Near bottom water temperature anomalies: Mid‐Atlantic Ridge Crest at latitude 26°N

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Abstract
Six water temperature anomalies were measured along two profiles each about 10 km in length at the TAG Hydrothermal Field on the east wall of the rift valley of the Mid‐Atlantic Ridge at latitude 26°N. The temperature anomalies were measured using a 3 m‐long vertical array of four thermistors towed within 20 m of the ocean bottom. The anomalies exhibit increases in potential temperature up to 0.127°C above ambient and inverse gradients warming downwards as great as 4.2 × 10−2°C m−1. The temperature anomalies are distributed as point sources in a linear pattern about 7 km in length along known fault zones in the east wall of the rift valley between depths of 2750 and 3200 m below sea level associated with hydrothermal mineral deposits. The characteristics of the temperature anomalies and their geologic setting indicate an origin by discharge of hydrothermal solutions through the faults in the rift valley wall. The magnitudes of the anomalies are consistent with values previously used to estimate a heat output of the order of several megawatts per kilometer of ridge at the TAG Hydrothermal Field.