O

ET

Central question:

How do plumes and currents interact above the Main Endeavour vent field to affect the measurement of hydrothermal

heat flux?

Approach:

Submarine volcanic heat flux and hydrography: perspectives from Northeast Pacific

observations, theory, and experiments

Proposed dissertation for Scott Veirs in the UW School of Oceanography

Endeavour Segment of the Juan de Fuca RidgeFlow Mow cruise (August, 2000) study site

HIGH BUOYANCY FLUX FIELDS:

SDF = Salty Dawg

HRF = High Rise

MEF = Main Endeavour

MF = Mothra

LOW BUOYANCY FLUX FIELDS:

C = Cirque

D = Dune

CB = Clam Bed

Q = Quebec

New or suspected fields Bathymetric contour interval: 100m

Main Endeavour hydrothermal vent fieldAxial valley bathymetry and key hydrographic observations

1 km

100mCTD

current

vents

1995

2000

Overview of current and hydrographic observations

MEF Sea floor

Ridge crest

m above MEF sea

floor

2210

1850

2100

Depth

250

50

150

200

100

2168

2070

2000

1900

1800

~350

ABE survey

CTD “ribbon”

CTD “curtain”

CTD “VOC”Upper control volume

Lower control volume

400m wide

800m long ~500m N&S

Hydrographic variability I

Hydrographic variability II

Currents in the MEF vicinity

~200m NE of MEF, 1995 ~1km S of MEF, 2000

depth/mab 2175/25 1900/300 2168/15 1968/215

Mean [cm/s] 1 to N 5 to SW 1 to N 5 to SSW

Max [cm/s] 5 67 9 13

q_adv

Sea floor

Ridge crest

250

50

150

200

100

mab 2200

1800

2100

Depth

q_sidesq_top

q_focused + q_diffuse + q_conduct

MEF heat flux calculation

q ~ AU, = ref + (z/Sz)(S-Sref)

Synthesis through “puff” models

Plume distributions in stratified, oscillatory cross flow

Current and surface waves

Oscillating jet

Lam and Xia, May, 2001

• Translate source with stepper moter• Concentration field from light sheet(s) and conductivity probeConductivity probe

Carriage

Stratified fluid

Interconnecting observation, theory, and experiment

Observations

Assumptions

Approaches

Products

CTD Currents MEF/sources

q_top +

q_sides

q_adv q variance

Puff model Lab workq~AU

definition and interpolation, A integration, U extrapolation; Scaling, dimensional analysis; Advection

dominates rotation

Frequencies with dominant spectral power:

Vertical coherence: 10-100m

Horizontal coherence: >50km

Other sources of data?

• rotary above the ridge crest

• rectified within the axial valley

• mean flows at both levels