Dissolved iron and manganese in the Canadian Arctic Ocean: On the biogeochemical processes controlling their distributions

Colombo, Manuel; Jackson, Sarah; Cullen, Jay T.; Orians, Kristin J.

doi:10.1016/j.gca.2020.03.012

Cited by 41 publications

(104 citation statements)

References 137 publications

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“…While some of the elevated TdFe and TdMn in these glacier systems will be subject to estuarine removal (Schroth et al., 2014), given the extremely high TdFe and TdMn values observed here, previous observations of elevated DFe and DMn concentrations adjacent to CAA glacier systems that authors have speculated may be partially attributed to glacier sources (Colombo et al., 2020), and signatures of elevated metal availability 10–100s of kilometers from glaciers in other systems (Hopwood et al., 2019), these contributions may significantly influence metal availability in recipient seas. Notably, the Labrador Sea contains regions that bear signatures of elevated metal concentrations, which may be associated with glacier and/or shelf‐derived sources, though this remains speculative to date (Colombo et al., 2020; Tonnard et al., 2020). Studies in the North Atlantic also note high Fe, Mn and other metal concentrations associated with Labrador Sea water masses: these may be consistent with a glacier source, though this requires further investigation (Conway & John, 2014; Noble et al., 2017).…”

Section: Discussionmentioning

confidence: 57%

“…While phytoplankton growth in the CAA is unlikely to be limited by micronutrient availability, regions downstream, including the Labrador Sea, can have areas of extremely low metal concentrations (Colombo et al., 2020), and thus have the potential to be impacted by enhanced metal delivery from upstream CAA glacier sources. While some of the elevated TdFe and TdMn in these glacier systems will be subject to estuarine removal (Schroth et al., 2014), given the extremely high TdFe and TdMn values observed here, previous observations of elevated DFe and DMn concentrations adjacent to CAA glacier systems that authors have speculated may be partially attributed to glacier sources (Colombo et al., 2020), and signatures of elevated metal availability 10–100s of kilometers from glaciers in other systems (Hopwood et al., 2019), these contributions may significantly influence metal availability in recipient seas. Notably, the Labrador Sea contains regions that bear signatures of elevated metal concentrations, which may be associated with glacier and/or shelf‐derived sources, though this remains speculative to date (Colombo et al., 2020; Tonnard et al., 2020).…”

Section: Discussionmentioning

confidence: 99%

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Glaciers and Nutrients in the Canadian Arctic Archipelago Marine System

Bhatia

Waterman

Burgess

et al. 2021

Global Biogeochemical Cycles

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Delivery of meltwater and materials from glaciers to the ocean is accelerating due to climate warming, with important and poorly characterized consequences for the marine environment. While the contributions of these shrinking ice masses to sea level rise are undisputed, their role in marine biogeochemical processes is just beginning to be revealed. Recent studies have shown that glacial meltwater discharge

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Section: Discussionmentioning

confidence: 57%

Section: Discussionmentioning

confidence: 99%

Glaciers and Nutrients in the Canadian Arctic Archipelago Marine System

Bhatia

Waterman

Burgess

et al. 2021

Global Biogeochemical Cycles

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“…Dissolved Co (dCo) is less prone to scavenging than Fe, and dissolved Mn (dMn) generally shows increased dissolved concentrations in near-surface waters due to a more pronounced positive effect of photochemical cycling on its stability (e.g., refs. 50 , 51 ).…”

Section: Resultsmentioning

confidence: 99%

The 79°N Glacier cavity modulates subglacial iron export to the NE Greenland Shelf

et al. 2021

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Approximately half of the freshwater discharged from the Greenland and Antarctic Ice Sheets enters the ocean subsurface as a result of basal ice melt, or runoff draining via the grounding line of a deep ice shelf or marine-terminating glacier. Around Antarctica and parts of northern Greenland, this freshwater then experiences prolonged residence times in large cavities beneath floating ice tongues. Due to the inaccessibility of these cavities, it is unclear how they moderate the freshwater associated supply of nutrients such as iron (Fe) to the ocean. Here, we show that subglacial dissolved Fe export from Nioghalvfjerdsbrae (the ‘79°N Glacier’) is decoupled from particulate inputs including freshwater Fe supply, likely due to the prolonged ~162-day residence time of Atlantic water beneath Greenland’s largest floating ice-tongue. Our findings indicate that the overturning rate and particle-dissolved phase exchanges in ice cavities exert a dominant control on subglacial nutrient supply to shelf regions.

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“…In contrast, the low F v / F m values recorded in the Lancaster Sound were not associated with high σ PSII , and correlation analysis of night-time σ PSII and F v / F m values revealed a weak positive relationship between σ PSII and F v / F m ( r = 0.17, p < 0.05, n = 214). Based on these results, and the proximity of our sampling to land-based Fe sources [53], we infer that nitrogen, rather than iron deficiency was the most likely cause of low photo-efficiencies observed from August 10-13 in Lancaster Sound.…”

Section: Discussionmentioning

confidence: 92%

Chlorophyll fluorescence-based estimates of photosynthetic electron transport in Arctic phytoplankton assemblages

Sezginer

Suggett

Izett

et al. 2021

Preprint

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We employed Fast Repetition Rate fluorometry for high-resolution mapping of marine phytoplankton photophysiology and primary productivity in the Lancaster Sound and Barrow Strait regions of the Canadian Arctic Archipelago in the summer of 2019. Continuous ship-board analysis of chlorophyll a variable fluorescence demonstrated relatively low photochemical efficiency over most of the cruise-track, with the exception of localized regions within Barrow Strait where there was increased vertical mixing and proximity to land-based nutrient sources. Along the full transect, we observed strong non-photochemical quenching of chlorophyll fluorescence, with relaxation times longer than the 5-minute period used for dark acclimation. Such long-term quenching effects complicate continuous underway acquisition of fluorescence amplitude-based estimates of photosynthetic electron transport rates, which rely on dark acclimation of samples. As an alternative, we employed a new algorithm to derive electron transport rates based on analysis of fluorescence relaxation kinetics, which does not require dark acclimation. Direct comparison of kinetics- and amplitude-based electron transport rate measurements demonstrated kinetic-based estimates were, on average, 2-fold higher than amplitude-based values. The magnitude of decoupling between the two electron transport rate estimates increased in association with photophysiological diagnostics of nutrient stress. Discrepancies between electron transport rate estimates likely resulted from the use of different photophysiological parameters to derive the kinetics- and amplitude-based algorithms, and choice of numerical model used to fit variable fluorescence curves and analyze fluorescence kinetics under actinic light. Our results highlight environmental and methodological influences on fluorescence-based productivity estimates, and prompt discussion of best-practices for future underway fluorescence-based efforts to monitor phytoplankton photosynthesis.

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Dissolved iron and manganese in the Canadian Arctic Ocean: On the biogeochemical processes controlling their distributions

Cited by 41 publications

References 137 publications

Glaciers and Nutrients in the Canadian Arctic Archipelago Marine System

Glaciers and Nutrients in the Canadian Arctic Archipelago Marine System

The 79°N Glacier cavity modulates subglacial iron export to the NE Greenland Shelf

Chlorophyll fluorescence-based estimates of photosynthetic electron transport in Arctic phytoplankton assemblages

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