Are Pacific Islands really being submerged in the Pacific?

http://www.sciencedirect.com/science/article/pii/S0921818110001013


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Global and Planetary Change
Volume 72, Issue 3, June 2010, Pages 234-246
doi:10.1016/j.gloplacha.2010.05.003 | How to Cite or Link Using DOI
Cited By in Scopus (5)
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The dynamic response of reef islands to sea-level rise: Evidence from multi-decadal analysis of island change in the Central Pacific

Arthur P. Webba, E-mail The Corresponding Author, Paul S. Kenchb, Corresponding Author Contact Information, E-mail The Corresponding Author
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a Pacific Islands Applied Geoscience Commission, SOPAC, Fiji
b School of Environment, The University of Auckland, Private Bag 92019, Auckland, New Zealand

Received 22 February 2010; Accepted 13 May 2010. Available online 21 May 2010.
Abstract

Low-lying atoll islands are widely perceived to erode in response to measured and future sea-level rise. Using historical aerial photography and satellite images this study presents the first quantitative analysis of physical changes in 27 atoll islands in the central Pacific over a 19 to 61 yr period. This period of analysis corresponds with instrumental records that show a rate of sea-level rise of 2.0 mm yr− 1 in the Pacific. Results show that 86% of islands remained stable (43%) or increased in area (43%) over the timeframe of analysis. Largest decadal rates of increase in island area range between 0.1 to 5.6 ha. Only 14% of study islands exhibited a net reduction in island area. Despite small net changes in area, islands exhibited larger gross changes. This was expressed as changes in the planform configuration and position of islands on reef platforms. Modes of island change included: ocean shoreline displacement toward the lagoon; lagoon shoreline progradation; and, extension of the ends of elongate islands. Collectively these adjustments represent net lagoonward migration of islands in 65% of cases. Results contradict existing paradigms of island response and have significant implications for the consideration of island stability under ongoing sea-level rise in the central Pacific. First, islands are geomorphologically persistent features on atoll reef platforms and can increase in island area despite sea-level change. Second, islands are dynamic landforms that undergo a range of physical adjustments in responses to changing boundary conditions, of which sea level is just one factor. Third, erosion of island shorelines must be reconsidered in the context of physical adjustments of the entire island shoreline as erosion may be balanced by progradation on other sectors of shorelines. Results indicate that the style and magnitude of geomorphic change will vary between islands. Therefore, island nations must place a high priority on resolving the precise styles and rates of change that will occur over the next century and reconsider the implications for adaption.

Keywords: Atoll island; sea-level rise; erosion; island migration; Pacific Ocean
Article Outline

1. Introduction
2. Field setting
3. Methodology
4. Results
5. Discussion
5.1. Net change in island area
5.2. Net vs gross island planform change
5.3. Styles of island planform change
5.3.1. Ocean shoreline adjustments
5.3.2. Lagoon shoreline adjustments
5.3.3. Island migration
5.3.4. Contraction, expansion and extension
5.4. Mechanisms driving change
5.4.1. Change in boundary conditions: sea level and climate
5.4.2. Anthropogenic modification
5.5. Implications for vulnerability assessments
6. Conclusions
References


http://tvnz.co.nz/national-news/nz-research-shows-pacific-islands-not-shrinking-3577883