Contrasting Inundation Patterns of Two Pacific Islands Under Sea-Level Rise

C. Kupp

Bachelor's Thesis (2015)

Department of Geosciences, The Pennsylvania State University

Coral atolls are coral reef islands that are found mostly in the Pacific and Indian Oceans and are vulnerable to rising sea levels due to their low elevation. Sea level may rise 0.5-2 meters by 2100, which could cause partial or complete submergence of atoll islands. Atolls support diverse ecosystems, including endangered species, as well as human populations. The loss of these islands would lead to the displacement of these populations. In this study, I investigated the impact of sea-level rise scenarios on Midway Atoll and compared it to the potential sea-level rise impact on the Hawaiian island of Oahu. To assess the effects of sea-level rise on these islands, I subtracted spatially constant amounts from a gridded topographic data set (a digital elevation model, or DEM). This method assumes that the islands' shape is static; thus, natural and anthropogenic processes that change the islands' topography are omitted. As sea level rises, more of the Midway Islands become inundated, and one member of the island group (Spit Island) disappears completely with 1.5 meters or more of sea-level rise. My results show that Oahu will be inundated to a lesser extent than the Midway Islands. However, important parts of Honolulu would likely be inundated if large amounts of sea-level rise were to occur. Our results reinforce existing work that suggests that inundation of atoll islands is likely to occur as sea level rises. Moreover, analysis of tide gauge data suggests that this flooding will be exacerbated by major storm events.

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