Sea-level rise drives shoreline retreat in Hawaii

Aug 30, 2013
This is an example of chronic coastal erosion threatening a building on the island of Maui. Higher average rates of erosion on Maui are due in part to higher rates of localized sea level rise compared to nearby Oahu Island. Credit: Zoe Norcross-Nuu

Sea-level rise (SLR) has been isolated as a principal cause of coastal erosion in Hawaii. Differing rates of relative sea-level rise on the islands of Oahu and Maui, Hawaii remain as the best explanation for the difference in island-wide shoreline trends (that is, beach erosion or accretion) after examining other influences on shoreline change including waves, sediment supply and littoral processes, and anthropogenic changes. Researchers from the University of Hawaii – Manoa (UHM), School of Ocean and Earth Science and Technology (SOEST) and the State of Hawaii, Department of Land and Natural Resources published a paper recently showing that SLR is a primary factor driving historical shoreline changes in Hawaii and that historical rates of shoreline change are about two orders of magnitude greater than SLR.

The authors of the work point out that knowing that SLR is a primary cause of on a regional scale allows managers and other coastal zone decision-makers to target SLR impacts in their research programs and long-term planning. This study is confirmation that future SLR is a major concern for decision-makers charged with managing beaches.

"It is common knowledge among coastal scientists that leads to shoreline recession," stated Dr. Brad Romine, coastal geologist with the University of Hawaii Sea Grant College Program. "Shorelines find an that is a balance between sediment availability and rising . On an individual beach with adequate sediment availability, beach processes may not reflect the impact of SLR. With this research we confirm the importance of SLR as a primary driver of shoreline change on a regional to island-wide basis."

Globally-averaged sea-level rose at about 2 mm per year over the past century. Previous studies indicate that the rate of rise is now approximately 3 mm per year and may accelerate over coming decades. The results of the recent publication show that SLR is an important factor in historical shoreline change in Hawaii and will be increasingly important with projected SLR acceleration in this century. "Improved understanding of the influence of SLR on historical shoreline trends will aid in forecasting beach changes with increasing SLR," said Dr. Charles Fletcher, Associate Dean and Professor of Geology and Geophysics at the UHM SOEST.

"The research being conducted by SOEST provides us with an opportunity to anticipate SLR effects on coastal areas, including Hawaii's world famous beaches, coastal communities, and infrastructure. We hope this information will inform long range planning decisions and allow for the development of SLR adaptation plans," said Sam Lemmo, Administrator, Department of Land and natural Resources, Office of Conservation and Coastal Lands.

Results of island-wide historical trends indicate that Maui beaches are significantly more erosional than beaches on Oahu. On Maui, 78% of beaches eroded over the past century with an overall (island-wide) average shoreline change rate of 13 cm of erosion per year, while 52% of Oahu beaches eroded with an overall average shoreline change rate of 3 cm of erosion per year.

The variation in long-term relative SLR rates along the Hawaii archipelago is due, in large part, to variations in island subsidence with distance from actively growing Hawaii Island and/or variations in upper ocean water masses. The islands of Oahu and Maui, Hawaii, with significantly different rates of localized sea-level rise (SLR has been approximately 65% higher rate on Maui) over the past century, provided a natural laboratory to investigate possible relations between historical shoreline changes and SLR.

Island-wide and regional historical shoreline trends were calculated for the islands using shoreline positions measured from aerial photographs and survey charts. Shoreline positions were manually digitized using photogrammetric and geographic information system (GIS) software from aerial photo mosaics and topographic and hydrographic survey charts provided by the National Ocean Service (NOS). Shoreline movement through time was measured using GIS software. Historical shoreline data were optimized to reduce anthropogenic influences (e.g., constructing seawalls or sand mining) on shoreline change measurements. The researchers controlled for influences other than SLR to determine if SLR remains as the best explanation for observed changes. They also utilized a series of consistency checks to determine if results are significant and to eliminate other possible explanations.

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More information: B M Romine, C H Fletcher, M M Barbee, T R Anderson, L N Frazer (2013) Are beach erosion rates and sea-level rise related in Hawaii? Global and Planetary Change, DOI: 10.1016/j.gloplacha.2013.06.009

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NikFromNYC
2.4 / 5 (23) Aug 30, 2013
"Globally-averaged sea-level rose at about 2 mm per year over the past century. Previous studies indicate that the rate of rise is now approximately 3 mm per year and may accelerate over coming decades."

All long running Hawaiian tide gauges defy this claim:
http://s10.postim...uges.jpg

Like nearly *all* world tide gauges, they show *no* big 'G' Global Warming signal, just the usual small 'g' one still locked onto the exact same natural warming trend that has existed since the end of the Little Ice Age of the 1600s.

The world average of tide gauges is shown in this info-graphic, which reveals how the systematic *mismatch* between continuing tide gauge records (relative to shore) that are truncated (!) and satellite altimetry data (absolute level) has been scandalously used by NASA's press office to insinuate that this instrumental mismatch represents a sudden jump in the rate of sea level rise:
http://s22.postim..._Two.jpg
NikFromNYC
2.3 / 5 (21) Aug 30, 2013
The large version of their Figure 3 of the tide gauge of Honolulu is seen here:
http://tidesandcu...lu,%20HI

This tide gauge and the vast majority of other continuously long running records utterly falsify claims from trumped up press releases that are repeated endlessly by the green energy con$ulting firm web site Phy$.org and then headline-writing ma$$ media reporters that sea level data supports claims of Man Made Global Warming Via Massive Water Vapor Amplification Of The Old School Greenhouse Effect (MMGWVMWVAOTOSGE).

Honolulu has lots of boring friends:
http://s23.postim...andy.gif

Real data disproves MMGWVMWVAOTOSGE.

"If the old trend wont quit you must acquit!" - defense lawyer for CO₂

-=NikFromNYC=-, Ph.D. in carbon chemistry (Columbia/Harvard)

Read more at: http://phys.org/n...html#jCp
Gmr
2.6 / 5 (9) Aug 31, 2013
[Again, we see the bull staking their claim early. This territory may go unchallenged, or it may support the ecosystem of scavengers who pick at scraps of controversy. We will have to be patient and see.][i]What will happen[/i][b]bold[/b][s]strikethrough?[/s]
NikFromNYC
2 / 5 (16) Aug 31, 2013
Gmr labelled me a egotistical narcissist after I included autobiographical tidbits to counter repeated assumptions that I was a cartoon worthy knuckle dragging Rush Limbot in the pay of Big Oil instead of a self-employed nerd living two blocks from the Tom's Diner building where James "Coal Death Trains" Hansen used to work. When that little NASA computer terminal office tried to drag the name of Columbia University science departments proper into the junk science gutter and label my buddies "deniers" worthy of prosecution for "crimes against humanity," I became territorial indeed since my reputation was personally at stake and so I made some infographics for the likes of my Upper West Side neighbors. Hard scientists don't even consider Climate Studies to be worthy of debunking since they see it as just another bunch of amateurs like sociologists or theoretical anthropologists, and in other words a branch of political science, merely, a bunch of policy wonk speculation by hacks.
NikFromNYC
1.8 / 5 (15) Aug 31, 2013
¿ʇou ʇı sǝop 'ʎɹoǝɥʇ buıɯɹɐʍ ןɐqoןb pǝıɟıןdɯɐ sǝıɟısןɐɟ ʎןɹǝʇʇn ǝbnɐb ǝpıʇ nןnןouoɥ puǝɹʇ pǝxıɟ ǝɥʇ˙˙˙˙ɹɯb ɐʇɐp ǝɥʇ ʇɐ *ʞooן*

It's kind of interesting the way a whole creepy little industry of satellite blogs has gathered around the main skeptical clearinghouse blog, all based on the massive scandal that Tony Watts pokes fun at slanderous trolls before finallly banning them:
http://wattsupwit...g-spawn/

Such parasitic sites allows Climatology members to safely wallow in obscure group bonding fests every time their eco-terrorist level fanaticism is ridiculed. They really are personally obsessed with skeptics, as were the academics in the "Hide The Decline" e-mails of Climategate infamy:

"Don't leave stuff lying around on ftp sites - you never know who is trawling them. The two MMs have been after the CRU station data for years. If they ever hear there is a Freedom of Information Act now in the UK, I think I'll delete the file...." -Phil Jones e-mail to M. Mann
Mauibrad
2.1 / 5 (11) Aug 31, 2013
There is no long-term sea level rise in Hawaii. The sea level the same it has always been in Hawaii.
Gmr
3 / 5 (4) Aug 31, 2013
[[There appears to be some posturing towards the blind, again... I'll have to question other researchers on what a 'qauqe' is... but it appears to affect 'qlobal' warming...and get a better blind...]]
Mauibrad
2.3 / 5 (12) Aug 31, 2013
BTW, the erosion in your picture above in North Kihei, Hawaii, is because that is where a freshwater stream that sometimes floods exits into the ocean, not sea level rise. There hasn't been any sea level rise on shorelines in Hawaii in at least the past 20 years, which I can vouch for.
Gmr
2.6 / 5 (5) Aug 31, 2013
[[The bull continues unchallenged in this territory. It appears to be because there is slim pickings to be had on this carcass - only one lone scavenger has appeared to pull at the bones. There will be no harem today.]]
Kiwini
1.3 / 5 (14) Sep 01, 2013
BTW, the erosion in your picture above in North Kihei, Hawaii, is because that is where a freshwater stream that sometimes floods exits into the ocean, not sea level rise. There hasn't been any sea level rise on shorelines in Hawaii in at least the past 20 years, which I can vouch for.


Make that at least 50 years... the beaches I played on back in the 60's and 70's are still there, the same height above the Pacific now as they were then.

On the short term/human scale, the only time the ocean intrudes is when some dumb haole builds too close to the wrong place.

Long-term, all of Hawaii-nei will eventually be consumed by the ocean, although the disappearance will be due to tectonics and erosion compounded by time, not a rising sea level.

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