Properties and Dispersal of a Hydrothermal Plume in a Weakly Stratified
Under-Ice Environment
Abstract
The Aurora vent field (82°53.83’ N, 6°15.32’ W) is located in the weakly
stratified Arctic Ocean under perennial ice cover at the western edge of
the ultraslow-spreading Gakkel Ridge, the slowest spreading mid-ocean
ridge on Earth. Here, we report data on the dispersal of the proximal
hydrothermal plume in this extreme environment. The hydrothermal plume
is of unusual dimensions, with a small horizontal, but large vertical
extent, which is caused by the hydrography of the Arctic Ocean. Water
column parameters such as turbidity and redox potential show a highly
variable but horizontally confined non-buoyant plume. Dissolved iron
(dFe), manganese (dMn), δ3He, and methane (CH4) all show distinct
enrichments in the hydrothermal plume relative to background deep-water,
but relatively low peak concentrations due to the dilution over a
vertical extent of over 500 m. Plume particle samples exhibit elevated
Fe/Al ratios consistent with Fe-oxyhydroxide precipitation close to the
vent, whereas particulate Mn/Al ratios do not reveal any complementary
pMn enrichments in the proximal plume. Positive correlation between
Fe/Al, and several other element/Al ratios (e.g. P, V, As) are
consistent with scavenging of these elements onto Fe-hydroxide plume
particles and removal into the underlying sediments. Surface sediment
samples collected close to Aurora reveal highly elevated concentrations
of hydrothermally-sourced elements in the immediate vicinity of the
vent-site. For example, proximal surface sediments contained up to 8222
mg kg-1 Cu, whereas Cu concentrations in core tops a few kilometers away
from the site were much lower (<50 mg kg-1).