Collaborative Research: RAPID: Linking Sea Ice and Biogeochemistry in the Weddell Sea Marginal Ice Zone: Physical Structure, Meltwater Chemistry, and Biological Gradients

Sea ice is a key feature of the Southern Ocean that shapes the physical structure of the water column and regulates phytoplankton community dynamics and primary production. Phytoplankton are the base of the food chain, and the type of phytoplankton present, along with their overall productivity, impact the abundance of zooplankton and larger animals. Phytoplankton communities and production are also an important link for carbon export to the deep sea, a critical service provided by the Southern Ocean. However, sea ice extent and duration are decreasing in the Antarctic Peninsula region of the Southern Ocean, potentially affecting carbon export. This project aims to evaluate physical and chemical characteristics of sea ice in the Weddell Sea near Seymour Island and quantify effects of melting sea ice on phytoplankton and zooplankton growth and carbon export. This work will promote the progress of polar science and allow for better predictions of the ecosystem effects of changing sea ice conditions, such as shifts in krill abundance and its ability to support macrofauna and fisheries, and changes in carbon export. This project will further support the training of new undergraduate and graduate polar scientists and confer key transferable skills, such as data analysis and visualization and science communication. This project brings together an interdisciplinary team of physical, chemical, and biological oceanographers to comprehensively evaluate characteristics of sea ice in the Weddell Sea near Seymour Island and parse the effects of sea ice melt on biological systems and carbon export through a dual approach involving environmental observations and replicated factorial incubation experiments. Snow pits and ice cores will be used to characterize physical (snow density, hardness, temperature, and grain size and shape) and chemical parameters (δ¹⁸O, nitrate + nitrite, and Fe concentrations) of sea ice. Physical characteristics will be used to better calibrate satellite observations and improve future remote sensing. Chemical parameters will help determine how much meltwater is derived from sea ice and will further constrain the impact of sea ice melt on macro and micronutrient availability in the surface mixed layer. The spatial evolution of sea ice melt across the Weddell Sea continental shelf will be quantified through conductivity, temperature, and depth transects extending from Seymour Island to the shelf break. These transects will also include seawater sampling, zooplankton tows, and deployment of an in situ particle imager to characterize microbial, phytoplankton, and zooplankton communities and calculate particle flux. Experimental incubations will constrain the impacts of changing salinity, light, and nutrient regimes associated with ice melt on biological productivity, particle formation, and export potential. Broader Impacts include training an undergraduate and a graduate student and a synthesis workshop to share results and build a network of scientists interested in the impacts of ice-melt on polar systems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.