Collaborative Research: Oceanic Response to Mesoscale Atmospheric Circulations in Terra Nova Bay
Polynyas, large areas of open water surrounded by sea ice, act like "windows" that expose the relatively warm ocean to the colder atmosphere. Although polynyas only cover a small fraction of the ocean surface, the transfer of heat and water vapor is so large that they play a significant role in the climate system leading to modifications of both atmosphere and ocean properties. The absence of an insulating sea ice barrier allows for energy and moisture exchange to rapidly warm and moisten the atmospheric column directly above and downwind of the polynya, altering regional atmospheric circulations. In the ocean the effect of the polynya is the massive production of salty, freezing point shelf water that is the prime ingredient in the formation of the globally important Antarctic Bottom Water and associated ventilation of the world ocean.
The Terra Nova Bay polynya is a prime example of a coastal polynya, and is the focus of this research. This project will use an observational program to simultaneously identify the mechanisms responsible for water mass modification within the Terra Nova Bay polynya and document all aspects of dense shelf water formation within an Antarctic polynya system. This study will characterize the water masses within Terra Nova Bay over the course of an annual cycle using in-situ oceanic observations. With the aid of an innovative uninhabited aerial vehicle (UAV), referred to as an Aerosonde, an intensive late winter/early spring observing period will be conducted that will quantify the surface energy budget components over the polynya and adjacent sea ice, describe the forcing for and near surface properties of regional mesoscale atmospheric flows responsible for polynya formation, and document the oceanic response to these flows at high vertical and temporal resolution. The measurements are the first such coordinated atmospheric and oceanic measurements to be made in the Antarctic at this time of year and therefore will provide an unprecedented view of the coupled atmospheric and oceanic processes acting at the polynya. The broad science questions to be addressed by this program include the following:
- How do the water column profile and dense salty shelf water (HSSW) characteristics evolve on time scales ranging from sub-synoptic to the annual cycle?
- What regulates the size of the TNB polynya and the sea-ice-air interactions that occur within the polynya?
- How do atmospheric processes over the Ross Sea modulate the intensity and spatial extent of katabatic winds, and other mesoscale flows, over TNB?