Inconvenient Study: Sea level rise likely not to drown low-lying Pacific atolls

By H. Sterling Burnett

A new study published in Geology, the journal of the Geological Society of America, indicates even if seas continue to rise, low-lying islands and atolls, such as Kiribati, Tokelau, and Tuvalu and are likely to adapt to the rising seas rather than sink beneath them, contrary to climate model projections.

Lead author Megan Tuck, of the University of Auckland, teamed with Dr. Murray Ford, also from the University of Auckland, Professor Paul Kench, at Simon Fraser University in Canada, and Professor Gerd Masselink from the University of Plymouth in the UK to recreate the effect of rising seas using a scale model of tiny Fatato Island on the southeast rim of Funafuti Atoll in Tuvalu to test the ability of the real island to withstand predicted climate affects.

The researchers simulated higher sea levels and storm-generated waves up to 4m in a 20 meter (m)-long water chute to replicate real-world sea levels of 0.5 m and 1 m. During the experiment, Tuck, et al., used lasers to track changes in the model as simulated sea levels rose, finding the crest of the island—its highest ground—actually increased 1.13m height as higher sea levels and strong wave action washed sand and gravel inland. The experiment found lower lying areas could decline as the height of the crest increased, though that might not occur because lower lying ground on such atolls and islands are “are continually replenished by sediment from the surrounding reef.”

This paper confirms earlier research by the same scientists in which, using aerial photos beginning in 1943 to track changes to the 101 islands that make up the Tuvalu archipelago, they found the islands’ land area grew by 2.9 percent or approximately 73.5 hectares over the past 40 years, even as sea levels rose.

Tuck, the lead author, says these two sets of findings show low-lying islands are more dynamic and resilient than is commonly assumed. Tuck said in a news release discussing the Geology paper:

“Atoll islands do not sit inert on the reef, instead the gravel and sand they are made up of shifts on the reef itself so that the land changes in response to environmental conditions,”

SOURCE: SciMex press release

The paper in Geology (behind paywall)

Physical modelling of the response of reef islands to sea-level rise

Summary

Sea-level rise simulation suggests that low-lying Pacific islands such as those in Tuvalu, Tokelau and Kiribati are likely to adapt to the effects of climate change rather than simply sink beneath the waves, according to Kiwi researchers. The researchers created 1:50 scale replica of the uninhabited island of Fatato in Tuvalu and submitted the model to rising water levels and mock storm-generated waves. They found that the highest part of the island actually got higher as rising sea levels and strong wave action washed sand and gravel toward it. They say this shows the islands may be more resilient than we thought as they may be able to change shape to adapt to the climate.

Abstract:

Sea-level rise and increased storminess are expected to destabilize low-lying reef islands formed on coral reef platforms, and increased flooding is expected to render them uninhabitable within the coming decades. Such projections are founded on the assumption that islands are geologically static landforms that will simply drown as sea-level rises. Here, we present evidence from physical model experiments of a reef island that demonstrates islands have the capability to morphodynamically respond to rising sea level through island accretion. Challenging outputs from existing models based on the assumption that islands are geomorphologically inert, results demonstrate that islands not only move laterally on reef platforms, but overwash processes provide a mechanism to build and maintain the freeboard of islands above sea level. Implications of island building are profound, as it will offset existing scenarios of dramatic increases in island flooding. Future predictive models must include the morphodynamic behavior of islands to better resolve flood impacts and future island vulnerability.

Of course, our own Willis Eschenbach was way ahead of these guys.