Self‐Shading and Meltwater Spreading Control the Transition From Light to Iron Limitation in an Antarctic Coastal Polynya

Twelves, Andrew G; Goldberg, Daniel; Henley, Sian F.; Mazloff, Matthew R.; Harle, James

doi:10.1029/2020jc016636

Cited by 17 publications

(21 citation statements)

References 78 publications

(229 reference statements)

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“…Interestingly, the peak in chl: C phyto in February occurred close in time to the seasonal maximum in light when cellular pigmentation is expected to be at its lowest, further highlighting the anomalous nature of the physiological response. The strong increase in chl due to the combined effects of phytoplankton growth and increased cellular pigmentation may have eventually led to self‐shading and stagnation of growth (Sakshaug et al., 1991; Twelves et al., 2021), causing the observed time difference between the C phyto and chl peak (Figure 2).…”

Section: Resultsmentioning

confidence: 99%

Southern Ocean Phytoplankton Stimulated by Wildfire Emissions and Sustained by Iron Recycling

Weis

Schallenberg

Chase

et al. 2022

Geophysical Research Letters

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Large ash plumes emitted by the 2019–2020 Australian wildfires were associated with a widespread phytoplankton bloom in the iron‐limited Pacific sector of the Southern Ocean. In this study, we used satellite observations and aerosol reanalysis products to study the regional phytoplankton community response to wildfire emissions. The bloom was stimulated by pyrogenic iron fertilization and coincided with elevated cellular pigment concentrations, increased photochemical efficiency, and apparent community structural shifts. Physiological anomalies were consistent with previously observed phytoplankton responses to iron stress relief and persisted for up to 9 months. Supported by a regional iron budget, we conclude that the bloom was sustained by iron recycling and episodic inputs of pyrogenic and dust‐borne mineral iron. The continuous regeneration of iron was likely facilitated by the bloom's large size, mitigating edge dilution effects, as well as enhanced bioavailability of pyrogenic and mineral iron due to atmospheric and chemical processing during long‐range transport.

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Section: Resultsmentioning

confidence: 99%

Southern Ocean Phytoplankton Stimulated by Wildfire Emissions and Sustained by Iron Recycling

Weis

Schallenberg

Chase

et al. 2022

Geophysical Research Letters

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“…These variations in primary production in bioregions 3 and 5 were thought to be related to the changes in iron, nitrate, phosphate, and silicate (Figure 10). The melting of the ice shelf increases iron availability due to the meltwater pump effect and due to the release of iron entrained at the glacier bed (Twelves et al, 2021). In bioregion 3, the dissolved iron concentrations increased significantly in November and December after 1998; these increased values were more than 2 times higher than those recorded before 1998.…”

Section: Variations In Primary Productivitymentioning

confidence: 93%

Variations in and environmental controls of primary productivity in the Amundsen Sea

Feng

Zhang

et al. 2021

Preprint

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Abstract. The Amundsen Sea is one of the regions with the highest primary productivity in the Antarctic. To better understand the role of the Southern Ocean in the global carbon cycle and in climate regulation, a better understanding of the variations in and environmental controls of primary productivity is needed. Using cluster analysis, the Amundsen Sea was divided into nine bioregions. The biophysical differences among bioregions enhanced confidence to identify priorities and regions to study the temporal and spatial variations in primary productivity. Four nearshore bioregions with high net primary productivity or rapidly increasing rates were selected to analyze temporal and spatial variations in primary productivity in the Amundsen Sea. Due to changes in net solar radiation and sea ice, primary production had significant seasonal variation in these four bioregions. The phenology had changed at two bioregions (3 and 5), which has the third and fourth highest primary production, due to changes in the dissolved iron, nitrate, phosphate, and silicate concentrations. Annual primary production showed increasing trends in these four bioregions. The variation in primary production in the bioregion (9), which has the highest primary production, was mainly affected by variations in sea surface temperatures. In the bioregion, which has the second-highest primary production (8), the primary production was significantly positively correlated with sea surface temperature and significantly negatively correlated with sea ice thickness. The long-term changes of primary productivity in bioregions 3 and 5 were thought to be related to changes in the dissolved iron, nitrate, phosphate, and silicate concentrations, and dissolved iron was the limiting factor in these two bioregions. Bioregionalization not only disentangle multiple factors that control the spatial differences, but also disentangle limiting factors that affect the phenology, decadal and long-term changes in primary productivity.

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“…Subglacial meltwater may be temporarily stored within subglacial lakes, which have been observed to fill and drain, potentially influencing ice flow (Fricker et al, 2007;Smith et al, 2017;Stearns et al, 2008;Wright & Siegert, 2012). Furthermore, the discharge of subglacial meltwater into the ocean provides a flux of freshwater and nutrients, impacting marine biological productivity (Death et al, 2014;Herraiz-Borreguero et al, 2016;Twelves et al, 2021), ocean circulation and enhancing ice-shelf basal melting (Gwyther et al, 2023;Jenkins, 2011;Le Brocq et al, 2013;Wei et al, 2020) with the potential to reduce ice-shelf buttressing (e.g., Reese et al, 2018;Goldberg et al, 2019). Therefore, accurate information about subglacial hydrology is important for understanding both ice-sheet dynamics and ocean properties.…”

Section: Introductionmentioning

confidence: 99%

Characterizing Subglacial Hydrology Within the Amery Ice Shelf Catchment Using Numerical Modeling and Satellite Altimetry

Wearing,

Dow,

Goldberg

et al. 2024

JGR Earth Surface

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Meltwater forms at the base of the Antarctic Ice Sheet due to geothermal heat flux (GHF) and basal frictional dissipation. Despite the relatively small volume, this water has a profound effect on ice‐sheet dynamics. However, subglacial melting and hydrology in Antarctica remain highly uncertain, limiting our ability to assess their impact on ice‐sheet dynamics. Here we examine subglacial hydrology within the Amery Ice Shelf catchment, East Antarctica, using the subglacial hydrology model GlaDS. We calculate subglacial melt rates using a higher‐order ice‐flow model and two GHF estimates. We find a catchment‐wide melt rate of 7.03 Gt year−1 (standard deviation = 1.94 Gt year−1), which is ≥50% greater than previous estimates. The contribution from basal dissipation is approximately 40% of that from GHF. However, beneath fast‐flowing ice streams, basal dissipation is an order of magnitude larger than GHF, leading to a significant increase in channelized subglacial flux upstream of the grounding line. We validate GlaDS using high‐resolution interferometric‐swath radar altimetry, with which we detect active subglacial lakes and fine‐scale ice‐shelf basal melting. We find a network of subglacial channels that connects areas of deep subglacial water coincident with active subglacial lakes, and channelized discharge at the grounding line coinciding with enhanced ice‐shelf basal melting. The concentrated discharge of meltwater provides 36% of the freshwater released into the ice‐shelf cavity, in addition to ice‐shelf basal melting. This suggests that ice‐shelf basal melting is strongly influenced by subglacial hydrology and could be affected by future changes in subglacial discharge, such as lake drainage or channel rerouting.

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Self‐Shading and Meltwater Spreading Control the Transition From Light to Iron Limitation in an Antarctic Coastal Polynya

Cited by 17 publications

References 78 publications

Southern Ocean Phytoplankton Stimulated by Wildfire Emissions and Sustained by Iron Recycling

Southern Ocean Phytoplankton Stimulated by Wildfire Emissions and Sustained by Iron Recycling

Variations in and environmental controls of primary productivity in the Amundsen Sea

Characterizing Subglacial Hydrology Within the Amery Ice Shelf Catchment Using Numerical Modeling and Satellite Altimetry

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