Analysis and modeling of hydrothermal plume data acquired from the 85°E segment of the Gakkel Ridge

We use data from a CTD plume-mapping campaign conducted during the Arctic Gakkel Vents (AGAVE) expedition in 2007 to constrain the nature of hydrothermal processes on the Gakkel Ridge at 85 degrees E. Thermal and redox potential (Eh) anomalies were detected in two discrete depth intervals: 2400-2800 m (Interval 1) and 3000-3800 m (Interval 2). The spatial and temporal patterns of the signals indicate that the Interval 1 anomalies were most likely generated by a single large, high-temperature (T > 100 degrees C) vent field located on the fault terraces that form the NE axial valley wall. In contrast, the Interval 2 anomalies appear to have been generated by up to 7 spatially distinct vent fields associated with constructional volcanic features on the floor of the axial valley, many of which may be sites of diffuse, low-temperature (T < 10 degrees C) discharge. Numerical simulations of turbulent plumes rising in a weakly stratified Arctic Ocean water column indicate that the high-temperature field on the axial valley wall has a thermal power of 1.8 GW, similar to the Trans-Atlantic Geotraverse and Rainbow fields in the Atlantic Ocean, whereas the sites on the axial valley floor have values ranging from 5 to 110 MW.