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The deception of rising sealevels

SUNDAY DECEMBER 07, 2014

One of the more mystifying claims in the global warmer/climate change debate is that of sea-levels rising. There is a huge variation amongst scientists, from Al Gore's figure of 65m per century, to NIWA's 1998 Lyttelton study of 1mm per year (10cm per century); a disparity of 65,000%. That degree of error disqualifies claims of plausibility, even throwing doubt on NIWA’s work. With that degree of uncertainty, it is difficult to see how anybody can be sure the sea is rising at all.

Just how, it may be asked, can 1mm change in sea-level be calculated, averaged over one entire year or a hundred years, when even a flat sea at rest undulates more than that with waves every few seconds, and tide height just in one day varies between high and low by some 2 metres.

To say a tide height is higher we require knowing higher than "what"?. To fairly compare tide heights, one needs a past reference height to compare with one in the present. Finding the former is not possible because ALL factors that influence tide height do not altogether repeat at one and the same time.

What are these factors? We are talking about the phase of the moon, lunar declination, perigee cycle, low and high air pressures that can suck surface heights up or depress them, and winds onshore that can blow water into a harbour, or offshore to deplete a bay. We are talking about closer-to-equinox tides that are higher than closer-to-solstice tides. We can remind ourselves that the sea is warmer in summer, therefore higher. Then we have underwater earthquakes, eruptions, and fissures, most non-recordable and/or undetectable, which raise local sea-levels by water expansion. It doesn't stop there.

Then there is rainfall at sea, river flows and land run-offs that contribute to sea-levels. Also, temperature changes control density and water volumes, ever-shifting in the ocean, and the direction of currents both deep, mid and surface, constantly alter sea height. Then there are cycles of glaciers’ advance and retreat that incrementally change heights of the ocean.

In short, we haven't a clue how high sea-levels are ever supposed to be in any fixed place, to a tolerance of 1mm per year, when everything connected to the sea is in constant flux. The sea is not a lake or a pond. No computer model can pretend that it is, just for the sake of a neat result, just to qualify for research funding.

Examinating old photographs, sketches and tide markers reveals high watermarks have remained unchanged on NZ beaches, apart from erosion due to changing currents. In February 1899 the public farewlled troops going to the Boer War. It was high tide when the ships left, so they could get safely out of the channel. The height of the high tide in this 115-year photograph, which appeared on the cover of the old Weekly News, can be seen against the wooden piles of the Auckland wharf. The average high tide height in Auckland is unchanged to this day.

 

My home is in West Auckland, within 2 minutes of a beach called French Bay, on the Manukau Harbour. I have been at this locality for over 40-years. The high water mark is the same now as it was well before I came to the neighborhood. Here is an archival photo of the same beach in the 1930s. The beach looks exactly the same today, with the same amount of foreshore, same distance of the road from the sea, and same highwater mark. The only difference is that what appears to be small shrubs are now mighty pohutakawas. 

If we cannot rely on old photos to prove our beaches have stayed the same, what can we rely on? These are not isolated cases of beaches unchanging. It would be very odd if the sea only raised its height at certain beaches and not others. What would be the selection process? If anyone needs more evidence for Auckland beaches, I spent the first five years of my life living near another, the beautiful and now very exclusive Takapuna Beach on Auckland's North Shore. Once again, the highwater mark there in the 1950s is identical to that of today.

Disappearing sand can be a function of lower tides that undermine foreshore, and top sand collapses. Without higher water to re-deposit sand higher up the shoreline, over time period a beach can ebb slowly away. Then higher tides deposit more sand because sand is heavier than water - surf brings sand in by momentum of wave action, and leaves it there when water recedes. It means that even if sea levels were rising, the water would not come over the land - the beach sand would simply get higher.

Erosion cycles are just that, cycles. Erosion on North Island east coast beaches like Ngunguru, Whitianga and Hawkes Bay will reverse as sand is replaced. If this was not cyclic, all sand on all beaches would have gone long before now.

Without monitoring over all oceans we cannot know if sea-levels are rising. We only have measuring devices on 0.4% on the earth's surface where humans live. Special buoys now report via satellite using Argos transmitters, but we need to wait several centuries to achieve a reliable average to comment on any future century's departure from average.

There is a finite amount of water on the planet. If it is not bound up in ice at the poles, it is in the sea. Antarctic and Arctic ice is thickening, which means sea-levels are now dropping, and in the southern hemisphere more so because ice on the eastern section of Antarctica, three quarters of that continent, is thickening at a faster rate. But not so in the west.

This is because under West Antarctica, thermal vents beneath the sea are currently active, melting ice on that quarter of the region. Thermal vents below the Alps are also causing some NZ glaciers to recede. Those are the glaciers that make the headlines, although in NZ advancing glaciers are more numerous.

On Tuvalu and other volcanic island atolls it is the land that is vertically moving, not the sea. Volcanic atolls are unstable - they go up and down like elevators. Small atolls like Tuvalu cannot be sliding under the sea whilst beaches in Australia and NZ stay unaffected. Again, how would the sea decide which countries to send beneath the waves?

As we emerge from this interglacial the poles have been the smallest in a while and some sea-levels are the highest they aspire to. Some countries are still rebounding after the last ice age– Scotland is rising and the south of England is lowering. The west of Australia is rising whilst the east is dropping. There is a similar differential between New Zealand's North and South island.

Let's get real and stop this scam of rising sealevels. Through daily surging wave action the high watermark on any beach varies up and down the sand by about a metre or so every 10 minutes. Small children run in and out of these surges, squealing with delight. NIWA's figure of sealevel rise is 1mm per year. So to that daily highwater mark of 1-2meters  let's add just 1 millimetre per year, the thickness of a grain of sand. If the thought of that tiny extra bit of water creeping up the beach over the course of a year is terrifying anyone, perhaps medical treatment might be advised.

For any queries please email ken@weatherman.co.nz


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