Mesoscale variability in the Gulf of Mexico and its importance in climate extremes over North America

The motivation for this study is in the need to improve understanding and modeling capabilities of regional air-sea interaction processes within the Intra-Americas Sea (IAS) region and their relationship with climate extremes. Oceanic circulation, which is characterized by strong mesoscale (order of 10-100km) variability, strongly affects airsea interactions in the region and distribution of heat anomalies, which has important implications for U.S. climate. In particular, distribution of surface temperature anomalies associated with the Atlantic Warm Pool (AWP) influence the rainfall over North America, thus playing a key role in frequency and severity of draughts and rain events. In addition, heat anomalies play the role of a heat reservoir for hurricanes in the IAS, particularly in the Gulf of Mexico (GoM) region, controlling conditions favoring their formation and intensification. In this regard, the mesoscale variability in the GoM – a key region linking the IAS and continental U.S. – is particularly important. The GoM circulation is complex and highly variable, and its rich dynamics, as well as its connection to the North American climate, continue to be poorly understood. Furthermore, key mesoscale processes involved in the dynamics are not captured by the current generation of CMIP5-class climate models, which lack resolution in their ocean component.

The goal of this study is to improve understanding and modeling capabilities of the circulation within the IAS and its mesoscale variability with implications for U.S. climate and extreme events. Our particular focus is on the major conduit of oceanic heat transport in IAS – the Caribbean Current (CC) / Loop Current (LC) system and associated eddies through Yucatan and into the GoM. Specific objectives are to analyze: (i) the dynamics of mesoscale variability in GoM; (ii) the importance of this variability for the heat distribution; (iii) role of these processes and their adequate resolution for climate studies. To achieve these objectives, we propose a comprehensive approach, which will utilize a hierarchy of numerical simulations, both coupled atmosphere-ocean and ocean-only, including the analysis of CMIP5-class climate model existing simulations. Key novel elements of the proposed research include examination of mesoscale dynamics in ocean-only models at very high resolutions not previously available, as well as a comparative analysis of coupled CMIP5-class simulations with low and high resolution in the oceanic component.

This proposal addresses MAPP Priority Area 3: “Modeling of Intra-Americas Sea climate processes associated with extremes over North America”. The proposed work is relevant to NOAA’s long-term goal to “Understand Climate Variability and Change to Enhance Society’s Ability to Plan and Respond”, by offering a comprehensive, novel study of the oceanic mesoscale processes in the IAS (focusing on the GoM domain) which are relevant for hurricanes and rain/draught events over North America. Adequate spatial resolution of oceanic mesoscale circulation is essential for accurate representation of oceanic processes in climate simulations. Comprehensive studies of mesoscale processes and their relevance to climate variability are urgently needed. The proposed study will make progress in this direction, by focusing on the poorly known mesoscale variability in a dynamically active region of the IAS. In particular, expected outcomes of this study include investigation of the importance of increased resolution in the ocean in climate model ability to capture essential processes in the region and to improve prediction of extremes. This study will be conducted through CIMAS Themes, “Climate Research and Impacts” and “Ocean Modeling”.