In situ temperature and heat flow were determined in 1994 at 159 sites, grouped into 66 clusters between latitude 65° N and 67°30’ N at water depths from 669 m to 1464 m. The mean of all cluster heat-flow measurements conducted in this survey was 58.5 mW m−2, with a standard error of ±4.40 mW m−2. The mean heat flow from IKU well data for the Trøndelag Platform is 56.2±6.65 mW m−2. Shorter wavelength heat-flow variations appear to be controlled structurally and can be explained by sedimentation and thermal refraction effects. High heat flow associated with faulted structural highs such as the Nyk High and Vema Dome–Rym Fault Zone may also result from hydrothermal convection. Relatively isolated high (106.6 mW m−2) heat flow observed at 846 m water depth may be an artefact of bottom water disturbances; however, virtually identical deep-water heat-flow anomalies, believed to be of hydrothermal origin, also exist. While heat-flow measurements made at water depths less than 1000 m should be regarded with caution, there is presently no justification for eliminating those exhibiting linear heat flow with depth. Submarine avalanches seem unimportant in the survey area. Neither crustal thinning, underplating nor sill intrusion, within the last 50 Ma, would have a measurable effect on present-day heat flow. The net effect of crustal thinning may be a reduction of the crustal heat generation potential, depending on the degree of thinning of the upper crust, since the accumulating sediments cannot compensate fully for the lost heat generation from a crystalline basement.

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