Other
Scientific paper
Dec 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agufmos32c..04e&link_type=abstract
American Geophysical Union, Fall Meeting 2001, abstract #OS32C-04
Other
4207 Arctic And Antarctic Oceanography, 4832 Hydrothermal Systems, 8135 Hydrothermal Systems (8424), 8424 Hydrothermal Systems (8135)
Scientific paper
The Gakkel Ridge, extending through the Eurasian Basin of the Arctic Ocean from north of Greenland to the Laptev Sea, is the slowest spreading mid-ocean ridge on the planet. There has been extensive speculation about crustal generation processes, the presence or absence of extrusive volcanic activity, and high temperature hydrothermal venting and associated fauna on the Gakkel Ridge, but data have remained scarce due to the relative inaccessibility of the ridge. From the end of July to early October, 2001, a team of scientists aboard the new icebreaker USCGC Healy and the RV Polarstern undertook the first systematic sampling of the Gakkel Ridge, largely for petrological studies. Miniature Autonomous Plume Recorders (MAPRs) were deployed on the trawl wire during dredging and rock coring operations, in order to identify sites of hydrothermal venting through light scattering and temperature anomalies associated with hydrothermal plumes. As of August 26, we have surveyed over 200 km of the ridge, from 8 degrees West to 15 degrees East, and identified at least four distinct areas of hydrothermal activity: the first ever found on the Gakkel Ridge. The extent of evident hydrothermal activity is remarkable, and unexpected in light of previous observations of the covariance between plume incidence (percent of ridge overlain by plumes) and spreading rate. Of 47 successful MAPR deployments so far, 36 show layers of high light scattering, with clearly defined upper and lower boundaries, well above the seafloor. Of these, 14 are large enough to have corresponding temperature anomalies (on the order of 0.01 degrees). Sulfide chimneys have been dredged at one site, on the flank of an axial volcanic edifice located near the intersection of the western Gakkel Ridge and Lena Trough. A single CTD cast, performed in a second area identified through three MAPR deployments, reveals that neutrally buoyant hydrothermal plumes in the Arctic Ocean exhibit negative anomalies of both potential temperature and salinity, similar to plumes in the Atlantic. Plume water samples have been collected for Mn, methane, and He-3 to confirm the hydrothermal nature of the light scattering anomalies and provide some estimate of source strength. Manganese analyses will be completed by the time of this meeting. We plan to sample as far as 85 degrees E, where it is believed a volcanic eruption may have occurred in 1999 (Edwards et al., Nature, 2001). In his life and work, John Edmond encompassed many extremes, including latitude, altitude, temperature and depth. In many ways, his example inspired the present investigation, and will doubtless continue to inspire many more.
Baker Thomas E.
Connelly Douglas P.
Edmonds Henrietta N.
German Christopher R.
Graham David W.
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