MESI: A Multiparameter Eddy Significance Index

• Published in: Earth and space science (Hoboken, N.J.) N.J.), 2023-02, Vol.10 (2), p.n/a
• Main Authors: Roman‐Stork, H. L., Byrne, D. A., Leuliette, E. W.
• Format: Article
• Language: English
• Subjects: biogeochemistry; Chlorophyll; Eddies; eddy tracking; Fisheries; Hurricanes; index; Marine ecosystems; mesoscale eddies; multiparameter; Nutrient cycles; nutrient cycling; Ocean circulation; Plankton; Precipitation; Productivity; Sea surface temperature; Upper ocean; Water circulation; Water quality
• ISSN: 2333-5084; 2333-5084
• DOI: 10.1029/2022EA002583

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. Plain Language Summary A Multiparameter Eddy Significance Index (MESI) is introduced in an effort to begin to quantify the potential impact mesoscale eddies have on the upper ocean circulation, nutrient cycling, and biological productivity. MESI is calculated using satellite observations of sea level anomalies, sea surface temperature and salinity, ocean color derived chlorophyll‐a, and eddy kinetic energy and is a normalized index that maintains the integrity of the eddy circulation type. Analysis of MESI values in conjunction with multiparameter mesoscale eddy tracking results for a period from August 2019–July 2021 suggest that eddies with higher amplitude MESI values penetrate deeper into the upper ocean than eddies with lower amplitude MESI values. In comparing MESI values with nitrate, phosphate, iron, and pH, it was found that MESI covaries with nutrient values with cross‐correlations between 76% and 95%, suggesting that MESI can be used as an indicator for nutrient cycling potential within tracked mesoscale eddies. When MESI is paired with eddy tracking, our results suggest that the index can provide valuable insight into eddy activity and impact on the upper ocean, especially during hurricanes and other large storms. Key Points