Margaret Lindeman

Antarctic open‐ocean polynyas trigger vigorous wintertime convection, influencing ocean circulation and atmospheric processes. In the Weddell Sea, interaction between the Weddell Gyre and the Maud Rise seamount generates a Taylor column that favors polynya formation. However, owing to limited observations, the dynamics of such polynya formation remain partially understood, particularly the long‐term preconditioning that sets the stage for polynya occurrence. We use glider observations from late austral summer 2022 to investigate the role of mixing in preconditioning, focusing on the interior layer below the pycnocline, which stores heat that melts sea ice and regulates deep convection. We show that multiple mixing processes contribute to the preconditioning. Widespread interleaving structures along the northwestern flank of Maud Rise are identified, indicating that warm, salty water intrudes into the Taylor column along isopycnals. This intrusion is likely driven by lateral shear and eddies, both arising from the flank's anticyclonic circulation. Moreover, eddy shedding, cabbeling, and diffusive convection jointly enhance lateral homogenization and destratification of the Taylor column interior below the pycnocline. Using the large eddy method and a triple decomposition of the tracer variance equation, we calculate snapshot‐based along‐isopycnal heat and salt transports from the Rise flanks into the Taylor column as ∼0.18 TW and ∼, respectively. At these rates, idealized estimates suggest that polynya‐favorable conditions could develop within 2–6 years of the observations. Our results highlight the role of mixing in polynya formation and the need to realistically represent these processes in climate‐scale ocean models.

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.

As global atmosphere and ocean temperatures rise and the Greenland Ice Sheet loses mass, the glacial fjords of Kalaallit Nunaat/Greenland play an increasingly critical role in our climate system. Fjords are pathways for freshwater from ice melt to reach the ocean and for deep, warm, nutrient-rich ocean waters to reach marine–terminating glaciers, supporting abundant local ecosystems that Greenlanders rely upon. Research in Greenland fjords has become more interdisciplinary and more observations are being collected in fjords than in previous decades. However, there are few long-term (> 10 years) datasets available for single fjords. Additionally, observations in fjords are often spatially and temporally disjointed, utilize multiple observing tools, and datasets are rarely provided in formats that are easily used across disciplines or audiences. We address this issue by providing standardized, gridded summer season hydrographic sections for Sermilik Fjord in Southeast Greenland, from 2009–2023. Gridded data facilitate the analysis of coherent spatial patterns across the fjord domain, and are a more accessible and intuitive data product compared to discrete profiles. We combined ship-based conductivity, temperature, and depth (CTD) profiles with helicopter-deployed eXpendable CTD (XCTD) profiles from the ice mélange region to create objectively mapped (or optimally interpolated) along-fjord sections of conservative temperature and absolute salinity. From the gridded data, we derived a summer season climatological mean and root mean square deviation, summarizing typical fjord conditions and highlighting regions of variability. This information can be used by model and laboratory studies, biological and ecosystem studies in the fjord, and provides context for interpreting previous work. Additionally, this method can be applied to datasets from other fjords helping to facilitate fjord intercomparison studies. The gridded data and climatological products are available in netCDF format at https://doi.org/10.18739/A28G8FK6D (Roth et al., 2025a). All original profile observations, with unique DOIs for each field campaign, are available through the Sermilik Fjord Hydrography Data Portal (https://arcticdata.io/catalog/portals/sermilik, last access: 7 November 2025) hosted by the Arctic Data Center (Straneo et al., 2025). The code used has also been made available to facilitate continued updates to the Sermilik Fjord gridded section dataset and applications to other fjord systems.

As global atmosphere and ocean temperatures rise and the Greenland Ice Sheet loses mass, the glacial fjords of Kalallit Nunaat/Greenland play an increasingly critical role in our climate system. Fjords are pathways for freshwater from ice melt to reach the ocean and for deep, warm, nutrient–rich ocean waters to reach marine–terminating glaciers, supporting abundant local ecosystems that Greenlanders rely upon. Research in Greenland fjords has become more interdisciplinary and more observations are being collected in fjords than in previous decades. However, there are few long–term (> 10 years) datasets available for single fjords. Additionally, observations in fjords in general are often spatially and temporally disjointed, utilize multiple observing tools, and are rarely provided in formats that are easily used across disciplines or audiences. We address this issue by providing standardized, gridded summer season hydrographic sections for Sermilik Fjord in Southeast Greenland, from 2009–2023. Gridded data facilitate the analysis of coherent spatial patterns across the fjord domain, and are a more accessible and intuitive data product compared to discrete profiles. We combined ship–based conductivity, temperature, and depth (CTD) profiles with helicopter–deployed eXpendable CTD (XCTD) profiles from the ice mélange region to create objectively mapped (or optimally interpolated) along–fjord sections of conservative temperature and absolute salinity. From the gridded data, we derived a summer season climatological mean and root mean square deviation, summarizing typical fjord conditions and highlighting regions of variability. This information can be used by model and laboratory studies, fjord intercomparison studies, biological and ecosystem studies in the fjord, and provides context for interpreting previous work. All original profile observations, gridded data, and climatological products are publicly available in netCDF format at Arctic Data Center and GitHub. The code used has also been made available to facilitate continued updates to the Sermilik Fjord gridded data product and applications to other fjord systems.

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.

Greenland’s glacial fjords are the sites of climatically important exchanges of heat, freshwater, and nutrients between the North Atlantic Ocean and the Greenland ice sheet, as well as hosting productive ecosystems integral to local communities. Though both glacial inputs and ocean exchanges are modulated by seasonal and interannual variability, observational studies of the complex interactions that take place in these fjords often necessarily rely on data from a single field campaign, amounting to a summer snapshot of fjord conditions.We have sustained a long-term monitoring program in Sermilik Fjord, a major glacial fjord in southeast Greenland, since 2008, collecting ocean temperature and salinity profiles almost annually, supplemented by ongoing mooring records that cover the full period from 2008-2023. This exceptional data set, at times augmented by the collection of complementary data such as velocity measurements and noble gas, nutrient, and dissolved oxygen concentrations, has given us a more robust understanding of the fjord circulation and water mass transformations. This in turn can be leveraged to help us address a range of questions within this complex system.We apply this foundational knowledge of Sermilik Fjord to interpret the cycling of mercury in the fjord from full water column measurements of mercury concentrations from summer 2021. We use a water mass analysis to show that the exported glacially-modified waters are depleted in inorganic mercury (HgII) relative to ambient ocean waters. We propose that sediments initially suspended in glacier meltwaters scavenge particle-reactive HgII and are subsequently buried, making the fjord a net sink of oceanic mercury.