The eastern extent of seasonal iron limitation in the high latitude North Atlantic Ocean

Birchill, Antony J.; Hartner, N. T.; Kunde, Korinna; Siemering, Beatrix; Daniels, Chris J.; González-Santana, David; Milne, Angela; Ussher, Simon J.; Worsfold, Paul J.; Leopold, Kerstin; Painter, Stuart C.; Lohan, Maeve C.

doi:10.1038/s41598-018-37436-3

Cited by 20 publications

(15 citation statements)

References 74 publications

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“…There were elevated concentrations for a range of elements (DAl: 45 nM; DMn: 3.20 nM, TDMn 8.78 nM; DZn: 0.625 nM, TDZn 1.30 nM) directly under the volcanic plume (63.1°N, 18.5°W) in the immediate vicinity of the Icelandic coast (Table 1), but with no increases for Co, Cd, Cu, Ni, and Pb compared with surface waters that were not influenced by the volcanic ash inputs (further discussion is provided in aerosol section below). Enhanced DAl, DCd, DCo, DCu, DPb, DNi, DMn, and DZn concentrations were also observed on the Scottish Shelf (Figure 2), likely due to continental and benthic inputs; indeed the elevated DMn (8.73 nM) on this shelf provided a strong indication of benthic release (Birchill et al, 2019; Burdige, 1993).…”

Section: Resultsmentioning

confidence: 93%

Trace Element Biogeochemistry in the High‐Latitude North Atlantic Ocean: Seasonal Variations and Volcanic Inputs

Achterberg

Steigenberger

Klar

et al. 2021

Global Biogeochemical Cycles

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We present dissolved and total dissolvable trace elements for spring and summer cruises in 2010 in the high-latitude North Atlantic. Surface and full depth data are provided for Al, Cd, Co, Cu, Mn, Ni, Pb, and Zn in the Iceland and Irminger Basins, and consequences of biological uptake and inputs by the spring Eyjafjallajökull volcanic eruption are assessed. Ash from Eyjafjallajökull resulted in pronounced increases in Al, Mn, and Zn in surface waters in close proximity to Iceland during the eruption, while 3 months later during the summer cruise levels had returned to more typical values for the region. The apparent seasonal removal ratios of surface trace elements were consistent with biological export. Assessment of supply of trace elements to the surface mixed layer for the region, excluding volcanic inputs, indicated that deep winter mixing was the dominant source, with diffusive mixing being a minor source (between 13.5% [dissolved Cd, DCd] and −2.43% [DZn] of deep winter flux), and atmospheric inputs being an important source only for DAl and DZn (DAl up to 42% and DZn up to 4.2% of deep winter + diffusive fluxes) and typically less than 1% for the other elements. Elemental supply ratios to the surface mixed layer through convection were comparable to apparent removal ratios we calculated between spring and summer. Given that deep mixing dominated nutrient and trace element supply to surface waters, predicted increases in water column stratification in this region may reduce supply, with potential consequences for primary production and the biological carbon pump.

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Section: Resultsmentioning

confidence: 93%

Trace Element Biogeochemistry in the High‐Latitude North Atlantic Ocean: Seasonal Variations and Volcanic Inputs

Achterberg

Steigenberger

Klar

et al. 2021

Global Biogeochemical Cycles

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“…Iron limitation in the western North Atlantic has received little attention, but field measurements in summer 2010 captured surface iron concentrations near zero in Labrador Sea (Rijkenberg et al, ). Likewise, field measurements in the high‐latitude eastern North Atlantic and the central Arctic indicate that iron indeed limits phytoplankton productivity in some regions (Birchill et al, ; Nielsdóttir et al, ; Rijkenberg et al, ). These results suggest that further exploring iron limitation in the Labrador Sea could be a worthy target of future research.…”

Section: Discussionmentioning

confidence: 99%

Assessing the Role of High‐Frequency Winds and Sea Ice Loss on Arctic Phytoplankton Blooms in an Ice‐Ocean‐Biogeochemical Model

et al. 2019

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The long‐term trend of increasing phytoplankton net primary production (NPP) in the Arctic correlates with increasing light penetration due to sea ice loss. However, recent studies suggest that enhanced stormy wind mixing may also play a significant role enhancing NPP. Here, we isolate the role of sea ice and stormy winds (hereafter high‐frequency winds) using an eddy‐permitting ice‐ocean‐biogeochemical model configured for the North Atlantic and the Arctic. In the model, the presence of high‐frequency winds stimulates nutrient upwelling by producing an earlier and longer autumn‐winter mixing period with deeper mixing layer. The early onset of autumn mixing results in nutrients being brought‐up to near‐surface waters before the light becomes the dominant limiting factor, which leads to the autumn bloom. The enhanced mixing results in higher nutrient concentrations in spring and thus a large spring bloom. The model also shows significant iron limitation in the Labrador Sea, which is intensified by high‐frequency winds. The effect of sea ice loss on NPP was found to be regionally dependent on the presence of high‐frequency winds. This numerical study suggests high‐frequency winds play significant role increasing NPP in the Arctic and sub‐Arctic by alleviating phytoplankton nutrient limitation and that the isolated effect of sea ice loss on light plays a comparatively minor role.

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“…Even though the water contains sufficient amounts of nitrate, nitrogen metabolic pathways of phytoplankton such as nitrogen fixation and nitrate + nitrite reduction are inhibited under very low concentrations of Fe (e.g., Morel & Price, 2003; Twining & Baines, 2013). The dFe:nitrate (+ nitrite) ratio in seawaters is a comprehensive tool to identify the factor limiting the phytoplankton community by comparing the ratio in seawaters to cellular Fe:nitrogen (N) ratios in phytoplankton (Birchill et al, 2019). Limited information is available on phytoplankton cellular Fe:N ratios in the coastal regions around Greenland.…”

Section: Discussionmentioning

confidence: 99%

Iron Supply by Subglacial Discharge Into a Fjord Near the Front of a Marine‐Terminating Glacier in Northwestern Greenland

Kanna

Sugiyama

Fukamachi

et al. 2020

Global Biogeochemical Cycles

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Glacial fjords in Greenland show high productivity owing to the runoff of meltwater from the glaciers. Macronutrient dynamics (of nitrate, phosphate, and silicate) associated with subglacial discharge plumes in front of marine-terminating glaciers are widely cited as important drivers of summer phytoplankton blooms in the fjords. However, the dynamics of iron (Fe), an essential micronutrient for primary production, remain largely unstudied in glacial fjords. To investigate the role of subglacial discharge plumes in Fe supply processes in glacial fjords, a comprehensive survey of Bowdoin Fjord, adjacent to the marine-terminating Bowdoin Glacier in northwestern Greenland, was conducted. The subglacial discharge of Fe-rich meltwater induces a buoyancy-driven upwelling plume in front of the glacier that entrains nutrient-rich Arctic-and Atlantic-origin waters. The plume water potentially carried 4.5-8.7 × 10 7 g day −1 of total dissolvable Fe out of Bowdoin Fjord in summer. The concentration of dissolved Fe (dFe) in the plume water (~15.6 nmol kg −1) was 4 times higher than that in the water in the outer part of the fjord (~3.8 nmol kg −1). The dFe:nitrate + nitrite ratio (mmol mol −1) in the plume water varied between 0.58 and 3.2, several orders of magnitude higher than the phytoplankton cellular Fe:nitrate ratio estimated using the hypothetical Fe:C ratio and observed particulate organic carbon:nitrate ratio of the fjord. Hence, the plume water is replete with Fe with respect to phytoplankton demands. Subglacial discharge drives the upwelling of Fe and macronutrients toward the euphotic zone, which is vital for the generation of summer phytoplankton growth in glacial fjords.

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The eastern extent of seasonal iron limitation in the high latitude North Atlantic Ocean

Cited by 20 publications

References 74 publications

Trace Element Biogeochemistry in the High‐Latitude North Atlantic Ocean: Seasonal Variations and Volcanic Inputs

Trace Element Biogeochemistry in the High‐Latitude North Atlantic Ocean: Seasonal Variations and Volcanic Inputs

Assessing the Role of High‐Frequency Winds and Sea Ice Loss on Arctic Phytoplankton Blooms in an Ice‐Ocean‐Biogeochemical Model

Iron Supply by Subglacial Discharge Into a Fjord Near the Front of a Marine‐Terminating Glacier in Northwestern Greenland

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