Quantifying the Residual Circulation of the Arctic Ocean

Geostrophic eddies in the ocean transport heat, salt, and mass in much the same fashion that storms transport heat, humidity, and mass in the atmosphere. The net effect of these eddy transports has a significant impact on the mean temperature and salinity stratification and circulation of the waters of the Arctic Ocean ? their climatology. Our understanding of these eddy transport process in the Arctic Ocean is weak. This project is devoted to improving that understanding.

The project contributes significantly to STEM workforce development. It will support the training of a post-doctoral associate and a graduate student. Furthermore, the principal investigators will develop a teaching module for the public ?Weather in a Tank? project - a laboratory guide for students to explore fluid dynamics experiments in a rotating frame to better understand the essential physics of atmosphere and ocean phenomena. The module will describe an instructive rotating laboratory experiment to simulate the fundamental principles at work in the Beaufort Gyre in the Arctic Ocean. The project also contributes indirectly to national security in that the mean salinity stratification of the Arctic Ocean is an important control on the fate of the Arctic sea ice cover, which influences resource development, transportation, tourism, and defense activities in the Arctic. A better understanding of eddy transport processes and their subsequent incorporation into models will improve projection of future states of the Arctic sea ice cover.

This project will determine, through study of a hierarchy of models in context with observations, the degree to which geostrophic turbulence plays a central role in setting the large-scale circulation of the Beaufort Gyre (BG) of the Canadian Arctic, shaping its so-called ?Residual? circulation. It is the Residual-mean circulation that transports tracers (e.g., heat, salt,

carbon) in the ocean, and this has two components: a contribution from the mean velocity (the ?Eulerian-mean? circulation), and a contribution from eddies (often called the ?bolus transport?). This decomposition has provided the essential framework for progress in understanding the fundamental dynamics and global climate implications of the Southern Ocean circulation. In this project, through study of the Residual-mean circulation and its components, fundamental dynamical processes at work in the Beaufort Gyre (BG) will be explored, including:

(1) analysis of the role of eddies in equilibrating the freshwater budget of the gyre, balancing the pumping down of fresh water from the surface by the action of the wind,

(2) examination of the role of boundary currents and seasonal forcing,

(3) characterization of the ?Residual-mean? circulation of the BG - distinguishing it from the ?Eulerian-mean? circulation.

Significant differences between Residual and Eulerian descriptions in the BG will mean that eddies have a leading order role in tracer transport. This will have far-reaching implications for Arctic oceanography, its circulation and biogeochemistry, how we interpret and take observations in the Arctic and how we model the Arctic.