PHYSICAL OCEANOGRAPHY AND MODELLING
Dr. Mark Merrifield, Dr. Brian Powell, and Dr. Peter Winsor lead the physical oceanography teams at University of Hawai’i and University of Alaska at Fairbanks. The team will be investigating the dominant forcing on circulation within Andvord Bay (e.g. wind, buoyancy) and explore mixing as a result of tidal fluctuations across the fjord sill. All of these factors affect nutrient distributions, mixed-layer depths, etc. which have broad implications for the fauna of this ecosystem. In addition, members of the team will be developing a detailed ecosystem model for the region which can be used to test the affects of various parameters including those altered by climate change.
In order to fully characterize the circulation of the fjord and the surrounding region, the team will deploy 4 oceanographic moorings. These moorings (schematic below) will contain instruments which record temperature, salinity, and current speeds and direction (Acoustic Doppler Current Profilers) over the entire water column. These moorings will provide a good overview of the large-scale circulation of the area.
To determine smaller scale variation in circulation, the team will also use towed instruments (towed Acrobat vehicle) throughout the fjord in order to target regions of interest (e.g. the sill) and to get a more detailed view of circulation throughout the entire fjord. Targeted measurements using a Vertical Micro-profiler will resolve very small scale mixing which is very important for nutrient concentrations throughout the fjord. Conducting these measurements in tandem with chemical measurements (see ‘Chemical Oceanography/Phytoplankton’ for more information) will provide a detailed view of the physical influence on productivity.
In addition, the team will be utilizing gliders; autonomous instruments which are equipped with temperature, salinity, current, nutrient, and fluorescence sensors. The gliders can be programmed on-board to conduct a particular survey path through the fjord, deployed, and recovered hours later when it has completed the mission. This not only provides a very detailed view of the fjord in regions we may not be able to easily access, but it also allows the ship and researchers to conduct additional sampling simultaneously.
Dr. Martin Truffer from the University of Alaska at Fairbanks will be investigating glacial dynamics within Andvord Bay. As the glacial ice is in direct contact with the ocean, these two systems are tightly coupled; perturbations to one can heavily impact the other. Changes in meltwater fluxes can change the turbidity of the water and sedimentation rate as well as force buoyancy-driven circulation within the fjord. There is sufficient evidence suggesting that Antarctic fjords function differently than Arctic fjords (both physically and biologically) and therefore a detailed knowledge of the glaciology in the West Antarctic Peninsula regions is necessary.
Time-lapse cameras will be deployed within the fjord facing the calving-front of the glacier as well as facing down-fjord. The resulting imagery can be used to measure iceberg fluxes, residence times within the fjord, as well as surface snow and ice melt. This data coupled with detailed physical oceanographic data within the fjord and near the glacial-front will aid in determining the overall dynamics of this glacio-marine fjord.