Sixty-Six Years of Island Shoreline Dynamics on Jaluit Atoll, Marshall Islands

According to a conventional narrative, tropical islands are eroding away due to rising seas and increasingly devastating storms. Not really, according to the recent work of Ford and Kench (2016).

Writing as background for their study, the two researchers state that low-lying reef islands are “considered highly vulnerable to the impacts of climate change,” where an “increased frequency and intensification of cyclones and eustatic sea-level rise [via global warming] are expected to accelerate shoreline erosion and destabilize reef islands.” However, they note that much remains to be learned about the drivers of shoreline dynamics on both short- and long-term time scales in order to properly project future changes in low-lying island development. And seeking to provide some of that knowledge, the pair of New Zealand researchers set out to examine historical changes in 87 islands found within the Jaluit Atoll (~6°N, 169.6°E), Republic of the Marshall Islands, over the period 1945-2010. During this time, the islands were subjected to ongoing sea level rise and the passage of a notable typhoon (Ophelia, in 1958), the latter of which caused severe damage with its >100 knot winds and abnormal wave heights.

So what did their examination reveal?

Analyses of aerial photographs and high-resolution satellite imagery indicated that the passage of Typhoon Ophelia caused a decrease in total island land area of approximately five percent, yet Ford and Kench write that “despite [this] significant typhoon-driven erosion and a relaxation period coincident with local sea-level rise, [the] islands have persisted and grown.” Between 1976 and 2006, for example, 73 out of the 87 islands increased in size, and by 2010, the total landmass of the islands had exceeded the pre-typhoon area by nearly 4 percent.

Such observations, in the words of Ford and Kench, suggest an “alternative trajectory” for future reef island development, and that trajectory is one of “continued island expansion rather than one of island withering.” And such expansion is not just limited to Jaluit Atoll, for according to Ford and Kench, “the observations of reef island growth on Jaluit coincident with sea level rise are broadly consistent with observations of reef islands made elsewhere in the Marshall Islands and Pacific (McLean and Kench, 2015).” Given as much, it would thus appear that low-lying islands are not as vulnerable to climate change as previously thought.

 

Reference

Ford, M.R. and Kench, P.S. 2016. Spatiotemporal variability of typhoon impacts and relaxation intervals on Jaluit Atoll, Marshall Islands. Geology 44: 159-162.

McLean, R.F. and Kench, P.S. 2015. Destruction or persistence of coral atoll islands in the face of 20th and 21st century sea level rise? WIRES Climate Change 6: 445-463.