Archives par mot-clé : Sea level

La hausse du niveau de la mer accélère-t-elle l’érosion des côtes? (1/3)

by Y. Battiau-Queney, 15 août 2019 in ScienceClimatEnergie


Il est courant de lire et d’entendre que la hausse du niveau de la mer, l’une des conséquences les plus manifestes du réchauffement climatique, va accélérer l’érosion de nos côtes, menacer de submersion marine de vastes zones littorales urbanisées et faire disparaître nombre d’îles basses habitées. Ces craintes sont-elles justifiées? Comme un consensus ne vaut pas vérité scientifique, on va essayer de démêler le vrai du faux en partant de l’état des connaissances scientifiques sur la hausse du niveau de la mer et analyser ses effets possibles sur les processus d’érosion des côtes.

 

1/ Que sait-on de la hausse du niveau de la mer ?

1.1. État des connaissances sur les variations passées et présentes du niveau de la mer à l’échelle mondiale

Une bonne synthèse récente sur les causes et l’ampleur de la hausse du niveau de la mer se trouve dans Cazenave et Le Cozannet (2014). On y trouvera une très abondante bibliographie antérieure à 2013. Les méthodes utilisées par les scientifiques pour évaluer la tendance moyenne de l’élévation du niveau de la mer dépendent de la période considérée. A l’échelle du Pléistocène (1 800 000 ans) et de l’Holocène (10 000 ans) on dispose d’archives sédimentologiques (repérage d’anciennes plages “soulevées”, analyse de niveaux tourbeux recouverts de sédiments marins, stratigraphie et datation de récifs coralliens …) et de données archéologiques, particulièrement riches sur les côtes méditerranéennes. On sait qu’à plusieurs reprises, pendant les phases interglaciaires du Pléistocène, le niveau de la mer a été supérieur à l’actuel de 5 à 10 m au moins (Planton et al., 2015). À partir du milieu du 19ème siècle, on utilise les données souvent précises des marégraphes installés principalement dans les ports de l’hémisphère nord. Elles fournissent les altitudes relatives du niveau de la mer par rapport aux terres émergées. Depuis 1993, les données satellitaires fournissent des altitudes absolues du niveau de la mer par rapport à l’ellipsoïde terrestre de référence et permettent d’avoir une vision beaucoup plus globale des variations du niveau des océans à toutes les latitudes et longitudes.

Tableau 1 : variations du niveau de la mer indiquées par les marégraphes (sources: SONEL et GLOSS; Wöppelmann et al., 2014 pour Marseille) (ND= non documenté). Les données dans les colonnes sont exprimées en mm/an.

Malfeasant Omissions? German Flagship ARD Broadcasting One-Sided, Drama-Making Sea Level Reporting

by Dr. S. Lüning, August 9, 2019 in NoTricksZone


What follows is another example of the tricks the mainstream media use to produce fake drama and urgency concerning sea level rise and climate change – namely omissions – and how geologist Sebastian Lüning held their feet to the fire.

Dr. Sebastian Lüning wrote a complaint to German ARD public broadcasting concerning its December 2, 2018, one-sided reporting of the Indian island of Ghoramara and the sea level rise it is allegedly experiencing. The €6.9 billion euro publicly funded, 22,612-employee ARD is the German equivalent to the UK’s BBC.

What follows is the exchange between Lüning and the ARD editorial staff:

With Sea-Level Rise, Climate Science Meets Reality

by J. Weatherall, August 6, 2019 in ClimateChangeDispatch


Numerous satellites utilized by Australian agencies and research bodies are able to take a measure of sea level by way of an altimeter. However, according to the CSIRO, it should not be overlooked that the signal to do so requires

# A satellite in an orbit which repeats the same ground track very closely (within about 1 kilometer)

# A radar system to measure the distance from the satellite to the sea surface to high accuracy. TOPEX/Poseidon and Jason-1 use two radar frequencies, Ku band (13.6GHz) and C band (5.3Ghz).

# A tracking system capable of locating the satellite vertically at any time to within a few centimeters. Some of the components of such a system are:

1/ Systems (usually a combination of GPS, satellite laser ranging and the French DORIS system) to locate the satellite

2/ A high-quality gravity model

3/ A model of the drag from solar wind and the atmosphere

4/ Suitable software to combine all of the above

Other corrections to correct the range:

On the satellite:

1/ A water vapor radiometer to measure the amount of water vapor between the satellite and the sea surface (the water vapor slows down the radar pulse, causing the raw measurement to be too long)

2/ Measurement of the range at two frequencies to estimate the “ionospheric correction” — that is, the degree to which the radar pulse is slowed down by free electrons in the ionosphere

3/ The troughs of waves contribute more to the radar reflection than the crests, so we need correction for this. This is estimated from the wind speed and the wave height, both of which can be estimated from the characteristics of the returned radar pulse.

On the ground:

1/ Ocean tide models to convert the raw altimeter measurement to “de-tided”

2/ Estimates (from a model) of the atmospheric pressure. This is used to calculate a correction to the radar range to compensate for the atmosphere slowing down the radar pulse

3/ A correction for the “inverse barometer” effect, where sea level is depressed in areas of high atmospheric pressure, and vice versa.

No one besmirches the accomplishments of the engineering and technology involved.

However, it is a basic truism that the greater the number of separate corrections needing to be applied, the greater the risk of miscalculation.

 

Study: Pacific Islands Will Survive Climate Change

by Eric Worrall, July 17, 2019 in WUWT


Who could have imagined that islands which survived rapid sea level rise at the end of the last ice age have no problem coping with changes in sea level?

Media Release
From: University of Auckland

Pacific atolls can adapt to rising seas and extreme storms – new study

Low-lying Pacific islands in atoll archipelagos such as Tuvalu, Tokelau and Kiribati are likely to adapt to the effects of climate change rather than simply sink beneath the waves, a new study shows.

Tuvalu, Tokelau and Kiribati are widely considered under threat from rising seas and severe storms due to climate change with their residents becoming ‘climate refugees’.

Researchers from the University of Auckland’s School of Environment recreated a scale model of tiny Fatato Island on the southeast rim of Funafuti Atoll in Tuvalu to test the ability of the real island to withstand predicted climate affects.

The study simulated higher sea levels and storm-generated waves up to 4m in a 20m-long water chute or ‘flume’ to replicate real-world sea levels of 0.5m and 1m in a purpose built laboratory at the University of Plymouth in the United Kingdom.

A beach at Funafuti atoll, Tuvalu, on a sunny day. Author Stefan Lins, source Wikimedia

The Holocene Sea Level Highstand

by David Middleton, June 6 , 2019 in WUWT


What is a highstand?

A highstand is one phase of the sea level cycle (AAPG Wiki)

  • Rising
  • Highstand
  • Falling
  • Lowstand

The highstand is the maximum sea level achieved during the cycle.

The Holocene Epoch

The Holocene Epoch was recently formally subdivided into three stages:

  1. Greenlandian Stage = Lower or Early-Holocene. 11.70 ka to 8.33 ka
  2. Northgrippian Stage = Middle or Mid-Holocene. 8.33 ka to 4.25 ka
  3. Meghalayan Stage = Upper or Late-Holocene. 4.25 ka to present

The abbreviation “ka” refers to thousands of years ago. Lower, Middle and Upper are generally used when referring to rock-time units. Early, Mid and Late are generally used when referring to time units (Haile, 1987). Prior to the formal subdivision, Lower/Early, Middle/Mid and Upper/Late were commonly used; however there was no formal nomenclature. The fake word, “Anthropocene” is not used by real geologists.

There is also an informal climatological subdivision of the Holocene:

  • Preboreal 10 ka–9
  • Boreal 9 ka–8 ka
  • Atlantic 8 ka–5 ka
  • Subboreal 5 ka–2.5 ka
  • Subatlantic 2.5 ka–present

Source: Wikipedia

Why would there have been a Mid- to Late-Holocene highstand?

Figure 1. Holocene sea level curves from Moore & Curray, 1974.

Another climate lie bites the dust – No, Honolulu’s beaches aren’t going to disappear in 20 years

by Aylin Woodward, April 25, 201 in WUWT


In May 2017, high tides engulfed parts of the iconic Waikiki beach, edging dangerously close to waterfront hotels. This kind of high-tide flooding, often called a king tide or sunny-day flood, occurs when ocean water surges to higher levels than coastal infrastructure was designed to accommodate. In that case, water levels rose 2.5 feet above average in Waikiki, drowning nearby roads and sidewalks.

According to a 2017 report (which was updated in September 2018), Hawaii’s state capital and Waikiki Beach – along with other coastal strips on Hawaii’s five islands – are expected to experience frequent flooding within 15 to 20 years.

“This flooding will threaten $5 billion of taxable real estate; flood nearly 30 miles of roadway; and impact pedestrians, commercial and recreation activities, tourism, transportation, and infrastructure,” Shellie Habel, lead author of the 2017 study, said in a release.

Now, Hawaii state lawmakers are taking steps to shore up the state’s beaches and coastal cities. A new bill that mandates a statewide shore protection program has passed both houses of Hawaii’s state legislature, and will soon makes its way to the governor’s desk for approval.


All well and good that they want to improve beach resilience. But, the claim that ” Hawaii’s iconic Waikiki Beach could be engulfed by the ocean in 20 years ” is totally bogus.

Here is why:

 

Isle de Jean Charles & Sea Level Rise

by P. Homewood, April 20, 2019 in NotaLotOfPeopleKKnowThat


The Isle de Jean Charles, Louisiana. It’s been largely submerged beneath the sea over the last 6 decades. The program gives the definite impression that the main reason for this inundation is sea level rise due to melting ice and thermal expansion of the oceans – driven by man-made climate change. Attenborough does mention oil extraction as a cause but his narrative is lost to the general tone of the messaging that this is a “climate catastrophe” and that the families driven from their homes in this part of Louisiana are some of the world’s first “climate refugees”. This is palpable bullshit.

 

https://tidesandcurrents.noaa.gov/sltrends/sltrends.html

CA sea level rise alarmist study ignores 30 years of NOAA data with no coastal sea level rise acceleration

by Larry Hamlin, March 13, 2019 in WUWT


NOAA tide gauge data measurements exist for 17 locations along the California coast with 8 of these locations having actual measured sea level rise data covering periods for more than 70 to 120 years in duration.

This measured data shows that none of these California locations are experiencing coastal sea level rise acceleration since climate alarmist first made such erroneous and flawed sea level acceleration claims before the U.S. Senate in 1988.

Climate alarmists and their supporting media conveniently conceal the fact that their flawed claims have been hyped for the last 30 years as they continue to try again and again to make the same repeated but flawed claims apparently hoping that the public will forget their long track record of failure and exaggeration.

NOAA measured tide gauge data shows that coastal sea level rise at Ca. locations varies between 3 to 12 inches per century and have remained at those levels during the long measurement periods during which actual measured data have been recorded with a sample of that measured data shown below for San Diego, La Jolla, Los Angeles and San Francisco.

New Paper: Widespread Collapse Of Ice Sheets ~5000 Years Ago Added 3-4 Meters To Rising Seas

by K. Richard, March 11, 2019 in NoTricksZone


During the Mid-Holocene, when CO2 concentrations were stable and low (270 ppm), Antarctica’s massive Ross Ice Shelf naturally collapsed, adding the meltwater equivalent of 3-4 meters to sea levels.

Because CO2 concentrations changed very modestly during the pre-industrial Holocene (approximately ~25 ppm in 10,000 years), climate models that are predicated on the assumption that CO2 concentration changes drive ocean temperatures, ice sheet melt, and sea level rise necessarily simulate a very stable Holocene climate.

In contrast, changes in ocean temperatures, ice sheet melt, and sea level rise rates were far more abrupt and variable during the Holocene than during the last 100 years.

Modern ocean changes are barely detectable in the context of natural variability

Image Source(s): Rosenthal et al., 2013Climate Audit

What’s Natural? Changing Sea Levels – Part 1

by Jim Steele, February 23, 2019 in WUWT


Local sea levels appear to rise when ocean volumes increase, but also when the land sinks. Scientists increasingly warn that coastal cities are sinking much faster than ocean volumes are rising. Pumping out groundwater not only causes lands to sink, it increases the oceans’ volume. China’s Huanghe Delta is sinking 10 inches a year. Southeast Asian cities battle sinking rates of 1.2 to 2.4 inches per year. Regions around Houston, Texas had sunk 10 feet by 1979; a disaster waiting to happen where hurricanes commonly generate 15-foot storm surges. Likewise, New Orleans was doomed by sinking 1.4 inches per year. Built on marshland, San Francisco’s airport sinks 0.4 inches per year.
In contrast, ocean warming plus added glacial meltwater are estimated to have only added 0.06 inches per year to sea level from 1850 to 1990, punctuated by decades that accelerated sea level rise to 0.14 inches a year. Still, that fastest rate of modern sea level rise remains only one-tenth of New Orleans’ sinking rate.

A global assessment of atoll island planform changes over the past decades

by E. Duvat, October 25, 2018 in WiresClimateChange


Over the past decades, atoll islands exhibited no widespread sign of physical destabilization in the face of sea‐level rise. A reanalysis of available data, which cover 30 Pacific and Indian Ocean atolls including 709 islands, reveals that no atoll lost land area and that 88.6% of islands were either stable or increased in area, while only 11.4% contracted. Atoll islands affected by rapid sea‐level rise did not show a distinct behavior compared to islands on other atolls. Island behavior correlated with island size, and no island larger than 10 ha decreased in size.

Study reconstructing ocean warming finds ocean circulation changes may account for significant portion of sea level rise

by Anthony Watts, January 7, 2019 in WUWT


Study suggests that in the last 60 years up to half the observed warming and associated sea level rise in low- and mid- latitudes of the Atlantic Ocean is due to changes in ocean circulation.

Over the past century, increased greenhouse gas emissions have given rise to an excess of energy in the Earth system. More than 90% of this excess energy has been absorbed by the ocean, leading to increased ocean temperatures and associated sea level rise, while moderating surface warming.

The multi-disciplinary team of scientists have published estimates in PNAS, that global warming of the oceans of 436 x 1021 Joules has occurred from 1871 to present (roughly 1000 times annual worldwide human primary energy consumption) and that comparable warming happened over the periods 1920-1945 and 1990-2015.

“Terrifying Sea-Level Prediction Now Looks Far Less Likely”… But “marine ice-cliff instability” is “just common sense”

by David Middleton, January 5, 2019 in WUWT


Marine ice cliff instability (MICI) “has not been observed, not at such a scale,” “might simply be a product of running a computer model of ice physics at a too-low resolution,” ignores post glacial rebound, couldn’t occur before ” until 2250 or 2300″… Yet “the idea is cinematic,” “it’s just common sense that Antarctic glaciers will develop problematic ice cliffs” and something we should plan for…

“Our results support growing evidence that calving glaciers are particularly sensitive to climate change.”  Greenland’s climate is always changing… Always has and always will change… And the climate changes observed over the last few decades are not unprecedented. The Greenland ice sheet is no more disappearing this year than it was last year and it is physically impossible for the ice sheet to “collapse” into the ocean.

Figure 6. Jakobshavn Isbrae. (Wikipedia and Google Earth)

Sea level oscillations in Japan and China since the start of the 20th century and consequences for coastal management – Part 1: Japan Author links open overlay panel

by Albert Parker, March 1, 2019 in Ocean&CoastalManagement


Highlights
• Japan has strong quasi-20 and quasi-60 years low frequencies sea level fluctuations.
• These periodicities translate in specific length requirements of tide gauge records.
• 1894/1906 to present, there is no sea level acceleration in the 5 long-term stations.
• Those not affected by crustal movement (4 of 5) do not even show a rising trend.
Proper consideration of the natural oscillations should inform coastal planning.

See also here

Land motion drives varying rates of sea level along the US East Coast

by Charles the moderator, December 26, 2018 in WUWT


From Science Magazine

Dec 20, 2018

Along the US East Coast, the Earth’s continued response to the end of the last ice age explains variances in relative sea level rates

Chestnut Hill, Mass. (12/20/2018) – Along the East Coast of the United States, relative sea level change does not happen uniformly between Maine and Florida.

Data have shown that sea level rise in the Mid-Atlantic region surpassed changes in relative sea level along the coastlines of the South Atlantic and the Gulf of Maine. A team of researchers took a look back at historical data through new analytical methods to pinpoint the reason behind the different rates of sea level change.

Assessing data from a range of sources and previous studies, the team concluded that the movement of the earth – referred to as vertical land motion – is the dominant force behind variations in rates of sea level rise up and down the East Coast, the team reports today in the journal Nature.