Science Centres: Oceans

Offshore exploration

This shows the modelled mean currents off the east coast of the North Island. The colours show the speed of the currents. The arrows show both direction and speed (the longer the arrow, the faster the current).
The main feature is the East Cape Current which flows down the east coast and turns off eastward near 42° S (south of the Wairarapa coast). Here it joins current from Cook Strait giving the strongest mean currents of over 30 centimetres per second (shown in red). Part of the flow recirculates forming the Wairarapa eddy (W).
One of the factors NIWA has investigated for MED is the strength of these mean currents relative to the strength of currents produced by tides.

Faced with the depletion of the Maui gas field, the Government is actively promoting gas exploration in parts of New Zealand’s offshore petroleum basins that have received comparatively little attention before.

The Ministry of Economic Development (MED) is commissioning offshore seismic surveys of these areas before inviting companies to bid for exploration permits. MED has contracted NIWA to provide information on the winds, waves, and currents that could be encountered by survey and exploration vessels.

To carry out this work, NIWA uses a variety of data sources. Observations of winds and waves from ships provide a valuable resource. In some areas, NIWA has used data from moorings previously deployed offshore to measure winds, currents, or waves for extended periods of time. However, the ocean is vast and most areas don’t have such measurements. To fill some of these gaps, NIWA has modelled what the waves around New Zealand were like between 1979 and 1998 using 20 years of modelled wind data. This means we can calculate long-term wave statistics, such as mean and extreme wave heights, for different parts of the ocean around New Zealand. For currents and tides, we have supplemented observations with information from an ocean circulation model and a tide model respectively.

To find out more about NIWA’s wave modelling: www.niwa.co.nz/rc/prog/chaz/news/waves