Led by Scripps Institution of Oceanography (SIO) scientists Jen MacKinnon and Matthew Alford, and University of Washington scientist John Mickett, our ArcticMix team is embarking on a month-long expedition to the Arctic Ocean. The team includes five SIO graduate students, project scientists, technicians, and colleagues from around the world. The overall goal of this National Science Foundation (NSF) funded experiment is to understand the role ocean heat might be playing in the accelerating loss of Arctic sea ice.
The rate of ice melt is set by a complex interplay between inflow of warmer waters through Bering and Fram Straits, retention of heat from the sun in the upper ocean, and turbulent mixing within the ocean interior. Most of these processes are heavily influenced by the ‘stratification’ – the layering of relatively light fresh water from river plumes and ice melt overtop salty, denser water below. One of the peculiarities of the Arctic circulation is that the surface waters are cold, generally near-freezing, while the salt water below is a few degrees warmer. This is in contrast to most of the ocean, where warmer waters overlie cooler. The difference here is that density in the Arctic is set by salinity, not temperature.
Historically the Arctic Ocean interior has been quiet, and the heat contained in sub-surface waters was sequestered from contact with the surface by a layer of thick ice. However, the more the ice melts, the more turbulent the ocean is likely becoming, and this deeper heat might be getting mixed upwards, warming surface waters and accelerating the rate of ice melt. Our team is bringing several innovative tools, developed with Office of Naval Research (ONR) funding, for studying these processes. Our tools include a microstructure profiler for directly measuring turbulence at centimeter scales, and a towed body that will let us map out the spatial extent, interleaving and evolution of both warm and cool, fresh water masses. Our ultimate goal is to unlock the physics driving this mixing and resultant surface heating, so that the relevant processes can more accurately represented in Arctic Ocean forecast models.
We’ll be spending the next month on the new R/V Sikuliaq, owned by NSF and operated by the University of Alaska. Our initial hypothesis might be borne out by the planned measurements, or we might find something entirely new and completely unexpected happening in those icy waters; such is the joy of exploration!