Search for: All records

Abstract High‐resolution glider sampling in the southwestern Ross Sea revealed an extensive phytoplankton bloom in austral summer 2022–2023 that persisted for over one month and extended through the upper 100 m of the water column. The temporal mean euphotic‐zone chlorophyll concentration was 20.38.5 , six to nine times higher than average summer Ross Sea concentrations. The bloom was likely initially dominated byPhaeocystis, favored over diatoms due to low light and high iron availability. Our observations are consistent with an ice‐edge bloom likely fueled by iron supply and enhanced stratification from late sea‐ice melt during an anomalously high ice‐covered summer. Photoacclimation to particularly low light conditions might have enhanced Chl‐a fluorescence. In the Ross Sea, the most productive region in the Southern Ocean, understanding the drivers of this extreme bloom is crucial for predicting potential impacts of the changing climate on primary production rates and carbon sequestration. 

Abstract The West Antarctic Ice Sheet is experiencing rapid thinning of its floating ice shelves, largely attributed to oceanic basal melt. Numerical models suggest that the Bellingshausen Sea has a key role in setting water properties in the Amundsen Sea and further downstream. Yet, observations confirming these pathways of volume and tracer exchange between coast and shelf break and their impact on inter‐sea exchange remain sparse. Here we analyze the circulation and distribution of glacial meltwater at the boundary between the Bellingshausen Sea and the Amundsen Sea using a combination of glider observations from January 2020 and hydrographic data from instrumented seals. Meltwater distributions over previously unmapped western regions of the continental shelf and slope reveal two distinct meltwater cores with different optical backscatter properties. At Belgica Trough, a subsurface meltwater peak is linked with hydrographic properties from Venable Ice Shelf. West of Belgica Trough, the vertical structure of meltwater concentration changes, with peak values occurring at greater depths and denser isopycnals. Hydrographic analysis suggests that the western (deep) meltwater core is supplied from the eastern part of Abbot Ice Shelf, and is exported to the shelf break via a previously‐overlooked bathymetric trough (here named Seal Trough). Hydrographic sections constructed from seal data reveal that the Antarctic Coastal Current extends west past Belgica Trough, delivering meltwater to the Amundsen Sea. Each of these circulation elements has distinct dynamical implications for the evolution of ice shelves and water masses both locally and downstream, in the Amundsen Sea and beyond.