Climate Change and Sea Level Rise in the Pacific Islands 4 to 6 – February – 2013 Reducing Disaster Risk for a Healthy Pacific Honolulu, Hawai‘i

Sea Level Rise Impacts Increased Flooding and Erosion Will Threaten both Natural and Built environments. Critical public facilities and infrastructure will experience damage. Freshwater resources will be at particular risk due to intrusion of salt water from the ocean; secondary effects include the fouling of sanitary systems. Salinization will affect agricultural activity by decreasing the land area available for farming. Foraging areas and nursery habitat for many coastal species, are expected to diminish. Psychological effects of stress are likely to be gradual and cumulative.

Sea Level is Rising Since the early 1990s, the rate of globally averaged sea-level rise has been estimated to be 3.4 ± 0.4 mm per year based on satellite altimeter measurements. This is twice the estimated rate for the 20th century as a whole based on tide gauge measurements. Projections based on climate models and that do not include ice-sheet contributions are for an 18 to 59 cm rise in global sea level by 2100. Projections using "semi-empirical models“ yield higher estimates of global sea level rise, ranging from roughly 1 to 1.5 m by 2100. Adapted from Church et al., 2008

Sea Level Rise through Time and Space.

Actionable Information? The long term change in global mean sea level is not particularly meaningful. Low signal to noise ratio, means at least over the next generation three is as much if not more change attributable to inundation events as sea level trends. It is really about extremes, which generally occur when high tides combine with some non-tidal change in water level (e.g., tropical and extra-tropical storms, ocean mesoscale variability, and swell events from distant storms). It is probably more about the next few months than it is the next few decades. Sector-specific indicators/thresholds are required to make relevant connections between forcings and impacts.

Time-varying Extremes 1.0 ‘Return level curves’ for different SLR scenarios can be used to support the siting and design of new facilities and infrastructure as well as identification of new habitat. ‘Threshold frequency curves’ for different SLR scenarios can be used to asses the risk to existing facilities and infrastructure, as well as species and ecosystem response. …after Sweet, Merrifield, Marra

Each location is unique Extreme climatologies from tide gauges for each day of the year. Marra et al., 2012 Pago Pago Guam Honolulu The ratio of mean non-tidal residual to mean extreme amplitude for annual maxima. Merrifield et al., 2012

Time-varying Extremes 2.0 Honolulu 50-year Return Level – tide cycle. Midway Islands 50-year Return Level – storminess. …after Menendez, Sweet, Merrifield, Marra

Dr John J. Marra john.marra@noaa.gov For more on the PIRCA: Regional Climate Services Director, Pacific Region For more on the PIRCA: http://www.eastwestcenter.org/PIRCA