Oxygenation of western Norwegian fjords

In fjords, oxygenation depends on exchange or no exchange of deep fjord basin water. In sill fjords, water mass exchange is directly linked to the density of the water mass found around sill depth. Along the coast of Norway, warming water entails reduced density and less frequent renewal events. To evaluate to what degree such observed changes are within the range of natural variability, we need to expand our knowledge base beyond observations. Here, we present reconstructions of fjord oxygenation and associated water mass density in and outside of western Norwegian sill fjords. Sediment records covering the last few centuries will be presented, covering the transition from the Little Ice Age towards the recent warming, hence documenting responses taking place while transferring from a somewhat colder to warmer than preindustrial climate. The fjord basins were characterized by a transition from less well oxygenated to better oxygenated fjord bottom water. Drivers of change in fjord oxygenation and how the fjord basin changes are impacted by oceanographic changes taking place in the more open coastal oceans will be discussed.