National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2008

Ocean current and temperature time series at Brothers volcano

Lavelle, J.W., G.J. Massoth, E.T. Baker, and C.E.J. de Ronde

J. Geophys. Res., 113, C09018, doi: 10.1029/2007JC004713 (2008)

Time series of currents and temperatures were acquired near surface and at depth on three moorings above Brothers volcano (34° 52.25′S, 179° 04′E), ~25 km west of the Kermadec Ridge and ~300 km northeast of the North Island, New Zealand, from September 2004 to May 2005. Ocean current time series were previously unavailable within 300 km of this site, and few such measurements exist anywhere near magmatically or hydrothermally active volcanoes such as Brothers. Energy in near surface currents (163–527 m depth) was primarily subtidal (64%). Subtidal motions to 527 m depth are shown to be reasonably well correlated with geostrophic currents derived from satellite sea level anomalies. Although the moorings were separated laterally by only 11 km, the upper current meters also recorded significant differences in M2 tidal currents, indicating the presence of significant internal tides at this site. Below volcano summit depth (1220 m), the kinetic energy of currents was primarily tidal (54%). Longer period currents at depth evidenced the influence of volcano topography. Temperature time series showed a 3-month period of sharply decreased temperature that extended in depth from 163 m to at least 1260 m. Advanced Very High Resolution Radiometer (AVHRR) sea surface temperature data show colder surface water immediately above and north of Brothers over the same time period. These data together with the velocity records suggest an anomalous, deep, cold water mass arrived and lingered over Brothers for 3 months in the austral late spring and early summer of 2004–2005.

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