Loop Current excursions and ring detachments during 1993-2009

摘要

Linkages between the variability of Loop Current (LC) surface dynamics, LC ring detachments, and the mean sea height anomaly in the Gulf of Mexico (GOM) are explored using a new methodology that locates the LC fronts and detects the shedding of LC rings. Based on satellite altimetry observations and dynamic height gradient, this methodology allows the determination of the dynamic structure in the region from 1993 to 2009. Northward penetration of the LC was found to be seasonal, with a tendency to increase during the spring and peaking in summer. Whereas northward oscillations exhibit ranges of 4 degrees of latitude, the range of westward oscillations is 6 degrees of longitude. Using the newly developed methodology, 28 LC rings are identified and described during 1993-2009. Starting in 2003, the LC is located more to the north on average, and the average number of LC rings formed per year increases. Since 2003, a significant increase in sea height residuals in the GOM has been observed, exhibiting a linear trend of 2.78 ± 0.26 cm/decade for the period 1993-2009. It is hypothesized here that the increase observed in sea height residuals is linked to the increase in mesoscale activity (LC northward intrusions and number of rings shed) obtained from satellite altimetry observations. Results shown here complement previous observational studies in the region, cover a longer time span, and define objectively the locations of the LC front and the shedding of the rings.