Bill – the Source article is a good read – and nice to see diverse opinions on the issue of Global Sea Level Rise (SLR) – and its regional outlay in terms of relative sea level rise (RSLR), in particular on sinking or subsiding coasts.
You and I and other learned colleagues interacted on this and related issues before in this forum. I will add some of my own findings and thoughts based on three essays: Sea level Rise – the Science; Sea level Rise – the Consequences and Adaptation; and Warming Climate and Entropy. In all these pieces, I have quoted National Academies Publications and 2021 IPCC Working Group findings – in particular with respect to their findings and predictions in terms of probability scale.
Perhaps – one can begin by seeing the Earth System – as consisting of three subsystems – the Fluid, the Solid and the Life. And it is helpful to see the issues in terms of Stress, e.g. . . . global warming is the stress with SLR as the consequence – in turn SLR is the stress with the consequences on human livelihood in the coastal zone . . .
Although we know all these, allow me to drift somewhat to the understandings of interactive and interdependent balancing processes. Earth's Fluidity, Solidity and the Life system evolved naturally in the past – until the beginning of industrial age. Beginning at this epoch, anthropogenic factors started accelerating the Earth-Sun energy balance – unbalancing the climate.
The significance and extent of RSLR – can best be understood from some quoted values. While SLR . . . has accelerated since the late 1960s, with an average rate of 2.3 [1.6 to 3.1] mm per yr over the period 1971–2018 increasing to 3.7 [3.2 to 4.2] mm per yr over the period 2006–2018 . . . the RSLR at the Mississippi River delta, the present SLR rates vary from +9 to +12 mm per year, far higher than the global average.
Apart from what are highlighted and discussed – in my judgment, the most crucial issue is how to address the SLR-RSLR consequential adverse effects on vulnerable coastal civil infrastructure in heavily built and urbanized areas. What mitigation and adaptation mean for these areas – in light, further of enhanced storm and wave activities – and reduction of gravity drainage hydraulic head.
And generally in terms of coastal erosion, saltwater intrusion and enhanced pore water pressure on coastal aquifers.
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Dr. Dilip K Barua, PhD
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