Sea Level Rise

Climate change has the potential to profoundly impact our well being and way of life.  In particular, rising sea levels will increase the occurrence and severity of coastal erosion and flooding, threatening natural resources and economic sectors concentrated along low-lying shores.

As shown in Figure 1, the observed rate of global sea level rise (SLR) has been accelerating: 0.6 mm/year (1900 – 1930), 1.2 mm/year (1930 – 1992), 3.2 mm/year (1993 – 2005) and 4.4 mm/year (2010 – 2015).

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Figure 1. The observed rate of global mean sea level rise is accelerating (1)

 

The worst case scenario or “business as usual” projection of SLR reported by the Intergovernmental Panel on Climate Change (IPCC) 2013 ranges from 1.6 feet (0.5 m) to 3.3 feet (0.98 m) by 2100, as shown below in Figure 2 (2). Recent evidence suggests that ice sheets and glaciers are melting at rates greater than predicted, making this scenario the more likely scenario (3).

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Figure 2. Projected rate of global mean sea level rise under different greenhouse gas emissions scenarios (2). The projected rate of global sea level rise, based on the IPCC RCP 8.5 scenario, ranges from 1.6 feet (0.5 m) to 3.2 feet (0.98 m) by 2100 (4). Recent evidence suggests that this high end scenario is the likely scenario because ice sheets and glaciers are melting at rates greater than accounted for in the IPCC report (3)

Sea level has risen around Hawaiʻi approximately 0.06 inches per year (1.5 mm per year or 6 inches over the next 100 years. Local relative sea level around Hawaiʻi, as shown below in Figure 3, is not only dependent on the global average trend but also local oceanographic patterns, meteorology, geomorphology and tectonics related to the Hawaiian hotspot.

 

 

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Figure 6. Observed mean-sea-level trends in the Hawaiian Islands (5)


Hawaiʻi-specific projections are in line with global projections of SLR with a mean height of 3 feet by 2100 (6).  The consequences of SLR for Hawaiʻi are severe compared to many other coastal states, as the majority of our population, public infrastructure, and economic sectors exist on low-lying coastal plains which are highly susceptible to coastal hazards. Hawai‘i and other Pacific islands are expected to experience significantly greater than average SLR (6). In addition, chronic erosion in Hawaiʻi causes beach loss, damages homes and infrastructure, and endangers critical habitat. These problems will likely worsen with increased SLR.


Projected Heights of Sea Level Rise for Honolulu

 

2030

Range: 0.3 to 0.7 feet
Mean: 0.5 feet

2050

Range: 0.6 to 1.4 feet
Mean: 1.0 feet

2100

Range: 1.6 to 4.6 feet
Mean: 3.0  feet


References

  1. Hay, C.C., et al., Probabilistic reanalysis of twentieth-century sea-level rise. Nature, 2015. 517(7535): p. 481-484.
  2. IPCC, Summary for Policymakers, T.F. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, Editor. 2013: Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
  3. NASA. Warming seas and melting ice sheets. ScienceDaily. August 26, 2015  October 5, 2015]
  4. Scripps Institution of Oceanography. The Keeling Curve. 2015; Available from: https://scripps.ucsd.edu/programs/keelingcurve/.
  5. Sea Level Trends. National Oceanic and Atmospheric Administration.  November 2015]
  6. Kopp, R.E., et al., Probabilistic 21st and 22nd century sea‐level projections at a global network of tide‐gauge sites. Earth’s Future, 2014. 2(8): p. 383-406.