Physical Oceanography and Endeavour Regional Circulation Moorings ONC NEPTUNE Canada Science Steve Mihaly, ONC Rick Thomson, DFO

Overview of Ridge and Rift Valley Scale Ocean Dynamics In the region: ~5cm/s ambient flow + ~10cm/s oscillatory flows

Overview of Ridge and Rift Valley Scale Ocean Dynamics Along the ridge flanks, trapped clockwise rotary 4-day and diurnal oscillations

Overview of Ridge and Rift Valley Scale Ocean Dynamics Surface storm-generated inertial waves enhanced over the ridge

Overview of Ridge and Rift Valley Scale Ocean Dynamics Axially-oriented rectilinear semidiurnal currents in rift valley

Overview of Ridge and Rift Valley Scale Ocean Dynamics Hydrothermally-driven mean flow in the valley

Rotary Spectra from the crest of Juan de Fuca Ridge Day winter- intensified weather band, clockwise rotary 2.Diurnal Tidal band amplified 3-4 times from background, clockwise rotary 3.Inertial Band, episodic up to 70 cm/s 4.Semidiurnal Tidal Band 5.High frequency nonlinear interaction components.

The Effect of Ridge Topography on Diurnal, Inertial and Semidiurnal Currents Thomson et al. 2003

The Effect of Ridge Topography on Diurnal, Inertial and Semidiurnal Currents Thomson et al. 2003

650 MW from Main Endeavour Field Estimated total: 1500MW Southern deeper sites Mothra, MEF and HiRise Considerably more active than shallower Northern Sites, Salty Dawg and Sasquatch Measurements of cold inflow could be a valid proxy for vent fluxes Conceptual Model of Hydrothermally-modified rift valley circulation – “The Sea-Breeze Effect” Thomson et al. 2003

Observed daily mean currents from the axial valley North Central South Persistent inflow at deep southern and central sites can be used as a proxy for hydrothermal fluxes Variable at the shoaler less protected northern site Thomson et al. 2003

Observed daily mean currents from the axial valley North Central South Persistent inflow at deep southern and central sites Variable at the shoaler less protected northern site Currents do reverse about 10% of the time in response to larger scale disturbances which can flush the entire rift valley

ONC Endeavour Segment Layout

ERCM-NE Sept-2010Sept-2011 June-2012 ERCM-NW ERCM-SW ERCM-SE June-2012 Deployed but not connected July-2012 connection lost Deployment Timeline

200 mab 125 mab 50 mab 5 mab

Wilcock, Thomson and Mihaly

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Background - Regional Circulation and the Sea Breeze Effect ~1500MW of buoyancy flux drives a 2-5 cm/s deep inflow