Nadine Steiger

Understanding ocean physical connectivity is essential for characterizing and predicting transport patterns, which in turn play a fundamental role in several marine processes. Here, we present an analysis of 30 years of surface water connectivity for the Bay of Biscay, derived from backward Lagrangian particle simulations driven by hourly high-resolution surface velocity reanalysis fields. The Lagrangian simulations are used to characterize transport pathways within and between key subregions across integration times of 7, 30, and 90 days, thereby capturing connectivity from weekly to seasonal scales. Results show that the obtained seasonal cycle of connectivity reflects the seasonal variability of regional ocean circulation: i) The northward transport along the shelf by the Iberian–Poleward Current, ii) the presence of transport barriers along the continental slope, and iii) the enhanced cross-shelf transport from the Spanish shelf during spring and from the French shelf during summer. Regional maps of particle origins and transit times reveal areas of strong isolation along the French coast and zones of intensive mixing at the French Spanish border. While interannual variability is evident, the simulations also indicate a slight but significant long-term decrease in transport from the Spanish to the French shelf. Overall, these results provide an overview of the main pathways of transport and retention within the Bay of Biscay at different time scales, offering insights into its potential role in different key ocean processes such as marine litter or plankton dispersal, genetic exchange, and ecosystem functioning.

Understanding ocean physical connectivity is essential for characterizing and predicting transport patterns, which in turn play a fundamental role in several marine processes. Here, we present an analysis of 30 years of surface water connectivity for the Bay of Biscay, derived from backward Lagrangian particle simulations driven by hourly high-resolution surface velocity reanalysis fields. The Lagrangian simulations are used to characterize transport pathways within and between key subregions across integration times of 7, 30, and 90 days, thereby capturing connectivity from weekly to seasonal scales. Results show that the obtained seasonal cycle of connectivity reflects the seasonal variability of regional ocean circulation: i) The northward transport along the shelf by the Iberian–Poleward Current, ii) the presence of transport barriers along the continental slope, and iii) the enhanced cross-shelf transport from the Spanish shelf during spring and from the French shelf during summer. Regional maps of particle origins and transit times reveal areas of strong isolation along the French coast and zones of intensive mixing at the French Spanish border. While interannual variability is evident, the simulations also indicate a slight but significant long-term decrease in transport from the Spanish to the French shelf. Overall, these results provide an overview of the main pathways of transport and retention within the Bay of Biscay at different time scales, offering insights into its potential role in different key ocean processes such as marine litter or plankton dispersal, genetic exchange, and ecosystem functioning.

Understanding ocean physical connectivity is essential for characterizing and predicting transport patterns, which in turn play a fundamental role in several marine processes. Here, we present an analysis of 30 years of surface water connectivity for the Bay of Biscay, derived from backward Lagrangian particle simulations driven by hourly high-resolution surface velocity reanalysis fields. The Lagrangian simulations are used to characterize transport pathways within and between key subregions across integration times of 7, 30, and 90 days, thereby capturing connectivity from weekly to seasonal scales. Results show that the obtained seasonal cycle of connectivity reflects the seasonal variability of regional ocean circulation: i) The northward transport along the shelf by the Iberian–Poleward Current, ii) the presence of transport barriers along the continental slope, and iii) the enhanced cross-shelf transport from the Spanish shelf during spring and from the French shelf during summer. Regional maps of particle origins and transit times reveal areas of strong isolation along the French coast and zones of intensive mixing at the French Spanish border. While interannual variability is evident, the simulations also indicate a slight but significant long-term decrease in transport from the Spanish to the French shelf. Overall, these results provide an overview of the main pathways of transport and retention within the Bay of Biscay at different time scales, offering insights into its potential role in different key ocean processes such as marine litter or plankton dispersal, genetic exchange, and ecosystem functioning.

Understanding ocean physical connectivity is essential for characterizing and predicting transport patterns, which in turn play a fundamental role in several marine processes. Here, we present an analysis of 30 years of surface water connectivity for the Bay of Biscay, derived from backward Lagrangian particle simulations driven by hourly high-resolution surface velocity reanalysis fields. The Lagrangian simulations are used to characterize transport pathways within and between key subregions across integration times of 7, 30, and 90 days, thereby capturing connectivity from weekly to seasonal scales. Results show that the obtained seasonal cycle of connectivity reflects the seasonal variability of regional ocean circulation: i) The northward transport along the shelf by the Iberian–Poleward Current, ii) the presence of transport barriers along the continental slope, and iii) the enhanced cross-shelf transport from the Spanish shelf during spring and from the French shelf during summer. Regional maps of particle origins and transit times reveal areas of strong isolation along the French coast and zones of intensive mixing at the French Spanish border. While interannual variability is evident, the simulations also indicate a slight but significant long-term decrease in transport from the Spanish to the French shelf. Overall, these results provide an overview of the main pathways of transport and retention within the Bay of Biscay at different time scales, offering insights into its potential role in different key ocean processes such as marine litter or plankton dispersal, genetic exchange, and ecosystem functioning.

Open-ocean polynyas, areas with little or no sea ice, reappeared extensively in 2016 and 2017 over the Maud Rise in the Weddell Sea after a 40-year hiatus, raising a series of unresolved questions about the atmosphere-ice-ocean interactions in the Antarctic region. These major polynyas significantly influence moisture and heat exchange between the atmosphere and the ocean, impacting both regional and global climate dynamics, as well as ecosystem functioning and biogeochemical processes. Notably, they may play a crucial role in contributing to the formation of Antarctic Bottom Water and influencing global ocean circulation. In this Review, we synthesize current knowledge on the drivers and impacts of Weddell Sea polynyas. Recent occurrences have been linked to factors such as a strengthening Weddell Gyre, a negative Southern Annular Mode, extreme local atmospheric conditions (atmospheric rivers and cyclones), and subsurface ocean heat buildup which acts as a preconditioning factor. The associated deep ocean convection from these polynyas can enhance air-sea gas exchange and trigger earlier phytoplankton blooms due to the influx of iron and nutrients from the deep ocean. While advancements in observation and modeling techniques have significantly improved our understanding of polynyas, substantial uncertainties remain regarding their interaction with recent Antarctic sea ice loss, their sensitivity to ocean mixing schemes, their excessive size or frequency in climate simulations, and future projections. Therefore, future research should focus on developing comprehensive four-dimensional regional observatories and targeted, data-constrained coupled models that accurately capture atmosphere-ice-ocean interactions across various timescales.

Phytoplankton blooms above the seamount Maud Rise in the Antarctic Ocean have been reported but their emerging mechanisms and their importance for the wider Southern Ocean are not well known. We use satellite data spanning over the last two decades and in-situ data collected from a ship, an underwater glider and Biogeochemical-Argo profiling floats to understand the processes involved in the formation of Maud Rise phytoplankton blooms. We find that the seamount generates upwelling of warm deep water that transports heat, and likely dissolved iron, to the surface via diapycnal mixing. This creates a recurring annular structure of chlorophyll concentration (or chlorophyll halo) in correspondence with the previously observed warm water and sea ice halo over Maud Rise. The in-situ observations reveal integrated chlorophyll-a concentrations of up to 100 mg·m ⁻² , which suggests exceptionally high phytoplankton biomass within the Southern Ocean, thus making the seamount a regional phytoplankton hotspot.

Open-ocean polynyas, openings in the sea ice, reappeared extensively in 2016 and 2017 over the Maud Rise in the Weddell Sea after a 40-year hiatus, raising a series of unresolved questions about the atmosphere-ice-ocean interactions in the Antarctic region. These major polynyas significantly influence moisture and heat exchange between the atmosphere and ocean, impacting both regional and global climate dynamics, as well as ecosystem functioning and biogeochemical processes. Notably, they could play a crucial role in contributing to the formation of Antarctic Bottom Water and influencing global ocean circulation. In this Review, we synthesize current knowledge on the drivers and impacts of Weddell Sea polynyas. Recent occurrences have been linked to factors such as a strengthening Weddell Gyre, a negative Southern Annular Mode, extreme local atmospheric conditions (atmosphere river and cyclones), and subsurface ocean heat buildup which acts as a preconditioning factor. The associated deep ocean convection from these polynyas can enhance air-sea gas exchange and trigger earlier phytoplankton blooms due to the influx of iron and nutrients from the deep ocean. While advancements in observation and modeling techniques have significantly improved our understanding of polynyas, substantial uncertainties remain regarding their interaction with recent Antarctic sea ice loss, their sensitivity to ocean mixing schemes and their excessive size or frequency in climate simulations, and future projections. Therefore, future research should focus on developing comprehensive four-dimensional regional observatories and targeted, assimilated coupled models that accurately capture atmosphere-ice-ocean interactions across various timescales.

Open-ocean polynyas, openings in the sea ice, reappeared extensively in 2016 and 2017 over the Maud Rise in the Weddell Sea after a 40-year hiatus, raising a series of unresolved questions about the atmosphere-ice-ocean interactions in the Antarctic region. These major polynyas significantly influence moisture and heat exchange between the atmosphere and ocean, impacting both regional and global climate dynamics, as well as ecosystem functioning and biogeochemical processes. Notably, they could play a crucial role in contributing to the formation of Antarctic Bottom Water and influencing global ocean circulation. In this Review, we synthesize current knowledge on the drivers and impacts of Weddell Sea polynyas. Recent occurrences have been linked to factors such as a strengthening Weddell Gyre, a negative Southern Annular Mode, extreme local atmospheric conditions (atmosphere river and cyclones), and subsurface ocean heat buildup which acts as a preconditioning factor. The associated deep ocean convection from these polynyas can enhance air-sea gas exchange and trigger earlier phytoplankton blooms due to the influx of iron and nutrients from the deep ocean. While advancements in observation and modeling techniques have significantly improved our understanding of polynyas, substantial uncertainties remain regarding their interaction with recent Antarctic sea ice loss, their sensitivity to ocean mixing schemes and their excessive size or frequency in climate simulations, and future projections. Therefore, future research should focus on developing comprehensive four-dimensional regional observatories and targeted, assimilated coupled models that accurately capture atmosphere-ice-ocean interactions across various timescales.

Open-ocean polynyas, openings in the sea ice, reappeared extensively in 2016 and 2017 over the Maud Rise in the Weddell Sea after a 40-year hiatus, raising a series of unresolved questions about the atmosphere-ice-ocean interactions in the Antarctic region. These major polynyas significantly influence moisture and heat exchange between the atmosphere and ocean, impacting both regional and global climate dynamics, as well as ecosystem functioning and biogeochemical processes. Notably, they could play a crucial role in contributing to the formation of Antarctic Bottom Water and influencing global ocean circulation. In this Review, we synthesize current knowledge on the drivers and impacts of Weddell Sea polynyas. Recent occurrences have been linked to factors such as a strengthening Weddell Gyre, a negative Southern Annular Mode, extreme local atmospheric conditions (atmosphere river and cyclones), and subsurface ocean heat buildup which acts as a preconditioning factor. The associated deep ocean convection from these polynyas can enhance air-sea gas exchange and trigger earlier phytoplankton blooms due to the influx of iron and nutrients from the deep ocean. While advancements in observation and modeling techniques have significantly improved our understanding of polynyas, substantial uncertainties remain regarding their interaction with recent Antarctic sea ice loss, their sensitivity to ocean mixing schemes and their excessive size or frequency in climate simulations, and future projections. Therefore, future research should focus on developing comprehensive four-dimensional regional observatories and targeted, assimilated coupled models that accurately capture atmosphere-ice-ocean interactions across various timescales.

Open-ocean polynyas, openings in the sea ice, reappeared extensively in 2016 and 2017 over the Maud Rise in the Weddell Sea after a 40-year hiatus, raising a series of unresolved questions about the atmosphere-ice-ocean interactions in the Antarctic region. These major polynyas significantly influence moisture and heat exchange between the atmosphere and ocean, impacting both regional and global climate dynamics, as well as ecosystem functioning and biogeochemical processes. Notably, they could play a crucial role in contributing to the formation of Antarctic Bottom Water and influencing global ocean circulation. In this Review, we synthesize current knowledge on the drivers and impacts of Weddell Sea polynyas. Recent occurrences have been linked to factors such as a strengthening Weddell Gyre, a negative Southern Annular Mode, extreme local atmospheric conditions (atmosphere river and cyclones), and subsurface ocean heat buildup which acts as a preconditioning factor. The associated deep ocean convection from these polynyas can enhance air-sea gas exchange and trigger earlier phytoplankton blooms due to the influx of iron and nutrients from the deep ocean. While advancements in observation and modeling techniques have significantly improved our understanding of polynyas, substantial uncertainties remain regarding their interaction with recent Antarctic sea ice loss, their sensitivity to ocean mixing schemes and their excessive size or frequency in climate simulations, and future projections. Therefore, future research should focus on developing comprehensive four-dimensional regional observatories and targeted, assimilated coupled models that accurately capture atmosphere-ice-ocean interactions across various timescales.