Posted on 24 May 2017

Tracking Tasman Bay

Over the next 2 weeks, 14 drifters will monitor how water circulates in Tasman Bay, providing insights into issues such as where river sediment and nutrient plumes end up.

“The drifters are buoys with a sensor that measures sea surface temperature and a GPS tracker that transmits its location every 10 minutes,” say Brett Grant, a Marine Physics Technician at NIWA, who deployed the drifters on Monday (22 May).

The drifters have a drogue, an ‘underwater sail’ that matches the drifter to the water’s speed rather than being blown around by the wind.

“The results help us work out how water moves in the bay, and how it exchanges with water outside the bay. We combine this with computer models to give as complete a picture as possible.

“This helps us answer questions like ‘Where does nutrient-laden river water end up?’, ‘Where can we locate aquaculture facilities so to get best production for least impact?’, and ‘Where might sediment from dredging resettle?’.”

This research is part of the Stressor footprints and dynamics project, which uses observational data to define the ‘footprint’ of materials that stress marine systems, eg contaminants, nutrients and sediment. The footprint includes where the materials are and how they flow through surrounding waters.

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Stressor footprints and dynamics
Stressor footprints and dynamics

We investigated how coastal waters and oceans mix and transport materials that can stress marine ecosystems.