The theory of sea rise and the implications
for the Huia Domain
Guest post by Uncle Arthur aka Ken Walker
Huia Sea Level Rise – Update as at 31 October 2015
At the beginning of this year I was staggered to discover from the HuiaSOS Facebook page that the Waitakere Local Board had reneged on improving, perhaps even saving, the Huia seawall and the Huia domain amenities. The reason was not lack of money (they had nearly $1million budget allocated to this task two years in succession), but rather an ideological commitment to ‘managed retreat’.Despite being reasonably eco-aware, this was a new one on me. Nonetheless, a quick web-search confirmed that ‘managed retreat’ is apparently a bona fide response to the threat of sea-level rise for those who subscribe to the IPCC agenda.Time to dig a little deeper.
I have provided sources wherever possible in the following. Be warned that what is outlined here contradicts the NZ Parliamentary Commissioner for the Environment (http://www.pce.parliament.nz/), and by extension, the Auckland Council and the Government itself.
I urge you to check the references, follow your instincts, and make your own mind up about the reality of the THREAT of sea level rise.
Let’s start. Is the sea-level rising? There is a widely held belief that it has been rising between 1-2mm per year for the last hundred years. Such a rise can be entirely explained by thermal expansion following the most recent mini ice-age; that is, as the sea warms up it expands slightly (see https://en.wikipedia.org/wiki/Maunder_Minimum). Still, we need to check this, not because it is material (being 4-8 inches a century for pre-metric readers), but because we need to understand why they even think this. And ‘they’ in this case is just about everybody who counts world-wide, so at this point we don’t discount the fact that it could be true. The question is, how does anybody measure the sea level to one tenth of a millimeter/year, which is the level of precision claimed?
The mechanics of sea-level measurement are easily found on the web. A tube inserted into the sea with a float, which is attached to something solid. For instance, Marsden Wharf!
http://sealevel.colorado.edu/content/tide-gauge-sea-level
Frankly, I am skeptical of the claimed accuracy. However, even if 1/10th of a millimeter is accurate, how do we know the wharf is not sinking by that amount?
The answer is that we triangulate it from already established survey points. But how do we know that the whole land mass is not sinking, survey points included?
The answer is that we use satellites to measure the height of the land mass.
All good so far, but how does it stack up?
A reasonable guess for Marsden Wharf is that it weighs more than 10,000 tons. Plus it has continuous movement and additional weight on its surface every day. And it is sitting on piles that are sunk into Auckland’s soft rock substrate. Could it conceivably sink just 1mm/year?
Any survey triangulation should uncover this 1mm vertical change, however the following web references cast doubt on this. The most accurately located points in NZ only have an accuracy that approaches several centimeters.
http://www.linz.govt.nz/data/geodetic-services/positionz
These stations are the most accurately located points in New Zealand. They provide data that is used by surveyors to connect to the survey system, and they monitor the deformation of New Zealand. - See more at: http://www.linz.govt.nz/data/geodetic-services/positionz#sthash.lcdEDtcl.dpuf
The PositioNZ network enables users to position points with an accuracy that approaches a few centimetres relative to NZGD2000 both horizontally and vertically. - See more at: http://www.linz.govt.nz/data/geodetic-services/positionz#sthash.lcdEDtcl.dpuf
But regardless, is the entire North Island sinking – or rising? The North Island is part of the Australian Plate; the South Island is on the Pacific Plate. The Australian Plate is riding up on the Pacific Plate. The dividing line is down a line from Gisborne through Wellington.
Satellites should tell us the answer. But I have found no site that claims that GPS accuracy is better than 1 METER of height. Yet we are being told that it is confirming changes that are occurring down to 1/10,000th of a meter.
See http://www.gps.gov/systems/gps/performance/accuracy/
So where are these tide measurement sites?
Well we either have 4 on the east coast and none on the West, or we have many on both coasts. Choose your expert! Better still, some experts claim the North Island is rising, while others claim that it is sinking, both by 1-2mm/year.
The first experts, John Hannah and Robert Bell in 2012, on the location of sea-level measurements:
http://onlinelibrary.wiley.com/wol1/doi/10.1029/2011JC007591/full
[2] For the last 2 decades the assessment of relative sea level trends in New Zealand has been solely derived from the sea level records obtained from the four main port tide gauges of Auckland, Wellington, Lyttelton and Dunedin, where the only long-term (>70 year) data sets exist (Figure 1). These records go back to the start of the 20th century.
[26] Unfortunately, there is no long-term tide gauge data on the entire west coast of New Zealand that would allow an assessment of the possible impact of ENSO and IPO events on New Plymouth. However, the inferred trend at New Plymouth has been derived from an original datum definition that used 4 years of MSL data (1918–1921) and is calculated over an intervening time period of 84 years. The Mode 1 sea level anomaly at the nearest Wellington gauge (although more on the east coast) indicates sea level was slightly higher for that period (Table 3, Figure 4), so the inferred trend is likely to be reasonably robust, if not conservative. Interestingly, this is the only estimate of sea level rise that could be derived for the entire west coast of New Zealand, bordering the Tasman Sea.
[29] However, the situation at Wellington (cGPS data since 2000) and Nelson (cGPS data since 2003) is not so clear. The analyses of these cGPS data indicate the presence of small but ongoing subduction events (P. Denys, University of Otago, personal communication, 2011), further complicated by the likely presence of slow seismic events [e.g., Wallace and Beavan, 2010]. These cGPS data are currently the subject of more extended and ongoing analyses.
On the other hand there is Dr Willem de Lange, Earth Sciences Programme, Faculty of Science and Engineering, University of Waikato. Dr de Lange was an IPCC reviewer who wrote a scathing report about the IPCC science and its conclusions which is available here:
http://www.climaterealists.org.nz/node/150
In that report, Dr de Lange said:
I expected sea level rise to slow and reverse early in the 21st Century. The underlying long-term trend, however, was likely to decrease, and there were some tide gauge data to indicate that it had started to do so. In the 1980s, the New Zealand rate was 1.8 mm per year. By 1990, it was 1.7 mm per year, and by 2001 it was 1.6 mm per year.
This comment is echoed in a more recent NZCPR article, in which Vincent Gray stated that:
There is a tide gauge in Wellington harbour which has shown a fall in the sea level for the past ten years, and there are similar measurements all over New Zealand which provide no reason for imminent action.
In response to an email, Dr de Lange he had this to say about the sea-level tide gauges (neither Hannah nor Bell responded to a similar email):
Most tide gauges are operated by port companies and this is the case for the Manukau Harbour. However, some regional councils operate water level recorders at the coast, but I haven’t checked for the Auckland region. NIWA also operate some open coast tide gauges, and have one on the west coast near the Manukau.
My Question: Who certifies that they have not sunk?
The Port of Auckland gauges in the Waitemata were checked by LINZ and the Surveying School from the University of Otago. They don’t seem to have looked at the Manukau gauges. GeoNET also maintain continuous GPS sites
The LINZ website also provides data from the NIWA open coast tide gauge near the Manukau Harbour at http://www.linz.govt.nz/sea/tides/sea-level-data/sea-level-data-downloads
Does any of this matter? No.
These changes are trivial. The more important changes occur from crustal earth movements – aka earthquakes. Earthquakes occur frequently enough in NZ to be a significant factor in relative sea-level. For instance, the Christchurch earthquake raised some land by 2 meters, and 0.1meters at the tide gauge:
This from Hannah and Bell
[29] (Update: Outside this analysis period, the recent Christchurch earthquakes of 2010–2011 have caused an uplift of the Lyttelton tide gauge of about 0.10 m (P. Denys, University of Otago, personal communication, 2011).)
So, is the sea level threat anticipated by the Waitakere Local Board really anticipating a significant earthquake in Auckland? No mention of it. Besides, it could equally cause the sea level to fall by raising the land, as it did at Christchurch, undoing more than a century’s worth of sea level rise!
We are left with global warming and ice melt as the proximate threat that is agitating our elected representatives on the Local Board. Ultimately, the only way sea level can rise relative to land is if there is more of it – sea that is. And the only place more seawater can come from is land based ice (sea-ice can all melt without affecting sea level – the ice displaces the same water volume whether it is liquid or solid).
That means the Greenland ice cap (20%), or the Antarctic ice cap (80%) must be going to melt. This is big stuff, and by the way, if this happens, the last thing we’ll be worried about is the Huia Seawall.
MORE TO COME...