Investigating the Connection between the Atlantic Meridional Overturning Circulation (AMOC) and the Northwest Atlantic Coastal Sea Level: Connecting the Dots across the Shelf Break

Two research areas in the Atlantic Ocean have received elevated interests in the community: (1) the stability and variability of the Atlantic Meridional Circulation (AMOC), and (2) the accelerated sea level rise (SLR) along the North American Coast from Cape Hatteras to Nova Scotia. The relationship between them, i.e., whether the observed coastal SLR is resulted from changes in the AMOC and whether a predicted weakening of the AMOC transport will further accelerate coastal SLR, is still being debated. As a circulation system in the open ocean, the AMOC would need to overcome the strong topographic barrier across the continental shelf break in order to influence coastal sea level. The cross-shelf connection is the least understood aspect in any suggested mechanisms linking coastal sea level variability to the AMOC changes. Most present climate models and basin-scale Ocean General Circulation Models (OGCMs), even with increasing resolutions, are not up to the task to address the complex cross-isobath processes near the continental shelf break. This is due to the fact that many coastal processes are often not well represented or adequately treated in global scale models, which are optimized for the large-scale processes like the AMOC and Gulf Stream (GS). Therefore, a well-treated and carefully designed regional model forced by dynamically consistent global model is more desirable for assessing the relationship between coastal sea level and the AMOC.
In this project, we propose an integrated approach using both in situ and satellite observations, eddy-resolving global data-assimilative reanalysis, and a hierarchy of numerical models, including a state-of-the-art regional ocean circulation model and a 2-layer process model to study the dynamical linkages between the AMOC and the sea level variability on the Northwest (NW) Atlantic shelf over interannual and decadal time scales. Specifically, we will analyze the AMOC variations on various time scales using available observations and global eddy-resolving, data assimilative simulations, characterize and quantify their impacts on western boundary currents (WBCs) and slope currents, search possible connections with coastal sea level changes, and identify and examine cross-shelf connection processes and mechanisms using models. Our goal is to identify and understand key cross-shelf processes and mechanisms that are important in connecting the AMOC and coastal sea level variability, based on which we can further develop predictive skills for coastal sea level changes. The outcome of this project will also be useful for the improvements of climate models in their representations of coastal processes.
Our proposed work directly addresses the Competition of CVP – Decadal Climate Variability and Predictability in the area of investigation of the relationship between the Atlantic Meridional Overturning Circulation (AMOC) and global and regional sea level (historical, current, and/or future), with a focus on understanding sea level extremes and coastal impacts in the United States, for the improved understanding of the ocean-climate system. This project is also responsive to the CPO’s strategy in addressing challenges in the areas of Weather and Climate Extremes, Climate impacts on water resources and Coasts and climate resilience.