Sea Level Rise Projection Map – Noumea

New Caledonia is a French overseas territory in the South Pacific. Like many island states, its inhabitants and unique species are increasingly threatened by rapid sea level rise. 

Earth.Org has mapped what extreme flooding could look like by 2100 to illustrate the need for action.

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Ouvéa, nicknamed “the island closest to paradise”, is considered to be one of the most beautiful atolls of the New Caledonian and Pacific group of islands. The archipelago has a population of about 259,000, 100,237 of whom live in the capital, Noumea. They are surrounded by varied microclimates, hidden in plains, lagoons and mountains, allowing a multitude of unique species to flourish.

Rising sea levels are accelerating coastal erosion, endangering habitats and forcing local tribes to adapt their daily lives. Although many homes are within reach of the creeping waters, crops are still safe. When this is no longer the case, survival on the islands will become seriously difficult.

Recent studies have highlighted a possible sea level rise of 1 to 2 meters by 2100 with current emission patterns. A single meter means the loss of 1.7 to 2% of the island’s land surface (out of a total of 54% that is not mountains or forests). Erosion is also eroding New Caledonia’s coastline, and if the inhabitants do not begin to defend themselves soon, they may lose a lot of space over the next few decades.

Today, land loss threatens to displace the tribes from the seafront and disrupt their social fabric. The island’s many different cultures will have to work together if they are to adapt to the rising waters, which means awareness and communication are key. This is also true for the global community’s confrontation with climate change as a whole.

Earth.Org has mapped the serious flooding that could occur by 2100 in New Caledonia if we do not reduce emissions. The time to act is now.

Sea level rise projections by 2100 for two scenarios with the amount of rise in meters indicated (mild = 2m; extreme = 3m). Population displacement indicated bottom right.

Methodology

Global mean sea level is projected to rise by 2m at the end of this century. However, in order to determine local sea level rise (SLR), one has to take into account local coastal flood levels which could be 2.8m above Mean Higher-High Water (MHHW) at extreme forecasts. These local levels bring variability to the projected SLR from 1m to 6.5m (eg. Rio vs Kolkata).

The SLR scenarios used in this study are based on the forecasts from Climate Central – Coastal Risk Screening Tool  with the following parameters:

• Sea level Projection Source
• Coastal Flood Level
• Pollution Scenario
• Luck

Sea level Projection Source:

From two highly cited journals by Kopp et al., estimating SLR mainly due to ocean thermal expansion and ice melt. The mid-range scenario projected 0.5-1.2m of SLR based on different representative concentration pathways (RCP) defined by the IPCC. While the pessimistic scenario added more mechanisms of ice-sheet melting, estimating SLR at 1m-2.5m in 2100, with a projection of 10m SLR at 2300.

Coastal Flooding

More frequent coastal flooding is a direct impact of sea-level rise. Based on the Global tides and surge reanalysis by Muis et al., (2016), it is estimated that the extreme coastal water level could be from 0.2 – 2.8m over the mean level. While in extreme cases like China and the Netherlands it could experience 5-10m of extreme sea levels. Here, the coastal local flood level is added on top of the projected SLR.

Pollution Scenario:

Allows choosing the RCP, the greenhouse gas concentration trajectory defined by the IPCC.  The mild level is based on RCP4.5, of 2°C temperature rise; while the Extreme level is based on RCP 8.5, of 4°C temperature rise.

Luck:

Applies to the baseline SLR, defined in the “Sea level projection” section, upon which we add flooding. “Mild” refers to the mid-range scenario of 0.5-1.2m, and “extreme” to the pessimistic scenario of 1-2.5m. We used the high-end value of each scenario (mild = 1m; extreme = 2.5m).

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References:

• Kulp, Scott A., and Benjamin H. Strauss. “New elevation data triple estimates of global vulnerability to sea-level rise and coastal flooding.” Nature communications 10.1 (2019): 1-12.

• Florczyk, A. J., Corbane, C., Ehrlich, D., Freire, S., Kemper, T., Maffenini, L., Melchiorri, M., Politis, P., Schiavina, M., Sabo, F. & Zanchetta, L. (2019). GHSL Data Package 2019 Public Release.

• Kopp, R. E., DeConto, R. M., Bader, D. A., Hay, C. C., Horton, R. M., Kulp, S., Oppenheimer, M., Pollard, D. & Strauss, B. H. (2017). Evolving Understanding of Antarctic Ice-Sheet Physics and Ambiguity in Probabilistic Sea-Level Projections. Earth’s Future, 5(12), 1217–1233.

• Kopp, R. E., Horton, R. M., Little, C. M., Mitrovica, J. X., Oppenheimer, M., Rasmussen, D. J., Strauss, B. H. & Tebaldi, C. (2014). Probabilistic 21st and 22nd Century Sea-Level Projections at a Global Network of Tide-Gauge Sites. Earth’s Future, 2(8), 383–406.

• Kulp, S. A. & Strauss, B. H. (2019). New Elevation Data Triple Estimates of Global Vulnerability to Sea-Level Rise and Coastal Flooding. Nature Communications, 10(1), 4844. Retrieved June 21, 2020, from http://www.nature.com/articles/s41467-019-12808-z

• Muis, S., Verlaan, M., Winsemius, H. C., Aerts, J. C. J. H. & Ward, P. J. (2016). A Global Reanalysis of Storm Surges and Extreme Sea Levels. Nature Communications, 7.