Good news: rising seas might not cover these Pacific islands

Summary: The press reports often and in detail about climate and climate science, with two exceptions. They tend to hide from the public the exciting progress in understanding climate (they stick to the myth that “the science is settled”). Equally sad, they ignore the (too rare) good news about climate and the environment. Many posts here have covered the former; today we look at some of good news.

The science is telling us it is already too late for us. And so we have been asking the global community to say, OK, think about the future, the speculation of what will happen. But don’t forget those who are already affected, those for whom it is already too late, we are working together collectively with the countries in the like situation, Tuvalu, the Marshall Islands, the Maldives, where the impact of climate change is about total annihilation of our nations.

— Anote Tong (President of Kiribati), interview on CNN, 8 June 2014

Kiribati, only 1-2 meters above sea level

Content

“Warming may not swamp islands”
Some of the supporting peer-reviewed research
Rising sea levels, past and future
For More Information

(1) Good news!

“Warming may not swamp islands“, Christopher Pala (writer), Science, 1 August 2014 — Gated. Excerpt:

… a song blasting over Kiribati’s state radio envisions an apocalypse for this fishhook-shaped atoll halfway between Honolulu and Fiji: “The angry sea will kill us all.”

… Many scientists quietly demur.

No doubt, the sea is coming: In a 2013 report {AR5}, the U.N. Intergovernmental Panel on Climate Change predicted that global sea levels will rise up to 1 meter by 2100. But recent geologic studies suggest that the coral reefs supporting sandy atoll islands will grow and rise in tandem with the sea. The only islanders who will have to move must do so for the same reason as millions of people on the continents: because they live too close to shore.

Paul Kench, a geomorphologist who now heads the University of Auckland’s School of Environment in New Zealand, was the first to question the dire forecasts for Kiribati and similar island nations. In 1999, the World Bank asked him to evaluate the economic costs of sea-level rise and climate change to Pacific island nations. Kench, who had been studying how atoll islands evolve over time, says he had assumed that a rising ocean would engulf the islands, which consist of sand perched on reefs. “That’s what everyone thought, and nobody questioned it,” he says. But when he scoured the literature, he could not find a single study to support that scenario.

So Kench teamed up with Peter Cowell, a geomorphologist at the University of Sydney in Australia, to model what might happen. They found that during episodes of high seas—at high tide during El Niño events, which raise sea level in the Central Pacific, for example — storm waves would wash over higher and higher sections of atoll islands. But instead of eroding land, the waves would raise island elevation by depositing sand produced from broken coral, coralline algae, mollusks, and foraminifera. Kench notes that reefs can grow 10 to 15 millimeters a year — faster than the sea-level rise expected to occur later this century. “As long as the reef is healthy and generates an abundant supply of sand, there’s no reason a reef island can’t grow and keep up,” he argues.

It’s not new news. New Scientist wrote about this four years ago: “Shape-shifting islands defy sea-level rise“, 2 June 2010 — Excerpt:

For years, people have warned that the smallest nations on the planet – island states that barely rise out of the ocean – face being wiped off the map by rising sea levels. Now the first analysis of the data broadly suggests the opposite: most have remained stable over the last 60 years, while some have even grown.

Despite this, Kench and Webb found that just four islands have diminished in size since the 1950s. The area of the remaining 23 has either stayed the same or grown.

Paul Kench at the University of Auckland in New Zealand and Arthur Webb at the South Pacific Applied Geoscience Commission in Fiji used historical aerial photos and high-resolution satellite images to study changes in the land surface of 27 Pacific islands over the last 60 years. During that time, local sea levels have risen by 120 millimetres, or 2 millimetres per year on average.

Journalists nearer ground zero for sea level rising have covered this story:

“NZ research shows Pacific islands not shrinking“, TV New Zealand, 3 June 2010
“Human interference real threat to Pacific atolls“, New Zealand Herald, 4 December 2013 — We’re wrecking the biosphere in far more rapid and immediate ways than CO2 emissions.

(2) Some of the supporting peer-reviewed research

(a) “The dynamic response of reef islands to sea level rise: evidence from multi-decadal analysis of island change in the central pacific“, Arthur P. Webb and Paul S. Kench , Global and Planetary Change, June 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 year period. This period of analysis corresponds with instrumental records that show a rate of sea level rise of 2.0 mm/year 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 hectares. 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.

(b) “Coral colonisation of a shallow reef flat in response to rising sea level: quantification from 35 years of remote sensing data at Heron Island, Australia“, J Scopélitis et al, Coral Reefs, December 2011 — Gated. Abstract:

Observations made on Heron Island reef flat during the 1970s–1990s highlighted the importance of rapid change in hydrodynamics and accommodation space for coral development. Between the 1940s and the 1990s, the minimum reef-flat top water level varied by some tens of centimetres, successively down then up, in rapid response to local engineering works. Coral growth followed sea-level variations and was quantified here for several coral communities using horizontal two-dimensional above water remotely sensed observations.

… This unique time-series displays a succession of ecological stage comprising a ‘catch-up’ dynamic in response to a rapid local sea-level rise in spite of the occurrences of the most severe bleaching events on record (1998, 2002) and the decreasing calcification rates reported in massive corals in the northern part of the Great Barrier Reef.

(c) “Evidence for coral island formation during rising sea level in the central Pacific Ocean“, Paul S. Kench et al, Geophysical Research Letters, 10 February 2014 — Excerpt:

This new evidence from the Pacific is consistent with evidence from the central Indian Ocean and combined with other studies indicates that reef islands can form at various stages of sea level change. Our findings suggest that island formation is complex and is likely dependent on the site specific temporal relationship between reef growth and sea level (which controls the depth window for effective wave entrainment and transport of sediments) and available sediment supply as previously proposed from evidence in the other reef regions.

… The results also imply Jabat should remain stable in the face of projected sea level rise over the next century as (i) the conglomerate platform provides a resistant core to the island and (ii) rising sea level will raise the elevation of the process regime to levels at which the island was formed during the mid-Holocene highstand.

(3) Rising sea levels since the end of the ice age & in the 21st C

It’s vital to remember that climate always changes. Just as the atmosphere has been warming for two centuries (humanity causing over half of the warming since 1950), sea levels have been rising for thousands of years — as shown by this graphic prepared by Robert Rohde of the Berkeley Earth project (bio here), from Wikimedia Commons.

It shows the rise in meters. During the past century the oceans have been rising roughly 2-3 millimeters per year, driven by the warming of the past two centuries (with humanity responsible for more than half the warming since 1950). For details see Chapter 13 of the IPCC’s Assessment Report #5, working group 1.

AR5 looks to the future

It is very likely that the rate of global mean sea level rise during the 21st century will exceed the rate observed during 1971–2010 for all Representative Concentration Pathway (RCP) scenarios due to increases in ocean warming and loss of mass from glaciers and ice sheets.

The IPCC expresses its conclusions and forecasts in terms of confidence. Very likely means 90-100% certain.