by Judith Curry
Pursuant to the controversy surrounding the last analysis of sea level rise from the University of Colorado, I spotted this article entitled “What will climate change and sea level rise mean for barrier islands?”
Some excerpts from the article:
A new survey of barrier islands published earlier this spring offers the most thorough assessment to date of the thousands of small islands that hug the coasts of the world’s landmasses.
During the 20th century, sea level has risen by an average of 1.7 millimeters (about 1/16 of an inch) per year. Since 1993, NASA satellites have observed an average sea level rise of 3.27 millimeters (about 1/8 of an inch) per year. A better understanding of how climate change and sea level rise are shaping barrier islands will also lead to a more complete grasp of how these dynamic forces are affecting more populated coastal areas.
The main points made in the article:
Every island is unique: Every island chain has a complex set of forces acting on it that underpin how islands form and how they’re likely to change over time. Barrier islands often develop in the mouths of flooded river valleys as sea level rises, but they can also form at the end of rivers as sediment builds up and creates a delta. Other important factors in barrier island formation include regional tectonics, sea level changes, climate, vegetation and wave activity. “Understanding how such forces impact barrier islands is the key to understanding how climate change will affect our coastlines,” noted Stutz.
Sea level rise can create or eliminate barrier islands: Paradoxically, gradual sea level rise can generate new barrier islands. Rising seas create shallow bays that develop barrier islands in the mouths of the bays along certain types of coastline. . . However, extremely rapid sea level rise — especially when coupled with decreases in sediment supply — can simply inundate islands causing them to break up and disappear. Islands are eroding rapidly along the Mississippi Delta, Eastern Canada and the Arctic for these reasons.
There are far more barrier islands than previously thought: A survey conducted by the same researchers tallied 1,492 barrier islands in 2001, but Stutz and Pilkey counted more than 2,149 this time. The difference: the researchers had access to higher-quality satellite imagery that covered a larger portion of the globe than they did last time.
Barrier islands cluster along tectonically calm coasts: Stable coasts, such as the eastern coast of the United States, tend to have wide, low relief areas with shallow estuaries that are conducive to barrier island formation. In contrast, continental margins near actively colliding plates, which generate earthquakes and volcanoes, produce fewer barrier islands.
Storms are key molders of barrier island shape: Storms tend to cause islands to retreat, carve new inlets that make them shorter and more numerous, and sometimes destroy them completely.
Arctic barrier islands are retreating the fastest: [M]elting of sea ice and the permafrost that buffers Arctic islands from waves have left them susceptible to constant pounding from storms.
Conclusions: NASA research shows that some coasts are experiencing sea level rise significantly faster than the global average of 3.27 millimeters (about 1/8 of an inch) per year, while other areas are experiencing slower rates of rise and even falling sea levels. “It would be nice if we could say we can predict exactly how a given island or island chain will react to rising sea levels or some other environmental change, but we’re simply not there yet for most islands, especially for many tropical islands where research dollars are scarce. We’re still a long way from being able to accurately model how an individual island will change as a result of climate change or even simple development pressure,” said Stutz.
JC comments: I am continuing to look for good resources on sea level rise and also guest posters on this subject. I liked this article because it underscores that the processes associated with sea level rise are fundamentally local. A massively rapid sea level rise such as that associated with the collapse of a major ice sheet would be a different story, but it seems that local geological processes and land use play a dominant role in local sea level rise.