A25. Implementation of Greenland Ice Sheet Freshwater Fluxes in E3SM Models

Title

Implementation of Greenland Ice Sheet Freshwater Fluxes in E3SM Models

Authors

Theresa Morrison (1), Julie McClean (1), Sarah Gille (1), Mathew Maltrud (2), Frank Bryan (3), Gustavo Marques (3), Detelina Ivanova (1); 1. Scripps Institution of Oceanography, 2. Los Alamos National Laboratory 3. National Center for Atmospheric Research

Abstract

Mass loss from the Greenland Ice Sheet has increased in recent decades adding a source of freshwater to the Subpolar North Atlantic. Freshwater perturbation experiments have shown that deepwater formation is sensitive to the magnitude and distribution of excess freshwater. However, these experiments have often not accounted for the vertical dilution of freshwater that occurs in narrow fjords along the ice sheet margin. The dilution and vertical structure of ice sheet melt water modify stratification and therefore are critical for understanding downstream impacts. Fully resolving the dynamics within glacial fjords is beyond the capabilities of high resolution Earth System Models and coupling between ice sheet and ocean models remains limited. 

We are implementing two methods for representing this dilution: a uniform vertical distribution and a fjord box model. We present results from global 0.1 degree E3SMv0 (POP2-CICE5, COREII forcing) hindcast simulations with freshwater added in a uniform vertical distribution over the top 200m of the ocean. We compare the salinity properties in the Subpolar North Atlantic during the first 5 years of the freshwater perturbation period to a control simulation. In addition we present the theory of the fjord box model that we are implementing in E3SMv1. The box model uses the conservation of salt and potential energy to estimate the dilution of ice sheet meltwater within a fjord. This box model is aimed at contributing to improved coupling of ice sheet and ocean models within E3SM.