Alpine Glacier Shrinkage Drives Shift in Dissolved Organic Carbon Export From Quasi‐Chemostasis to Transport Limitation

Canadell, Marta Boix; Escoffier, Nicolas; Ulseth, Amber J.; Lane, Stuart N.; Battin, Tom J.

doi:10.1029/2019gl083424

Cited by 30 publications

(31 citation statements)

References 60 publications

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“…From an ecosystem perspective, glacier‐driven shifts in OC export from coastal watersheds will impact stocks of biolabile OC that can be incorporated into freshwater (Fellman et al, 2015) and marine (Arimitsu et al, 2018) food webs. In the case of DOC, our findings suggest that decreasing glacier coverage is likely to increase riverine yields (Boix Canadell et al, 2019). At the same time, the loss of glacier runoff will decrease the overall bioavailability of the riverine DOC pool (Hood et al, 2009; Singer et al, 2012).…”

Section: Glacier Influence On Riverine Ocmentioning

confidence: 69%

“…To evaluate catchment OC balances, the relationship between runoff ( Q ) and OC yields ( Y ) was modeled using a power function ( Y = aQ b ), where the slope coefficient ( b ) refers to chemostasis ( b = 1), source limitation ( b < 1), or transport ( b > 1) limitation of catchment‐scale OC export (Boix Canadell et al, 2019; Zarnetske et al, 2018). For each model, we report the coefficient of determination ( r 2 ) and p value for the linear fit in log space, and similar to previous studies, our models do not account for temporal autocorrelation in the data (Boix Canadell et al, 2019; Vaughan et al, 2017).…”

Section: Study Sites and Methodsmentioning

confidence: 99%

“…In the glacierized watersheds, the slope coefficients ( b ) for the power law relationship between daily runoff and DOC yields were <1 (Figure 1a) indicating that DOC export is source limited. Glacierized watersheds in the Alps have been shown to be in chemostasis with regard to DOC yields (Boix Canadell et al, 2019). Our finding of source‐limited DOC yields in HR and CC reflects that DOC mobilization from englacial stores (Hood et al, 2015; Li et al, 2018) and the solubilization of OC produced in supraglacial and subglacial environments (Spencer et al, 2014) does not increase proportionally with discharge.…”

Section: Glacier Influence On Riverine Ocmentioning

confidence: 99%

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Glacier Loss Impacts Riverine Organic Carbon Transport to the Ocean

Hood

Fellman

Spencer

2020

Geophysical Research Letters

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Lateral transport of organic carbon (OC) to the coastal ocean is an important component of the global carbon cycle because rivers transport, mineralize, and bury significant amounts of OC. Glaciers drive water and sediment export from many high-elevation and high-latitude ecosystems, yet their role in watershed OC balances is poorly understood, particularly with regard to particulate OC. Here, we evaluate seasonal water, sediment, and comprehensive OC budgets, including both dissolved and particulate forms, for three watersheds in southeast Alaska that vary in glacier coverage. We show that glacier loss will shift the dominant size fraction of riverine OC from particulate toward dissolved and potentially alter the provenance of particulate OC. Glacier coverage also controls whether OC export is source (C stock) or transport (runoff) limited at the watershed scale. These findings provide insight into the future trajectory of riverine OC export in glacierized regions. Plain Language Summary Rivers transport large quantities of organic carbon from the land to the ocean; however, the role that glaciers play in this process is not well understood. We measured organic carbon leaving three watersheds in coastal Alaska that vary in their relative amount of glacier cover to understand how glacier shrinkage will impact the amount and type of organic carbon in rivers. We found that changes in glacier coverage will increase transport of dissolved organic carbon in rivers and decrease transport of particulate organic carbon. Sources of particulate organic carbon in rivers may also change as glaciers shrink. In watersheds, glaciers also appear to influence whether transport of OC in rivers is controlled by the availability of carbon in the watershed versus the availability of water to move that carbon. These findings provide insight into how the loss of glaciers will change the transport of organic carbon in rivers.

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Section: Glacier Influence On Riverine Ocmentioning

confidence: 69%

Section: Study Sites and Methodsmentioning

confidence: 99%

Section: Glacier Influence On Riverine Ocmentioning

confidence: 99%

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Glacier Loss Impacts Riverine Organic Carbon Transport to the Ocean

Hood

Fellman

Spencer

2020

Geophysical Research Letters

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“…changes observed due to deglaciation and varying contributions of glacial meltwater in other locations such as Alaska (Fellman et al, 2014;Hood & Scott, 2008), Canada (Lafrenière & Sharp, 2004), and the Alps (Boix Canadell et al, 2019). These shifts impact both the quantity and quality of DOM exported from landscapes, which may then impact the role of DOM in coastal biogeochemical cycles (Figure 1).…”

Section: 1029/2020gb006614mentioning

confidence: 99%

Differences in the Quantity and Quality of Organic Matter Exported From Greenlandic Glacial and Deglaciated Watersheds

Pain

Martin

et al. 2020

Global Biogeochemical Cycles

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Riverine input of terrestrial dissolved organic matter (DOM) is an important component of the marine carbon cycle and drives net carbon dioxide production in coastal zones. DOM exports to the Arctic Ocean are likely to increase due to melting of permafrost and the Greenland Ice Sheet, but the quantity and quality of DOM exports from deglaciated watersheds in Greenland, as well as expected changes with future melting, are unknown. We compare DOM quantity and quality in Greenland over the melt seasons of 2017-2018 between two rivers directly draining the Greenland Ice Sheet (meltwater rivers) and four streams draining deglaciated catchments that are disconnected from the ice (nonglacial streams). We couple these data with discharge records to compare dissolved organic carbon (DOC) exports. DOM sources and quality differ significantly between watershed types: fluorescence characteristics and organic molar C:N ratios suggest that DOM from deglaciated watersheds is derived from terrestrial vegetation and soil organic matter, while that in glacial watersheds contains greater proportions of algal and/or freshly produced biomass and may be more reactive. DOC specific yield is similar for nonglacial streams (0.1-1.2 Mg/km 2 /year) compared to a glacial meltwater river (0.2-1.1 Mg/km 2 /year), despite orders of magnitude differences in instantaneous discharge. Upscaling based on land cover leads to an estimate of total DOC contributions from Greenland between 0.2 and 0.5 Tg/year, much of which is derived from deglaciated watersheds. These results suggest that future warming and ice retreat may increase DOC fluxes from Greenland with consequences for the Arctic carbon cycle.

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“…Glacier-fed streams (GFSs) are characterized by their low water temperatures, high levels of turbidity and suspended sediment loads, and strong diel and seasonal variability in discharge (Ward, 1994;Uehlinger et al, 2010). The ongoing and widespread increase in glacier mass loss resulting from climate change (Zemp et al, 2015) further adds to the dynamic nature of GFSs through changes in meltwater generation and corresponding dissolved and particulate matter fluxes (Milner et al, 2017;Boix-Canadell et al, 2019). As the climate shifts, increases in meltwater runoff are expected for individual glaciers, but seasonal runoff and particulate fluxes will eventually decline when the diminished ice volume can no longer produce more melt (Milner et al, 2017;Huss and Hock, 2018).…”

Section: Introductionmentioning

confidence: 99%

Patterns and Drivers of Extracellular Enzyme Activity in New Zealand Glacier-Fed Streams

et al. 2020

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Glacier-fed streams (GFSs) exhibit near-freezing temperatures, variable flows, and often high turbidities. Currently, the rapid shrinkage of mountain glaciers is altering the delivery of meltwater, solutes, and particulate matter to GFSs, with unknown consequences for their ecology. Benthic biofilms dominate microbial life in GFSs, and play a major role in their biogeochemical cycling. Mineralization is likely an important process for microbes to meet elemental budgets in these systems due to commonly oligotrophic conditions, and extracellular enzymes retained within the biofilm enable the degradation of organic matter and acquisition of carbon (C), nitrogen (N), and phosphorus (P). The measurement and comparison of these extracellular enzyme activities (EEA) can in turn provide insight into microbial elemental acquisition effort relative to environmental availability. To better understand how benthic biofilm communities meet resource demands, and how this might shift as glaciers vanish under climate change, we investigated biofilm EEA in 20 GFSs varying in glacier influence from New Zealand’s Southern Alps. Using turbidity and distance to the glacier snout normalized for glacier size as proxies for glacier influence, we found that bacterial abundance (BA), chlorophyll a (Chl a), extracellular polymeric substances (EPS), and total EEA per gram of sediment increased with decreasing glacier influence. Yet, when normalized by BA, EPS decreased with decreasing glacier influence, Chl a still increased, and there was no relationship with total EEA. Based on EEA ratios, we found that the majority of GFS microbial communities were N-limited, with a few streams of different underlying bedrock geology exhibiting P-limitation. Cell-specific C-acquiring EEA was positively related to the ratio of Chl a to BA, presumably reflecting the utilization of algal exudates. Meanwhile, cell-specific N-acquiring EEA were positively correlated with the concentration of dissolved inorganic nitrogen (DIN), and both N- and P-acquiring EEA increased with greater cell-specific EPS. Overall, our results reveal greater glacier influence to be negatively related to GFS biofilm biomass parameters, and generally associated with greater microbial N demand. These results help to illuminate the ecology of GFS biofilms, along with their biogeochemical response to a shifting habitat template with ongoing climate change.

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Alpine Glacier Shrinkage Drives Shift in Dissolved Organic Carbon Export From Quasi‐Chemostasis to Transport Limitation

Cited by 30 publications

References 60 publications

Glacier Loss Impacts Riverine Organic Carbon Transport to the Ocean

Glacier Loss Impacts Riverine Organic Carbon Transport to the Ocean

Differences in the Quantity and Quality of Organic Matter Exported From Greenlandic Glacial and Deglaciated Watersheds

Patterns and Drivers of Extracellular Enzyme Activity in New Zealand Glacier-Fed Streams

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