Observations of Heat Flow on Hotspot Swells Robert N. Harris, Oregon State Univ. Marcia K. McNutt, MBARI 1.Marine Heat and Fluid Flow 2. Heat Flow on Hotspot Swells 3. Conclusions

seafloor thermistors Temperature Time each thermistor q = -k dT/dz dT/dz = thermal gradient k = thermal conductivity Marine Heat Flow

Subaerial versus Subsea Fluid Flow

Costa Rica Fisher et al., 2003

Hawaii

Reunion Bonneville et al., 1997

Crozet

Cape Verde

Bermuda

Take Home Points 1.High-resolution heat flow surveys at Hawaii and Reunion show large variability. Coarse surveys on other hotspot swells show increasing variability as volcanic edifices are approached. Both observations are consistent with fluid flow. 2.The most likely driving force is the bathymetric relief of the volcanic edices coupled with thin to nonexistant sediment cover. 3. One potential outcome of fluid flow is that the heat flux is diminished where sublithospheric heat flow anomalies are expected to be the greatest. 4. In areas of hydrothermal circulation, conductive thermal models should be used with caution.