highest during initial snowmelt runoff in spring, indicating that this historically under-studied period contributes significantly to total annual export. In particular, the initial snowmelt period (the stream is completely frozen during the winter) accounted for upwards of 35% of total export of DOC and DON estimated for the entire study period. DOC and DON concentrations were positively correlated with discharge whereas nitrate (NO 3 -) and silicate were negatively correlated with discharge throughout the study. However, discharge-specific DOC and DON concentrations (i.e. concentrations compared at the same discharge level) decreased over the summer whereas discharge-specific concentrations of NO 3 -and silicate increased. Soluble reactive phosphorus (SRP) and ammonium (NH 4 ? ) were negatively correlated with discharge during the spring thaw, but were less predictable with respect to discharge thereafter. These data provide valuable information on how Arctic watershed biogeochemistry will be affected by future changes in temperature, snowfall, and rainfall in the Arctic. In particular, our results add to a growing body of research showing that nutrient export per unit of stream discharge, particularly NO 3 -, is increasing in the Arctic.

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“…About 17 % of the DOC was reported to be biologically available in lake, river, and marine ecosystems (Sondergaard and Middelboe, 1995). Recently, studies have shown that a significant fraction (∼ 30 %) of Arctic river DOC is degradable in the Arctic Ocean on a scale of 1-2 years (Alling et al, 2010;Holmes et al, 2008) -longer than the shallow shelf water residence time, which is on the order of several weeks (Nikiforov and Shpaikher, 1980;Semiletov et al, 2000). Thus, in the near-shore zone, riverine DOC can be considered a quasiconservative parameter.…”

Section: Biogeochemical Signatures Of Organic Matter Degradation In Smentioning

confidence: 99%

Space–time dynamics of carbon and environmental parameters related to carbon dioxide emissions in the Buor-Khaya Bay and adjacent part of the Laptev Sea

et al. 2013

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This study aims to improve understanding of carbon cycling in the Buor-Khaya Bay (BKB) and adjacent part of the Laptev Sea by studying the inter-annual, seasonal, and meso-scale variability of carbon and related hydrological and biogeochemical parameters in the water, as well as factors controlling carbon dioxide (CO₂) emission. Here we present data sets obtained on summer cruises and winter expeditions during 12 yr of investigation. Based on data analysis, we suggest that in the heterotrophic BKB area, input of terrestrially borne organic carbon (OC) varies seasonally and inter-annually and is largely determined by rates of coastal erosion and river discharge. Two different BKB sedimentation regimes were revealed: Type 1 (erosion accumulation) and Type 2 (accumulation). A Type 1 sedimentation regime occurs more often and is believed to be the quantitatively most important mechanism for suspended particular matter (SPM) and particulate organic carbon (POC) delivery to the BKB. The mean SPM concentration observed in the BKB under a Type 1 regime was one order of magnitude greater than the mean concentration of SPM (~ 20 mg L⁻¹) observed along the Lena River stream in summer 2003. Loadings of the BKB water column with particulate material vary by more than a factor of two between the two regimes. Higher partial pressure of CO₂ (pCO₂), higher concentrations of nutrients, and lower levels of oxygen saturation were observed in the bottom water near the eroded coasts, implying that coastal erosion and subsequent oxidation of eroded organic matter (OM) rather than the Lena River serves as the predominant source of nutrients to the BKB. Atmospheric CO₂ fluxes from the sea surface in the BKB vary from 1 to 95 mmol m⁻² day⁻¹ and are determined by specific features of hydrology and wind conditions, which change spatially, seasonally, and inter-annually. Mean values of CO₂ emission from the shallow Laptev Sea were similar in September 1999 and 2005 (7.2 and 7.8 mmol m⁻² day⁻¹, respectively), while the CO₂ efflux can be one order lower after a strong storm such as in September 2011. Atmospheric CO₂ emissions from a thawed coastal ice complex in the BKB area varied from 9 to 439 mmol m⁻² day⁻¹, with the mean value ranged from 75.7 to 101 mmol m⁻² day⁻¹ in two years (September 2006 and 2009), suggesting that at the time of observations the eroded coastal area served as a more significant source of CO₂ to the atmosphere than the tundra (mean value: 22.7 mmol m⁻² day⁻¹) on the neighboring Primorsky coastal plain (September 2006). The observed increase in the Lena River discharge since the 1990s suggests that increased levels of "satellite-derived" annual primary production could be explained by an increasing load of humic acids delivered to shelf water; in this water the color resulting from the presence of CDOM (colo...

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Lability of DOC transported by Alaskan rivers to the Arctic Ocean

Cited by 314 publications

References 28 publications

Sources and sinks of carbon in boreal ecosystems of interior Alaska: A review

Sources and sinks of carbon in boreal ecosystems of interior Alaska: A review

Seasonal and hydrologic drivers of dissolved organic matter and nutrients in the upper Kuparuk River, Alaskan Arctic

Space–time dynamics of carbon and environmental parameters related to carbon dioxide emissions in the Buor-Khaya Bay and adjacent part of the Laptev Sea

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