Prepared in cooperation with and funded in part by the Arctic Landscape Conservation Cooperation (ALCC) Changing Storm Conditions in Response to Projected 21st Century Climate Change and the Potential Impact on an Arctic Barrier Island–Lagoon System—A Pilot Study for Arey Island and Lagoon, Eastern Arctic Alaska Open-File Report 2020–1142 U.S. Department of the Interior U.S. Geological Survey Cover: View from the western end of Barter Island looking southeast toward Arey Lagoon. Image and other oblique images of the North Slope of Alaska are available for download at http://pubs.usgs. gov/ds/436/ (Gibbs and Richmond, 2009). Changing Storm Conditions in Response to Projected 21st Century Climate Change and the Potential Impact on an Arctic Barrier Island–Lagoon System—A Pilot Study for Arey Island and Lagoon, Eastern Arctic Alaska By Li H. Erikson, Ann E. Gibbs, Bruce M. Richmond, Curt D. Storlazzi, Ben M. Jones, and Karin A. Ohman Prepared in cooperation with and funded in part by the Arctic Landscape Conservation Cooperation (ALCC) Open-File Report 2020–1142 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior DAVID BERNHARDT, Secretary U.S. Geological Survey James F. Reilly II, Director U.S. Geological Survey, Reston, Virginia: 2020 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit https://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit https://store.usgs.gov. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation: Erikson, L.H., Gibbs, A.E., Richmond, B.M., Storlazzi, C.D., Jones, B.M., and Ohman, K.A., 2020, Changing storm condi- tions in response to projected 21st century climate change and the potential impact on an arctic barrier island–lagoon system—A pilot study for Arey Island and Lagoon, eastern Arctic Alaska: U.S. Geological Survey Open-File Report 2020–1142, 68, p., https://doi.org/10.3133/ofr20201142. Associated data for this publication: Erikson, L.H., Gibbs, A.E., Richmond, B.M., Jones, B.M., Storlazzi, C.D., and Ohman, K.A., 2020, Modeled 21st century storm surge, waves, and coastal flood hazards, and supporting oceanographic and geological field data (2010 and 2011) for Arey and Barter Islands, Alaska and vicinity: U.S. Geological Survey data release, https://doi.org/10.5066/ P9LGYO2Q. ISSN 2331-1258 (online) iii Acknowledgments Funding for this study was provided by the Arctic Landscape Conservation Cooperative (ALCC), and we wish to thank ALCC’s Philip Martin and Jennifer Jenkin for collaborative support and discussions that sharpened our thinking and improved our overall study. We thank the U.S. Geological Survey Coastal and Marine Hazards and Resources Program. We also acknowledge the World Climate Research Programme’s Working Group on Coupled Modeling, which is responsible for CMIP5, and we thank the climate modeling groups (listed in table 4 of this report) for producing and making available their model output. The U.S. Department of Energy’s Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals for CMIP. iv Contents Acknowledgments ........................................................................................................................................iii Executive Summary .......................................................................................................................................1 Introduction.....................................................................................................................................................2 Clarification of Key Terms .............................................................................................................................5 Wind-Generated Waves ......................................................................................................................5 Storm Surge ...........................................................................................................................................6 Total Water Levels ................................................................................................................................7 Barrier Island Overwash and Breaching ..........................................................................................7 Study Area.......................................................................................................................................................8 Regional Setting ....................................................................................................................................8 Local Setting ..........................................................................................................................................9 Data and Methods .......................................................................................................................................10 Historical Shoreline Positions ..........................................................................................................10 Model Simulation Methodology .......................................................................................................10 Meteorological Forcing and Sea-ice Data .....................................................................................12 Wind Adjustments .....................................................................................................................13 Sea-level Rise ......................................................................................................................................13 Field Observations and Model Evaluation ...............................................................................................14 Results ...........................................................................................................................................................15 Historical Shoreline Change .............................................................................................................15 Arey Island Breaching History ................................................................................................15 Arey Island Shoreline Change Rates ......................................................................................17 Arey Lagoon Shoreline Change Rates ...................................................................................17 Hindcast and Projected Storms ......................................................................................................19 Waves .........................................................................................................................................20 Deepwater Wave Conditions ..........................................................................................20 Nearshore Waves at the 10-m Isobath .........................................................................24 Storm Surge Levels ...................................................................................................................24 Impact of Waves and Storm Surge on Arey Island Stability .......................................................26 Hindcast Period ..........................................................................................................................26 Projected Period ........................................................................................................................28 Inundation and Flood Potential of Arey Lagoon Mainland Coast ...............................................29 Projected Permanent Inundation ............................................................................................29 Intermittent Flood Potential ......................................................................................................29 Summary of Findings and Conclusions ...................................................................................................34 Historical Shoreline Change Rates of Arey Island and Arey Lagoon Mainland Shore ...........34 Projected Ocean Storm Conditions and Changes with Respect to the Recent Past ..............34 Future Stability of the Barrier Island Chain and its Capacity in Modulating Wave Energy Reaching Coastal Wet Sedge Areas within Arey Lagoon ..............................................34 Effects of Sea-level rise and Changing Storm Conditions on the Frequency and Extent of Flooding ...................................................................................................................................35 References Cited..........................................................................................................................................36 v Appendix 1. Documented historical and model hind-cast storm events in the vicinity of Arey Island and Lagoon ..........................................................................................................................41 References Cited.................................................................................................................................44