Abstract
AbstractAn unusual double-thermostad warm-core ring of the Gulf Stream was discovered in the Slope Sea, south of Georges Bank, during the R/V Endeavor cruise 578 in May 2016. The ring’s stratification was peculiar as it included two thermostads at, respectively, 100–200 m (core T = 18.14°C, S = 36.52) and 250–500 m (core T = 16.70°C, S = 36.35). Extensive use of satellite data (SST imagery and SSH maps) allowed the life history of this ring to be reconstructed, with independent SST and SSH data mutually corroborating each other. The double-thermostad ring was formed by vertical alignment of two preexisting warm-core anticyclonic rings of the Gulf Stream. The first ring spawned by the Gulf Stream in February has cooled by ~2°C before merging in April with the second ring spawned by the Gulf Stream in March. During vertical alignment of these rings, the warmer ring overrode the colder ring, thereby forming the double-thermostad ring surveyed in May 2016. From ADCP sections through the ring, the upper and lower thermostads had different core relative vorticities of −0.65f and −0.77f, respectively, where f is the local Coriolis parameter. An in-depth literature survey has confirmed that this is the first report of a double-thermostad warm-core ring of the Gulf Stream and one of the best-documented cases of vertical alignment of two eddies ever observed in the World Ocean.
Highlights
During a short technology-testing cruise to GeorgesBank southeast of Cape Cod in May 2016, a sequence of cloud-free high-resolution satellite images of sea surface temperature (SST) revealed a very well-formed warmcore ring (WCR or ring hereafter) immediately to our south
The Gulf Stream WCR described in this paper was first spotted in satellite SST imagery of 11 May 2016, showing the ring centered at 398450N, 668500W and impinging on the southern flank of Georges Bank (Fig. 1)
The ring was unusual by having two pycnostads: the upper one at 100–200 m with core T 5 18.148C, S 5 36.52, z 5 20.65f, and the lower one at 250–500 m with core T 5 16.708C, S 5 36.35 and z 5 20.77f
Summary
College of Marine Science and Technology, Zhejiang Ocean University, Zhoushan, China, and Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island. Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island (Manuscript received 5 February 2019, in final form 13 November 2019)
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