Interdecadal Pacific Oscillation (IPO): a mechanism for forcing decadal coastal scale change on the northeast coast of New Zealand? Journal Paper
- Author
- de Lange, W.P.
- Year
- 2001
- Journal / Source
- Journal of Coastal Research
- Publisher / Organisation
- Coastal Education & Research Foundation, Inc.
- Volume
- Special Issue 34
- Pages
- 657-664
- Keywords
- El Nino, Coasts, Sea level, La Nina, Storm surges, Sea level rise, Beaches, Oceans, Climate change, Storms
- Summary
- The IPO is a combination of changes in oceanic and atmospheric circulation over the North Pacific Ocean, that have been proposed as the cause of climatic regime shifts at intervals of 20-35 years. Via a series of teleconnections (atmospheric and oceanic links), the IPO may also produce similar climatic shifts in the Equatorial and South Pacific Ocean, Indian Ocean and the North Atlantic Ocean. The observed climatic shifts in the North Pacific have involved decadal scale changes in precipitation, storminess, prevailing wind direction, sea surface temperature, and storm surge frequency. Similar decadal scale changes around the New Zealand coast may be associated with the IPO. On the New Zealand coast, the IPO may affect sea level, frequency of storms, nearshore winds and currents, and the wave climate. This occurs primarily by modulating the frequency and magnitude of the El Niño-Southern Oscillation. ENSO extremes (El Niño and La Niña) occur at interannual scales, and have previously been linked to coastal change on the New Zealand and North American coasts. The mechanisms whereby these changes occur include changes in sea level, prevailing wind direction, storm frequency and wave climate. These changes have been viewed as minor oscillations about long-term trends, so that their impacts tend to be averaged out over time. However, the IPO may cause a higher incidence of one extreme for periods of 20-35 years. Hence, the IPO may drive decadal scale changes by favouring either erosive or accretionary conditions. For the northeast coast of New Zealand, the IPO may be responsible for a reduced incidence of coastal erosion between ∼1976 and the present, compared to between 1948 and 1976. The IPO appears to be a natural phenomenon, so phase reversals are likely continue for the foreseeable future.
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