delphine lannuzel

Enhanced Iron Flux to Antarctic Sea Ice via Dust Deposition From Ice‐Free Coastal Areas

Publisher: American Geophysical Union (AGU)

Date: 12-2019

DOI: 10.1029/2019JC015221

Nutrient Distribution in East Antarctic Summer Sea Ice: A Potential Iron Contribution From Glacial Basal Melt

Publisher: American Geophysical Union (AGU)

Date: 27-11-2020

DOI: 10.1029/2020JC016130

Abstract: Antarctic sea ice can incorporate high levels of iron (Fe) during its formation and has been suggested as an important source of this essential micronutrient to Southern Ocean surface waters during the melt season. Over the last decade, a limited number of studies have quantified the Fe pool in Antarctic sea ice, with a focus on late winter and spring. Here we study the distribution of operationally defined dissolved and particulate Fe from nine sites s led between Wilkes Land and King George V Land during austral summer 2016/2017. Results point toward a net heterotrophic sea‐ice community, consistent with the observed nitrate limitation ( μM). We postulate that the recycling of the high particulate Fe pool in summer sea ice supplies sufficient (∼3 nM) levels of dissolved Fe to sustain ice algal growth. The remineralization of particulate Fe is likely favored by high concentrations of exopolysaccharides (113–16,290 μg xeq L −1 ) which can serve as a hotspot for bacterial activity. Finally, results indicate a potential relationship between glacial meltwater discharged from the Moscow University Ice Shelf and the occurrence of Fe‐rich (∼4.3 μM) platelet ice in its vicinity. As climate change is expected to result in enhanced Fe‐rich glacial discharge and changes in summer sea‐ice extent and quality, the processes influencing Fe distribution in sea ice that persists into summer need to be better constrained.

Physical and Biogeochemical Properties of Rotten East Antarctic Summer Sea Ice

Publisher: American Geophysical Union (AGU)

Date: 02-2023

DOI: 10.1029/2022JC018875

Abstract: Sea ice forms a barrier to the exchange of energy, gases, moisture and particles between the ocean and atmosphere around Antarctica. Ice temperature, salinity and the composition of ice crystals determine whether a particular slab of sea ice is habitable for microorganisms and permeable to exchanges between the ocean and atmosphere, allowing, for ex le, carbon dioxide (CO 2 ) from the atmosphere to be absorbed or outgassed by the ocean. Spring sea ice can have high concentrations of algae and absorb atmospheric CO 2 . In the summer of 2016–2017 off East Antarctica, we found decayed and porous granular ice layers in the interior of the ice column, which showed high algal pigment concentrations. The maximum chlorophyll a observed in the interior of the ice column was 67.7 μg/L in a 24% porous granular ice layer between 0.8 and 0.9 m depth in 1.7 m thick ice, compared to an overall mean sea‐ice chlorophyll a (± one standard deviation) of 13.5 ± 21.8 μg/L. We also found extensive surface melting, with instances of snow meltwater apparently percolating through the ice, as well as impermeable superimposed ice layers that had refrozen along with melt ponds on top of the ice. With future warming, the structures we describe here could occur earlier and/or become more persistent, meaning that sea ice would be more often characterized by patchy permeability and interior ice algal accumulations.

Circumpolar Deep Water and Shelf Sediments Support Late Summer Microbial Iron Remineralization

Publisher: American Geophysical Union (AGU)

Date: 11-2021

DOI: 10.1029/2020GB006921

Abstract: Despite widespread iron (Fe) limitation in the Southern Ocean, intense phytoplankton blooms are observed around productive coastal regions such as the Mertz Polynya (off George V Land and Adelie Land, East Antarctica 140–155°E). Sources of Fe across coastal East Antarctica vary, with limited data available for late summer months. We investigated the sources of dissolved Fe (dFe .2 μm) at 19 oceanographic stations in the Mertz Glacier Region (64–67°S 138–154°E), between January and March of 2019. Concentrations of dFe ranged from below detection limit (0.03 nM) at the surface, to 0.34 nM above the base of the mixed layer (35 m), reaching 0.59 nM at depth (520 m). Using oceanographic features and trace element ratios (manganese and titanium), we identified Circumpolar Deep Water (CDW) and shelf sediment resuspension in modified CDW as contributors of dFe to the region over this period. Microbial Fe remineralization was evident where nutrient‐rich water met highly oxygenated waters over the continental shelf. Reduced Fe concentrations in the mixed layer and euphotic zones suggested rapid biological uptake prior to s ling. Despite proposals for pelagic Fe recycling by marine animals, preliminary investigations reveal no significant spatial relationship between animal presence and surface ocean Fe concentrations over the study area. Further research is required to identify seasonal changes to Fe supply in coastal areas which will strengthen our understanding of the Fe cycle and its influence on microbial and primary productivity in this globally significant region.

The future of Arctic sea-ice biogeochemistry and ice-associated ecosystems

Publisher: Springer Science and Business Media LLC

Date: 27-10-2020

DOI: 10.1038/S41558-020-00940-4

Polar oceans and sea ice in a changing climate

Publisher: University of California Press

Date: 2023

DOI: 10.1525/ELEMENTA.2023.00056

Antarctic Landfast Sea Ice: A Review of Its Physics, Biogeochemistry and Ecology

Publisher: American Geophysical Union (AGU)

Date: 06-2023

DOI: 10.1029/2022RG000770

Abstract: Antarctic landfast sea ice (fast ice) is stationary sea ice that is attached to the coast, grounded icebergs, ice shelves, or other protrusions on the continental shelf. Fast ice forms in narrow (generally up to 200 km wide) bands, and ranges in thickness from centimeters to tens of meters. In most regions, it forms in autumn, persists through the winter and melts in spring/summer, but can remain throughout the summer in particular locations, becoming multi‐year ice. Despite its relatively limited extent (comprising between about 4% and 13% of overall sea ice), its presence, variability and seasonality are drivers of a wide range of physical, biological and biogeochemical processes, with both local and far‐ranging ramifications for the Earth system. Antarctic fast ice has, until quite recently, been overlooked in studies, likely due to insufficient knowledge of its distribution, leading to its reputation as a “missing piece of the Antarctic puzzle.” This review presents a synthesis of current knowledge of the physical, biogeochemical and biological aspects of fast ice, based on the sub‐domains of: fast ice growth, properties and seasonality remote‐sensing and distribution interactions with the atmosphere and the ocean biogeochemical interactions its role in primary production and fast ice as a habitat for grazers. Finally, we consider the potential state of Antarctic fast ice at the end of the 21st Century, underpinned by Coupled Model Intercomparison Project model projections. This review also gives recommendations for targeted future work to increase our understanding of this critically‐important element of the global cryosphere.

Discovery Early Career Researcher Award - Grant ID: DE120100030

Start Date: 01-2012

End Date: 08-2016

Amount: $375,000.00

Funder: Australian Research Council

ARC Future Fellowships - Grant ID: FT190100688

Start Date: 05-2020

End Date: 09-2024

Amount: $917,463.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP230101368

Start Date: 04-2023

End Date: 04-2026

Amount: $807,639.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP0985361

Start Date: 2009

End Date: 12-2011

Amount: $300,000.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE220100103

Start Date: 07-2022

End Date: 12-2023

Amount: $328,389.00

Funder: Australian Research Council

Linkage Infrastructure, Equipment And Facilities - Grant ID: LE220100089

Start Date: 07-2022

End Date: 06-2023

Amount: $552,086.00

Funder: Australian Research Council

Special Research Initiatives - Grant ID: SR200100008

Start Date: 08-2021

End Date: 12-2027

Amount: $20,000,000.00

Funder: Australian Research Council