Originally posted on Jennifer Marohasy’s blog.
April 22, 2022 By jennifer
I live by the coast and love walking along the coast including climbing the ledges in Noosa National Park. All the way from Noosa to Sydney, you can find wave-cut platforms carved in the sandstone towards the bottoms of the cliff faces.
The sandstone is very old, thought to date back to the time of the dinosaurs, perhaps 180 million years ago, but the ledges – called platforms when they are wide – are much younger. Expert geologists suggest that my favorite very broad wave-cut platform, at the bottom of the cliff face that descends from the Boiling Pot Lookout, is about 125,000 years old.
It forms when sea levels are higher, and the shearing action of waves knocks large rocks down from above. Debris will be removed by washing, beyond the intertidal zone. The face of the cliff would have receded inland as the sea penetrated it. This is how cliffs are formed, and when they are sandstone, they sometimes leave ledges and wave-cut platforms as monuments, indicating that sea levels were higher in a bygone era.
For the past few years, I have stood on the wide platform at the bottom of the cliff, below the observatory, at the time of highest tide each year. Normally, the waves hit the rocks about a meter below, never reaching me. So, I confidently pick my nose at claims of unprecedented high sea levels as echoed on the nightly news and in IPCC reports. I also use it as an opportunity to agree with some geologists that sea levels were even higher 125,000 years ago, during the period known as the Eemian.
With the exception of this past January, the highest astronomical tides corresponded to a four-meter surge from the old storm Seth. That was the first year I didn’t stand on the platform at the height of the astronomical tide. But my dear friend Jared did. I made a short film about it all, called ‘Washed Away’.
Australia is a good place to study sea level change. Unlike Britain, Australia was not covered by an ice sheet during the last ice age. Ice sheets complicate things because when all the ice melts – as the Scottish iceberg did more than 9,000 years ago – part of the land mass can gradually recover dragging its bottom half. So the north of the British Isles is rising, while the south is sinking by 0.6 mm per year for the past 1,000 years – about 60 cm in total since the time of William the Conqueror. The sinking of this land is sometimes confused with sea level rise, and is thought to have occurred due to increased carbon dioxide emissions since the Industrial Revolution.
Where I live, about halfway down the east coast of Australia, sea levels started to rise about 16,000 years ago with the melting of Antarctica. About 9,000 years ago, sea levels around the world rose 12,000 centimeters, or 120 meters, equivalent to a 25-story building! The magnitude of this increase dwarfs the 36cm increase that has occurred over the past 150 years, and subsidence in places like Lincolnshire, by just a few centimeters over the same period, both prompting the Intergovernmental Panel on Climate Change (IPCC).
Indeed, it is indisputable, at least in peer-reviewed journals, that global sea level rise at the end of the last ice age occurred at a rate 10 times faster than the modern rate of about 3mm. per year – i.e. about how much compared to Scotland is increasing due to isostatic recovery.
After being buried under a few kilometers of ice, much of Europe and North America is undergoing recovery. For example, ice receded from Sweden between 9,900 and 10,300 years ago, and a large-scale increase is still taking place to the extent that tide gauges in Stockholm show sea levels have decreased by about 50 centimeters over the past 129 years – the average annual rate is a reduction of 3.9mm per year. The rise at Juneau, in Alaska, is even more dramatic: in just 80 years, sea levels have dropped 120cm at a steady rate of minus 15mm per year. This fact overlaps with the catastrophic sea level rise concept, so the IPCC ‘restricts’ the measurements from these tide gauges, until they show sea level rise.
These numbers aren’t easy to read and may seem extraordinary, but sea levels actually rose globally by 120 meters by the end of the last ice age. However, this inconvenient fact tends to be excluded from revised data-based climate change political summaries.
According to the IPCC’s latest report on climate change – Assessment Report 6, published just before the 26th Conference of the Parties (COP26) in Glasgow late last year – global temperatures are the warmest in history. at least the last 125,000 years. There’s no mention of it getting pretty cold in the middle and Scotland (where that meeting was held) was covered in a lot of ice.
Since Australia’s land area has not sunk or increased much during this time period, if the IPCC report is correct, the waves will cover my favorite 125,000-year-old platform at every high tide and I will be swept away.
The highest tides for this year are forecast for Monday, January 3 at 8:27 am. A water surge of four meters is also forecast because extratropical Seth exists just offshore. That morning, I hesitated. I didn’t get off the platform and was in danger of being swept away.
Instead, I positioned myself on a ledge and filmed Jared circling the platform to stay there at high tide.
There are rocky outcrops at three different heights in Noosa National Park – and along the coastline as far as Sydney. This is evidence carved in the rock that there were times in the past when sea levels were even higher than they are now. Why? Because the climate is always changing.
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This is a variation on an article first published in the UK edition on Audience January 22, 2022 magazine titled ‘Aussie Life’.
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