Collaborative Research: Polynyas in Coastal Antarctica (PICA): Linking Physical Dynamics to Biological Variability.

Collaborators: Weifeng Zhang (WHOI), Rubao Ji (WHOI), Ted Maksym (WHOI) and Stephanie Jenouvrier (WHOI)

During winter, sea-ice coverage along the Antarctic coast is punctuated by numerous polynyas – isolated openings of tens to hundreds of kilometers wide. These coastal polynyas are hotspots of sea ice production and the primary source regions of the bottom water in the global ocean. They also host high levels of biological activities and are the feeding grounds of Emperor penguins and marine mammals. Polynya features differ dramatically from each other in timing of formation, duration, phytoplankton growth season, and overall biological productivity. Yet, the underlying reasons for differences among them are largely unknown. This project studies the fundamental biophysical processes at a variety of polynyas, examines the connection between the physical environment and the phytoplankton and penguin ecology, and investigates the mechanisms behind polynya variability. The results of this interdisciplinary study will provide a context for interpretation of field measurements in Antarctic coastal polynyas, set a baseline for future polynya studies, and examine how polynya ecosystems may respond to local and large-scale environmental changes. The project will include educational and outreach activities that convey scientific messages to a broad audience. It aims to increase public awareness of the interconnection between large-scale environmental change and Antarctic coastal systems.


The main objectives of this study are to form a comprehensive understanding of the temporal and spatial variability of Antarctic coastal polynyas and the physical controls of polynya ecosystems. The interdisciplinary approach will
1. Establish a coupled modeling system which links the sea ice and ocean conditions to the plankton ecology and penguin population.
2. Combine modeling with data analysis to determine the biophysical influences of individual forcing factors on the timing of polynya phytoplankton bloom and the overall polynya biological productivity.
3. Examine how changing polynya state affects penguin breeding success, adult survival, and population growth.



Effects of Mesoscale Eddies on Three-Dimensional Oil Dispersion: Data Integration, Interpretation and Implications for Oil Spill Models.

Collaborators: Xinfeng Liang (UDel), Robert Weisberg (USF) and Yonggang Liu (USF).

After the Deepwater Horizon Oil Spill, the scientific community immediately realized that a system for tracking the discharged petroleum and associated contaminants, both at the surface and at depth, was needed for effective mitigation efforts. In the past years, largely within the framework of GoMRI, many efforts have been devoted to this, and significant progress has been made in tracking the petroleum via numerical models and satellite remote sensing resources. However, accurate oil tracking remains challenging. Among many oceanic physical processes that affect the dispersal of subsurface materials, mesoscale eddies likely play an essential yet overlooked role. Limited studies in the GoM and other regions of the global ocean show that mesoscale eddies can significantly influence the deep-ocean subinertial flows (horizontal dispersal), particularly near large topography. Also, these eddy-influenced deep-ocean currents, mainly subinertial, contribute to driving, dissipating and modulating internal waves, and consequently are expected to affect diapycnal mixing (vertical dispersal). Examining the likely impacts of mesoscale eddies on the subsurface low-frequency currents as well as vertical mixing can potentially improve our understanding of the three-dimensional dispersal of subsurface materials in the GoM. The results gained from this study have numerous potential scientific and societal impact. Along with improving oil spill tracking capabilities in the GoM, the proposed study is also expected to yield useful information for harmful algae bloom prediction and tracking, fisheries ecology, dispersal of geochemical tracers, sediment transport, and so forth.

The major objective of this proposal is to analyze, understand and quantify the roles of mesoscale eddies in the three-dimensional dispersal of subsurface materials. The team will characterize and quantify the subsurface impacts of mesoscale eddies in the GoM by synthesizing and analyzing multiple streams of data sets. My specific role is to test the sensitivity of particle trajectory to the eddy-induced changes in subsurface velocity, mixing and particle decay. For this purpose, we will employ a simplified particle tracking model, with the physical processes calculated by the Lagrangian trajectory model, and the decay of oil expressed as a first-order, temperature-dependent decay rate of mass. The temperature effect is to alter buoyant velocity as particle size shrinks. The necessary simplification allows us to focus on the key physical and biochemical processes among the full complex oil-related reaction/interaction (e.g., emulsification, dissolution, sedimentation and biodegradation), and to test sensitivity of individual processes to mesoscale eddy motions.