Category Archives: Sea Level

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.

North Atlantic sea level is falling

“Despite stressing global sea level rise is worrisome and due to anthropogenic warming, Chafik et al. (2019) report a distinct cooling trend in the North Atlantic that coincides with a transition to falling regional sea levels since 2004.” click here

Sea-level rise absent in Maldives, development expanding…

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.

Bangkok Thailand will soon be underwater, only 5,000 years to go….

“At current sea level rise rates, it will take at about 5,000 years for Bangkok to drown. Same amount of time since these artifacts were made.” click here

Reef islands can adapt to sea-level rise

Megan E. Tuck, Paul S. Kench, Murray R. Ford, Gerd Masselink. Physical modelling of the response of reef islands to sea-level rise, Geology (2019) 47 (9): 803-806. https://doi.org/10.1130/G46362.1

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.

Coral reefs benefit from rising sea levels

Long-term observation of coral reefs indicate rising sea levels “not only promoted coral cover” but also “limit damaging effects of thermally-induced bleaching”

B. E. Brown, R. P. Dunne, P. J. Somerfield, A. J. Edwards, W. J. F. Simons,
N. Phongsuwan, L. Putchim, L. Anderson & M. C. Naeije. Long-term impacts of rising sea temperature and sea level on shallow water coral communities over a ~40 year period. Scientific Reports, volume 9, 2019

Effects of combined rising sea temperature and increasing sea level on coral reefs, both factors associated with global warming, have rarely been addressed. In this ~40 y study of shallow reefs in the eastern Indian Ocean, we show that a rising relative sea level, currently estimated at ~11 mm y−1, has not only promoted coral cover but also has potential to limit damaging effects of thermally-induced bleaching. In 2010 the region experienced the most severe bleaching on record with corals subject to sea temperatures of >31 °C for 7 weeks. While the reef flats studied have a common aspect and are dominated by a similar suite of coral species, there was considerable spatial variation in their bleaching response which corresponded with reef-flat depth. Greatest loss of coral cover and community structure disruption occurred on the shallowest reef flats. Damage was less severe on the deepest reef flat where corals were subject to less aerial exposure, rapid flushing and longer submergence in turbid waters. Recovery of the most damaged sites took only ~8 y. While future trajectories of these resilient reefs will depend on sea-level anomalies, and frequency of extreme bleaching the positive role of rising sea level should not be under-estimated.