1. I-IV: Physics & Biogeochemistry of Estuarine Turbidity Maxima
Estuarine Turbidity Maxima (ETM) are major features in both the North and South Channel of the Columbia River estuary.
Detailed understanding and ability to predict the ETM dynamics is necessary to address the variability and change of the biogeochemistry and ecosystem function in the lower Columbia River estuary, under the effects of climate and land/use. Phase 1 focus.
The biogeochemistry of the North and South channel ETMs shows important contrasts, the understanding of which matters for CMOP II initiatives in the role of lateral bays on carbon cycle, in estuarine hypoxia/acidification, and in M. rubra blooms. Phase 2 focus.
For numerical models to usefully address ETM biogeochemistry, they need to be skilled in representing circulation and trapping mechanisms at fine scales. Core CMOP focus.
salinity:
marine
estuarine
freshwater
sandy, vegetated
sandflats
mudflats

2. ETM resuspension and settling

3. Long-Term Scientific Goals Enabled by the Phase 1 ETM Initiative
To develop highly skilled numerical models that describe key ETM processes, in particular density structure, sediment trapping, and exchanges with the ocean and estuarine lateral bays. This will be accomplished by:
Measuring and characterizing the dominant physical processes that determine circulation, mixing and trapping in the North Channel, through a combination of long-term observations at endurance stations and of intense fortnightly observations in low and high-flow conditions.
Characterizing the turbulence structure along the North Channel, and computing eddy coefficients for incorporation in numerical models.
Rigorously benchmarking numerical models of circulation and sediment transport against the observed physical structure of the North Channel ETM, and exploring strategies for model improvements.
Conducting a “blind evaluation” of the predictive ability of numerical models to characterize ETMs at the mouth and in the South Channel of the estuary.

4. Phase 1: North Channel Laboratory
Instrumentation to deploy: In addition to endurance stations
Bottom node supporting ADV and CTD
Sigma profiler
Repeated vertical profiling from R/V, including V, T, S, O2, OBS, LISST 100, altimeter and turbulence profiles, supplemented by appropriate biogeochemistry sensors
Doppler radar measurements of surface velocity over N. Channel
Mobile profiles of water properties with an autonomous mobile AUV
Field operations (IOP): Two-week operations in May and September 2012
Expected Outcomes:
Improved understanding of flow and mixing in N. Channel
Refined parameterizations of bottom and interfacial stresses
Improved skill of circulation models

5. Long-Term Scientific Goals Enabled by the Phase 2 ETM Initiative
Develop and demonstrate detailed quantitative understanding and predictive ability of how the salinity intrusion and ETM formation influences biogeochemical factors, and demonstrate portability of theses predictive capabilities to the South Channel and entrance ETMs.
Determine and contrast the dynamics and biogeochemistry of the three Columbia River ETMs, and their role as bioreactors for transformation and removal of river-borne nutrients and biogenic inputs.
Predict climate change and land-use impacts on Columbia River ETMs, and integrate acquired understanding on regional efforts assessing or managing habitat and water quality for fisheries and aquaculture.

6. What is Needed to Achieve ETM Goals and Operations
People: Initial team:
Lead PIs: Tom Sanford and Byron Crump
Phase 1 PIs: Jim Lerczak (OSU), Murray Levine (OSU), Antonio Baptista (OHSU), Yvette Spitz (OSU), Craig McNeil (APL-UW), Gordon Farquharson (APL-UW), Fred Prahl (OSU)
Prior Studies: CRETM-LMER
Instruments and facilities:
Endurance stations
R/V Forerunner (scheduling limitations?) and access to UNOLS vessels
PI and CMOP instrumentation and methodologies
CMOP’s Virtual Columbia River modeling
Funding:
NSF from CMOP II
Contributions from involved PIs from personal grants
Extramural sources, especially for instrumentation

7. ETM resuspension and settling

8. Particle-attached bacterial production correlates with turbidity

9. ETM particles are aggregates, and can be >1mm in size

10. Unique ETM bacteria amid allochthonous communities (1997)

11. River
Ocean
Estuary

12. Diversity correlates with salinity, varies with season, repeats annually
Fortunato et al. In Prep

13. Marine Diatoms dominate 18S rRNA sequences in bottom waters.

14. Conceptual model of OM composition in Estuary