Momentum exchange near ice keels in the under ice ocean boundary layer

This thesis describes momentum exchange in the under-ice ocean boundary layer near ice keels. Understanding ice-ocean momentum exchange is important for accurate predictive ice modeling. Due to climate change, increased naval presence in the Arctic region is anticipated and ice models will become necessary for tactical and safety reasons. Measurements took place in March 2007 in the Beaufort Sea at the Applied Physics Laboratory Ice Station sponsored by the U.S. Navy. Turbulence measurements were made at a single point behind a large multi-year ice ridge in the upper ocean boundary layer. The keel was found to be at least 12.5m deep and much broader than expected. Ocean profiles showed the pycnocline between 13-18m deep and thus a unique situation of measuring the flow around a large ice structure in a shallow boundary layer presented itself. Results indicate that estimates of turbulence intensity depend on ice speed, direction and measurement depth. Velocity spectra indicate periods of low inertial subrange levels likely resulting from close proximity to the pycnocline. Low frequency variance in the velocity spectra was also observed and is thought to be a wake effect resulting from an under ice structure upstream of the flow.http://archive.org/details/momentumexchange109454282US Navy (USN) author.Approved for public release; distribution is unlimited