TY - JOUR
T1 - Rethinking Reef Island Stability in Relation to Anthropogenic Sea Level Rise
AU - Kane, Haunani H.
AU - Fletcher, Charles H.
N1 - Funding Information:
Funding for this study was provided by the University of Hawai‘i School of Ocean and Earth Science and Technology, the University of Hawai‘i Graduate Student Organization, the U.S. Geological Survey, and the Advancing Science in America Foundation. Kristian McDonald, Shellie Habel, Kammie Dominique Tavares, Mark Stege, Fern Lehman, and Karl Fellenius provided invaluable assistance collecting data in the field. We thank the people of the Republic of the Marshall Islands for allowing us to learn from your home. For islanders across the globe, your strength and resilience does not go unnoticed. This work was accomplished with you in mind. This material is based upon work supported by the National Science Foundation under grant number 1907359.
Publisher Copyright:
© 2020 The Authors.
PY - 2020/10/1
Y1 - 2020/10/1
N2 - Unprecedented rates of anthropogenic sea level rise (ASLR) and attendant wave-driven flooding and salinization threaten the stability (and habitability) of atoll islands. Thus, there is doubt regarding the continued existence of sovereign atoll nations and unique, place-based indigenous atoll cultures. Evidence that some atoll islands may have originally formed in the latter stages of post-glacial sea level rise (SLR) has been interpreted to mean they will persist under accelerating ASLR. These forecasts are at odds with interpretations that atoll islands will succumb to rising seas. To shed light on conflicting models of island stability, we develop a multitemporal island vulnerability assessment (MIVA) to anticipate island instability and apply it in the Republic of the Marshall Islands (RMI) where there is a history of previous research. Using evidence from geological and historical records of island response to changing late Holocene sea level and modern tide, wave, and groundwater observations, we identify thresholds where islands pass from stable to unstable phases due to projected local, relative ASLR. Under the most likely scenario (intermediate-high) where ASLR reaches 1.91 m by 2100, island stability deteriorates by midcentury as historical rates of SLR at RMI increase threefold, and temporary flood events deteriorate potable groundwater and agroforests. In the second half of the century, as ASLR exceeds geological sea level thresholds, permanent island instability will be inevitable with no action. We conclude that these islands are already trending into declining stability due to ASLR as documented by published observations of extreme tides, wave inundation, salinization, and sediment mobilization.
AB - Unprecedented rates of anthropogenic sea level rise (ASLR) and attendant wave-driven flooding and salinization threaten the stability (and habitability) of atoll islands. Thus, there is doubt regarding the continued existence of sovereign atoll nations and unique, place-based indigenous atoll cultures. Evidence that some atoll islands may have originally formed in the latter stages of post-glacial sea level rise (SLR) has been interpreted to mean they will persist under accelerating ASLR. These forecasts are at odds with interpretations that atoll islands will succumb to rising seas. To shed light on conflicting models of island stability, we develop a multitemporal island vulnerability assessment (MIVA) to anticipate island instability and apply it in the Republic of the Marshall Islands (RMI) where there is a history of previous research. Using evidence from geological and historical records of island response to changing late Holocene sea level and modern tide, wave, and groundwater observations, we identify thresholds where islands pass from stable to unstable phases due to projected local, relative ASLR. Under the most likely scenario (intermediate-high) where ASLR reaches 1.91 m by 2100, island stability deteriorates by midcentury as historical rates of SLR at RMI increase threefold, and temporary flood events deteriorate potable groundwater and agroforests. In the second half of the century, as ASLR exceeds geological sea level thresholds, permanent island instability will be inevitable with no action. We conclude that these islands are already trending into declining stability due to ASLR as documented by published observations of extreme tides, wave inundation, salinization, and sediment mobilization.
KW - Holocene
KW - Republic of the Marshall Islands
KW - atoll
KW - coastal vulnerability
KW - reef island
KW - sea level rise
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U2 - 10.1029/2020EF001525
DO - 10.1029/2020EF001525
M3 - Article
AN - SCOPUS:85093871506
SN - 2328-4277
VL - 8
JO - Earth's Future
JF - Earth's Future
IS - 10
M1 - e2020EF001525
ER -