RISE logoRiver Influences on Shelf Ecosystems (RISE)
Ocean Mixing Group
Oregon State University



The Columbia River brings buoyant fresh water to the Pacific Ocean, along with dissolved silicate and iron, crucial to phytoplankton growth.   The plume strongly-influences Oregon and Washington's dynamic coastal environments.

The Ocean Mixing Group seeks to understand the role of turbulence in mixing water of riverine and oceanic origin to produce the biochemical environment needed to fuel high biological productivity.  The 1-5 m thick plume issued from the Columbia mouth at ~2 m/s produces high velocity shear, a sharp, bore-like front, and generates large amplitude internal waves throughout the region.  Each of these play impoprtant roles in entraining nutrients into the plume.  Bottom boundary mixing may also bring Fe from plume-deposited sediments into the upwelling system.

plume front

Turbulence and Mixing in the Columbia River PlumeChameleon

Using Chameleon (our vertical microstructure profiler) and advanced shipboard acoustics (near-surface ADCP and 120 kHz echosounder), the Ocean Mixing Group obtains highly-resolved observations of velocity, density, turbulence, optics and acoustical backscatter within the plume and the coastal waters that receive it.  These observations reveal extremely sharp gradients in velocity and water properties that produce intense mixing and large-amplitude internal waves.


Shear-Driven Turbulence

  • As the plume leaves the river mouth, strong vertical gradients in velocity generate turbulence at the plume's base.

Plume Frontsechosounder plume front image

  • Plume fronts are extremely sharp (>0.5 m/s changes in 10 m)
  • highly nonhydrostatic
  • displace fluid downwards
  • may release large amplitude internal waves.
This image of 120 kHz acoustic backscatter reveals the bore-like character of the plume front just prior to the release of a packet of large amplitude internal waves.

Large Amplitude Internal WavesSAR image

  • large amplitude internal waves are ubiquitous.
  • displace fluid >30-m downward
  • may be unstable and generate turbulence
  • have associated biological response?
A paper describing the generation of large amplitude internal waves from the Columbia River plume front appeared in Nature 437, 400-403 (15 September 2005)

If you don't have electronic access to Nature, a reprint can be found here (download 500 kB pdf)


2004 Observations

Preliminary observations from the July 2004 experiment are available here.

Link to graduate student Levi Kilcher's RISE website

Participants

RISE (River Influences on Shelf Ecosystems) is a 5-year interdisciplinary study of the Columbia River plume, funded by the Coastal Ocean Program of the National Science Foundation.

RISE consists of participants from the Universities of Washington, California (Santa Cruz), OHSU and Oregon State University.

RISE participants from the Ocean Mixing Group include