Category Archives: Sea Level

Sea level rise nothing out of the ordinary

New York City will soon be underwater, Not!

Nils-Axel. The Illusive Flooding of New York CityJournal of Environmental Sciences Volume 1, Issue 2 

In media we often hear frightening stories of a sea in the progress of rapidly rising and flooding low-lying coasts and islands, and coastal cities like New York. This paper is devoted to a scientific evaluation of evidence-based facts versus fake news that violates facts and physical laws. It is a serious mistake to claim that global sea level is in a phase of rapid rise. Observationally based facts document a present changes in absolute (eustatic) sea level ranging between ±0.0 and +1.0 mm/yr. This poses no threats what so ever. In New York City, sea level is rising at a rate of +2.84 mm/yr, which would imply an additional rise in sea level by 23.3 cm by 2100, a modest rise that can be handled without problems. There also occur statements that sea level may raise by 1 m or more by 2100. All such claims represent fake news that does not concur with observational fact and violates physical frames of realism.

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.

Coastlines are expanding worldwide; Sea level not rising

Arjen Luijendijk, Gerben Hagenaars, Roshanka Ranasinghe, Fedor Baart, Gennadii Donchyts, Stefan Aarninkhof. The State of the World’s Beaches. Scientific Reports 8, 6641 (2018)

Coastal zones constitute one of the most heavily populated and developed land zones in the world. Despite the utility and economic benefits that coasts provide, there is no reliable global-scale assessment of historical shoreline change trends. Here, via the use of freely available optical satellite images captured since 1984, in conjunction with sophisticated image interrogation and analysis methods, we present a global-scale assessment of the occurrence of sandy beaches and rates of shoreline change therein. Applying pixel-based supervised classification, we found that 31% of the world’s ice-free shoreline are sandy. The application of an automated shoreline detection method to the sandy shorelines thus identified resulted in a global dataset of shoreline change rates for the 33 year period 1984–2016. Analysis of the satellite derived shoreline data indicates that 24% of the world’s sandy beaches are eroding at rates exceeding 0.5 m/yr, while 28% are accreting and 48% are stable. The majority of the sandy shorelines in marine protected areas are eroding, raising cause for serious concern.

Tuvalu is growing, not sinking

“The Pacific nation of Tuvalu—long seen as a prime candidate to disappear as climate change forces up sea levels—is actually growing in size, new research shows.” click here

South Pacific island shorelines expand

“the dramatic impacts of climate change felt on coastlines and people across the Pacific are still anecdotal” see discussion here

Michino Hisabayashi, John Rogan & Arthur Elmes. Quantifying shoreline change in Funafuti Atoll, Tuvalu using a time series of Quickbird, Worldview and Landsat data Journal GIScience & Remote Sensing Volume 55, 2018 Issue 3

Funafuti Atoll, Tuvalu is located in the southwestern Pacific Ocean, which has experienced some of the highest rates of global sea-level rise over the past 60 years. Atoll islands are low-lying accumulations of reef-derived sediment that provide the only habitable land in Tuvalu, and are considered vulnerable to the myriad possible impacts of climate change, especially sea-level rise. This study examines the shoreline change of twenty-eight islands in Funafuti Atoll between 2005 and 2015 using 0.65 m QuickBird, 0.46 m WorldView-2, and 0.31 m WorldView-3 imagery using an image segmentation and decision tree classification. Shoreline change estimates are compared to previous study that used a visual interpretation approach. The feasibility of estimating island area with Landsat-8 Operational Land Imager (OLI) data is explored using CLASlite software. Results indicate a 0.13% (0.35 ha) decrease in net island area over the study time period, with 13 islands decreasing in area and 15 islands increasing in area. Substantial decreases in island area occurred on the islands of Fuagea, Tefala and Vasafua, which coincides with the timing of Cyclone Pam in March, 2015. Comparison between the WorldView-2 shoreline maps and those created from Landstat-8 indicate that the estimates tend to be in higher agreement for islands that have an area > 0.5 ha, a compact shape, and no built structures. Ten islands had > 90% agreement, with percent disagreements ranging from 2.78 to 100%. The methods and results of this study speak to the potential of automated EoV shoreline monitoring through segmentation and classification tree approach, which would reduce down data processing and analysis time. With the growing constellation of high and medium spatial resolution satellite-based sensors and the development of semi or fully automated image processing technology, it is now possible to remotely assess the short and medium-term shoreline dynamics on dynamic atolls. Landsat estimates were reasonably matched to those derived from fine resolution imagery, with some caveats about island size and shape.

Only mm of sea level rise expected if Antarctic ice shelf melts

“The new study shows that a collapse of Larsen C would result in inland ice discharging about 4 mm to sea level, while the response of glaciers to George VI collapse could contribute over five times more to global sea levels, around 22 mm.” click here