Exploring the mixing of freshwater around Greenland in a high-resolution climate model using the freshwater transformation framework

In the sub-polar North Atlantic, perturbations to climatological mean freshwater fluxes can impact the strength of the climatically important Atlantic Meridional Overturning Circulation, providing an impetus for us to try and understand the pathways of freshwater in the region. In recent years, our understanding of the climatological mean horizontal pathways of freshwater through Greenland’s boundary current systems and out of the sub-polar North Atlantic have increased; however, we lack a thorough understanding of where freshwaters are destroyed by processes such as diahaline mixing.

In this study, I describe and use the freshwater transformation framework (based on the water mass transformation framework pioneered by Walin (1982)) to quantify how rates of diahaline mixing vary around Greenland with both season and region. I demonstrate the framework using an eddy resolving coupled configuration of the ICON earth system model (5 km ocean, 10 km atmosphere). Two patterns emerge:

• the destruction of fresh waters by mixing is stronger during wintertime than summertime;
• the destruction of fresh waters by mixing is stronger off the coast of southern Greenland than Northern Greenland.

Using the freshwater transformation framework, I also explore the interplay of diahaline mixing with the salinification of boundary currents, surface sources of freshwater, and the storage of low salinity water in different regions. I find that different processes dominate the climatological mean freshwater balance depending upon the season and region under consideration.