13 Sep 2023
 | 13 Sep 2023
Status: this preprint is open for discussion.

A comprehensive Earth System Model (AWI-ESM2.1) with interactive icebergs: Effects on surface and deep ocean characteristics

Lars Ackermann, Thomas Rackow, Kai Himstedt, Paul Gierz, Gregor Knorr, and Gerrit Lohmann

Abstract. The explicit representation of cryospheric components in Earth System models has become more and more important over the last years. However, there are only few advanced coupled Earth System models that employ interactive icebergs, and most iceberg model studies focus on iceberg trajectories or ocean surface conditions.

Here, we present multi-centennial simulations with a fully coupled Earth System model including interactive icebergs to assess the effects of heat and freshwater fluxes by iceberg melting on deep ocean characteristics. The icebergs are modeled as Lagrangian point particles and exchange heat and freshwater fluxes with the ocean. They are seeded in the Southern Ocean, following a realistic present-day size distribution. Total calving fluxes and the locations of discharge are derived from an ice sheet model output which allows for implementation in coupled climate-ice sheet models.

The simulations show a cooling of deep ocean water masses in all ocean basins that propagates from the southern high latitudes northward. We also find enhanced deep water formation in the continental shelf area of the Ross Sea, a process commonly underestimated by current climate models. The vertical stratification is weakened by enhanced sea-ice formation and duration due to the cooling effect of iceberg melting. The deep water formation in this region is increased by up to 10 %. By assessing the effects of heat and freshwater fluxes individually, we find latent heat flux to be the main driver of these water mass changes. The altered freshwater distribution by freshwater fluxes and synergetic effects play only a minor role. Our results emphasize the importance of realistically representing both heat and freshwater fluxes in the high southern latitudes.

Lars Ackermann et al.

Status: open (until 08 Nov 2023)

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Lars Ackermann et al.

Lars Ackermann et al.


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Short summary
We present long-term simulations with interactive icebergs in the Southern Ocean. By melting, icebergs reduce the temperature and salinity of the surrounding ocean. In our simulations, we find that this cooling effect of iceberg melting is not limited to the surface ocean but also reaches the deep ocean and propagates northward into all ocean basins. Additionally, the formation of deep water masses in the Southern Ocean is enhanced.