MESI: A Multiparameter Eddy Significance Index

Abstract

In this study, we introduce the Multiparameter Eddy Significance Index (MESI) for use in conjunction with mesoscale eddy tracking to estimate the impact of mesoscale eddies on the upper ocean and marine ecosystems. MESI combines blended satellite observations of sea level anomalies, sea surface temperature, sea surface salinity, and ocean color chlorophyll-a and is a normalized index. When used in conjunction with mesoscale eddy tracking, MESI can highlight those eddies which extend into the deeper ocean and have a greater effect on nutrient cycling. Preliminary analysis in the Gulf Stream region of the western North Atlantic shows that MESI covaries with model estimates of nitrate, phosphate, iron, and pH with cross-correlation values between 76% and 95%. These results suggest that when MESI is used in concert with eddy tracking, it can be used as an indicator of eddies and areas that are more likely to impact nutrient cycling in the upper ocean. An additional analysis of MESI values inside eddies during Hurricane Dorian (2019) along the Carolina coast further suggests that MESI is most effective when used to enhance eddy tracking as it provides valuable insight into mesoscale eddy activity and the upper ocean circulation.