Deep-Sea Research II 49 (2002) 4003–4021 A Subtropical Oceanic Ring of Magnitude (STORM) in the Eastern North Atlantic: physical, chemical and biological properties Beatriz Mouri * no a, *, Emilio Fern ! andez a , Jos ! e Esc ! anez b , Demetrio de Armas b , Sylvie Giraud c , Bablu Sinha d , Robin Pingree e a Universidade de Vigo, Departamento de Ecolox ! ıa e Biolox ! ıa Animal, Campus Lagoas-Marcosende, E-36200 Vigo, Spain b Instituto Espa * nol de Oceanograf ! ıa, E-38120 Santa Cruz de Tenerife, Spain c Collecte Localisation Satellites, 8-10, rue Herm" es, 31526 Ramonville St-Agne, France d Southampton Oceanography Centre, Southampton SO14 3ZH, UK e The Laboratory, MBA Citadel Hill, Plymouth PL1 2PB, UK Received 15 September 2000; received in revised form 26 February 2001; accepted 5 June 2001 Abstract A Subtropical Oceanic Ring of Magnitude (STORM) that budded from the Azores Current was studied in the Eastern North Atlantic Ocean in April 1999. The cyclonic eddy, called Leticia, was centred at B32.41N–28.71W and extended across more than 200 km in an east–west direction. Leticia had been previously detected by means of TOPEX/ POSEIDON altimetry data and further intensively investigated using expendable bathythermograph and conductivity– temperature–depth stations. The altimeter surface signature of the eddy revealed a B20-cm sea-level depression, an upward displacement of the 161C isotherm of B125 m was linked to the eddy centre and Geostrophic transport of the amount of water swirling cyclonically was 7 Sv. The temperature, nitrate, and oxygen anomalies on the s 0 ¼ 26:5 isopycnal surface inside Leticia were 0.41C, 1 mmol l 1 , and +0.3 ml l 1 , respectively, with respect to surrounding waters. Shallowing (>50 m) of the deep chlorophyll maximum (>0.3 mg m 3 ) was observed at the eddy centre associated with vertical displacements of the isotherms (>100 m) within the photic layer. Vertical excursions of the isopycnals and the deep chlorophyll maximum of more than 30 m were observed over temporal scales of a few (3–6) h. Integrated nitrate concentration over the photic layer was B4-fold higher inside Leticia than outside, however, primary production rates were only slightly higher. Eddy diffusive fluxes across the nitracline, located B30 m below the deep chlorophyll maximum, ranged from 0.02 to 0.10 mmol NO 3 m 2 d 1 , and explained o25% of the nitrate required to sustain the estimated new production (0.24–0.48 mmol NO 3 m 2 d 1 ). r 2002 Elsevier Science Ltd. All rights reserved. 1. Introduction Several observational (e.g., Angel and Fasham, 1983; Falkowski et al., 1991; McNeil et al., 1999) and modelling studies (e.g., McGillicuddy et al., 1995; McGillicuddy and Robinson, 1997) indicate that mesoscale features could play an important role in nutrient supply to the upper productive layer in subtropical nutrient-depleted regions. Recently, Oschlies and Gar - con (1998) have esti- mated that mesoscale eddy activity could account for about one-third of the total flux of nitrate into *Corresponding author. Tel.: +34-986-814-087; fax: +34- 986-812-556. E-mail address: beame@uvigo.es (B. Mouri * no). 0967-0645/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII:S0967-0645(02)00139-X