SGER: An Exploratory Full-Depth Section of Mixing Observations Across the Arctic Ocean

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

Funds are provided to conduct an exploratory investigation of diapycnal mixing across the entire Arctic basin from surface to full ocean depth using an innovative instrument capable of measuring microscale temperature, conductivity and velocity shear under challenging ice-covered conditions during the upcoming pan-arctic Beringia 2005 expedition. The microstructure measurements will be analyzed together with information from lowered acoustic Doppler current profiler and a full hydrographic-biogeochemical program. The dissipation rates of thermal variance and turbulent kinetic energy will be measured and used to estimate the vertical diffusivity across the whole basin. The proposed measurements are highly exploratory. Furthermore, microstructure instruments and their probes are very sensitive, adding to the uncertainty and high risk of such measurements in ice-covered regions. If successful, these observations may enable a significant leap forward in understanding of mixing in the Arctic Ocean and its influence on lateral and vertical fluxes of heat, salt and momentum. A key issue for understanding and predicting heat and freshwater uptake, storage and transport by the ocean is the rate of mixing across density surfaces in the ocean's interior. Such mixing is a prerequisite for the renewal of deep waters and is essential for upper ocean heat transfer and storage. Understanding this critical process has become more urgent of late, as it is now realized that mixing processes have very complex distributions, quite different from the uniform mixing rate assumed in models. One particularly important issue is understanding those mixing processes that control the vertical flux of heat, in the Arctic Ocean, from warm subsurface waters to the sea surface where the heat can contribute to the loss of sea ice, and how these might vary due to global change.