Abstract. New marine geophysical data along the Macquarie Ridge Complex, the AustraliaPacific plate boundary south of New Zealand, illuminate regional neotectonics. We identify tectonic spreading fabric and fracture zones and precisely locate the Australia-Pacific plate boundary along the Macquarie Ridge Complex. We interpret a-•5-10 km wide Macquarie Fault Zone between the two plates along a bathymetric high that extends nearly the entire length of the Australia-Pacific plate boundary south of New Zealand. We conclude that this is the active Australia-Pacific strike-slip plate boundary. Arcuate fracture zones become asymptotic as they approach the plate boundary. A broad zone of less intense deformation associated with the plate boundary extends -50 km on either side of the Macquarie Fault Zone. Marine geophysical data suggest that distinct segments of the plate boundary have experienced convergence and strike-slip deformation, although teleseismic evidence overwhelmingly indicates strike-slip motion along the entire surveyed boundary today. The McDougall and southernmost Puysegur segments show no evidence for past underthrusting, whereas data from the Macquarie and Hjort segments strongly suggest past convergence. The present-day strike-slip plate boundary along the Macquarie Ridge Complex coincides with the relict spreading center responsible for Australia-Pacific crest in the region. Our conceptual model for the transition from seafloor spreading to strike-slip motion along the Macquarie Ridge Complex addresses the decreasing length of spreading center segments and spacing between fracture zones, as well as the arcuate bend of the fracture zones that become asymptotic to the current transform plate boundary.

In New Zealand, climate change impacts have already been observed, and will increase in future decades. Average air temperature is predicted to warm by 2.1°C by 2090 for a mid-range IPCC scenario (A1B), with larger increases possible for some IPCC scenarios with higher rates of future emissions. Sea-level rise projections range between 0.18 -0.59 m by 2100, based on six IPCC future emission scenarios excluding future rapid dynamical changes in polar ice-sheet flow. Global surface ocean pH is predicted to decrease by an additional 0.14 -0.35 units by 2100, with a similar decrease expected in New Zealand waters. Rainfall is predicted to change significantly, with increased precipitation in the west, and reduced precipitation in the east, and more intense rainfall events. Increasing temperature is likely to result in species' range shifts southward and upward, and mortality during extreme heat events. Ocean acidification is expected to cause declines in carbonate communities, with cold water communities predicted to decline first due to a lower aragonite saturation horizon in cold waters. Sea-level rise is likely to impact on coastal biota, reducing coastal habitats, changing inundation patterns, and increasing vulnerability to storm surges and tides. Changes in storm and rainfall intensity are predicted to increase disturbance to terrestrial and aquatic communities. Areas with increased precipitation will amplify rates of disturbance, erosion and sedimentation into aquatic, estuarine and coastal ecosystems, while areas with low precipitation will experience increased fire risk. In New Zealand, climate change projections are being integrated into management, including increasing protection and improving management of coastal habitats. Contributing to a global reduction in greenhouse gas emissions, New Zealand is the first country to include forestry in their Emissions Trading Scheme, already positively affecting biodiversity by reducing deforestation.

a b s t r a c tThis paper describes the first use of a stochastic cyclone model (SCM) to quantify the extreme significant wave height from tropical cyclones across the Southwest Pacific Ocean. The median extreme significant wave heights across the entire SW Pacific Ocean were 7.5, 10 and 11 m for annual exceedance probabilities (AEPs) of 0.1, 0.02 and 0.01 respectively. Maximum significant wave heights in the region were approximately 1.5 times these values for the same AEP. Tables of extreme significant wave heights are provided for selected inhabited locations. The SCM was used to quantify the effects of the El Niño-Southern Oscillation (ENSO) on extreme significant wave heights, and also the effects of projected climate change on cyclone intensity and frequency of occurrence. West of the International Dateline in the region of the Vanuatu archipelago, the extreme cyclone wave climate was relatively consistent during all phases of the ENSO cycle, but highest during El Niño. Cyclone formation and propagation eastward of the Dateline are more likely to occur during El Niño conditions, however these cyclones tended to be more intense, particularly during extreme El Niño events, leading to a higher long-term extreme wave climate in the eastern SW Pacific, despite the relatively low cyclone observation rate there. Simulations of climate change cyclone intensity increases of 10-20% of the most intense cyclones (categories 4 and 5) along with 10-20% reduction in number of cyclones indicated little change in extreme significant wave heights for low-occurrence AEPs of 1/20 or less. These changes were much less than induced by present-day ENSO variability, suggesting that future changes in extreme wave climate will be sensitive to climate change influences on the frequency and intensity of ENSO events. These results are significant in the light of indications that the frequency of extreme El Nino events might double in response to greenhouse warming.

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A technique to produce high-water alerts from coinciding high astronomical tide and high mean sea level anomaly is demonstrated for the Pacific Islands region. Low-lying coastal margins are vulnerable to episodic inundation that often coincides with times of higher-than-normal high tides. Prior knowledge of the dates of the highest tides can assist with efforts to minimize the impacts of increased exposure to inundation. It is shown that the climate-driven mean sea level anomaly is an important component of total sea level elevation in the Pacific Islands region, which should be accounted for in medium-term (1-7 months) sea level forecasts. An empirical technique is applied to develop a mean sea level-adjusted high-water alert calendar that accounts for both sea level components and provides a practical tool to assist with coastal inundation hazard planning and management.