Joint Seminar: Subpolar North Atlantic’s mean state affects the overturning response to the North Atlantic Oscillation
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.
Date
10.05.2023
Time
13:30 h
Place
- Bundesstr. 53, room 022/023
- Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg