Upper ocean observations in eastern Caribbean Sea reveal barrier layer within a warm core eddy

• Published in: Journal of geophysical research. Oceans 2017-02, Vol.122 (2), p.1057-1071
• Main Authors: Rudzin, J. E., Shay, L. K., Jaimes, B., Brewster, J. K.
• Format: Article
• Language: English
• Subjects: Air temperature; Aircraft; Aircraft components; air‐sea interaction; Anomalies; Atmosphere; Atmospheres; barrier layer; Barrier layers; Barriers; Brazil Current; Brunt-vaisala frequency; Buoyancy; Caribbean Sea; Climatology; Current rings; Cyclones; Density stratification; Dimensional measurement; Eddies; Eddy currents; Entrainment; Geophysics; Gulf of Mexico; Hurricanes; in situ observations; Lower atmosphere; Marine; Ocean circulation; Ocean currents; Ocean-atmosphere interaction; Oceans; Profilers; Research aircraft; Stratification; Temperature (air-sea); Temperature effects; Thermal structure; Thermocline; Tropical climate; Tropical cyclones; Upper ocean; Velocity; Warm water; warm‐core eddy; Water mass characteristics
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1002/2016JC012339

Three‐dimensional measurements of a large warm core eddy (WCE) and the Caribbean Current are acquired using oceanic profilers deployed during a NOAA research aircraft study in September 2014 in the eastern Caribbean Sea. Measurements of the near‐surface atmosphere are also collected to examine air‐sea processes over the eddy. These novel measurements showcase temperature and salinity for the eddy and background flow, upper ocean stratification, a residing barrier layer (BL), velocity structure, and water mass characteristics. The eddy's thermal structure is alike that of WCEs in the Gulf of Mexico (GoM) whereas surrounding waters have relatively deeper isotherms compared to its GoM counterparts. Analyses suggest that upper ocean stratification within the study region is due to a BL. These are the first observations of a BL inside a WCE to the best of our knowledge. Reduced shear comparisons suggest that the upper ocean, especially within the WCE, would be more resistant to tropical cyclone (TC) induced mixing than the GoM because of the BL. The eddy is suspected to originate from North Brazil Current rings, given its fresh anomalies relative to climatology and surrounding waters and its trajectory prior to sampling. Atmospheric measurements suggest the WCE is influencing the lower atmosphere along its boundaries. These observations signify that not only does this WCE have deep thermal structure and modulate the near‐surface atmosphere but it is unique because it has a BL. The findings and analyses suggest that a similar eddy could potentially influence air‐sea processes, such as those during TC passage. Key Points: In situ upper ocean observations show a barrier layer in a warm‐core eddy in the eastern Caribbean Sea Barrier layer enhances buoyancy frequency in upper ocean in the Caribbean Sea compared to Gulf of Mexico, especially in the warm eddy Deep warm water in WCE and large upper ocean stratification could act to inhibit thermocline water entrainment during TC passage