Karen BemisRuss Light, Peter Rona, Darrell Jackson, Guangyu Xu

12/1/12 NEPTUNE Canada Endeavour Workshop

COVIS is at the Endeavour site on the NEPTUNE Canada Observatory showing cable system.

COVIS’s beam coverage over the bathymetry of the Grotto vent cluster in the Main Endeavour Field.

Distance (m)

Depth (m)

Distance (m)

COVIS

MEF instrument site

North Tower

The COVIS systemThe sonar sits atop a 4 m tripod platform with 3 motors to control orientations

Products3D images of plume(s)Plume bending

characterizationVertical velocity and

volume fluxMaps of diffuse flow

distribution

Products of the basic software turned over to NEPTUNE Canada

plume quick look diffuse flow quick look

Bathymetry from MBARI 2008 cruise thanks to D. Clague.

Fancy Work

Preliminary estimates of plume bending

Estimating the plume centerline uses Gaussian fitting on horizontal slices

The centerline inclination (bending from vertical) and declination (compass direction of bending) vary over time

Inclination Declination

Periodogram of Angles

by Guangyu Xu

by Jeff Rabinowitz

Spectral analysis of the  plume bending data and the currents from RSN-N support both tidal and other forcing.

Plume bending Spectrum

• Dominant (blue) peaks in plume bending angle spectrum match ambient currents and modeled semi-diurnal tides.

• One secondary peak may be found in ambient current as well; another is unique to the plume.

• Best explanation of secondary peaks is rift valley inflow

Ambient current

Across Rift Valley

Along Rift Valley

Pressure

data from S. Mihaly Thomson et al, 2005 JGR

Plume bending

Changes in plume bending patterns2010

2010

2011

COVIS mapping mode focuses on detecting regions with diffuse flow based on decorrelation.

spatial distributions of diffuse flow change in area over time

a map

by Peter Lin, undergraduate intern, summer 2011

Diffuse flow influenced by tidal cycle: searching for mechanisms

2011-2012 area estimates Strong semi-diurnal peak

Oct 2010 area estimates

250

0

Area (m2)

10/2/11 1/1/12Time (days)

220

0

Area (m2)

10/1/10 10/26/10Time (days)

But not in Oct 2010. why?

The Doppler mode quantifies vertical flow rates and estimates volume flux.

preliminary analyses• detection of plumes• estimation of vertical velocity and volume flux

Mean Volume Flux Mean Vertical Velocity

volume flux2010 to 2012

Plume Over North Tower Plume Over In-Situ Site