Sea-level Rise for the Coasts of California, Oregon, and Washington: Past, Present, Future


Level Rise for the Coasts of California, Oregon, and Washington Past, Present, Future National Research Council of the National Academies The National Research Council has just completed a new report on sea level rise along the coast of California, Oregon and Washington which is intended to provide elected officials, coastal managers, and decision makers with an objective and independent analysis upon which they can base future coastal planning. Sea levels are rising because the ocean is warming which increases ocean volume, and also because ice sheets and glaciers are melting Over the past century tide gages indicate that sea level has risen globally about 7 inches but over the last 20 yrs satellite measurements indicate that number has accelerated to nearly twice as fast as its been over the last hundred years So the question is how much will sea level rise over the next century? Although we have global sea level rise values, we know from place to place that those values will vary depending on offshore oceanographic conditions and whether the land is rising or sinking or is tectonically active, and along the west coast we know we have an active coastline such that the land has been rising and sinking which affects those local sea level rise values.

From San Diego north to Cape Mendocino, we know the coast of California which is the Pacific plate is sliding alongside the San Andreas fault with very little vertical motion along the coast line such that sea level from tide gages over the last century is close to the global number about 4-8 North of Cape Mendocino, along the coast of Northern California, Oregon, and Washington, however, the land has been slowly rising such that many of the tide gages actually show a small drop in sea level over the last century or so This region lies along the Cascadia Subduction Zone, where the Juan de Fuca Plate, descends or is subducted, beneath the North American Plate. This builds up seismic strain along the coast, which actually pushes the land upward, and explains why sea level in the region has dropped, even as global sea level has risen. This could all change very rapidly however if we have a large offshore earthquake which could cause rapid subsidence and therefore an instant rise in sea level.

Observations and projections of both climate change and sea level rise indicate that sea level rise is going to continue to rise well into the future. There are uncertainties however and that makes precise predictions difficult. The further we go out in time, the greater those uncertainties become The Committee projected future regional sea levels, and they vary along the west coast. By 2030 our average sea-level rise values for the area south of Cape Mendocino are projected to be about 6 inches, while to the north, only about 2 inches of rise is expected because the coastline is slowly rising. By 2050, we project 12 inches orf rise to the south and 6 inches to the north along the Oregon and Washington coasts; and by 2100, average values of 36 inches along the California coast are projected, and 24 inches north of Cape Mendocino.

These are average values however and the actual values could be significantly higher or lower. For some perspective, the two major international airports in San Francisco Bay, San Francisco and Oakland, were built on fill only a few feet above sea level such that 16 inches of sea level rise, which could happen within the next several decades, would begin to inundate those runways. Many west coast communities already experience coastal erosion, flooding and inundation, and loss of wetlands due to El Ni o elevated sea levels, the impacts of large storm waves at times of high tide, and a slowly rising sea level. The water levels reached during these short-term events have exceeded mean sea levels projected for 2100. Thus, at least for the next several decades, these events are a greater hazard for the west coast than the climate-driven rise in sea level. It is very likely that in the future as sea level continues to rise, that the impacts of those events will get greater in magnitude and also likely they will increase in frequency, as we move into the future.

Coastal communities need to begin to understand these processes and what these sea level rise indicate to them and plan accordingly. gd E gd E gd E gd E gd E :p E [Content_Types].xml #!MB ;c=1 _rels/.rels theme/theme/themeManager.xml sQ}# theme/theme/theme1.xml G$$DA : BR {i5@R V*[_X ,l\Y Ssd+r] 5\|E Vky- V4Ej 6NGU s?^V *<“)QH @\&> 7;wP EBU` 5<V8 LStf+] C9P^ wB>VD GGHPXNT, /M,W m2iU [[v _Xtl theme/theme/_rels/themeManager.xml.rels 6?$Q K(M&$R(.1 [Content_Types].xmlPK _rels/.relsPK theme/theme/themeManager.xmlPK theme/theme/theme1.xmlPK theme/theme/_rels/themeManager.xml.relsPK <?xml version=”1.0″ encoding=”UTF-8″ standalone=”yes”?> <a:clrMap xmlns:a=”” bg1=”lt1″ tx1=”dk1″ bg2=”lt2″ tx2=”dk2″ accent1=”accent1″ accent2=”accent2″ accent3=”accent3″ accent4=”accent4″ accent5=”accent5″ accent6=”accent6″ hlink=”hlink” folHlink=”folHlink”/> Video Transcript Stacy Stacy Jannis Normal.dotm Rebecca Microsoft Macintosh Word PICT! o{o{^ g9o{o{c F1Nsw F1kZNsc F1NsR NsNss g9o{R o{o{c g9o{g9c g9g9o{ g9o{^ kZkZw o{o{c o{o{kZw o{JR o{g9Z kZo{R kZg9R Nso{Z g9g9NsV g9g9c g9g9Z g9g9Z o{o{c g9g9Z kZo{^ g9g9c g9g9{ o{kZo{g9o{kZo{kZo{ kZ${ o{kZkZo{kZs kZkZg9kZo{w o{kZw g9o{kZkZo{w o{kZg9o{kZc g9g9kZs kZo{c o{kZs o{g9o{g9s g9g9s g9o{o{kZo{kZw kZg9g9kZs o{g9o{kZs kZg9o{o{kZg9c kZo{g9kZkZw g9g9w o{g9g9c g9g9kZ^ “g9c g9kZkZc kZo{c o{kZ^ o{g9c g9o{Z kZo{g9kZc kZkZs kZg9g9c g9o{g9kZg9^ o{kZ{ o{o{kZw kZg9s kZkZw kZo{c kZo{w kZo{kZw g9g9o{o{kZ{ g9kZkZo{o{kZg9g9c o{o{kZs g9o{w kZo{kZkZZ Bg9Z g9Nsc kZo{c o{kZo{kZZ kZo{Z g9g9c kZo{Z g9kZo{c kZkZc o{o{ o{o{s o{o{w o{o{s o{o{ o{kZs !o{kZg9g9kZs g9o{o{g9kZo{g9w kZkZo{o{s kZkZw g9o{w o{kZo{g9g9{ o{g9Z kZg9V g9g9Z !g9g9c g9g9s g9o{kZc g9kZg9c g9g9o{Z o{kZg9c g9kZw o{g9s o{-c o{o{s kZo{w o{o{{ kZo{s o{o{c kZo{s g9kZo{ o{o{s o{g9kZkZ kZo{g9g9s g9o{ g9(V kZkZc g9kZs g9g9kZo{s g9g9kZs g9g9o{g9g9s kZo{kZc kZkZg9c o{o{{ g9g9 ‘kZZ g9g9Z o{g9Z kZkZg9w g9o{g9Z o{kZkZo{kZkZZ o{kZkZo{kZc g9kZ^ kZkZg9o{{ g9o{g9o{kZg9s kZo{g9kZs kZo{^ o{o{w kZg9 kZo{kZo{s o{o{{ o{o{s o{o{{ o{o{s o{kZ{ o{kZs kZg9w g9o{{ o{kZo{w kZo{c g9kZo{{ o{o{ o{g9kZg9g9{ kZkZs ,g9V o{kZc kZo{g9g9s o{kZc g9g9c Nso{Z g9o{{ 4g9g9kZ^ o{kZg9kZs g9g9o{^ g9g9c g9kZw kZkZw o{o{g9s kZg9c kZg9Z kZg9g9kZs kZkZc g9kZkZ o{kZw o{o{kZw o{g9s o{o{^ o{kZs g9o{s o{g9w kZo{s kZo{s o{g9w g9kZs kZg9kZw kZo{kZc k|g:^ /g9c g9g9^ g9kZc o{o{{ kZg9kZo{kZkZZ o{8kZ^ kZo{g9^ g9g9Z o{g9o{g9o{c g9o{^ g9kZo{o{c g9g9s kZg9s kZkZw kZo{o{kZkZw o{kZo{o{w o{kZo{o{{ g9o{s kZo{o{s o{g9w o{kZs g90Z o{g9^ kZg9^ kZg9c o{o{^ kZkZc g9g9c kZkZ^ o{kZs Nso{c kZg9V g9NskZc kZg9Z .

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