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Oceanographic evidence for a transient geothermal event affecting the Mid‐Atlantic Ridge
Author(s) -
Murton Bramley J.,
Redbourn Lisa J.
Publication year - 2000
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/1999gl002394
Subject(s) - geology , geothermal gradient , ridge , tectonics , basalt , salinity , temperature salinity diagrams , anomaly (physics) , mid atlantic ridge , water mass , oceanic crust , geophysics , petrology , geochemistry , oceanography , seismology , paleontology , subduction , physics , condensed matter physics
Long‐term monitoring has revealed variations in the temperature and salinity of bottom water overlying the axis of the Mid‐Atlantic Ridge. These are attributed to three primary mechanisms: externally introduced changes in the water mass; topography‐driven vertical mixing; and geothermal heating. Here, we focus on anomalous temperature changes that were induced within the ridge axis. Over a period of 35 days the bottom water warmed by up to 0.05°C but without changing its salinity. During the following 60 days, anomalously warm water was advected out of the southwestern end of the ridge axis at a depth of 2850 m. We attribute the temperature anomaly to a geothermal event, triggered by either magmatic or tectonic activity, during which ∼6.9 × 10 15 J of heat were dissipated. This is equivalent to the emplacement and cooling of 1.5 ± 0.15 × 10 6 m³ of basaltic material on, or into, the shallow oceanic crust. Alternatively, it could have been caused by the release of an upper crustal reservoir of warm, 50°C above ambient, with a volume of 3.4 × 10 7 m³.