Sea Level Rise/Coastal Inundation

“Sea level rise and coastal inundation – we need the data!”
Workshop theme

To identify inundation risk you need to know current elevations of land and sea and how both are expected to change.  Unlike coastal areas in the lower 48, where this information is available in great detail, information for Alaska’s 50,000 kilometers of coastline is sparse, low resolution and/or out of date. Much better information is sorely needed if communities and land and resource managers can anticipate and plan for changes.

Impacts in Alaska

While details of the magnitudes and impacts of sea level rise are missing, as Bob Dylan famously said – “you don’t need a weatherman to know which way the wind blows”.  It is clear that global sea levels are rising.  With large stretches of low lying coastline, Alaska is destined to experience profound impacts from rising ocean waters.

Four Factors - A Start at Mapping Local Coastline Changes

The four topics below explain data needed to predict future inundation. The information here is preliminary, but does provide a starting picture of the coastal areas likely most at-risk.

  1. Changes in Sea Level Elevations:
    The world’s oceans do not behave like a bathtub – “sea level” varies from place to place. Projecting sea level rise must account for both global and local changes.  Estimates for average sea level rise world-wide range from ½ to 2 meters by century’s end.  Data needed: Comprehensive data on current mean local sea level plus detailed modeling of expected local sea level rise.

  2. Starting Land Elevations: Low Lying Areas
    Land elevations relative to sea level are critical for predicting impacts of sea level rise. The map at right uses topographic data of limited accuracy to show lowest lying coastal areas.  Data needed: Current, comprehensive, high resolution topographic data including digital elevation models.

  3. Changing Land Elevations: Uplift & Subsidence
    Where land is subsiding the impact of sea level rise is intensified; where land is rising the impact is muted.  In simplest terms, rocky areas, with a recent history of glacial coverage are rising, while lower lying areas like the Y-K delta are subsiding. Data needed:  Accurate measurements and projections of land areas subsiding and areas rising due to tectonic lift and/or post-glacier-melt rebound.

  4. Thawing Permafrost
    Thawing permafrost can lead to subsiding land; areas with higher percentages of water ice are prone to more subsidence.  The red areas on the coarse, statewide map at left are areas with 40% to as much as 80% water ice. Large portions of these areas are also low elevation areas.  Data needed: Better data on permafrost locations and water content (ground ice), and on the dynamics of permafrost thaw.

And a final word...

Predicting climate change is enormously difficult.  It is worth noting, however, that over the last 30 years, the actual increases in sea level rise, and decreases in sea ice, have generally exceeded those predicted by the Intergovernmental Panel on Climate Change (the IPCC) and other respected scientific research groups.

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