Tag Archives: Indian Ocean

Pacific and Indian Ocean atoll islands are either stable or increasing in area

Virginie K. E. Duvat. A global assessment of atoll island planform changes over the past decades. WIREs Climate Change, Volume 10, Issue 1, 2018  https://doi.org/10.1002/wcc.557

Over the past decades, atoll islands exhibited no widespread sign of physical destabilization in the face of sea‐level rise. A reanalysis of available data, which cover 30 Pacific and Indian Ocean atolls including 709 islands, reveals that no atoll lost land area and that 88.6% of islands were either stable or increased in area, while only 11.4% contracted. Atoll islands affected by rapid sea‐level rise did not show a distinct behavior compared to islands on other atolls. Island behavior correlated with island size, and no island larger than 10 ha decreased in size. This threshold could be used to define the minimum island size required for human occupancy and to assess atoll countries and territories’ vulnerability to climate change. Beyond emphasizing the major role of climate drivers in causing substantial changes in the configuration of islands, this reanalysis of available data indicates that these drivers explain subregional variations in atoll behavior and within‐atoll variations in island and shoreline (lagoon vs. ocean) behavior, following atoll‐specific patterns. Increasing human disturbances, especially land reclamation and human structure construction, operated on atoll‐to‐shoreline spatial scales, explaining marked within‐atoll variations in island and shoreline behavior. Collectively, these findings highlight the heterogeneity of atoll situations. Further research needs include addressing geographical gaps (Indian Ocean, Caribbean, north‐western Pacific atolls), using standardized protocols to allow comparative analyses of island and shoreline behavior across ocean regions, investigating the role of ecological drivers, and promoting interdisciplinary approaches. Such efforts would assist in anticipating potential future changes in the contributions and interactions of key drivers.

Sea-level rapidly rising, not!

Nils-Axel Mörner, Biology and Shore Morphology: Keys to proper reconstruction of sea level changes, J Marine Biology and Aquascape . Doi: http://dx.doi.org/ 10.31579/ 26415143/JMBA.2019 /020

Biological criteria and shore morphology do not lie. Therefore, they are key elements for a proper reconstruction of sea level changes during the last 500 years. The elements have to be observed, understood, documented and dated. Having done so in the Maldives, Bangladesh, Goa (India), Fiji and New Caledonia, a new picture emerged. Sea level is not at all in a rapidly rising mode in the equatorial region, rather it is in opposed phase with the well-known climate changes of the Northern Hemisphere. The main driving force is changes in Earth’s rate of rotation as a function of planetary-solar interaction with the Earth’s systems.

Pacific and Indian ocean atoll islands stable or growing in size

Duvat, V. K. E. (2018). A global assessment of atoll island planform changes over the past decades. Wiley Interdisciplinary Reviews: Climate Change, e557. doi:10.1002/wcc.557

Over the past decades, atoll islands exhibited no widespread sign of physical destabilization in the face of sea-level rise. A reanalysis of available data, which cover 30 Pacific and Indian Ocean atolls including 709 islands, reveals that no atoll lost land area and that 88.6% of islands were either stable or increased in area, while only 11.4% contracted. Atoll islands affected by rapid sea-level rise did not show a distinct behavior compared to islands on other atolls. Island behavior correlated with island size, and no island smaller than 10 ha decreased in size. This threshold could be used to define the minimum island size required for human occupancy and to assess atoll countries and territories’ vulnerability to climate change. Beyond emphasizing the major role of climate drivers in causing substantial changes in the configuration of islands, this reanalysis of available data indicates that these drivers explain subregional variations in atoll behavior and within-atoll variations in island and shoreline (lagoon vs. ocean) behavior, following atoll-specific patterns. Increasing human disturbances, especially land reclamation and human structure construction, operated on atoll-to-shoreline spatial scales, explaining marked within-atoll variations in island and shoreline behavior. Collectively, these findings highlight the heterogeneity of atoll situations. Further research needs include addressing geographical gaps (Indian Ocean, Caribbean, north-western Pacific atolls), using standardized protocols to allow comparative analyses of island and shoreline behavior across ocean regions, investigating the role of ecological drivers, and promoting interdisciplinary approaches. Such efforts would assist in anticipating potential future changes in the contributions and interactions of key drivers.