Abstract
Warm Core Rings (WCRs) in the Gulf Stream (GS) play a major role in distributing heat and salt over the shelf and slope seas. A database of WCR characteristics was developed for the time period of 1980 to 2017 using a consistent and continuous set of GS charts. Multiple analyses were carried out to understand the variability of WCR formations, detect regime shifts within the 38-year study period, and to determine the survival of WCRs. WCR formations peak in late spring and early summer and there are few rings in winter. The same pattern of seasonality persists on a sub-regional basis. More than 2/3ʳᵈ of WCRs are formed to the east of 65°W. The high interannual variability observed in WCR formation motivated investigating a potential regime change. A significant regime shift was detected in the year 2000. This regime change was pervasive in all four subregions. Increasing numbers of WCR Formation, reduction in average lifespan, and an increased WCR impact were observed during the 2000-2017 regime. Multiple survival analysis methods indicated a higher survival probability for WCRs formed within the 70°-65°W longitude band. The radius of a WCR at formation, distance traveled during the ring's life, and latitude of formation - all have a significant effect on the survival of WCRs when a Cox proportional hazard model was employed for whole GS region. Similar regime changes reported in the shelf ecosystem of northeast United States around the year 2000 supports the relationship between shifting ocean dynamics and ecosystem responses which need to be explained by further investigations.