05.06.2023: online Ocean Circulation and Climate Dynamics Colloquium

- online only-

When?  Monday, 5 June  2023 at 11 am
Where?     zoom https://geomar-de.zoom.us/j/89174395310?pwd=UlNqcXByWWw0UnMzQWRJU25uNTgwZz09 

Meeting ID: 891 7439 5310
Passcode: 433855

Abstract: 
Climate models are a valuable tool to study the interaction between ocean and atmosphere. Nevertheless, they are known to suffer from various biases and uncertainties. In the subpolar North Atlantic large uncertainties among models from the Coupled Model Intercomparison Project phase 6 (CMIP6) are found in the mean surface temperature and salinity, and the sea ice concentration. These mean state biases will affect the air-sea interaction.
In this study, we are investigating the diversity of CMIP6 models with respect to their response of the Atlantic Meridional Overturning Circulation (AMOC) to the North Atlantic Oscillation (NAO) in pre-industrial control experiments. This response is sensitive to the mean spiciness of the North Atlantic. Thus, we focus on two categories of models: Models that are spicy (warm-salty) and models that are minty (cold-fresh) within the subpolar gyre of the North Atlantic. Warm-salty models tend to have a lower sea ice cover in the Labrador Sea (LS) and larger LS heat loss during a positive NAO, compared to cold-fresh models. Also, warm-salty models have a weaker stratification in the LS. Sub-surface density changes 1 to 3 years after the NAO are larger in the warm-salty models and establish a zonal density gradient that can cause a stronger delayed AMOC response that is also more coherent across latitudes.
These findings stress the importance of realistic mean states to reduce uncertainties in the AMOC variability.

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