AMOC, Water Mass Transformations, and Their Responses to Changing Resolution in the Finite‐VolumE Sea Ice‐Ocean Model

• Published in: Journal of Advances in Modeling Earth Systems
• Main Authors: Dmitry Sidorenko, Sergey Danilov, Vera Fofonova, William Cabos, Nikolay Koldunov, Patrick Scholz, Dmitry V. Sein, Qiang Wang
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union (AGU) 2020
• Subjects: Physical geography; GB3-5030; Oceanography; GC1-1581; North Atlantic; Sea ice
• Online Access: https://doi.org/10.1029/2020MS002317; https://doaj.org/article/74853bd663a04a8d9640b2611e4f18d8

Abstract The Atlantic meridional overturning circulation (AMOC) is one of the most important characteristics of an ocean model run. Using the depth (z) and density frameworks, we analyze how the sinking and diapycnal transformations defining the AMOC as well as AMOC strength and variability react to mesh refinement from low to higher resolution in two model runs driven by the CORE‐II forcing. Both runs can represent the key locations of sinking and diapycnal transformations behind AMOC, that is, northeastern North Atlantic. Although their spatial patterns do not change significantly with resolution in both frameworks as the consequence of the same atmospheric forcing, the quantitative differences, reaching several sverdrups, are seen in different locations between two model runs for both frameworks. In particular, the refinement leads to the strongest differences in the vertical transport and diapycnal transformations in the latitude range between 30°N and 55°N. The z framework emphasizes the role of localized upwelling around the Gulf Stream separation site, whereas the density framework emphasizes the contribution of (spurious) diapycnal mixing around the Grand Banks. Both effects are reduced in the higher‐resolution run, leading to higher AMOC south of 26°N as compared to the low‐resolution run, despite the AMOC maxima, located at high latitudes, are higher in the low‐resolution run. We suggest that both AMOC frameworks should be used routinely in standard analyses, including forthcoming intercomparison projects.