Glacial and Hydrothermal Sources of Dissolved Iron (II) in Southern Ocean Waters Surrounding Heard and McDonald Islands

Holmes, Thomas M.; Wuttig, Kathrin; Chase, Zanna; Schallenberg, Christina; Merwe, Pier van der; Townsend, Ashley T.

doi:10.1029/2020jc016286

Cited by 7 publications

(4 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Ligands in deep waters are typically saturated with Fe due to particle remineralisation (Hassler et al, 2020b;Gerringa et al, 2015) and therefore are unlikely to act as a source of L' to surface waters. In addition, the FeL c o n t e n t o f L C D W m a y b e f u r t h e r e n h a n c e d b y hydrothermalism and lateral advection within the Antarctic Circumpolar Current (Holmes et al, 2020;Janssen et al, 2020;Schine et al, 2021). Therefore, FeL entrained by LCDW which is upwelled onto the Mertz continental shelf may provide a possible explanation for the presence of strong binding ligands in this region.…”

Section: Deeper Watersmentioning

confidence: 99%

Identifying potential sources of iron-binding ligands in coastal Antarctic environments and the wider Southern Ocean

et al. 2022

Self Cite

View full text Add to dashboard Cite

The availability of iron (Fe) to marine microbial communities is enhanced through complexation by ligands. In Fe limited environments, measuring the distribution and identifying the likely sources of ligands is therefore central to understanding the drivers of marine productivity. Antarctic coastal marine environments support highly productive ecosystems and are influenced by numerous sources of ligands, the magnitude of which varies both spatially and seasonally. Using competitive ligand exchange adsorptive cathodic stripping voltammetry (CLE-AdCSV) with 2-(2-thiazolylazo)-p-cresol (TAC) as a competing artificial ligand, this study investigates Fe-binding ligands (FeL) across the continental shelf break in the Mertz Glacier Region, East Antarctica (64 - 67°S; 138 - 154°E) during austral summer of 2019. The average FeL concentration was 0.86 ± 0.5 nM Eq Fe, with strong conditional stability constants (Log KFeL) averaging 23.1 ± 1.0. The strongest binding ligands were observed in modified circumpolar deep water (CDW), thought to be linked to bacterial Fe remineralisation and potential siderophore release. High proportions of excess unbound ligands (L’) were observed in surface waters, as a result of phytoplankton Fe uptake in the mixed layer and euphotic zone. However, FeL and L’ concentrations were greater at depth, suggesting ligands were supplied with dissolved Fe from upwelled CDW and particle remineralisation in benthic nepheloid layers over the shelf. Recent sea-ice melt appeared to support bacterial production in areas where Fe and ligands were exhausted. This study is included within our newly compiled Southern Ocean Ligand (SOLt) Collection, a database of publicly available Fe-binding ligand surveys performed south of 50°S. A review of the SOLt Collection brings attention to the paucity of ligand data collected along the East Antarctic coast and the difficulties in pinpointing sources of Fe and ligands in coastal environments. Elucidating poorly understood ligand sources is essential to predicting future Fe availability for microbial populations under rapid environmental change.

show abstract

Section: Deeper Watersmentioning

confidence: 99%

Identifying potential sources of iron-binding ligands in coastal Antarctic environments and the wider Southern Ocean

et al. 2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…Marine ecosystems in fjords support large colonies of higher predators such as sea birds and marine mammals (Ward, 1989; Wȩsławski et al., 2000), while open ocean and on‐shelf phytoplankton blooms may also rely on the transport of nutrients circulated by nearby fjords from upwelling and terrestrial sources via glacial runoff (Holmes et al., 2019; Wȩsławski et al., 2000). Fjords are also important spawning grounds for fish (Everson et al., 2001).…”

Section: Introductionmentioning

confidence: 99%

Oceanographic Variability in Cumberland Bay, South Georgia, and Its Implications for Glacier Retreat

Zanker,

Young,

Holland

et al. 2024

JGR Oceans

View full text Add to dashboard Cite

South Georgia is a heavily glaciated sub‐Antarctic island in the Southern Ocean. Cumberland Bay is the largest fjord on the island, split into two arms, each with a large marine‐terminating glacier at the head. Although these glaciers have shown markedly different retreat rates over the past century, the underlying drivers of such differential retreat are not yet understood. This study uses observations and a new high‐resolution oceanographic model to characterize oceanographic variability in Cumberland Bay and to explore its influence on glacier retreat. While observations indicate a strong seasonal cycle in temperature and salinity, they reveal no clear hydrographic differences that could explain the differential glacier retreat. Model simulations suggest the subglacial outflow plume dynamics and fjord circulation are sensitive to the bathymetry adjacent to the glacier, though this does not provide persuasive reasoning for the asymmetric glacier retreat. The addition of a postulated shallow inner sill in one fjord arm, however, significantly changes the water properties in the resultant inner basin by blocking the intrusion of colder, higher salinity waters at depth. This increase in temperature could significantly increase submarine melting, which is proposed as a possible contribution to the different rates of glacier retreat observed in the two fjord arms. This study represents the first detailed description of the oceanographic variability of a sub‐Antarctic island fjord, highlighting the sensitivity of fjord oceanography to bathymetry. Notably, in fjords systems where temperature decreases with depth, the presence of a shallow sill has the potential to accelerate glacier retreat.

show abstract

“…Marine ecosystems in fjords support large colonies of higher predators such as sea birds and marine mammals (Ward, 1989;We ¸sławski et al, 2000), while open ocean and on-shelf phytoplankton blooms may also rely on the transport of nutrients circulated by nearby fjords from upwelling and terrestrial sources via glacial runoff (Holmes et al, 2019;We ¸sławski et al, 2000). Fjords are also important spawning grounds for fish (Everson et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

Oceanographic variability in Cumberland Bay, South Georgia, and its implications for glacier retreat

Zanker,

Young,

Holland

et al. 2023

Preprint

View full text Add to dashboard Cite

South Georgia is a heavily glaciated sub-Antarctic island in the Southern Ocean. Cumberland Bay is the largest fjord on the island, split into two arms, each with a large marine-terminating glacier at the head. Although these glaciers have shown markedly different retreat rates over the past century, the underlying drivers of such differential retreat are not yet understood. This study uses observations and a new high-resolution oceanographic model to characterize oceanographic variability in Cumberland Bay and to explore its influence on glacier retreat. While observations indicate a strong seasonal cycle in temperature and salinity, they reveal no clear hydrographic differences that could explain the differential glacier retreat. Model simulations suggest the subglacial outflow plume dynamics and fjord circulation are sensitive to the bathymetry adjacent to the glacier, though this does not provide persuasive reasoning for the asymmetric glacier retreat. The addition of a postulated shallow inner sill in one fjord arm, however, significantly changes the water properties in the resultant inner basin by blocking the intrusion of colder, higher salinity waters at depth. This increase in temperature could significantly increase submarine melting, which is proposed as a possible contribution to the different rates of glacier retreat observed in the two fjord arms. This study represents the first detailed description of the oceanographic variability of a sub-Antarctic island fjord, highlighting the sensitivity of fjord oceanography to bathymetry. Notably, in fjords systems where temperature decreases with depth, the presence of a shallow sill has the potential to accelerate glacier retreat.

show abstract

Glacial and Hydrothermal Sources of Dissolved Iron (II) in Southern Ocean Waters Surrounding Heard and McDonald Islands

Cited by 7 publications

References 49 publications

Identifying potential sources of iron-binding ligands in coastal Antarctic environments and the wider Southern Ocean

Identifying potential sources of iron-binding ligands in coastal Antarctic environments and the wider Southern Ocean

Oceanographic Variability in Cumberland Bay, South Georgia, and Its Implications for Glacier Retreat

Oceanographic variability in Cumberland Bay, South Georgia, and its implications for glacier retreat

Contact Info

Product

Resources

About