Simulating northern hemisphere glacier – ocean interactions using the Open Global Glacier Model and the Nucleus for European Modelling of the Ocean

Marine-terminating glaciers cover roughly one-third of the Northern Hemisphere's glacierized area (outside the Greenland ice sheet) and their direct freshwater export to the oceans has the potential to change not only global mean sea level (GMSL), but also local and regional ocean circulation patterns. Due to the interrelation of surface and frontal mass budgets, the dynamics of marine-terminating  glaciers are distinct from those of land-terminating glaciers forced only by the atmosphere. Here, were present recent advances in large-scale modeling of marine-terminating glaciers in the Open Global Glacier Model (OGGM). These include an enhanced representation of frontal processes and an independent calibration of surface and frontal mass balance. Further, we do a first investigation of coupling effects with an ocean general circulation model (Nucleus for European Modelling of the Ocean; NEMO). Including an explicit treatment of frontal processes (but so far ignoring future changes in ocean climate), we find that the spread between different emission scenarios at the end of the 21st century is reduced. Cumulative GMSL rise contribution projected for Northern Hemisphere glaciers is reduced by ca. 8 % in 2100, while the reduction for marine-terminating glaciers is ca. 23 %. Utilizing temperature and salinity output of NEMO, configured for the Arctic and Northern Hemisphere Atlantic (NEMO-ANHA4), to force a newly implemented submarine melt parameterization in OGGM, we estimate that 12 (6 - 22) % of the total frontal ablation was caused by submarine melt between 2010 and 2020. Finally, we explore differences in the ocean model’s output between runs that include the freshwater forcing from northern hemisphere glaciers and those that do not. The two main findings considering NEMO runs that include the freshwater forcing derived from OGGM output compared to those that do not are: i) an increased heat transport into Baffin Bay, and ii) changes in the pathways of Atlantic water to the Arctic Ocean, with less transport into the Barents Sea and more through Fram Strait.