Collaborative Research: Role of Mesoscale Air-Sea Coupling in Climate Variability over the Southern Ocean

About This Grant

Processes governing the coupling of the atmosphere and ocean occur on a range of time and space scales and modulate weather and climate variability, as well as the ocean uptake of excess heat and carbon. This project is focused on advancing understanding of atmosphere-ocean coupling on mesoscales (100-1000 km) over the Southern Ocean and its impact on the long-term, large-scale climate variability of the region. This addresses a significant gap in the current understanding of mesoscale atmosphere-ocean coupling regarding its role in decadal to multi-decadal climate variability. The Southern Ocean has some of the most continuous and significant mesoscale ocean variability on the planet, motivating the choice to focus on this region. The investigators hypothesize that mesoscale air–sea interaction related sea surface temperature anomalies lead to large-scale reorganization of the mid-latitude jet stream over the Southern Ocean, which in turn feeds back onto the large-scale currents and mesoscale ocean variability in the region. To explore this idea, the investigators will use a hierarchy of coupled climate models of different resolutions and complexities, allowing them to isolate and explore regional-scale processes, as well as examine these processes in conjunction with larger-scale influences. The project’s focus on advancing understanding of climate variability on decadal time scales has strong societal implications. The project also includes the mentoring of undergraduate and graduate students and an early career scientist, as well as an outreach effort with local high school science educators, addressing NSF’s priority to educate the next generation of scientists and the public on important science issues. The team will take a hierarchical modeling approach, using both the Community Climate System Model v4 (CCSM4), and the intermediate complexity, moist quasi-geostrophic coupled model (MQ-GCM). CCSM4 coupled simulations to be examined by this study include a low-resolution and high-resolution ocean component and an interactive atmospheric ensemble approach established by the team in earlier work. This unique approach to coupled modeling allows the atmospheric noise to be filtered out of the model simulations, which for this study represents the atmospheric feedback from the mesoscale oceanic eddies. Thus, comparing the control simulations with the filtered simulations will help test the team’s hypothesis that feedback from the ocean to the atmosphere on mesoscales affects longer term conditions in both the atmosphere and ocean in the Southern Ocean region. Additional fully coupled and reduced coupled simulations will also be carried out under a doubling of atmospheric CO2 to understand the sensitivity of the multi-scale coupling processes to different background states. By exploring the importance of mesoscale interactions on the climate system, the project addresses a current gap in understanding and creates avenues for model improvement of decadal to multi-decadal climate variability. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.