Natural Variability in South Florida Sea Level Rise

Whether it be economic, ecological, or agricultural, the threats of sea level rise (SLR) in South Florida have been felt through nuisance flooding, saltwater intrusion and contamination of freshwater. While the dominant signal over the past century has been a steady increase in SLR associated with anthropogenic warming, we find that South Florida SLR is also well correlated with natural modes of variability in the ocean and atmosphere such as the Atlantic Multidecadal Oscillation (AMO), North Atlantic Oscillation (NAO), and Pacific Decadal Oscillation (PDO). Within these local drivers, the Gulf Stream ocean current was also expected to play a significant role. We ran statistical analyses on factors affecting sea surface height (SSH) in Key West. The rate of SLR in Key West is accelerating and has been increasing 7.48mm/yr since 2010. For the last 50 years, the NAO and AMO have shown strong correlations to sea level changes locally. The negative AMO pattern obtained from the spatial correlation of sea surface temperature to Key West SSH is tied to a weaker Gulf Stream flow and Atlantic Meridional Overturning Circulation (AMOC). However, we found that certain modes are present over some time frames, yet absent during others; suggesting that their relative influence on South Florida’s SLR may change over time. When analyzing the indices that describe the oscillatory behavior of the leading modes known to influence South Florida’s climate, it became evident that the NAO was well correlated with Key West SSH from 1948-1980 and again from 2005-2017. This positive NAO pattern is associated with a stronger wind circulation which corresponds with the path of the Gulf Stream. The PDO showed little concurrent correlation with Key West SSH until the period 2005-2017. Over the coming year these results will be applied to study the role of the AMOC in driving the AMO, and to better establish the relationships found between sea level in Key West and its regional drivers.