N-ICE2015: Physical oceanography

This project will improve our understanding of the under-ice boundary layer, its coupling to the sea ice cover, and the underlying Atlantic Water (AW).

The proposed programme covers one of the key components of the sea ice heat budget during the drift, and will give important information on the role of inflowing AW. The vertical heat flux through the upper ocean strongly influences the sea-ice melting in this region, with observed fluxes to the ice ranging between 1 W/m² in the deep interior Arctic Ocean to 200 W/m² over the slope-following AW.

Recent studies highlight importance of increased AW temperature of ~2°C since the 1960’s and heat transport since the late 1990’s, suggesting that a 1 m loss of ice in this area is mainly driven by the AW variations. As the ice cover becomes thinner and has larger melt pond fraction, more incoming solar radiation will be absorbed (WP2) and, with some delay, contribute to the ice heat budget from below. Ocean mixing seems to be enhanced in the new ice free areas, mostly caused by the larger waves now appearing. As the marginal ice zone creeps northwards into the Arctic Ocean we might expect increased mixing in the future, with important implications for Arctic Ocean circulation and sea ice.

By making and analyzing state-of-the-art observations, this project will fill major gaps in our understanding and description of important processes linking AW heat with sea-ice melt. We will describe how upper ocean stratification interacts with sea ice evolution, and how a «young» sea ice cover (more melt ponds, greater open water fraction, shallower ridges) influences solar input and wind driven ocean mixing. Along with data from the atmosphere and radiation measurements the full sea ice energy budget can be closed and compared with observed ice mass balance. We will assess the geographical variation of AW transformation and influence on sea ice melt, investigate evolution of the surface melt layer, and relate these high resolution measurements to the larger scale Arctic Ocean hydrography.