Monterey Bay Aquarium Research Institute
CANON Initiative
Case study:
Mesoscale eddies

Presented by Matthew Church and Alexandra Worden

Research topic and goals

The research on mesoscale eddies is not about studying the evolution of eddies but rather getting a low-time-scale snapshot of their interactions with each other. The surrounding ocean has implications for figuring out how ocean circulation changes as a result of climate change, which may affect biogeochemistry over vast areas.

Our understanding of how mesoscale processes influence the open sea is limited by inadequate sampling in time and space. Sampling is done by satellites, ships, moorings, gliders/autonomous underwater vehicles (AUVs), and floats, but it does not include in-situ (analyzing samples in real time).

The experiment is to send out the AUVs to get a decent picture of where the eddies are (in 3D?), then send the ship to the appropriate area and sample the features. Another task is to do shipboard (e.g. perturbation) experiments to get additional information. It is important to think critically about ways to make common shipboard experiments autonomous.

The research focuses on open ocean mesocale eddies and the subsequent effect on surrounding biogeochemistry. The research constraints will be short time scales (three-month project, monthly AUV surveys , ship support)

Current autonomous samplers

The samples will be preserved for 30 days at 26 degrees Celsius.

The sampling will depend on the specific feature of the ocean eddy and its complexity. The inter-eddy transition zone is likely going to be most heterogeneous and will require increased sampling.

There is a need to get the number of samples that will yield a statistically-significant picture of each eddy.This will be difficult to achieve in the inter-eddy transition zone where variances between samples will be high.

Scientists are more adept at measuring physical rather than biological effects of eddies. Shipboard sampling at 15 kilometer intervals can miss two-thirds of variability in carbon dioxide (CO2) and temperature. Light varies with depth exponentially, so eddies could have a major effect on productivity by moving organisms vertically.

For each site, 100 to 1,000 samples is the optimal amount (for site characterization in autonomous mode).

Last updated: Aug. 17, 2010