Tuvalu is one of many ring shaped islands in that region. They are sitting atop extinct volcanoes where the rim of the volcano forms the island and the caldera forms a natural lagoon. The reason that the local rise in recorded water levels is higher than average is due to erosion.A quick look-up on GoogleScholar came up with these studies:
– With the post-shield quiescence in volcanic activity, destructive processes gradually take over…Reef growth and/or uplift may also prolong the island’s lifetime above the waves. The ultimate fate of most islands, however, is to be drowned through subsidence and/or truncation by marine erosion.
– We calculated that, due to coastal erosion, the island (Corvu) has lost a volume of 6.5 ± 2.7 km3 corresponding to a reduction of roughly 80 % of its surface area since it was first built.
What stands out in these and other studies is that the porous volcanic substrate of the islands is particularly vulnerable to subsurface erosion from seawater. And the third study above indicates that due to the nature of the rock around calderas ring-islands collapse rapidly after their formation. There is no doubt then that the islands will disappear in the long run, not from warm conditions but from natural internal erosion.
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Tuvalu is one of many ring shaped islands in that region. They are sitting atop extinct volcanoes where the rim of the volcano forms the island and the caldera forms a natural lagoon. The reason that the local rise in recorded water levels is higher than average is due to erosion.A quick look-up on GoogleScholar came up with these studies:
https://www.sciencedirect.com/science/article/abs/pii/S0012825213001736
– With the post-shield quiescence in volcanic activity, destructive processes gradually take over…Reef growth and/or uplift may also prolong the island’s lifetime above the waves. The ultimate fate of most islands, however, is to be drowned through subsidence and/or truncation by marine erosion.
https://www.sciencedirect.com/science/article/abs/pii/S0012821X07004669
– These islands are constituted of very porous pyroclastic deposits, andesitic or basaltic lava flows, allowing significant water infiltration
https://esurf.copernicus.org/preprints/esurf-2022-18/
– We calculated that, due to coastal erosion, the island (Corvu) has lost a volume of 6.5 ± 2.7 km3 corresponding to a reduction of roughly 80 % of its surface area since it was first built.
What stands out in these and other studies is that the porous volcanic substrate of the islands is particularly vulnerable to subsurface erosion from seawater. And the third study above indicates that due to the nature of the rock around calderas ring-islands collapse rapidly after their formation. There is no doubt then that the islands will disappear in the long run, not from warm conditions but from natural internal erosion.