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Mechanisms of internal Atlantic multidecadal variability in HadGEM3-GC3.1 at two different resolutions

Lai, W. K. M., Robson, J. I. ORCID: https://orcid.org/0000-0002-3467-018X, Wilcox, L. J. ORCID: https://orcid.org/0000-0001-5691-1493 and Dunstone, N. (2021) Mechanisms of internal Atlantic multidecadal variability in HadGEM3-GC3.1 at two different resolutions. Journal of Climate. ISSN 1520-0442 (In Press)

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To link to this item DOI: 10.1175/JCLI-D-21-0281.1

Abstract/Summary

This study broadly characterises and compares the key processes governing internal AMV in two resolutions of HadGEM3-GC3.1: N216ORCA025, corresponding to ~60km in the atmosphere and 0.25 degrees in the ocean, and N96ORCA1 (~135km / 1 degree). Both models simulate AMV with a timescale of 60-80 years, which is related to low frequency ocean and atmosphere circulation changes. In both models, ocean heat transport convergence dominates polar and subpolar AMV, whereas surface heat fluxes associated with cloud changes drive subtropical AMV. However, details of the ocean circulation changes differ between the models. In N216 subpolar subsurface density anomalies propagate into the subtropics along the western boundary, consistent with the more coherent circulation changes and widespread development of SST anomalies. In contrast, N96 subsurface density anomalies persist in the subpolar latitudes for longer, so circulation anomalies and the development of SST anomalies are more centred there. The drivers of subsurface density anomalies also differ between models. In N216, the NAO is the dominant driver, while upper-ocean salinity-controlled density anomalies that originate from the Arctic appear to be the dominant driver in N96. These results further highlight that internal AMV mechanisms are model dependent and motivate further work to better understand and constrain the differences

Item Type:Article
Refereed:Yes
Divisions:Science > School of Mathematical, Physical and Computational Sciences > NCAS
Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:100876
Publisher:American Meteorological Society

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