CMCC Webinar
23 November 2023, 11:00 CET
To join the webinar, register here

Speaker:
Casey Patrizio, CMCC – CSP Division

Moderator:
Panos Athanasiadis, CMCC – CSP Division

Abstract

The extratropical atmosphere–ocean system in the North Atlantic exhibits variability on subseasonal to multidecadal timescales that can influence regional climate in neighboring continents. Due to these large-scale climate impacts, climate models have been used extensively to better understand and predict this atmosphere–ocean variability. However, these efforts are hindered by model deficiencies in the representation of atmospheric and oceanic processes, in part due to insufficient model resolution.

In this webinar, I will first provide a brief overview of some key improvements in extratropical North Atlantic climate that arise from increased model resolution, focusing on results from recent studies utilizing multi-model output from the HighResMIP. Then, I will discuss findings from our recent study wherein the representation of North Atlantic atmosphere–ocean variability was assessed in low-resolution (LR) and high-resolution (HR) simulations from HighResMIP.

In our study, it was found that the LR simulations tend to overestimate the low-frequency variability of sea-surface temperature (SST) in the subpolar region and underestimate its relationship with the North Atlantic Oscillation (NAO), but that these deficiencies are significantly reduced in the HR simulations. It is argued that the LR simulation deficiencies are ultimately caused by a cold/fresh bias in a key subpolar region of oceanic deep convection, which promotes a positive feedback between subpolar salinity anomalies and the Atlantic Meridional Overturning Circulation (AMOC) rather than a negative AMOC–temperature feedback as in the HR simulations. Overall, our findings suggest that mean biases in the subpolar ocean can degrade the representation of extratropical North Atlantic atmosphere–ocean variability in climate simulations, and that increased model resolution can mitigate these deficiencies.

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