Sensitivity of ocean biogeochemistry to the iron supply from the Antarctic Ice Sheet explored with a biogeochemical model

Person, Renaud; Aumont, Olivier; Madec, Gurvan; Vancoppenolle, Martin; Bopp, Laurent; Merino, Nacho

doi:10.5194/bg-16-3583-2019

Cited by 26 publications

(42 citation statements)

References 105 publications

(226 reference statements)

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“…Wadley et al (2014) estimated the contribution of Fe in sea ice to SO primary production to 11%, which is significantly lower than their 75% estimated for the sedimentary Fe source. For C export, a contribution of sea ice of less than 4% is estimated in the SO (Wang et al, 2014), which falls within the 1-30% range of the contribution estimated for the iceberg-ice shelf Fe source (Laufkötter et al, 2018;Person et al, 2019;Wadley et al, 2014).…”

Section: Should Primary Production and Carbon Export Estimates Be Revsupporting

confidence: 75%

“…Although nonlinear, but showing a clear trend in which higher primary productivity is associated with higher C export in the model (Person et al., 2019), the contribution of sea ice to primary productivity results in an increase in C export ranging from 9% to 19% in all four experiments relative to CTL. The increase in C export is at least twice as high as that of Wang et al.…”

Section: Discussionmentioning

confidence: 92%

“…Our study also overlooks the continental glacial inputs of Fe: The external source of Fe from icebergs and ice shelves is not included, which represents a potentially important Fe reservoir in the SO (Hopwood et al., 2019; Laufkötter et al., 2018; Person et al., 2019; Raiswell et al., 2016). Synergies between melting icebergs‐ice shelves and incorporation in growing sea ice could occur, leading to increased Fe transport by sea ice, particularly in the coastal regions of Antarctica, and changing its distribution throughout the SO.…”

Section: Discussionmentioning

confidence: 99%

“…These cryospheric elements reduce light availability at the ocean surface. However, they are also iron laden, which is thought to stimulate productivity and carbon export (Duprat et al., 2016; Lin et al., 2011; Raiswell et al., 2016; Wadley et al., 2014; Wang et al., 2014), to an extent that remains subject to large uncertainties (Hopwood et al., 2019; Person et al., 2019). Among these ice forms, sea ice is considered as one of the important Fe sources in the SO (Boyd & Ellwood, 2010; Geibert et al., 2010; Lannuzel et al., 2016; Tagliabue et al., 2017; Vancoppenolle et al., 2013), acting as a spatially extended reservoir, and transporting Fe from coastal to offshore regions, with coastal sediments being the main Fe source (Lancelot et al., 2009; Lannuzel et al., 2010; Sedwick & DiTullio, 1997; Wadley et al., 2014).…”

Section: Introductionmentioning

confidence: 99%

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Iron Incorporation From Seawater Into Antarctic Sea Ice: A Model Study

Person

Vancoppenolle

Aumont

2020

Global Biogeochemical Cycles

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Sea ice acts as an iron (Fe) reservoir in the Southern Ocean (SO) where primary productivity is largely Fe limited. The mechanisms leading to Fe enrichment in sea ice result from the combination of poorly understood and largely unexplored physical and biological processes. We analyze the biogeochemical impacts of three plausible idealized formulations of dissolved Fe (DFe) incorporation into sea ice corresponding to (i) constant Fe concentration in sea ice, (ii) constant ocean-ice Fe flux, and (iii) ocean-ice Fe flux linearly varying with seawater Fe concentration in a global ocean-sea-ice-biogeochemical model, focusing on the SO. The three formulations simulate different geographical distributions of DFe concentrations in sea ice. Iron in sea ice remains largely uncertain due to the limited number of spatial and seasonal observations, poorly constrained Fe sources and sinks, and significant uncertainties in simulated sea ice and hydrography. Despite these differences, the fertilization effect by sea ice on phytoplankton photosynthesis is qualitatively similar regardless of the formulation considered. Iron incorporation during sea-ice formation, transport, and melt release, common to all formulations, dominates over differences in sea-ice Fe concentrations. Formulating the Fe incorporation rate as proportional to seawater Fe concentrations gives the closest agreement to field observations. With this formulation, sediments work in synergy with Fe transport to fertilize the waters north of the continental shelf. Southern Ocean primary production and export production increase by 5-10% and 9-19%, respectively, when Fe incorporation into sea ice is considered, suggesting a moderate effect of Fe-bearing sea ice on marine productivity. A large part of the SO is under the influence of the cryosphere, which involves several forms of ice: sea ice (pack ice and landfast ice), icebergs, and melting ice shelves. These cryospheric elements reduce light availability at the ocean surface. However, they are also iron laden, which is thought to stimulate productivity and carbon export (

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Section: Should Primary Production and Carbon Export Estimates Be Revsupporting

confidence: 75%

Section: Discussionmentioning

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Iron Incorporation From Seawater Into Antarctic Sea Ice: A Model Study

Person

Vancoppenolle

Aumont

2020

Global Biogeochemical Cycles

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“…Duprat et al 7 , recently suggested, using satellite-derived chlorophyll data, that icebergs drive >20% of Southern Ocean particulate organic carbon export (POC). This is supported by one model estimate of 30% for Antarctic runoff and icebergs 17 , yet other estimates of iceberg fertilization vary widely and are in some cases significantly smaller 8,9,18,19 . Similarly, there is disagreement about whether iceberg fertilization is more, or less, efficient as iceberg size increases 7,8 .…”

Section: Introductionmentioning

confidence: 75%

Highly variable iron content modulates iceberg-ocean fertilisation and potential carbon export

et al. 2019

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Marine phytoplankton growth at high latitudes is extensively limited by iron availability. Icebergs are a vector transporting the bioessential micronutrient iron into polar oceans. Therefore, increasing iceberg fluxes due to global warming have the potential to increase marine productivity and carbon export, creating a negative climate feedback. However, the magnitude of the iceberg iron flux, the subsequent fertilization effect and the resultant carbon export have not been quantified. Using a global analysis of iceberg samples, we reveal that iceberg iron concentrations vary over 6 orders of magnitude. Our results demonstrate that, whilst icebergs are the largest source of iron to the polar oceans, the heterogeneous iron distribution within ice moderates iron delivery to offshore waters and likely also affects the subsequent ocean iron enrichment. Future marine productivity may therefore be not only sensitive to increasing total iceberg fluxes, but also to changing iceberg properties, internal sediment distribution and melt dynamics.

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Antarctic ecosystem responses following ice‐shelf collapse and iceberg calving: Science review and future research

Ingels

Aronson

Smith

et al. 2020

WIREs Climate Change

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The calving of A‐68, the 5,800‐km2, 1‐trillion‐ton iceberg shed from the Larsen C Ice Shelf in July 2017, is one of over 10 significant ice‐shelf loss events in the past few decades resulting from rapid warming around the Antarctic Peninsula. The rapid thinning, retreat, and collapse of ice shelves along the Antarctic Peninsula are harbingers of warming effects around the entire continent. Ice shelves cover more than 1.5 million km2 and fringe 75% of Antarctica's coastline, delineating the primary connections between the Antarctic continent, the continental ice, and the Southern Ocean. Changes in Antarctic ice shelves bring dramatic and large‐scale modifications to Southern Ocean ecosystems and continental ice movements, with global‐scale implications. The thinning and rate of future ice‐shelf demise is notoriously unpredictable, but models suggest increased shelf‐melt and calving will become more common. To date, little is known about sub‐ice‐shelf ecosystems, and our understanding of ecosystem change following collapse and calving is predominantly based on responsive science once collapses have occurred. In this review, we outline what is known about (a) ice‐shelf melt, volume loss, retreat, and calving, (b) ice‐shelf‐associated ecosystems through sub‐ice, sediment‐core, and pre‐collapse and post‐collapse studies, and (c) ecological responses in pelagic, sympagic, and benthic ecosystems. We then discuss major knowledge gaps and how science might address these gaps. This article is categorized under: Climate, Ecology, and Conservation > Modeling Species and Community Interactions

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Sensitivity of ocean biogeochemistry to the iron supply from the Antarctic Ice Sheet explored with a biogeochemical model

Cited by 26 publications

References 105 publications

Iron Incorporation From Seawater Into Antarctic Sea Ice: A Model Study

Iron Incorporation From Seawater Into Antarctic Sea Ice: A Model Study

Highly variable iron content modulates iceberg-ocean fertilisation and potential carbon export

Antarctic ecosystem responses following ice‐shelf collapse and iceberg calving: Science review and future research

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